阅读说明：本技术 制造经装饰皮革的方法 (Method for producing decorated leather ) 是由 L·德勒克 于 2019-10-08 设计创作，主要内容包括：经装饰天然皮革的制造方法包括以下步骤：将具有真皮面、粒面和边缘的半硝皮革施加在具有定位装置的输送机系统上,和通过对着所述定位装置移动所述边缘使所述半硝皮革对准；和将所述对准的半硝皮革层压在具有粘合剂层的临时载体上,其中朝着所述临时载体输送所述输送机系统上的所述半硝皮革,并相对于所述输送机系统移动所述临时载体的同时,所述真皮面通过所述粘合剂层附着在所述临时载体上；和通过喷墨印刷系统使用一种或多种着色喷墨油墨在所述粒面上喷墨印刷图像。(The method for manufacturing the decorated natural leather comprises the following steps: applying a semi-finished leather having a leather surface, a grain surface, and an edge on a conveyor system having a positioning device, and aligning the semi-finished leather by moving the edge against the positioning device; and laminating the aligned semi-leather on a temporary carrier having an adhesive layer, wherein the leather side is attached to the temporary carrier by the adhesive layer while transporting the semi-leather on the conveyor system toward the temporary carrier and moving the temporary carrier relative to the conveyor system; and ink-jet printing an image on the grain side with one or more pigmented ink-jet inks by an ink-jet printing system.)

1. A method of manufacturing decorated natural leather comprising the steps of:

-applying a semi-tanning leather having a leather surface, a grain surface and an edge on a conveyor system having a positioning device, and

-aligning the semi-nitro-leather by moving the edge against the positioning means; and

-laminating the aligned semi-nitro-leather on a temporary carrier having a top layer, wherein the leather side is attached to the temporary carrier by the top layer while conveying the semi-nitro-leather on the conveyor system towards the temporary carrier and moving the temporary carrier relative to the conveyor system; and

-ink-jet printing an image on the grain side by an ink-jet printing system using one or more pigmented ink-jet inks.

2. The method of claim 1, wherein the conveyor system comprises a set of positioning devices for applying and aligning a set of crust leather; and

wherein the set of aligned semi-nitro leathers are laminated on the temporary carrier during the conveying step and the relative moving step to inkjet print a set of images on the laminated set of aligned semi-nitro leathers.

3. The method of claim 2, comprising the steps of: leveling the laminated semitanning leather on the temporary carrier by applying pressure on the semitanning leather prior to the inkjet printing step.

4. The method of claim 3, wherein the conveyor system comprises a plurality of holding devices for connecting the set of positioning devices; and

wherein the method comprises the step of connecting the positioning device to the holding device.

5. The method of claim 4, wherein the locations of the set of connected positioning devices are transmitted to the inkjet printing system to inkjet print the set of images according to a layout determined by the transmitted locations.

6. The method of claim 5, wherein the retaining device is a perforation or a cavity in the conveyor system, wherein an extension from the positioning device is adapted for connecting the positioning device and the retaining device.

7. The method of claim 6, wherein the positioning device further comprises: a round pin, an elongated sheath, a beam or a connected beam at a determined angle, preferably 90 ° to align the semi-nitro leather.

8. The method of any one of claims 1 to 7, wherein the conveyor system is a conveyor belt and the conveyor system optionally comprises a fixed or rolling edge at its output location.

9. The method of any one of claims 1 to 8, wherein the temporary support is a paper or plastic foil or a polyester felt.

10. The method of any one of claims 1 to 9, wherein the top layer is an adhesive layer.

Technical Field

The present invention relates to the manufacture of decorated natural leather.

