Manufacturing method of decorated natural leather

Abstract

A method of image recording on natural leather including the steps of: i) applying a base coat composition onto a surface of crusted leather, the base coat composition comprises water, a coloured pigment and a binder being a polyacrylate, a polyurethane, a polyamide or a polybutadiene, such as to form a base coat layer; and ii) applying a pre-treatment liquid onto at least a part of the base coat layer, the pre-treatment liquid comprising water, a fixing agent being a multivalent metal salt or a cationic polymer, a binder being a polyacrylate, a polyamide, a polyester, a polybutadiene or a polyurethane, such as to form a pre-treatment layer; and iii) inkjet printing an image onto the pre-treatment layer using an aqueous inkjet ink comprising a pigment and a water-soluble organic solvent. An image receiving natural leather substrate is also provided.

Description

PatXML 1 / 38 GX23014 Description Manufacturing method of decorated natural leather Technical Field

[0001] The present invention relates to methods for manufacturing decorated natural leather using inkjet printing technology. Background Art

[0002] Natural leather has been traditionally decorated by screen printing. However, screen printing is labour intensive as each colour requires an individual screen. This is costly and time consuming, especially when personalization is desired.

[0003] Digital printing technologies using UV curable inkjet ink have been disclosed for printing on natural leather as illustrated by WO2013 / 135828 A. UV curable inkjet inks have the advantage that they can also be printed on substantially non-absorbing substrates, such as natural leather that after tanning and crusting has been coated with a pigmented base coat layer.

[0004] In leather articles like shoes and wallets, the decorated natural leather must be able to endure a lot of flexing and abrasion without deterioration of the decoration. For accomplishing this, flexible UV curable inkjet inks are used that contain a high amount of monofunctional monomers. For example, in EP3833720A, the UV curable inkjet inks contain at least 85.0 wt.% of monofunctional polymerizable compounds based on the total weight of the polymerizable composition. Consequently, considerable amounts of residual uncured monofunctional monomer may be present in the decorated natural leather, thus posing a health and safety risk, especially for leather articles which frequently come into contact with the human skin such as handbags and wallets.

[0005] To overcome this potential drawback, it would be desirable to change from UV curable inkjet inks to aqueous inkjet inks. However, it has been observed that poor image quality is obtained especially when printing thePatXML 2 / 38 GX23014 aqueous inkjet inks on substantially non-absorbing substrates like crusted leather carrying a base coat as disclosed in EP3388491A.

[0006] JP2019077070A discloses an aqueous inkjet ink which is printed directly onto a leather with synthetic resin surface.

[0007] Fixing agents such as multivalent salts, cationic polymers or organic acids are used to be added to layers, often called pre-treatment layers or primers on poor or non-absorbing substrates in order to improve image quality. These fixing agents reduce the mobility of the pigments of the aqueous inkjet ink printed onto these pre-treatment layers and improve image quality such as reduced beading and bleeding.

[0008] WO2023001650A discloses a pre-treatment composition for inkjet printing, comprising water, a water-soluble multi-valent metallic salt, a wax, a non- ionic dispersant and a resin particle stabilized by a non-ionic group or non- ionic or amphiphilic compound to improve image quality. It is not clear if these pre-treatment compositions are fit for use with respect to flexibility and abrasion resistance for leather applications.

[0009] Base coats used onto crusted leather often contain coloured pigments to give the crusted leather surface onto which an image will be printed a black ground colour. The pigments in the base coat liquid, mostly dispersed with anionic dispersants, are however not compatible with the use of fixing agents in that composition, leading to storage stability issues of the base coat composition prior to being applied to the leather.

[0010] Therefor there is still a need for an image recording method onto coloured natural leather using aqueous inkjet ink technology and which combines an excellent image quality with a sufficient flexibility and durability. Summary of invention

[0011] It is the objective of the present invention to provide a solution to the above stated problems. The objective has been achieved by providing a method of recording an image including the steps of: - applying a base coat composition onto a surface of crusted leather, the base coat composition comprises water, a pigment and a binder selected from the group consisting of a polyacrylate, a polybutadiene, a polyurethane, a polyamide and a combination thereof, such as to form aPatXML 3 / 38 GX23014 base coat layer; and - applying a pre-treatment liquid onto at least a part of the base coat layer, the pre-treatment liquid comprising water, a fixing agent being a multivalent metal salt or a cationic polymer, a binder selected from the group consisting of a polyacrylate, a polyamide, a polyester, a polyurethane and a combination thereof, such as to form a pre-treatment layer; and - inkjet printing an image onto the pre-treatment layer using an aqueous inkjet ink comprising a pigment and a water-soluble organic solvent.

[0012] It is another embodiment of the invention to provide an image receiving natural leather substrate comprising: - crusted leather; and - a base coat layer onto a surface of the crusted leather, the base coat layer comprising a pigment and a binder selected from the group consisting of a polyacrylate, a polyurethane, a polyamide and combinations thereof; and - a pre-treatment layer onto at least a part of the base coat layer, the pre- treatment layer comprising a fixing agent being a multivalent metal salt or a cationic polymer and a binder selected from the group consisting of a polyacrylate, a polyurethane, a polyamide, a polyester and a combination thereof, such as to form a pre-treatment layer.

[0013] It is further an another embodiment of the invention to provide an ink set comprising a base coat composition comprising water, a pigment and a binder selected from the group consisting of a polyacrylate, a polyurethane, a polyamide and a combination thereof and a pre-treatment liquid onto at least a part of the base coat layer, the pre-treatment liquid comprising water, a fixing agent being a multivalent metal salt or a cationic polymer, a binder selected from the group consisting of a polyacrylate, a polyamide, a polyester, a polyurethane and a combination thereof, such as to form a pre-treatment layer.

[0014] Other features, elements, steps, characteristics and advantages of the present invention will become more apparent from the following detailedPatXML 4 / 38 GX23014 description of preferred embodiments of the present invention. Specific embodiments of the invention are also defined in the dependent claims. Description of embodiments A. Method of image recording on natural leather

[0015] The method of image recording on natural leather according to the invention includes the steps of: - applying a base coat composition onto a surface of crusted leather, the base coat composition comprises water, a pigment and a binder selected from the group consisting of a polyacrylate, a polyurethane, a polybutadiene, a polyamide, a polyester and a combination thereof, such as to form a base coat layer; and - applying a pre-treatment liquid onto at least a part of the base coat layer, the pre-treatment liquid comprising water, a fixing agent being a multivalent metal salt or a cationic polymer, a binder selected from the group consisting of a polyacrylate, a polyamide, a polyester, a polyurethane and a combination thereof, such as to form a pre-treatment layer; and - inkjet printing an image onto the pre-treatment layer using an aqueous inkjet ink comprising a pigment and a water-soluble organic solvent. A.1. Crusted leather

[0016] Crusted leather is obtained by tanning natural leather obtained from the animal skin or rawhide. In the tanning phase, the protein of the rawhide or skin is converted into a stable material that will not putrefy. Tanning serves further to give the hide mechanical resistance to humidity, temperature and chemical agents. It is technically a cross-linking process of collagen which is the main protein of connective tissue in animals. There are various tanning substances such as: chromium, tannins, aluminum, zirconium, aldehydes. Chrome is most frequently used as tanning agent whereby the tanned product obtains a pale blue colour, therefore commonly called “wet blue”.PatXML 5 / 38 GX23014

[0017] In a further phase of crusting, the tanned leather is dried and softened, by washing and neutralizing the hides to remove many remaining chemicals. Then the hides may be dyed to give them a desired color.

[0018] The tanning phase is followed by a re-tanning phase, wherein the leather is treated with filling substances, water-repellent substances and fatliquors which can be of an animal, vegetable or synthetic nature. The crusting often includes processes such as stripping (removal of superficially fixed tannins), fat liquoring (fats, oils and waxes are fixed to the leather fibres), dyeing, whitening, physical softening, and buffing (abrasion of leather surface to reduce grain defects). A.2. Application of a base coat onto crusted leather

[0019] In this step of the image recording method according to the invention, a base coat composition is applied onto the surface of the crusted leather to obtain a basecoat.

[0020] The basecoat composition is applied on a crusted leather for providing a level of quality commensurate to the luxury aspect of leather and for avoiding too much penetration into the leather of the low viscosity inkjet ink resulting in a reduced image quality.

