EP2820160A1

EP2820160A1 - Coating composition for stingray leather, tanning and finishing processes and finished stingray leather

Info

Publication number: EP2820160A1
Application number: EP12707737.8A
Authority: EP
Inventors: Luis AMPUERO
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-02-29
Filing date: 2012-02-29
Publication date: 2015-01-07
Also published as: WO2013127455A1

Abstract

The present invention relates to a coating composition for stingray leather, the use thereof. The present invention also relates to tanning and finishing processes comprising coating stingray leather with the coating composition of the invention. The present invention further relates to a coated finished stingray leather.

Description

COATING COMPOSITION FOR STINGRAY LEATHER, TANNING AND FINISHING PROCESSES AND FINISHED STINGRAY LEATHER

FIELD OF INVENTION The present invention relates to a coating composition for stingray leather, tanning and finishing processes comprising coating stingray leather with the coating composition of the invention and coated finished stingray leather. Especially, the present invention relates to a surface finishing coating for galuchat leather, also called shagreen.

BACKGROUND OF INVENTION Shagreen is a type of leather made from rays' skin, preferably stingray skin. It presents the particularity to have a granular surface due to the presence of calcified papillae. Indeed, the skin of rays is naturally covered by placoid scales that are flattened teeth and therefore made of dentin. These dermal denticles cover the skin with round, closely set, calcified papillae whose size is chiefly dependent on the species of rays. The skin of sharks is also covered by placoid scales. However, in sharks, dermal denticles are in the form of hooks and made of silica.

When polished, shagreen makes appear planar sections of dermal denticles. Polished shagreen gives to see shining partitioned cells (polished dermal denticles) surrounded by valleys (tanned skin beneath). Shagreen may be dyed in different colors. The use of shagreen was first developed in Asia where armors were covered with this leather. Shagreen was introduced in Europe at 16^th century and became very prized in royal courts and aristocracy at 18^th century. The French leatherworker Jean-Claude Galluchat developed a new manner to work-up ray and shark skins and created beautiful pieces covered with shagreen such as boxes, small cases, hilts and scabbards of swords and daggers. Jean-Claude Galluchat was the leatherworker of the French court of Louis XV and the Marquise de Pompadour particularly appreciated his work. Fame of Jean Claude Galluchat resulted in giving his name to this type of leather. A time forgotten, shagreen came back to fashion at the beginning of the 20 century during the art deco period. It is nowadays used essentially in luxury industry of furniture and leather goods.

Leather production, whatever the origin of the skin, comprises the following main steps:

- pre-treatment of the raw skin comprising:

o salting the skin for preservation purposes ,

o soaking to rehydrate and clean the skins,

o liming the skin to remove remaining flesh and fat,

o deliming, bating and bleaching the skin,

- tanning to transform the skin into leather by treatment with tanning agents, resulting in irreversible cross-linking of collagen fibers for stabilization of the skin,

post-treatment of the leather comprising:

o a wet-end processing comprising steps of retanning, dyeing and fat liquoring,

o a pre-finishing or dressing step comprising drying, buffing and staking the leather,

o a finishing step, comprising essentially coating operations.

Above steps have to be closely adapted depending on the origin of the skin and of the intended use of the finished leather. In the case of shagreen processing, the presence of the dermal denticles at the surface of the ray's skin is a further concern in optimizing the processing and requires further specific treatments to magnify denticles. Especially, the processing of the pearl-side is very difficult.

There are very few information in the art relative to specific tanning processes and leather post-treatment of rays skin to obtain shagreen. Tanning methods for fish skin are described; however, they are dedicated to common fishes with scales and not to fishes with dermal denticles, such as rays. Therefore, tanning methods generally comprise a descaling step or a scales dissolution step (see for example US4,755,186 or EPl 605 066). Some previous art also describes the removing or partial dissolution of denticles from rays or sharks skin (see for example GB 191 203 481 or GB 331 241). On the contrary, during shagreen manufacturing, denticles should be carefully kept and magnified as they are the specific characteristic of this kind of leather.

Coating compositions for use in finishing step of leather coming from mammals, such as cows, sheep, goats or pigs, have been described. For example, US patent US7, 378,032 describes a coating composition for mammal leather, or artificial leather, comprising curable fluorine-containing resin and silicon oil to give soft feeling and abrasive resistance to leather. However, this coating composition is dedicated to mammal leather or artificial leather and is not adapted to shagreen finishing that is a leather coming from a very specific fish. Other coatings are used to provide a particular surface effect on leathers, such coatings being prefabricated on a hot substrate having a structure corresponding to a surface effect, such as in patent US6,177,198 or in patent application US2007/082176.

However, in the Applicant knowledge, there are no specific description of tanning and post-treatments for shagreen manufacturing, especially wet-end, pre-finishing and finishing steps of shagreen processing.

Moreover, as shagreen is mainly used in luxury industry, an ever-increasing quality is required to satisfy customers. Good quality leather should pass mechanical tests measuring parameters such as, tensile and tear strength. In addition to these basic mechanical properties, very high quality shagreen would be characterized by particular softness and flexibility, by having subtle dyeing and an overall specific appearance that may be appreciated by a leather specialist. Softness and flexibility may be quantified by physical tests. Overall aspect and quality may also be quantitatively estimated by "haptic" tests or qualitatively estimated by perception tests conducted either by leather specialists or involving consumers. Due to chemicals and methods employed today in ray's skin processing, shagreen commercially available does not meet the high quality leather requirements. Especially, flexibility and softness of existing shagreen are not satisfying. These parameters may be qualitatively and quantitatively appreciated. Shagreen is often too rigid and bony, due to the poor tanning methods that are currently used, mainly to keep the costs as low as possible. Moreover, pigmented coatings used today often mask valleys between dentine beads, as well as overall patterns of the surface. The natural beauty of shagreen is therefore lost. Another quality limiting parameter is the finishing treatments that are used, especially base and top coats, that often result in a plastic-like rendering far away from expected natural feel.