Background

The manufacture of natural leather products is well known and can be generally divided into five stages as shown in figure 1. Preparation phase 1 often occurs partly in slaughterhouses and partly in tanneries, while phases 2 to 4 occur in tanneries and phase 5 occurs at leather manufacturers. In the first stage, the preparation stage, the skin is removed (peeled) from the animal and pre-treated for the second stage of tanning. Pretreatment may involve processes such as soaking, liming, unhairing, flaking and pickling (pH adjustment to aid in tanning agent penetration). During the tanning stage, the proteins of the hide or skin are converted into stable substances that do not decay. Chromium is most commonly used as a tanning agent, whereby the tanned product gives a light blue color, and is therefore commonly referred to as "wet blue". In the third stage of semi-tanning (tanning), the tanned leathers are dried and softened. Mirabilitum often includes processes such as stripping (removing surface-fixed tanning material), fatliquoring (fats, oils and waxes are fixed on the leather fibers), dyeing, whitening, physical softening and buffing (abrading the leather surface to reduce particle defects). In a fourth stage, known as finishing, the leather is prepared for sale to leather goods manufacturers. Finishing operations may include painting, polishing, and embossing. In a fifth stage, leather articles are manufactured, which involves processes that may include cutting, perforating, sewing, leather wrapping, decoration, and embossing.

In the past, natural leather has been decorated by screen printing. However, screen printing is labor intensive because each color requires a separate screen. This is expensive and time consuming, especially when personalization or customization is required.

Digital printing techniques have been studied on finished leather, but many solutions to finished leather remain inferior. Inkjet technology for textile printing using thermal transfer paper has been explored for leather printing. However, as with ink jet printing directly on natural leather, it has been found that the process of ink jet printing a dye-based image onto a transfer sheet and subsequently transferring the image by heat to tanned leather results in an unacceptable quality of many luxury leather products. Examples of such inkjet processes are disclosed in WO 01/32434 a (gilham) and US 2016067984 a (chung). Further improvements are required in aspects such as image quality, photobleaching of transfer dyes, and scratch resistance.

Photobleaching of dyes can be addressed by the use of pigmented inks. GB 2510696 (SERICOL) discloses a method of printing on leather or synthetic leather substrates by: depositing a primer layer on a substrate, the primer comprising a thermoplastic resin and water; at least partially drying and/or curing the primer; ink-jet printing a pigmented mixed solvent/radiation curable ink on the primer layer; drying and curing the mixed ink layer.

Recently, high quality decorated leather has been obtained by printing "in" the tanned leather using pigmented inks. EP 2825387 a (codus) discloses a process for printing into tanned leather comprising the steps of: a) applying an ink receptor directly on the leather surface; b) applying the ink directly to a receptor by ink jet; c) applying an additive to the ink; d) heating the surface of the barrier substantially impermeable to the ink; and e) directly contacting the heated barrier with the ink receptors, additives and inks on the surface of the leather to soften the additives, ink receptors and inks into the leather so that the inks penetrate into the leather.

Natural leather is cut into leather pieces, which can be further cut into smaller pieces and sewn together into leather articles. By ink-jet printing on the leather block, the leather article can be personalized or can be a limited version of the leather article by using ink-jet technology decoration.

However, applying all of the leather pieces from the inkjet printing station to the printing station is a labor intensive task that results in long production times, where no ink is consumed. As the skilled person knows, the long waiting time between printing is not good for inkjet print heads. This can be avoided by regular maintenance of the inkjet print head, but when the inkjet print head is maintained, this also leads to an extension of the long production time and ink consumption. Such time delays and ink waste should be avoided, and there is therefore a need to obtain a more efficient and economical method of manufacturing high quality decorated natural leather articles that allow personalization and have short delivery times to the customer, since long delivery times reduce the feeling of luxury.

Disclosure of Invention

In order to overcome the above problems, a preferred embodiment of the present invention has been accomplished using the method for manufacturing decorated natural leather of claim 1.

Drawings

Fig. 1 shows a flow diagram of a conventional manufacturing of leather articles involving different stages and locations.

Fig. 2 shows a cross-section of a manufacturing line according to a preferred embodiment of the invention.

Fig. 3 shows a cross-section of a manufacturing line according to a preferred embodiment of the invention.

Fig. 4 shows a cross-section of a manufacturing line according to a preferred embodiment of the invention.

Detailed Description

Method for manufacturing decorated natural leather

The method for manufacturing the decorated natural leather according to the preferred embodiment of the present invention comprises the steps of:

-applying a semi-tanning leather having a leather surface, a grain surface and an edge onto a conveyor system having a positioning device, and

-aligning the semi-nitro-leather by moving the edge against the positioning means; and

-laminating the aligned semi-nitro-leather on a temporary carrier having a top layer, wherein the leather side is attached to the temporary carrier by the top layer while conveying the semi-nitro-leather on the conveyor system towards the temporary carrier and moving the temporary carrier relative to the conveyor system; and

-ink-jet printing an image on the grain side by an ink-jet printing system using one or more pigmented ink-jet inks. The top layer is preferably an adhesive layer to better attach the dermal surface to the temporary carrier.

