EP1556522A1

EP1556522A1 - Method for removing horn substances from animal skin

Info

Publication number: EP1556522A1
Application number: EP03757967A
Authority: EP
Inventors: Hans-Georg Lemaire; Tilman Lüdecke TAEGER; Gunther Pabst; Philippe Lamalle; Michael Breuer; Burkhard Kröger; Thomas Subkowski
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2002-10-21
Filing date: 2003-10-14
Publication date: 2005-07-27
Also published as: US20060037148A1; AR041659A1; US20070143930A1; US7250062B2; AU2003273997A1; WO2004038046A1

Abstract

The invention relates to a method for removing horn substances from animal skin. Said method is characterised in that animal skins are treated in an aqueous bath containing between 0.05 and 5 wt. % - in relation to the weight of the salt - of at least one compound of general formula I or the corresponding alkali metallic salts or alkaline-earth metallic salts thereof or ammonium or phosphonium salts, the variables having the following definitions: R1 is selected from hydrogen or C1-C12 alkyl, unsubstituted or substituted by at least one S-H group or one O-H group; X1 to X4 are the same or different and selected from hydrogen, C1-C4 alkyl, O-H, S-H or N-HR2; and R2 represents hydrogen or C1-C12 alkyl or a C1-C4-alkyl-C=O group, at least one X1 to X4 representing S-H. If R1 contains neither O-H nor S-H, at least one other X1 to X4 is selected from S-H, OH or NH-R2. Said aqueous bath also comprises at least one compound which catalyses the hydrolysis of peptide compounds.

Description

Process for removing home substances from animal skins

description

The present invention relates to a process for removing home substances from animal skins, characterized in that animal skins in aqueous liquor with 0.05 to 5 wt .-%, based on the salt weight, of one or more compounds of the general formula I

or their corresponding alkali or alkaline earth metal salts or ammonium or phosphonium salts, the variables being defined as follows:

R ^{1 is} selected from hydrogen or -CC ₁₂ alkyl, unsubstituted or substituted with one or more SH or OH groups;

X ¹ to X ^{4 are the} same or different and selected from hydrogen, CC alkyl, OH, SH or N-HR ² ,

R ² denotes hydrogen or CC ₂ alkyl or a CC ₄ alkyl C = O group,

where at least one X ¹ to X ⁴ means SH,

and in the event that R ^{1 contains} neither OH nor SH, at least one further X ¹ to X ^{4 is} selected from SH, OH or NH-R ² ,

and further with at least one compound that catalyzes the hydrolysis of peptide bonds.

Animal hides have been processed into leather since ancient times. Before you can start with the actual leather production, tanning, you have to prepare the animal skins. This preparation generally takes place in the so-called water workshop (English: beam house) and comprises numerous work steps. Most of these operations serve to separate those components of the animal skin that are undesirable in later leather production or in later leather skins that are undesirable in later leather production or leather. The undesirable components usually include, for example, the hair together with the hair roots. Depilation of the animal skins is usually promoted by chemicals. A distinction is made between oxidative, reductive and enzymatic hair removal methods. An overview of methods can be found in Herfeld, "Library of Leather", Vol. 2, 1988, pages 62-167 and in E. Heidemann, "Fundamentals of Leather Manufacturing", E. Roether KG Druckerei und Verlag, Darmstadt 1993, page 165-218.

Most of the time the hairs of the animal skins are largely or completely removed in the so-called liming or the Schwöde. Common depilatory reagents that are inexpensive to produce are Na ₂ S and NaSH, the latter often also referred to as sodium sulfohydrate. Both salts can be used in heavily contaminated form, "technical Na ₂ S" generally has a Na ₂ S content not exceeding 65% by weight, and "technical NaHS" usually contains 70-72% by weight NaHS , Both Na ₂ S and NaHS have disadvantages in practical use. For safety reasons, Na ₂ S and NaHS can only be used in a strongly alkaline environment, because during acidification they develop toxic and foul-smelling hydrogen sulfide. The removal of the unused sulfide, especially the sulfide-containing waste water, is a questionable step for ecological and procedural reasons. If excess sulfide precipitates, for example with Fe ²⁺ or Fe ³⁺ , iron sulfide sludges which are difficult to remove are obtained. One can also try to convert them into ecologically harmless salts by oxidation with, for example, H ₂ O ₂ sulfides, but then one has to accept corrosion problems.

There has been no shortage of attempts to use reagents other than Na ₂ S or NaHS for the treatment of animal skins. Most of the experiments are based on volatile organic reagents containing SH groups.

US 1,973,130 describes the use of organic sulfur compounds in the presence of lime (column 1, line 40) for depilation of, for example, calf skins. Ethyl mercaptan in particular is a malodorous reagent, and waste water containing ethyl mercaptan is difficult to process, which prevents the use of ethyl mercaptan in the water workshop.

FR 1,126,252 describes the depilation of animal skins by the action of thioglycolamide (example 1) or thioglycerol (example 2) in the presence of ammonium sulfate at a pH of 7-8.

Attempts to substitute Na ₂ S or NaHS with mercaptoacetic acid or mercaptoethanol or their alkali metal or alkaline earth metal salts did not lead to success. follow, because both reagents and also their alkali or alkaline earth metal salts easily

Split off hydrogen sulfide and smell extremely unpleasant. Even waste water from the

Water workshops containing mercaptoacetic acid or mercaptoethanol or decomposition and secondary products are difficult to clarify and emit unpleasant odors.

