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Title:
COMPOSITION AND PROCESS FOR LEATHER DYEING WITH POLYCARBODIIMIDES AND DYES
Document Type and Number:
WIPO Patent Application WO/2022/098232
Kind Code:
A1
Abstract:
The present invention relates to a novel dyeing composition suitable for dyeing leather, hides and/or pelts comprising at least one dyeing agent and at least one polycarbodiimide agent and optionally water-miscible organic solvent and/or optionally one or more plasticizer and/or optionally one or more dispersing agents and/or optionally one or more acidifying agents, to obtain leather that has good colour fastness according to ISO 11640:2012 and good lightfastness according to ISO105-B02 and/or to IUF 402 and that results in an outstanding uniform colouring throughout the leather.

Inventors:
GAMARINO ROBERTA (IT)
MATTIOLO EMANUELE (IT)
PIERINI MASSIMO (IT)
Application Number:
PCT/NL2021/050673
Publication Date:
May 12, 2022
Filing Date:
November 03, 2021
Export Citation:
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Assignee:
STAHL INT B V (NL)
International Classes:
D06P1/02; D06P1/06; D06P1/08; D06P1/10; D06P1/39; D06P3/32; D06P1/649
Domestic Patent References:
WO2019235658A12019-12-12
WO2019235658A12019-12-12
WO2019235658A12019-12-12
Foreign References:
US20100174018A12010-07-08
US5002586A1991-03-26
EP3342395A22018-07-04
EP3431555A12019-01-23
US20120047663A12012-03-01
KR101453216B12014-10-22
KR20180108266A2018-10-04
US20100174018A12010-07-08
Other References:
DATABASE WPI Week 201475, Derwent World Patents Index; AN 2014-U14953, XP002803710
"Progress in Organic Coatings", vol. 55, 2006, pages: 142 - 148
Attorney, Agent or Firm:
WITMANS, H.A. (NL)
Download PDF:
Claims:
36

CLAIMS

1. Dyeing composition suitable for dyeing leather, hides and/or pelts comprising at least one dyeing agent and at least one polycarbodiimide agent and optionally water-miscible organic solvent and/or optionally one or more plasticizers and/or optionally one or more dispersing agents and/or optionally one or more acidifying agents.

2. Composition according to claim 1, wherein the weight ratio between the dyeing agent and the polycarbodiimide agent is between 5 and 500 parts of dyeing agent to 100 parts of polycarbodiimide agent, preferably between 10 and 200 parts of dyeing agent to 100 parts of polycarbodiimide agent, more preferably between 20 and 100 parts of dyeing agent to 100 parts of polycarbodiimide agent, even more preferably between 15 and 100 parts of dyeing agent to 100 parts of polycarbodiimide agent wherein the parts of both dyeing agent and the polycarbodiimide agent are referring to the mass of the non-volatile components therein.

3. Composition according to claim 2 wherein the ratio between the dyeing agent and the polycarbodiimide agent is between 20 and 75 parts of dyeing agent to 100 parts of polycarbodiimide agent wherein the parts of both dyeing agent and the polycarbodiimide agent are referring to the mass of the non-volatile components therein.

4. Composition according to any one of claims 1 to 3 wherein the amount of polycarbodiimide agent on total dyeing composition considering only the non-volatile components therein is between 10 and 70 weight%, preferably between 15 and 65 weight%.

5. Composition according to claim 4 wherein the amount of polycarbodiimide agent on total dyeing composition considering only the nonvolatile components therein is between 17 and 50 weight% and most preferably between 20 and 40 weight%. 37

6. Composition according to any one of claims 1 to 5, wherein the amount of polycarbodiimide agent on total dyeing composition considering also the volatile components therein is between 1 and 30 weight%, preferably between 2 and 20 wt%.

7. Composition according to any one of claims 1 to 6, wherein the polycarbodiimide agent is liquid at ambient conditions (atmospheric pressure and a temperature of 25°C), or wherein the polycarbodiimide may be a solution in a solvent or water or may be a dispersion in water.

8. Composition according to any one of claims 1 to 7, wherein the total dyeing composition is liquid at ambient conditions.

9. Composition according to any one of claims 1 to 8, wherein the composition may contain one or more water-miscible organic solvents of up to 70% by weight of the overall weight of the composition.

10. Composition according to any one of claims 1 to 9, wherein the dyeing agent is a metal complex or metal free dye, preferably based on azo derivatives.

11. Composition according to any one of claims 1 to 10 wherein the composition does not comprise a pigment.

12. Composition according to any one of claims 1 to 11 wherein the polycarbodiimide agent contains hydrophilic groups so as to improve miscibility in aqueous mixtures.

13. Composition according to any one of claims 1 to 12 wherein the polycarbodiimide agent is not based on tetramethylxylene diisocyanate.

14. Composition according to any one of claims 1 to 13 wherein the polycarbodiimide agent is based on 3-isocyanatomethyl-3,5,5- trimethylcyclohexyl-isocyanate or 4,4'-methylene dicyclohexyldiisocyanate.

15. Composition according to any one of claims 1 to 14 wherein the composition does not comprise an additional polymeric component such as a reaction-promoting additive for forming a peptide bond or a random polyurethane.

16. A process for preparing the composition as defined in any one of the preceding claims, comprising simple mixing of the various components optionally in a solvent, solvent mixture, water or any mixture thereof.

17. Process according to claim 16, wherein the respective dyeing agent and polycarbodiimide agent are liquid at ambient conditions and are mixed in liquid form or one or both of these two agents is in solid form at ambient conditions and is pre-dissolved in water or solvent and then mixed in liquid form with the other agent.

18. Use of a composition as defined in any one of claims 1 to 15 for dyeing of pre-tanned leather, tanned leather, pelts, skins, hides, leather intermediate products or non-finished leather.

19. Use according to claim 18 by dip or float dyeing, sponging or brush dyeing and spray dyeing, or other dyeing techniques such as paddle dyeing, by dyeing in a through-feed machine, by using a curtain coater, by using a roll coater, by screen printing, by tray dyeing, by deeping or by using a paint coater.

20. Process for dyeing of pre-tanned leather, tanned leather, pelts, skins, hides, leather intermediate products or non-finished leather using a dyeing composition as defined in any one of claims 1 to 15.

21. The leather, obtainable by the process of claim 20.

22. Leather according to claim 21 having a good colour fastness according to ISO 11640:2012 and good lightfastness according to ISO 105-B02 and/or to IUF 402 and that results in an outstanding uniform colouring among the leather.

23. A kit of parts comprising 1) a first compartment comprising the first composition, and 2) a second compartment comprising a second composition, wherein the first composition comprises at least one polycarbodiimide agent and the second composition comprises at least one dyeing agent for combined use to dye leather, hides or pelts.

Description:
Title: Composition and process for leather dyeing with polycarbodiimides and dyes

The present invention relates to a novel dyeing composition for dyeing leather (the term “leather” encompassing fur skins, hides or pelts).

Leather is a durable, flexible material created via the tanning of animal rawhide and skin. The leather manufacturing process is divided into three fundamental sub-processes: preparatory stages, tanning and crusting.

The present invention relates to the sub-process of crusting, especially the colouring part thereof.

In the preparatory stages, hide or skin is prepared for tanning. After trimming, animal skin is soaked to remove salts and other solids, while restoring moisture when the skin was first dried. Then, the flesh side of the wet skin is scraped to remove any remaining traces of flesh or fat, and the skin is optionally dehaired. After an optional bating and pickling step, the skins are subjected to tanning. Other potential steps that may be part of the preparatory stages include preservation, liming, splitting, reliming, deliming, degreasing, frizzing, bleaching and depickling.

Tanning is the process of preserving the skins by converting the protein, and especially the collagen, of the raw hide or skin into a stable material that does not putrefy and provides tanned leathers with satisfactory properties, such as high shrinkage temperatures Ts, suppleness and suitability for subsequent processing such as neutralization, retanning, fatliquoring, dyeing, finishing.

