GB2192199A - Penetration dyeing of leather with basic dyes - Google Patents

Abstract

Leather is dyed with basic dyes, and optionally with anionic dyes, in the presence of a retanning agent as dyeing and penetration assistant; a fatting may be carried out in the same bath; an after-treatment with a cationic dyeing assistant may also be carried out in the same bath.

Description

SPECIFICATION Leather dyeing The invention relates to a process for the penetration dyeing of leather with basic dyes in the presence of particular compounds as dyeing assistants.

Thus the invention provides a process for the penetration dyeing of tanned leather from an aqueous medium in the presence of a dyeing assistant, wherein the leather is dyed with a basic dye (B) and the dyeing assistant is a retanning agent (H).

Any kind of tanned leather commonly used as a substrate for dyeing from aqueous media may be used for the process of the 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 nubuk leather; further also wool-bearing skins and furs (e.g. fur-bearing suede leather). The leather may have been tanned by any usual tanning method, in particular vegetable, mineral, synthetic or combined tanned (e.g. chrome tanned, zirconyl tanned, aluminium tanned or semichrome tanned).If desired, the leather may also be retanned and/or fatted; for retanning, there may be used any tanned agent conventionally employed for retanning, e.g. mineral, vegetable or synthetic tanning agents [e.g. chromium, zirconyl or aluminum derivatives, oak, quebracho, chestnut or mimosa extract, aromatic syntanes, polyurethanes, copolymers of (meth)acrylic acid compounds or melamine, dicyanodiamide and/or urea/formaldehyde resins]. Leather retanned with any conventional retanning agent may be used with advantage for the process of the invention, vegetable and synthetic retanning agents being preferred. Preferably the leather (in particular chome-tanned leather) is retanned with up to 25% by weight, more preferably 2-20% by weight of retanning agent, based on the wet weight of the leather.

Before dyeing the leather may also be fatted, and for this purpose any conventional anionic, cationic, non-ionic or combined fatting agents may be employed, in particular such as are commonly applied from aqueous media, e.g. animal, vegetable or mineral fats, oils, resins or waxes and their chemical modification products, e.g. hydrogenation, oxidation, saponification or sulphonation products of animal and vegetable fats and oils or chlorination and/or sulphonation products of mineral fats or oils and synthetic fatting agents, e.g. esters of polybasic acids in particular phosphoric acid with optionally oxyethylated fatty alcohols. By the term "sulphonation" is meant generally the introduction of a sulpho group including also the formation of a sulphato group (="sulphating") and the introduction of a sulpho group by reaction with a sulphite or SO2 (="sulphiting").Such fatting agents are described in part e.g. in F. Stather, "Gerbereichemie und Gerbereitechnologie", Akademieverlag Berlin, 1967, 4th edition, in chapter 21 on pages 517-535. For fatting it is preferred to use fat liquor emulsions in which the fat liquor is emulsified by means of an emulsifier and/or by chemical modification. The emulsifiers may be non-ionic, anionic or cationic, depending on the fatting agent, and are also well known in the art; they are in part described for example in the above mentioned publication of Stather. If the leather is fatted before the dyeing process of the invention, it is preferred to use a non-ionic or more preferably an anionic fat-liquor (preferably wherein at least some of the fatting agent and/or of the optionally present emulsifier contains a sulpho group and/or a carboxy group).The fatting agents and emulsifiers mentioned in the above publication of Stather are incorporated herein by reference. Particularly worth mentioning are the saponification and/or sulphonation products of tallow, train oil, neat's foot oil, olive oil, castor oil, rape seed oil, linseed oil, coconut oil, wood oil, cottonseed oil, sesame oil, corn oil and Japanese tallow and their mixtures with non-modified fats or oils and/or with woolfat, beeswax, ceresin, mineral oil or optionally sulphonated paraffins.

The leathers may be of various thicknesses, thus there may be used very thin leathers such as bookbinders' leather or glove leather (nappa), leather of medium thickness such as shoe upper leather, garment leather and leather for handbags or also thick leathers such as shoe sole leather, furniture leather, leather for suitcases, for belts and for sport articles; hair-bearing leathers and furs may also be used.After tanning and before the dyeing process of the invention the pH of the leather is advantageously set to values in the range of 4 to 8 (the leather is "neutralized"); depending on the thickness of the leather and on the compactness of its fibrous structure, there may be chosen an optimum pH-range, mainly as follows: for grain leather and thick leathers (such as nubuk) pH-values in the range of 4 to 6; for suede leathers, split velours and for very thin leathers pH-values in the range of 4,5 to 6,5; for intermediately dried suede leathers and intermediately dried split velours, the pH-values may range in the scope of 5 to 6,5. Preferably the pH-range is kept at neutral to weakly acidic values, more preferably within the range of 4,5 to 6.For the adjustment of the pH-value of the leather, there may be employed conventional assistants; for tanned leather of acidic character the pH may be adjusted by addition of suitable bases, e.g. ammonia or ammonium bicarbonate or alkali metal salts of weak acids, e.g. sodium formate, sodium acetate, sodium bicarbonate, sodium carbonate or sodium bisulphite or buffer salts, e.g. mono- or dialkali metal salts of polybasic acids, in particular phosphoric acid, e.g. mono- or disodium or -potassium hydrogen phosphate of which sodium formate and ammonium bicarbonate are preferred. Sodium bicarbonate and the buffer salts are usable in particular as second bases for the exact adjustment of the superficial pH-value of the leather. For any retanning step, the pH is kept preferably in the range of 4 to 6.5.If desired, mineral tanned leather may also be masked, e.g. with alkali metal formate, oxalate or polyphosphate or e.g. with titanium/potassium oxalate.

