(19)
(11)EP 4 022 099 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
14.09.2022 Bulletin 2022/37

(21)Application number: 21754838.7

(22)Date of filing:  20.07.2021
(51)International Patent Classification (IPC): 
C14C 1/08(2006.01)
C14C 3/10(2006.01)
C14C 3/06(2006.01)
C14C 3/28(2006.01)
(52)Cooperative Patent Classification (CPC):
C14C 1/08; C14C 3/06; C14C 3/10; C14C 3/28
(86)International application number:
PCT/IB2021/056546
(87)International publication number:
WO 2022/018632 (27.01.2022 Gazette  2022/04)

(54)

ENVIRONMENTALLY FRIENDLY PROCESS FOR TANNING HIDES

UMWELTFREUNDLICHES GERBVERFAHREN

PROCÉDÉ DE TANNAGE ÉCOLOGIQUE


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 22.07.2020 IT 202000017719

(43)Date of publication of application:
06.07.2022 Bulletin 2022/27

(73)Proprietor: Beken Italia S.r.l.
36071 Arzignano (IT)

(72)Inventor:
  • NEGRETTO, Mirko
    36071 Arzignano (IT)

(74)Representative: Palladino, Saverio Massimo et al
Notarbartolo & Gervasi S.p.A. Viale Achille Papa, 30
20149 Milano
20149 Milano (IT)


(56)References cited: : 
US-A- 4 126 413
US-A1- 2015 376 726
US-A1- 2005 268 671
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    FIELD OF THE INVENTION



    [0001] The present invention refers to an innovative process for the tanning of animal hides characterised, compared to currently adopted processes, by the non-adoption of the step known in the industry as "pickling", which is one of the main sources of pollution caused by the tanning industry. The invention also concerns hides tanned by the new process.

    STATE OF THE ART



    [0002] Tanning is the treatment to which the hides are subjected in order to transform them into leather, thus allowing their preservation indefinitely and the processing to make them suitable for use in various industrial sectors, including furniture and clothing, leather goods industry (bags, shoes and leather accessories) and in the automotive sector.

    [0003] Hide preservation treatments, from the slaughter of the animals to tanning (and possible further subsequent treatments), have been known for centuries and have many variations; it is not possible to give an exhaustive description of these treatments here, for which reference should be made to specialised manuals, such as the book Tanning Chemistry: The Science of Leather, Anthony D. Covington and William R. Wise, Royal Society of Chemistry, 2nd Edition, 2019.

    [0004] In short, all hide treatment processes essentially comprise the following steps:
    • Preservation: this operation must be carried out as quickly as possible after killing the animal, and consists in creating conditions inside the hide that prevent the development of microorganisms that would cause the putrefaction thereof. The most widely used methods for this purpose are salting and drying;
    • Soaking: has the purpose to give the hide back the water that it had lost in the preservation process, and to eliminate sodium chloride in the case of hides preserved by salting. This operation, as well as many of the subsequent ones in the process, is normally carried out in a "drum", a machine consisting of a cylinder rotating around its axis into which the hides to be treated are introduced together with water and/or the chemicals necessary for the specific operation. In the case of soaking, the hides are treated with water and varying amounts of surfactants;
    • Liming: this is one of the fundamental operations of the tanning process, and allows various effects to be obtained. This operation is carried out by treating the hides with calcium hydroxide (Ca(OH)2), which brings the pH of the bath to values around 12.5, in the presence of reducing agents, particularly sodium sulphide (Na2S). The main effects of liming are the depilation of the hide and its swelling and turgidity due to osmotic pressure caused by the high concentration of Na+, Ca2+ and OH- ions. Other effects of this operation are the elimination from the hide of part of the natural fats (by saponification) and of the globular proteins (by solubilisation), which could interfere with the subsequent operations; and the hydrolysis of part of the amide side groups of the collagen protein chain with the formation of free carboxylate groups (R-COO-) which are added to those already naturally present on the collagen molecules, increasing the possibilities of binding with the tanning metal and consequently facilitating tanning;
    • Deliming: the calcined hide is swollen and strongly alkaline, and in this state could not be subjected to the subsequent chemical operations. Deliming serves to lower the pH of the hide to around 8-9, eliminate swelling and turgidity, and eliminate calcium hydroxide and sodium sulphide. This operation is carried out with mildly acidic chemicals. Ammonium sulphate is generally used for cowhides, but other products such as weak organic acids (lactic acid, glycolic acid, etc.), sulphophthalic acid, sodium bisulphite and the like, or mixtures of these compounds, may also be used;
    • Maceration: Maceration is an enzymatic operation whose purpose is to complete deliming, eliminate residues of other unhelpful interfibrillar substances, loosen the fibrous structure of the hide so as to facilitate the expulsion of the pigments (melanins) and hair roots remained still embedded in the hide and produce a softer leather. Baths of animal pancreatic enzymes, possibly obtained from bacteria modified by genetic engineering, can be used for the operation. This operation can be carried out mildly, or not at all, if the intention is to produce a stiff and little flexible leather;
    • Pickling: in this operation, the pH of the hide is brought to a value between about 3 and 4, generally using a mixture of sulphuric and formic acids, to prepare it for tanning. The aim is both to prevent the formation of chromium hydroxides (which occurs at pH values above 4-4.5), which would make the addition of the element useless, and to neutralize the free carboxylate groups produced in the liming step by forming R-COOH carboxyl groups. The reason is that carboxylate groups are extremely reactive towards tanning metals, particularly Cr3+ ions, so that the reaction would occur very quickly and effectively with the carboxylate groups on the surface of the hide, preventing further penetration of the tanning agent into the hide. To avoid the osmotic swelling of the hide that would occur at these pH values, high amounts of sodium chloride are also added to the bath, between 5 and 15%, typically between 6 and 8%, by weight of the hide; on this subject, see for example the book Tanning Chemistry: The Science of Leather quoted above, paragraph 9.2.2, which indicates 6% by weight as the minimum amount of sodium chloride to be used in pickling;
    • Tanning: finally, the hide deriving from the pickling process is subjected to the actual tanning process, the chemical operation that transforms the still putrescible hide into an imputrescible material, i.e. leather. There are many types of tanning, but the most common ones are chrome tanning (about 80-90% of all the leathers produced worldwide are chrome tanned) and tanning with mixtures of synthetic and vegetable tannins, aldehydes, particularly glutaraldehyde, and metallic salts, particularly of aluminium and zirconium. The product obtained by chrome tanning has a light blue-green colour and is referred to in the industry as "wet blue", while tanning by mixtures of tannins, aldehydes and metallic salts (of metals other than chrome) gives an essentially white product and the product obtained is referred to as "wet white".


    [0005] In addition to these fundamental steps, a tanning process may comprise other steps, such as fleshing (mechanical removal of residues of subcutaneous tissues), carried out before or, preferably, immediately after liming; splitting in the case of very thick hides (typically cowhides, while thinner sheep hides do not require or do not allow this operation), also carried out after liming and which consists in forcing the hide, by passing between two rollers, against a blade which divides it into two layers in a parallel manner to its surface; and degreasing, an operation carried out (normally using surfactants) between maceration and tanning when necessary, i.e. in the case of hides still containing high amounts of fat after maceration which could interfere with the tanning.

    [0006] As described above, pickling is a fundamental and necessary step in known tanning processes, but it is also one of the steps that causes the greatest environmental problems; after this step, a solution containing sulphates and, above all, high amounts of sodium chloride are discharged. Purification plants are able to reduce practically all the pollutants present in the waste water of the tanning processes, except for sodium chloride which therefore remains in the waste water. Sodium chloride is not a toxic or harmful product, but it strongly alters the environment of rivers and lakes into which the discharges of the tanning plants flow, with strong impacts on the flora and fauna of these environments.

    [0007] Patent application US 2005/0268671 A1 describes a process for the tanning of hides which has the stated purpose of achieving a better fixation of chromium salts in the wet blue tanning, and thus a lower dispersion of these salts in the environment. According to the document, this would be possible with a step of preparation for tanning carried out at higher pH values than those traditionally adopted, and which further makes it possible to reduce or even avoid the use of sodium chloride in the pickling step. In spite of this statement in the general description, in the examples sodium chloride is always used in relevant amounts, between 5 and 7% with respect to the weight of the hide, which are characteristic of the pickling steps of the prior art; moreover, no indicative data is reported on the quality, type (e.g. of cow, sheep, goat, etc.) and weight check (e.g. of cow 36 kg+ or above 40 kg, etc.) of the hides obtained according to the described tanning process.