Tanning is carried out by using either vegetable chemicals, using tannin and other ingredients derived from vegetable matter such as the bark of certain trees, by the use of chromium salts (giving so-called wet-blue leather), by the use of aldehydes (resulting in wet-white leather), by the use of organic reactive tanning agent (resulting in wet-white leather), by use of synthetic tannins (syntans), or other conventional techniques. The product prepared in this sub-process is called “tanned leather”. As said, the present invention focuses on the sub-process of crusting, and especially on the colouring part thereof. Crusting is the process wherein the tanned hide or skin is thinned, retanned, and lubricated, and often a colouring operation is included in the crusting sub-process. Any chemicals used or added during crusting must be fixated in place. The crusting process ends with drying and softening operations. This description of the crusting process is not complete; crusting may also include wetting back, sammying, splitting, shaving, rechroming, neutralization, filling, stuffing, stripping, whitening, fixating, setting, conditioning, milling, staking and buffing.

The chemical aspects of the crusting process at least encompass retanning (optionally following neutralization, especially after chrome-tanning) and fatliquoring. Usually in the preparation of leather from tanned hides, the re-tanning and fatliquoring is done in separate steps.

The initial colour of a leather is dependent on the tanning agents used. Tannins of plants give the leather a brownish tone, whereas fat and oil tanning makes leather yellowish, while tanning with alum and synthetic tanning agents give the leather a whitish tone and chrome tanning makes it bluish-greyish. These are often not the colours desired by customers and hence the tanned leather needs to undergo a colouring step. In the colouring of leather, two main colouring methods are distinguished. The first process involves dyeing the leather with dyes and the second one involves pigmentation of the surface with binder-based colours. The present invention concerns the dyeing of leather.

Most leather is first dyed through completely. This is usually done with liquid dye like ink that is also used for colouring of textiles. Dyes dissolve and can thus penetrate everywhere. Pigments are solid particles that remain on the outside of the fibres and hence a through coloring cannot be obtained by using pigments. For this purpose, the leather is immersed in a dye bath in rotating barrels. The dye has to be fixed and excess colour has to be rinsed out to prevent dye transfer from leather. There are leathers that are not further coated and then the dyeing is the only colouring that is applied onto the leather, such as aniline leather, nubuck and suede. Other leathers can be further coated with finish layers that may contain dyes and pigments, but nevertheless these leathers are usually dyed through anyway, so that leathers with mechanical damages to the finish still have a similar colour tone in the area of the damage.

Dyeing of leather is an intricate process. Leather dyes refer to dyes with an affinity to leather and for leather colouring. Leather is dyed mainly by means of selected acids, substantive or metal-complex dyes and, to a minor extent, basic dyes. Further, in some cases, superficial dyeing or surface colouring is required whereas in the case of shoe leather and garment leather, certain degree of penetration is desired which will resist or minimize further buffing or scuffing of the leather surface.

Based on solvent types, dyes can be divided into two categories: non-water-soluble dyes and water-soluble dyes. Non-water-soluble dyes comprise: sulphur dyes soluble in aqueous solution of sulphide; fat-soluble oilsoluble dyes and alcohol-soluble dyes. Water-soluble dyes include: anionic acid dyes; direct dyes; special dyes for leather; amphoteric metal complex dyes; triphenylmethane dyes of sulphite and cationic alkaline dyes.

There are three techniques to dye leather: dip dyeing, sponging or brush dyeing and spray dyeing.

Dip dyeing is one of the most common leather dyeing techniques used in tanneries. The hides are introduced into a drum and soaked in a considerable quantity of water containing the leather dye. Generally, to increase the penetration of the dyes inside the leather fibres the temperature is raised to 50-60°C, and the rotary movement of the drum further favours the penetration of the leather dyes.

Sponging is used in tanneries when it is necessary to colour delicate leathers, for example for the production of glove articles, where the prerogative is to maintain the original softness of the leather that could be altered by the strong mechanical action of the drum or to colour high quality leather articles, for example shoes, garment or upholstery articles. This artisanal leather colouring technique is still used today in some tanneries, but only for the production of very fine leathers, as the cost of labour for colouring is high.

Spraying is used in tanneries as a valid alternative to drum and is generally carried out using a special machine, consisting of a carousel rotary machine with spray guns that rotate and spray leather dye simultaneously on the leather. The spraying technique has considerably shortened the industrial production times as it is a very rapid process and requires a minimum employment of labour. Often it is used to modify the colour of the leather already dyed in drum.

Colour migration is an important aspect in leather dyeing. The term "migration" refers to the tendency of substances to move from one material to another wherein the dissolved portions of colorant may migrate from their medium of application to the surface or into a similar material with which it is in contact. This colour migration is a problem in current dyeing systems and reduction of such colorant migration is very desirable.

ISO 15701:2015 specifies a method for assessing the propensity of dyes and pigments to migrate from leather to a synthetic substrate by determining the transfer of colour from the leather to white plasticized poly(vinyl chloride) in contact with it. This method is suitable for leather of all kinds at any stage of processing.

ISO 11640:2012 specifies a method for determining the colour fastness of leather to cycles of to-and-fro rubbing. Colour fastness tests according to ISO 11640:2012 can be done as a measure for colour fixation upon mechanical abrasion and involve rubbing a white woollen felt, loaded with a weight over a stretched leather surface for several times. Then the leather and the felt are checked for changes in colour, and the colour difference is compared with a grey scale. This type of rub fastness tests are often called Veslic tests. The felt can be used dry or soaked in water. Reported are the number of rubs that have been done and the colour change according to the grey scale for those numbers of rubs. Less change in colour is better, as well as a higher number of rubs that can be done to arrive at the same change in colour.

IUF 402 specifies a method for determining the resistance of the colour of leather to the action of an artificial light source, by exposing to xenon arc under prescribed conditions, along with eight dyed wool standards. The resistance is assessed by comparing the fading of the leather with that of the standards. The scores range from 1, which is very low light resistance, to 8, which is very high light resistance.

ISO 105-B02 assesses the light resistance. This methodis intended for determining the resistance of the colour of leather to the action of a standard artificial fight source. The Xenon lamp has an emission wavelength profile close to daylight; the colour change of the leather is visually assessed with grey scales, with a scale ranging from 5 (best) to 1 (worst) or with blue scales, with a scale ranging from 8 (best) to 1( worst).

EP3431555-Al describes a dyeing composition for leather that gives very good colour fastness, which was evaluated according to ISO 15701 using plasticised polyvinylchloride (PVC), wherein the sample is placed in contact with a standardised PVC material, under a defined pressure for 16 hours at 50°C. However, no mention is made of the performance according to ISO 11640:2012, which specifies a method for determining the colour fastness of leather to cycles of to-and-fro rubbing.

US20 120047663-Al discloses a method for reactive dyeing of leather, which involves providing a reactive dye solution comprising at least one reactive dye and water, and making the reactive dye in the reactive dye solution to act on crust leather at a temperature from 25° C to 70° C to form covalent bonds between the reactive dye and the crust leather. The drawback of this prior art is the lengthy process involved in dyeing and the high temperature, of up to 70°C, which makes it unsuitable for dyeing leather which cannot withstand high temperatures.

KR10 1453216-B1 describes a dye composition comprising a carbodiimide compound and a dye, preferably a reactive dye, that introduces a specific functional group capable of covalent bonding with a protein residue of hair, skin, fiber or leather, which composition can continuously impart a semi-permeable dyeing effect without damage to hair, skin, fibres or leather The carbodiimide is preferably directed to a specific polycarbodiimide made from tetramethylxylene diisocyanate (TMXDI) or to l-ethyl-3-(3- dimethylaminopropyl)carbodiimide, which is a monocarbodiimide, and the dyeing is mainly directed to hair. The amount of carbodiimide compound is between 0.001 and 10 pbw per 100 pbw of dyeing composition and the amount of the dye is between 0.001 and 50 pbw per 100 pbw of dyeing composition. In the examples the amount of dye as well as TMXDI polycarbodiimide is 0.5 wt% on total dyeing composition.