Where retanning and/or fatting is carried out the strict sequence of the steps: neutralisation and re-tanning or of the steps: fatting and dyeing is not critical. Thus, fatting may be carried out in one or more steps and may take place before and/or after the dyeing; and retanning may comprise a further neutralisation and/or masking (depending on the retanning agent). If wet leather is fatted in the process of the invention at least one fatting step is advantageously carried out after the dyeing; the above mentioned fatting agents may be used for this purpose.

The retanning agents (H) which are used as dyeing assistants, in particular as penetration assistants, according to the invention may be any conventional, preferably anionic substances as employed as main substances and/or preferably as auxiliary in the retanning of tanned leather.

These substances are described e.g. in "Bibliothele des Leders", vol. 3 ("Gerbmittel, Gerbung und Nachgerbung"), ed. by Hans HERFELD or in "Journal of the Society of Leather Technologists and Chemists", vol. 64, page 16 ff. in the article of Samir DAS GUBTA "Some thoughts on standardisation of synthetic tanning materials". The retanning agents (H) that are to be employed as dyeing assistants according to the invention are preferably semi-synthetic or synthetic.

As semi-synthetic retanning agents there may be mentioned sulphonated lignines and their salts (sodium, chromium and/or calcium salts) and polypeptides including degradation products of tanned leather fibres (optionally containing mineral tanning agent, in particular chrome tanning agent).

As purely synthetic retanning agents there may be mentioned aromatic syntanes: preferably sulphonated oligophenylenes or sulpho-group-containing derivatives of naphthalene and/or of phenol that may contain methylene, sulphonyl or ether bridges, in particular condensation products of diphenylether sulphonic acid, condensation products of sulphonaphthalene with formaldehyde, condensation products of dihydroxydiphenylenesuiphone with formaldehyde and with a further compound contaning sulpho groups, preferably fi-sulpho-naphthalene or diaryletherdisulphonic acid (mainly diphenylether disulphonic acid), condensation products of disulphodiarylethers with formaldehyde or condensation products of oligophenylenesulphonic acid with formaldehyde.These products are preferably in the form of salts in particular alkali metal, earth alkali metal and optionally also chromium salts (chrome syntanes).

The above products may be employed as single substances or also as mixtures of different substances. In the mixtures sulphonated lignines and their salts are preferably mixed with other substances, e.g. with polypeptides or with purely synthetic sulpho group containing aromatic syntanes as listed above.

In the dyeing process of the invention the sulpho-group-containing aromatic derivatives indicated above are preferred, of which the ones that do not contain any -SO2- bridges between aromatic rings are particularly preferred. Particularly worth mention are oligophenylene sulphonic acids, lignine sulphonates, condensation products of formaldehyde with napthalene sulphonic acid, condensation products of formaldehyde with diaryl ether sulphonic acid and mixtures of lignine sulphonates with oligophenylene sulphonic acids, with condensation products of formaldehyde with naphthalene sulphonnic acid or diarylether sulphonic acid or with polypeptides as indicated above or in particular also corresponding chrome syntanes.

The basic dyes (B) may be in general any conventional in particular hydrosoluble dyes with basic or cationic character e.g. as defined in the "Colour Index" under the denomination "basic dyes". The basic dyes usable according to the invention may belong to any subgroup and include anthraquinone, azo (in particular mono- or disazo), azomethine, hydrazone, oxazine, naphtholactam, triphenylmethane, styryl and/or pyridone and metal complexes (e.g. of metallisable azo or azomethine components or of phthalocyanines). The dyes preferably have an average of 1-4 cationic groups in the molecule; the metal free basic dyes preferably have 1-2, more preferably 1.3-2 cationic groups, and the metal complexes preferably have 1-4, more preferably 1.5-4 cationic groups on the average per dye molecule.The dyes described in European patent application 41040 Al [in particular as defined in formulae (III) and (IV)] and in European patent application 92520 A2 [in particular as defined in formula (II) preferably with a radical of formula (aa7) in the molecule] are incorporated herein by reference. The basic dyes (B) used according to the invention may be single dyes or also mixtures of basic dyes, in particular mixtures of dyes with similar tinctorial behaviour and optionally different shade (e.g. for trichromatic dyeings).

Mixtures of basic dyes having different tinctorial behaviour (e.g. differing in affinity, penetration capability and levelling capability) may also be used, however, since the dyeing assistant (H) may also display a balancing effect on such mixtures.

The dyeing assistant (H) used according to the invention is added suitably so that it is efficiently present in the same bath as dye (B). Although it is possible to combine the dyeing process of the invention with a retanning step by adding the dye to the retanning bath before conclusion of the retanning, it is preferred to conclude any retanning before carrying out the dyeing of the invention. Preferably retanning is carried out in a separate bath or, if the bath is not drained off, retanning is carried out until practically all of the retanning agent has built-up on the substrate and only then components (H) and (B) of the invention are added.

If the retanning agents (H) that are used according to the invention as dyeing assistants are of anionic character, they are suitably added to the bath in such a way that no undesired secondary effects occur, in particular no precipitation together with (B). The following alternatives are preferred: -(H) is not added to the dye bath simultaneously with (B). The time interval between the two additions is advantageously at least 21 minute, preferably 2 minute to 30 minutes, more preferably 1-20 minutes, in particular up to 15 minutes, if (B) is added after (H); or 2 minute to 90 minutes, preferably 30 minutes, more preferably 1-20 minutes, in particular up to 10 minutes if (H) is added after (B).If (H) is added after (B) it is in particular of advantage to keep a time interval of at least 3 minutes between the two additions.