Therefore, there is a need for new shagreen upgraded processing that result in high quality leather, especially with high softness and flexibility and a natural appearance.

It is admitted that the production of quality leather, whatever the origin of the skins, depends upon the proper selection of raw material, chemicals, auxiliaries, formulation and judicious adjustments and manipulations in the manufacturing process and finishing operations (Ramabrahmam et al., Leather International Magazin, 2003, 10). These selections should be adapted to the kind of skin that is treated and require numerous tests and comparative samples to obtain an overall process leading to high quality leather. In the specific case of stingray leather, the presence of dermal denticles, is a further concern that has to be taken into consideration in the development of methods to obtain high quality leather.

The Applicant found that using a specific coating composition, together with an optimized pre- and/or post-treatment of stingray leather, gives access to shagreen with a quality never reached to date. SUMMARY

This invention thus relates to the process for manufacturing a finished stingray leather comprising applying a coating composition comprising:

a vehicle comprising an organic solvent and/or water,

a film forming component, and

at least one mean for coloring the composition

for coating a stingray leather.

In one embodiment , the organic solvent is selected from alcohol such as ethanol, diacetone alcohol, isopropanol or n-butanol; ketones, acetone, dimethylformamide, ethers, alkanes such as pentane, cyclopentane, hexane, toluene, heptane or cyclohexane; cyclic ethers such as tetrahydrofuran or 1,4-dioxane, glycol ethers, ethylene glycol monobutyl ether acetate, cellosolve acetate, methyl cellosolve acetate, butyl cellosolve, ethyl cellosolve, phenylated solvents such as xylene; esters of acetic acid such as butyl acetate, methyl acetate, pentyl acetate, propyl acetate or ethyl acetate; chlorinated hydrocarbons such as methylene chloride, chloroform or methylchloroform; or a mixtures thereof.

In one embodiment, the film forming component comprises a film forming polymer, a film forming resin or a mixture thereof. In one embodiment, the film forming polymer is selected from polyurethane, polyurethane copolymers, cellulose acetate, cellulose acetate butyrate, ethyl cellulose, nitrocellulose, vinyl polymers, vinyl acetate polymers or copolymers, vinyl acrylates, methacrylate polymers, acrylate polymers, styrenated acrylic polymers, acrylic-urethane polymers, olefin polymers, olefin copolymers or mixtures thereof. In one embodiment, the film forming resin is selected from drying or non-drying alkyd resin, polyvinyl resins such as polyvinyl acetate, polyester resins, epoxy resins, acrylic polymers and copolymers, maleic modified glycerol esters of rosin, toluene sulfonamide/epoxy resins, tosylamide resin, arylsulfonamide formaldehyde resins or mixtures thereof. In one embodiment, the means for coloring is a pigment, a colorant or a mixture thereof.

In one embodiment; the pigment is selected from natural mineral mica, said mica being covered or not with a layer of metal oxide; silicon dioxide platelets, calcium aluminum borosilicates, bismuth oxichloride or mixture thereof.

In one embodiment the coating composition is applied on the pearl-side of a stingray leather.

In one embodiment, the process of the invention further comprises a preliminary step of polishing the pearl- side of a stingray leather. In one embodiment, the process of the invention further comprises coating the pearl- side of stingray leather with another coating composition. Preferably, the process of the invention comprises applying one, two or three layers of a coating composition, at least one layer thereof being a layer of the coating composition as described herein. In one embodiment, the process of the invention further comprises a cleaning step between the step of polishing and the coating step.

In one embodiment, the process of the invention further comprises a step of buffing the flesh-side of a stingray leather, preferably prior to polishing the pearl-side of the stingray leather. In one embodiment, the process of the invention is performed on a pre-finished stingray leather, said pre-finished stingray leather being obtained by a process comprising the following steps:

- a pre-treatment step comprising:

removing flesh of a stingray to obtain the raw stingray skin, and/or soaking the skin to clean it, and/or

liming the skin to remove remaining flesh and fat, and/or

deliming and/or bating the skin, and/or

bleaching the skin,

leading to a pre-treated stingray skin,

- a tanning step comprising treating the pre-treated stingray skin by pickling and with tanning agents, said tanning agents comprising chrome or being chrome free tanning agents,

leading to tanned stingray leather,

- a wet-end post-treatment comprising retanning, dyeing and/or fat liquoring the tanned stingray leather,

leading to a wet-end post-treated stingray leather, and

- a pre-finishing post-treatment comprising setting out, drying, stacking and buffing wet-end post-treated stingray leather,

leading to pre-finished stingray leather. The present invention also relates to stingray leather obtainable by the process of the invention.

In one embodiment, the stingray leather of the invention forms parts of leather accessories such as a purse, a document holder, a wallet, a coin case, a belt, a strap, a watch band, a book cover, a smartphone cover, a mobile cover, a numeric tablet cover, a computer cover, a bag, an eyewear, a scientific instrument, a pen, a box, a footwear, clothes, a jacket; a furniture item for automotive, plane and/or boats interiors, walls, doors, panels, ceiling for interior decoration or design.

DEFINITIONS

In the present invention, the following terms have the following meanings:

"stingray leather" refers to a leather made from stingray skins,

"raw stingray skin" refers to the stingray skin that has just been removed from the stingray carcass.