    [0008] The object of the present invention is to provide a process for the tanning of hides that avoids the pickling step and thus the use of sodium chloride. Another object of the invention is to provide hides tanned according to this process.

    SUMMARY OF THE INVENTION



    [0009] This object is achieved by the present invention, which in a first aspect thereof relates to a process for the tanning of hides which includes the steps of soaking, liming, deliming, maceration, preparation for tanning, and tanning, characterized in that in the step of preparation for tanning the hides are treated with a liquid mixture consisting of:
    • water in an amount between 40 and 60% by weight with respect to the weight of the hide;
    • between 0.5 and 2.5% by weight with respect to the weight of the hide of an emulsion containing between 45 and 60% by weight of water and between 40 and 55% by weight of an oil consisting of one or more sulphonates of general formula R-SO3H, wherein R is a C4-C20 alkyl radical;
    • between 0.2 and 1.5% by weight with respect to the weight of the hide of a mixture of C4-C6 dicarboxylic acids containing between 10 and 30% by weight of succinic acid, between 40 and 60% by weight of glutaric acid and between 15 and 35% by weight of adipic acid; and
    • a salt selected from sodium acetate and sodium formate or mixtures thereof in an amount between 1 and 2% by weight with respect to the weight of the hide.


    [0010] In its second aspect, the invention concerns a hide tanned by the process described above.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0011] Fig. 1 shows schematically the experimental set-up for measuring the quality of a tanned hide (measurement of shrinkage temperature).

    DETAILED DESCRIPTION OF THE INVENTION



    [0012] The inventor has found that the treatment characteristic of the process of the invention, carried out with the mixture of water, an emulsion of sulphonates, C4-C6 dicarboxylic acids and sodium acetate and/or formate, makes it possible to avoid the pickling operation carried out in the processes of the prior art, and which as described above is one of the main sources of pollution in the tanning industry.

    [0013] In the following description and in the claims, unless otherwise indicated, all concentrations and purities are given as percentage values by weight. In addition, all amounts of compounds used in the various steps of the process are expressed as percentages by weight with respect to the weight of the hide treated in that step (the weight of the hide may vary during the process, e.g. as a result of fleshing or splitting).

    [0014] The process of the invention comprises a series of steps carried out according to traditional methods, with the pickling being replaced by the characterising step mentioned above.

    [0015] A typical process of the invention includes steps of soaking, liming, deliming, maceration, preparation for tanning, and tanning carried out as described below.

    [0016] Soaking is carried out with a first step of continuous washing with running water for one hour or discontinuously, for example with the addition of two successive aliquots of water each in an amount of about twice the weight of the hide; and a second step of treatment in a drum with an amount of water of about twice the weight of the hide, for 16-24 hours. In the second step, salts can be added to the water to give the solution a basic pH, e.g. sodium bicarbonate, or surfactant detergents. The temperature of the soaking step is preferably around 20-25 °C, and in any case not higher than 45 °C; in case of temperatures higher than 25 °C, an antibacterial product (anti-mould agent) must be added to the water to prevent the proliferation of micro-organisms that could alter the hide.

    [0017] The liming step can be carried out in any way known in the industry. This step is preferably carried out at room temperature, with a weight of water about double that of the hide to be treated, Ca(OH)2 in an amount between 3 and 5%, and sodium sulphide (Na2S) normally between 2 and 3% or sodium hydrosulphide (NaHS) in an amount between 0.5 and 1%. This step is protracted for a time between 18 and 36 hours, commonly between 21 and 24 hours.

    [0018] The deliming step is carried out at a temperature of about 30 to 38 °C, preferably in two successive phases, each carried out with an amount of water equal to the weight of hide to be treated, by draining the water between one phase and the next, and in which the second phase is carried out at a slightly higher temperature (e.g., 2 °C) than the first. The total time of the deliming step is about 3 to 4 hours. In this step are used altogether, subdivided into the two phases:
    • a mixture containing between 40 and 45% of ammonium chloride (NH4Cl), between 20 and 30% of one or more C4-C6 dicarboxylic acids, and between 0.5 and 1.5% of sulfamic acid (H2NSO3H), with the balance to 100% consisting of ammonium sulphate ((NH4)2SO4); this mixture is added in this step in amounts between about 0.8 and 1.5% in the case of split hides and between 1.5 and 3% in the case of unsplit hides;
    • ammonium sulphate between about 0.4 and 1.0%; and
    • between 0.3 and 1.5% of a degreaser known in the field. As an example of a degreaser, one can mention a liquid mixture consisting of about 54-58% by weight of 2-propylethyl alcohol ethoxylate (a commercially available component with CAS registry no. 160875-66-1), between 2 and 3% of sodium salts of sulphates of C12-C14 alcohol ethoxylates (CAS no. 68891-38-3) and between 0.01 and 0.04% of 1,2-benzisothiazol-3(2H)-one (CAS no. 2634-33-5); also in this mixture the balance to 100% consists of ammonium sulphate.


    [0019] The maceration step is carried out at a temperature between 30 and 37 °C, with amounts of water between about 0.5 and 1.5 times the weight of the hide to be treated, for a total time between 3 and 5 hours. This step is completed by a series of washes, carried out with an amount of water between 2 and 4 times the weight of the hide. Pancreatic enzymes are added to the water of the maceration step in amounts between 0.1 and 2%. In this step, or in the subsequent washes (two or three, each lasting from 10 to 20 minutes), other components may be added to the water, for example up to about 0.5% by weight of a degreaser (e.g. the mixture of 2-propylethyl alcohol ethoxylate, sodium salts of sulphates of C12-C14 alcohol ethoxylates, 1,2-benzylisothiazol-3(2H)-one and ammonium sulphate mentioned above), up to 1.2% of the mixture of ammonium chloride, C4-C6 dicarboxylic acids and sulfamic acid mentioned above, about 0.2% by weight of ammonium sulphate and up to about 0.4% by weight of hydrogen peroxide.

    [0020] The characterizing step of the process of the invention is the preparation for tanning one, which is carried out without using sodium chloride.

    [0021] This step is carried out at a temperature between 15 and 25 °C, preferably at 20 °C, for a time between 1 and 2.5 hours, with an amount of water between 40 and 60% with respect to the weight of the hides to be treated.

    [0022] As mentioned above, in this step water is added with:
    • between 0.5 and 2.5% of an emulsion containing between 45 and 60% by weight of water and between 40 and 55% by weight of an oil consisting of one or more sulphonates of general formula R-SO3H, wherein R is a C4-C20 alkyl radical, preferably a C6-C14 radical, and even more preferably a C12-C14 radical;
    • between 0.2 and 1.5% of a mixture of C4-C6 dicarboxylic acids containing between 10 and 30% by weight of succinic acid, between 40 and 60% by weight of glutaric acid and between 15 and 35% by weight of adipic acid; and
    • a salt selected from sodium acetate and sodium formate in an amount between 1 and 2%.


    [0023] An antibacterial product can be added to the treatment water in amounts between 0.1 and 0.2%. Antibacterial (or anti-mould) products for tanning processes are widely available commercially; a possible product of this type comprises 25-35% by weight of sodium salt of 4-chloro-3-methylphenol, 8-12% of 2-phenylphenol, 11-15% of diethylene glycol and 12-14% of sodium hydroxide, with water as a 100% complement.

    [0024] In addition to avoiding pickling and the consequent release of sodium chloride into the environment, the step before tanning of the invention offers other environmental advantages.