WO2019235658-A1 and KR20180108266 are similar, but describe additionally a requirement for a reaction-promoting additive for forming a peptide bond. This reaction-promoting additive for forming a peptide bond is selected from a group consisting of hydroxysuccinimide, hydroxycarb amide, hydroxytriazole, hydroxybenzotriazole, hydroxypyridinone, hydroxyphenylbenzimidazole, hydroxyindolinone, hydroxybenzotriazine and oxyma, or a water-soluble nonionic polymer, a bead- or resin-type polymer resin, but most emphasis is given to the various polymer types that may be suitable. In the examples a polybutene is included in an amount of 16 wt%, besides other oily components that may also be considered as non-ionic polymers. In the examples the amount of dye is 0.01 wt% and the amount of TMXDI polycarbodiimide is 0.1 wt% both on total dyeing composition.

US 2010/174018 describes an aqueous formulation comprising a pigment, a polycarbodiimide and a random polyurethane for coloring textile substrates such as leather. Pigments are being defined as substantially insoluble, dispersed, finely divided, organic or inorganic colorants as defined in DIN 55944. No dye is used.

After the dyeing process of leather, it is generally observed that the dyeing intensity is not evenly distributed among the leather as wrinkles in the leather are generally of a slightly different colour. This effect is most pronounced when leathers have been tanned by the use of organic reactive tanning agents. This effect is not desired as it has a disadvantageous effect on the appearance of the leather.

Hence there is a need to provide a dyeing composition for dyeing leather not possessing the disadvantages of the prior art dyeing compositions.

The object of the present invention is to provide a dyeing composition that shows good colour fastness according to ISO 11640:2012 after application on leather and that results in an outstanding uniform colouring among the leather.

It has been surprisingly found that using a dyeing composition comprising a dyeing agent and a polycarbodiimide agent provides dyed leathers that can withstand much higher number of rubs in rub fastness tests according to ISO 11640:2012 and that has a more evenly distributed colour among the leather than is obtained when dyes are used without polycarbodiimide or when current industry dyeing products are used.

Hence, in a first aspect, the present invention relates to a dyeing composition suitable for dyeing leather, hides and/or pelts comprising at least one dyeing agent and at least one polycarbodiimide agent and optionally water-miscible organic solvent and/or optionally plasticizer and/or optionally dispersing agent and/or optionally acidifying agent. Herein, the term “water- miscible organic solvent" denotes an organic solvent that forms a homogeneous liquid phase with water.

Preferred ratios between the dyeing agent and the polycarbodiimide agent are between 5 and 500 parts of dyeing agent to 100 parts of polycarbodiimide agent, wherein the parts of both dyeing agent and the polycarbodiimide agent are referring to the mass of the non-volatile components therein. More preferably, the ratio between the dyeing agent and the polycarbodiimide agent is between 10 and 200 parts of dye to 100 parts of polycarbodiimide agent, even more preferably the ratio between the dyeing agent and the polycarbodiimide agent is between 15 and 100 parts of dye to 100 parts of polycarbodiimide agent and most preferably the ratio between the dyeing agent and the polycarbodiimide agent in between 20 and 75 parts of dye to 100 parts of polycarbodiimide wherein the parts of both dyeing agent and the polycarbodiimide agent are referring to the mass of the non-volatile components therein. In the context of the present invention non-volatile components are those components that do not evaporate into air due to their low vapour pressure and can be defined as any component that has an initial boiling point above 250°C measured at a standard pressure of 101.3 kPa.

In a preferred embodiment, the polycarbodiimide agent used as component of the dyeing composition is liquid at ambient conditions (atmospheric pressure and a temperature of 25°C), wherein the polycarbodiimide may be solution in a solvent or water or may be a dispersion in water. In instances that the polycarbodiimide agent is a solution in a solvent or water or a dispersion in water, it is preferred that the concentration of the polycarbodiimide polymer in the solution or dispersion is above 20 weight%, more preferably above 30 weight%, even more preferably above 40 or 50 weight%.

In a more preferred embodiment, the total dyeing composition is liquid at ambient conditions.

Preferably the amount of polycarbodiimide agent on total dyeing composition considering only the non-volatile components therein is between 10 and 70 weight%, preferably between 15 and 60 weight%, more preferably between 17 and 50 wt%,most preferably between 20 and 40 wt%. Whereas WO20 19/235658 mentions that a content of polycarbodimide of more than 10 parts by weight, leads to difficulties to improve the efficacy, odor and properties of a product, and creates problems in formulation and formulation stabilization due to the excessive amount of the carbodiimide-based compound, which is more than reaction sites present on the surface of hair, skin, fingernails, toenails, fiber or leather, this is not the case in the present invention wherein also amounts of above 10% of carbodiimide still provide good dyed leather.

Preferably the amount of polycarbodiimide agent on total dyeing composition considering all the components is between 1 and 30 wt%, more preferably between 2 and 20 wt%.

The dyeing composition of the present invention contains a dyeing agent, i.e. a dye. A dye is a colorant, either liquid or solid, that is soluble in water or another solvent. A dissolved dye can thus penetrate equally far inside a material as the liquid in which it is dissolved can penetrate. Contrary hereto a pigment is a solid colorant that does not dissolve in water or any other solvent and thus remains a solid always. A pigment has a certain particle size and this limits the maximum dilution and penetration into a material. Hence, dyes, and not pigments, are used for through-dyeing of leather. The dyeing composition of the present hence preferably does not contain any pigment.

The dyeing agent in the dyeing compositions of the present invention is selected from one of or a combination of conventional dyes, and examples of such dyes are acridine dyes, anthraquinone dyes, diarylmethane dyes, triarylmethane dyes, poly arylmethane dyes, carbonyl dyes, azo dyes, diazonium dyes, metal complex dyes, nitro dyes, nitroso dyes, phthalocyanine dyes, quinone-imine dyes, azin dyes, eurhodin dyes, safranin dyes, indophenol dyes, oxazin dyes, oxazone dyes, thiazin dyes, thiazole dyes, xanthene dyes, fluorene dyes, pyronin dyes, fluorone dyes and rhodamine dyes, or from one of or a combination of reactive dyes or from one of or a combination of substantive or direct dyes or from one of or a combination of special leather dyes and high fastness dyes. In a preferred embodiment, the dyeing agent is supplied in liquid form at ambient conditions (atmospheric pressure and a temperature of 25°C), either because the dyeing agent non-volatile component is liquid or because the dyeing agent non-volatile component is dissolved in a solvent or in water or is dispersed in water.

Preferred are metal complex and metal free dyes mainly based on azo-derivatives. Examples of suitable metal free dyes are C.I. Acid Red 249 (azo derivate), C.I. Acid blue 83 (triarylmethane derivate), C.I. Acid black 210 (azo-derivate) , C.I. Yellow 42 (azo-derivate); examples of suitable metal complex dyes are C.I. Acid Red 227 (azo-derivate), C.I. Acid Yellow 59 (azo- derivate) , C.I. Acid Black 172 (azo-derivate ).

