EP0094329B1 - Tanning process for rendering leathers mycostatic, antimycosic and antifungicidal, and articles produced thereby - Google Patents

Description

The present invention relates to the tanning of leathers and it relates, more particularly, to the technical field of leathers intended to form all or part of clothing elements and, more especially, still leathers intended for the manufacture, at least in part, of shoes.

In the past, hides and skins were tanned with vegetable extracts, generally extracts of oak and chestnut which were used in large quantities. These vegetable tannins are known to have antiseptic properties.

The excess of such tannins incorporated into the leather had the effect of producing a salting out under the influence of perspiration. The antiseptic function of these products within the leather was thus transmitted indirectly to the skin and made it possible to combat any development of microbes or yeast.

Modern tanning methods have abandoned vegetable tannins to use mineral tannins to speed up the tanning process and therefore lower the cost of such a process and produce hides and skins of good general quality, flexibility , resistance and touch.

If such leathers are satisfactory on many levels, it seems, on the other hand, that it is now necessary to take responsibility for the development of mycoses or other skin diseases which are encountered more and more frequently.

In fact, there has been a considerable increase in yeast infections, especially in the foot, despite the many products sold to combat such conditions.

Studies on this subject have shown that a properly treated fungal infection of the feet recurs spontaneously as soon as the subject returns shoes that have already been the subject of a certain use. It was thus possible to determine that the fact of carrying over shoes which have already been used has the effect of bringing the skin into indirect contact with the leather by means of natural perspiration. The mycotic germs which are present on the surface of the leather of the shoe find, thus, a natural vehicle of development bringing them back in contact with the skin on which they can again develop and survive.

These findings prompted the search for a way to combat such transmission, in order to remove the obligation to destroy new or barely used shoes responsible for the effect of recontamination of a fungus, however treated and cured.

For this purpose, it has been proposed to impregnate the support with suitable agents having a bactericidal, fungicidal, etc. action. Such products are generally applied by any suitable means to the surface of the leathers to be placed in indirect contact with the skin. Besides that such products are generally responsible for odor emissions, more or less characterized and persistent, it has also been found that their antimycotic function degrades over time, since such products are not attached to leather. With use, such products were subject to a sort of salting out and disappeared from the surface of the leather on which they had been applied.

The expected effect quickly disappeared and the recontamination mycoses reappeared. Thus, French Patent No. 2,364,969 describes a process for protecting leathers against fungi consisting in tanning the hides in a tanning liquid containing usual tanning ingredients and the presence of 0.4 to 1.8 g of p -toluyl diiodomethylsulfone for 10 kg of skins. Among the usual ingredients are cited those containing chromium sulfate and sulfuric acid.

Another drawback of such products is that they are generally responsible for burns, dermatitis, allergies, which can be defined as iatrogenic diseases corresponding to accidents caused by the absorption of the skin by antimycotic and fungicidal products. Such iatrogenic diseases are known to produce various manifestations, ranging from mild burns to severe allergies and complex forms.

The object of the invention is to solve the above problems by proposing a new tanning process making it possible to make hides and skins mycostatic and antimycotic, in a durable way in time, without risk of allergic accident, even when the products made with such hides and skins are worn frequently and intensively.

Another object of the invention is to propose a new tanning process including, to achieve the object of the invention, a treatment phase which can be applied, without any loss of efficiency, at any stage of the tanning proper , that is to say from the confit to the last finishing operations.

An additional object of the invention is to propose a new tanning process which can be implemented for all types of hides and skins, without causing any modification of the essential qualities sought, that is to say fineness, flexibility, mechanical resistance, etc.

The method according to the invention gives leathers mycostatic properties by fixing a biocidal agent to the leather fiber by means of an insoluble metal complex and having basic functions giving it tanning properties.

The method according to the invention makes it possible to tan hides and skins from insoluble basic metal complexes formed in situ and on which it is possible to fix antiseptic, bactericidal, fungicidal, germicidal, antimycotic and more generally biocidal agents in order to their confer a mycostatic, bacteriostatic, fungistatic or more generally biostatic power.

These basic insoluble metal complexes having a tanning activity can be formed in situ on the fiber by the reaction of two water-soluble salts or by the fixing of a salt insoluble in water but soluble in an emulsifiable solvent and of course having the basic character already mentioned.

The same is true for the biocidal agent which can be used in a water-soluble form or used in a solvent. In both cases, it will react with the free basic functions of the insoluble and tanning metal complex to fix it in an insoluble form.

This process can be used alone or in combination with other conventional tanning agents such as metal salts of chromium, iron, aluminum, silica, zirconium, etc. with tanning properties, or even proven vegetable or synthetic tannins. It can be used for pretanning, tanning or retanning.

