EP1511865A1

EP1511865A1 - Method for removing horn substance from skins, pelts, or furs

Info

Publication number: EP1511865A1
Application number: EP03752667A
Authority: EP
Inventors: Tilman Lüdecke TAEGER; Gunther Pabst; Philippe Lamalle; Stephan Hüffer; Stefan Schroeder
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2002-05-22
Filing date: 2003-05-19
Publication date: 2005-03-09
Anticipated expiration: 2023-05-19
Also published as: KR20050010825A; CN1653195A; EP1511865B1; BR0311165A; WO2003097880A1; CN100381581C; JP2005531650A; DE50311784D1; AR039980A1; PT1511865E; ES2329463T3; AU2003232797A1; US20050229326A1; US7404826B2; ATE438742T1

Abstract

Disclosed is a method for removing horn substance from skins, pelts, or furs of dead animals by treating said skins, pelts, or furs in an aqueous liquor comprising one or several compounds of general formula I or the corresponding alkaline salts, alkaline earth metal salts, ammonium salts, or phosphonium salts thereof, in which the variables are defined as follows: R<1> is selected among hydrogen or C1-C12 alkyl, which is unsubstituted or substituted with one or several S-H group/s or O-H group/s; X<1> to X<4> are identical or different, being selected among hydrogen, C1-C4 alkyl, O-H, S-H, or N-HR<2>; R<2> represents hydrogen, C1-C12 alkyl, or a C1-C4 alkyl C=O group. At least one radical X<1> to X<4> represents S-H if R<1> contains at least one sulfur atom while at least two radicals X<1> to X<4> represent S-H if R<1> contains no sulfur atom.

Description

Process for removing horny substances from hides, furs or furskins

description

The present invention relates to a process for removing horny substances from hides, furs or fur skins of dead animals, characterized in that the hides, furs or fur skins are in an aqueous liquor with one or more compounds of the general formula I.

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

R ^{1 is} selected from hydrogen or -CC -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, C ₁ -C ₄ alkyl, OH, SH or N-HR ² ,

R ^{2 is} hydrogen or Cχ-Cι-alkyl or a Cχ-C-alkyl-C = 0 group,

in the event that R ^{1 contains} at least one sulfur atom, at least one radical X ¹ to X ^{4 is} SH,

and in the event that R ¹ contains no sulfur atom, at least two radicals X ¹ to X ⁴ SH.

Animal hides have been processed into leather for several thousand years. Before you can start with the actual leather production, tanning, you have to prepare the skins. These preparatory steps generally take place in the so-called water workshop (English: beam house) and involve numerous work steps. Most of these operations are used to separate such components of the skins, which in the later Leather production or later leather are undesirable. The unwanted components usually include the hair together with the hair roots and the epider. Depilation of the 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 hair is largely or completely removed in the so-called liming or the Schwöde. Common depilatory reagents that are inexpensive to produce are NaS and NaSH, the latter often also referred to as sodium sulfate hydrate. Both salts can usually be used in heavily contaminated form, "technical Na S" often 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, however, have disadvantages in practical use. For safety reasons, Na S and NaHS can only be used in a strongly alkaline environment because they develop toxic and foul-smelling hydrogen sulfide during acidification. 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, H0 ₂ sulfides, so one has to accept corrosion problems.

There has been no shortage of attempts to use reagents other than Na S or NaHS to treat the skins of dead animals. Most attempts are based on organic reagents containing SH groups.

No. 1,973,130 describes the use of numerous organic sulfur compounds, in particular in the presence of lime (column 1, line 40) for depilation from, for example, calf skins. In particular, ethyl mercaptan is a malodorous reagent, and waste water containing ethyl mercaptan is difficult to process, which is contrary to use in the water workshop. FR 1,126,252 describes the depilation of animal skins by the action of water-soluble thiols, in particular thioglycolamide (example 1) or thioglycerol (example 2) in the presence of ammonium sulfate at a pH of 7-8 on animal skins.

Attempts to substitute Na ₂ S or NaHS with mercaptoacetic acid or mercaptoethanol or their alkali or alkaline earth metal salts did not lead to success, however, because both reagents and their alkali or alkaline earth metal salts easily split off sulfur hydrogen and were extremely unpleasant smell. Waste water from the water workshop, containing mercaptoacetic acid or mercaptoethanol or decomposition and secondary products, is also difficult to clarify and emits unpleasant smells.