The use of formulations containing 1,4-dimercaptobutanediol for removing home substances, in particular hair, from living tissue is known from the cosmetic industry, for example in the case of undesired beard growth. DE 21 31 630, for example, shows that agents consisting of at least 0.25% by weight dimer-captobutanediol and about 0.01 to 40% by weight of a water-soluble guanidine compound and a pH of less than 12 on guinea pigs can be applied to depilate them, or to human cornea to remove calluses without causing skin irritation in guinea pigs or even erythremia (malignant growths in the education system of the red blood cells). The epidermis remains intact in the treatment described in DE 21 31 630.

EP-A 0 095 916 discloses the use of formulations containing aminoethanethiol and 1,4-dimercaptobutanediol and an aminoguanidine or diguanide compound in order to eliminate unwanted human body and facial hair. On page 2, line 1, it is taught that small thiol molecules are preferably suitable for achieving rapid depilation because they penetrate the skin more quickly. The epidermis is retained in the treatment described in EP-A 0 095 916.

EP-A 0 096 521 discloses the use of formulations containing, for example, 1,4-dimercaptobutanediol and an aminoguanidine or diguanidine compound, in order to eliminate unwanted human body and facial hair. The epidermis is retained in the treatment described in EP-A 0 096 521.

It is also known that collagen can be modified by opening S-S bridges in the collagen by reaction with dithioerythrol and subsequent chlorination with chloroacetamide or chloroacetic acid, see. for example E. Heidemann, "Fundamentals of Leather Manufacturing", E. Roether KG Druckerei und Verlag, Darmstadt 1993, page 253. Protein solutions can also be preserved by adding dithioerythrol or dithiothreitol. The preservation is based on a kind of protection against oxidation, because dithioerythrol is usually the first to be oxidized instead of the proteinic SH groups.

From DE 29 17376 C2 it is known that animal skins deal with enzymes in the presence of compounds of the general formula A1 or A2

A1 A2

depilate. R 'are selected from hydrogen, an amino group and alkyl radicals with 1 to 6 carbon atoms, n is a number from 0 to 6, and R "is an alkyl radical with 1 to 6 carbon atoms. The animal skins are first treated in acid pH range with thioglycolic acid (example 1), mercaptoacetic acid (example 2) or mercaptoethanol and thioglycolic acid (example 3) or a combination with thioglycolic acid and thiourea, but the pretreatment agents have a very unpleasant odor.

In WO 96/19560 it is proposed to remove the hair from cattle with two different enzymes and dithiothreitol (example 2, page 14, lines 10 to 12), the hair being retained; however, no instructions for carrying out the proposed method are disclosed.

The task was to provide a method for removing hom substances from animal skins and removing the epidermis as far as possible in the same work step, in which as little unpleasant odors as possible are emitted. In particular, the task was to provide a method for removing home substances in such a way that they are destroyed as far as possible.

It has now been found that the process defined at the outset is excellently suited to removing home substances from animal skins and removing the epidermis as far as possible in the same work step, and that the reagents used emit little or no unpleasant odors.

For the purposes of the present invention, home substances are understood to be calluses, feathers, parts of nails and claws, and in particular hair of animals.

The animal skins may contain remains of meat from the animals in question. It is essential to the invention that they contain hom substances. The amount of horny substance, based on the total weight of the animal skin, is not critical. The method according to the invention is suitable both for removing large amounts of horny substance and for removing small hair residues. For the purposes of the present invention, animal skins are understood not only to mean skins of animals slaughtered or intentionally killed in some other way, but also of those animals which have been caused by accidents, for example traffic accidents or fights with conspecifics or other animals, or by natural causes such as age or Disease have died.

The animal skins within the meaning of the present invention are usually vertebrate animal skins such as e.g. Cattle, calves, pigs, goats, sheep, lambs, moose, game such as deer or deer, and also birds such as ostriches, fish or reptiles such as snakes.

The procedure according to the invention is advantageously carried out as follows.

Animal skins are treated with 0.05 to 5% by weight, based on the salt weight, of one or more compounds of the general formula I.

or the corresponding alkali or alkaline earth metal salts or ammonium or phosphonium salts, the radicals in formula I being defined as follows:

R ¹ selected from

CC ₁₂ alkyl such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, n-pentyl, iso-pentyl, sec.-pentyl, neo-pentyl , 1,2-dimethylpropyl, iso-amyl, n-hexyl, iso-hexyl, sec.-hexyl or n-decyl, particularly preferably CC-alkyl such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, isobutyl, sec-butyl and tert-butyl;

C C ₂ alkyl substituted with one or more hydroxy or thiol groups such as hydroxymethyl, 2-hydroxyethyl, 1,2-dihydroxyethyl, 3-hydroxy-n-propyl, 2-

Hydroxy-isopropyl, w-hydroxy-n-butyl, / -hydroxy-n-decyl, HS-CH ₂ -; HS- (CH ₂ ) ₂ - or HS- (CH ₂ ) ₃ -,

and most preferably hydrogen, X ¹ to X ^{4 are the} same or different and selected from hydrogen,

C _r C alkyl such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl and tert-butyl

OH, SH or N-HR ² , especially OH or SH,

R ^{2 is} hydrogen or

CrC ₁ alkyl such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec.-

Butyl, tert-butyl, n-pentyl, iso-pentyl, sec.-pentyl, neo-pentyl, 1, 2-dimethylpropyl, iso-amyl, n-hexyl, iso-hexyl, sec.-hexyl or n-decyl , particularly preferably -CC alkyl such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl;

or HC = O or a C ₁ -C ₄ alkyl-C = O group, for example acetyl, C ₂ H ₅ -C = O, nC ₃ H ₇ -C = O, iso-C ₃ H ₇ -C = O, nC ₄ H ₉ -C = O, iso-C ₄ H ₉ -C = O, sec- C ₄ H ₉ -C = O, tert-C H ₉ -C = O,

in the presence of at least one compound which catalyzes the hydrolysis of peptide bonds.