- "pre-finished stingray leather" refers to a stingray leather that have been post- treated after tanning by wet-end processes and pre-finishing processes,

"finished stingray leather" refers to a stingray leather that have been post-treated after tanning by wet-end processes, pre-finishing and finishing processes,

"tanning" refers to the transformation of a skin into leather by treatment with tanning agents, resulting in irreversible cross-linking of collagen fibers for stabilization of the skin.

"wet-end process" refers to the post-treatment of a leather after tanning comprising steps of retanning, dyeing and/or fat-liquoring.

"pre-finishing process" refers to the post-treatment of a leather after tanning comprising steps of drying, buffing, and/or stacking. In the case of stingray leather processing, "pre-finishing process" refers to the post-treatment of a leather after tanning comprising steps of drying, buffing, polishing and/or stacking,

"finishing process" refers to the post-treatment of a leather after tanning and wet- end processing comprising coating. "coating composition" refers to a composition that forms a covering film when applied on a substrate.

"means for coloring" refers to substances that give a specific color to the substrate on which they are applied.

"pigment" refers to a mean for coloring that is insoluble and made of fine colored particles.

"micropigment" refers to pigments with a particle size ranging from 0.1 μιη to 500 μιη, preferably from 5 μιη to 100 μιη, more preferably from 10 μιη to 60 μιη.

"colorant" refers to a mean for coloring that is soluble in a vehicle and that is absorbed and/or chemically linked by the substrate to be colored. The terms "dye" and "colorant" may be used interchangeably.

"vehicle" refers to a substance that brings the product of interest in a composition, especially a substance able to dissolve the product of interest. In the present invention, the vehicle may comprise water and/or one or more organic solvent different from water.

"film forming component" refers to a component that, when encompassed into a composition, allows said composition to form a covering film when applied on a surface.

"coating composition" refers to a composition that forms a coating when applied on a surface.

"about" preceding a figure means plus or less 10% of the value of said figure.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a scheme showing alternative routes (1A, IB and 1C) of manufacturing finished stingray leather from pre-finished stingray leather by the process of the invention.

Figure 2 is a scheme showing an overall process of manufacturing pre-finished stingray leather from raw stingray skin. DETAILED DESCRIPTION

Coating composition

This invention relates to a composition for use in coating leather, especially ray leather, more preferably stingray leather. In a preferred embodiment, stingray leather has dentin pearls at its surface.

Especially, this invention relates to a coating composition for use in coating pre-finished stingray leather in a finishing step.

According to an embodiment, the composition of the present invention comprises:

a vehicle comprising an organic solvent and/or water,

a film forming component, and

at least one mean for coloring the composition.

In an embodiment, the composition of the present invention is able to form a covering film on leather, preferably on ray leather, more preferably on stingray leather.

In a first embodiment, the composition of the present invention is able to form a thin film, preferably the thickness of the film is less than 0.3 mm, more preferably the thickness of the film is ranging from 0.001 mm to 0.1 mm, more preferably from 0.005 mm to 0.09 mm, more preferably from 0.02 mm to 0.08 mm, even more preferably from 0.01 mm to 0.06 mm. In an alternative embodiment, the thickness of the film is ranging from 0.08 mm to 0.3 mm. In a second embodiment, the composition of the present invention is able to form a medium film, preferably the thickness of the film is ranging from 0.3 mm to 2 mm, preferably from 0.3 mm to 1 mm, more preferably from 0.3 mm to 0.6 mm. In a third embodiment, the composition of the present invention is able to form a thick film, preferably the thickness of the film is more than 2 mm, preferably the thickness of the film is ranging from 2 mm to 7 mm. In an embodiment, the thickness of the film may be measured by ultrasonic technique, with for example a PosiTector 200 apparatus from TQC.

The composition of the invention may be a solution, a dispersion or an emulsion. According to one embodiment, the vehicle comprises an organic solvent, preferably a solvent such as alcohol such as ethanol, diacetone alcohol, isopropanol or n-butanol; ketones, acetone, dimethylformamide, ethers, alkanes such as pentane, cyclopentane, hexane, toluene, heptane or cyclohexane; cyclic ethers such as tetrahydrofuran or 1,4- dioxane, glycol ethers, ethylene glycol monobutyl ether acetate, cellosolve acetate, methyl cellosolve acetate, butyl cellosolve, ethyl cellosolve, phenylated solvents such as xylene; esters of acetic acid such as butyl acetate, methyl acetate, pentyl acetate, propyl acetate or ethyl acetate; chlorinated hydrocarbons such as methylene chloride, chloroform or methylchloroform. The aforementioned organic solvents can be used alone or in mixtures thereof.

According to another embodiment, the vehicle comprises water.

According to one embodiment, the composition of the invention is an evaporative finish. In this embodiment, when the composition is applied on leather, the vehicle of the composition evaporates. As a consequence, the composition dries and forms a hard film.

According to another embodiment, the composition of the invention is a reactive finish. In this embodiment, when the composition is applied on leather, the vehicle of the composition evaporates and the components of the compositions undergo chemical reactions. According to one embodiment, the film forming component comprises a film forming polymer, a film forming resin or a mixture thereof.

In one embodiment, the film forming component comprises a film forming polymer such as polyurethane, polyurethane copolymers, cellulose acetate, cellulose acetate butyrate, ethyl cellulose, nitrocellulose, vinyl polymers, vinyl acetate polymers or copolymers, vinyl acrylates, methacrylate polymers, acrylate polymers, styrenated acrylic polymers, acrylic-urethane polymers, olefin polymers, olefin copolymers or mixtures thereof. In one embodiment, the film forming component comprises a film forming resin such as drying or non-drying alkyd resin, polyvinyl resins such as polyvinyl acetate, polyester resins, epoxy resins, acrylic polymers and copolymers, maleic modified glycerol esters of rosin, toluene sulfonamide/epoxy resins, tosylamide resin, aryl sulfonamide formaldehyde resins or mixtures thereof.