The invention solves the possibility of aligning one or more leather pieces on top of a temporary carrier, such as an adhesive temporary carrier, so that said leather pieces can be easily printed in an aligned manner. The conveyor system is preferably a conveyor belt and more preferably angled to more easily align and move against the positioning device.

In a preferred embodiment of the manufacturing process, the crust leather, base coat, decorative image and top coat are hot pressed. Such a process is known from WO 2013/135828 a (codus) to allow at least a part of the sandwich "base coat/decorative inkjet image/top coat" to penetrate and integrate into the leather.

In a preferred embodiment, a plurality of crust leathers are applied on the conveyor system to align the crust leathers on the temporary carrier. The conveyor system therefore comprises a set of positioning devices for applying and aligning a set of crust leather. Laminating the set of aligned semi-nitro leathers on the temporary carrier during the conveying step and the relative moving step for inkjet printing a set of images on the laminated set of aligned semi-nitro leathers.

By applying the leathers in front of a conveyor system and subsequently transferring them to a temporary carrier; the leather is mounted in an aligned manner and glued to a temporary carrier. If the alignment is determined, a set of images may be printed on the installed hide according to the alignment; thereby aligning on top of the installed hide. By means of the invention, a plurality of leathers can be printed in an aligned manner, which saves a lot of time. The conveyor system may be a drum, but it is preferably a conveyor belt.

The set of positioning means is preferably arranged in a grid pattern, whereby the set of leathers is arranged in the same pattern on the temporary carrier. The grid pattern preferably comprises columns and/or rows, whereby a group of leathers is arranged in columns and/or rows.

Preferably, the manufacturing comprises the steps of: flattening the laminated nitrocellulose leather on the temporary carrier by applying pressure on the nitrocellulose leather prior to the inkjet printing step. The pressure may be applied by a pressure roller.

In preferred embodiments, additional positioning devices may be added or removable positioning devices may be added to the conveyor system. Thus, the positioning means on the conveyor system are releasable, wherein the position depends on the shape of the crust leather and/or the determined distance between the crust leathers. Thus, the conveyor system may comprise a plurality of holding devices for connecting the set of positioning devices; and wherein the method may comprise the steps of:

-connecting the positioning means to the holding means; or

-disconnecting the positioning device from the holding device.

In a preferred embodiment, the positioning device for aligning the raw leather comprises: a round pin, an elongated sheath, a beam or a connected beam at a determined angle, preferably 90 deg.. In another preferred embodiment, the positioning device includes an extension that engages a perforation or cavity in the conveyor system to retain the positioning device. Shelf support pegs used in cabinets may be used.

In a preferred embodiment, the location of the set of attached positioning devices is determined and transmitted to an inkjet printing system for inkjet printing the set of images according to a layout determined by the transmitted location. In a preferred embodiment, the shape/size of the leather applied on the conveyor system is also transferred to an inkjet printing system to inkjet print the set of images according to a layout determined by the position transferred and the shape/size.

It has been found that in order to facilitate the transfer of the crust leather from the conveyor belt, which is the conveyor system of the invention, to the temporary carrier, there is a fixed or rolling edge at the output position of the conveyor system. The output position is the position where the semi-niter leather leaves the conveyor system.

By temporary carrier is meant that the carrier is present during a certain period of the manufacturing process. In the present invention, the temporary support is used during ink-jet printing. Separating the temporary carrier from the laminated aligned semi-nitro leather prior to assembling the leather into a leather article.

In a preferred embodiment of the manufacturing method, the temporary carrier is a paper or plastic foil. An advantage of such a foil is that human transport of the decorated natural leather is still feasible due to the low weight contribution of the foil, especially when compared to metal, wooden or plastic plates as temporary carriers.

In one embodiment of the manufacturing method, the plastic foil is a transparent or translucent plastic foil. This allows backlighting of the semitanning leather attached to the plastic foil, so that printable surface areas and leather defects, such as scratches and holes, are easily detected when scanning the semitanning leather-attached temporary carrier.