    [0025] The sulphonate-based oil described above has a very low content of volatile organic compounds (often also indicated with the corresponding abbreviation VOC). A low VOC value of the tanned hides allows having a very low environmental impact, both in domestic use and in the workplace, and even more so in small spaces such as aircraft, ship hulls and especially car interiors. Due to the commercial importance of the automotive sector, standards for the assessment of emissions have been developed particularly for this industry, the reference standards being VDA 277:1995-01 (based on the measurement of the equilibrium composition of the atmosphere in an enclosed space above the sample after static heating to 120 °C for 5 hours) and VDA 278:2011 (based on the thermal desorption method); the method VDA 278:2011 also allows determining the release of condensable volatile compounds (referred to in the sector as FOG). For the automotive application, the tanned hide is typically subjected to further treatments such as retanning, after which it is pressed, split, shaved up to the thickness of 1.1-1.2 mm and finally subjected to analytical checks of the release of volatile compounds; tests of this type carried out on the hides tanned by the process of the invention have resulted in VOC values equal to or less than 0.01% by weight of the sulphonated oil used.

    [0026] Finally, the process of the invention comprises the actual tanning step.

    [0027] This step is carried out by adding the compounds listed below directly to the bath derived from the previous step, which is not unloaded from the drum.

    [0028] Tanning generally lasts between 16 and 20 hours and requires the use of various compounds added to the bath at different times. The compounds used and the timings of their additions vary depending on whether the tanning is for wet blue productions or the tanning is for wet white productions.

    [0029] In the case of wet blue tanning, a Cr3+ salt, e.g. basic chromium (III) sulphate (Cr(OH)SO4), possibly in a mixture with sodium sulphate, in an amount between 5 and 8%, between 0.5 and 0.8% of the above-described mixture of succinic, glutaric and adipic acids and about 0.2% of an anti-mould agent are added to the bath, leaving the system under rotation in the drum for 8 hours. Formic acid is then added in amounts between 0.3 and 0.5% allowing to react for 2 hours. An anti-mould agent (0.1%) and an alkaline compound (0.4%), which has the function of stabilising and fixing the chromium on the protein fibres of the hide, are then added, allowing to react for 4 hours; commonly the alkaline compound is calcium oxide or a mixture containing it. Finally, one or more washes are carried out with cold water (20 °C) in a total amount of about one and a half times the weight of the hide, with possible additions of small amounts (0.1% each) of formic acid and anti-mould agent, for a total time of about 2 hours and a half. Finally, the drum is unloaded and the hides are recovered and sent to the steps following the tanning.

    [0030] In the case of wet white tanning (with tannins), a tanning agent, generally a phosphonium salt or a mixture of phosphonium salts (e.g. tetrakis(hydroxymethyl)phosphonium sulphate, (P(CH2OH)4)2SO4) in an amount between 2 and 4% and an anti-mould agent in an amount between 0.3 and 0.5% are initially added, and the drum is rotated for at least three hours; the tanning agent is generally used in the form of a 50% by weight aqueous solution. The hides are then allowed to rest in the bath without rotation for about 8 hours (conveniently, this step is carried out overnight). Next, sodium bicarbonate (NaHCO3) is added in two successive aliquots of about 0.5% each; the second addition of bicarbonate is carried out about half an hour after the first one. Finally, after about an hour and a half, sodium percarbonate is added in an amount between 1.0 and 1.5% and the system is allowed to rest for about an hour and a half. Finally, the drum is unloaded and are added water at 40 °C in an amount by weight about the same as that of the hide, tannins (natural or synthetic) in an amount of about 4-5%, between 0.1 and 0.8% of an emulsion containing between 45 and 60% by weight of water and between 40 and 55% by weight of an oil consisting of one or more sulphonates of general formula R-SO3H, wherein R is a C4-C20 alkyl radical (preferably C6-C14, more preferably C12-C14), and an amount between 0.1 and 0.2% of an anti-mould agent. The system is allowed to react in the drum under stirring for about three hours, after which the drum is unloaded and the hides are washed with an amount of cold water equal to about twice the weight of the hides for about 10 minutes, finally unloading the drum and recovering the hides which are sent to the steps following the tanning.

    [0031] In its second aspect, the invention concerns a hide tanned by the process described above.

    [0032] The tanned hide of the invention exhibits chemical stability (resistance to rot) and physical-mechanical characteristics comparable to, or even better than, the hides obtained by conventional tanning processes. Furthermore, the hides obtained by this process consistently showed a shrinkage temperature, Tg, above 75 °C in the case of tanning with tannins, and above 100 °C in the case of chromium tanning.

    [0033] The invention will be further described by the following experimental part.

    [0034] The samples of hide tanned by the process of the invention are tested in the examples by measuring the shrinkage temperature according to ISO 3380.

    [0035] In short, the method consists of slowly heating a specimen in water and measuring the temperature at which a sudden shrinkage of the sample occurs. The instrument for carrying out the test is shown schematically in Fig. 1. The sample, 10, is completely immersed into water, initially at a temperature of 20 ± 2 °C, inside a container 11; the lower end of the sample is blocked with a fixed clamp 12, while the upper end is hooked to a mobile clamp 13 connected to a movement indicator 14 (an index pivoted at one end at the centre of a quadrant 15); a sample pretensioner 16, which exerts on the sample a force equivalent to a weight of 3 g, is also connected to the same axis on which the index is pivoted. Immersed in the water, near the centre of the sample, there is a thermometer 17 (in the set-up used in the tests, the thermometer was an IKA® ETS-D5 electronic digital thermometer, from the company IKA®-Werke GmbH & Co. KG, Staufen, Germany). To carry out the test, the temperature of the water is raised slowly (2 °C/min) by means of an electric heater in a glass or quartz sheath, immersed in the water in the lower part of the container (not shown in the figure). When the shrinkage temperature, indicated in the sector as Tg, is reached, the sample undergoes a sudden and irreversible shrinkage, which is visualised by the shift of the indicator 14. The measurement has an accuracy of ± 0.5 °C.

    EXAMPLE 1



    [0036] This example refers to the preparation of a wet blue tanning process (with chromium) according to the invention.

    [0037] The amounts of added components are indicated as a percentage by weight with respect to the weight of the hide. All process steps are carried out under continuous stirring, by rotation of the drum, except for the step of unloading of the different baths from the drum itself or some steps (identified in the description below) lasting overnight, during which the drum is rotated intermittently for a few minutes every hour or half an hour.

    [0038] Two full-thickness fleshed-out calf hides, weighing 65 kg in total (for an average weight of more than 30 kg), which had already undergone the soaking and liming processes, were introduced into a drum.

    [0039] The deliming step was carried out in three successive steps.

    [0040] In the first step it was added to the drum:
    • 100% water at 30 °C;
    • 0.6% ammonium sulphate;
    • 1,3% of a powdered mixture containing C4-C6 dicarboxylic acids, ammonium chloride, sulfamic acid and ammonium sulphate, in which the dicarboxylic acids are present at 30% by weight; and
    • 0.2% non-ionic degreaser consisting of 2-propylethyl alcohol ethoxylate (content in the mixture 58%), 3% sodium salts of sulphates of C12-C14 alcohol ethoxylates and 0.04% 1,2-benzylisothiazol-3(2H)-one, the balance to 100% consisting of ammonium sulphate.


    [0041] After an hour of treatment, this solution was unloaded from the drum.

    [0042] The second phase of the deliming step was carried out under the same conditions and in the same way as the first step, the only difference being that the water temperature was 34 °C.

    [0043] In the third phase of the deliming step, the same components as in the first two steps were used, but in different amounts: 50% water at 36 °C, 3% of the mixture containing the C4-C6 dicarboxylic acids, 0.5% ammonium sulphate and 0.25% of the above-mentioned degreasing mixture were used; treatment in this third step was continued for two hours, at the end of which the drum was not unloaded from the solution.

    [0044] Maceration was then carried out. For this purpose, 0.2% of the mixture containing dicarboxylic acids described above and 0.2% of ammonium sulphate were added to the bath of the last delim ing step (at 36 °C) and the hides were treated with this solution for 30 minutes; then 1% of a commercial pancreatic enzyme was added and the treatment was continued for 90 minutes; finally the bath was unloaded from the drum.

    [0045] Before the step of the preparation for tanning, two washes were carried out, the first one lasting 20 minutes with 100% water at 20 °C and 0.3% of the above-mentioned degreasing mixture, followed by drum unloading; the second wash was carried out with sole water (100%) at 20 °C for 10 minutes followed by drum unloading.