According to one embodiment, the film forming component may further comprise UV light absorbers, photo initiator agents, polymerization initiators, curing agents (also called cross -linkers), curing accelerators or a mixture thereof. UV light absorbers may be for example ectocrylene or benzophenone- 1. Curing agents may be for example an isocyanate compound, an amino resin, an acid anhydride, a polysilane compound, a polyepoxy compound or an isocyanate group-containing silane compound. In one specific embodiment, the film forming component comprises polyurethane as film forming polymer and further comprises an isocyanate compound as curing agent. According to one embodiment, curing agents are present in the composition of the present invention in amounts ranging from 0.1% to 10%, preferably from 1% to 5%, more preferably from 1% to 3 % in weight of the total weight of the composition. Curing accelerator may be for example a tin compound, an acidic phosphate ester, a reaction product between an acidic phosphate ester and an amine, a saturated or unsaturated polycarboxylic acid or anhydride thereof, an organic titanate compound, an amine compound, a lead octoate, or a combination thereof. According to one embodiment, curing accelerators are present in the composition of the present invention in amounts ranging from 0.1% to 10%, preferably from 1% to 8%, more preferably from 2% to 5 % by weight of the total weight of the composition.

According to one embodiment, the film forming component is present in the composition of the present invention in amounts ranging from 5% to 98% by weight of the total weight of the composition. According to a first embodiment, the amount of film forming component is ranging from 5% to 40% by weight of the total weight of the composition, preferably from 8 % to 30 %, more preferably from 10% to 20%. According to a second embodiment, the amount of film forming component is ranging from 40% to 98% by weight of the total weight of the composition, preferably from 70 % to 95 %, more preferably from 90% to 94%.

According to a first embodiment, the at least one means for coloring may be a pigment, a colorant or a mixture thereof. According to a first embodiment, the at least one mean for coloring is a pigment.

According to an embodiment, pigments used in the composition of the invention may be based on natural mineral mica, covered or not with a layer of metal oxide. The metal oxide may be for example titanium oxide. This kind of pigments may have a glittering effect depending of the pigment particle size. According to another embodiment, pigments used in the composition of the invention may be based on silicon dioxide platelets (silicate oxide). This kind of pigment offers color gradation depending on the angle of observation. According to another embodiment, pigments used in the composition of the invention may be based on calcium aluminum borosilicates, resulting in brilliance and sparkle. In this embodiment, pigment particles may further be coated with metal oxide. According to another embodiment, pigments used in the composition of the invention may be based on bismuth oxichloride leading to metallic luster aspect.

By way of example only, suitable pigments may be obtained from Rhodia-Pigments Ceramics and Additives, Clariant-Pigments and Additives, BASF AG, Bayer Corporation Coating and Colorants, Sun Chemical Corp. Colors Group, CIBA or Merk KG. By way of example only, suitable pigments may be "effect pigments" from BASF, preferably pigments selected from Dynacolor®, Lumina®, Magna Pearl®, Firemist®, Mearlite®, Graphitan ®, Glacier™, Metasheen® or Paliocrom®.

In one embodiment, the particle size of pigments is ranging from 0.001 μιη to 500 μιη. In an embodiment, the particle size of pigments is ranging from 0.001 μιη to 10 μιη, preferably from 0.01 μιη to 5 μιη, more preferably from 0.02 μιη to 8 μιη, more preferably from 0.1 μιη to 5 μιη. In one embodiment, when the particle size of pigments is up to 8 μπι, pigments are well dispersed the composition wherein they are encompassed. In one embodiment, when the particle size of pigments is up to 3 μιη, pigments are excellently dispersed the composition wherein they are encompassed. In one embodiment, when the particle size of pigments is less than 1 μιη, pigments are ultra finely dispersed in the composition wherein they are encompassed. In another embodiment, the particle size of pigments is ranging from 10 μιη to 500 μιη; preferably from 100 μιη to 300 μιη, more preferably from 150 μιη to 250 μιη.

According to a preferred embodiment, pigments used in the composition of the invention are micropigments, preferably micro effect pigments.

According to an embodiment, above pigments may be used alone or in combination together or in combination with further pigments.

According to a second embodiment, the at least one mean for pigmenting is a colorant, preferably an organic colorant, more preferably an organic coloring polymer.

According to one embodiment, the mean for pigmenting is present in the composition of the present invention in amounts up to 20% by weight of the total weight of the composition, preferably up to 10%, preferably ranging from 0.1% to 10%, more preferably from 1 to 9 %, even more preferably from 2 to 8 %.

According to one embodiment, the composition of the invention further comprises glittering agents such as for example aluminum particles. Glittering effects may be obtained by using for example Poly*Flake or Holo*Gram products of Glitterex. According to one embodiment, the composition of the invention further comprises additives such as suspending or dispersing agents, antifoaming agents, anti-gelling agents, anti-oxydation agents, thickening agents, moisturizers, stabilizers, handle modifiers, plasticizers, glittering agents, fragrances. These components are well known in the art of film forming compositions. Suspending agents may be for example colloidal clays, montmoriUonite clays, especially stearalkonium hectorite, stearalkonium bentonite, fumed silica or mixtures thereof. Plasticizers may be for example tricresyl phosphate, dibutyl tartrate, benzyl benzoate, tributyl phosphate, butyl acetyl ricinoleate, butyl glycolate, butyl stearate, triphenyl phosphate, triethyl citrate, camphor, castor oil, esters of citric, stearate, phalic, oleic, phosphate, butyric and benzoic acid, glyceryl triacetate and glyceryl triproprionate, 2,2,4-trimethyl-l,3-pentandiiol diisobutyrate or mixtures thereof.