• - on fait agir un sel d'un métal ayant tout à la fois des propriétés antimycosiques et bactéricides et un certain pouvoir tannant, comme le zinc, le cuivre, l'argent, etc. tout en évitant ceux dont la toxicité est trop notoire comme le mercure, le plomb... ou encore, ceux présentant certains caractères radioactifs.
• - la plupart de ces métaux présentent l'inconvénient de ne former des complexes stables avec le collagène du cuir qu'à des pH alcalins. Aussi, pour conférer à ce tannage une irréversibilité à tous les pH habituels dans l'industrie du cuir, on les transforme en complexes insolubles basiques présentant cependant une affinité importante pour le collagène, grâce à des anions spécifiques pour chacun d'eux.

The manufacturing principle is as follows:

• - a salt of a metal is made to act, having both antimycotic and bactericidal properties and a certain tanning power, such as zinc, copper, silver, etc. while avoiding those whose toxicity is too notorious such as mercury, lead ... or even those with certain radioactive characteristics.
• - most of these metals have the drawback of forming stable complexes with leather collagen only at alkaline pHs. Also, to give this tanning an irreversibility at all the usual pH in the leather industry, they are transformed into basic insoluble complexes, however, having a significant affinity for collagen, thanks to specific anions for each of them.

In the text, the set of anions may be replaced by (A) or by (A-) and an anion not specified by (a) or (a-) or in a more general and precise manner (a ^n- ) .

Likewise for the cations the set will be (C) and an unspecified cation (c) or according to the protocol adopted for the anions (cm +).

Basicity will be indicated in a global formula by a basic (OH) group capable of forming by dissociation of the product an ionic or ionized particle (OH) -.

(M) will represent all of the antibacterial or bactericidal, antifungal or fungicidal or even antiseptic antimycotic agents and, more generally, biocides. A biocide from this list and not specified will be indicated by (m) in a general or global application.

The list of anions (A), cations (C) and biocides (M) concerned by this process will be given below.

• Dérivés du soufre : sulfate, thiosulfate, sulfites, hydrosulfites, sulfures,
• Dérivés du sélénium : des séléniates aux séléniures,
• Dérivés du tellure : des tellurates aux tellurures,
• Dérivés du phosphore : phosphates, phosphites, phosphures,
• Dérivés du silicium : principalement silicates, fluorosilicates et dérivés,
• Dérivés de l'étain : principalement les stannates et dérivés des stannates,
• Dérivés du bismuth : bismuthate et dérivés,
• Cités pour mémoire parce que trop toxiques : arséniates, antimoniates et les dérivés des cyanures.

List of Anions (A) giving interesting compounds in the tanning of biostatic leathers:

• Sulfur derivatives: sulfate, thiosulfate, sulfites, hydrosulfites, sulfides,
• Selenium derivatives: from seleniates to selenides,
• Tellurium derivatives: from tellurates to tellurides,
• Phosphorus derivatives: phosphates, phosphites, phosphides,
• Silicon derivatives: mainly silicates, fluorosilicates and derivatives,
• Tin derivatives: mainly stannates and stannate derivatives,
• Bismuth derivatives: bismuthate and derivatives,
• Cited for memory because too toxic: arsenates, antimoniates and derivatives of cyanides.

Monovalent acids derived from fluorine, chlorine, iodine and bromine are not to be considered interesting except with tri or tetravalent metals. The same is true for nitrogen anions which are monovalent with the same reservations.

• Seuls ne conviennent pas à ce procédé le lithium, le sodium, le potassium, le rubidium, et le caesium qui sont monovalents et qui de ce fait ne peuvent pas donner de sels basiques. Le radon a été éliminé parce qu'il est non ou zérovalent donc non réactif et incapable de donner des sels.

List of Cations (C) giving interesting compounds for the tanning of biostatic leathers:

• The only lithium, sodium, potassium, rubidium and caesium which are monovalent and which therefore cannot give basic salts are not suitable for this process. Radon has been eliminated because it is non or zerovalent therefore non reactive and unable to give salts.

• - les métaux radioactifs suivants : technétium, prometium, francium, radium, actinium, thorium, protactinium, uranium, polonium et astatine et
• - les métaux lourds toxiques suivants à cause de leur toxicité : mercure, cadmium et plomb.

Are not recommended even if they can give complexes meeting the criteria of the process:

• - the following radioactive metals: technetium, prometium, francium, radium, actinium, thorium, protactinium, uranium, polonium and astatin and
• - the following toxic heavy metals because of their toxicity: mercury, cadmium and lead.