The use of formulations containing 1,4-dimer-captobutanediol to remove horny 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 of dimercaptobutanediol and about 0.01 to 40% by weight of a water-soluble guanidine compound and a pH of less than 12 can be applied to guinea pigs Depilate them or on the human cornea to remove calluses without causing skin irritation in guinea pigs or even erythremia (malignant growths in the red blood cell formation system). The epidermis is retained 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 amino guanidine 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 preferred to achieve quick hair removal because they penetrate the skin faster. The epidermis remains intact during the treatment described in EP-A 0 095 916.

EP-A 0 096 521 discloses the use of formulations containing, for example, 1-dimercaptobutanediol and an aminoguanidine or diguanide 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.

Finally, it is known that collagen can be modified by opening SS bridges in the collagen by reaction with dithioerytrol and subsequent chlorination with chloroacetamide or chloroacetic acid, see. for example E. Heidemann, "Funda- mentals of Leather Manufacturing ", E. Roether KG-Druckerei und Verlag, Darmstadt 1993, page 253. You can also preserve protein solutions by adding dithioerythrol or dithiothreitol. The preservation is based on a kind of protection against oxidation, because dithioerythrol is usually used instead of the protein SH -Groups

• is the first to be oxidized.

It has now surprisingly been found that the process defined at the outset is particularly suitable for removing horny substances from the hides, furs and fur of dead animals.

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

The hides and epidermis can still contain remains of meat from the dead animals concerned. It is essential to the invention that they contain horny substances. The amount of horny substance, based on the total weight of the skin or fur or fur, 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, dead animals are understood not only to mean animals slaughtered, hunted in a hunted manner or consciously killed in some other way by humans, but also those animals which are the result of accidents, for example traffic accidents, or fighting with other species or other animals or by natural causes how old age or illness have died.

The hides, furs or fur skins of the animals are usually skins, furs or fur skins of cattle, calves, pigs, goats, sheep, lambs, elk, game such as deer or roe deer, and also birds such as, for example Ostriches, fish or reptiles such as snakes.

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

The skins are treated with one or more compounds of the general formula I.

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

R ¹ selected from

Cχ-Cχ ₂ 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 C ₁ -C ₄ -alkyl such as methyl, ethyl, n-propyl , iso-propyl, n-butyl, iso-butyl, sec-butyl and tert-butyl;

Cχ-Cχ ₂ alkyl, substituted with one or more hydroxy or thiol groups such as hydroxymethyl, 2-hydroxyethyl, 1,2-di-hydroxyethyl, 3-hydroxy-n-propyl, 2-hydroxy-iso-propyl, ω-Hy - droxy-n-butyl, ω-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,

Cχ-C-alkyl such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl and tert-butyl OH, SH or N-HR ¹ , in particular OH or SH,

R ^{2 is} hydrogen or

Cχ-Cχ ₂ 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 Cχ-C ₄ -alkyl such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl and tert-butyl; or HC = 0 or a Cχ-C ₄ alkyl-C = 0 group, for example acetyl, C ₂ H ₅ -C = 0, nC ₃ H ₇ -C = 0, iso-C ₃ H ₇ -C = 0, nC ₄ H ₉ -C = 0, iso-C ₄ H ₉ -C = 0, sec-C ₄ H ₉ -C = 0, tert-C ₄ H ₉ -C = 0.

In the event that R ^{1 contains} at least one sulfur atom, at least one radical X ¹ to X ⁴ denotes an SH group, and in the event that R ¹ contains no sulfur atom, at least two radicals X ¹ to X ⁴ denotes an SH Group.

At least one is preferred, and at least two X ¹ to X ⁴ hydroxyl groups are particularly preferred.

Among the corresponding alkali and alkaline earth metal salts, in particular the mono- and disodium salts, mono- and dipotassium salts as well as 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 as cations those of the formula N (R ³ ) (R ⁴ ) (R ⁵ ) (R ⁶ ) ⁺ , where R ³ to R ^{6 are} each the same or different and selected from hydrogen, Cχ-Cχ -Alkyl, phenyl or CH ₂ -CH-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,

Ia Ia 'I one or its corresponding alkali or alkaline earth metal salts. I a and I a are also called dithiotreitol, I b is also called dithioerythrol. The use of race ischemic dithiothreitol is very particularly preferred. I a, I a ^λ and I b are practically odorless, easily metered and readily water-soluble compounds.