-(H) is added simultaneously with (B). In this case it is preferred to add (H) and (B) in the form of anhydrous substances or preparations (preferably powder or granulate) or (B) is combined, before the addition to the bath, with an excess of (H) to give a composition readily dilutable with water.

Preferably (B) is added after (H), advantageously when (H) has not yet built-up completely and irreversibly on the substrate.

According to a particularly preferred way of working (B). is added to the bath at a time interval as short as possible after the addition of (H) suitably as soon as (H) has distributed homogenously (dissolved or dispersed) in the liquor. Particularly with the preferred anionic retanning agents (H) this time interval may be very short, e.g. of 1-10 minutes, in particular of 1-5 minutes. After a time interval of at least 2 minutes or even only one minute the retanning agents (H) are already so well distributed in the liquor in the drum (or also in the paddle) that the dye (B) may already be added.

According to a particular aspect of the invention an anionic dye is also added to the same dyebath, the basic and anionic dyes being suitably added in such a way that their build-up on the substrate is not exactly simultaneous.

Thus, the invention provides also a process for the dyeing of tanned leather from an aqueous medium, wherein an anionic dye (A) and a basic dye (B) are added to the dyebath in any desired sequence, a retanning agent (H) being used as dyeing assistant.

The anionic dyes (A) may be in general any conventional in particular hydrosoluble dye with anionic character suitable for the dyeing of leather, including azo dyes, azomethine dyes, metal complexes of azo dyes and/or azomethine dyes, formazane dyes, polycyclic dyes optionally containing heterocycles (e.g. dyes of the anthraquinone, quinoline, oxazine, thiazine, dehydrothiotoluidine, cumarine or indole series), phthalocyanines, stilbene dyes or sulpho group containing sulphur dyes (in particular so-called Bunte-salts as defined e.g. in VENKATARAMAN "The Chemistry of Synthetic Dyes", vol. VII, 1974, Academic Press, in chapter II on pages 35-68), and anionic dyes as defined in the "Colour Index" under the denominations "Acid Dyes", "Direct Dyes", "Mordant Dyes", "Reactive Dyes", "Solubilised Sulphur Dyes", "Condense Sulphur Dyes" and "Leather Dyes" and is particularly described therein. Mixtures of anionic dyes, in particular mixtures of anionic dyestuffs with similar tinctorial behaviour and optionally different shade (e.g. for trichromatic dyeings) may also be employed. Mixtures of anionic dyes having different tinctorial behaviour (e.g. differing in affinity, penetration capability and levelling capability) may also be used, however, since the dyeing assistant (H) used according to the invention may display a balancing action on such mixtures.

The dyes (A) and (B) are added advantageously in such a way that they do not act exactly simultaneously on the substrate, i.e. they are either not added simultaneously to the dye bath or, if added simultaneously they are added in such a way that they do not distribute at the same rate into the liquor. The retanning agent (H) used according to the invention as dyeing assistant is suitably added in such a way that it can fully display its action as a dyeing assistant, in particular as a penetration assistant; preferably it is added at any desired time before the addition of the first dye up to at latest simultaneously with the addition of the second dye. The retanning agent (H) may, for instance, be added to the dye bath before the addition of the first dye or between the two dye additions or it can be added together with one of the two dyes (A) or (B).If (A), (B) and (H) have to be added together contemporarily they are preferably all in dry solid form (in particular in the form of powder or granulate).

Suitably the dyes (A) and (B) are added so that the second is added at a time when the first has not yet built up completely on the leather, preferably so that the second dye is added when the retanning agent has not yet built up completely and irreversibly on the substrate. Components (A), (B) and (H) may be added, e.g. according to the following alternative sequences: 1) A-H-B 2) (A+H)-B 3) A-(H+B) 4) H-A-B 5) H-B-A 6) (H+B)-A 7) B-H-A 8)- B-(A+H) 9) (A+H+B) (the sign "+" signifies the contemporary addition and the sign - signifies the addition in the indicated sequence with insertion of a time interval).In the alternatives 3) and 6) the mixture (H+B) is an anhydrous mixture of solid products and in alternative 9) (A+H+B) is a mixture of solid anhydrous substances. The dyeing assistant (H) is added preferably before the addition of dyes of very high affinity for the substrate (in particular cationic dyes); it may, however, be advantageously added to the liquor also contemporarily with anionic dyes. Preferably the addition of components (A), (H) and (B) takes place in two or three steps, i.e. according to alternatives 1) to 8) of which the alternatives 1) to 5) and in particular 1), 2), 4) and 5) are preferred. Of these the alternatives 1) and 2) are preferred alternative 2) being particularly preferred by reasons of process economics.

The time intervals between the different additions may be different and are suitably such that the retanning agent (H) can exert maximum influence on the behaviour of the dyes (A) and (B) especially on their build-up. The time intervals between the different additions may be advantageously in the range of 2 to 20 minutes, preferably 1-10 minutes, more preferably 1-5 minutes.

The concentration of the retanning agent (H) is, suitably, at least sufficient to influence the behaviour of the dyes and at most such that the build-up capability of the dyes is not impeded too much. The concentration of (H) is advantageously at least 1%, preferably 1-8%, more preferably 2-6%, in particular 3-5%, referred to the wet weight of the leather. For hair-bearing skins there are employed corresponding amounts of (H), i.e. at a liquor to goods ratio of e.g.