[0021] The base coat composition comprises water, a pigment and a binder selected from the group consisting of a polyacrylate, a polyamide, a polyester, a polyurethane, a polybutadiene and combinations thereof. These polymers lead to base coats showing excellent flexibility to the printed leather. The base coat composition may further comprise a filler such as silica particles and the pigment can be a mix of pigments.

[0022] The basecoat preferably has a colour similar to that of the corium and the grain of the crusted leather. Consequently, the visual color density of the corium and grain is enhanced. Any desired colour may be chosen for the corium or grain and the basecoat, such as red, green, brown, black, blue..., but preferably the hue of the pigment in the base coat is equal or at least similar to the hue of the colored crusted leather. The corium and grain are usually dyed by dyes during the crusting phase.PatXML 6 / 38 GX23014

[0023] To have sufficient color fastness, pigments as colorants are preferred to be included in the basecoat. Consequently, these colour pigment reduce the fading of the leather colour under prolonged UV exposure, such as from the sun.

[0024] The pigments in the base coat composition need to be dispersed in the vehicle of the composition, the vehicle containing at least water.

[0025] The pigments in the base coat composition according to the invention may be black, white, cyan, magenta, yellow, red, orange, violet, blue, green, brown, mixtures thereof, and the like. A color pigment may be chosen from those disclosed by HERBST, Willy, et al. Industrial Organic Pigments, Production, Properties, Applications.3rd edition. Wiley - VCH, 2004. ISBN 3527305769.

[0026] The pigment particles are dispersed in an aqueous vehicle, preferably by using a polymeric dispersant, a surfactant, a combination thereof or they can be self-dispersible pigments. The latter prevents interaction of the polymeric dispersant with the dispersing groups of resin particles.

[0027] Useful polymeric dispersants and surfactants do preferably include an anionic charge to assure electrostatic stabilization of the dispersed pigment particles in the aqueous vehicle.

[0028] Suitable commercially available pigment dispersions for use in the base coat composition of the invention are RODA® Lite range, RODA® Car range and Aquadem® X range from TFL. The amount of the pigment in suitable pigment dispersions is preferably not less than 5 wt.% to not more than 25 wt.%, more preferably not less than 10 wt.% to not more than 20 wt.%. If the pigment amount in the pigment dispersions is below these ranges, to much water is included in the base coat formulation leading to longer dry times. If the pigment amount in the pigment dispersions is above these ranges, sedimentation and inhomogeneous application of the pigment in the base coat may occur.

[0029] Suitable polyurethanes include RODA® PUR range, Aquaderm® Bottom range, and Bayderm® Bottom range, from TFL, UrepalTM PU147 and PU181 from CHEMIPAL S.p.A.; Rhoda Base Wh0303, Rhoda® Pur 64 / N from TFL ; MelioTM Promul 61 from STAHL; AstacinTM Finish PS fromPatXML 7 / 38 GX23014 BASF; EcrothanTM 4075, 4078 and 4084 from MICHELMAN; IncorezTM CS8073 and CS065-195 from INCOREZ. The dry weight of the polyurethane in the basecoat is preferably in the range of 3 to 60 g / m².

[0030] Although polyurethanes are preferred as the polymers for the basecoat composition, other polymers may be used in combination with the polyurethanes. Such polymers preferably have an elongation at break of more than 200%, more preferably 300%. The elongation at break is measured according to ISO527-2, for example, with a MTS ExceedTM testing apparatus from MTS Systems Corporation.

[0031] Suitable polyamides include the PA emulsion types ED310 and 161148 CX from MICHELMAN. The dry weight of the polyamide in the basecoat is preferably less than 7 g / m², more preferably less than 5 g / m².

[0032] Another type of preferred polymers to be used in the basecoat composition are polyacrylates. Polyacrylates provide good flexibility and stabilize pigment dispersions in the basecoat.

[0033] In a preferred embodiment, the basecoat composition preferably includes a polymer or copolymer based on polyurethane and polymer or copolymer based on a polyacrylate. Such a combination brings excellent flexibility even in the presence of pigments.

[0034] Preferred polyacrylates are RODA® Base range, RODA® Cryl range, Primal®range and Euderm®range from TFL. A suitable polymeric acrylate emulsion is BioflexTM KGA from LMF Biokimica.

[0035] A cross-linker may be incorporated in the basecoat layer to improve the strength and the adhesion to crust leather. Preferred cross-linkers include isocyanate based cross-linkers, aziridine based crosslinkers, aldehyde based cross-linkers such as formaldehyde, melamine formaldehyde derivatives, urea formaldehyde resins, glyoxal and glutaraldehyde, epoxides, oxazolidines and carbodiimides. Isocyanate and carbodiimides being particularly preferred.

[0036] Suitable commercial carbodiimides are Roda® Link 5777 from TFL and Carbodilite series manufactured by Nisshinbo Chemical, suitable commercial isocyanate cross-linkers are the Aquaderm®XL range from TFL.PatXML 8 / 38 GX23014

[0037] The basecoat composition may be applied as a single layer or may be applied as multiple layers. Multiple layers are useful if the required amount of binders and pigments to be laid down on the surface of the crusted leather is high, the required amount can be split over multiple base coat layers. The multiple layers may even have a different composition for improving properties like adhesion or flexibility.

[0038] The dry weight of the base coat layer is preferably equal to 3 g / m² or more and 60 g / m² or less. If the dry weight is below this amount, insufficient color density of the non-printed image part is obtained. Dry weights above this range are not suitable to be applied via spraying requiring complex coating equipment.

[0039] The dry weight of the cross-linker in the basecoat layer is preferably less than 3 g / m², more preferably less than 2 g / m². If the dry weight of the cross-linker is above these values, penetration of the ink is decreased impairing the image quality due to increased bleeding and coalescence.

[0040] The basecoat composition is preferably applied by spraying, but may be applied by any coating technique known, such as reverse or synchro roller coating knife coating, extrusion coating, slide hopper coating, curtain coating, transfer coating, flexographic or printing and jetting techniques such as ink jetting or valve-jetting.

[0041] As decorated leather articles are used in harsh conditions, it can be advantageous to apply an adhesion liquid onto the crusted leather surface before applying the base coat composition. This adhesion liquid which comprises a binder and a solvent increases the adhesion of the base coat to the surface of the crusted leather.

[0042] The binder in this adhesion liquid is preferably a polyurethane or a polyacrylate. Suitable commercially available polyurethanes are polyether urethanes such as RODA® Pur range , RODA® Cryl range, Aquaderm® range and Euderm® range from TFL.

[0043] The dry weight of the applied adhesion layer is equal to 1 g / m² or more and 20 g / m² or less. If the dry weight is below this amount, insufficient adhesion of the base coat and image to the crusted leather is obtained.PatXML 9 / 38 GX23014 Dry weights above this range are not suitable to be applied via spraying requiring multiple layers or complex coating equipment.

[0044] After the application of the base coat composition and optionally the adhesion liquid onto the surface of the crusted leather, the layers are preferably dried before applying the next, using heat and or an air flow. Optionally, the layers can be fixed by means of a thermal treatment in combination with pressure, such as by means of heated plates. A.3. Application of a pre-treatment liquid onto the base coat layer

[0045] After or during the application of the base coat, a pre-treatment liquid is applied onto at least a part of the base coat layer such as to form a pre- treatment layer. The pre-treatment layer reduces the mobility of the colorants of the inkjet inks which will be printed thereupon. Reduced mobility improves image quality of the inkjet printed image as it decreases ink bleed, ink coalescence and improves sharpness.

[0046] The pre-treatment liquid comprises water, a fixing agent, a binder selected from the group consisting of a polyacrylate, a polyurethane, a polyether urethane, a polyamide, a polyester and combinations thereof.

[0047] The fixing agent present in the pre-treatment composition is a multivalent metal salt or a cationic polymer.

[0048] The multivalent metal salt may be present in the pre-treatment composition to improve inkjet print quality. Generally, the multivalent metal salt may be any water-soluble multivalent metal salt. In specific examples, the multivalent metal salt may include calcium chloride (CaCI2), magnesium chloride (MgCI2), magnesium sulfate (MgSO4), aluminium chloride (AICI3), calcium nitrate (Ca(NO3)2), magnesium nitrate (Mg(NO3)2), magnesium acetate (Mg(CH3COO)2), zinc acetate (Zn(CH3COO)2) calcium propionate (Ca(C2H5COO)2), or a combination thereof. In a particular example, the multivalent metal salt may be Magnesium nitrate. In further examples, the multivalent metal salt may include a metal cation selected from calcium, copper, nickel, magnesium, zinc, barium, iron, aluminium, chromium, or another multivalent metal.PatXML 10 / 38 GX23014

[0049] The multivalent metal salt may also include an anion. In some examples, the anion may be fluoride, chloride, iodide, bromide, nitrate, chlorate, sulfate, acetate, or RCOO- where R is hydrogen or any low molecular weight hydrocarbon chain, e.g., C1 to C12. The cationic salt may also be a mixture of two or more different cationic salts.