In a preferred embodiment of the manufacturing method, the temporary carrier foil is a paper foil or an opaque plastic foil, most preferably white.

In a preferred embodiment of the manufacturing method, the adhesive is applied by coating or spraying, preferably by spraying. This allows a fast application of the leather on the temporary carrier, resulting in a higher productivity. Spraying is performed on the surface of the temporary carrier.

In a preferred embodiment of the manufacturing process, the adhesive exhibits a higher self-cohesion and a higher adhesion to the temporary support than to the nitrocellulose leather. If this is the case, the adhesive can be removed from the real leather side of the leather more quickly without causing any damage to the leather.

In a preferred embodiment of the manufacturing process, a primer coating is applied to the grain side of the leather, prior to the ink-jet printing step. It has been observed that such a base coat improves image quality because the leather contains irregularities and large depressions caused by residual pores (skin pores) and wrinkles that are originally present in the hide or skin. Upon inkjet printing, the ink collects in these irregularities and large depressions, resulting in uneven color density. These irregularities and large depressions are smoothed by applying a primer consisting of one or more layers.

In a particularly preferred embodiment of the manufacturing process, the base coat comprises a polyurethane-based polymer or copolymer. The presence of a polymer or copolymer based on polyurethane is advantageous for good flexibility. Enhanced compatibility between the UV pigmented inkjet ink and the leather was observed.

In a particularly preferred embodiment of the manufacturing process, the base coat is also applied on a temporary support coated or sprayed with an adhesive. This has the advantage that the inkjet-printed leather can be pinned on the temporary carrier without adhesion problems, since the adhesion of the adhesive present on the temporary carrier not covered by leather is neutralized by the base coat.

In a preferred embodiment of the manufacturing method, the adhesive is a pressure sensitive adhesive. Pressure sensitive adhesives are adhesives that form a bond between the leather and the temporary carrier when pressure is applied. No solvent, water or heat is required to activate the adhesive. The use of pressure sensitive adhesives results in increased productivity. If the leather is not completely flat on the temporary carrier, a portion of the leather can be easily removed to reattach it in a flat manner. Post-IT developed from 3M^TMSuch attachment to and subsequent removal from an object without damaging the object is well known in the form of a pad.

In a preferred embodiment of the manufacturing method, the one or more pigmented inkjet inks are one or more radiation curable pigmented inkjet inks, more preferably one or more UV curable pigmented inkjet inks. High image quality can be obtained by using UV curable pigmented inkjet inks because UV curing can quickly "freeze" the decorative image after the jetted ink is dropped on the leather or base coat. More preferably, the UV curable pigmented inkjet ink comprises water or an organic solvent in an amount of less than 25 wt%, more preferably less than 15 wt%, and most preferably from 0 to 10 wt%, based on the total weight of the ink. If no or only limited amounts of water or organic solvents are present, the penetration of the inkjet ink into the pores of the leather will be limited and an improved image quality will be obtained.

In a preferred embodiment of the manufacturing process, a top coat is applied over the decorative image and the base coat. The top coat serves as a protective layer for the decorative image, for example against scratches.

In a particularly preferred embodiment of the manufacturing process, the crust leather, the base coat, the image and the top coat are hot pressed and/or embossed. Such a hot pressing process is known from WO 2013/135828 a (codus) to allow at least a part of the sandwich "base coat/decorative inkjet image/top coat" to penetrate and integrate into the leather.

Embossing is commonly used to provide a design to leather, for example, the grain structure of other animals can be replicated to a certain leather. Typically, embossing is accomplished by pressing the leather grain structure against the grain side. Since the non-compressed leather fibres remain on top, a three-dimensional effect is created.

Sometimes the leather is ironed to make it smooth or shiny. Smooth leather is also less sensitive and easier to clean.

A decorative image is inkjet printed on the basecoat layer using one or more pigmented inkjet inks. In contrast to most dyes, pigmented inkjet inks ensure good light fastness, since leather articles are often used under outdoor conditions. The one or more pigmented inkjet inks may be aqueous inkjet inks, but are preferably UV curable pigmented inkjet inks because UV curing rapidly "freezes" the inkjet printed decorative image. The good image quality obtained further contributes to the luxurious appearance of the decorated leather article.

A preferred embodiment is an assembly of decorated natural leather attached to a temporary carrier by means of an adhesive, obtained by a manufacturing process as claimed in any one of claims 1 to 15.