2000% with reference to the dry weight of the skin, preferably up to 6g/1 of (H), in particular 3-6g/i of (H).

The total dye concentration may vary broadly depending on the substrate, the dyeing method, the dye combination and the desired colouristic effect and may range, if desired, up to the saturation level of the substrates. The total amount of dye is advantageously from 0.02-4%, based on the wet weight of the substrate (i.e. about 0.04-8%, based on the dry weight of the substrate, e.g. for hair-bearing skins where, however, also the possible dyeability of the hair portion is to be considered).

The weight ratio of components (A) and (B) may also vary broadly e.g. depending on the substrate, the affinity, the shade and depth of the dyeing, the desired effect and the dyeing method. The weight ratio (A)/(B) ranges, advantageously from 1:20 to 20:1, preferably from 1:4 to 4:1. If desired, the dyeing liquor may contain further conventional assistants.

The dyeing may be carried out under conventional temperature and pH conditions, advantageously in the temperature range of 10-70"C, preferably 25-70"C, the temperature range of 35-55"C being preferred for leather dyeings and milder temperature conditions, in particular temperatures in the range of 25-55"C being preferred for the treatment of wooled skins. The pH values are advantageously within the range of 2-8, preferably of 3-7. The treatment with the dyeing assistant (H) and the dyes (B) or (A) and (B) takes place preferably in the pH range of 4-6.5 and to conclude the dyeing procedure the pH of the dye bath is preferably lowered by acid addition, advantageously to pH-values from 3 to 5, preferably at pH-values c4, in particular in the range of 3.3-4 for fixation.Any conventional acids may be used for this purpose, e.g.

acetic acid or preferably formic acid. After the addition of the components (H), (B) and optionally (A) and before any final addition of acid the treatment of the substrate in the dye bath is continued until the desired penetration is achieved. The optimum dyeing duration for a given combination of substrate, dyes, assistant and dyeing method may be assessed by a few preliminary tests and is for instance within 15 and 120 minutes, normally within 30 and 90 minutes. The dyeing process may be carried out according to any conventional dyeing methods, e.g. in the dyeing drum, in mixers such as Challenge Cook, Coretan or Hagspiel or also in a paddle.

Before any acid addition the dyed substrates may be fatted or fat-liquored. After conclusion of the dyeing procedure including any fatting or fat-liquoring and any acid addition, the substrate may be washed or rinsed with water and, after drying, finished as usual. If desired the treated leather may be subjected to subsequent treatments, thus it may be fatted, hydrophobised or finished with a resilient polymer-coating or gloss topping.

According to a particular aspect of the invention fatting is carried out in the same bath, in particular after dyeing and before any acid addition. Any conventional leather fatting agents, in particular fat-liquoring agents, e.g. as described above, are suitable. The concentration of the fatting agent or fat-liquoring agent (calculated as dry substance, referred to the wet weight of the substrate) is in the usual range, mainly within 1 and 10%, preferably within 2 and 8%, more preferably between 4 and 8%. In this way the dyeing process may be combined in the same bath with a fatting process so that a separate, later fatting step is unnecessary. Preferably an anionic fat-liquoring agent is used. If wet leather is employed in the process of the invention it is of advantage to fat-liquor also or only after the dyeing.The fatting agent (in particular the fatliquoring agent) is added advantageously after an interval of 5-90 minutes, preferably 20-60 minutes after the only or the second dyestuff addition. The duration of the fatting resp. fatliquoring treatment may be as conventional, preferably 15-90 minutes. After the fatting it is of advantage to iower the pH value to the above mentioned values of 3-5, preferably < 4, in particular 3.3-4 (preferably by addition of formic acid), mainly in order to fix the dyeing. After the addition of the acid the substrate may be further treated as indicated above.

According to a further variation of the process of the invention it is possible to further dye the already dyed and fixed substrate by further addition to dye (A) or (B) in the same bath after which, if required, the pH may again be corrected to values of 3-5, preferably < 4, in particular 3-4. The fatting may also be carried out after this later dyeing but before any final pH lowering; if a later dyeing is carried out it is, however, preferred to fat or fat-liquor between the main dyeing and the later dyeing.

According to a further particular aspect of the invention the dyed substrates are after-treated with a cationic dyeing assistant (K) in the same bath in which the dyeing and any fatting has been carried out. The cationic dyeing assistants (K) may be any conventional hydrosoluble or hydrodispersible, essentially colourless dyeing-assistants employed in the dyeing of textiles or leather with hydrosoluble dyes. The cationic dyeing assistants (K) that come into consideration are mainly amino compounds and these may be quaternary ammonium compounds or also nonquaternised amines that form ammonium ions in aqueous, in particular acidic medium.

The amino compounds that are to be used as (K) comprise mainly aliphatic mono- or polyamines (e.g. polymethylenediamines with 2-6 methylene groups in the polymethylene bridge or polyalkylene-polyamins in which alkylene contains 2-4 carbon atoms and containing 3-6 amino groups, or cyclic amines) which may bear one or more Cg 24-aliphatic hydrocarbon radicals and which optionally may be benzylated and/or alkylated with C, 4-alkyi radicals, e.g. as described in DE-A 25 08 242, 29 24 471 and 35 34 102; or basic nitrogen atom-containing reaction products of such mono- or polyamines with cyanamide, dicyanodiamide, guanidine, biguanide, epichlorohydrine, formaldehyde, dicarbonic acids and/or methylolated nitrogen-compounds and optionally with alkylating agents or further reactants as described e.g. in DE-A 32 16 913 and 34 46 284, in the PCT specification 81-2423 and in EP 151 370 A2: or amino group containing guanyl compounds as described in British Patent 1 238 091; or also aromatic amino compounds. The cationic compounds (K) may optionally be blended with conventional additives, in particular with non-ionic, preferably hydrophilic dispersing agents (in particular for the production of aqueous dispersions of correspondingly dispersed amino compounds).As examples of such cationic dyeing assistants (K) there may be mentioned those identified in the above patent and patent applications or also methylolated melamine, condensation products of di-(C, 2-alkyl)amine with epichlorohydrine (0.9:1 to 5:4) and aminobenzoic acid benzylester (alcoholic solution).