At least one X ¹ to X ^{4 means} SH, and in the event that R ^{1 contains} neither OH nor SH, at least one further X ¹ to X ^{4 is} selected from SH, OH or NH-R ² .

At least one is preferred, and at least two groups X ¹ to X ⁴ are particularly preferred hydroxyl groups. X ² and X ^{3 are} each very particularly preferably hydroxyl groups. X ¹ and X ⁴ are very particularly preferably each SH groups, and very particularly preferably R ¹ is hydrogen.

Among the corresponding alkali and alkaline earth metal salts, in particular the mono- and disodium salts, mono- and dipotassium salts and potassium sodium salts of the compounds of the general formula I are also to be mentioned, as are the corresponding calcium and magnesium salts. The ammonium salts or primary, secondary, tertiary and in particular quaternary mono- and diammonium salts and phosphonium salts should also be mentioned. Mixtures of compounds of the general formula I and their corresponding alkali metal or alkaline earth metal salts or ammonium or phosphonium salts can of course also be used. Preferred mono- and diammonium salts have cations of the formula N (R ³ ) (R) (R ⁵ ) (R ⁶ ) ⁺ , where R ³ to R ^{6 are} each the same or different and selected from hydrogen, CrCι ₂ alkyl, Phenyl or CH ₂ -CH ₂ -OH. Examples include tetramethylammonium, tetraethylammonium, methyldiethanolammonium and n-butyldiethanolammonium. Preferred mono- and diphosphonium salts have cations of the formula P (R ³ ) (R ⁴ ) (R ⁵ ) (R ⁶ ) ⁺ , where R ³ to R ^{6 are} as defined above.

It is very particularly preferred to use one or more 1,4-dimercaptobutanediols selected from I a, I a 'and I b,

I a I a 'I b

one or its corresponding alkali or alkaline earth metal salts. I a and I a 'are also referred to as dithiothreitol, I b is also referred to as dithioerythrol. The use of racemic dithiothreitol is very particularly preferred. I a, I a 'and I b are practically odorless, easily metered and readily water-soluble compounds.

The compounds I a or I a 'and I b are known and commercially available, for example, from Aldrich or AGROS Chemicals. The synthesis of other representatives succeeds as in US 4,472,569 or J. Chem. Soc. 1949, 248 or by analogous implementations.

At least one process according to the invention is carried out in the presence of at least one compound which catalyzes the hydrolysis of peptide bonds.

At least one of these compounds is preferably an organic compound.

In the context of the present invention, compounds which catalyze the hydrolysis of peptide bonds are not to be understood as Bronsted acids or their salts.

In the context of the present invention, organic compounds which catalyze the hydrolysis of peptide bonds are to be understood in particular as enzymes. Exo- and endopeptidases are preferred. It can be representative of the Main classes of proteases, for example serine proteases, cysteine proteases, metalloproteases and acid proteases.

You can use an enzyme.

Mixtures of 2 enzymes can be used.

Examples of serine proteases are trypsin, chymotrypsin, elastase, thrombin, plasmin, subtilisin and acrosine.

Examples of cysteine proteases are papain, bromelain and cathepsin B. Examples of metalloproteases are carboxypeptidase and ACE (angiotensin conversion enzyme).

Examples of acidic proteases (aspartate proteases) are pepsin and HIV protease.

Serine proteases such as trypsin, chymotrypsin, subtilisin and proteinase K and variants of the above-mentioned enzymes are particularly suitable in the context of the present invention. Variants include, inter alia, mutants which have arisen as a result of insertion (s), deletion (s) and point mutation (s) and which have modified, in particular advantageous properties, in comparison with the protease which was in each case started. Examples of changed properties are thermostability, higher affinity for the substrate to be converted enzymatically, (higher) substrate specificity and shifting the pH optimum into the desired pH range. Fragments of the aforementioned proteases are also referred to as variants in the sense of the present invention. The variants are produced recombinantly using the customary methods described, for example, in "Molecular Cloning - A Laboratory Manual" by Sambrook, Fritsch and Maniatis (1989) in a suitable bacterial or fungal host system. Proteases of the four main classes (serine, cysteine, metallo- and acid proteases) with specific keratinolytic activity and mixtures of these enzymes are very particularly preferred. In the context of the present invention, enzymes which hydrolyze peptide bonds are also to be understood as commercially available enzyme formulations. Examples of such products are Alcalase 3.0T, Pyrase 250 MP, conc. PTN 3.0 (type p) from Novozymes, Prozym 6 from TFL, pancreatin from Nordmark A, Pancreatina enzyme conc. from Scientific Protein Laboratory, Alprolase 3m, Basozym® L10 and Basozym® S20 from BASF-Aktiengesellschaft, Batinase (manufacturer: Genencor), Proleather (manufacturer: Amano), Protease L 660 (manufacturer: Genencor), Esperase (manufacturer: Novo Nordisk), Alcalase 2.4L (manufacturer: Novo Nordisk), Savinase (manufacturer: Novo Nordisk) and Pruafect 4000 L (manufacturer: Genencor). If the above-mentioned enzymes or variants thereof of these enzymes are used alone or in mixtures in the process according to the invention, not only is a particularly good removal of home substances achieved, but also extensive or, preferably, complete degradation of the epidermis is observed.

In general, an amount of 0.05 to 5% by weight of compound I, based on the skin or salt weight of the animal skins, is sufficient. 0.1 to 1.5% by weight are preferred, and 0.25 to 1.0% by weight are particularly preferred.