Are set apart because of their too high price although they may be suitable: scandium, germanium, gallium, niobium, yttrium, ruthenium, rhodium, palladium, terbium, praeseodyme, neodymium, holmium, erbium, samarium, thulium, europium, ytterbium, gadolinium, lutetium, hafnium, tantalum, rhenium, osmium, gold, iridium and platinum.

Are specially selected: titanium, vanadium, manganese, cobalt, nickel, molybdenum, tungsten, thallium, bismuth, indium, tin, beryllium, magnesium, calcium, strontium , and barium.

Are retained and usable according to the invention (although their tanning properties in the form of hydroxide are known and used): chromium, iron, zirconium and aluminum used in the form of basic insoluble complexes.

Finally, will be preferred to other cations used alone or in admixture with others: copper, zinc and silver because of their antiseptic properties.

List of biocides (M) used in the processes for obtaining biostatic leathers by tanning with insoluble metal complexes.

Due to the proliferation of antiseptics on the market, all antiseptics capable of binding to insoluble and basic metal complexes can be added to the list below for the benefit of control.

Naphthenic acid and its salts, dimethylthiocarbamic acid and its salts, 2 mercaptobenzothiozol and its salts, diethyldithiocarbamic and its salts, dimethyldithiocarbamates, ethylene dithiocarbamate, ethylxanthate, isopropylxanthate and phenylacetate undethenylacetate, and ethylphenylacetate nitrophenoxyacetatic acid and nitrophenoxyacetates, cresylic acid (cresol) and cresylates, bensuldazic acid and bensuldazates, 2 phenylphenol and salts, pentachlorophenol and salts, tetrachlorophenol, triphenylantimoine, triphenylboluth, parphenol, parethylphenol, parphenophenol, parethylphenol, parethylphenol, parphenophthalophenol, parethylphenol, parphenophenol mercurobutol) and chloromercuriphenates, salicyanilide, griseofulvin, amphotericin, nystatin (mycostatin), flucytosine, siccamine, bacitracin, capilin O. chloro-a-diphenylbenzylimidazole, miconazole (daktarin), econazole) chloro 4 nitrophenol, 1,2 bis (ethoxycarbonylthiouréido) benzene (thiophanase), 6. chloro, 1-2 benzoisothiazoline 3 one (ticlatone) fungeryl, gentian violet, eosin and eosinates, etc ...

The number and the substances are not limited. All that matters is the mode of binding of the biocide to the leather fiber by means of a basic insoluble and tanning complex.

From these conventions and by adopting the language of modern mathematics applied to chemistry, it is possible to write the formula of an insoluble basic metal complex (c, a, OH), its tanning action (collagen or leather) U (c, a, OH) and the final complex giving a biostatic leather in the form (leather) U (c, am), "U being the mathematical symbol of the union.

This way of writing makes it possible to highlight the tanning mode of action of the insoluble metal complex and its biocidal function.

• Le principe de la fabrication in situ de complexes métalliques insolubles basiques (c, a, OH) procède d'une loi de la chimie :
  
  toutes les fois où un des sels formés dans le second membre peut s'éliminer de la solution par précipitation ou par évaporation. On peut donc écrire :
  
  toutes les fois où a^IC² ou a²c¹ s'évapore ou précipite. Dans le cas présent, l'action intéressante est la précipitation. Dans certains cas il est possible de produire la précipitation conjointe des deux composés formés. Comme exemple, on peut citer :
  
  réaction dans laquelle le sulfate de baryum et le sulfure de zinc, formés à partir du sulfate de zinc et du sulfure de baryum, précipitent en même temps.

Method of obtaining insoluble and basic metal complexes:

• The principle of in situ manufacturing of basic insoluble metal complexes (c, a, OH) comes from a law of chemistry:
  
  whenever one of the salts formed in the second member can be eliminated from the solution by precipitation or by evaporation. We can therefore write:
  
  whenever a ^I C ² or a ² c ¹ evaporates or precipitates. In this case, the interesting action is precipitation. In some cases it is possible to produce the joint precipitation of the two compounds formed. As an example, we can cite:
  
  reaction in which barium sulfate and zinc sulfide, formed from zinc sulfate and barium sulfide, precipitate at the same time.

In this text, precipitated complexes have been defined as basic. This character is very useful in tanning to allow efficient tanning. It is this basicity which gives such character to cations such as chromium, iron, alumina, zirconium and silicon, etc. In the mineral tanning processes which use metals, the tanning is obtained by metal hydroxides. Trivalent and sometimes tetravalent cations are used to the exclusion of all others. Unlike the process according to the invention, so-called “masking agents” are used which do not insolubilize the basic forms but on the contrary dissolve them. However, the tanning factor remains the basicity and the versatility equal to or greater than 3 which makes it possible to crosslink or three-dimensional the bonds between the collagen fibers by cationic bridges and this in a statistical manner.