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

In general, an amount of 0.1 to 5% by weight of compound I, based on the skin or salt weight of the hides, furs or fur skins, is sufficient. 0.1 to 2.5% by weight are preferred, 0.1 to 1.5% by weight are particularly preferred.

The treatment of the hides, furs or fur skins according to the invention is preferably carried out with one or more compounds of the general formula I in the liming or the Schwöde, both under hair-destroying and under hair-preserving conditions. It is possible to add a concentration of less than 1% by weight of Na ₂ S or NaHS instead of the usual concentration of about 4% by weight NaS or NaHS in the liming or Schwöde the same great effect with regard to the removal of horny substances.

In a variant of the process according to the invention, one or more compounds of the general formula I are used in the liming together with thiols known from tannery, such as mercaptoethanol or thioglycolic acid. Less than 0.5% by weight of mercaptoethanol or thioglycolic acid is preferably used.

In a very particularly preferred variant of the process according to the invention, however, it is possible to dispense with the use of Na S or NaHS or other malodorous sulfur-containing reagents.

According to the invention, the skins are treated in an aqueous solution

Fleet. 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 skins. The process according to the invention is carried out at pH values from 7 to 14, preferably from 8 to 13 and particularly preferably from 9 to 12.5.

To adjust the pH value, one can proceed by adding up to 3% by weight of lime (also hydrated lime), based on the liquor. But you can also significantly reduce the amount of lime. In a preferred variant of the method according to the invention, lime is not used. In the preferred embodiment, one or more inorganic basic alkali metal compounds are added, for example one or more hydroxides or carbonates of alkali metals, preferably of sodium or potassium and very particularly preferably of sodium. Other suitable inorganic basic alkali metal compounds are alkali metal silicates. You can also add basic amines, for example ammonia, methylamine, dimethylamine, ethylamine or triethyla in, or combinations of alkali metal compounds and one or more basic amines.

In addition to water, other organic solvents can be used in the

Be brisk, for example up to 20 vol .-% ethanol or isopropanol.

The process can be carried out in the usual tannery vessels in which ashing 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 10 / min and particularly preferably up to 4.5 / min.

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, 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 start of the liming process, but the skins can also first be soaked first under basic conditions and only after a while one or more compounds of the general formula I can be metered in. The metering can be carried out in one step, ie the total amount of the compound or compounds I used is metered in one step; but I can also be metered in portions or continuously. The process according to the invention can be carried out in a period of 10 minutes to 48 hours, preferably 1 to 36 hours and particularly preferably 3 to 15 hours.

Of course, you can add tanning agents customary in tanning, for example phosphines, such as, for example, to carry out the process according to the invention. B. triphenylphosphine or tris (2-carboxyethyl) phosphine hydrochloride, further hydroxylamine, urea, guanidine or guanidinium hydrochloride, hydrazine, biocides, enzymes, surfactants and emulsifiers.

The method according to the invention makes it possible to produce excellently hairless bare skin. It is surprising that the epidermis is completely or at least largely detached even after a short treatment period. The present invention therefore relates to nakednesses produced by the method according to the invention.

Furthermore, it has surprisingly been found that the pelts produced according to the invention are extremely suitable for the production of leather. After further processing of the bare leather according to the invention, i.e. Pickling, decalcifying if necessary, pimples, chrome-free tanning or chrome tanning, retanning and (dressing 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 produced with With the help of, for example, Na S, NaHS, thioglycolic acid or aminethanol have been depilated.