According to one embodiment, the curing of the composition of the present invention may be induced by moisture, pressure or UV lighting. In a specific embodiment, the composition of the invention comprises a photoinitiator agent when cured under UV lighting.

The composition of the invention presents the advantage to be a non-yellowing system. The composition of the present invention is therefore suitable for white and light color substrates.

Leather post-treatment process

The invention also relates to a process for post-treating stingray leather after tanning. The process of the present invention leads to finished stingray leather. Unless otherwise specified, all steps of the process may be performed in any order. According to one embodiment the process of the invention is performed on pre-finished stingray leather. In this embodiment the process of the invention is a finishing process.

In the following, it should be understood that the "outer surface" of the stingray leather stands for the side of the leather on which dentine pearls are visible, also called "pearl- side". The "inner surface" of the stingray leather stands for the side of the skin that was in contact with flesh, also called "flesh-side"

According to an embodiment, the finishing process of the invention comprises the following steps (figure 1A):

polishing the pearl- side of a pre-finished stingray leather, and

coating the polished pearl-side at least once with the coating composition of the invention,

optionally further coating the polished pearl-side at least once with another coating composition. According to an embodiment, all the steps of the process of the present invention are validated by quality control comprising perception tests by leather specialists to evaluate smoothness, softness, flexure, and uniformity of the leather surface. Each step of the process may be conducted twice or more time depending of the result of the quality control.

According to one embodiment, polishing of the pearl-side is performed using a polishing machine. In one embodiment, the pearl-side of stingray leather is polished using sandpaper. In another embodiment, the pearl-side of stingray leather is polished using a polishing stone, felts, rollers and/or wax stone. According to one embodiment, polishing is performed by at least one passage of the pre-finished stingray leather through a polishing machine. According to one embodiment, polishing may be performed by a plurality of passage in a polishing machine. In a specific embodiment, the polishing machine is equipped with sandpaper and polishing is performed by a plurality of passage in the polishing machine using sequentially different abrasive grading of sandpaper. According to a specific embodiment, the number of passage in the polishing machine is ranging from 1 to 10 times, preferably from 1 to 8, more preferably from 1 to 4.

In one embodiment, the quality of the polishing is evaluated by quality control between passages in the polishing machine. The number of further passages in the polishing machine and the choice of the grade of sandpaper are determined after quality control. The choice of the grade of sandpaper may depend from the intended use of the leather and whether the leather was pre -polished or not.

The polishing step allows making shine dentin pearls and controlling the leveling of pearls to render them more or less flat depending of the desired effect. In one embodiment, the process of the invention may comprise a further step of cleaning after polishing of the pearl- side (figure IB). Cleaning may be performed by dedusting or by solvent cleaning. Dedusting may be performed in a dedusting machine comprising a vacuum pump and a moving belt. According to one embodiment, the coating composition is applied by spraying the coating composition of the pearl-side of the leather. The spraying may be performed using any type of spray gun or a spraying machine known to be suitable by the one skilled in the art. According to another embodiment, the coating composition is applied by scraping, casting, padding or using a brush or a roller coating machine or other type of coating machines.

According to one embodiment, the coating composition is applied once or more time, for example 1, 2, 3, 4, 5 or more times. The choice of the number of applications of the coating composition depends on the quality control that is conducted after application and on the final appearance looked for.

According to one embodiment, the coating composition of the invention is applied on the pearl- side of the leather to form a covering film.

According to a first embodiment, the coating composition of the invention is applied on the pearl-side of the leather to form a thin film, said film having a thickness of less than 0.1 mm, more preferably the thickness of the film is ranging from 0.001 mm to 0.3 mm, more preferably from 0.005 mm to 0.09 mm, more preferably from 0.02 mm to 0.08 mm, even more preferably from 0.01 mm to 0.06 mm. In an alternative embodiment, the thickness of the film is ranging from 0.08 mm to 0.3 mm According to a second embodiment, the coating composition of the invention is applied on the pearl- side of the leather to form a medium film, said film having a ranging from 0.3 mm to 2 mm, preferably from 0.3 mm to 1 mm, more preferably from 0.3 mm to 0.6 mm.

According to a third embodiment, the coating composition of the invention is applied on the pearl-side of the leather to form a thick film, said film having thickness of more than 2 mm, preferably the thickness of the film is ranging from 2 mm to 10 mm. In one embodiment, the process of the invention may comprise a further step of coating comprising the application of a further coating composition on the peal-side of the stingray leather (figure IB). In this embodiment, the further coating composition may be a composition of the present invention or another coating composition known by the one skilled in the art of leather finishing. In one embodiment, the further coating composition may be a top-coat composition. In the case of a top-coat, the composition may comprise handle modifiers such as Lacquer Additive C of TOA Resin Corporation Ltd Japan, glittering agents such as Poly*Flake of Glitterex, means for coloring or a mixture thereof. The application of a top-coat may contribute to impart protection to the leather, especially rendering it resistant to weather and environment. In an embodiment, the top-coat is transparent. In another embodiment, the top-coat is colored.

According to one embodiment, the applied coating composition is let drying and/or curing before any further operation.

Curing of the coating may occur spontaneously after a given time or being activated. Curing activation may be performed for example by UV lighting, by pressure application or by moistening. In another embodiment, curing activation is performed by curing agents present in the coating composition. According to one embodiment, curing may occur for a period ranging from 1 to 24 hours, preferably from 3 to 15 hours, more preferably from 6 to 12 hours. According to one embodiment, curing may occur at a temperature ranging from 10°C to 60°C, preferably from 20°C to 50°C, more preferably from 30°C to 45 °C. In a specific embodiment, curing occurs at ambient temperature.