Decorated natural leather and leather articles

Natural leather is classified into different grades, such as full grain, topgrain (which is essentially full grain, but with part of the grain layer sanded and the underlying split removed), and split leather (split leather). For the latter, the underlying layer of hide is removed and used to create split leather. Depending on the thickness of the underlying layers, a number of cross-sections may be created. Split leather has a rough appearance and is commonly used for making suede leather.

To avoid particle damage and fragility, chrome tanned hides or skins are preferably used, but other tanning methods, such as vegetable tanning, can also be used. After tanning, the leather is dried and softened into so-called crust leather. The crust may include a number of processes such as stripping (to remove surface-bound tanning material), fatliquoring (to bind fats, oils and waxes to the leather fibres), dyeing, whitening, physical softening and buffing (to abrade the leather surface to reduce particle defects).

The decorated natural leather can be used to make a wide range of leather products. Preferred leather articles include footwear, furniture, home furnishings, bags and cases, gloves, belts, purses, clothing, automotive leather (e.g., train, airplane, boat, and car seats), upholstery, books and stationery, packaging, equestrian articles, and the like.

Adhesive agent

The adhesive may be used to attach the leather of the saltpeter to the temporary carrier at its dermal surface. The top layer is then the adhesive layer. In the present invention, adhesive is applied to the temporary carrier prior to installation of the leather from the conveyor belt, which leather is aligned in front of the conveyor belt.

Any adhesive known in the art can be used in the present invention, from classically known adhesives to biomimetic based adhesives.

Repositionable adhesives are preferred because they help ensure a process for ensuring that the leather is completely flat attached to the carrier without causing a collision with the inkjet print head.

In the present invention, pressure sensitive adhesives are a particularly preferred type of adhesive.

Temporary carrier

There is no practical limitation on the composition of the temporary carrier. Preferred temporary supports of the present invention are polymers because of their light weight compared to, for example, metallic temporary supports. Synthetic polymers or natural polymers may be used for the temporary support.

Preferred natural polymers are cellulose-based, such as plain paper or resin-coated paper, such as polyethylene-or polypropylene-coated paper. Kraft paper is particularly preferred as a temporary carrier because it is strong enough and inexpensive.

Preferred synthetic polymers for the temporary carrier are polyethylene, polypropylene, polycarbonate, polyvinyl chloride, polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN) and Polylactide (PLA) and polyimide. Polyethylene terephthalate (PET) foil is particularly preferred as a temporary carrier due to its recyclability.

The temporary support may be transparent, translucent or opaque. Preferred opaque substrates include so-called synthetic papers, such as the Synaps by Agfa-Gevaert^TMGrade, which is a density of 1.10 g/cm³Or higher opaque polyethylene terephthalate foil. Synaps are particularly preferred^TMOM135AP and Synaps^TMOM135AR because they are pre-coated with an adhesive layer.

A white opaque temporary support has the advantage of providing a good contrast for the identifier, which is usually black.

There is no limitation on the shape of the substrate. It may be a flat sheet, such as a paper sheet or a polymer sheet, or it may be in the form of a paper roll or a polymer foil.

Another type of suitable material for the temporary carrier is a textile. The preferred textile is canvas, which is a very durable plain weave fabric that can be reused many times.

The temporary carrier is preferably an air-permeable support.

Breathable support

In the present invention, the breathable support is larger than natural leather and is preferably flat. The natural leather partially covers the support to have good adhesion at the edges of the natural leather. When the support is the same size as the natural leather and the leather completely covers the support, the edges of the natural leather can curl (wavy or crimp) due to the tufted leather face and its adhesive properties when vacuum is applied. This can lead to collisions with the print head of the inkjet printer.

The breathable support comprises one or more fibrous layers, wherein the dermal side of the natural leather is preferably in contact with fibrous layers from said one or more fibrous layers. The fibrous layer readily adheres to the fibrous and tufted leather faces. The fibrous layer may be coated and/or a nonwoven fabric, such as a felt. The felt may be wool felt, but it is preferably a polyester felt. Recycled polyester felt may also be used. Polyester felts are most preferred because of the tighter construction of the felts and because they can be used at operating temperatures above 30 ℃. The polyester felt may be blended with other materials such as wool.