[0050] In some cases, the multivalent metal salt may be present in an amount from 1 wt. % to 99 wt. % with respect to the entire weight of the solids of the pre-treatment liquid. In more specific examples, the multivalent metal salt may be present in an amount from 5 wt. % to 65 wt. %, more preferably from 25 wt. % to 60 wt. %, with respect to solids content of the pre-treatment composition. If the amounts are below the lower limits, insufficient fixing of the colorants occur resulting in a reduced image quality.

[0051] Cationic polymers, suitable as fixing agent in the pre-treatment composition contain either guanidinium or fully quaternized ammonium functionalities, such as quaternized polyamine copolymers. Generally, the weight average molecular weight (Mw) of the cationic polymer allows a viscosity less than 25 cP at 25°C, as measured on a Brookfield viscometer. Typical Mw are less than 500.000 g / mol, and in one aspect, less than 50.000 g / mol.

[0052] Suitable classes of cationic polymers that can be used include, but are not limited to, quaternized polyamines, dicyandiamide polycations, diallyldimethyl ammonium chloride copolymers, quaternized dimethylaminoethyl(meth)acrylate polymers, quaternized vinylimidizol polymers, alkyl guanidine polymers, alkoxylated polyethylene imines, and mixtures thereof.

[0053] The dry weight of the pre-treatment layer is preferably from 1 g / m² to 20 g / m², more preferably 1 g / m² to 10 g / m², most preferably 1 g / m² to 5 g / m². If the dry weight is lower than this range, the image quality of the printed image (ink spreading / mottle and coalescence) is insufficient. If the dry weight is higher than this range, the application via spraying requires multiple layers or complex coating equipment.PatXML 11 / 38 GX23014

[0054] The pre-treatment liquid according to the invention comprises water as a vehicle. The aqueous vehicle may include one or more water-soluble organic solvents.

[0055] The one or more organic solvents may be added for a variety of reasons. For example, it can be advantageous to add a small amount of an organic solvent to improve the dissolution of a compound in the pre-treatment liquid to be prepared, to obtain better penetration in porous substrates or to prevent fast drying of the pre-treatment liquid at the nozzle of inkjet heads if the pre-treatment liquid is jetted. Preferable water-soluble organic solvents are polyols (e.g., ethylene glycol, glycerin, 2-ethyl-2- (hydroxymethyl)-1 ,3-propanediol, tetraethylene glycol, triethylene glycol, tripropylene glycol, 1,2,4-butanetriol, diethylene glycol, propylene glycol, dipropylene glycol, butyleneglycol, 1 ,6-hexanediol, 1 ,2-hexanediol, 1 ,5- pentanediol, 1,2-pentanediol, 2,2-dimethyl-1 ,3-prapanediol, 2-methyl-2,4- pentanediol, 3-methyl-1 ,5-pentanediol, 3-methyl-1 ,3-butanediol, and 2- methyl-1 ,3-propanediol), N-hydroxyethyl-pyrrolidon, N-butyl-pyrrolidon, amines (e.g., ethanolamine, and 2-(dimethylamino)ethanol), monohydric alcohols (e.g., methanol, ethanol, and butanol), alkyl ethers of polyhydric alcohols (e.g., diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, and dipropylene glycol monomethyl ether), 2,2'- thiodiethanol, amides such as N,N-dimethylformamide, heterocycles such as 2-pyrrolidone and N-methyl-2-pyrrolidone, and acetonitrile. The organic solvents are preferably added to the pre-treatment liquid formulation in a total amount of 0.1 to 25 wt.% based on the total weight of the liquid.

[0056] All well-known conventional methods can be used for applying the pre- treatment liquid on the base coat. Examples of the method include air knife coating, blade coating, roll coating, gravure coating, jetting and spraying. More preferably the pre-treatment liquid is applied by means of a spraying technique. The advantage of a spray technique for applying the pre- treatment composition according to the invention is linked to the versatilityPatXML 12 / 38 GX23014 of the technology which allows the layer to be applied on any type of surface, from smooth to embossed surfaces, in a very homogeneous way.

[0057] After applying the pre-treatment liquid onto the base coat, the pretreatment layer is preferably at least partially dried before printing the image. Suitable drying techniques may include heat, air flow and heated pressure plates.

[0058] The base-coated leather to which the pre-treatment liquid has been applied may be dried and optionally undergo a heat treatment, before the subsequent ink jetting step with the pigment containing ink. Examples of the heating process include, but are not limited to, ventilated oven, heat press, atmospheric steaming, high-pressure steaming, and THERMOFIX. Any heat source can be used for the heating process; for example, an infrared ray lamp can be employed.

[0059] In another preferred embodiment of the invention, the pre-treatment liquid is not substantially dried before the image is printed by means of the jetting of the aqueous ink jetting step. A.4. Inkjet printing an image onto the pre-treatment layer

[0060] After applying the pre-treatment liquid and at least partially drying the pre- treatment layer an aqueous pigment ink composition is applied onto the pretreatment liquid or pretreatment layer.

[0061] A preferred method of applying the aqueous inkjet ink is by means of an ink jetting technique.

[0062] A preferred ink jet head for the jetting of the aqueous inkjet ink printing system is a piezoelectric ink jet head. Piezoelectric inkjet jetting is based on the movement of a piezoelectric ceramic transducer when a voltage is applied thereto. The application of a voltage changes the shape of the piezoelectric ceramic transducer in the print head creating a void, which is then filled with aqueous inkjet ink. When the voltage is removed, the ceramic expands to its original shape, ejecting a drop of aqueous inkjet ink from the ink-jet head. However, the jetting of the aqueous inkjet ink according to the present invention is not restricted to piezoelectric inkjet printing. Other inkjet print heads can be used and include various types,PatXML 13 / 38 GX23014 such as a continuous type, a thermal print head type, a Memjet-type of head and a valve jet type.

[0063] The inkjet head can be a fixed array of nozzles oriented transversally to the conveying direction, preferable over the width of the leather or can be incorporated in a scanning equipment which moves the inkjet head in a direction transversally to the conveying direction.

[0064] Specifically, for reliable jetting of metal oxide based white inks, the inkjet printing system includes preferably shaking, mixing or stirring equipment. This equipment is to re-disperse the white inkjet ink which may have settled in between print jobs. In some examples, the printing system may be configured to shake the cartridge, ink tank or ink buffer tank including the white inkjet ink. In other examples, the print cartridge or ink tank may be configured to mix or stir the white inkjet prior to printing.

[0065] In a preferred embodiment, the printing system may be configured to recirculate the aqueous ink prior to printing. A particularly useful inkjet head to print the aqueous inkjet inks of the invention, is from the type that includes a recirculation of the ink within the head such as through-flow heads as disclosed in WO 2006 / 030235 A2 and WO 2006 / 064036 A1.

[0066] This type of inkjet head is very suitable to be incorporated in a printing system comprising a through-flow print head having one or more nozzles for ejecting drops of aqueous ink onto a pre-treatment layer, and an ink circulation system for feeding and circulating the ink through the print head, comprising an ink tank for containing the ink, a supply buffer tank for receiving the ink from the main tank and supplying the ink to the through- flow print head, a return manifold for receiving the ink from the through- flow print head and returning ink to the main ink tank via a pump.

[0067] After having applied the aqueous inkjet ink onto the layer of the pre- treatment liquid such that an image is formed, the image is dried.

[0068] The drying step of the image can be performed by applying an air flow and or apply heating. The heating step must be performed by using heat sources; examples include equipment for forced-air heating, radiation heating such as IR-radiation, including NIR-, CIR- and SWIR radiation, conduction heating, high-frequency drying, and microwave drying.PatXML 14 / 38 GX23014 Examples of the heating process include, but are not limited to, heat press, atmospheric steaming, high-pressure steaming, and THERMOFIX.

[0069] When inkjet printing an image onto the pre-treatment layer according to the invention, an inkjet ink comprising water, a pigment and a water- soluble organic solvent is used.