    [0046] The step of the preparation for tanning, characteristic of the invention, was then carried out. Water at 20 °C (amount 50%) and 1% of an emulsion containing 52% by weight of water and between 48% by weight of an oil consisting of a mixture of sulphonates of general formula R-SO3H, wherein R is a C12-C14 alkyl radical, was added to the drum; the treatment continued for 20 minutes. 1% sodium acetate and 0.5% of a mixture of powdered C4-C6 dicarboxylic acids were then added and the treatment continued for two hours. The system was then allowed to rest overnight, with the drum rotating for only 5 minutes every hour.

    [0047] In the morning, 0.65% of powdered C4-C6 dicarboxylic acids was added and the treatment was continued for 10 minutes. Then 0.2% of an anti-mould agent and 6.5% of a powder mixture containing 67% by weight of sodium sulphate and 33% by weight of basic chromium (III) sulphate (CrOHSO4) were added, initially allowing the system to stir continuously for 8 hours, and then to rest (stirring for 3 minutes every 30 minutes) overnight.

    [0048] The next morning, 0.4% formic acid was added and the treatment continued for 2 hours. 0.1% of anti-mould agent and 0.4% of calcium oxide were then added to raise the pH and fix the chromium, continuing the treatment for 4 hours.

    [0049] Water was then added at 38 °C (50% amount) for two hours, the drum was unloaded, a 5-minute wash with 100% water at 20 °C was carried out and the drum was unloaded.

    [0050] Finally, 100% water at 20 °C, 0.1% of formic acid, 0.1% of anti-mould agent were introduced into the drum and the treatment was continued for 20 minutes. At the end of this treatment the drum was unloaded, the hides were extracted, pressed and stretched to dry on suitable pallets.

    [0051] The dried hides had a clear blue tone, were well stretched without wrinkles or curves, and were very easy to machine mechanically; with regard to appearance and workability, the hides tanned by the process of the invention are at least comparable to, if not even better than, the wet blue hides obtained by the conventional process with pickling. A sample of hide produced in this example was also subjected to a shrinkage temperature measurement (Tg): no shrinkage occurred up to the maximum temperature allowed by the instrument; the shrinkage temperature of the sample is therefore above 100 °C, confirming the excellent preservation properties over time of the tanned hide.

    EXAMPLE 2



    [0052] This example refers to the preparation of a wet white tanning process (with tannins) according to the invention.

    [0053] As in Example 1, the amounts of added components are indicated as a percentage on the weight of the hide and all the steps of the process take place under stirring by continuous rotation of the drum except the unloading steps or the intermittent stirring steps.

    [0054] Two full-thickness fleshed-out calf hides, weighing 62 kg in total (average weight of more than 30 kg) which had already undergone soaking and liming processes, were introduced into a drum.

    [0055] The hides were subjected to an initial 20-minute washing treatment with 100% water at 30 °C which was then unloaded from the drum.

    [0056] The deliming step was carried out in two successive steps.

    [0057] In the first step it was added to the drum:
    • 100% water at 34 °C;
    • 0.4% ammonium sulphate;
    • 1,0% of a powdered mixture containing C4-C6 dicarboxylic acids, ammonium chloride, sulfamic acid and ammonium sulphate, in which the dicarboxylic acids are present at 30% by weight; and
    • 0.4% non-ionic degreaser consisting of 2-propylethyl alcohol ethoxylate (content in the mixture 58%), 3% sodium salts of sulphates of C12-C14 alcohol ethoxylates and 0.04% 1,2-benzylisothiazol-3(2H)-one, the balance to 100% consisting of ammonium sulphate.


    [0058] After half an hour of treatment, this solution was unloaded from the drum.

    [0059] The second step of the deliming step was carried out with 100% water at 36 °C by successive additions of components in the same solution.

    [0060] Initially, 0.6% of the 30% dicarboxylic acid mixture, 0.1% of the non-ionic degreaser described above were added and the hides were treated under these conditions for 15 minutes. A second aliquot of 0.6% of the 30% dicarboxylic acid mixture was then added and allowed to react for 60 minutes. A third aliquot of 0.6% of mixture of 30% dicarboxylic acids was added and allowed to react for 30 minutes. Finally, a fourth aliquot of 0.3% of mixture of 30% dicarboxylic acids and 0.5% of ammonium sulphate were added and allowed to react for 90 minutes.

    [0061] Maceration was then carried out by adding 0.2% of a mixture of 30% dicarboxylic acids and 1% of a commercial pancreatic enzyme to the same solution deriving from deliming and the treatment was continued for 90 minutes, finally unloading the solution from the drum.

    [0062] Prior to the step of the preparation for tanning, two washes were performed, the first one lasting 20 minutes with 200% water at 20 °C followed by drum unloading; the second wash was performed with 200 °C water at 20 °C and 0.2% hydrogen peroxide for 20 minutes followed by drum unloading.

    [0063] The step of the preparation for tanning, characteristic of the invention, was then carried out. Water at 20 °C (amount 50%), 0.15% of anti-mould agent and 1.5% of an emulsion containing 52% by weight of water and between 48% by weight of an oil consisting of a mixture of sulphonates of general formula R-SO3H, wherein R is a C12-C14 alkyl radical, were added to the drum; the treatment continued for 20 minutes. Then 0.5% of a mixture of powdered C4-C6 dicarboxylic acids was added, continuing the treatment for 20 minutes, followed by 2% of sodium formate, continuing the treatment for a further 20 minutes.

    [0064] The tanning treatment was then carried out.

    [0065] To this end, 3% of phosphonium salts and 0.35% of anti-mould agent were added to the bath described above and the system was allowed to react initially for three hours and then throughout the night.

    [0066] The next morning, a first aliquot of 0.5% of sodium bicarbonate was added to the bath, allowing it to react for 30 minutes, followed by a second aliquot of 0.5% of sodium bicarbonate, allowing it to react for two hours.

    [0067] 1.2% of sodium percarbonate (tanning stabiliser) was then added and the system was allowed to react for 90 minutes, with the bath then unloaded from the drum.

    [0068] Finally, 200% water at 40 °C, 4% of commercial tannins, 0.15% of an anti-mould agent and 0.5% of an emulsion containing 52% by weight of water and between 48% by weight of an oil consisting of a mixture of sulphonates of general formula R-SO3H, wherein R is a C12-C14 alkyl radical, were added and the system was allowed to react for three hours.

    [0069] Finally, the drum was unloaded from the bath, a washing with 200% of water at 20 °C for 10 minutes was carried out, and the hides were extracted and dried.

    [0070] The dried hides were cream to white in colour, were well stretched without wrinkles or creases, and were easy to machine mechanically; in these respects the hides tanned by the process of the invention are at least comparable to, if not even better than, the wet white hides obtained by the processes of the prior art.

    [0071] The shrinkage temperature of a sample of hide thus obtained was measured and found to be equal to 78 °C, confirming the excellent preservation properties over time.

    [0072] Some samples obtained from the thus tanned hides were also subjected to volatile organic compound (VOC) emission measurements. A hide from this example was pressed, split and shaved up to a thickness of 1.1-1.2 mm, and a sample was taken from it and subjected to measurement using the method VDA 278:2011, and emissions of organic compounds equal to VOC 249 mg/Kg (expressed as toluene) and FOG 1373 mg/Kg (expressed as C16 hydrocarbons) were found. The second hide of the example was treated in the same way as the first hide, and three samples were taken from it and measured using the method VDA 277:1995-01, finding in the three measurements release values of volatile organic compounds equal to 22.8 µgC/g, 21.8 µgC/g and 20.9 µgC/g, respectively (the measurement unit µgC/g indicates the µg of carbon in the VOCs emitted per g of sample).

    Commentaries on the results



    [0073] As shown in the examples, with the process of the invention it is possible to obtain tanned hides having chemical stability (resistance to rot) and physical-mechanical characteristics comparable to, or even better than, hides obtained by conventional tanning processes.

    [0074] The process of the invention makes it possible, in an unexpected way, to achieve this result without the need for a pickling step, with the consequent elimination from the process wastewater of acids such as sulphuric, formic and in some cases also hydrochloric acid, and the reduction in this water of 6-8% (by weight of the hides) of sodium chloride.