Drying of the coating may be performed by letting coated leather at ambient temperature, by using a drying tunnel, an air drying oven, a toggle drier or any method known by the one skilled in the art. According to one embodiment, drying may occur for a period ranging fromlO minutes to 24 hours, preferably from 30 minutes to 10 hours. In a specific embodiment, drying occurs for a period ranging from 10 minutes to 2 hours, preferably from 30 minutes to 1 hour. In another specific embodiment, drying occurs for a period of time ranging from 1 to 24 hours, preferably from 5 to 15 hours, more preferably from 8 to 12 hours. According to one embodiment, drying may occur at a temperature ranging from 10°C to 90°C, more preferably from 20°C to 80°C, more preferably from 30°C to 70 °C. In a specific embodiment, curing occurs at ambient temperature.

In one embodiment, drying is performed in two steps: (i) a first step comprising drying for a period of time ranging from 1 minute to 30 minutes, preferably from 5 minutes to 10 minutes, preferably about 5 minutes and at a temperature ranging from 80°C to 110°C, preferably from 90°C to 100°C; followed by (ii) a second step comprising drying for a period of time ranging from 5 hours to 24 hours, preferably from 6 hours to 12 hours, preferably about one night and at ambient temperature.

In one embodiment, the process of the invention comprises a further step of plating after coating application. Plating may be performed at a temperature ranging from 50 to 120°C, preferably from 60 to 110°C, more preferably from 80 to 100°C. According to one embodiment plating is performed using a plating machine, preferably a hydraulic press machine.

In another embodiment, the process of the invention further comprises a preliminary step of buffing the flesh-side of the pre-finished stingray leather, said buffing step being performed before the polishing step of the process of the invention (figure 1C). In this embodiment the flesh-side is buffed to reduce thickness, to remove unwanted fibers and/or smoothen up the inner surface of leather. This buffing may be performed using sandpaper. Different grades of sandpaper may be used and a plurality of passages in the buffing machine may be conducted. The number of passage in the buffing machine and the grade of sandpaper to be used are determined according to quality control results and desire effect needed.

According to one embodiment, when the process of the invention comprises a preliminary buffing step, it may further comprise a cleaning step, preferably a dedusting step, before the pearl-side polishing (figure 1C).

According to an embodiment, the process of the invention is performed on a pre- finished stingray leather, said pre-finished stingray leather being obtained by a process comprising the following steps (see figure 2): a pre-treatment step comprising:

o removing flesh of a stingray to obtain the raw stingray skin, and/or o soaking the skin to clean it, and/or

o liming the skin to remove remaining flesh and fat, and/or o deliming and/ or bating the skin, and/or

o bleaching the skin,

leading to a pre-treated stingray skin,

a tanning step comprising treating the pre-treated stingray skin by pickling and with tanning agents, said tanning agents comprising chrome or being chrome free tanning agents,

leading to tanned stingray leather,

a wet-end post-treatment comprising retanning, dyeing and/or fat liquoring the tanned stingray leather,

leading to a wet-end post-treated stingray leather, and

- a pre-finishing post-treatment comprising setting out, drying, stacking and buffing wet-end post-treated stingray leather, optionally further comprising polishing and/or cleaning wet-end post-treated stingray leather,

leading to pre-finished stingray leather.

In one embodiment, the wet-end post-treatment comprises dyeing the tanned stingray leather. In this embodiment, dyeing provides dyed leather, meaning that the leather in which dentine pearls are embedded is totally dyed. In one embodiment, dentine pearls are totally or partially dyed during the dying process. In another embodiment, dentine pearls are not dyed or slightly dyed in the dying process. The dying of dentine pearls during the dying process depends on the amount of dye. In order to give a specific color and/or effect to the pearls, a coating composition comprising pigments and/or effect agents should be applied as in the finishing process of the invention.

In one embodiment, the wet-end post-treatment comprises retanning the tanned stingray leather. In this embodiment, retanning comprises the steps of tanning, neutralizing, dyeing, fatliquoring and/or fixation. In one embodiment, the pre-finishing post-treatment comprises drying the leather. According to one embodiment, drying step may be performed by hanging, by using a drying tunnel, by toggle drier and/or by vacuum drying.

According to a first embodiment the process of the present invention is a solvent-based process. According to a second embodiment, the process of the present invention is a water-based process. According to a third embodiment, the process of the present invention is a mixed process comprising solvent-based steps and water-based steps.

According to one embodiment, leather used in the process of the invention is not leather made from shark skins. Finished stingray leather

The invention also relates to finished stingray leather obtained by the process of the present invention using the coating composition of the invention.

According to an embodiment, the finished stingray leather of the present invention may be processed to give various leather products. Examples of leather products are leather accessories such as a purses, document holders, wallets, coin cases (as small leather goods), straps and belts, watch bands, book covers, smart phone/mobile covers, numeric tablet covers; computer covers and bags (all sizes), eyewear, scientific instruments (microscopes, telescopes, etc), pens, boxes (jewelry or others), clothes and jackets, footwear, furniture, automotive, plane and boat interiors, walls, doors, panels, ceilings for interior decoration or design in general covering any surface for improving handle, grip, appearance, durability, style and design.