[0070] In a preferred embodiment of the invention, the aqueous inkjet ink also comprises a resin and or a wax. As such, the wax may be polyethylene waxes, petroleum waxes, paraffin waxes, carnauba waxes, polypropylene waxes, crystalline and microcrystalline waxes, amide waxes (oleamide, stearamide, erucamide, cyclic amide, etc…), and combinations thereof. In an aspect of the invention, the wax may be a high-density polyethylene wax.

[0071] In an aspect of the invention, the wax may be a polyethylene wax or modified paraffin wax. An example of modified paraffin wax particles includes paraffin wax that has been modified to improve dispersability in water, e.g., via emulsification. The modified paraffin wax may be surface modified, chemically modified, etc.

[0072] Some specific examples of wax that may be used include those of the JONCRYL Wax series (such as JONCRYL Wax 22, JONCRYL Wax 26, and JONCRYL Wax 120 available from BASF Corp.), those of the AQUACER series (such as AQUACER 498, AQUACER 501, AQUACER 505, AQUACER 513, AQUACER 530, AQUACER 531, AQUACER 535, AQUACER 537, AQUACER 539, and AQUACER 552 available from BYK- Gardner, Columbia, Md. ) and Liquilube 404E from Lubrizol .

[0073] The wax may have i) a high melting temperature T and / or ii) a small average particle size. In an example, the wax may have a high melting T such as one that is equal to or greater than 90°C. Further, the wax may have an average particle size (in terms of effective diameter assuming that the individual wax particles are not perfectly spherical) ranging from 0.03 µm to 1.5 µm, more preferably from 0.05 µm to 1 µm(D50). If the particle size exceeds these upper limits, jetting reliability problems of the varnish are likely to occur.PatXML 15 / 38 GX23014

[0074] The wax may be present in the reaction liquid in an amount ranging from 0.1 to 10 wt. %, more preferably from 0.3 to 5 wt. %, relative to the total weight of the reaction liquid.

[0075] The aqueous inkjet ink may further comprise a surfactant, a humectant, a biocide, an anti-foam additive, an anti-corrosion additive and a thickener additive. Pigment

[0076] The pigments in the aqueous inkjet ink according to the invention may be black, white, cyan, magenta, yellow, red, orange, violet, blue, green, brown, mixtures thereof, and the like. A colour pigment may be chosen from those disclosed by HERBST, Willy, et al. Industrial Organic Pigments, Production, Properties, Applications.3rd edition. Wiley - VCH, 2004. ISBN 3527305769.

[0077] Suitable pigments are disclosed in paragraphs

[0128] to

[0138] of WO 2008 / 074548.

[0078] The pigment particles are dispersed in an aqueous vehicle, preferably by using a polymeric dispersant, a surfactant, a combination thereof or they can be self-dispersible pigments. The latter prevents interaction of the polymeric dispersant with the dispersing groups of resin particles or capsules which may be included in the inkjet ink (see below).

[0079] A self-dispersible pigment is a pigment having on its surface covalently bonded anionic hydrophilic groups or salt-forming groups, that allow the pigment to be dispersed in an aqueous medium without using a surfactant or a resin.

[0080] The technology for making self-dispersible pigments is well-known. For example, EP1220879A discloses pigments having attached a) at least one steric group and b) at least one organic ionic group and at least one amphiphilic counterion, wherein the amphiphilic counterion has a charge opposite to that of the organic ionic group that are suitable for inkjet inks. Also, EP906371A discloses suitable surface-modified coloured pigment having attached hydrophilic organic groups containing one or more ionic groups or ionizable groups. Suitable commercially available self-PatXML 16 / 38 GX23014 dispersible colour pigments are, for example, the CAB-O-JETTMinkjet colorants from CABOT.

[0081] Pigment particles in inkjet inks should be sufficiently small to permit free flow of the ink through the inkjet-printing device, especially at the ejecting nozzles. It is also desirable to use small particles for maximum colour strength and to slow down sedimentation.

[0082] The average pigment particle size is preferably between 0.050 and 1 μm, more preferably between 0.070 and 0.300 μm and particularly preferably between 0.080 and 0.200 μm. Most preferably, the numeric average pigment particle size is no larger than 0.150 μm. The average particle size of pigment particles is determined with a Brookhaven Instruments Particle Sizer BI90plus based upon the principle of dynamic light scattering.

[0083] Suitable white pigments are given by Table 2 in

[0116] of WO 2008 / 074548. The white pigment is preferably a pigment with a refractive index greater than 1.60. The white pigments may be employed singly or in combination. Preferably titanium dioxide is used as pigment with a refractive index greater than 1.60. Suitable titanium dioxide pigments are those disclosed in

[0117] and in

[0118] of WO 2008 / 074548.

[0084] Also, special colorants may be used, such as metallic pigments for printing a luxury look of silver and gold colours on leather.

[0085] Suitable polymeric dispersants are copolymers of two monomers but they may contain three, four, five or even more monomers. The properties of polymeric dispersants depend on both the nature of the monomers and their distribution in the polymer. Co-polymeric dispersants preferably have the following polymer compositions: ^ statistically polymerized monomers (e.g. monomers A and B polymerized into ABBAABAB); ^ alternating polymerized monomers (e.g. monomers A and B polymerized into ABABABAB); ^ gradient (tapered) polymerized monomers (e.g. monomers A and B polymerized into AAABAABBABBB); ^ block copolymers (e.g. monomers A and B polymerized into AAAAABBBBBB) wherein the block length of each of the blocks (2,PatXML 17 / 38 GX23014 3, 4, 5 or even more) is important for the dispersion capability of the polymeric dispersant; ^ graft copolymers (graft copolymers consist of a polymeric backbone with polymeric side chains attached to the backbone); and ^ mixed forms of these polymers, e.g. blocky gradient copolymers.

[0086] Suitable dispersants are DISPERBYKTMdispersants available from BYK CHEMIE, JONCRYLTMdispersants available from BASF and SOLSPERSETMdispersants available from Lubrizol. A detailed list of non- polymeric as well as some polymeric dispersants is disclosed by MC CUTCHEON. Functional Materials, North American Edition. Glen Rock,N.J.: Manufacturing Confectioner Publishing Co., 1990. p.110-129.

[0087] The polymeric dispersant has preferably a number average molecular weight Mn between 500 and 30000, more preferably between 1500 and 10000.

[0088] The polymeric dispersant has preferably a weight average molecular weight Mw smaller than 100,000, more preferably smaller than 50,000 and most preferably smaller than 30,000.

[0089] The pigments are preferably present in the range of 0.01 to 15 %, more preferably in the range of 0.05 to 10 % by weight and most preferably in the range of 0.1 to 5 % by weight, each based on the total weight of the inkjet ink. For white inkjet inks, the white pigment is preferably present in an amount of 3% to 40% by weight of the inkjet ink, and more preferably 5% to 35%. An amount of less than 3% by weight cannot achieve sufficient covering power.

[0090] In a preferred embodiment of the invention the aqueous ink comprises a pigment which is encapsulated by means of a cross-linked polymeric shell. Encapsulated pigments provide higher stability certainly in formulations in which pigment dispersions and resin dispersions are mixed.

[0091] Suitable encapsulated pigments are provided by Lubrizol as Diamond HSDX-dispersions and by Fujifilm as RxD pigment dispersions such as APD1000 and APD400 premium dispersions. VehiclePatXML 18 / 38 GX23014

[0092] The aqueous ink according to the invention comprises water as a vehicle. The aqueous vehicle may further include one or more water-soluble organic solvents.

[0093] The one or more organic solvents may be added for a variety of reasons. For example, it can be advantageous to add a small amount of an organic solvent to improve the dissolution of a compound in the ink composition to be prepared or to prevent fast drying of the ink at the nozzle of the inkjet head. Preferable water-soluble organic solvents are polyols (e.g., ethylene glycol, glycerin, 2-ethyl-2-(hydroxymethyl)-1,3-propanediol, tetraethylene glycol, triethylene glycol, tripropylene glycol, 1,2,4-butanetriol, diethylene glycol, propylene glycol, dipropylene glycol, butyleneglycol, 1,6- hexanediol, 1,2-hexanediol, 1,5-pentanediol, 1,2-propane diol, 1,3- propane diol, 1,2-pentanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-2,4- pentanediol, 3-methyl-1,5-pentanediol, 3-methyl-1,3-butanediol, and 2- methyl-1,3-propanediol), N-hydroxyethyl-pyrrolidon, N-butyl-pyrrolidon, amines (e.g., ethanolamine, and 2-(dimethylamino)ethanol), monohydric alcohols (e.g., methanol, ethanol, and n-butanol), alkyl ethers of polyhydric alcohols (e.g., diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, and dipropylene glycol monomethyl ether), 2,2'- thiodiethanol, amides such as N,N-dimethylformamide, heterocycles such as 2-pyrrolidone and N-methyl-2-pyrrolidone, and acetonitrile.