The amount of compound that catalyzes the hydrolysis of peptide bonds, and especially enzyme, is usually expressed in Löhlein-Volhard units (LVEs). Usually, one does not dose pure enzyme, but rather diluted formulations, which can be solid or liquid.

The LVEs are determined by titrimetric methods known per se, which are based on the breakdown of casein by an enzyme formulation to be investigated or an enzyme to be investigated and the subsequent titration of the released carboxyl groups with 0.1 N NaOH.

One LVE corresponds to 0.00575 ml 0.1 N NaOH.

According to the invention, 500 to 2,000,000 LVE / kg, preferably 1000 to, are metered

50,000 LVE / kg, particularly preferably 1500 to 10,000 LVE / kg, each based on the

Salt weight of the animal skin to be treated.

Compounds or compounds which catalyze the hydrolysis of peptide bonds are generally used in amounts which are at least a factor of 10, preferably 100, particularly preferably 1000, smaller than the amount of compound I, based on pure compounds.

In particular, if one or more enzymes are used as the compound, it is usually not the pure enzyme that is metered in, but rather one or more solid or liquid formulations containing the compound which catalyzes the hydrolysis of peptide bonds.

In addition to the compound or compounds which catalyze or catalyze the hydrolysis of peptide bonds, solid formulations also contain inorganic or organic solids or mixtures thereof. Examples of inorganic solids are NaCl, Na ₂ SO _4, diatomaceous earth, NaHCO ₃ , Na ₂ CO ₃ or kaolin, concrete, clay minerals; Suitable organic solids are, for example, polysaccharides such as starch and modified starch or urea. Fixed formulations can further reducing substances such as NaHSO ₃ contain. Liquid formulations contain at least one liquid solvent or dispersant, for example water or mixtures of water and organic solvent.

The animal skins are preferably treated in accordance with the invention with one or more compounds of the general formula I and at least one compound which catalyzes the hydrolysis of peptide bonds, in the liming or the Schwöde, either under hair-destroying or under hair-preserving conditions. In this case, it is possible in the liming or painting instead of the usual concentration of about 2 to 4 wt .-% Na ₂ S or NaHS, with a concentration of less than 0.1 wt .-% Na ₂ S or NaHS in the same great effect with regard to the removal of home substances. In a preferred variant of the process according to the invention, it is possible to dispense with the use of Na ₂ S or NaHS or other malodorous sulfur-containing reagents.

The animal skins are treated according to the invention in an aqueous liquor. The liquor ratio is from 1:10 to 10: 1, preferably 1: 2 to 4: 1, particularly preferably up to 3: 1, based on the skin weight or salt weight of the animal skins.

The process according to the invention is carried out at pH values from 6 to 14, preferably from 7 to 12.3, particularly preferably from 7.5 to 10.5 and very particularly preferably from 8.1 to 10.

To adjust the pH value, one can proceed by adding up to 3% by weight of lime (also hydrated lime), based on the liquor. However, the amount of lime can also be reduced to a maximum of 0.3% by weight.

In a preferred embodiment of the process according to the invention, lime is not used. In the preferred embodiment, 0.1 to 4% by weight of one or more inorganic basic alkali metal compounds, for example one or more hydroxides or carbonates of alkali metals, preferably of Sodium or potassium and most preferably sodium. Other suitable inorganic basic alkali metal compounds are alkali metal silicates. Instead of basic alkali metal compounds, magnesium oxide, magnesium hydroxide, amines such as, for example, ammonia, methylamine, dimethylamine, ethylamine or triethylamine or combinations of alkali metal compound and one or more amines can be added.

In addition to water, there may be organic solvents in the liquor, for example up to 20% by volume of ethanol or isopropanol. The method according to the invention can be carried out in vessels in which cremation is usually carried out. The method according to the invention is preferably carried out in rotatable drums with internals. The speed is usually 0.5 to 100 / min, preferably 1.5 to 15 / min and particularly preferably up to 5 / min. If cremation is to take place over a period of more than 8 hours, the speed is usually 0.5 to 10 / min, preferably 1.5 to 5 / min and particularly preferably up to 3 / min for 5 minutes within each hour, ie 5 Minutes and 55 minutes rest per hour.

The pressure and temperature conditions for carrying out the method according to the invention are generally not critical. Carrying out at atmospheric pressure has proven to be suitable; a pressure increased up to 10 bar is also conceivable. Suitable temperatures are 10 to 45 ^C C, preferably 15 to 35 ° C and particularly preferably 25 to 30 ° C.

The compound or compounds of the general formula I can be metered in at the beginning of the liming process, but the animal skins can first be soaked under basic conditions and only after a while one or more compounds of the general formula I and at least one compound which hydrolyses peptide bonds catalyzed, metered. Dosing can be done in one step, i.e. the total amount of the compound or compounds I used is metered in one step; compound I can also be metered in portions or continuously. The same procedure can be followed with at least one compound which catalyzes the hydrolysis of peptide bonds. Compound I and compound which catalyzes the hydrolysis of peptide bonds can be dosed together or separately.

The process according to the invention can be carried out in a period of 5 minutes to 48 hours, preferably 10 minutes to 36 hours and particularly preferably 20 minutes to 15 hours.

In one embodiment of the present invention, organic polyelectrolytes can be added.

Organic polyelectrolytes are generally understood to mean organic polymers with a large number of ionically dissociable groups which can be an integral part of the polymer chains or can be attached to them laterally. In general, each of the statistical repetition units carries at least one group that is ionically dissociable in aqueous solution. In the context of the present invention, so-called ionomers are also counted among the organic polyelectrolytes, which are those organic polymers in which many, but not every repeating unit carries an ionically dissociable group. Polymers with only one or two ionizable groups at the respective chain ends, or in the case of branched polymers a number of dissociable groups corresponding to the number of chain ends, do not count towards polyelectrolytes in the sense of the present invention.