In the present invention, the air permeability of the air-permeable support may be between 30 and 120L/(dm 2 xmin), preferably between 35 and 90L/(dm 2 xmin), at a pressure difference of 200 Pa. The air permeability may be measured using an AKUSTRONTM air permeability tester following the industry standards DIN 53887, DIN 53120, ISO9237 and ASTM D737-96. Therefore, air permeability is measured in minutes, abbreviated as "min".

If the air-permeable support comprises multiple layers on top of each other, one or more of said layers are fibrous layers, but preferably all layers are fibrous. The layer also needs to be breathable. Measuring the air permeability of the air permeable support on all of the multiple layers. Preferably, a first layer of the plurality of layers in facial contact with the dermis has a lower air permeability than a second layer, which is a subsequent layer of the first layer. Most preferably, subsequent layers of one of the plurality of layers have a higher air permeability.

If the layer in contact with the dermal surface is a nonwoven, the orientation of the fibers of the nonwoven and the fibers in contact with the dermal surface may be altered to have better adhesion to the fibrous and tufted dermal surface.

For ease of handling and a certain rigidity, the weight of the air-permeable support is preferably between 0.6 and 2.5 kg/m²In the meantime. While the thickness of the support is preferably between 1.5 mm and 4 mm, more preferably between 1.5 mm and 3 mm. In a preferred embodiment, the thickness of the air permeable support is offsetThe thickness of the supported natural leather is two times or more, but more preferably, the thickness of the air-permeable support is not more than 100 times the thickness of the supported natural leather.

In a preferred embodiment, the air permeable support is a conveyor belt that is wrapped around the vacuum support and a plurality of pulleys or gliders. The conveyor belt may be driven by a motor for generating a torque for one of the pulleys or may be conveyed when connected to a vacuum belt as a vacuum support. This last embodiment is highly preferred because the vacuum belt, which is the vacuum support, is arranged for correct printing, for example in register and at a controlled speed. If the vacuum support is a vacuum table, the air permeable support must be rigid and have low stretchability for printing in registration and at controlled speed.

The transport preferably has a continuous distance movement, also called discrete stepwise increments.

The breathable support may also be a sheet having one or more fibrous layers and wherein the area of the support is greater than the area of the natural leather.

When one or more natural leathers are supplied onto the air-permeable support, the position can be scanned by a camera system above the air-permeable support. If the support has registration marks or registration means or identification codes, the scanning can be used to optimize the supply chain of the decorated natural leather of the invention. In the post-treatment of decorated natural leathers, the identification code and the position of the natural leather or leathers can be used, for example, to cut or heat press or emboss or top coat the natural leather if the natural leather is still on the breathable support.

Conveying belt

The conveyor system of the present invention is preferably a conveyor belt. Preferably, the conveyor belt has two or more layers of material, with the lower layer providing linear strength and shape, also referred to as a framework, and the upper layer being referred to as a cover layer or support surface. The framework is preferably a woven fabric mesh, and more preferably a woven fabric mesh of polyester, nylon, glass fabric or cotton. The material of the cover layer is preferably various rubbers and more preferably a plastic compound and most preferably a thermoplastic polymer resin. However, other foreign materials such as silicone or gum may be used for the cover when traction is required. The conveyor belt is preferably an air permeable support, more preferably a non-woven fabric, most preferably a felt or polyester felt.

Preferably, the conveyor belt comprises a glass fabric or the frame is a glass fabric, and more preferably, the glass fabric as the frame has a coating comprising a thermoplastic polymer resin on top, and most preferably, the glass fabric has a coating on top comprising: polyethylene terephthalate (PET), Polyamide (PA), High Density Polyethylene (HDPE), Polytetrafluoroethylene (PTFE), Polyoxymethylene (POM), Polyurethane (PU) and/or Polyaryletherketone (PAEK).

Preferably, the conveyor belt is an endless conveyor belt.

Most conveyor belts are wrapped around at least two pulleys or around a pulley and a knife to form a conveyor belt system. The pulleys in the conveyor belt system are preferably transmission drums for rotating the conveyor belt on its pulleys or knives. In a preferred embodiment, the conveyor belt system comprises a fixed or rolling edge at the output position. The radius of the rolling edge is preferably between 2 and 20 mm in order to have a good transfer on the temporary carrier.