    [0075] This allows to obtain the same results obtained with traditional tanning, but with a notable reduction of chlorides, sulphates, and COD ("Chemical oxygen demand"); this last parameter is the overall measure of oxidizable organic and inorganic substances present in a water sample, and therefore gives an indication of the total amount of potential pollutants contained in the water itself.

    [0076] In addition, the use of the special sulphonated oils in the characteristic process step, alternative to pickling, also enables a significant reduction in VOC and FOG (volatile organic compound emissions) values to be obtained in the final product.


    Claims

    1. Process for the tanning of hides which includes the steps of soaking, liming, deliming, maceration, preparation for tanning, and tanning, characterized in that in the step of preparation for the tanning the hides are treated with a liquid mixture consisting of:

    - water in an amount between 40 and 60% by weight with respect to the weight of the hide;

    - between 0.5 and 2.5% by weight with respect to the weight of the hide of an emulsion containing between 45 and 60% by weight of water and between 40 and 55% by weight of an oil consisting of sulphonates of general formula R-SO3H, wherein R is a C4-C20 alkyl radical;

    - between 0.2 and 1.5% by weight with respect to the weight of the hide of a mixture of C4-C6 dicarboxylic acids containing between 10 and 30% by weight of succinic acid, between 40 and 60% by weight of glutaric acid and between 15 and 35% by weight of adipic acid; and

    - a salt selected from sodium acetate and sodium formate in an amount between 1 and 2% by weight with respect to the weight of the hide.


     
    2. Process according to claim 1 wherein R is a C12-C14 alkyl radical.
     
    3. Process according to any one of the preceding claims wherein an antibacterial component is added to the liquid mixture of the step of preparation for tanning, in an amount between 0.1 and 0.2% by weight with respect to the weight of the hide.
     
    4. Process according to claim 3 wherein said antibacterial component comprises 25-35% by weight of sodium salt of 4-chloro-3-methylphenol, 8-12% of 2-phenylphenol, 11-15% of diethylene glycol and 12-14% of sodium hydroxide, with water as a 100% complement.
     
    5. Process according to any one of the preceding claims, wherein the soaking step is carried out with a first step of continuous washing with running water for one hour or of discontinuous washing with the addition of two successive aliquots of water each in an amount of about twice the hide weight; and a second step of treatment in a drum with an amount of water of about twice the weight of the hide, at a temperature between 20 and 45 °C, for 16-24 hours, possibly with the addition of surfactant detergents and/or salts which give the solution a basic pH.
     
    6. Process according to claim 5 wherein when the treatment in the drum is carried out at a temperature above 25 °C, an antibacterial component is added to the water, and in which the salt which gives basic pH to the water is sodium bicarbonate.
     
    7. Process according to any one of the preceding claims, wherein the liming step is carried out at room temperature, for a time between 18 and 36 hours, with a weight of water about double that of the hide to be treated, Ca(OH)2 in an amount between 3 and 5% with respect to the weight of the hide to be treated, and a compound selected from sodium sulphide (Na2S) used in an amount between 2 and 3% with respect to the weight of the hide to be treated and sodium hydrosulphide (NaHS) in an amount between 0.5 and 1% by weight with respect to the hide to be treated.
     
    8. Process according to any one of the preceding claims, wherein the deliming step is carried out at a temperature between 30 and 38 °C in two successive phases, each carried out with an amount of water equal to the weight of hide to be treated, by draining the water between one phase and the next, and in which the second phase is carried out at a higher temperature than the first one, in an overall time between 3 and 4 hours, using, possibly subdivided into the two phases:

    - between 0.8 and 1.5% with respect to the weight of the hide in the case of split hides, and between 1.5 and 3% with respect to the weight of the hide in the case of non-split hides, of a mixture containing between 40 and 45% of ammonium chloride (NH4Cl), between 20 and 30% of one or more C4-C6 dicarboxylic acids, and between 0.5 and 1.5% of sulfamic acid (H2NSO3H), with the balance to 100% consisting of ammonium sulphate (NH4SO4H);

    - between 0.4 and 1.0% with respect to the weight of the hide of ammonium sulphate; and

    - between 0.3 and 1.5% with respect to the weight of the hide of a degreaser.


     
    9. Process according to claim 8, wherein said degreaser is a liquid mixture consisting of 54-58% by weight of 2-propylethyl alcohol ethoxylate (CAS 160875-66-1), between 2 and 3% of sodium salts of sulphates of C12-C14 alcohol ethoxylates (CAS 68891-38-3), between 0.01 and 0.04% of 1,2-benzylisothiazol-3(2H)-one (CAS 2634-33-5), the balance to 100% consisting of ammonium sulphate.
     
    10. Process according to any one of the preceding claims, wherein the maceration step is carried out at a temperature between 30 and 37 °C, for a total time between 3 and 5 hours, with an amount of water between 0.5 and 1 times the weight of the hide to be treated, to which an amount between 0.5 and 1.5% by weight with respect to the weight of the hide of pancreatic enzymes is added, and in which said maceration step is followed by two or three washes, each lasting between 10 and 20 minutes, with a total amount of water between 2 and 4 times the weight of the hide.
     
    11. Process according to any one of the preceding claims, wherein in the maceration step or in the subsequent washing steps one or more components are added selected from:

    - up to 0.5% by weight of a degreaser;

    - up to 1.2% of a mixture containing between 40 and 45% of ammonium chloride (NH4Cl), between 20 and 30% of one or more C4-C6 dicarboxylic acids, and between 0.5 and 1.5% of sulfamic acid (H2NSO3H), with the balance to 100% consisting of ammonium sulphate (NH4SO4H);

    - up to 0.2% by weight of ammonium sulphate; and

    - up to 0.4% by weight of hydrogen peroxide.


     
    12. Process according to any one of the preceding claims, wherein the tanning step is carried out as chrome tanning according to the following steps:

    - addition in the bath derived from the previous step of a Cr3+ salt in an amount between 5 and 8% with respect to the weight of the hide, possibly mixed with sodium sulphate, between 0.5 and 0.8% with respect to the weight of the hide of a mixture of C4-C6 dicarboxylic acids containing between 10 and 30% by weight of succinic acid, between 40 and 60% by weight of glutaric acid and between 15 and 35% by weight of adipic acid, and between 0.1 and 0.3% with respect to the weight of the hide of an antibacterial component, allowing the system to react under stirring for at least 8 hours;

    - addition of formic acid in an amount between 0.3 and 0.5% with respect to the weight of the hide, allowing the system to react under stirring for at least 2 hours;

    - addition of an antibacterial agent in an amount between 0.1 and 0.2% with respect to the weight of the hide and of a basic chromium-stabilizing compound in an amount between 0.2 and 0.5% with respect to the weight of the hide, allowing the system to react under stirring for at least 4 hours and then unloading the drum from the solution contained therein;

    - one or more washes with cold water in a total amount of about one and a half times the weight of the hide, with possible additions of formic acid and antibacterial agent in amounts of up to 0.1% each with respect to the weight of the hide, for a total time of about 2 hours and a half, and finally unloading the drum and recovering the hides that are sent to the steps following the tanning.


     
    13. Process according to any one of claims 1 to 11, wherein the tanning step is carried out as tanning with tannins, according to the following steps:

    - addition in the bath derived from the previous step of a phosphonium salt or a mixture of phosphonium salts in an amount between 2 and 4% with respect to the weight of the hide and an antibacterial component in an amount between 0.3 and 0.5% with respect to the weight of the hide, allowing the system to react under stirring for at least 3 hours and then allowing the system to rest for at least 8 hours;

    - addition of sodium bicarbonate (NaHCO3) in two successive aliquots each for an amount between 0.25 and 1% with respect to the weight of the hide, allowing the system to react under stirring for at least half an hour;

    - addition of sodium percarbonate in an amount between 1.0 and 1.5% with respect to the weight of the hide, allowing the system to react under stirring for an hour and a half and then unloading the drum from the contained solution;

    - addition of water at 40 °C in an amount by weight between 0.8 and 1.2 times that of the hide, natural or synthetic tannins in an amount by weight between 3 and 6% with respect to the weight of the hide, between 0.1 and 0.8% with respect to the weight of the hide of an emulsion containing between 45 and 60% by weight of water and between 40 and 55% by weight of an oil consisting of sulphonates of general formula R-SO3H wherein R is a C4-C20 alkyl radical, and an antibacterial component in an amount ranging from 0.1 to 0.2% with respect to the weight of the hide, allowing the system to react under stirring for at least three hours and then unloading the drum from the solution contained therein;

    - washing the hides for a time between 5 and 20 minutes with cold water in an amount between 1.5 and 2.5 times the weight of the hides, finally unloading the drum and recovering the hides that are sent to the steps following the tanning.