Polybases, polyacids, polyampholytes or their polysalts or mixtures thereof can be used in the process according to the invention. Polyacids are organic polyelectrolytes which dissociate in an aqueous medium with the elimination of protons, for example with polyvinylsulfonic acid, polyvinylsulfuric acid, polyvinylphosphonic acid, polymethacrylic acid or polyacrylic acid as a statistical repeating unit. Polybases are understood to mean those organic polyelectrolytes which contain groups or radicals which can be protonated by reaction with Bronsted acids, for example polyethyleneimines, polyvinylamines or polyvinylpyridines. Polyampholytes are usually understood to mean those polymers which both. contain repeating units which dissociate in an aqueous medium with the elimination of protons, and also repeating units which can be protonated by reaction with Bronsted acids. Polysalts are usually understood to mean single or in particular multiple deprotonated polyacids.

Synthetic polyelectrolytes are preferably used in the process according to the invention.

Of course, you can add tanning agents that are customary in tanning, for example phosphines, such as, for example, B. triphenylphosphine or tris (2-carboxyethyl) phosphine hydrochloride, further hydroxylamine, urea, guanidine or guanidinium hydrochloride, hydrazine, biocides, surfactants and emulsifiers.

The method according to the invention makes it possible to produce excellently hairless pelts. It is found that the epidermis is completely or at least largely detached after a short treatment period. Furthermore, it is found that, in particular in the treatment of animal skins of completely or partially black animals such as, for example, black-colored cattle, a substantial proportion or even all of the melanin is destroyed or removed from the nakedness, so that particularly bright nakedness is obtained. The present invention therefore relates to particularly light pelts produced by the process according to the invention.

It has furthermore been found that the pelts produced according to the invention are extremely suitable for the production of leather. After further processing of the pelts according to the invention, ie pickling, decalcifying, pimples, chrome-free tanning ben or chrome tanning, retanning and dressing, it is observed that the pelts produced according to the invention can be processed further into leather with an improved area yield and less swelling damage, compared with leather which is produced from pelts which are produced with the aid of, for example, Na ₂ S, NaHS, Thi - oglycolic acid or aminethanol have been depilated. In addition, the pelts produced according to the invention can be dyed in a particularly unimportant manner. If the use of lime is dispensed with in the process according to the invention, then bare lumps according to the invention with particularly flat and smooth scars are obtained.

Only slight, preferably no, nubucking is observed.

In a preferred embodiment, the pickling step can be omitted in the further processing.

Another object of the present invention are leather, made from the pelts of the invention. They are characterized by overall advantageous application properties.

Furthermore, it was found that the wastewater produced in the process according to the invention, in particular wastewater from processes according to the invention in which work is carried out without Na ₂ S, NaSH or mercaptans such as aminoethanol or thioglycolic acid, can be worked up particularly well. After the action of one or more compounds of the general formula I and one or more compounds which catalyze the hydrolysis of peptide bonds on the animal skins has ended, the pelts obtained are separated from the liquor, for example by simply removing the pelts or by draining the liquor. The separated liquor is also referred to below as the residual liquor according to the invention or as the residual liquor. The remaining liquor contains, among other things, reacted and possibly unused compound of the general formula I, basic alkali metal compound or basic amines or lime, and in particular residues of the horny materials separated from the nakedness and the epidermis and optionally melanin and / or degradation products of melanin. In a preferred embodiment, the residual liquor according to the invention contains no noticeable proportions from the compound of the general formula I.

The present invention furthermore relates to residual liquors which contain only small amounts of Na ₂ S and preferably neither Na ₂ S nor NaHS and, as organic sulfur compounds, those of the general formula I and their reaction and secondary products from the removal of home substances from animal skins, and see organic sulfur compounds that come from animal skins. The residual liquors according to the invention can now contain melanin and / or breakdown products of melanin as well as melamine and / or breakdown products from melanin. In addition, the salt load is considerably reduced by using the method at pH values below 12.4, in particular at pH values from 7 to 10. This is particularly possible if you have not used lime. The liquors according to the invention are obtainable by the process according to the invention. They are almost odorless and particularly easy to work up compared to the residual tannery liquors known from the prior art.

The remaining liquors contain reaction and secondary products of compounds of the general formula I which result from the removal of home substances from the animal skins, mainly to name hydrolysis and oxidation products of compounds of the general formula I and proteins hydrolysed with the aid of organic compounds.

It has been found that the residual liquors according to the invention can be worked up particularly easily. -

Another object of the present invention is a method for working up residual liquors according to the invention. The refurbishment process according to the invention comprises several steps.

In a first, optional step, the pelts according to the invention are separated from the lime. This step is naturally only necessary if lime has been used in the treatment of the animal skins, otherwise it is not necessary. The separation is carried out by settling, flotation, decanting, filtering or centrifuging, the separation of the lime by decanting, settling or filtering being preferred in the case of large amounts of residual liquors according to the invention. The first step described above makes lime-free residual liquors accessible.

The lime-free residual liquors are then neutralized with acid until a pH of 2 to 8, preferably 3 to 7, particularly preferably 4 to 5 is reached.

Organic or inorganic acids are suitable as acids. Examples include hydrochloric acid, phosphoric acid, CO ₂ , formic acid, sulfuric acid, acetic acid, citric acid, adipic acid and dicarboxylic acid mixtures of adipic acid, glutaric acid and succinic acid. Acidification can be carried out without any special measures relating to the development of hydrogen sulfide.