[0094] Preferably, if two or more organic solvents are present in the ink, one of the organic solvents has a boiling point of 150°C or more and 250°C or less. If the boiling point is below this range, the solvent is very volatile and may give an unwanted odour to the ink. When the boiling point of the solvent is above the mentioned range, the solvents have the tendency of not being eliminated in the drying step and remain in the printed image leading to a reduced resistance to rubbing and scratching of the printed image. This water-soluble organic solvent is preferably added to the ink composition formulation in an amount of 0.1 to 55 wt.% based on the totalPatXML 19 / 38 GX23014 weight of the ink. Resin

[0095] The ink jet ink composition according to the invention may comprise resin particles. The resin is often added to the ink jet ink formulation to achieve a good adhesion of the pigment to the layers on the substrate. The resin is preferably a polymer and suitable resins can be an acrylic based resin or a urethane resin.

[0096] The polyurethane resin is preferably to be incorporated in the ink formulation as a dispersion and may be selected from the group consisting of aliphatic polyurethane dispersions, aromatic polyurethane dispersions, anionic polyurethane dispersions, non-ionic polyurethane dispersions, aliphatic polyester polyurethane dispersions, aliphatic polycarbonate polyurethane dispersions, aliphatic acrylic modified polyurethane dispersions, aromatic polyester polyurethane dispersions, aromatic polycarbonate polyurethane dispersions, aromatic acrylic modified polyurethane dispersions, for example, or a combination of two or more of the above.

[0097] A preferred urethane resin to be used as dispersion in the ink of the invention is a polyester resin including a structural unit containing a urethane bond. Among such resins, a water-soluble or water-dispersible urethane-modified polyester resin is preferred. It is preferable that the urethane-modified polyester resin include at least one structural unit derived from a hydroxyl group-containing polyester resin (polyester polyol) and at least one structural unit derived from an organic polyisocyanate.

[0098] A preferred polyurethane resin to be included in the ink of the invention is a polyurethane resin obtainable by reacting a polyester polyol, a polyether diol, a polyol containing an anionic group and a polyisocyanate. Examples of suitable polyurethane resins and their preparations are disclosed in the unpublished patent application EP16196224.6.

[0099] Some examples of suitable polyurethane dispersions are NEOREZ R-989, NEOREZ R-2005, and NEOREZ R-4000 (DSM NeoResins); BAYHYDROL UH 2606, BAYHYDROL UH XP 2719, BAYHYDROL UH XP 2648, andPatXML 20 / 38 GX23014 BAYHYDROL UA XP 2631 (Bayer Material Science); DAOTAN VTW 1262 / 35WA, DAOTAN VTW 1265 / 36WA, DAOTAN VTW 1267 / 36WA, DAOTAN VTW 6421 / 42WA, DAOTAN VTW 6462 / 36WA (Cytec Engineered Materials Inc., Anaheim CA); and SANCURE 2715, SANCURE 20041, SANCURE 2725 (Lubrizol Corporation), for example, or a combination of two or more of the above.

[0100] Acrylic based resins include polymers of acrylic monomers, polymers of methacrylic monomers, and copolymers of the aforementioned monomers with other monomers. These resins are present as a suspension of particles having an average diameter of about 30 nm to about 300 nm. The acrylic latex polymer is formed from acrylic monomers or methacrylic monomers. Examples of monomers of the acrylic latex polymer include, by way of illustration, acrylic monomers, such as, for example, acrylate esters, acrylamides, and acrylic acids, and methacrylic monomers, such as, for example, methacrylate esters, methacrylamides, and methacrylic acids. The acrylic latex polymer may be a homopolymer or copolymer of an acrylic monomer and another monomer such as, for example, a vinyl aromatic monomer including, but not limited to, styrene, styrene butadiene, p-chloromethylstyrene, divinyl benzene, vinyl naphthalene and divinylnaphthalene.

[0101] Some examples of suitable acrylic latex polymer suspensions are, JONCRYL 537 and JONCRYL 538 (BASF Corporation, Port ArthurTX); CARBOSET GA-2111, CARBOSET CR-728, CARBOSET CR-785, CARBOSET CR-761, CARBOSET CR-763, CARBOSET CR-765, CARBOSET CR-715, and CARBOSET GA-4028 (Lubrizol Corporation); NEOCRYL A-1110, NEOCRYL A-1131, NEOCRYL A-2091, NEOCRYL A- 1127, NEOCRYL XK-96, and NEOCRYL XK-14 (DSM); and BAYHYDROL AH XP 2754, BAYHYDROL AH XP 2741, BAYHYDROL A 2427, and BAYHYDROL A2651 (Bayer), for example, or a combination of two or more of the above.

[0102] The ink jet ink composition according to the invention may comprise a capsule. Capsules, more preferably, nanocapsules are often incorporated in ink jet ink formulations to encapsulate colouring agentsPatXML 21 / 38 GX23014 (US2009227711A, JP2004075759) or to encapsulate reactive ingredients which can cross-link. Particularly useful are the nanocapsules disclosed in WO2015158649 [0037-0110]: The nanocapsules have a polymeric shell surrounding a core containing reactive chemistry. The shell material includes polyureas, polyurethanes, polyesters, polycarbonates, polyamides, melamine-based polymers and mixtures thereof, with polyureas and polyurethanes being especially preferred.

[0103] Other particularly useful nanocapsules are disclosed in WO2016165970 [0051-0138]: the nanocapsules include a dispersing group covalently coupled to the shell polymers. The core of the nanocapsules in WO2015158649 [0037-0110] and WO2016165970 [0051-0138] comprise reactive chemistry which is able to form a reaction product upon application of heat and / or light, allowing a wide variety of substrates to be addressed. Other suitable reactive chemistry is the one which is activated upon radiation as described in WO2015158649 [0068-0110].

[0104] The resins are preferably present in the inkjet ink in an amount of no more than 30 wt.%, preferably between 0.3 and 25 wt.% based on the total weight of the ink. Additives

[0105] The ink composition may contain a surfactant. Any known surfactant may be used but preferably an acetylene glycol surfactant and / or an acetylene alcohol surfactant and / or a polysiloxane surfactant is to be used. The use of the acetylene glycol surfactant and / or the acetylene alcohol surfactant and / or the polysiloxane surfactant improves the drying property in printing to allow high-speed printing.

[0106] The acetylene glycol surfactant and / or the acetylene alcohol surfactant is preferably one or more selected from 2, 4, 7, 9-tetramethyl-5-decine-4, 7- diol, alkylene oxide adducts of 2,4,7,9-tetramethyl-5-decine-4, 7-diol, 2,4- dimethyl-5-decin-4-ol, and alkylene oxide adducts of 2,4-dimethyl-5-decin- 4-ol. These are available from Nissin Chemical Industry, for example, as Olfine (registered trademark) E series, such as Olfine E1010, or fromPatXML 22 / 38 GX23014 Evonik (formerly Air Products (GB)) as Surfynol (registered trademark), 104, Surfynol 465 and Surfynol 61.

[0107] A biocide may be added to the ink composition to prevent unwanted microbial growth, which may occur over time. The biocide may be used either singly or in combination. Suitable biocides for the ink-jet ink of the present invention include sodium dehydroacetate, 2-phenoxyethanol, sodium benzoate, sodium pyridinethion-1-oxide, ethyl p-hydroxybenzoate and 1,2-benzisothiazolin-3-one and salts thereof.

[0108] Preferred biocides are ProxelTMGXL and ProxelTMUltra 5 available from ARCH UK BIOCIDES and BronidoxTMavailable from COGNIS.

[0109] A biocide is preferably added to the aqueous medium in an amount of 0.001 to 3 wt.%, more preferably 0.01 to 1.0 wt. %, each based on the total weight of the liquid.