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

It has also been found that the wastewater produced in the process according to the invention, in particular wastewater from liming processes in which work is carried out without Na 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 on the skins has ended,

Furs or fur skins of dead animals are separated from the fleece obtained from the fleet, for example by simply removing the fleece or by lowering the fleet. The liquor contains, among other things, unreacted (reacted) compound of the general formula I, from a few ppm up to 4% by weight, in addition basic alkali metal compound or basic amines or lime and in particular residues of the horn material separated from the nakedness. lien and the epidermis. The separated liquor, which contains the unused (reacted) compound of the general formula I, furthermore base and residues of the horn materials separated from the bare and the epidermis, is also referred to below as the residual liquor. The present invention therefore furthermore relates to residual liquors which contain neither Na ₂ S nor NaHS and, as organic sulfur compounds, only contain those of the general formula I, and their reaction and secondary products from the removal of horny substances from skins, furs or fur skins of dead animals, as well as organic sulfur compounds derived from the skins, furs or fur skins of the dead animals. For the purposes of the present invention, residual liquors which contain neither Na ₂ S nor NaSH are to be understood as those residual liquors which contain up to 100 ppm, preferably up to 75 ppm, of sulfide. The sulfide is determined as hydrogen sulfide after acidification with concentrated hydrochloric acid, heating to 90 ° C and stripping. The residual 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.

Hydrolysis and oxidation products of compounds of general formula I are to be mentioned as reaction and secondary products of compounds of general formula I, which result from the removal of horny substances from the hides, furs and fur skins of dead animals.

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

Another object of the present invention is therefore a method for processing residual liquors. The method 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, preference being given to removing the lime by decanting, settling or filtering 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 an acid until a pH of 2 to 8, preferably 3 to 7, particularly preferably 4 to 5 is reached.

5 Toxicologically harmless organic or inorganic acids are suitable as acids. Examples include hydrochloric acid, phosphoric acid, formic acid, sulfuric acid, acetic acid, citric acid, carbonic acid (C0 ₂ ), adipic acid and dicarboxylic acid mixtures of adipic acid, glutaric acid and succinic acid. Acidification 10 can be carried out without 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 15 steps, for example by filtration or flotation.

The invention is illustrated by working examples.

20 working examples

General work regulations

1. Ashes (hair-destroying) 25

The values in% by weight relate in each case to the salt weight, unless stated otherwise.

The skin of a South German cattle was first pre-soaked at 28 ° C with 30,200% by weight of water and 0.2% by weight of an Eusapon® W in a barrel at 1-3 rpm for 120 minutes. The liquor was drained and then soaked for 19 hours with 100% by weight of water, 0.2% by weight of Eusapon® W and 0.5% by weight of soda in automatic mode (5 '/ h). The fleet was then drained. 35

The softened hides of southern German cattle were fleshed green (thickness about 4 mm) and the croupons of the hides were cut into pieces of skin weighing 2.5 kg each.

40 In the following, the values in% by weight refer to the green weight, unless otherwise noted.

1.1. Ashes of Comparative Example VI

45 For Comparative Example VI, 100 parts by weight of green weight in a rotatable 10-1 barrel with flow-breaking internal fittings were successively mixed with 60 parts by weight of water, 0.8% by weight. NaSH and 3% by weight hydrated lime. This was followed by 0.75% by weight sodium sulfide at intervals of 30 minutes. The drum was operated for a further 45 minutes at 15 revolutions / minute. A further 40 parts by weight of water were then metered in. After 10 hours at 23 to 27 ° C. and 5 revolutions / minute, the experiments were ended by draining the liquor and washing the skin twice with 150 parts by weight of water for 15 minutes.

1.2. Hair-destroying limber of Examples 1 to 6 according to the invention

In Examples 1 to 6 according to the invention, 100 parts by weight of green weight were first mixed with 60% by weight of water in a rotatable 10-liter barrel with flow-breaking internal fittings and then, as can be seen from Table 1, products were added.

Table 1

The keg was operated for a further 45 minutes at 5 revolutions / minute. A further 40% by weight of water was then metered in. After 10 hours at 23 to 27 ° C. with periodic operation at 3 revolutions / minute for 5 minutes per hour in each case, the tests were ended by draining off the liquor and the blocks twice for 15 minutes at 150% by weight. Water.

1.3. Assessment of the comparative example and the examples according to the invention and the residual liquors after the liming

The treated according to the inventive examples were pelts hinsieht- treated according to Comparative Example VI ^skins' of the swelling lent only slightly superior, but distinguished by a smoother and flatter grain, in particular the pelts of Examples 1.4 to 1.6 according to the invention. The epidermis and hair with hair roots in the nakedness 1.1 to 1.3 were largely and completely destroyed in the nakedness 1.4 to 1.6.