The finished stingray leather according to the present invention has the advantage to have good hydrolysis resistance, excellent flexing resistance, good scratch resistance and good UV resistance. In one embodiment, the coated stingray leather according to the present invention has a flexing resistance superior to 20,000 dry flexes. Mechanical properties of the finished leather of the present invention may be assessed by using tests such as:

- adhesion of finish (IUF 470)

- flexing endurance (BS EN ISO 5402:2002)

- light fastness (BS EN ISO 105-B02: 1999)

- dry / wet rub fastness (BS EN ISO 11640: 1998)

- perspiration rub fastness (BS EN ISO 11640: 1998)

- softness (ISO 17235:2002 / IUP 36) The finished and tanned leather of the present invention may also be chemically characterized by the following tests, especially to assess the content in undesirable compounds:

Azo dyes and arylamines content (BLC Method 7C.1 based on BS EN ISO 17234-1:2010)

- chrome VI content (EN ISO 17075:2007)

- formaldehyde content (BLC Method 7A.9 based on BS EN ISO 17226- 1:2008, HPLC analysis)

- pH (BS EN ISO 4045:2008)

heavy metal screening (EN71:Part 3, migration of certain elements) - lead content (total digestion followed by BLC Method 7D.3, ICP analysis) cadmium content (total digestion followed by BLC Method 7D.3, ICP analysis)

- REACH screening for SVHC Standard 10 day.

In one embodiment, the finished stingray leather according to the present invention has an aniline-wise look.

In one embodiment, the coating according to the invention protects finished stingray leather from aging. According to one embodiment, the coating according to the invention improves flexing resistance, stain resistance, abrasion resistance, appearance, smoothness and warm-touch feeling of the finished leather. EXAMPLES: The present invention is further illustrated by the following examples. Example 1: Black water-based-coating compositions

Amounts of the different components are given in grams.

Coat #1 Coat # 2 Coat #3 Coat #4

Component Function % % % % grams grams grams grams

w/w w/w w/w w/w water vehicle 300 33 \ \ \ \ \ \

film

Roda Pur

forming \ \ 250 41.0 20 15.4 \ \ 1817 - TFL

component

film

Roda Pur 67

forming \ \ 50 8.2 \ \ \ \ - TFL

component

film

Roda Car

forming \ \ 200 32.8 \ \ \ \ 5768 - TFL

component

film

TLC 300 - forming \ \ 50 8.2 6 4.6 10 7.7 TFL

component

film

sRoda Pur

forming \ \ \ \ 96 73.1 30 23.1 1427 - TFL

component

film

Top EP 110

forming \ \ \ \ \ \ 60 46.1 - TFL

component

film

Car Matt 92

forming \ \ \ \ \ \ 20 15.4 - TFL

component

Roda Link

cross linker 10 1 10 1.6 2 1.5 3 2.3 C 70 - TFL

pigmented

Roda Pur film

300 33 \ \ \ \ \ \ ADX - TFL forming

component

RodaLite

Black SH - pigment \ \ 50 8.2 \ \ \ \ TFL

Iriodin /

Miraval / effect

\ \ \ \ 3 2.3 \ \ Colorstream pigment

- Merck

Roda Mod handle

\ \ \ \ 3 2.3 7 5.4 2075 - TFL modifier

IPA penetrator 300 33 \ \ \ \ \ \ The coating compositions coat #1, coat #2, coat #3 and coat #4 were prepared by mixing the different components.

It should be noted that in coat #2, coat #3 and coat #4, components used already comprise water. Therefore, no additional water was used as vehicle.

Example 2: Gold solvent-based coating composition

Amounts of the different components are given in grams.

* The use of the cross linker in Coat#l depends on the desired degree of fastness and of the desired flexibility of the film. The higher the amount of cross-linker, the harder the film and partial loss of flexibility may happened.

Example 3: Finishing process

Raw material: a pre-finished stingray leather, i.e. stingray leather that has been treated after tanning and by dyeing, retanning, fatliquoring, setting out and drying. a) Buffing flesh side: The flesh side of the pre-finished stingray leather was buffed in a buffing machine equipped with sand paper. Due to the degree of flesh that needed to be removed, different sandpaper grades were used, namely paper N°80, 100 and 180 and 240 and 320. Four passages were performed in the buffing machine with paper N°80 and 4 passages with paper N°100, 2 passages No.180, 2 passages with paper No. 240 and 2 passages with paper No. 320. Quality controls were performed between passages in the buffing machine to finally obtain a thickness between 1 - 2mm depending the size and nature of the skins.

After buffing, leather was passed in a dedusting machine to remove dust. b) Polishing pearl side

Dedusted buffed stingray leather was then polished on the pearl-side in a polishing machine equipped with sand paper. In order to obtain a smooth effect, different sandpaper grades were successively used, namely paper N°100, 120, 240, 320 and 400. Four passages were performed in the polishing machine with paper N°100, 4 passages with paper N°120 and 2 passages with paper N°240 and 2 passages with paper N°320 and 2 passages with paper N°400. Quality controls were performed between passages in the polishing machine to finally obtain expected smoothness. If needed even a last passage with paper N°600 can be done.

After polishing, leather was passed in a dedusting machine to remove dust. c) Coating

Water-based coating compositions

The black water-based coating compositions prepared in example 1 were applied using a spray gun on polished stingray leather. One to three spray layers of Coat #1, Coat #2, Coat #3 and/or Coat #4 were applied. Each coat was let drying for about 5 minutes in an oven at a temperature of about 90- 100°C and was then let curing for about 5-10 hours, before applying the other ones. Black stingray leather was obtained.

Solvent-based coating composition

The gold solvent-based coating compositions prepared in example 2 were applied using a spray gun on polished stingray leather. One to three spray layers of Coat #1, Coat #2 and/or Coat #3 were applied.