The proteins removed from the nakedness in the liming or the Schwöde precipitate or float, so that they are mechanically separated in a further step, for example by filtration or flotation. It was also found that after the neutralization and separation of the proteins, residual liquors according to the invention can be used excellently to soften the raw skins. Another object of the present invention is therefore the use of the neutralized and liquor-free residual liquors according to the invention as a medium for the softness of raw skins. The present invention furthermore relates to a process for working up residual liquors according to the invention by neutralization and separation of proteins.

The invention is illustrated by working examples.

General

Determination of LVE

Casein Hammarsten (commercially available from E. Merck, Art. 2242) was used as a 4% by weight solution.

A 4% by weight solution of casein was prepared by diluting 40 g of casein at temperatures up to 60 ° C with 800 ml of distilled water and 32 ml of 1N NaOH, mixing until no precipitation or undissolved solids were present. The solution was cooled to 25 ^° C. and adjusted to a pH of 8.2 with 0.1 N NaOH or 0.1 N HCl. The mixture was then diluted to 1000 ml with distilled water.

50 ml of the casein solution described above were mixed with 10 ml of the formulation of the compound (s) to be investigated which catalyzes the hydrolysis of peptide bonds and the pH was adjusted to 0.1 N NaOH or 0.1 N HCl pH adjusted to 8.2. After 60 minutes at 37 ^° C., the reaction was stopped by adding 20 ml of 0.1N HCl and 20 ml of 10% by weight Na ₂ SO ₄ solution, any precipitates formed were filtered off, and 20 ml were removed, which were treated with 0 , Titrated 1 N NaOH against phenolphthalein.

A blank was made by mixing the above reagents without adding the formulation of the compound (s) to be examined which catalyzes the hydrolysis of peptide bonds. The work was continued as described above. The difference in NaOH consumption multiplied by 17.39 and divided by the enzyme mass used in g corresponds to the LVE / g.

In the following, all data in% by weight relate to the salt weight, unless stated otherwise. General working regulations:

1st switch

Soft using water

The salted skin of a South German cattle was first at 120 ° C. with 150% by weight of water and 0.2% by weight of C ₁₅ H ₃ ι-O- (CH ₂ -CH ₂ -O) ₇ -H for 120 minutes pre-soaked a barrel with slight movement. The liquor was drained (X1-1 "liquor pre-soak", 200% by weight) and then with 100% by weight water, 0.2% by weight C ₁₅ H ₃₁ -O- (CH ₂ -CH ₂ - O) ₇ -H and 0.5% by weight of Na ₂ CO ₃ soaked for 19 hours with occasional agitation. The liquor was then drained off (X1-2 "liquor main switch", 100% by weight).

2. Hair-destroying limber of comparative example V1

For comparative example V1, 100 parts by weight of salt in a rotatable 10 liter barrel with flow-breaking internal fittings were successively charged with 80 parts by weight of water and 1.0% by weight of mercaptoethanol. After 30 minutes, 0.8% by weight NaSH (70% by weight) and 1% by weight hydrated lime followed for a further 30 minutes. This was followed at intervals of 30 minutes by 0.75% by weight sodium sulfide and 0.75% by weight sodium sulfide together with 1.0% by weight lime. The drum was operated at 15 revolutions / minute for a further 30 minutes. A further 70 parts by weight of water and 1.0% by weight of lime were then metered in. After 10 hours at 23 to 27 ° C. and 5 minutes per hour at 3 revolutions / minute, the experiments were ended by draining off the liquor (sample V1-3 "liquor limber", 150% by weight) and the nakedness once for 15 minutes was washed with 150 parts by weight of water (sample V1-4 "wash liquor limber", 150 wt .-%).

Before further processing, the nakedness was fleshed and split (2.8 mm).

2.1. Further processing of the bare fabric according to comparative example V1 in descaling

In the following, the data in% by weight relate to the pelt weight, grain gap, 2.8 mm (corresponds to 75% salt weight), unless stated otherwise. Descaling was carried out at a temperature of 25 to 32 ° C. Test parameters can be found in Table 1. Table 1 Test parameters for further processing of the bare fabric from V1

The penetration of the neutralization over the skin cross-section was checked with phenolphthalein as an indicator. The time required for this was noted.

2.2. Pimples and tanning of the nakedness according to comparative example V1

In the following, the data in% by weight relate to the pelt weight, grain gap, 2.8 mm (corresponds to 75% salt weight), unless stated otherwise.

100% by weight of the respective pelts E1 to E6 according to the invention were mixed with 40% by weight of water and 6% by weight of NaCl (8 ° Be) in a rotatable 10-liter barrel with flow-breaking internals. After 10 minutes, 1.0% by weight of the lipoderm Licker® A1 fatliquor was added, commercially available from BASF Aktiengesellschaft, and after 20 minutes, 0.4% by weight aqueous formic acid (20% by weight) was added. After 30 minutes, 0.8 wt% 98 wt% sulfuric acid was added; the pH was 3.0. After a further 90 minutes, 2.5% by weight of a dispersion of the Relugan® GTP diluted with water in a volume ratio of 1: 3, 3.0% by weight of a dispersion of the syntan tanning agent Basyntan® SW diluted with water in a volume ratio of 1: 2 became liquid (both reagents commercially available from BASF Aktiengesellschaft) and 2.0% by weight of one company) and 2.0% by weight of a naphthalenesulfonic acid-formaldehyde condensation product, prepared in accordance with US Pat. No. 5,186,846, example "Dispersant 1", was added. The mixture was left to act for 90 minutes with occasional rotation and blunted with 0.2% by weight of sodium formate a pH value of 3.9 after a contact time of 15 hours, a further 0.2% by weight of sodium formate and 0.2% by weight of NaHCO _{3 were added,} and the pH was now 4.0 For a further 90 minutes, 0.2% by weight of a dispersion of fungicide Cortymol® Fun diluted with water in a volume ratio of 1: 3 was added.