     
    14. Hide tanned according to the process of any one of claims 1 to 13 having shrinkage temperature, measured according to the method defined in standard ISO 3380, higher than 100 °C in the case of wet blue hide and higher than 75 °C in the case of wet white hide.
     


    Ansprüche

    1. Verfahren zum Gerben von Häuten, das die Schritte zum Einweichen, Kälken, Entkälken, Mazerierens Vorbereiten für das Gerben und Gerben beinhaltet, dadurch gekennzeichnet, dass die Häute im Schritt zum Vorbereiten für das Gerben mit einer flüssigen Mischung behandelt werden, die aus Folgendem besteht:

    - Wasser in einer Menge zwischen 40 und 60 Gew.-%, bezogen auf das Gewicht der Haut;

    - zwischen 0,5 und 2,5 Gew.-%, bezogen auf das Gewicht der Haut, einer Emulsion, die zwischen 45 und 60 Gew.-% Wasser und zwischen 40 und 55 Gew.% eines Öls enthält, das aus Sulfonaten der allgemeinen Formel R-SO3H besteht, wobei R ein C4-C20-Alkylrest ist;

    - zwischen 0,2 und 1,5 Gew.-%, bezogen auf das Gewicht der Haut, einer Mischung von C4-C6-Dicarbonsäuren, die zwischen 10 und 30 Gew.-% Bernsteinsäure, zwischen 40 und 60 Gew.-% Glutarsäure und zwischen 15 und 35 Gew.-% Adipinsäure enthält, und

    - ein Salz, das aus Natriumacetat und Natriumformiat in einer Menge zwischen 1 und 2 Gew.-%, bezogen auf das Gewicht der Haut, ausgewählt ist.


     
    2. Verfahren nach Anspruch 1, wobei R C12-C14-Alkylrest ist.
     
    3. Verfahren nach einem der vorhergehenden Ansprüche, wobei ein antibakterieller Bestandteil in einer Menge zwischen 0,1 und 0,2 Gew.-%, bezogen auf das Gewicht der Haut, zu der flüssigen Mischung des Schrittes zum Vorbereiten für das Gerben zugegeben wird.
     
    4. Verfahren nach Anspruch 3, wobei der antibakterielle Bestandteil 25 bis 35 Gew.-% Natriumsalz von 4-Chlor-3-methylphenol, 8 bis 12 % 2-Phenylphenol, 11 bis 15 % Diethylenglykol und 12 bis 14 % Natriumhydroxid mit Wasser als 100 % Ergänzung umfasst.
     
    5. Verfahren nach einem der vorhergehenden Ansprüche, wobei der Einweichungsschritt mit einem ersten Schritt zum kontinuierlichen Waschen mit fließendem Wasser für eine Stunde oder zum diskontinuierlichen Waschens unter Zugabe von zwei aufeinanderfolgenden Aliquoten Wasser, jeweils in einer Menge von etwa dem Doppelten des Hautgewichts durchgeführt wird; und einem zweiten Schritt zur Behandlung in einer Trommel mit einer Wassermenge von etwa dem Doppelten des Hautgewichts bei einer Temperatur zwischen 20 und 45°C für 16-24 Stunden, möglicherweise unter Zugabe von Tensid-Detergenzien und/oder Salzen, die der Lösung einen basischen pH-Wert verleihen.
     
    6. Verfahren nach Anspruch 5, wobei, wenn die Behandlung in der Trommel bei einer Temperatur über 25°C durchgeführt wird, dem Wasser einen antibakteriellen Bestandteil zugegeben wird, und wobei das Salz, das dem Wasser einen basischen pH-Wert verleiht, Natriumbicarbonat ist.
     
    7. Verfahren nach einem der vorhergehenden Ansprüche, wobei der Kälkungsschritt bei Raumtemperatur für eine Zeit zwischen 18 und 36 Stunden mit einem Wassergewicht, das etwas das Doppelte dessen der zu behandelnden Haut, Ca(OH)2 in einer Menge zwischen 3 und 5 %, bezogen auf das Gewicht der zu behandelnden Haut, und einer Verbindung, ausgewählt aus Natriumsulfid (Na2S), das in einer Menge zwischen 2 und 3 %, bezogen auf das Gewicht der zu behandelnden Haut, verwendet wird, und Natriumhydrosulfid (NaHS) in einer Menge zwischen 0,5 und 1 Gew.-%, bezogen auf die zu behandelnde Haut, durchgeführt wird.
     
    8. Verfahren nach einem der vorhergehenden Ansprüche, wobei der Entkälkungsschritt bei einer Temperatur zwischen 30 und 38 °C in zwei aufeinanderfolgenden Phasen durchgeführt wird, die jeweils mit einer Wassermenge gleich dem Gewicht der zu behandelnden Haut durchgeführt werden, indem das Wasser zwischen einem Schritt und dem nächsten abgelassen wird, und wobei der zweite Schritt bei einer höheren Temperatur als die erste in einer Gesamtzeit zwischen 3 und 4 Stunden durchgeführt wird, wobei es gegebenenfalls in die beiden Schritten unterteilt wird:

    - zwischen 0,8 und 1,5 %, bezogen auf das Gewicht der Haut im Falle von gespaltenen Häuten, und zwischen 1,5 und 3 %, bezogen auf das Gewicht der Haut im Falle von nicht gespaltenen Häuten, einer Mischung, die zwischen 40 und 45 % Ammoniumchlorid (NH4Cl), zwischen 20 und 30 % einer oder mehrerer C4-C6-Dicarbonsäuren und zwischen 0,5 und 1,5 % Amidosulfonsäure (H2NSO3H) enthält, wobei der Rest zu 100 % aus Ammoniumsulfat (NH4SO4H) besteht;

    - zwischen 0,4 und 1,0 %, bezogen auf das Gewicht der Haut, von Ammoniumsulfat; und

    - zwischen 0,3 und 1,5 %, bezogen auf das Gewicht der Haut eines Entfettungsmittels.


     
    9. Verfahren nach Anspruch 8, wobei das Entfettungsmittel eine flüssige Mischung ist, bestehend aus 54-58 Gew.-% 2-Propylethylalkoholethoxylat (CAS 160875-66-1), zwischen 2 und 3 % Natriumsalzen von Sulfaten von C12-C14-Alkoholethoxylaten (CAS 68891-38-3), zwischen 0,01 und 0,04 % 1,2-Benzylisothiazol-3(2H)-on (CAS 2634-33-5), wobei der Rest zu 100 % aus Ammoniumsulfat besteht.
     
    10. Verfahren nach einem der vorhergehenden Ansprüche, bei dem der Mazerationsschritt bei einer Temperatur zwischen 30 und 37°C während einer Gesamtzeit zwischen 3 und 5 Stunden mit einer Wassermenge zwischen dem 0,5und 1-fachen des Gewichts der zu behandelnden Haut durchgeführt wird, der eine Menge zwischen 0,5 und 1,5 Gew.-%, bezogen auf das Gewicht der Haut, an Pankreasenzymen zugegeben wird, und wobei auf den Mazerationsschritt zwei oder drei Waschungen, die jeweils zwischen 10 und 20 Minuten dauern, mit einer Wassergesamtmenge zwischen dem 2- und 4-fachen des Gewichts der Haut folgen.
     
    11. Verfahren nach einem der vorhergehenden Ansprüche, wobei im Mazerationsschritt oder in den nachfolgenden Waschschritten einer oder mehrere Bestandteile zugegeben werden, ausgewählt aus:

    - bis zu 0,5 Gew.-% eines Entfettungsmittels;

    - bis zu 1,2 % einer Mischung, die zwischen 40 und 45 % Ammoniumchlorid (NH4Cl), zwischen 20 und 30 % einer oder mehrerer C4-C6-Dicarbonsäuren und zwischen 0,5 und 1,5 % Sulfaminsäure (H2NSO3H) enthält, wobei der Rest zu 100 % aus Ammoniumsulfat (NH4SO4H) besteht;

    - bis zu 0,2 Gew.-% Ammoniumsulfat; und

    - bis zu 0,4 Gew.-% Wasserstoffperoxid.


