EP0326059B1 - Liming process for obtaining hair - Google Patents

Abstract

The invention relates to a process for liming hides and skins with hair preservation and hair removal, wherein a) the skins and hides are treated for 4-48 hours in a soak comprising an aqueous liquor of pH 7-10.5 and containing at least one surfactant, then b) the soaked skins and hides are treated in an incubation step with an aqueous liquor containing an unhairing agent which is based on reductive organic sulphur compounds and is essentially free of inorganic sulphide and on hydrotropes, for 30 to 180, preferably 45 to 90, minutes, at pH 9-11, and then c) in an immunisation phase the skins and hides are subjected for 1 to 12 hours to the action, with agitation, of the liquor which has been adjusted to pH 10-14 by the addition of bases, and then d) in a hair loosening step the skins and hides are subjected for 30-180 minutes to the action, at pH 10-14, of the liquor to which inorganic sulphide has been added in amounts corresponding to 0.5 to 3% by weight, based on the salt or fresh weight of the skins and hides, and e) hair and hide are separated from one another and f) in a liming step the pelts thus obtained are thoroughly limed in the presence of water, alkali and liming aids in the lime wheel, with the proviso that the liquor at each stage amounts to 50-500% by weight of the hide or skin material used.

Description

OBJECT OF THE INVENTION

The invention relates to a novel hair-preserving liming process of animal hides and skins to obtain the hair, which includes a soft and a subsequent liming process with immunization of the hair by controlled pretreatment with alkali.

STATE OF THE ART

In current leather manufacturing practice, the skins are removed using hydrated lime and inorganic sulfides. (See Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd Ed. Vol. 14, pg. 209, J. Wiley, 1981; Ullmanns Enzyklopadie der Techn. Chemie, 4th ed., Vol. 16, p. 118, publisher Chemistry, 1978). The hair-destroying hair removal processes with sulfides have a negative impact on wastewater and air and are therefore subject to justified criticism. Enzymatic depilation processes, which are tryptic enzymes or fungal or bacterial proteases, partly also carbohydrolases service, have always been suggested. However, the enzymatic depilation methods have only been used in practical applications for small animal skins and also only to a limited extent.

The enzymatic depilation usually does not lead to completely hair-free skins or nakedness. On the other hand, it is sometimes observed that the scars are attacked to a greater or lesser extent by collagenolytically active enzymes, such as those found in many technical enzyme preparations.

eingesetzt werden.Soft processes using hydrotropics and optionally enzymes are known from DE-A 29 44 461 and US-A 4,344,762. An enzymatic process for hair extraction and simultaneous skin disruption using disulfide-bridging substances, including mercaptans and thio-fatty acids, has been described in DE-C 29 17 376 and US Pat. No. 4,294,087. In DE-A 29 29 844 and US-A 4 278 432, an acidic softening process is recommended, in which mercaptans, thiofatty acids or compounds with the structural element are also used

be used.

More recently, efforts have been made to automate depilation processes on the one hand, and to use technology that is as environmentally friendly as possible.

This line is e.g. the "Darmstadt continuous process". (See E. Heidemann in "Das Leder" 35, 143-150 (1984) and the so-called CSIRO-LIME process developed by Cranston, Davis and Scroggie in Australia. (See RW Cranston et al., Leather 186, 229-231 (1984).

TASK AND SOLUTION

It was therefore the task of providing a hair-preserving depilation process in which the hair can be largely preserved and separated, which pollutes the waste water as little as possible and which leads to high-quality leather. It has now been found that the liming process according to the invention fulfills the task to a high degree. The method according to the invention advantageously follows on from the known process steps of the water workshop: the method according to the invention is usually preceded by a dirt diverter.