The polycarbodiimide agent in the dyeing compositions of the present invention is selected from the group of polycarbodiimides that are known as polycarbodiimide crosslinker in the leather finishing industry or in the coatings industry. These polycarbodiimides agents contain more than one carbodiimide group (-N=C=N-) in their polymer chain or oligomer chain, preferably these polycarbodiimide agents contain from 2 to 10, preferably from 2 to 6 carbodiimide groups on average. These polycarbodiimides agents are supplied in liquid form, either because the polycarbodiimide non-volatile component is liquid or because the polycarbodiimide non-volatile component is dissolved in a solvent or in water or is dispersed in water. These polycarbodiimide agents are generally linear polymers, synthesized from diisocyanates and optionally mono-isocyanates, wherein some other functional groups such as hydrophilic components may have been incorporated so that the polycarbodiimide agents are miscible in aqueous mixtures. This type of products has been described in Progress in Organic Coatings, volume 55, pages 142-148, 2006. Examples of such polycarbodiimide agents are XR- 5592 (a waterborne polycarbodiimide with about 40% non- volatiles), XR- 5570 (a solventborne ‘multifunctional’ polycarbodiimide with about 50% non-volatiles, wherein ‘multifunctional’ indicates that beside carbodiimide also other reactive functional groups are present), XR-5517 (a solventborne polycarbodiimide with about 50% non-volatiles in methoxypropyl acetate), XR- 13-554 (a liquid polycarbodiimide of 100% non-volatiles), XR-5508 (a waterborne polycarbodiimide with about 40% non-volatiles), XR-5525 (a solventborne ‘multifunctional’ polycarbodiimide with about 50% non- volatiles, wherein ‘multifunctional’ indicates that beside carbodiimide also other reactive functional groups are present), XR-55-250 (a solventborne ‘multifunctional’ polycarbodiimide with about 50% non-volatiles, wherein ‘multifunctional’ indicates that beside carbodiimide also other reactive functional groups are present), all obtainable from Stahl Europe BV, or Zoldine XL-29SE (a solventborne polycarbodiimide with about 50% non- volatiles in methoxypropyl acetate) obtainable from Angus Chemical Company. Especially preferred polycarbodiimide agents are those polycarbodiimide agents that are supplied in water or as 100% non-volatile, so without volatile organic solvents. Preferably the polycarbodiimide used in the present invention is based on isophorone diisocyanate (IPDI) or on 4, d'methylene dicyclohexyldiisocyanate (H12MDI). The polycarbodiimide used in the present invention is preferably not based on tetramethylxylene diisocyanate (TMXDI), which has a relatively low reactivity compared to polycarbodiimides made from IPDI or H12MDI. Preparation of TMXDI based polycarbodiimides also requires a higher reaction temperature, or a longer reaction time or more catalyst, compared to synthesizing polycarbodiimides made from IPDI or H12MDI.

The dyeing composition may contain one or more water-miscible organic solvents and/or one or more plasticizers of in total up to 70% by weight of the overall weight of the composition.

Preferably, the water-miscible organic solvent is selected from the group consisting of monohydric alcohols, polyhydric alcohols, ethers and ethers of polyhydric alcohols, ketones, esters of organic acids and aromatic solvents. Preferably, the ester of organic acids is selected from the group consisting of ethyllactate, dimethyl carbonate, propylene carbonate. Preferably, the polyhydric alcohol is selected from the group consisting of ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, dipropylene glycol dimethyl ether, butyltriglycol and 1- methoxy-2-propanol. More preferably, the water-miscible organic solvent is selected from the group consisting of ethanol, isopropyl alcohol, n-butanol, benzyl alcohol, butyltriglycol, acetone, ethyl methyl ketone, butyl acetate, diethylene glycol monobutyl ether, dipropylene glycol dimethyl ether and 1- methoxy-2-propanol, or mixtures thereof. The amount of water-miscible organic solvent, when present, is generally between 5 and 60 wt% on total dyeing composition.

The presence of a plasticizer is beneficial for the colour fastness. Preferably, the plasticizer is selected from the group of phtalic acid alkylesters, mono-acid alkylesters, di-acid alkylesters, tri-acid alkylesters, polyesters, phosphate esters, polyethers, polyether-polyesters, glycols, fatty acid esters, normal or modified natural or mineral oils, sulphonated oils, ethoxylated oils, epoxidized oils, fatty acids, sulfonamides, fat liquors, lecithine or mixtures thereof. Most preferred, the plasticizer is selected from the group consisting of tributoxy ethylphosphate, tetraethylene glycol dimethyl ether, triethylene glycol mono-2 -hexyl-hexanoate, acetyltribuylcitrate, acetyltrioctylcitrate, tributylcitrate, tributylphosphate, triisopropylphosphate, dioctyladipate, diisobutylmaleate, triethylene glycol dihexanoate. A plasticizer with some hydrophilic nature is preferred so that it can be dispersed easily in an aqueous dyeing composition. The amount of plasticizer, when present, is generally between 1 and 10 wt% on total dyeing composition. Also a combination of one or more water-miscible organic solvents and one or more plasticizers may be used.

The dyeing composition may contain one or more dispersing agents, which are added to improve the separation of particles and to prevent settling or clumping, of up to 5% by weight of the overall weight of the composition. The dispersing agent is preferably selected from the group consisting of surfactants, anti-agglomeration agents, deflocculants, anti-settling agent, polymeric dispersants, and more preferable the dispersing agent is selected from the group consisting of sodium polycarboxylate in aqueous solution. The presence of surfactant is beneficial for the colour fastness. The amount of dispersing agent, when present, is generally between 0.5 and 3 wt% on total dyeing composition.

The dyeing composition may contain one or more acidifying agents of up to 5% by weight of the overall weight of the composition. The acidifying agent is preferably selected from the group consisting of organic acids, and more preferable the acidifying agent is selected from the group consisting of acetic acid, p -toluene sulfonic acid, lactic acid, formic acid, or mixtures thereof. In the context of the present invention, it has been observed that the addition of an acidifying agent to the dyeing composition results in a stronger colour intensity, which is a beneficial effect.

The dyeing composition may also contain water, which may be added as an ingredient or which may be a component of the dyeing agent and/or the polycarbodiimide agent. The amount of water that is used is such that the components dissolve and have a good viscosity and dye loading. The amount of water should not be too high (generally less than 75 wt%, preferably less than 50 wt% of the dyeing composition) because then the color intensity is less due to the dilution.

The dyeing agent may contain other additional ingredients but preferably does not contain a reaction promoting additives as described in WO20 19235658, such as a nonionic polymer and/or a random polyurethane as described in US2010/174018. Such compounds are usually polymers with as disadvantage that these polymers will penetrate the leather and this will (likely) result in some stiffening of the leather, which is undesired for a flexible material like leather. Thus preferably the dyeing composition does not comprise any additional polymeric compounds.

The dyeing compositions of the present invention are prepared by simple mixing of the separate components into one mixture. This can be in a solvent, solvent mixture, water or mixtures thereof, preferably the components are mixed when these are in liquid form. This may involve predissolving in water or solvent of a component which is in solid form at ambient conditions and subsequent mixing with the other components. Mixing may take place at ambient temperatures, i.e. between about 10°C and 40°C and may use all kinds of available equipment.

The dyeing composition can be used immediately or very quickly following on preparation of the dyeing composition, but the dyeing composition can also be used while there has been a longer time interval following preparation of the dyeing composition, wherein the longer time interval can be mimicked by ageing the dyeing composition for a period of time at an elevated temperature, such as 24 hours at 50°C. In the context of the present invention, the use of a freshly prepared mixture is preferred, as this results in an outstanding uniform colouring throughout the leather, whereas using aged mixtures results in colouring throughout the leather that is not as uniformly distributed as with freshly prepared mixture, while using both freshly prepared mixture and aged mixture results in good colour fastness according to ISO 11640:2012 after application onto leather.

In a further aspect, the present invention relates to the use of said dyeing composition for dyeing leather, pelts, skins, hides, leather intermediate products or non-finished leather. Most preferably the dyeing composition is used for dyeing leather, leather intermediate products or nonfinished leather.

The dyeing compositions of the present invention can be applied using the well-known techniques to dye leather, such as dip or float dyeing, sponging or brush dyeing and spray dyeing, or other dyeing techniques such as paddle dyeing, by dyeing in a through-feed machine, by using a curtain coater, by using a roll coater, by screen printing, by tray dyeing, by deeping or by using a paint coater. The compositions of the present invention can be used in all conventional machines that are used for the dyeing of leather.

The dyeing compositions of the present invention can be used to prepare leathers for all applications, for example shoe, furniture, car, clothing and bag leathers.