Tanning with cationic hydroxides can be expressed with the conventions adopted (c, OH) and by tanning becomes (leather) U (c) and (c) is tri or tetravalent.

• Un anion peut se définir qualitativement par le nombre de charges électronégatives par molécule. Par exemple :
  • (a-) anion monovalent ou monoacide,
  • (a--) anion bivalent ou biacide et par extension,
  • (a^m-) anion polyvalent ou polyacide.
  • Il en est de même pour les cations (c),
  • (c⁺) cation monovalent ou monobasique,
  • (c⁺⁺) cation bivalent ou bibasique,
  • (cⁿ⁺) cation ou ion métallique polyvalent ou polybasique.

Study of the various salts formed between an anion and a cation:

• An anion can be defined qualitatively by the number of electronegative charges per molecule. For example :
  • (a-) monovalent or monoacid anion,
  • (a--) bivalent or biacid anion and by extension,
  • (a ^m- ) polyvalent or polyacid anion.
  • The same is true for cations (c),
  • (c ⁺ ) monovalent or monobasic cation,
  • (c ⁺⁺ ) bivalent or bibasic cation,
  • (c ^{n +} ) polyvalent or polybasic metal cation or ion.

To bring up the notion of basicity, it is necessary to extract (OH-) from the set of anions (A) and even from the subset (A-). From there, there is a rule: the number of salts that it is possible to make between an anion and a cation is equal to the sum of the acidities (number of valences) and the sum of the basicities (valences) minus one. For example with (a ^m- ) and (c ^{n +} ), the number of salts = m + n - 1.

For example, between phosphoric acid, triacid and tribasic chromium, 5 salts can be formed: 2 acids, a neutral and 2 basic. It appears that the number of basic salts is always equal to n - 1 and that of the acid salts to m - 1.

In the case of the invention, the formation of basic salts in the insoluble complexes requires not taking cations where n = 1 or n - 1 = 0. All the metals of the alkaline group, ie lithium, are therefore to be eliminated from the process. sodium, potassium, rubidium and cesium.

Likewise, monovalent or monoacid anions such as fluorides, chlorides, bromides and iodides will be excluded (see lists above).

The anions can be introduced into the final composition either in the form of soluble salts directly giving an insoluble basic complex, or be obtained by reaction of certain compounds to obtain the one that is sought, or still go through the stage of a third solvent which will be reacted in solution or in emulsion.

ou

Il est possible d'obtenir un résultat analogue avec de l'hyposulfite

On peut aussi réaliser le même objectif par l'adjonction d'acide oxalique

For example, from the sulfide anion (S--), we can obtain:

or

It is possible to obtain a similar result with hyposulfite

We can also achieve the same objective by adding oxalic acid

To obtain more weight, it is possible to introduce into these last two reactions barium salts (Ba) to transform Na ₂ SO ₄ into BaS0 ₄ which is insoluble.

• La fixation du complexe basique peut s'écrire des deux manières, soit sous forme d'une équation chimique :
  

Attaching the complex to the leather:

• The fixation of the basic complex can be written in two ways, either in the form of a chemical equation:
  

The larger 1, the greater the tanning effect. There is a real crosslinking and even in some cases a crosslinking of the collagen by transforming it into leather.

• On peut exprimer l'effet tannant du complexe minéral basique insoluble dans le langage des mathématiques modernes soit collagène U C_xA_y(OH)_z- H₂O x 1.

Fixation of the biocide (m) on the complex after its fixation on the collagen:

• We can express the tanning effect of the basic mineral complex insoluble in the language of modern mathematics, namely collagen UC _x A _y (OH) _z - H ₂ O x 1.

For the fixation of (m) to be real, z - 1 must not be 0 or z - 1 = 1.

The process leads to a mycostatic action. It is therefore necessary that the or the antiseptic product belonging to (M) is (are) fixed (s) on the collagen therefore on the leather fibers via the insoluble basic metal complex. This bond must be really chemical. It must be done thanks to free basic (OH) groups. This therefore implies the obligation to have z - 1 = ₁ .

The list of antiseptics (M) suitable for this use has been given above.

• collagénate de (C_xA_yM_(z-1))

The final formula of the mycostatic leather obtained by the process according to the invention can be summarized in the following formula:

• (C _x A _y M _(z-1) ) collagenate

If in the writing of this formula the cations were written C and not c, it is possible to use several of them together. It is the same for the anions written A and not a as well as for the antiseptics of the set defined by (M). The fact of using various cations, anions and antiseptics does not in any way modify the characteristics of the present process. The number of each is not limitative.