The conveyor belt preferably comprises a plurality of perforations and/or cavities for holding one or more positioning devices. And the positioning means have an extension fitting said perforation or cavity. A plurality of perforations and/or cavities are preferably arranged on the carrying surface in a grid pattern to create different alignment schemes according to the dimensions of the leathers to be applied on the conveyor belt and subsequently aligned on the temporary support to be printed by the ink-jet technique.

Image of a person

There is no practical limit to the type of image that can be ink-jet printed on leather using one or more pigmented ink-jet inks. The decoration may consist of a single color, or it may also comprise a plurality of colors, such as black, white, cyan, magenta, yellow, red, orange, violet, blue, green and brown.

A set of images may be printed according to a layout. The layout may be determined based on the position of a set of positioning devices of the conveyor belt used in the present invention. In a preferred embodiment, the positioning device can be changed, removed from the conveyor belt or added to the conveyor belt, so the layout is changeable. In a preferred embodiment, the layout is additionally determined by the shape and/or size of the leather applied on the conveyor belt. Thus, the shape and/or size is determined and also delivered to the inkjet printing system.

Base coat

The basecoat applied over the crust provides a level of image quality commensurate with the luxurious appearance of the leather, since the low viscosity of the inkjet inks causes them to quickly penetrate into the leather, resulting in reduced image quality.

The primer layer may be applied as a single layer, or may be applied as multiple layers. The multiple layers may even have different compositions to improve properties such as adhesion or flexibility.

The base coat preferably comprises a polyurethane based polymer or copolymer as this has been found to improve the flexibility of the printed leather. Since polyamides have been found to improve compatibility with crust leather and improve the strength of the base coat, the base coat preferably further comprises a polyamide polymer or copolymer.

The base coat is preferably applied by spray coating, but may be applied by any known coating technique, such as knife coating, extrusion coating, slide hopper coating, and curtain coating. It may be applied before the semitanning leather is attached to the temporary support, or it may also be applied when the semitanning leather has been attached to the temporary support.

The base coat may be transparent, but is preferably an opaque base coat. The primer layer may be a white primer layer to enhance color vividness of the inkjet-printed image, but preferably, the primer layer has a color similar to the color of the dermis and the color of the particles. Any desired color may be selected for the dermis or the particles and the base coat, for example, red, green, brown, black, blue.

Pigmented inkjet inks

The inkjet printed one or more pigmented inkjet inks may be selected from the group consisting of aqueous pigmented inkjet inks, solvent-based pigmented inkjet inks, and radiation curable pigmented inkjet inks. However, the one or more pigmented inkjet inks are preferably one or more radiation curable inkjet inks, most preferably one or more UV curable inkjet inks.

The one or more pigmented inkjet inks preferably comprise organic colour pigments, since organic colour pigments allow to obtain a high colour gamut on natural leather. Carbon black and titanium dioxide are inorganic pigments that may be advantageously used in the present invention to constitute black and white ink-jet inks, respectively.

The preparation of pigmented UV curable inkjet inks is well known to the skilled person. Preferred preparation processes are disclosed in paragraphs [0076] to [0085] of WO 2011/069943 (AGFA).

Top coat

A top coat may be applied over the decorative image and the base coat to enhance the scratch and mar resistance of the decorative image.

The top coat may be applied as a single layer, or may be applied as multiple layers. The multiple layers may even have different compositions to improve properties such as scratch resistance.

The protective top coat may have the same or similar composition as the base coat. The protective top coat is usually slightly optimized for leather applications. For example, in contrast to leather shoes, flexibility has no important effect on leather book covers. Thus, the protective top coat for the cover can be optimized for scratch resistance.

The top coat preferably comprises a cross-linking agent and a polymer or copolymer based on polyurethane and/or polyamide.

Since polyurethane-based polymers or copolymers are beneficial for the flexibility of the printed leather, the top coat preferably comprises polyurethane-based polymers or copolymers. If improved scratch resistance is desired, polyamide polymers which have been found to have high compatibility with polyurethane adhesives are preferably included.

The top coat is preferably applied by spraying, but may be applied by the same coating techniques as described above for the base coat.