The after-treatment of the dyeings with the cationic dyeing assistants (K) is carried out in the same bath as the dyeing and any optional after-dyeing, advantageously under acidic pH conditions, preferably at 3-5, more preferably at pHc4, in particular at pH 3.3-4. Preferably (K) is added to the dye bath when the liquor after the dyeing (if a fatting or fat-liquoring agent has been added, also after the addition of this fatting agent and, if an after-dyeing has been carried out, also after the after-dyeing) has been acidified to the above indicated pH-values, preferably at pH-values < 4, in particular at pH-values in the range of 3.3-4. The cationic after-treatment agent (K) is employed advantageously in a concentration of 0.1-2%, preferably 0.2-1%, calculated as cationic compound, based on the wet weight of the substrate.The after-treatment is carried out advantageously in the same temperature range as the dyeing, the optional fatting and any optional lowering of the pH-value by acid addition, preferably at 25-70"C, in particular 35-55"C for leather and 25-55"C for hair-bearing skins.

By this after-treatment there can be achieved a surprisingly good exhaustion of the dye-bath.

After this after-treatment the treatment substrate may be washed or rinsed with water as usual and, after the drying, finished in the usual way and if desired further treated as indicated above.

Colour-yield, dyestuff-penetration and fastnesses, brillancy and levelness of the so-obtained leather dyeings are surprisingly good. By the addition of all the treating substances [i.e. of the assistant (H), of the dyes (B) and optionally (A), optionally of a leather-fatting agent and preferably of a cationic after-treatment agent (K)] in one bath the dyeing process can be carried out in a particularly rational and simple way.

The grain may be dyed very regularly and with practically no bronzing effect, even at relatively high dyestuff concentrations. By suitable choice of the components (A, (B) and (H) their concentration and the sequence of the additions, widely varying colour effects may be obtained. By the choice of dyes or dye-mixtures (A) and (B) of the same shade, there may be obtained very regularly dyed leathers and by means of components (A) and (B) of different shade there may be obtained, if desired, also penetration dyeing and grain dyeing of different shades. By the dyeing of wooled skins (or furs) there may be also achieved particular colour effects of hair side and leather side.

According to the invention it is possible to dye leather, in particular also thick and very thick leathers (in particular such of a thickness of at leat 1.0mum) very well and in high yield and penetration.

In the following examples parts and percentages are by weight; the temperatures are indicated in degrees Celsius; the concentrations indicated in percent refer, if not otherwise indicated, to the wet weight of the substrates, unless thay do not refer clearly to the concentration of a solution or a dispersion. The products used are commercial products and their concentrations refer, if not otherwise indicated, to the active substance. If not otherwise indicated, the dyeings are drum-dyeings.

Example 1 Chrome-tanned cow leather of 2 mm thickness, the pH of which is adjusted to 4.5, is retanned in a fresh bath at 40 with 100% of water and 4% of mimosa extract. After 45 minutes of drum-rotation 5% fat-liquor (sulfited fish oil) are added to the same bath; after a further 45 minutes 5% polycondensate of formaldehyde with fi-naphthalene sulfonic acid (molar ratio 3/4) are added; after further 5 minutes of drum-rotation 2% of the brown dye of example 157 of EP 41040 Al are added and dyeing is continued for 1 hour. Then 2% of 85% formic acid is added in 3 additions at 10 minutes intervals. 30 minutes after the last addition the pH of the bath is 3.3. Then the dyed leather is rinsed, drained, dried and cured as usual.The treated leather is optimally penetration-dyed in high yield in a brown shade and the dyeing is of optimum fastnesses.

Example 2 Chrome-tanned cow leather of 2mm thickness, the pH of which is adjusted to 4.5, is given into a fresh bath of 100% water of 40"C and 2% of the basic dye C.l. Basic Blue 3 and dyeing is continued for 1 hour. After this time 5% of the same penetration assistant as in example 1 are added and the treatment is continued for 1 hour. Then in the same bath the leather is fatted with 5% sulfited fish oil and after 45 minutes 2% of 85% formic acid are added in 3 additions at intervals of 10 minutes; 30 minutes after the last addition the pH of the bath is 3.3. Now the leather is rinsed, drained, dried and cured as usual. The obtained leather is optimally penetration dyed in a blue brillant shade of optimum fastnesses and in optimum colour yield.

Example 3 Example 2 is repeated with the difference that the penetration assistant is added 5 minutes (instead of 1 hour) after the basic dye.

Examples 4 and 5 Examples 1 and 2 are repeated using in place of the stated dyeing assistant the same quantity of a semi-synthetic retanning agent, consisting of a mixture of equal parts of chrome lignine sulphonate and proteins (degraded leather fibres). Penetration-dyed leathers of optimum fastnesses and brillancy are obtained.

Analogously as described in the examples 1 and 2 the following dyes may be employed: C.l.