In this set the complex (c, m) gives all the desired reactivity to the antiseptic (m) to impart mycostaticity to the leather fibers tanned by the pair (c, a).

• On appelle biostaticité d'un support, en l'occurrence les fibres du cuir provenant du collagène convenablement tanné, la propriété par laquelle des microbes, bactéries, levures ou champignons ne peuvent ni se développer ni survivre à son contact. De plus la biostaticité implique qu'il n'y ait ni relarguage ni diffusion des agents (m) antiseptiques, bactéricides, fongicides et autres biocides autour du support. Cette précaution est nécessaire pour éviter que le corps humain en contact avec ce support ne risque de subir des brûlures, des dermites ou des allergies même légères, même si ce contact est indirect, par exemple au travers d'une chaussette ou d'un bas. A partir du moment où il y a relarguage, voire même simple diffusion, même très légère, cela signifie qu'il y a migration suffisante pour provoquer une action antibactérienne et antimycosique pouvant atteindre le corps humain et y provoquer des brûlures, des dermites, des allergies et autres maladies iatrogènes. Ces désagréments ont été constatés par divers organismes techniques professionnels.

Definition of biostaticity:

• The biostaticity of a support, in this case the fibers of the leather originating from suitably tanned collagen, is called the property by which microbes, bacteria, yeasts or fungi can neither develop nor survive on contact. In addition, biostaticity implies that there is neither release nor diffusion of the agents (m) antiseptics, bactericides, fungicides and other biocides around the support. This precaution is necessary to prevent the human body in contact with this support from risking burns, dermatitis or even mild allergies, even if this contact is indirect, for example through a sock or stocking . From the moment there is release, or even simple diffusion, even very slight, this means that there is sufficient migration to cause an antibacterial and antimycotic action which can reach the human body and cause burns, dermatitis, allergies and other iatrogenic diseases. These inconveniences have been noted by various professional technical bodies.

• De cette définition, il résulte deux types d'essais propres à démontrer que les microbes, bactéries, levures et champignons ne peuvent se reproduire ni survivre au contact de ces cuirs et autres supports contenant des fibres de cuir ainsi traitées. D'autre part, il faudra contrôler que l'antiseptique (m) utilisé ne relargue pas ni ne migre, ni ne diffuse.

Biostaticity control:

• From this definition, two types of tests result which demonstrate that microbes, bacteria, yeasts and fungi cannot reproduce or survive on contact with these leathers and other supports containing leather fibers thus treated. On the other hand, it should be checked that the antiseptic (m) used does not release, migrate or diffuse.

• 1. Mettre sur l'échantillon de cuir à examiner, un morceau de jersey imprégné d'une culture des microbes, bactéries, levures ou champignons les plus fréquents dans les mycoses humaines. A titre d'exemples, on peut citer parmi les bactéries, les pseudomonas (P. aeruginosa), les staphylocoques (S. aureus - S. epidermidis), pour les levures, les candida (candida albicans et autres) et pour les champignons les tricophytons (T. mentagrophytes, T. rubrum, T. pedis) et les epidermophytons (E. floccosum, E. scopulariopsis brevicaulis, etc...).

These tests can be summarized as follows:

• 1. Put on the leather sample to be examined, a piece of jersey impregnated with a culture of microbes, bacteria, yeasts or fungi most frequent in human yeast infections. By way of examples, mention may be made, among bacteria, of pseudomonas (P. aeruginosa), staphylococci (S. aureus - S. epidermidis), for yeasts, candida (candida albicans and others) and for fungi. tricophytons (T. mentagrophytes, T. rubrum, T. pedis) and epidermophytons (E. floccosum, E. scopulariopsis brevicaulis, etc ...).

The jersey is kept in contact with the leather for 12 hours in an atmosphere of 100% humidity and at a temperature of 37 ° C. The jersey is then separated from the leather and left for 12 hours at 20 ° C and a humidity of 60%.

After microbial impregnation and drying, the leather pieces will be placed in a culture broth most favorable to the strain tested, at the pH and temperature most favorable for the development of each species. With a really mycostatic leather, there must be no bacterial development (negative test).

To know the product's efficiency over time, several impregnation / drying cycles will be carried out.

2. As the tests of 1 can be negative with free antibacterial, antimycotic or antifungal antiseptics, it is necessary to check if the material is really mycostatic and not only antiseptic by a simple spraying or impregnation of a bactericidal or fungicidal product.

A leather sample is then placed in a PETRI box with the most suitable culture broth for the strain studied and seeded with the bacteria, yeasts and fungi chosen, even on the leather sample. The cultures must develop on all the surface of the box except in contact with the leather above and below.