1.4. Further treatment of the remaining fleets

The remaining liquors of Examples 1.1 to 1.6 according to the invention were acidified to pH 4.5 with formic acid without the development of hydrogen sulfide being observed. The precipitated proteins were then easily separated off by filtration. The remaining fleets of Examples 1.4 to 1.6 were almost clear.

General instructions for the further processing of the pelts from VI and the pelts 1.1 to 1.6 according to the invention

The decalcification or neutralization was carried out with a mixture consisting of two parts by weight of formic acid and three parts by weight of adipic acid. The liquor was brought to pH 7.5-8.5 in two dosing steps. The penetration of the acid mixture over the skin cross-section was determined with phenolphthalein as In indicator checked. The time required for this was noted.

The intermediate stages obtained above were then coiled in a conventional pimple bath at 25 ° C. over a period of 30 minutes with 7% by weight of sodium chloride. 1% by weight of Lipoderm Licker® AI was then added and 4% by weight of formic acid were added after a further 20 minutes. After a further half an hour, a pH of 3 was set using concentrated sulfuric acid.

A 2.5% by weight glutardialdehyde formulation, commercially available as Relugan® GT 24 from BASF Aktiengesellschaft, was added to each of the pimple baths described above. After 90 minutes, 3% by weight of a synthetic tanning agent, commercially available as Basyntan® SW fl. From BASF Aktiengesellschaft, was added. After 30 minutes, 1% by weight of a tanning agent based on naphthalenesulfonic acid, commercially available as Tamol® M from BASF Aktiengesellschaft, was added and left to stand overnight. The mixture was then neutralized with sodium formate and sodium bicarbonate and the liquor was drained off.

The leather thus obtained was washed with water and dried and stretched and folded by conventional methods. The fold thickness of the leather was 2.0-2.2 mm. In the following, the data in% by weight relate to the dried leather, unless stated otherwise.

The "wet white" cowhides obtained in this way were immersed in 100% by weight of water and adjusted to a pH of <3.0 by adding sodium formate and sodium hydrogen carbonate. The leather was drummed at 30 ° C for 60 minutes in a barrel and then washed with 200% by weight of water.

Then 4% by weight of Relugan® GTP were added and drummed for 60 minutes. After addition of 2 wt .-% Tamol® NA, commercially available from BASF Aktiengesellschaft, and 30 wt .-% inütigem fulling 3 of the fatliquoring agent Lipoderm ^etc. licker AI were commercially available from BASF Aktiengesellschaft, and 1 wt .-% - Lipoderm® Liquer LA, commercially available from BASF Aktiengesellschaft, added and drummed for 60 minutes. After the liquor had been drained, 100% by weight of water at 40 ° C. and 2% by weight of commercially available polymeric tanning agent (Relugan® SE), commercially available from BASF Aktiengesellschaft, were added. After partial neutralization of the liquor with sodium hydrogen carbonate to pH 5 and dyeing of the leather in the same liquor with 0.5% by weight of the leather dye Luganil® Light Brown NGB, commercially available from BASF Aktiengesellschaft, it became commercially available with 30% by weight Sulfone tanning agent (Basyntan® SW liquid) and 4% by weight of commercial tare (Granofin® TA, from Clariant Deutschland GmbH) were tanned for 2 hours.

The mixture was then greased with a mixture of 8% by weight of fatliquor (Lipoderm® Licker AI) and 4% by weight of Lipoderm® Licker LA 1. The liquor was then adjusted to a pH of 3.5 to 3.8 using formic acid, the leather briefly rinsed cold and further processed as usual.

Then the physical and technical properties were checked.

Crust leather 2.1 was obtained. until 2.6. with very good coloring and good firm grain with at the same time very good fullness and excellent, light softness with an elegant handle. Crust leathers 2.4 to 2.6 had a smoother and finer grain than V2. Further application properties are shown in Table 2.

Table 2

The hair decomposition and the scar strength were assessed optically and haptically by 2 propands (1: very good, 6: unsatisfactory).

3. liming (hair preserving)

The skin of a South German cattle was first pre-soaked at 28 ° C with 150% by weight water and 0.2% by weight Eusapon® W in a barrel at 1-3 rpm for 120 minutes. The liquor was drained and then with 150 wt .-% water, 0.2 wt .-% Eusapon® W and 0.5 wt .-% Soak soda for 19 hours, stirring occasionally. The fleet was then drained.