Any kind of leather which is conventionally dyed is suitable to be dyed by using a dyeing composition of the present invention, particularly grain leather (e.g. nappa from sheep, goat or cow and box-leather from calf or cow), suede leather (e.g. velours from sheep, goat or calf and hunting leather), split velours (e.g. from cow or calf skin), buckskin and nubuck leather; further also woollen skins and furs (e.g. fur-bearing suede leather). The leather may have been tanned by any conventional tanning method, in particular vegetable, mineral, synthetic or combined tanned (e.g. chrome tanned, zirconyl tanned, aluminium tanned, synthetic organic reactive tanning or semi-chrome tanned). If desired, the leather may also be re-tanned; for retanning there may be used any tanning agent conventionally employed for retanning, e.g. mineral, vegetable or synthetic tanning agents [e.g. chromium, zirconyl or aluminium derivatives, quebracho, chestnut or mimosa extracts, aromatic syntans, polyurethanes, (co)polymers of (meth)acrylic acid compounds or melamine/dicyan diamide and/or urea/formaldehyde resins]. Thus, leathers of very high to very low affinity for anionic dyes may be used.

The leathers can be of various thicknesses, thus, thin leathers, suitable for garment leather or glove-leather (nappa), leather of medium thickness suitable for shoe upper leather and handbags, or also thick leathers suitable for shoe-sole leather, furniture leather, automotive leather, leather for suitcases, for belts and for sport articles; hair -bearing leathers and furs may also be used. The leather dyed according to the process of the invention is notable for a good colour fastness according to ISO 11640:2012 and for an outstanding uniform colour throughout the leather, which is able to mask defects such as wrinkles, notably on leathers tanned by organic reactive tanning agents, while other properties of the dyed leather, such as suppleness, tear strength, touch and feel aspects, remain good and are not deteriorated by the process of the invention.

The dyeing composition of the present invention is preferably supplied as a sole mixture of the various components. Alternatively, the dyeing composition may comprise two mixtures that combined comprise the various components. Hence, the present invention also relates to a kit comprising of 1) a first compartment comprising the first composition, and 2) a second compartment comprising a second composition, wherein the first composition comprises at least one polycarbodiimide agent and the second composition comprises at least one dyeing agent. The kit according to the present invention includes the first and the second compartment, each of which includes, respectively, the first composition and the second composition separately. The first and second compartment may be equipped with a dispensing unit or a discharging means, such as a pump. The first and second compartments may be separately included in two distinct containers, but may also be present in a single container. It is possible to use the kit by, for example, dispensing or discharging the first composition from the first compartment, followed by applying the first composition onto the leather, followed by dispensing or discharging the second composition from the second compartment, followed by applying the second composition onto the leather, which had already been treated with the first composition, or alternatively, by dispensing or discharging the first composition from the first compartment and dispensing or discharging the second composition from the second compartment, followed by mixing the first composition and the second composition into one mixture, followed by applying the mixture onto the leather.

The present invention will be further elaborated by the following non-limiting working examples. Parts and percentages of components referred to in these working examples are drawn to the weight of the total composition wherein these components are present, like in the other parts of the description and claims, unless otherwise indicated.

Example 1 Dyeing composition

A dyeing composition is made by adding together and mixing until homogenous of 250 g of XR-5592 (a waterborne polycarbodiimide, made from H12MDI-monomer, of 40% solids, obtainable from Stahl Europe BV), 220 g of butyltriglycol, 180 g of benzyl alcohol, 50 g of triisobutyl phosphate and 300 g of LD-5915 (a liquid black dye of 13% solids, obtainable from Stahl Europe BV).

The ratio dyeing agent/polycarbodiimide based on non-volatile components is 39/100. The amount of polycarbodiimide on total dyeing composition based solely on the non volatile components is 24 wt%. The amount of polycarbodiimide on total dyeing composition is 10 wt%, when taking into account also the volatile components.

Example 2 Dyeing composition

A dyeing composition is made by adding together and mixing until homogenous of 250 g of XR-5592 (a waterborne polycarbodiimide, made from H12MDI-monomer, of 40% solids, obtainable from Stahl Europe BV), 400 g of dipropylene glycol dimethyl ether, 50 g of triisobutyl phosphate and 300 g of LD-5915 (a liquid black dye of 13% solids, obtainable from Stahl Europe BV).

The ratio dyeing agent/polycarbodiimide based on non-volatile components is 39/100. The amount of polycarbodiimide on total dyeing composition based solely on the non volatile components is 53 wt%. The amount of polycarbodiimide on total dyeing composition is 10 wt%, when taking into account also the volatile components.

Example 3 Dyeing composition

A dyeing composition is made by adding together and mixing until homogenous of 370 g of XR-5570 (a solventborne ‘multifunctional’ polycarbodiimide, made from IPDI-monomer, of 50% solids in methoxypropyl acetate, wherein ‘multifunctional’ indicates that beside carbodiimide also other reactive functional groups are present, obtainable from Stahl Europe BV), 325 g of butyltriglycol, 266 g of benzyl alcohol and 38 g Cromalent Black S6 (a liquid black dye of 100% solids, obtainable from Stahl Europe BV).

The ratio dyeing agent/polycarbodiimide based on non-volatile components is 20/100. The amount of polycarbodiimide on total dyeing composition based solely on the non volatile components is 34 wt%. The amount of polycarbodiimide on total dyeing composition is 19 wt%, when taking into account also the volatile components.

Example 4 Dyeing composition

A dyeing composition is made by adding together and mixing until homogenous of 370 g of XR-5570 (a solventborne ‘multifunctional’ polycarbodiimide, made from IPDI-monomer, of 50% solids in methoxypropyl acetate, wherein ‘multifunctional’ indicates that beside carbodiimide also other reactive functional groups are present, obtainable from Stahl Europe BV), 325 g of butyltriglycol, 266 g of benzyl alcohol and 38 g Cromalent Orange powder (an orange dye of 98% solids, obtainable from Stahl Europe BV).

The ratio dyeing agent/polycarbodiimide based on non-volatile components is 20/100. The amount of polycarbodiimide on total dyeing composition based solely on the non volatile components is 34 wt% The amount of polycarbodiimide on total dyeing composition is 19 wt%, when taking into account also the volatile components. Example 5 Dyeing composition

A dyeing composition is made by adding together and mixing until homogenous of 250 g of XR-5517 (a solventborne polycarbodiimide, made from IPDI-monomer, of 50% solids in methoxypropyl acetate, obtainable from Stahl Europe BV), 220 g of butyltriglycol, 180 g of benzyl alcohol, 50 g of triisobutyl phosphate and 300 g of LD-5924 (a liquid brown dye of 14% solids, obtainable from Stahl Europe BV).

The ratio dyeing agent/polycarbodiimide based on non-volatile components is 34/100. The amount of polycarbodiimide on total dyeing composition based solely on the non volatile components is 29 wt%. The amount of polycarbodiimide on total dyeing composition is 13 wt%, when taking into account also the volatile components.

Example 6 Comparative

A mixture was made analogous to Example 1, but 250 g of demineralized water was used instead of 250 g of XR-5592.

Example 7 Comparative

A mixture was made analogous to Example 2, but 500 g of dipropylene glycol dimethyl ether was added instead of 400 g, and 150 g of demineralized water was used instead of 250 g of XR-5592.

Example 8 Comparative

A mixture was made analogous to Example 3, but 370 g of methoxypropyl acetate was added instead of 370 g of XR-5570.

Example 9 Comparative

A mixture was made analogous to Example 4, but 370 g of methoxypropyl acetate was added instead of 370 g of XR-5570.

Example 10 Comparative

A mixture was made analogous to Example 5, but 250 g of methoxypropyl acetate was added instead of 370 g of XR-5517. Example 11 Dyeing composition

A dyeing composition is made by adding together and mixing until homogenous of 165 g of XR-5592 (a waterborne polycarbodiimide of 40% solids, obtainable from Stahl Europe BV), 145 g of propylene carbonate, 80 g of butyltriglycol, 45 g of benzyl alcohol, 45 g of triisobutyl phosphate, 15 g of acetyl tributyl citrate, 185 g of demineralized water, 35 g of Orotan 731 A ER (a dispersant of 25% solids, obtainable from Dow Chemical) and 285 g of LD- 5915 (a liquid black dye of 13% solids, obtainable from Stahl Europe BV).