The top coat is most preferably a transparent top coat, but may be a translucent top coat. By having a transparent top coat, the ink jet printed image is clearly visible through the top coat. By using a translucent top coat, a special aesthetic effect is created.

Matting agents may be included if inkjet printed leather requires a matte top surface. Any suitable matting agent may be used. Preferred matting agents include silica.

Ink jet printing system

One or more pigmented inkjet inks are jetted by one or more print heads that eject small droplets through a nozzle in a controlled manner onto the natural leather moving relative to the print head.

A preferred print head for an inkjet printing system is a piezoelectric head. Piezoelectric inkjet printing is based on the movement of a piezoelectric ceramic transducer when a voltage is applied. Application of a voltage changes the shape of the piezoelectric ceramic transducer in the printhead, thereby forming a void, which is subsequently filled with an inkjet ink or liquid. When the voltage is removed again, the ceramic expands to its original shape, ejecting a drop of ink from the print head.

A preferred piezoelectric print head is a so-called through-flow piezoelectric drop-on-demand ink jet print head. By using a through-flow print head, the reliability is improved and thus a more efficient and economical process for manufacturing high quality decorated natural leather articles is obtained. Such a print head is available, for example, as the CF1ou print head at TOSHIBA TEC.

However, the inkjet printing method of the present invention is not limited to piezoelectric inkjet printing. Other inkjet print heads may be used and include various types, such as continuous type print heads.

The inkjet print head is typically scanned back and forth across the moving leather surface in the transverse direction, which is referred to as a multi-pass print mode. Sometimes the inkjet print head does not print on the way back. Bi-directional printing is preferred to obtain high area throughput.

Another preferred printing method is by a "single pass printing process" which can be carried out by using a page wide inkjet print head or a plurality of staggered inkjet print heads that cover the entire width of the leather surface. In a single pass printing process, the inkjet print head is typically held stationary and the ink receiving leather surface is transported beneath the inkjet print head.

An advantage of using a multi-pass printing mode is that the liquid UV curable inkjet ink is cured in a continuous pass rather than in a single pass, which would require a curing device with high UV output. For multi-pass printing, the printhead life is also longer. While in single pass printing one side shooter (side shooter) is sufficient to replace the entire print head, in multi-pass printing multiple side shooters, and even failure, can be tolerated. Moreover, the cost of multi-pass printers is generally much lower, especially for large format crust leather.

Curing device

If an aqueous or solvent-based pigmented inkjet ink is used, some curing means for evaporating the water and organic solvent is required. Suitable curing means include heat radiating means such as a hot air dryer, an oven or an infrared light source such as an infrared laser, one or more infrared laser diodes or infrared LEDs.

If a UV curable pigmented inkjet ink is used, curing is usually performed by ultraviolet radiation alone. If the so-called hybrid UV-curable pigmented inkjet ink also comprises water or an organic solvent, the curing device also preferably further comprises a curing device for aqueous or solvent-based pigmented inkjet inks.

In inkjet printing, a curing device may be arranged in conjunction with the print head of the inkjet printer and travel with it so that the inkjet ink is exposed to curable radiation immediately after being jetted.

Any ultraviolet light source, as long as part of the emitted light is absorbed by the photoinitiator or photoinitiator system, may be used as the radiation source, such as high or low pressure mercury lamps, cold cathode tubes, black light, ultraviolet LEDs, ultraviolet lasers, and flash lamps.

Examples

The figures from 2 to 4 show some preferred embodiments of the invention. The crust leather (700) is applied to the conveyor belt (100) against the positioning device (105). The aligned semi-nitro-leather is laminated in an aligned manner on the temporary carrier (200) by conveying (shown as an arcuate arrow in a pulley) and moving the temporary carrier (200) containing the adhesive layer (205) as a top layer. The laminated and aligned crust leather is then flattened with a flattener (300) to avoid collision with the inkjet print head (400) when printing with the print head. The inkjet printed image is then cured by a curing device (500).

Fig. 2 shows the conveyor belt lying horizontally. Fig. 3 shows a tilted conveyor belt (at an angle). Fig. 4 shows a particular conveyor system, in which a fixed knife edge is shown in the output position.

REFERENCE SIGNS LIST

100 conveyor belt

105 positioning device

200 temporary carrier

205 adhesive layer

300 flattener

400 ink jet print head

500 solidification equipment

700 parts of leather.