[0110] The ink composition may further comprise at least one thickener for viscosity regulation in the liquid. Suitable thickeners include urea or urea derivatives, hydroxyethylcellulose, carboxymethylcellulose, hydroxypropylcellulose, derived chitin, derived starch, carrageenan, pullulan, proteins, poly(styrenesulphonic acid), poly(styrene-co-maleic anhydride), poly(alkyl vinyl ether-co-maleic anhydride), polyacrylamid, partially hydrolyzed polyacrylamid, poly(acrylic acid), poly(vinyl alcohol), partially hydrolyzed poly(vinyl acetate), poly(hydroxyethyl acrylate), poly(methyl vinyl ether), polyvinylpyrrolidone, poly(2-vinylpyridine), poly(4- vinylpyridine) and poly(diallyldimethylammonium chloride).

[0111] The thickener is added preferably in an amount of 0.01 to 20 wt.%, more preferably 0.1 to 10 wt.% based on the liquid. A.5. Application of a topcoat onto printed leather

[0112] A topcoat or topcoat is usually applied for enhancing the scratch resistance of the ink jet printed image.

[0113] The topcoat may be applied as a single layer or may be applied as multiple layers. The multiple layers may have a different composition for improving properties like scratch resistance or reducing the amount of extractables.PatXML 23 / 38 GX23014

[0114] A topcoat layer may have the same or a similar composition as the basecoat. Usually, a topcoat layer is somewhat optimized according to the leather application. For example, flexibility does not play an important role for a leather book cover contrary to leather shoes. Hence, a protective topcoat layer for a book cover may be optimized towards scratch resistance rather than flexibility.

[0115] A topcoat layer preferably includes a polymer or copolymer based on polyurethane, as this has been found to improve the abrasion and flexing performance of the printed leather. The topcoat layer may preferably further include a polyamide polymer or copolymer, such as casein. Polyamide has been found to improve the compatibility with the crust leather and to improve the scratch resistance of the topcoat.

[0116] Suitable polyurethanes include, UrepalTMPU147 and PU181 from CHEMIPAL S.p.A.; MelioTMPromul 61 from STAHL; AstacinTMFinish PS from BASF; EcrothanTM4075, 4078 and 4084 from MICHELMAN; IncorezTMCS8073 and CS065-195 from INCOREZ. Suitable topcoat containing polyurethane binders include RODA® Fix range, Aquaderm® finish range from TFL. The dry weight of the polyurethane in the topcoat is preferably in the range of 0.5 to 6 g / m2.

[0117] Suitable polyamides include RODA® Bind range from TFL, the PA emulsion types ED310 and 161148 CX from MICHELMAN. The dry weight of the polyamide in the topcoat is preferably less than 7 g / m2, more preferably less than 5 g / m2.

[0118] Other types of preferred polymers to be used in the topcoat include polyacrylates. Polyacrylates generally provide good flexibility and are preferably used alone or in combination with polyurethanes.

[0119] A cross-linker may be incorporated in the topcoat to improve the strength and the adhesion to ink layer. The dry weight of the cross-linker in the topcoat is preferably less than 8 g / m2, more preferably less than 4.0 g / m2.

[0120] Suitable polyacrylates and crosslinkers for the topcoat are given in § A.2.

[0121] The topcoat is preferably applied by spraying, but may be applied by any coating technique known, such as reverse or synchro roller coating, knifePatXML 24 / 38 GX23014 coating, extrusion coating, slide hopper coating curtain coating and transfer coating.

[0122] The topcoat is most preferably a transparent topcoat, but may be a translucent topcoat. By having a transparent topcoat, the decorative image is clearly visible through the topcoat. By using a translucent topcoat, a special aesthetic effect is created.

[0123] If a matt top surface is desired for the inkjet printed leather, a matting agent may be included. Any suitable matting may be used. Preferred matting agent include silica or intrinsically matting PUD and / or polymeric beads. Preferred commercially available examples of a matting dispersion agents are EudermTMSN2, RODA® Fix SFD, Aquaderm® Matt 200 and Aquaderm® Matt 102 from TFL. B. An image receiving natural leather substrate

[0124] It is further an embodiment of the present invention to include an image receiving natural leather substrate comprising: - crusted leather; and - a base coat layer onto a surface of the crusted leather, the base coat layer comprising a pigment and a binder selected from the group consisting of a polyacrylate, a polyurethane, a polyamide, a polybutadiene and combinations thereof; and - a pre-treatment layer onto at least a part of the base coat layer, the pre- treatment layer comprising a fixing agent being a multivalent metal salt or a cationic polymer and a binder selected from the group consisting of a polyacrylate, a polyurethane, an amide, a polyester and a combination thereof.

[0125] The image receiving natural leather substrate according to the present invention is an intermediate product which can be used as a recording medium for inkjet printing an image by means of inks, preferably water based inkjet inks, but also for other printing applications such as screen printing.

[0126] The image receiving natural leather substrate according to the invention is preferably prepared according to the method as described in § A.PatXML 25 / 38 GX23014 C. Examples C.1. Materials

[0127] All materials used in the following examples were readily available from standard sources such as Aldrich Chemical Co. (Belgium) and Acros (Belgium) unless otherwise specified. Where used, water is demineralised water (DI). ^ White crusted leather is supplied by TFL ^ PU-1 is RODA® PUR 76, an anionic polyurethane resin supplied by TFL ^ PU-2 is RODA® PUR WX 1418F, an anionic polyurethane resin supplied by TFL ^ PU-3 is RODA® PUR 5101, a non-ionic polyurethane based leveler supplied by TFL ^ IPA is isopropanol ^ PU-4 is RODA® PUR 64 N, a polyurethane based resin supplied by TFL ^ FILL 1 is RODA® Base WH 0303, a binder / filler supplied by TFL ^ FILL 2 is RODA® Base 5514, an anionic acrylic binder / filler supplied by TFL ^ CROSS 1 is RODA® Link 5777, a nonioinic modified carbodiimide based crosslinker supplied by TFL ^ CROSS 2 is RODA® Link C70, supplied by TFL ^ ACR is RODA® Cryl NP 86, an anionic polyacrylic resin supplied by TFL ^ COL 1 is RODA® Car White P, a white pigment dispersion containing about 15 wt.% of pigment and supplied by TFL ^ COL 2 is Diamond HSDC X1, a cyan water based pigment dispersion supplied by Diamond ^ COL 3 is RODA® Lite White 07, a white pigment dispersion containing about 15 wt.% of pigment and supplied by TFL ^ FIX is RODA® Fix SFD , an aliphatic polyurethane based aqueous formulation supplied by TFLPatXML 26 / 38 GX23014 ^ CAR is RODA® Car Dull 92 / N, a polyurethane and matting agent aqueous formulation supplied by TFL ^ FEEL is RODA® Feel S5796, a water-based silicone emulsion supplied by TFL ^ BIO is a 5wt. % aqueous solution of 1,2-benzisothiazolin-3-one available as ProxelTMK from YDS CHEMICALS NV. ^ Liquilube 404E is a 35 wt.% aqueous HDPE wax dispersion from Lubrizol ^ Ultralube GA 1042 is a 35 wt.% HDPE wax dispersion from KEIM- ADDITEC SURFACE GMBH ^ SURF 2 is Synperonic PE P105-SS, an ethyleneoxide- propyleneoxide copolymer surfactant from Croda chemicals) ^ SURF 3 is Surfynol 104PG50, a surfactant from Evonik, containing 50 wt.% solution of 2,4,7,9-Tetramethyl-5- decyne-4,7-diol in propylene glycol ^ RES 1 is Printrite DP379, an aqueous 30 wt.% dispersion of a polyether based polyurethane from Lubrizol ^ RES 2 is Aquacer 530, an aqueous dispersion containing 32 wt.% oxidized HDPE wax from BYK ^ PD is 1,2-propanediol from DOW ^ HD is 1,2-hexanediol from Degussa ^ BD is n-butanol from Univar ^ SALT is Mg(NO3)2.6H2O Magnesium nitrate hexahydrate from Merck Group C.2. Evaluation methods C.2.1. Sample preparation

[0128] Adhesion (ADH) and basecoat (BC) liquids were applied (unless mentioned otherwise) in that order, on a white crusted leather supplied by TFL, using a PRO-TEK 2600 spray gun. The base coated leather was obtained by consecutively applying 1 layer of ADH, 2 layers of BC-1 (A, B or C) and 1 layer of BC-2 (A or B), except if mentioned otherwise. The wetPatXML 27 / 38 GX23014 layer weights are indicated in Table 1. After each application of a liquid, samples are dried in a convection oven for 5 minutes at 80°C. After drying, the last layer of the BC-1 (A, B or C), the coated leather sample was ironed at 70°C with a pressure of 50 bar for 5 seconds.