The ratio dyeing agent/polycarbodiimide based on non-volatile components is 56/100. The amount of polycarbodiimide on total dyeing composition based solely on the non volatile components is 26 wt%. The amount of polycarbodiimide on total dyeing composition is 7 wt%, when, taking into account also the volatile components.

Example 12 Dyeing composition

A dyeing composition is made by adding together and mixing until homogenous of 165 g of XR-5592 (a waterborne polycarbodiimide of 40% solids, obtainable from Stahl Europe BV), 145 g of propylene carbonate, 80 g of butyltriglycol, 45 g of benzyl alcohol, 45 g of triisobutyl phosphate, 15 g of acetyl tributyl citrate, 175 g of demineralized water, 35 g of Orotan 731 A ER (a dispersant of 25% solids, obtainable from Dow Chemical), 10 g of an aqueous solution of 65% para-toluene sulfonic acid and 285 g of LD-5915 (a liquid black dye of 13% solids, obtainable from Stahl Europe BV).

The ratio dyeing agent/polycarbodiimide based on non-volatile components is 56/100. The amount of polycarbodiimide on total dyeing composition based solely on the non volatile components is 25 wt%. The amount of polycarbodiimide on total dyeing composition is 7 wt%, when, taking into account also the volatile components.

Example 13 Comparative

A dyeing composition is made by adding together and mixing until homogenous of 145 g of propylene carbonate, 80 g of butyltriglycol, 45 g of benzyl alcohol, 45 g of triisobutyl phosphate, 15 g of acetyl tributyl citrate, 350 g of demineralized water, 35 g of Orotan 731 A ER (a dispersant of 25% solids, obtainable from Dow Chemical) and 285 g of LD-5915 (a liquid black dye of 13% solids, obtainable from Stahl Europe BV).

Example 14 Dyeing of leather

Tanned, retanned and fatliquored leather was sponged with a dyeing mixture. The dyed leather was subsequently left to dry at room temperature for at least 24 hours before testing the dyed leather.

Tanned leather was tanned with chrome, or using Granofin Easy F-90, which is an organic -based tanning agent obtainable from Stahl Europe BV, or using glutaraldehyde, or using a mixture of tara extract and chrome.

Dyeing compositions prepared according to Example 1 to 5 were used either freshly prepared or after ageing the dyeing compositions for 24 hours at 50°C. No such ageing discrimination was used for dyeing compositions prepared according to Comparative Examples 6 to 10, because these Comparative Examples do not contain polycarbodiimides, which are the potentially reactive components in the dyeing composition. Dyeing compositions prepared according to Example 11 and 12 were used freshly prepared as well as the dyeing composition prepared according to Comparative Example 13.

See Table 1 below.

Example 15 Colour fastness tests

The dyed leather samples of example 14 were subjected to colour fastness tests according to ISO 11640:2012. These tests involve rubbing a white woollen felt of 15 mm by 15 mm, loaded to a total weight of 1 kg, over a stretched leather surface for several times. The leather and the felt were checked in intervals for changes in colour, and the colour difference was compared with a grey scale. This type of rub fastness tests are often called Veslic tests. The rubbing fastness test was done with wet felt, meaning felt soaked in water, and with dry felt. Reported are the number of rubs that have been done and the colour change according to the grey scale for those numbers of rubs. Less change in colour is better, as well as a higher number of rubs that can be done to arrive at the same change in colour.

The colour change of the felt is visually assessed with grey scales according to ISO 105-A02, with a scale ranging from 5 (best) to 1 (worst).

Table 1 below indicates a discrimination for the tanning system, wherein chrome is indicated for leather that was tanned with chrome, and F 90 is indicated for leather that was tanned using Granofin Easy F-90, which is an organic -based tanning agent obtainable from Stahl Europe BV, and glutaraldehyde is indicated for leather that was tanned using glutaraldehyde, and mix tara & chrome is indicated for leather that was tanned using a mixture of tara extract and chrome.

The table indicates a discrimination for the age of the dyeing compositions of Examples 1 to 5, wherein fresh is indicated when the dyeing composition was used freshly prepared and aged is indicated when the dyeing composition was used after ageing the composition for 24 hours at 50°C.

The table further indicates the colour of the dyeing composition and thus of the obtained dyed leather. The colours used were black, orange and brown.

Besides dyeing compositions from Examples 1 to 5, 11 and 12, and Comparative Examples 6 to 10 and 13, also two commercially available dyeing compositions S Derm Grigio T commercially available from TFL Ledertechnik GmbH and ks TARTUFO commercially available from Kemia Tau srl were used. Table 1

When comparing the scores of the dyeing composition from

Example 1 against Comparative Example 6, it is clear that the number of rubs that the dyed leather can withstand to arrive at the same level of colouring of the felt is higher for leather treated with dyeing composition from Example 1. This is for leathers that were tanned using either chrome tanning or tanning with Granofin Easy F-90.

The same holds for the comparison between leather dyed with dyeing composition from Example 2 against Comparative Example 7, as well as for Example 3 against Comparative Example 8, as well as for Example 4 against Comparative Example 9, as well as for Example 5 against Comparative Example 10. It must be remarked that 500 rubs with a rating of 3-4 is considered significantly better than 150 rubs with a rating of 4, which is the case when considering entries 6 and 19 in Table 1 and entries 20 and 18 in Table 1. In addition, in a comparison of the same types of leather and the same colour applied, the dyeing compositions from Examples 1, 2 and 3 can withstand a larger number of rubs to arrive at the same level of colouring of the felt as for the industry reference of product S Derm Grigio T (obtainable from TFL Ledertechnik GmbH), and the dyeing compositions from Example 4 applied freshly prepared can withstand a larger number of rubs to arrive at the same level of colouring of the felt as for the industry reference of product ks TARTUFO (obtainable from Kemia Tau srl).

Dyeing compositions from Example 11 and Example 12 differ from Dyeing composition from Example 1, because they contain some plasticizer and dispersing agent, and the dyeing composition from Example 12 additionally contains some acidifying agent. The presence of surfactant is beneficial for the colour fastness as well as surprisingly the presence of a plasticizer as the entries in the table demonstrate: entry 25 withstood a larger number of wet rubs to arrive at the same level of colouring of the felt as entry 3, and the same holds for entry 26 versus 6. Entries 29 to 32, when comparing to entries 25 to 28, demonstrate that the presence of additionally acidifying agent results in a lower number of wet rubs that can be withstood. The results from the colour fastness tests demonstrate that the dyeing compositions that contain a polycarbodiimide have a better colour fastness than the corresponding dyeing composition that do not contain a polycarbodiimide.

Example 16 Dyeing composition

A dyeing composition is made by adding together and mixing until homogenous of 250 g of XR-5592 (a waterborne polycarbodiimide of 40% solids, obtainable from Stahl Europe BV), 220 g of butyltriglycol, 180 g of benzyl alcohol, 50 g of triisobutyl phosphate and 300 g of LD-5915 (a liquid black dye of 13% solids, obtainable from Stahl Europe BV).

The ratio dyeing agent/polycarbodiimide based on non-volatile components is 39/100. The amount of polycarbodiimide on total dyeing composition based solely on the non volatile components is 24 wt%. The amount of polycarbodiimide on total dyeing composition is 10 wt%, when taking into account also the volatile components.

Example 17 Dyeing leather in drum process

A full drum process starting from wet blue leather was done, which had first been retanned prior to the dyeing process. The percentages are the weight percentages compared to the weight of the dried leather.

In first step, the washing step, 200% of water of 30°C, 0.5% of Tergolix DA.01 Liq (obtainable from Stahl Europe BV) and 0.5% of 80% aqueous acetic acid were added and the drum was run for 30 minutes, followed by wash overflow and draining the liquid.

In a next step, the neutralization step, 200% water of 25°C and 2% of sodium formate were added and the drum was ran for 20 minutes, after which 1% sodium bicarbonate was added and the drum was ran for another 90 minutes, followed by wash overflow and draining the liquid.