     
    12. Verfahren nach einem der vorhergehenden Ansprüche, wobei der Gerbungsschritt als Chromgerbung gemäß den folgenden Schritten durchgeführt wird:

    - Zugabe eines Cr3+ -Salzes in das aus der vorhergehenden Stufe abgeleitete Bad in einer Menge zwischen 5 und 8 %, bezogen auf das Gewicht der Haut, gegebenenfalls gemischt mit Natriumsulfat, zwischen 0,5 und 0,8 %, bezogen auf das Gewicht der Haut, einer Mischung von C4-C6-Dicarbonsäuren, enthaltend zwischen 10 und 30 Gew.-% Bernsteinsäure, zwischen 40 und 60 Gew.-% Glutarsäure und zwischen 15 und 35 Gew.-% Adipinsäure, und zwischen 0,1 und 0,3 %, bezogen auf das Gewicht der Haut, eines antibakteriellen Bestandteils, so dass das System unter Rühren mindestens 8 Stunden reagieren kann;

    - Zugabe von Ameisensäure in einer Menge zwischen 0,3 und 0,5%, bezogen auf das Gewicht der Haut, so dass das System unter Rühren für mindestens 2 Stunden reagieren kann;

    - Zugabe eines antibakteriellen Mittels in einer Menge zwischen 0,1 und 0,2% bezogen auf das Gewicht der Haut und einer basischen chromstabilisierenden Verbindung in einer Menge zwischen 0,2 und 0,5% bezogen auf das Gewicht der Haut, so dass das System unter Rühren für mindestens 4 Stunden reagieren und dann die Trommel aus der darin enthaltenen Lösung entladen werden kann;

    - eine oder mehrere Waschungen mit kaltem Wasser in einer Gesamtmenge von etwa dem anderthalbfachen des Gewichtes der Haut, mit möglichen Zugaben von Ameisensäure und antibakteriellem Mittel in Mengen von jeweils bis zu 0,1%, bezogen auf das Gewicht der Haut, für eine Gesamtdauer von etwa 2 Stunden und einer Hälfte, und schließlich Entladen der Trommel und Zurückgewinnen der Häute, die zu den Schritten nach dem Gerben geschickt werden.


     
    13. Verfahren nach einem der Ansprüche 1 bis 11, wobei der Gerbungsschritt als Gerbung mit Gerbstoffen gemäß den folgenden Schritten durchgeführt wird:

    - Zugabe eines Phosphoniumsalzes oder einer Mischung von Phosphoniumsalzen in das aus der vorhergehenden Stufe abgeleitete Bad in einer Menge zwischen 2 und 4 %, bezogen auf das Gewicht der Haut, und eines antibakteriellen Bestandteils in einer Menge zwischen 0,3 und 0,5 %, bezogen auf das Gewicht der Haut, in das Bad, wobei das System unter Rühren mindestens 3 Stunden reagieren und dann mindestens 8 Stunden ruhen kann;

    - Zugabe von Natriumbicarbonat (NaHCO3) in zwei aufeinanderfolgenden Aliquoten jeweils in einer Menge zwischen 0,25 und 1 %, bezogen auf das Gewicht der Haut, so dass das System unter Rühren für mindestens eine halbe Stunde reagieren kann;

    - Zugabe von Natriumpercarbonat in einer Menge zwischen 1,0 und 1,5% bezogen auf das Gewicht der Haut, so dass das System unter Rühren für eineinhalb Stunden reagieren und dann die Trommel aus der enthaltenen Lösung entladen werden kann;

    - Zugabe von Wasser bei 40 °C in einer Gewichtsmenge zwischen dem 0,8- und 1,2-fachen derjenigen der Haut, natürlichen oder synthetischen Tanninen in einer Gewichtsmenge zwischen 3 und 6 % bezogen auf das Gewicht der Haut, zwischen 0,1 und 0,8 % bezogen auf das Gewicht der Haut einer Emulsion, enthaltend zwischen 45 und 60 Gew.-% Wasser und zwischen 40 und 55 Gew.-% eines Öls, bestehend aus Sulfonaten der allgemeinen Formel R-SO3H, wobei R ein C4-C20-Alkylrest ist, und eines antibakteriellen Bestandteils in einer Menge im Bereich von 0,1 bis 0,2 % bezogen auf das Gewicht der Haut, so dass das System unter Rühren für mindestens drei Stunden reagieren und dann die Trommel aus der darin enthaltenen Lösung entladen werden kann;

    - Waschen der Häute für eine Zeit zwischen 5 und 20 Minuten mit kaltem Wasser in einer Menge zwischen 1,5 und 2,5 mal das Gewicht der Häute, schließlich Entladen der Trommel und Zurückgewinnen der Häute, die zu den Schritten nach dem Gerben geschickt werden.


     
    14. Gegerbte Haut nach dem Verfahren nach einem der Ansprüche 1 bis 13 aufweisend eine Schrumpftemperatur, gemessen nach der in der Norm ISO 3380 definierten Methode, höher als 100 °C bei feuchter blauer Haut und höher als 75 °C bei feuchter weißer Haut.
     


    Revendications

    1. Procédé de tannage de peaux qui inclut les étapes de trempage, chaulage, déchaulage, macération, préparation au tannage et tannage, caractérisé en ce que, dans l'étape de préparation au tannage, les peaux sont traitées avec un mélange liquide constitué de :

    - eau en une quantité comprise entre 40 et 60 % en poids par rapport au poids de la peau ;

    - entre 0,5 et 2,5 % en poids par rapport au poids de la peau d'une émulsion contenant entre 45 et 60 % en poids d'eau et entre 40 et 55 % en poids d'une huile constituée de sulfonates de formule générale R-SO3H, dans laquelle R est un radical alkyle en C4-C20 ;

    - entre 0,2 et 1,5 % en poids par rapport au poids de la peau d'un mélange d'acides dicarboxyliques en C4-C6 contenant entre 10 et 30 % en poids d'acide succinique, entre 40 et 60 % en poids d'acide glutarique et entre 15 et 35 % en poids d'acide adipique ; et

    - un sel sélectionné parmi l'acétate de sodium et le formiate de sodium en une quantité comprise entre 1 et 2 % en poids par rapport au poids de la peau.


     
    2. Procédé selon la revendication 1 dans lequel R est un radical alkyle en C12-C14.
     
    3. Procédé selon l'une quelconque des revendications précédentes dans lequel un composant antibactérien est ajouté au mélange liquide de l'étape de préparation au tannage, en une quantité comprise entre 0,1 et 0,2 % en poids par rapport au poids de la peau.
     
    4. Procédé selon la revendication 3 dans lequel ledit composant antibactérien comprend 25-35 % en poids de sel de sodium de 4-chloro-3-méthylphénol, 8-12 % de 2-phénylphénol, 11-15 % de diéthylène glycol et 12-14 % d'hydroxyde de sodium, avec de l'eau comme complément à 100 %.
     
    5. Procédé selon l'une quelconque des revendications précédentes, dans lequel l'étape de trempage est réalisée avec une première étape de lavage continu à l'eau courante pendant une heure ou de lavage discontinu avec addition de deux aliquotes successives d'eau, chacune en une quantité d'environ deux fois le poids de la peau ; et une seconde étape de traitement dans un tambour avec une quantité d'eau d'environ deux fois le poids de la peau, à une température comprise entre 20 et 45 °C, pendant 16-24 heures, éventuellement avec addition de détergents tensioactifs et/ou de sels qui donnent à la solution un pH basique.
     
    6. Procédé selon la revendication 5 dans lequel lorsque le traitement dans le tambour est réalisé à une température supérieure à 25 °C, un composant antibactérien est ajouté à l'eau, et dans lequel le sel qui donne un pH basique à l'eau est le bicarbonate de sodium.
     