[0129] For the pre-treatment layer (IL), a wet coating weight as indicated in Table 1, is applied before drying for 5 minutes in a convection oven at 80°C. The pre-treatment liquid is applied on top of the BC. In certain examples layers can be omitted selectively.

[0130] After applying and drying the adhesion liquid, basecoat composition and pre-treatment liquid (unless mentioned otherwise), samples were printed by means of an ImageXpert JetXpert with GIS print head driving electronics for FujiFilm Dimatix Samba print heads (Samba G3L) with a drop volume between 5.4-6.5 pl at a voltage between 19.5-23.5 V at 32 °C and with a firing frequency of 7.8 kHz using aqueous cyan ink, unless mentioned otherwise. The printed images were dried at 60°C for 2 minutes in an oven resulting in an ink load of 9 mL / m² (unless mentioned otherwise).

[0131] Unless mentioned otherwise, two layers of a topcoat (TC) are applied on the dried prints using a spray gun, according to the wet layer weights indicated in Table 1. After each application of a liquid, samples are dried in a convection oven for 5 minutes at 80°C. Table 1 Total wet coating weight of each layer (g / m²) min max ADH 16.1 43.1 BC-1A 16.1 43.1 BC-1B 16.1 43.1 BC-1C 16.1 43.1 BC-2A 16.1 43.1 BC-2B 16.1 43.1PatXML 28 / 38 GX23014 IL 16.1 32.3 TC 16.1 19.4 C.2.2. Image Quality

[0132] The image quality of the printed images was evaluated by visually analysing the following: 1) ink spreading and 2) coalescence / mottle.

[0133] Ink spreading: the ink should completely cover the solids in the printed image. A lack of ink spreading is demonstrated by the appearance of white lines in the solid areas. The evaluation was conducted by visually observing the solid areas and by scoring according to Table 2 Table 2 Ink spreading A Excellent: Complete coverage B Intermediate: Some white lines visible in solid areas C Poor: A lot of white lines visible in solid areas

[0134] Coalescence / Mottle: the ink should homogenously and intensely cover the solids in the printed image. Coalescence was evaluated by visually observing the solid areas and by giving a score as indicated in Table 3. Table 3 Coalescence / mottle A None / limited: Homogeneous coverage of solid areas B Intermediate: Some inhomogeneities seen in coverage of solid areas C Strong: Strong inhomogeneity

[0135] In both image quality evaluations, a score of ‘C’ is not acceptable. C.2.3. Flexibility

[0136] Printed, top coated samples as described in § C.2.1. were dye cut to a sample of 45 by 70 mm. The flexibility was determined on a Bally flexo-PatXML 29 / 38 GX23014 meter FT116 at room temperature wherein samples had to endure a cycle of 20000 flexes (at 1000 flexes per minute). The amount of cracks in, or damage to the leather determines the score.

[0137] They are visually evaluated by means of a microscope at 8x magnification according to the criteria in the Table 4. For dry flexing samples are mounted as such. For wet flex, samples are first submerged into deionized water in a glass dish and placed in a desiccator with reduced pressure of - 4kPa for 4 minutes, after which normal atmospheric pressure is restored. Next the excess water is removed from the test piece using blotting paper, after which the wet flexing test is initiated without delay. Table 4 Damage in flexing zone (Flexing behaviour) A Not visible by the naked eye and / or microscope B Some damage visible with the naked eye but substrate is not visible C Severe damage visible with the naked eye, leather is visible / ink is peeling off C.2.4. Abrasion

[0138] To test abrasion resistance a circular piece (38 mm diameter) was cut, incorporating a printed part (full solid) next to an unprinted part. The sample was placed in a Martindale tester (from SDS Atlas), after which 1000 cycles (20 minutes) of a dedicated Lissajous (3 mm diameter) rubbing pattern are performed using a standard abradant fabric (ISO12947-1) with a pressure of 12 kPa. Samples are visually evaluated according to the Table 5. Table 5 Abrasion resistance of print A No damage seen in printed areas B Print is damaged, but substrate is not visible yetPatXML 30 / 38 GX23014 C Print is damaged and substrate below is (clearly) visible Abrasion - smearing out A No smearing out of ink on unprinted area B Visible smearing out of ink on unprinted area C Excessive smearing out of ink on unprinted area

[0139] In both abrasion resistance evaluations, a score of ‘C’ is practically not acceptable. C.2.5 Colour

[0140] The colour values of each sample were measured 3 times (then averaged) with a Gretag Macbeth SPM50 spectrophotometer. The CIEL*a*b* coordinates were determined for a 2° observer and a D50 light source, without filter (M0).

[0141] The colour difference between two colours 1 and 2, is determined according to the CIE76 colour difference formula and is defined as: ∆ ^^^^= ^( ^^∗^− ^^∗ଶ)ଶ+ ( ^^^∗− ^^ଶ∗)ଶ+ ( ^^^∗− ^^ଶ∗)ଶ. A value for ΔE ≈ 2.3 corresponds to a JND (just noticeable difference), as explained in Sharma, Gaurav (2003). Digital Colour Imaging Handbook (1.7.2 ed.). CRC Press. ISBN 0-8493- 0900-X. C.3. Composition of the liquids used

[0142] Table 6 below shows the composition of the adhesion liquid (ADH), the basecoat composition (BC’s) and the topcoat (TC) used. Table 6 Wt. % of product in formulation ADH BC-1A BC-1B BC-1C BC-2A BC-2B TC PU-1 20 0 0 0 3.6 3.6 0 PU-3 10 9.1 8.7 9.1 3.6 3.6 0 IPA 10 0 0 0 0 0 0PatXML 31 / 38 GX23014 FILL 1 0 22.7 21.7 22.7 0 0 0 PU-4 0 9.1 8.7 9.1 0 0 0 ACR 0 9.1 8.7 9.1 1.8 1.8 0 COL 1 0 9.1 0 0 10.9 0 0 COL 3 0 0 13.0 9.1 0 10.9 0 CROSS 1 0 2.5 2.4 2.5 2.5 2.5 0 FILL 2 0 0 0 0 36.4 36.4 0 PU-2 0 0 0 0 7.3 7.3 0 FIX 0 0 0 0 0 0 20 CAR 0 0 0 0 0 0 10 FEEL 0 0 0 0 0 0 1 CROSS 2 0 0 0 0 0 0 3 DI Complete to 100%

[0143] Table 7 lists the composition (in wt.% of each product) of the inventive pre- treatment liquids (IL) used. Table 7 INV_IL1 INV_IL2 INV_IL3 INV_IL4 INV_IL5 PU-2 7.3 7.3 7.3 0 12.0 ACR 1.8 1.8 1.8 0 0 COL 1 0 0 10.9 0 0 PU-1 3.6 3.6 3.6 0 6 PU-3 0 0 3.6 0 0 CROSS 1 2.5 0 2.5 0 4.1 SALT 8.0 8.0 8.0 8.0 9.6 RES 1 0 0 0 17.8 0 RES 2 0 0 0 8.0 0 SURF 2 0 0 0 1.0 0 PD 0 0 0 19.0 0 HD 0 0 0 2.9 0 DI To complete to 100%PatXML 32 / 38 GX23014

[0144] Table 8 lists the composition (in wt. % of each product) of the comparative pre-treatment liquids (IL) used. Table 8 COMP_IL1 COMP_IL2 PU-2 7.3 7.3 ACR 1.8 1.8 PU-1 3.6 3.6 CROSS 1 2.5 0 DI To complete to 100%

[0145] Table 9 lists the composition (in wt.% of each product) of the inks used. Table 9 INK_1 INK_2 INK_3 Liquilube 404E 2.84 0.00 0.00 Ultralube GA 1042 0.00 0.00 1.43 PD 39.50 43.00 42.00 BD 3.00 2.95 2.95 SURF 3 0.40 0.40 0.40 BIO 0.01 0.01 0.01 COL 2 13.16 13.16 13.16 DI To complete to 100% C.4. Example 1

[0146] Example 1 shows the need for a pre-treatment layer containing a multivalent metal salt as fixing agent.