Basic Brown 1, C.l. Basic Green 1, C.l. Basic Green 4, C.l. Basic Blue 9, C.l. Basic Blue 22, C.l.

Basic Blue 154, C.l. Basic Orange 21, C.l. Basic Orange 64, C.l. Basic Red 14, C.l. Basic Red 22, C.l. Basic Red 111, C.l. Basic Violet 16, C.l. Basic 27, C.l. Basic Yellow 2, C.l. Basic Yellow 11, C.l. Basic Yellow 13, C.l. Basic Yellow 60, C.l. Basic Yellow 94, and dyes of examples 128, 139, 141, 151, 154 and 157 of EP 41040 Al of the dye of example 35a of EP 92520 A2.

In place of the single dyes as in examples 1 and 2 there may also be employed mixtures of 2 or more dyes with similar dyeing properties.

Example 6 Chrome-tanned cow leather of 2mm thickness, the pH of which is adjusted to 4.5 is retanned in a fresh bath with 100% of water at 40"C, 2% mimosa extract, 2% of an aromatic syntane (condensation product of foramaldehyde and ss-naphthalene sulphonic acid) and 2% of a resin retanning agent on polyacrylate basis. After 45 minutes of drum-rotation the bath is drained off and 100% of water at 50"C and 5% polycondensate of formaldehyde and ss-naphthaline sulphonic acid are added; after 5 minutes of drum-rotation 0.7% of a dye mixture consisting of 0.4% C.l. Basic Yellow 82 0,1% C.l. Basic Red 59 0,2% C.l. Basic Blue 411 are added and dyeing is continued for 40 minutes.Then 5% of a fat-liquor (sulfinated fish oil-dry content 75%) are added and after further 45 minutes 2% formic acid (of 85% concentration) are added in 3 additions at intervals of 10 minutes from each other. 30 minutes after the last addition the pH of the bath is 3.3. To this are added 2% of the aqueous product of example 2 of DE-A 29 24 471 and the treatment is continued for 30 minutes, then the dyed leather is rinsed, drained, dried and cured as usual. The so-treated leather is dyed optimally and in a high-yield and the dyeing is of optimum fastnesses.

In analogous way as in example 6 other trichrornatic dyestuff combinations are employed, in which in place of each of the above mentioned yellow, red and blue components one or more of the following components are employed: C.l. Basic Orange 64, C.l. Basic Red 11 and C.l. Basic Blue 154 or also combinations of such elements.

Analogously as in the above Example 6 the other dyes mentioned in Examples 1 and 5 may be employed, e.g. as single dyes.

Example 7 Example 6 is repeated using N,N'-bis-(3-aminopropyl)-ethylenediamine in place of the product of example 2 of DE-A 29 24 471.

Example 8 (In this example the percentages refer to the dry weight of the substrate).

Suede sherling of chrome-tanned sheep skin (given dry into the drum) is drummed for 15 minutes with 2000% of water at 30"C containing the following additions: 1g/l of the condensation product of formaldehyde with ss-naphthaline sulphonic acid, 1g/l of the sodium salt of partially carboxymethlated lauryl alcohol decaethyleneglycolether, 1g/l of sulphated coconut oil and 1g/l of ammonia. Thereupon 5g/l of the polycondensate of formaldehyde of ss-naphthaline sulphonic acid are added followed after 2 minutes by 1.8gel of the basic dye according to example 141 of EP 41040 Al and dyeing is continued for 45 minutes. Then 2g/l of sulphited fish oil (dry content 75%) are added and after 20 minutes of drumming 2g/l of formic acid are added for acidification and treatment is continued for 30 minutes.Then the treated sheep skin is rinsed with water and cured as usual.

Example 9 Example 8 is repeated with the difference that 2g/l of the cationic dyeing assistant as described in example 6 is added after the acid addition and treatment is continued for 30 minutes after which the treated substrate is rinsed and cured as described.

According to a further variation of the dyeing process of examples 8 and 9 there is used in place of the undyed suede sherling a suede sherling in which the hair portion has been dyed with a wool-dye, with or without a reserving of the leather portion.

Very good dyeings are also obtained if in the above examples 8 and 9 the corresponding quantity of one of the following products is employed in place of the product of example 2 of DE-A 29 24471.

-N benzyl-N,N-dimethyl-taliow ammonium chloride -the condensation product according to example 1 of EP 151 370 A2 in the form of the sulphate -the condensation product of dimethylamine and epichlorohydrin (1/1) -trimethylolmelamine -the product according to example A of British Patent 1 238 091.

Example 10 Chrome-tanned cow leather of 2mm thickness is retanned as follows: the wet leather is drummed for 40 minutes in a fresh bath with 200% of water at 45"C, 1% dimethylolethyleneurea and 0.5% of a condensation product based on diphenylethersulphonic acid (sulphone). Then the bath is drained off. After drumming for 20 minutes with 100% of water at 35"C, 1% of ss- naphthalene sulphonic acid/formaldehyde polycondensate (sodium salt) and 1% of sodium formate; 1.2% of polyacrylate based retanning agent are added and treatment is continued for 20 minutes; thereupon there are added 3% of melamine formaldehyde resin and 3% of dimethylolu rea and, after drumming for further 60 minutes, the bath is drained off (pH of the bath=4.6).