If by chance there was a halo of non-proliferation of the culture around the leather sample, this would mean that there is a migration of the active product. We can call this migration diffusion or salting out, this results in a departure of the active product, often active at low concentration. The observation of the conservation of the biocidal activity of the product is not proof of non-migration.

To then check the merits of a mycostatic quality, it is necessary to carry out an even more severe check. A sample of finely ground leather is placed in a cartridge of SOXHLET. We then do 50, 100 or more, filling / emptying cycles with water.

After this series of leaching, the extract thus obtained is studied with very sensitive detection methods (infrared spectrophotometer for example). One can also make tests on carefully selected culture broths. With truly mycostatic leathers, the results must be negative in either case. The advantage of infrared spectrophotometry is to be able check whether the biocidal compound has migrated. On the other hand, it is possible to control the quality of the fraction of the tanning by the mineral complex, or even the fixing of other products used in the tanning.

The laboratory tests were carried out with the various cations of the set (C) in association with the anions of the list (A) and the various antiseptics of the list (M).

The various tests have been successful. However, for reasons of convenience of supply, but also because they presented biocidal qualities by themselves, the following cations were retained in the tests: zinc, copper and silver. Lead, mercury and cadmium were released despite their results due to their toxicity, as were radioactive metals.

As regards the anions, it is preferable to choose, from list (A), direct and indirect sulfides, phosphates and borates, as well as silicates.

Among the antiseptics from the list (M), dimethylthiocarbamate, undecylenic acid and phenylphenol 2 will preferably be chosen. The results at minimum doses give excellent results.

The tanning process can be applied once or several times at the various stages of manufacturing: pre-tanning,

in tanning proper,

in retanning,
whether with mineral tannins (chromium, aluminum, iron), with synthetic or vegetable tannins, including those having undergone the most diverse or associated pretanning.

The following examples illustrate the invention without, however, limiting its scope.

Example 1 - Pre-tanning:

• - weigh the skins,
• - introduce into the fuller:

• water 80%
• zinc sulfate 4%
• copper sulphate 5%

• - rotate the fuller until the salts are dissolved and introduce the skins,
• - rotate the fuller for one hour,
• - check penetration by cutting the skin,
  For pickled skins, additionally add 6 or 8% salt (sodium chloride ₌ NaCl) to the initial solution and dissolve it well before introducing the skins.
• - then add:

• sodium sulfhydrate 4%

• - turn to obtain a homogeneous pH of 7.0 in the bath and the skin.

For pickled skins, this pH will be obtained by adding baking soda dissolved in hot water (60 ° C). The amount of bicarbonate depends on the composition of the initial pickle.

It is possible to substitute for the sulphhydrate a phosphate, a polyphosphate, or even a silicate. It is retanned with chromium, vegetable tannin or synthetic.

The fungicide agent chosen from the list above can be added, after neutralization at pH = 7.0 or after retanning, generally in the form of sodium hydroxide salt. It can also be mixed with food before or after retanning.

Example 2 - Fuller's mineral tanning:

• Raw material: pickled skins.

• - weigh the skins,
• - introduce into the fuller:

• water 80%
• salt (NaCI) 6%

• - rotate the fuller to dissolve the salt,
• - introduce the skins and add:

• chromium sulfate at 32 ° Sch 10%
• zinc oxide 3%

• - rotate the fuller until the zinc oxide dissolves and a homogeneous pH of 3.5,
• - add :

• sodium hyposulfite 3%

• - run 30 minutes,
• - add :

• barium chloride 6%

• - run 30 minutes,
• - add :

• 3% baking soda

• - run for 30 minutes at pH 7.0.

It should be noted that the Schrolemmer 32 ° chromium sulfate corresponds to the formula Cr (SO ₄ ) OHCr ₂ (SO ₄ ) ₃ = 0 ° and Cr (OH) ₃ = 100 ⁰ Sch. and Cr ₂ (SO ₄ ) (OH) ₄ = 66 ° Sch. This scale is adopted internationally.

During tanning, chromium oxide binds to the leather fiber and releases sulfuric acid which dissolves the zinc oxide to form zinc sulfate. This is induced in the notion of tanning.