Each coat was let drying for about 5 minutes in an oven at a temperature of about 90- 100°C and where applicable was then let curing for about 5-10 hours, before applying the other ones.

Gold stingray leather was obtained.

Example 4: Qualitative softness test

The softness feeling of the gold stingray leather prepared in example 3 was qualitatively evaluated by touch feeling according to the following criteria:

A. very soft

B. soft

C. medium

D. hard

E. very hard

Gold leathers prepared in example were found to have a "A" softness. Comparatively, a commercially available gold stingray leather was found to have a "B" softness.

Example 5: Mechanical tests

The gold stingray leather prepared in example 3 of the present invention and a commercially available gold stingray leather were tested against British Standards of Leather goods. "ND" stands for "not determined" and "GSR" stands for "Grey scale rating".

The *GSR rating is the following:

GSR 5 - no change in appearance

GSR 4 - slight change in appearance

GSR 3 - moderate change in appearance

GSR 2 - marked change in appearance

GSR 1 - very marked change in appearance

Results are presented in the table below.

Even though both leathers (i.e. the gold stingray leather prepared in example 3 of the present invention and the commercial gold stingray leather) meet the British standards minimum requirements, values obtained for the different parameters demonstrate that the gold stingray leather prepared in example 3 of the present invention has much better mechanical properties than the commercial one. Especially, the stingray leather of the invention is softer, has a better adhesion of its coating (finish) and a better color fastness to rubbing.

Claims

1. A process for manufacturing a finished stingray leather comprising coating a stingray leather with a coating composition comprising: a vehicle comprising an organic solvent and/or water,

a film forming component, and

at least one mean for coloring the composition.

2. The process according to claim 1, wherein the organic solvent is selected from alcohol such as ethanol, diacetone alcohol, isopropanol or n-butanol; ketones, acetone, dimethylformamide, ethers, alkanes such as pentane, cyclopentane, hexane, toluene, heptane or cyclohexane; cyclic ethers such as tetrahydrofuran or 1,4- dioxane, glycol ethers, ethylene glycol monobutyl ether acetate, cellosolve acetate, methyl cellosolve acetate, butyl cellosolve, ethyl cellosolve, phenylated solvents such as xylene; esters of acetic acid such as butyl acetate, methyl acetate, pentyl acetate, propyl acetate or ethyl acetate; chlorinated hydrocarbons such as methylene chloride, chloroform or methylchloroform; or a mixtures thereof.

3. The process according to claim 1 or claim 2, wherein the film forming component comprises a film forming polymer, a film forming resin or a mixture thereof.

4. The process according claim 3, wherein the film forming polymer is selected from polyurethane, polyurethane copolymers, cellulose acetate, cellulose acetate butyrate, ethyl cellulose, nitrocellulose, vinyl polymers, vinyl acetate polymers or copolymers, vinyl acrylates, methacrylate polymers, acrylate polymers, styrenated acrylic polymers, acrylic-urethane polymers, olefin polymers, olefin copolymers or mixtures thereof.

5. The process according to claim 3, wherein the film forming resin is selected from drying or non-drying alkyl resin, polyvinyl resins such as polyvinyl acetate, polyester resins, epoxy resins, acrylic polymers and copolymers, maleic modified glycerol esters of rosin, toluene sulfonamide/epoxy resins, tosylamide resin, arylsulfonamide formaldehyde resins or mixtures thereof.

6. The process according to anyone of claims 1 to 5, wherein the film forming component further comprises UV light absorbers, photo initiator agents, polymerization initiators, curing agents (also called cross-linkers), curing accelerators or a mixture thereof.

7. The process according to anyone of claims 1 to 6, wherein the mean for coloring is a pigment, a colorant or a mixture thereof.

8. The process according to claim 7, wherein the pigment is selected from natural mineral mica, said mica being covered or not with a layer of metal oxide; silicon dioxide platelets, calcium aluminium borosilicates, bismuth oxichloride or mixture thereof.

9. The process according to claims 1 to 8 wherein the coating composition is applied on the pearl-side of a stingray leather.

10. The process according to anyone of claims 1 to 9 further comprising a preliminary step of polishing the pearl-side of a stingray leather.

11. The process according to anyone of claims 1 to 10, comprising applying one, two or three layers of a coating composition, at least one layer thereof being a layer of the coating composition as described in anyone of claims 1 to 8.

12. The process according to claim 10 or claim 11, further comprising a cleaning step between the step of polishing and the coating step.

13. The process according to anyone of claims 10 to 12, further comprising a step of buffing the flesh- side of a stingray leather, preferably prior to polishing the pearl- side of the stingray leather.

14. The process according to anyone of claims 1 to 13, performed on a pre-finished stingray leather, said pre-finished stingray leather being obtained by a process comprising the following steps:

a pre-treatment step comprising:

o liming the skin to remove remaining flesh and fat, and/or o deliming and/or bating the skin, and/or

o bleaching the skin,

leading to a pre-treated stingray skin,

leading to tanned stingray leather,

leading to a wet-end post-treated stingray leather, and

a pre-finishing post-treatment comprising setting out, drying, stacking and buffing wet-end post-treated stingray leather,

leading to pre-finished stingray leather.

15. A stingray leather obtainable by the process according to anyone of claims 1 to 14.

16. The stingray leather according to claim 15, which forms parts of leather accessories such as a purse, a document holder, a wallet, a coin case, a belt, a strap, a watch band, a book cover, a smartphone cover, a mobile cover, a numeric tablet cover, a computer cover, a bag, an eyewear, a scientific instrument, a pen, a box, a footwear, clothes, a jacket; a furniture item for automotive, plane and/or boats interiors, walls, doors, panels, ceiling for interior decoration or design.