The dyeing is now carried out as follows: 150% of water of 50"C, 3.6% fl-naphthaline sulphonic acid/formaldehyde polycondensate (sodium salt) and 0.5% of the brown dye C.l. Acid Brown 362 are added and after 2 minutes of rotation there are added 0.5% of the brown dye of example 157 of EP 41040 Al and 0.5% of the basic dye C.l. Basic Yellow 60 and dyeing is continued for 40 minutes. Then 7% of a 60% emulsion of a sulphited fish oil are added as the fat-liquoring agent. After 40 minutes of drum rotation 1% of formic acid (of 85% concentration) diluted 1:10 are added and after further 10 minutes of drum-rotation a further 1% of formic acid (85% concentration) diluted 1:10 are added and treatment is continued for 30 minutes. The pH is now 3.5.The treated leather is rinsed in running water, drained, dried and cured as usual.

Example 11 Example 10 is repeated using double the quantity of dye and adding 1% of the aqueous product of example 2 of DE-A 29 24 471 after the formic acid addition and before the rinsing.

The after-treatment with this product is continued for 30 minutes, whereupon the dyed leather is rinsed, drained, dried and cured as usual. The treated leather is optimally penetration-dyed in high yield and the dyeing displays optimum fastnesses.

Example 12 Example 10 resp. 11 is repeated with the difference that the anionic dye C.l. Acid Brown 362 is added 1 minute after the addition of the ssnapthalene sulphonic acid/formaldehyde polycondensate (sodium salt) the cationic dye mixture being added 2 minutes after the addition of the anionic dye.

Example 13 Example 10 resp. 11 is repeated with the difference that the ssnaphthalene sulphonic acid/formaldehyde polycondensate (sodium salt) is added to the liquor 1 minute after the addition of the anionic dye C.l. Acid Brown 262 and the cationic dye mixture is added 2 minutes after the addition of the polycondensate.

Example 14 Example 12 is repeated with the difference that the sequence of the dye additions is interchanged, i.e. the sequence of the additions is as follows: first the ss-naphthalene sulphonic acid/formaldehyde polycondensate (sodium salt); after 1 minute the cationic dye mixture; after 2 further minutes the anionic dye.

Example 15 Example 14 is repeated with the difference that the sequence of the additions of dyes and polycondensate is as follows: first the cationic dye mixture, after 1 minute the fi-naphthalene sulphonic acid/formaldehyde polycondensate (sodium salt); after 2 minutes the anionic dye.

Example 16-21 Examples 10-15 are repeated with the difference that in place of the dye C.l. Acid Brown 362 there is used a mixture of 1 part C.l. Acid Brown 127, 2 parts C.l. Direct Yellow 133 and 2 parts C.l. Mordant Brown 79.

Example 22 Chrome-tanned and neutralised sheep-leather of 0.8mm thickness is further neutralised by addition of 150% of water at 40"C, 1% sodium formate and after 10 minutes 1% sodium bicarbonate; after 30 minutes of drum-rotation there are added for retanning 1.6% of a retanning agent on polyacrylate basis and 3% dimethylolurea and after further 20 minutes of drum-rotation 3% of quebracho extract and 2% of ss-naphthalene sulphonic acid/formaldehyde polycondensate (sodium salt) and after 80 minutes of drum-rotation the bath is drained off (pH of the iiquor=4.5).

After washing with 300% water at 55"C for 10 minutes the bath is drained off and 150% of water at 55"C, 3,2% fi-naphthalene sulphonic acid/formaldehyde polycondensate (sodium salt) and 1% of the anionic dye C.l. Direct Black 155 are added and after 3 minutes of drum-rotation 1.8% of the cationic black dye according to example 35a of EP 92520 A2 are added and dyeing is continued for 40 minutes. Then fatting is carried out by addition of 8% of a 60% aqueous emulsion of a sulphited fish oil and 2.7% of the phosphoric acid partial ester of tetraoxyethylated tallow fatty alcohol (monoethanolamine salt) and continuation of the treatment for 60 minutes.Then there is added 1% formic acid and after 10 minutes there is added 1 further % of formic acid and the treatment is continued for 30 minutes upon which there is added 1% of the black cationic dye of example 35a of EP 92520 A2. After 30 minutes of drum-rotation 2% of formic acid are added and rotation is continued for further 30 minutes; then 1% of the product according to example 2 of DE-A 29 24 471 is added and the treatment is continued for 30 minutes. Then the so-treated substrate is rinsed with water, drained, dried and cured as usual. The resulting dyeing is level and fast and of outstanding penetration.

Very good dyeings are also obtained if in the above examples 11-22 in place of the product of example of DE-A 29 24 471 there is used the corresponding quantity of one of the following products: -N-benzyl-N,N-dimethyl-tallow ammonium chloride -the condensation product according to example 1 of EP 151 370 A2 in the form of the sulphate -the condensation product of dimethylamine and epichlorohydrine (1/1) -trimethylolmelamine -the product according to example A of British Patent 1 238 091.

Example 23 (paddle dyeing) (The percentages refer to the dry weight of the substrate).

A suede sherling of chome-tanned sheep skin (given dry into the paddle) is paddled 15 minutes with 2000% of water at 30"C that contains the following additions: lg/l of the polycondensate of formaldehyde and fi-naphthalene sulphonic acid (sodium salt), 1 gel of the sodium salt of partially carboxymethylated lauryl alcoholdecaethyleneglycolether, 1 gel of sulphated coconut-oil and 1g/l ammonia. Then 5g/l polycondensate of formaldehyde and ss-naphthalene sulphonic acid (sodium salt) are added together with 0.5g/l of the dye C.l. Acid Brown 362 and after 2 minutes there is added 1g/l of the basic dye of example 141 of EP 41040 Al and dyeing is continued for 45 minutes.After this time 2g/l of sulphited fish oil (dry content 75%) are added and the treatment is continued for 20 minutes, followed by acidification by addition of 2g/l of formic acid. Paddling is continued for further 30 minutes and then the treated skins are rinsed and cured as usual.