Example 3: Retanning Extra White Leather Fuller:

• - peser les peaux, les mettre dans le foulon et ajouter :

• eau 250 %
• sel (NaCI) 18%

• - faire tourner jusqu'à dissolution du sel,
• - ajouter :

• acide oxalique 4 à 5 %
• selon effet désiré

• - faire tourner pendant 10 minutes, laisser en contact 40 minutes et tourner 10 minutes, soit une durée de 60 minutes,
• - vider le bain,
• - rincer 10 minutes à l'eau froide courante,
• - égoutter 10 minutes et refaire un nouveau bain :

• eau 80 %
• oxyde de zinc 2,6 %
• sulfate de zinc 5,75 %

• - durée 60 minutes (vérifier la dissolution de l'oxyde de zinc) et ajouter :

• sulfhydrate de sodium 1,76%

• - faire tourner le foulon 15 minutes et ajouter :

• chlorure de baryum 6,0 %

• - faire tourner 15 minutes et ajouter :

• tannin synthétique type SYNEKTAN PM (marque déposée) 2 %

• - faire tourner 30 minutes, laisser passer la nuit dans le foulon au repos, puis faire tourner 15 minutes,
• - vider le bain,
• - rincer 10 minutes à l'eau (60 °C) et faire un bain neuf :

• eau 65 °C 80 %
• huile de pied de boeuf 1,6%
• acide undécylénique 0,5%
• 2 phényl phénol 0,2 %
• émulsifiant type SANDOLIX WWL (marque déposée) 4,9 %
• lithopone alcalin 6,0 %

• - faire tourner 60 minutes et ajouter tannin synthétique type :

• SYNEKTAN PM (marque déposée) 8,0 %

• - rotation discontinue 90 minutes,
• - vider le bain et éventuellement sortir les peaux après rinçage eau froide, établir et sécher.

Raw material: derailed Wet Blue skins.

• - weigh the skins, put them in the fuller and add:

• water 250%
• salt (NaCI) 18%

• - rotate until the salt is dissolved,
• - add :

• oxalic acid 4 to 5%
• according to desired effect

• - rotate for 10 minutes, leave in contact 40 minutes and rotate 10 minutes, a duration of 60 minutes,
• - empty the bath,
• - rinse for 10 minutes under running cold water,
• - drain for 10 minutes and redo a new bath:

• water 80%
• zinc oxide 2.6%
• zinc sulfate 5.75%

• - duration 60 minutes (check the dissolution of the zinc oxide) and add:

• sodium sulfhydrate 1.76%

• - rotate the fuller for 15 minutes and add:

• barium chloride 6.0%

• - rotate for 15 minutes and add:

• synthetic tannin type SYNEKTAN PM (registered trademark) 2%

• - rotate for 30 minutes, let the night pass in the fuller at rest, then rotate for 15 minutes,
• - empty the bath,
• - rinse for 10 minutes with water (60 ° C) and make a new bath:

• water 65 ° C 80%
• beef foot oil 1.6%
• 0.5% undecylenic acid
• 2 phenyl phenol 0.2%
• emulsifier type SANDOLIX WWL (registered trademark) 4.9%
• 6.0% alkaline lithopone

• - rotate 60 minutes and add synthetic tannin type:

• SYNEKTAN PM (registered trademark) 8.0%

• - discontinuous rotation 90 minutes,
• - empty the bath and possibly remove the skins after rinsing with cold water, establish and dry.

If the leather is intended to make dark colors, it is advisable to replace all or part of the zinc sulphate with copper sulphate. The dyeing and feeding operations can be done without intermediate drying.

Example 4: Retanning of full-grain leathers:

• - weigh the moistened skins,
• - put them in the drum with:

• water 80%
• oxalic acid 4%

• - discontinuous rotation 60 minutes,
• - empty the bath,
• - drain for 5 minutes and redo the new bath:

• water 80%
• zinc sulfate 6%

• - run 60 minutes and add:

• sodium hyposulfite 3%

• - rotate the fuller for 60 minutes,
• - empty the bath,
• - rinse for 10 minutes, water at 65 ° C,
• - drain 5 minutes and make a new bath:

• water 65 ° C 80%
• emulsifier type SANDOLIX WWL (registered trademark) _3%
• 2 phenyl phenol sodium hydroxide 0.3%

• - shoot 20 minutes,
• - add :

• formic acid 0.5%

• - rotate the fuller for 20 minutes,
• - empty the bath,
• - take out the skins and establish them.

If the leathers are intended for dark shades, part of the zinc sulphate can be added or replaced by copper sulphate. To give weight and a little firmness, you can also add 7 to 14% of barium chloride.

The SANDOLIX WWL can be replaced by any emulsifier containing a percentage of sulfated or sulfonated oil, or even sulfited.

In the case of sheepskins for linings (sheepskin), it is unnecessary to add food, but it is desirable to add 0.6% of undecylenate of soda at the same time as 2-phenylphenol. This operation is done hot but can be done cold without bath.

Example 5: Special method for leather with soles:

• - peser les cuirs humidifiés et les mettre dans le foulon avec :

• eau 80 %
• sulfate de zinc 6 %

• - faire tourner 60 minutes et ajouter :

• sulfure de baryum 5,80%

• - tourner 60 minutes et ajouter :

• diéthyldithiocarbamate de soude 0,2 %

• - faire tourner le foulon 30 minutes,
• - vider le bain,
• - rincer 10 minutes à l'eau froide,
• - égoutter et sortir les peaux.