In the next step, the retanning, dyeing and fat liquoring step, 100% of water of 30°C and 3% of Tergotan PR liq (obtainable from Stahl Europe BV) were added and the drum was run for 10 minutes. Subsequently, 4% of Tanicor PW p (obtainable from Stahl Europe BV) was added and the drum was run for 50 minutes. Next, 10% of dyeing composition from Example 16 was added and the drum was run for 60 minutes, followed by the addition of 200% water of 50°C and another 10 minutes of running the drum. Next, 4% of Derminol CFS liq (obtainable from Stahl Europe BV) was added and the drum was run for 60 minutes, followed by the addition of formic acid until a pH of 3.8 was achieved, after which the drum was run for 30 minutes, followed by wash overflow and draining the liquid.

Next step, the drying and conditioning step, was done by drying the leather at ambient conditions while hanging, followed by condition (slight rewet spraying with water), stake (to soften the piece) and toggle (to make it more flat) actions.

Example 18 Dyeing leather in drum process

A full drum process was done starting from leather tanned with Granofin Easy F90 (which is an organic -based tanning agent obtainable from Stahl Europe BV), which had first been retanned prior to the dyeing process. A full drum process starting from leather tanned by Granofin Easy F 90 ( obtainable from Stahl Europe BV) was done and retanned according to the recipe below. The percentages are the weight percentages referred to the weight of the shaved leather. The shave thickness was 1.3 to 1.4 mm.

In a first step, the leathers were washed and pre-retanned. An amount of 200% water of 40°C was added into the drum containing the tanned leathers, and the drum was run for 5 minutes, 0.3% of Tergolix W-01 (obtainable from Stahl Europe BV) and 0.7% of formic acid 85% were added and the drum was run for 30 minutes. The pH of the bath was 3.5. Next, 10% Tanicor SOU (obtainable from Stahl Europe BV) was added and the drum was run for 60 minutes, followed by draining the bath.

Second step is the neutralization step. An amount of 200% water at 40°C was added and next 2% of Tanicor AS 6 liq (obtainable from Stahl Europe BV) and 2% of sodium formate powder were added, and the drum was run for 60 minutes, after which the pH was checked and found to be 5.0 to 5.3. Next, an amount of 250% water at 30 °C was added and the drum was rotated for 10 minutes.

Third step is the pre-fatliquoring step. An amount of 100% water at 30°C was added, then 2% of Derminol NLM liq. (obtainable from Stahl Europe BV) and 2% of Tergotan PO-62 liq. (obtainable from Stahl Europe BV) were added, and the drum was run for 20 minutes, followed by the addition of 8% of Granofin TA powder (obtainable from Stahl Europe BV) and 8% of Tergotan EF liq. (obtainable from Stahl Europe BV). The drum was run for 45 minutes, after which 1% of formic acid 85% was added and the drum was run for 30 minutes. The pH was checked and found to be 3.9. The bath was drained.

Fourth step is a washing step. An amount of 50% of water at 45°C was added and the drum was rotated for 10 minutes, followed by draining the bath.

Fifth step is fatliquoring. An amount of 150% water at 45°C was added into the drum, followed by the addition of 5% of Tergotan PO 62 liq. (obtainable from Stahl Europe BV), 4% of Derminol NLM (obtainable from Stahl Europe BV) and 5% of Derminol CFS liq (obtainable from Stahl Europe BV) and the drum was run for 60 minutes. Next, 1.0% of formic acid 85% was added and the drum was run for 30 minutes. The pH of the bath was found to be 3.7. The bath was drained and an amount of 250% of water at 50°C was added and the drum was run for 10 minutes. The bath was drained and an amount of 250% of water at 20°C was added and the drum was run for 10 minutes. The bath was drained and leathers were horsed up overnight, then put under vacuum at 45°C for 2 minutes, then hang dried at room temperature, conditioned and staked.

From this moment to the end of the process, the percentages are the weight percentages compared to the weight of the dried leather. In the next step, the wetting back step, 200% of water of 35°C and 0.5% of Tergolix SL.01 Liq (obtainable from Stahl Europe BV) was added, and the drum was ran for 10 minutes, 1% of Dermagen DMA liq (obtainable from Stahl Europe BV) was added and the drum was ran for 120 minutes, wherein the pH was 4.2, followed by draining the liquid.

Next, 100% of water at 35°C, 20% of dyeing composition from Example 16 was added and the drum was ran for 60 minutes, followed by the addition of 200% of water of 50°C and another 10 minutes of running the drum, followed by the addition of 1% of formic acid solution (8.5% in water) and the drum was ran for 30 minutes, followed by the addition of 1% formic acid solution (8.5% in water) and the drum was ran for 45 minutes, followed by draining the liquid.

Next, 300% of water at 25 °C was added and the drum was run for 10 minutes, followed by draining the liquid.

Next step, the drying and conditioning step, was done by drying the leather at ambient conditions while hanging, followed by condition, (slight rewet spraying with water), stake (to soften the piece) and toggle (to make it more flat) actions.

Example 19

The obtained leather from Example 17, which was tanned with chrome, and from Example 18, which was tanned without chrome, were evaluated on light fastness according to IUF 402 and perspiration according to IUF 426.

IUF 402 is to determine the resistance of the colour of leather to the action of an artificial light source, by exposing to xenon arc under prescribed conditions, along with eight dyed wool standards. The fastness is assessed by comparing the fading of the leather with that of the standards. The scores range from 1, which is very low light fastness, to 8, which is very high light fastness. IUF 426 is to determine the resistance of the colour of leather to the action of an artificial perspiration solution, by pressing a specified textile, wetted with artificial perspiration on the leather for a specified time and an appropriate apparatus. The change in colour of the leather and the staining of the textile are assessed with standard Grey scale, where 5 is the best score and 1 the worst score.

N : Change in shade of leather;

Co : staining on Cotton; Wo : staining on Wool

Example 20 Dyeing composition

A dyeing composition is made by adding first 2 g of Coriacide RED 2B (a solid, metal-free, red dye, obtainable from Stahl Europe BV) to 20 g of water, which was mixed during 5 minutes, after which 1 g of XR-5592 (a waterborne polycarbodiimide of 40% solids, obtainable from Stahl Europe BV), 1 g of dipropylene glycol dimethyl ether was added, followed by mixing for 20 minutes.

The ratio dyeing agent/polycarbodiimide based on non-volatile components is 500/100. The amount of polycarbodiimide on total dyeing composition based solely on the non volatile components is 17 wt%. The amount of polycarbodiimide on total dyeing composition is 1.7 wt%, when taking into account also the volatile components. Example 21 Comparative

A dyeing composition is made by adding first 2 g of Coriacide RED 2B (a solid, metal-free, red dye, obtainable from Stahl Europe BV) to 20 g of water, which was mixed during 5 minutes, followed by mixing for 20 minutes.

Example 22 Dyeing composition

A dyeing composition is made by adding first 3 g of Coriacide BLUE RF (a solid, metal-free, blue dye, obtainable from Stahl Europe BV) to 20 g of water, which was mixed during 5 minutes, after which 4 g of XR-5592 (a waterborne polycarbodiimide of 40% solids, obtainable from Stahl Europe BV), 4 g of dipropylene glycol dimethyl ether was added, followed by mixing for 20 minutes.

The ratio dyeing agent/polycarbodiimide based on non-volatile components is 187/100. The amount of polycarbodiimide on total dyeing composition based solely on the non volatile components is 35 wt%. The amount of polycarbodiimide on total dyeing composition is 5 wt%, when taking into account also the volatile components.

Example 23 Comparative

A dyeing composition is made by adding first 3 g of Coriacide BLUE RF (a solid, metal-free, blue dye, obtainable from Stahl Europe BV) to 20 g of water, which was mixed during 5 minutes followed by mixing for 20 minutes.

Example 24 Dyeing leather in drum process

A full drum process was done starting from leather tanned with Granofin Easy F90 (which is an organic -based tanning agent obtainable from Stahl Europe BV), which had first been retanned prior to the dyeing process following below described process.

The percentages are the weight percentages referred to the weight of the shaved leather. The shave thickness was 1.1 mm.