    7. Procédé selon l'une quelconque des revendications précédentes, dans lequel l'étape de chaulage est réalisée à température ambiante, pendant une durée comprise entre 18 et 36 heures, avec un poids d'eau d'environ deux fois celui de la peau à traiter, du Ca(OH)2 en une quantité comprise entre 3 et 5 % par rapport au poids de la peau à traiter, et un composé sélectionné parmi le sulfure de sodium (Na2S) utilisé en une quantité comprise entre 2 et 3 % par rapport au poids de la peau à traiter et de l'hydrosulfure de sodium (NaHS) en une quantité comprise entre 0,5 et 1 % en poids par rapport à la peau à traiter.
     
    8. Procédé selon l'une quelconque des revendications précédentes, dans lequel l'étape de déchaulage est réalisée à une température comprise entre 30 et 38 °C en deux phases successives, chacune réalisée avec une quantité d'eau égale au poids de peau à traiter, en vidangeant l'eau entre une phase et la suivante, et dans lequel la deuxième phase est réalisée à une température plus élevée que la première, en un temps global compris entre 3 et 4 heures, en utilisant, éventuellement subdivisés dans les deux phases :

    - entre 0,8 et 1,5 % par rapport au poids de la peau dans le cas de peaux refendues, et entre 1,5 et 3 % par rapport au poids de la peau dans le cas de peaux non refendues, d'un mélange contenant entre 40 et 45 % de chlorure d'ammonium (NH4Cl), entre 20 et 30 % d'un ou plusieurs acides dicarboxyliques en C4-C6, et entre 0,5 et 1,5 % d'acide sulfamique (H2NSO3H), le complément jusqu'à 100 % étant constitué de sulfate d'ammonium (NH4SO4H) ;

    - entre 0,4 et 1,0 % par rapport au poids de la peau de sulfate d'ammonium ; et

    - entre 0,3 et 1,5 % par rapport au poids de la peau d'un dégraisseur.


     
    9. Procédé selon la revendication 8, dans lequel ledit dégraissant est un mélange liquide constitué de 54-58 % en poids d'éthoxylate d'alcool 2-propyléthylique (CAS 160875-66-1), entre 2 et 3 % de sels de sodium de sulfates d'éthoxylates d'alcool en C12-C14 (CAS 68891-38-3), entre 0,01 et 0,04 % de 1,2-benzylisothiazol-3(2H)-one (CAS 2634-33-5), le complément jusqu'à 100 % étant constitué de sulfate d'ammonium.
     
    10. Procédé selon l'une quelconque des revendications précédentes, dans lequel l'étape de macération est réalisée à une température comprise entre 30 et 37 °C, pendant une durée totale comprise entre 3 et 5 heures, avec une quantité d'eau comprise entre 0,5 et 1 fois le poids de la peau à traiter, à laquelle une quantité comprise entre 0,5 et 1,5 % en poids par rapport au poids de la peau d'enzymes pancréatiques est ajoutée, et dans lequel ladite étape de macération est suivie de deux ou trois lavages, chacun durant entre 10 et 20 minutes, avec une quantité totale d'eau entre 2 et 4 fois le poids de la peau.
     
    11. Procédé selon l'une quelconque des revendications précédentes, dans lequel dans l'étape de macération ou dans les étapes de lavage ultérieures, on ajoute un ou plusieurs composants sélectionnés parmi :

    - jusqu'à 0,5 % en poids d'un dégraissant ;

    - jusqu'à 1,2 % d'un mélange contenant entre 40 et 45 % de chlorure d'ammonium (NH4Cl), entre 20 et 30 % d'un ou plusieurs acides dicarboxyliques en C4-C6, et entre 0,5 et 1,5 % d'acide sulfamique (H2NSO3H), le complément jusqu'à 100 % étant constitué de sulfate d'ammonium (NH4SO4H) ;

    - jusqu'à 0,2 % en poids de sulfate d'ammonium ; et

    - jusqu'à 0,4 % en poids de peroxyde d'hydrogène.


     
    12. Procédé selon l'une quelconque des revendications précédentes, dans lequel l'étape de tannage est réalisée comme un tannage au chrome selon les étapes suivantes :

    - addition dans le bain dérivé de l'étape précédente d'un sel de Cr3+ en une quantité comprise entre 5 et 8 % par rapport au poids de la peau, éventuellement mélangé avec du sulfate de sodium, entre 0,5 et 0,8 % par rapport au poids de la peau d'un mélange d'acides dicarboxyliques en C4-C6 contenant entre 10 et 30 % en poids d'acide succinique, entre 40 et 60 % en poids d'acide glutarique et entre 15 et 35 % en poids d'acide adipique, et entre 0,1 et 0,3 % par rapport au poids de la peau d'un composant antibactérien, en laissant le système réagir sous agitation pendant au moins 8 heures ;

    - addition d'acide formique en une quantité comprise entre 0,3 et 0,5 % par rapport au poids de la peau, en laissant le système réagir sous agitation pendant au moins 2 heures ;

    - addition d'un agent antibactérien en une quantité comprise entre 0,1 et 0,2 % par rapport au poids de la peau et d'un composé basique stabilisateur de chrome en une quantité comprise entre 0,2 et 0,5 % par rapport au poids de la peau, en laissant le système réagir sous agitation pendant au moins 4 heures, puis en déchargeant le tambour de la solution qu'il contient ;

    - un ou plusieurs lavages à l'eau froide dans une quantité totale d'environ une fois et demie le poids de la peau, avec des ajouts éventuels d'acide formique et d'agent antibactérien dans des quantités allant jusqu'à 0,1 % chacun par rapport au poids de la peau, pendant une durée totale d'environ 2 heures et demie, et enfin déchargement du tambour et récupération des peaux qui sont envoyées aux étapes suivant le tannage.


     
    13. Procédé selon l'une quelconque des revendications 1 à 11, dans lequel l'étape de tannage est réalisée comme un tannage aux tanins, selon les étapes suivantes :

    - addition dans le bain dérivé de l'étape précédente d'un sel de phosphonium ou d'un mélange de sels de phosphonium en une quantité comprise entre 2 et 4 % par rapport au poids de la peau et d'un composant antibactérien en une quantité comprise entre 0,3 et 0,5 % par rapport au poids de la peau, en laissant le système réagir sous agitation pendant au moins 3 heures, puis en laissant le système reposer pendant au moins 8 heures ;

    - addition de bicarbonate de sodium (NaHCO3) en deux aliquotes successives, chacune pour une quantité comprise entre 0,25 et 1 % par rapport au poids de la peau, en laissant le système réagir sous agitation pendant au moins une demi-heure ;

    - addition de percarbonate de sodium en une quantité comprise entre 1,0 et 1,5 % par rapport au poids de la peau, en laissant le système réagir sous agitation pendant une heure et demie, puis en déchargeant le tambour de la solution qu'il contient ;

    - addition d'eau à 40 °C en une quantité en poids comprise entre 0,8 et 1,2 fois celle de la peau, de tanins naturels ou synthétiques en une quantité en poids comprise entre 3 et 6 % par rapport au poids de la peau, entre 0,1 et 0,8 % par rapport au poids de la peau d'une émulsion contenant entre 45 et 60 % en poids d'eau et entre 40 et 55 % en poids d'une huile constituée de sulfonates de formule générale R-SO3H dans laquelle R est un radical alkyle en C4-C20, et un composant antibactérien en une quantité allant de 0,1 à 0,2 % par rapport au poids de la peau, en laissant le système réagir sous agitation pendant au moins trois heures, puis en déchargeant le tambour de la solution qu'il contient ;

    - lavage des peaux pendant une durée comprise entre 5 et 20 minutes avec de l'eau froide dans une quantité comprise entre 1,5 et 2,5 fois le poids des peaux, enfin déchargement du tambour et récupération des peaux qui sont envoyées aux étapes suivant le tannage.


     
    14. Peau tannée selon le procédé de l'une quelconque des revendications 1 à 13 ayant une température de rétraction, mesurée selon la méthode définie dans la norme ISO 3380, supérieure à 100 °C dans le cas de peau bleue humide et supérieure à 75 °C dans le cas de peau blanche humide.
     




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    Cited references

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    Patent documents cited in the description




    Non-patent literature cited in the description