The raw material can also be assembly raw materials, welts or synderms.

• - weigh the moistened leathers and put them in the drum with:

• water 80%
• zinc sulfate 6%

• - run 60 minutes and add:

• barium sulfide 5.80%

• - turn 60 minutes and add:

• 0.2% sodium diethyldithiocarbamate

• - rotate the fuller for 30 minutes,
• - empty the bath,
• - rinse for 10 minutes with cold water,
• - drain and remove the skins.

For skins that are a little dark or that must be finished in dark color, all or part of the zinc sulphate can be replaced by copper sulphate. This method has the advantage of not forming hygroscopic salts in the leather or at least minute quantities.

Sodium diethyldithiocarbamate can be replaced with sodium bensuldazate.

The invention is not limited to the examples described and shown, since various modifications can be made thereto without departing from its scope.

Claims (10)

1. Tanning process giving to leathers and hides biostatic properties with no migration of the active agent, characterized in that :

a) the leathers and hides are tanned by forming in situ, a non-soluble metallic complex comprising one or several OH groups, and fixing said complex on the collagen ;

b) the biocidal agent is fixed on said complex.

2. Tanning process acoording to claim 1, characterized in that the non-soluble basic metallic complexes, with a tanning activity, are formed in situ on the fiber by reacting two water-soluble salts.

3. Process according to claim 1, characterized in that the said non-soluble basic metallic complexes, with a tanning activity, are formed in situ on the fiber by fixing a salt insoluble in water but soluble in an emulsionable solvent of a basic nature.

4. Process according to any one of claims 1 to 3, characterized in that the biocidal agent is used in water-soluble form or in solution in a solvent.

5. Process according to any one of claims 1 to 4, characterized in that conventional tanning agents are also used such as the metal salts of chromium, iron, aluminium, silica, zirconium or vegetable or synthetic tanning agents.

6. Process according to any one of claims 1 to 5, characterized in that the anions (A) are selected from the following :

Sulphur derivatives : sulphate, thiosulphate, sulphites, hydrosulphites, sulfides,

Selenium derivatives : from selenates to selenides,

Tellurium derivatives : from tellurates to tellurides,

Phosphorous derivatives : phosphates, phosphites, phosphides,

Silicium derivatives : mainly silicates, fluosilicates and derivatives,

Tin derivatives : mainly stannates and derivatives thereof,

Bismuth derivatives : bismuthate and derivatives.

7. Process according to claims 1 to 5, characterized in that the cations are selected from the following :

titanium, vanadium, manganese, cobalt, nickel, molybdenum, tungsten, thallium, bismuth, indium, tin, beryllium, magnesium, calcium, strontium and baryum cations,

chromium, iron, zirconium and aluminium cations used in non-soluble basic complex form.

8. Process according to any one of claims 1 to 5, characterized in that the cations (C) used are selected from copper, zinc or silver cations.

9. Process according to any one of claims 1 to 8, characterized in that the biocidal agent is selected from the following : naphtenic acid and its salts, dimethylthiocarbamic acid and its salts, 2 mercaptobenzothiazol and its salts, diethyldithiocarbamic and its salts, dimethyldithiocarbamates, ethylene, dithiocarbamate, ethylxanthate, isopropylxanthate, ethylphenyldithiocarbamate, undecylenic acid and unde- cylenates, hydroacetic acid and dehydroacetates, phenoxyacetic acid and phenoxyacetates, nitrophenox- yacetatic acid and nitrophenoxyacetates, cresylic acid (cresol) and cresylates, bensuldazic acid and bensuldazates, 2-phenylphenol and its salts, pentachlorophenol, and its salts, tetrachlorophenol, triphenylantimony, triphenylbismuth, trimethyl-tin, paranitrophenols, and paranitrophenates, 3-methyl- chlorophenol (p. chlorometaxylenol), chloromercuriphenol (mercurobutol) and chloromercuriphenates, silicyanilide Griseofulvin, Amphotericin, Mystatin (Mycostatin), Flucytosin, Siccamin, Bacitracin, Capilin, 0-chloro-a a-diphenylbenzylimidazole, miconazole (Daktarin), econazole (pevaryl), haloprogine, 2-chloro-4-nitrophenol, 1,2 bis-(ethoxycarbonylthioureido) = benzene (thiophanase), 6-chloro 1,2-ben- zoiisothiazoline-3-one (ticlatone) fongeryl, gentian violet, Eosin and eosinates.

10. Leathers and hides, characterized in that they have been tanned by a process according to any one of claims 1 to 9.