After the action had ended, the remaining liquor was discharged and the remaining liquor V-0 was obtained.

3. Examples E1 to E7 according to the invention

3.1. Hair-destroying limber of examples E1 to E7 according to the invention

For examples E1 to E5 according to the invention, 100 parts by weight of salt in a rotatable 10-liter barrel with flow-breaking internal fittings were charged with 50 parts by weight of water. The barrel was turned. Then the amount of enzyme shown in Table 2 and after 60 minutes the amount of racemic dithiothreitol ("DTT") shown in Table 2 were added. The pH was 7.5. After the time shown in Table 2, "Base 1 "NaOH solution (50% by weight in water) added. The pH rose to the value given in the table. In Examples E1 to E5, the amount of NaOH solution given in Table 2 (50% by weight in water) was added as "Base 2", the pH increasing to the value given in the table.

The barrel was rotated at 5 rpm for 5 minutes and left motionless for 55 minutes, after which the movement cycle was repeated. After an exposure time of 10 hours, 50% by weight of water was added, the liquor was drained, 150% by weight of water was added, the mixture was agitated for 10 minutes and the washing liquor was discharged again.

Example E6 was carried out analogously, except that NaOH solution was replaced by solid MgO and base was not added.

Example E7 was carried out analogously, but the addition of base was dispensed with. Table 2: Experimental parameters of the liming of the examples according to the invention

ration with 1000 LVE / g.

The pelts B E1 to B E7 according to the invention were obtained.

Before further processing the pelts were fleshed and split (2.8 mm).

3.2. Pimples and tanning of the nakedness of Examples E1 to E7 according to the invention

100% by weight of the respective pelts E1 to E6 according to the invention were mixed with 40% by weight of water and 6% by weight of NaCl (8 ° Be) in a rotatable 10-liter barrel with flow-breaking internals. After 10 minutes, 1.0% by weight of the lipoderm Licker® A1 fatliquor was added, commercially available from BASF Aktiengesellschaft, and after 20 minutes 0.4% by weight became aqueous formic acid and after 20 minutes 0.4 wt% aqueous formic acid (20 wt%) was added. After 30 minutes, 0.8 wt% 98 wt% sulfuric acid was added; the pH was 3.0. After a further 90 minutes, 2.5% by weight of a dispersion of the leather dye Relugan® GTP diluted with water in a volume ratio of 1: 3, 3.0% by weight of a dispersion of the syntan tanning agent Basyntan® SW diluted with water in a volume ratio of 1: 2 liquid (both reagents commercially available from BASF Aktiengesellschaft) and 2.0% by weight of a naphthalenesulfonic acid / formaldehyde condensation product, prepared according to US Pat. No. 5,186,846, example "Dispersant 1" was added. The mixture was left to act for 90 minutes with occasional rotation and was blunted then with 0.2% by weight of sodium formate to a pH of 3.9 After 15 hours of exposure, a further 0.2% by weight of sodium formate and 0.2% by weight of NaHCO ₃ were added The value was now 4.0 After a further 90 minutes, 0.2% by weight of a dispersion of fungicide Cortymol® Fun diluted with water in a volume ratio of 1: 3 was added.

After exposure, let. the remaining liquor was removed and the remaining liquors E1-5 to E6-5 and the leather L E1 to L E6 according to the invention were obtained.

4. Assessment of the pelts according to comparative example B V1 and the inventive examples B E1 to B E7 and the leather according to comparative example L V1 and according to the inventive examples L E1 to L E7

The leather produced according to the invention was distinguished from the leather according to the comparative example by a smoother and flatter scars without visible nubucking.

The epidermis and the hair with the hair root were completely removed or destroyed from the nakedness according to the examples according to the invention. The very bright appearance of the pelts according to the invention was particularly striking and advantageous. The bluish shadows (reaction of sulfide with iron ions) and lime shadows, which are common for lime / sodium sulphate liming, as well as lime shadows, which can lead to uneven coloring, especially in light shades, were completely absent. The properties of the pelts produced according to the invention with regard to swelling were also excellent.

5. Further processing of the leather according to comparative example L V1 and according to examples L E1 to L E7 according to the invention in retanning

The following polymers were used:

Polymer 1: alternating copolymer of (C ₂₀ -C ₂₄ - olefin) maleic anhydride; molar comonomer fraction of (sum of α-olefins): maleic anhydride 1: 1, M _w 8900 g, preparation described in EP 0412389 B1 as dispersion I. Form of use: 30.2% by weight of dispersion.

Polymer 2: 30% by weight aqueous, partially neutralized with NaOH polymer solution; Homopolymer of methacrylic acid, M "approx. 10,000 g / mol; K-value according to Fikentscher: 12, viscosity of the 30% by weight solution: 65 mPa-s (DIN EN ISO 3219, 23 ° C), pH 5.1.

The leathers obtained after 3 were wilted and folded using conventional methods. The fold thickness of the leather was 2.0-2.2 mm (fold weight corresponds to 25% salt weight). The retanning was carried out as follows:

The pretanned leather L V1 or L E1 to L E6 was treated with a liquor length of 100 wt.% Water at 30 ° C. with 15 wt.% Polymer 1 as 30.2 wt.% Aqueous dispersion and 15 wt. % of a 30% by weight aqueous dispersion of polymer 2 (treatment step (a), see Table 4). The commercially available Luganil® Black AS fl. Dye was then added to the leather. Then another 10% by weight of polymer 1 in the form of the 30.2% by weight aqueous dispersion and 2% by weight of polymer 2 as 20% by weight of dispersion were added. The leather remained in the resulting liquor for the time given in Table 4 (exposure step (b)).