Analogously as described in the above examples 10-23 there are employed the following anionic dyes: C.i. Direct Black 19, 118, 155 or 163; Cl. Direct Blue 1, 15, 67, 77, 86, 106, 158, 159, 251, 262 or 267; C.l. Direct Green 26; C.l. Direct Yellow 6, 11, 28, 68, 93 or 132; C.l. Direct Orange 39 or 40; Cl. Direct Red 23, 24, 26, 63, 80, 83, 95, 111, 223 or 239; C.l. Direct Brown 169 or 170; C.l. Direct Violet 66; C.l. Direct Mordant Brown 79; C.l. Mordant Orange 6 or 10; C.l. Solubilized Sulphur Black 1; C.l. Solubilized Sulphur Blue 11; C.l. Solubilized Sulphur Red 6; C.l. Solubilized Sulphur Brown 10 or 14; C.l. Reactive Yellow 34; C.l. Reactive Orange 14, 26 or 33; C.l. Reactive Red 8; C.l. Reactive Brown 12; C.l. Reactive Blue 1 or 60; Cl. Acid Yellow 19, 65, 111, 112, 127, 204, 235 or 243; C.l.Acid Orange 3, 7, 67, 80, 82, 94, 95, 135, 168 or 170; C.l. Acid Green 9, 16, 20, 28, 60, 80, 106, 111 or 112; C.l. Acid Blue 25, 80, 83, 90, 113, 193, 227, 247, 250, 296, 312 or 334; Cl. Acid Black 1, 50, 58, 76, 115, 132, 170, 194, 209, 215 or 218; C.l. Acid Violet 48, 66, 90 or 128; Cl. Acid Red 4, 88, 97, 106, 114, 119, 215, 217, 261, 263, 362, 399 or 404; C.l. Acid Brown 28, 30, 53, 58, 75, 98, 126, 127, 188, 235, 237, 276, 289, 298, 303, 304, 311, 358, 359, 360, 362, 363, 396, 397, 402, 404, 409, 425, 426 or 432; or suitable mixtures of the mentioned dyes.

In place of the cationic dyes or dye mixtures mentioned in the examples 10-23 there may be used cationic dyes or dye mixtures selected from the following: C.l. Basic Brown 1, C.l. Basic Green 1, C.l. Basic Green 4, C.l. Basic Blue 9, C.l. Basic Blue 22, C.l. Basic Blue 154, Cl. Basic Orange 21, C.l. Basic Orange 64, C.l. Basic Red 14, Cl. Basic Red 22, C.l. Basic Red 111, Cl. Basic Violet 16, Cl. Basic Red 27, Cl. Basic Yellow 2, Cl.

Basic Yellow 11, C.l. Basic Yellow 13, C.l. Basic Yellow 60, C.l. Basic Yellow 94, the dyes of examples 128, 139, 141, 151, 154 and 157 of EP 41040 Al and the dye of example 35a of EP 92520 A2 as suitable together with the respective chosen anionic dyes.

Claims (19)

1. A process for the penetration-dyeing of tanned leather from an aqueous medium, wherein the leather is dyed with a basic dye (B) a retanning agent (H) being used as dyeing assistant.

2. A process according to claim 1 wherein also an anionic dye (A) is employed (A) and (B) being added in any desired sequence.

3. A process according to claim 2 wherein the one of the two dyes (A) and (B) is added when the other has not yet built up completely on the leather and the retanning agent (H) is added to the dye bath at any time before the addition of the first of the two dyes up to at latest contemporarily with the addition of the second of the two dyes.

4. A process according to claim 3 wherein dye (B) is added after the addition of (A) and/or (H).

5. A process according to claims 1-4 wherein (B) is added after (H) to the bath.

6. A process according to claims 1-4 wherein the dye (B) and retanning agent (H) are added contemporarily (B) and (H) being in the form of powder or granulate.

7. A process according to any of claims 2, 3 and 6 wherein the dyes (A) and (B) and the retanning agent (H) are added contemporarily and are in the form of powder or granulate.

8. A process according to any of claims 1-7 wherein the only or the second dye is added when the retanning agent (H) has not yet built up completely and irreversibly on the substrate.

9. A process according to any of claims 1-8 wherein the dyeing assistant (H) is an anionic sulpho-group-containing retanning agent.

10. A process according to any of claims 1-9 wherein the substrate is retanned before dyeing.

11. A process according to any of claims 1-10 wherein the substrate is fatted in the same bath.

12. A process according to claim 11 wherein the fatting is carried out after the dyeing.

13. A process according to claim 11 or 12 wherein fatting is carried out in the same bath before and after the dyeing.

14. A process according to any of claims 1-13 wherein fixation is carried out at pH 3-5.

15. A process according to claim 14 wherein after fixation an ulterior dyeing is carried out in the same bath by addition of dye (A) or (B) whereupon fixation is again carried out at pH 3-5 if required.

16. A process according to any of claims 1-15 wherein an after-treatment with a cationic dyeing assistant (K) is carried out in the same bath.

17. Leather whenever dyed by a process according to any of claims 1-16.

18. A process as claimed and as particularly described hereinbefore in any of examples 1-13.

19. Leather dyed by a process as claimed and as specifically described hereinbefore in any of examples 1-13.