In a first step, the leathers were wetted back. An amount of 250% water of 30°C was added into the drum containing the tanned leathers, and the drum was run for 5 minutes, and 0.5% of Prospread (obtainable from Stahl Europe BV) was added and the drum was run for 30 minutes, followed by draining the bath.

Second step is the retanning step. An amount of 200% water at 45°C was added and next a 1:4 aqueous dilution of 6% of Catalix 150 liq. (obtainable from Stahl Europe BV) 45°C ) was added and the drum was run for 30 minutes. Next, 3% of Coralon OT (obtainable from Stahl Europe BV) powder was added and the drum was run for 5 minutes, followed by the addition of a 1:4 aqueous dilution of 6% of Tergotan RE 5021 (obtainable from Stahl Europe BV) at 45 °C. The drum was run for 15 minutes, followed by the addition of 12% of Basyntan DLX-N p. (obtainable from Stahl Europe BV) and 6% of Granofin TA p. (obtainable from Stahl Europe BV) and the drum was run for 90 minutes, followed by draining the bath. An amount of 100% water of 30°C was added into the drum and the drum was run for 5 minutes. Next, 1% of Prospread (obtainable from Stahl Europe BV) was added and the drum was run for 5 minutes. Next, a 1:4 aqueous dilution of 3% of Tergotan RE 5021 (obtainable from Stahl Europe BV) at 45°C was added and the drum was run for 15 minutes. Next, 3% of Derminol OCS (obtainable from Stahl Europe BV), 6% of Derminol NLM (obtainable from Stahl Europe BV) and a 1:4 aqueous dilution of 6% of Stahlite RDT (obtainable from Stahl Europe BV) at 55°C were added and the drum was run for 60 minutes. Next, a 1:4 aqueous dilution of 3% of Catalix 150 (obtainable from Stahl Europe BV) at 45°C was added and the drum was run for 30 minutes. Next, 15% of a 8.5% aqueous solution of formic acid 85% was added and the drum was run for 30 minutes, followed by draining the bath.

The bath was drained and an amount of 200% of water at 50°C was added and drum was run for 5 minutes. The bath was drained and leathers were hang dried at room temperature and conditioned.

From this moment to the end of the process, the percentages are the weight percentages compared to the weight of the dried leather. In the next step, the wetting back step, 1000% of water of 30°C was added, and the drum was ran for 180 minutes, wherein the pH was 5, followed by draining the liquid.

A mixture from Example 20 was added in an amount of 24% together with an amount of 180% of water and the drum was ran for 60 minutes. Then 600% of water of 50°C was added, and the drum was ran for 10 minutes, followed by the addition of 2% formic acid solution (8.5% in water) and the drum was ran for 60 minutes, followed by draining the liquid. The leather was washed, dried by hanging and conditioned.

Example 25 Dyeing leather in drum process - comparative

Same process as in Example 24 was followed, except that a mixture from comparative Example 21 was added in an amount of 22% instead of a mixture from Example 20 in an amount of 24%.

Example 26 Dyeing leather in drum process

Same process as in Example 24 was followed, except that a mixture from Example 22 was added in an amount of 31% instead of a mixture from Example 20 in an amount of 204%.

Example 27 Dyeing leather in drum process - comparative

Same process as in Example 24 was followed, except that a mixture from comparative Example 23 was added in an amount of 203% instead of a mixture from Example 20 in an amount of 24%.

Example 28 - Evaluation and comparison of dyed leathers from Examples 24 and 26 versus Comparative Examples 25 and 27

The leather from Example 24 was more even, defects were very well covered and the intensity of the dyeing was almost 15% higher than the reference from Comparative Example 25. The intensity difference of 15% was a visual estimation.

The leather from Example 26 was more even, defects were very well covered and the intensity of the dyeing was almost 25% higher than the reference from Comparative Example 27. The intensity difference of 25% was a visual estimation.

Example 29 Dyeing composition

Same process as in Example 22 was followed, except that Luganil Yellow G (a solid, metal-free, yellow dye, obtainable from Stahl Europe BV) was used as dye instead of Coriacide BLUE RF.

Example 30 Comparative

Same process as in Comparative Example 23 was followed, except that Luganil Yellow G (a solid, metal-free, yellow dye, obtainable from Stahl Europe BV) was used as dye instead of Coriacide BLUE RF.

Example 31 Dyeing composition

Same process as in Example 22 was followed, except that Coriacide Red 2B (a solid, metal-free, red dye, obtainable from Stahl Europe BV) was used as dye instead of Coriacide BLUE RF.

Example 32 Comparative

Same process as in Comparative Example 23 was followed, except that Coriacide Red 2B (a solid, metal-free, red dye, obtainable from Stahl Europe BV) was used as dye instead of Coriacide BLUE RF.

Example 33 Dyeing leather in drum process

Same process as in Example 26 was followed, except that a dyeing composition from Example 29 was used instead of a dyeing composition from Example 22.

Example 34 Dyeing leather in drum process - comparative

Same process as in Example 33 was followed, except that a dyeing composition from comparative Example 30 was added instead of a dyeing composition from Example 29.

Example 35 Dyeing leather in drum process

Same process as in Example 26 was followed, except that a dyeing composition from Example 31 was used instead of a dyeing composition from Example 22. Example 36 Dyeing leather in drum process - comparative

Same process as in Example 35 was followed, except that a dyeing composition from comparative Example 32 was added instead of a dyeing composition from Example 31.

Example 37 - Hot-Xenon exposure comparison of dyed leathers from Examples 33 and 35 versus Comparative Examples 34 and 36.

Pieces of leather from Examples 33 and 35 and Comparative Examples 34 and 36 were subjected to Hot Xenon test for 72 hours, according to ISO 105-B02 to assess the light fastness, wherein the colour change of the leather was visually assessed with grey scales, with a scale ranging from 5 (best) to 1 (worst).

Leather from Examples 33 and 35 obtained a score of 3 after Hot Xenon testing, whereas Comparative Examples 34 and 36 obtained a score of 2 after Hot Xenon testing. This demonstrates the better light fastness obtained by using the dyeing compositions of the invention.

Example 38 Dyeing composition

Same process as in Example 22 was followed, except that Melioderm HF Dark Brown R (a solid, anionic metal complex of chrome and iron, brown dye, obtainable from Stahl Europe BV) was used as dye instead of Coriacide BLUE RF.

Example 39 Comparative

Same process as in Comparative Example 23 was followed, except that Melioderm HF Dark Brown R (a solid, anionic metal complex of chrome and iron, brown dye, obtainable from Stahl Europe BV) was used as dye instead of Coriacide BLUE RF.

Example 40 Dyeing composition

Same process as in Example 22 was followed, except that Coriacide Black AF 135 (a solid, metal-free, black dye, obtainable from Stahl Europe BV) was used as dye instead of Coriacide BLUE RF. Example 41 Comparative

Same process as in Comparative Example 23 was followed, except that Coriacide Black AF 135 (a solid, metal -free, black dye, obtainable from Stahl Europe BV) was used as dye instead of Coriacide BLUE RF.

Example 42 Dyeing leather in drum process

Same process as in Example 26 was followed, except that a dyeing composition from Example 38 was used instead of a dyeing composition from Example 22.

Example 43 Dyeing leather in drum process - comparative

Same process as in Example 42 was followed, except that a dyeing composition from comparative Example 39 was added instead of a dyeing composition from Example 38.

Example 44 Dyeing leather in drum process

Same process as in Example 26 was followed, except that a dyeing composition from Example 40 was used instead of a dyeing composition from Example 22.

Example 45 Dyeing leather in drum process - comparative

Same process as in Example 44 was followed, except that a dyeing composition from comparative Example 41 was added instead of a dyeing composition from Example 40.

Example 46 - Evaluation and comparison of dyed leathers from Examples 42 and 44 versus Comparative Examples 43 and 45

The leathers from Examples 42 and 44 were more even, defects were better covered and showed better penetration than the references from Comparative Examples 43 and 45, respectively.