The softened hides of southern German cattle were fleshed green 5 (thickness about 4 mm) and the croupons of the hides were cut into 2.5 kg pieces of skin.

In the following, the values in% by weight relate to the green weight, unless otherwise noted.

10

3.1. Hair-conserving limiter of comparative example V3

For comparative example V3, 100 parts by weight of green weight were placed in a rotatable 10-1 drum with

15 installations in succession with 60% by weight of water and after 60 minutes in each case 1.2% by weight of Mollescal MF®, commercially available from BASF Aktiengesellschaft, 0.8% by weight of hydrated lime and 1% by weight of sodium sulfide (60% ) acted upon. The mixture was then filtered over a period of 120 minutes. It followed at a distance of 60 _. ,

20 minutes further 1.6 wt .-% hydrated lime and 40 wt .-% water. After 10 hours at 23 to 27 ° C with periodic operation at 3 revolutions / minute for 5 minutes each hour, the tests were ended by draining off the liquor and the pelts were thrown twice for 15 minutes each at 150% by weight. ^• water were washed.

25

3.2 Hair-holding liming of the examples according to the invention 3.1. until 3.3

30 100 parts by weight of green weight were first mixed with 60% by weight of water in a rotatable 10-1 barrel with flow-breaking internal fittings and then, as can be seen from Table 3, products were added.

35

40

45 Table 3

The drum was operated for a further 45 minutes at 15 revolutions / minute. A further 40 parts by weight of water were then metered in. After 10 hours at 23 to 27 ° C with periodic operation at 3 revolutions / minute for 5 minutes each hour, the experiments were ended by draining off the liquor and washing the pelts twice for 15 minutes with 150% by weight of water ,

3.3. Assessment of comparative example V3 and the examples according to the invention

The pelts treated according to the examples according to the invention were only slightly superior in terms of swelling to the hides treated according to comparative example C3, but were distinguished by a smoother and flatter scars, in particular the pelts of examples 3.2 and 3.3 according to the invention. The epidermis and the hair with hair root in 3.1 was largely and completely destroyed in 3.2 to 3.3.

Then the bare fabric from V3 and 3.1 to 3.3 v / ie were further processed as described under 2.

Then the physical and technical properties were checked.

Crust leather 4.1 was obtained. until 4.2. with very good coloring and good firm grain with at the same time very good fullness and excellent softness with an elegant handle. The crust leathers 4.2 to 4.3 had smoother and finer scars than V4. Further application properties are shown in Table 4.

3.4. Further treatment of the remaining fleets

The remaining liquors of Examples 3.1 and 3.2 according to the invention were acidified to pH 4.5 with formic acid without the development of hydrogen sulfide being observed. The precipitated proteins were then easily removed by filtration. The remaining fleets of Examples 3.2 to 3.3 were almost clear.

Claims

claims

1. A process for removing horny substances from hides, furs or fur skins of dead animals, characterized in that the hides, furs or fur skins in an aqueous liquor with 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:

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

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

R ^{2 is} hydrogen or Cχ-Cχ ₂ alkyl or a Cχ-C ₄ alkyl-C = 0 group,

where R ^{1 contains} at least one sulfur atom, at least one radical X ¹ to X ⁴ SH,

and in the event that R ¹ contains no sulfur atom, at least two radicals X ^x to X ⁴ SH.

2. The method according to claim 1, characterized in that X ^x to X ⁴ each represent OH or SH.

3. The method according to any one of claims 1 to 2, characterized in that R is selected to be hydrogen.

4. Bare animals obtained by a method according to claims 1 to 3.

5. Leather made by tanning pelts according to claim 4.

6. Residual liquors which contain neither Na ₂ S nor NaHS and as organic sulfur compounds only those of the general formula I and their reaction and secondary products which result from the removal of horny substances from hides, furs or fur skins of dead animals, and organic sulfur compounds which from the skins, furs or furskins of the dead animals are obtained by a process according to claims 1 to 3.

7. Process for the processing of residual liquors according to claim 6, characterized in that they are separated from the lime in an optional step, then neutralized with an acid and then mechanically separated off the proteins.