The reaction temperature was then increased by adding 100% water at 45 ° C. The pH was adjusted to 3.5 with formic acid. The leather remained in the resulting liquor for the time given in Table 4 (exposure step (c)).

Finally, the leather was dyed with a solution of 1.5% by weight of Luganil® Black AS fl. In 100% by weight of water and 0.7% by weight of formic acid over a period of 45 minutes, then washed as usual, fixed and completed. The finished crust leather C V1 (comparative example) and C E1 to C E6 (according to the invention) were obtained.

The process parameters are shown in Table 3.

Table 3: Process parameters of the action steps in retanning

Then the physical and technical properties were checked.

6. Assessment of the finished leather C V1 and C E1 to C E6

The crust leathers produced from the examples according to the invention differed in their haptic and optical properties by the smoother and finer scars from the comparative example. Leather was obtained with a very good color, good firm grain with very good fullness and excellent softness with an elegant handle. The values are shown in Table 4.

Table 4: Application properties of Crustledem C V1 and C E1 to C E6

The depilation effect and scar strength were assessed visually with grades as in school from 1 (very good) to 6 (unsatisfactory).

7. Refurbishment of the remaining fleets

General working instructions using the example of the remaining fleets according to example E1

The liquor limber E1-3 and wash liquor limber E1-4 were combined and adjusted to a pH of 4.5 with concentrated sulfuric acid (98% by weight). The precipitated protein was separated off with a chamber filter press. The data for the combined and cleaned fleets E1-3 and E1-4 are listed under 8.1 (Fleet E1-A). The cleaned liming liquors were ideal as soft liquors. This can significantly reduce water consumption.

The remaining liquors of the examples according to the invention could be acidified to a pH of 4.5 with sulfuric acid without the development of hydrogen sulfide, and the precipitated proteins could be removed without problems by filtration. The remaining fleets were also almost clear.

The fleet according to comparative experiment V1 could not be acidified without precautionary measures and developed malodorous hydrogen sulfide. Even after processing, it could not be used to soften cattle hides.

8. Analytical results of the residual fleets and waste water

Table 5: analytical results of the residual fleets and waste water

COD: chemical oxygen demand 8.1. Protein precipitate according to E1 - E6:

Approx. 100 - 150 kg each, dry matter 30% by weight, COD [kg O ₂ / kg] 83.3 - 92.8, ash content 1.0 - 1.4%

8.2. Refurbished and reused residual fleets using E1 as an example:

Table 6: Analytical values of the processed residual fleets E1-A

8.3. Use of neutralized and protein-free residual liquors

Soak using neutralized and protein-free residual liquors

The regulation .1 was repeated with a salted skin of a southern German cattle, but water was replaced by the neutralized and protein-free residual liquor described under 7.

The softened skin was then processed further in the same way as E1. A crust leather with the same properties as C E1 was obtained.

Claims

Patent claims

1. A process for removing homing substances from animal skins, characterized in that animal skins are dissolved in an aqueous liquor containing 0.05 to 5% by weight, based on the salt weight, of one or more compounds of the general formula I

R is selected from hydrogen or Cι-Cι ₂ alkyl, unsubstituted or substituted with one or more SH or OH groups;

X ¹ to X ⁴ are the same or different and selected from hydrogen, dC ₄ -alkyl, OH, SH or N-HR ² ,

R ² means hydrogen or CC ₁₂ -AlkyI or a C ₁ -C -alkyl-C=O group,

where at least one X ¹ to X ⁴ means SH,

and in the event that R ¹ contains neither OH nor SH, at least one further X ¹ to X ⁴ is selected from SH, OH or NH-R ² ,

2. The method according to claim 1, characterized in that the treatment of 100 parts by weight of green weight of a southern German cattle with 1% by weight of a proteolytic enzyme preparation with 1000 LVE / g, 0.5% by weight of racemic dithiothreitol and 1.2% by weight. -% NaOH in the form of a 50 wt.% solution, which is added in three portions, in a rotating 10 l drum with flow-breaking internals, with wt.% being excluded in each case

Green weight are related.

3. The method according to claim 1 or 2, characterized in that at least one compound which catalyzes the hydrolysis of peptide bonds is an organic compound.

4. The method according to any one of claims 1 to 3, characterized in that at least one compound which catalyzes the hydrolysis of peptide bonds is an enzyme.

5. Method according to one of claims 1 to 3, characterized in that the enzyme is a protease or a peptidase.

6. The method according to any one of claims 1 to 5, characterized in that the activity according to Löhlein and Volhard of the compounds which catalyze or catalyze the hydrolysis of peptide bonds is in the range from 500 to

2,000,000 LVE/kg salt weight.

7. The method according to any one of claims 1 to 6, characterized in that R ¹ is chosen to be H, X ¹ and X ⁴ to be SH and X ² and X ³ to be OH.

8. The method according to any one of claims 1 to 7, characterized in that the amount of compound which catalyzes the hydrolysis of peptide bonds is chosen to be smaller than the amount of compound I by a factor of at least 10.

9. The method according to any one of claims 1 to 8, characterized in that one works in the presence of urea.

10. Bares, produced by a process according to claims 1 to 9.

11. Residual liquors, obtainable by a process according to one of claims 1 to 10, containing melanin or degradation products of melanin.

12. Process for processing residual liquors according to claim 11, characterized in that they are separated from lime in an optional step, then neutralized with acid and then proteins are separated.

13. Use of neutralized and protein-free residual liquors according to claim 12 for soaking raw hides.