[0147] Samples were prepared according to § C.2.1. Table 10 Coalescence / Ink Sample BC-1A BC-2A IL INK Mottle spreading PL-INV1 Yes Yes INV_IL1 INK_3 A A PL-INV2 Yes Yes INV_IL2 INK_3 A APatXML 33 / 38 GX23014 PL-COMP1 Yes Yes COMP_IL1 INK_3 C C PL-COMP2 Yes Yes COMP_IL2 INK_3 C C PL-COMP3 Yes Yes - INK_1 C C

[0148] Table 10 shows image quality of solids prints printed as described in § C.2.1. and evaluated as in § C.2.2. It must be mentioned that the values of the flexibility and abrasion resistance of the printed images all show an A-value.

[0149] The table demonstrates that a pre-treatment layer, comprising a multivalent metal salt as fixing agent, is needed to obtain sufficient high image quality (coalescence and ink spreading) of the printed images. C.5. Example 2

[0150] Example 2 shows the need for a pre-treatment layer containing a multivalent metal salt as fixing agent, preferably devoid of water-soluble resins.

[0151] Samples were prepared according to § C.2.1. The ink used for printing a solid image was INK-1. Table 11 Dry Wet Abrasion Abrasion Sample BC-1A BC-2A IL flex flex print - smear PL-INV3 Yes Yes INV_IL3 A A A A PL-INV4 Yes Yes INV_IL4 A B B B

[0152] Table 11 shows evaluation of prints according to § C.2.3 and C.2.4. Although coalescence and ink spreading are good for both examples (A- value for coalescence and spreading), a primer containing propylene oxide-ethylene oxide block copolymer as water soluble polymer, decreases to some extend, both wet flex behaviour and abrasion resistance. C.7. Example 3PatXML 34 / 38 GX23014

[0153] In Example 3 it is shown that increasing the amount of pigment in one of the base coat layers allows to omit one of the other (pigmented) base coat layers.

[0154] Samples were prepared according to § C.2.1. (see Table 12), but PL-INV6 has been prepared without a second base coat layer (BC-2B). The prints were made with INK_3, jetted with a Samba G5L printhead, resulting in an ink load of about 14 mL / m².

[0155] Table 12 shows the values of the optical and physical property measurements of the obtained samples PL-INV5 to PL-INV6. Each sample was made twice, hence Table 12 displays average values. Both samples do show an ‘A’-value for Dry flex, Wet flex, Abrasion print and Abrasion- smear. Table 12 Sample BC-1 BC-ILL* a* b*2B PL-INV5 BC-1C Yes INV_IL543,47 -12,51 -55,46PL-INV6 BC-1B No INV_IL541,80 -13,01 -56,36

[0156] It can be seen that using a base coat layer with a higher pigment load (wet or dry) still gives excellent physical properties, without impacting the final visual aspect (ΔEabof 1,97), even if only one base coat layer is applied. The application of only one base coat layer implies a production method containing one step less, resulting in a more cost-effective production method. C.8. Example 4

[0157] In Example 4, it is shown that different aqueous inkjet inks applied according to the method of the invention lead to images with excellent physical properties.

[0158] Samples were prepared according to § C.2.1. The prints were made with INK_1, INK_2 and INK_3.PatXML 35 / 38 GX23014

[0159] Table 13 shows the results of the abrasion tests on the printed images (samples PL-INV7 to PL-INV10). Image quality remained excellent (a value = A) and unchanged by modifying the inks. Table 13 Example BC- BC- IL Ink Dry Wet Abrasion Abrasion 1A 2A flex flex print - smear PL-INV7 Yes Yes INV_IL3 INK_1 A A A A PL-INV8 Yes Yes INV_IL3 INK_2 A A A A PL-INV9 Yes Yes INV_IL2 INK_2 A A A A PL-INV10 Yes Yes INV_IL2 INK_3 A A A A

[0160] Table 13 shows that prints obtained with inks containing or devoid of resin particles, when printed according to the method of the invention, show all excellent physical properties.

Claims

PatXML 36 / 38 GX23014 Claims Claim 1. A method of image recording on natural leather including the steps of: - applying a base coat composition onto a surface of crusted leather, the base coat composition comprises water, a colorant, being a pigment and a binder selected from the group consisting of a polyacrylate, a polyurethane, a polyamide, a polybutadiene and a combination thereof, such as to form a base coat layer; and - applying a pre-treatment liquid onto at least a part of the base coat layer, the pre-treatment liquid comprising water, a fixing agent being a multivalent metal salt or a cationic polymer, a binder selected from the group consisting of a polyacrylate, a polyamide, a polyester, a polyurethane, a polyether urethane and a combination thereof, such as to form a pre-treatment layer; and - inkjet printing an image onto the pre-treatment layer using an aqueous inkjet ink comprising a pigment and a water-soluble organic solvent; - drying the image. Claim 2. The method of image recording according to Claim 1 wherein a topcoat is applied onto at least a part of the image, the topcoat comprises water and a binder selected from the group consisting of a polyacrylate, a polyurethane and a wax. Claim 3. The method of image recording according to any of the preceding claims wherein the pre-treatment liquid further comprises a second binder selected from the group consisting of a polyurethane, a polyacrylate and a combination thereof. Claim 4. The method of image recording according to any of the preceding claims wherein the base coat composition comprises a crosslinker selected from the group consisting of isocyanate based cross-linkers, aziridine based crosslinkers, aldehyde based cross-linkers such as formaldehyde, melamine formaldehyde derivatives, urea formaldehyde resins, glutaraldehyde, epoxides, oxazolidines and carbodiimides. Claim 5. The method of image recording according to any of the preceding claims wherein an adhesion liquid is applied prior to the application of a base coat composition onto the surface of crusted leather, the adhesion liquidPatXML 37 / 38 GX23014 comprises a solvent and a polyurethane, a polyether urethane or a combination thereof. Claim 6. The method of image recording according to any of the preceding claims wherein the aqueous inkjet ink further comprises a resin selected from the group consisting of a polyacrylate, a polyurethane and a wax. Claim 7. The method of image recording according to any of the preceding claims wherein the amount of pigment in the base coat layer is 35 wt.% or more with respect to the total weight of the solids in the base coat layer. Claim 8. The method of image recording according to any of the preceding claims wherein the polyurethane in the pre-treatment liquid is an anionic polyether urethane or an anionic aliphatic polyurethane. Claim 9. An image receiving natural leather substrate comprising: - crusted leather; and - a base coat layer onto a surface of the crusted leather, the base coat layer comprising a pigment and a binder selected from the group consisting of a polyacrylate, a polyurethane, a polybutadiene, a polyamide and combinations thereof; and - a pre-treatment layer onto at least a part of the base coat layer, the pre- treatment layer comprising a fixing agent being a multivalent metal salt or a cationic polymer and a binder selected from the group consisting of a polyacrylate, a polyurethane, a polyamide, a polyester, a polyether urethane and a combination thereof. Claim 10. The image receiving natural leather substrate according to Claim 9 wherein an adhesion layer contacts the surface of the crusted leather, the adhesion layer comprises a polyurethane, a polyether urethane or a combination thereof. Claim 11. The image receiving natural leather substrate according to Claim 9 and Claim 10 wherein the base coat composition comprises a crosslinker selected from the group consisting of isocyanate based cross-linkers, aziridine based crosslinkers, aldehyde based cross-linkers such as formaldehyde, melamine formaldehyde derivatives, urea formaldehyde resins, glutaraldehyde, epoxides, oxazolidines and carbodiimides.PatXML 38 / 38 GX23014 Claim 12. The image receiving natural leather substrate according to Claim 9 to Claim 11 wherein the pre-treatment layer further comprises a second binder selected from the group consisting of a polyurethane, a polyacrylate and a combination thereof. Claim 13. The image receiving natural leather substrate according to Claim 9 to Claim 12 wherein the polyurethane in the pre-treatment layer is an anionic polyether urethane or an anionic aliphatic polyurethane. Claim 14. The image receiving natural leather substrate according to Claim 9 to Claim 13 wherein the amount of pigment in the base coat layer is 35 wt.% or more with respect to the total weight of the solids in the base coat layer. Claim 15. A liquid set for image recording onto crusted natural leather comprising: - an adhesion improving liquid comprising a solvent and a binder selected from the group consisting of a polyurethane, a polyether urethane or a combination thereof. - a base coat composition comprising water, a pigment and a binder selected from the group consisting of a polyacrylate, a polyurethane, a polyamide and combinations thereof. - a pre-treatment liquid comprising a fixing agent being a multivalent metal salt or a cationic polymer and a binder selected from the group consisting of a polyacrylate, a polyurethane, a polyamide, a polyester and a combination thereof.