• a) in einer Weiche bestehend aus einer wäßrigen Flotte vom pH-Wert 7 - 10,5, vorzugsweise 8 - 10, besonders bevorzugt 9 - 10, enthaltend mindestens ein Tensid T während 4 - 48 Stunden behandelt, anschließend
• b) in einem Inkubationsschritt
  die geweichten Felle und Häute mit einer wäßrigen Flotte enthaltend (im wesentlichen) von anorganischem Sulfid freies Enthaarungsmittel EM auf Basis reduzierend wirkender organischer Schwefelverbindungen RED-S während 30 bis 180, vorzugsweise 45 bis 90 Minuten bei einem pH-Wert von 9 - 11, vorzugsweise 9,5 - 10,5 behandelt und anschließend
• c) in einer Immunisierungsphase
  auf die Felle und Häute, die durch Zusatz von Basen B auf einen pH-Wert im Bereich von 10 - 14, vorzugsweise 12 - 14, insbesondere 12,5 + 0,5 gebrachte Flotte während 1 bis 12 Stunden, vorzugsweise 1 bis 3 Stunden unter Bewegen zur Einwirkung gebracht und anschließend
• d) in einem Haarlockerungsschritt
  auf die Felle und Häute die Flotte, der anorganisches Sulfid AS in Mengen entsprechend 0,5 bis 3 Gew.-%, bezogen auf das Salz- bzw. Frischgewicht der Felle und Häute zugesetzt worden war, im pH-Bereich 10 -14, vorzugsweise 12-14, während 30 bis 180 Minuten zur Einwirkung gebracht wird und
• e) Haare und Haut voneinander getrennt werden und
• f) in einem Äscherschritt
  die so erhaltenen Blößen unter Zusatz von Wasser, Alkali und Äscherhilfsmitteln AH durchgeäschert werden, mit der Maßgabe, daß die Flotte jeweils 50 - 500 Gew.-% des eingesetzten Haut- oder Fellmaterials ausmacht.

The process according to the invention for the liming of hides and skins while maintaining and obtaining hair in a soft and subsequent liming process with immunization of the hair by controlled pretreatment with alkali consists in that the skins and skins

• a) treated in a switch consisting of an aqueous liquor with a pH of 7-10.5, preferably 8-10, particularly preferably 9-10, containing at least one surfactant T for 4-48 hours, then
• b) in an incubation step
  the softened skins and skins with an aqueous liquor containing (essentially) hair removal agent EM free of inorganic sulfide based on reducing organic sulfur compounds RED-S for 30 to 180, preferably 45 to 90 minutes at a pH of 9-11, preferably 9.5 - 10.5 treated and then
• c) in an immunization phase
  on the skins and skins, which by adding base B to a pH in the range of 10-14, preferably 12-14, in particular 12.5 + 0.5, brought liquor for 1 to 12 hours, preferably 1 to 3 hours brought under influence and then
• d) in a hair loosening step
  on the skins and skins, the liquor, the inorganic sulfide AS had been added in amounts corresponding to 0.5 to 3% by weight, based on the salt or fresh weight of the skins and skins, in the pH range 10-14, preferably 12-14 for 30 to 180 minutes and
• e) hair and skin are separated and
• f) in a liming step
  the pelts obtained in this way are cremated with the addition of water, alkali and liming aids AH, with the proviso that the liquor each makes up 50-500% by weight of the skin or fur material used.

• Zur Weiche a)
  Die Einstellung des pH-Werts der wäßrigen Weichflotte geschieht in an sich bekannter Weise durch Verwendung von Alkali, insbesondere Natrium- oder weniger bevorzugt Kaliumhydroxid, -carbonat bzw. -bicarbonat, gegebenenfalls auch durch Ammoniumverbindungen wie Ammoniak bzw. durch Kombination von Alkalien.
  Die Flottenlänge beträgt - in Anpassung an die verwendeten Gefäße - in der Regel 100 - 500, vorzugsweise 100 - 500 Gew.-%, bezogen auf die gesalzenen Häute bzw. Felle. In Abwesenheit geeigneter Enzyme als Weichhilfsmittel ist mit verlängerter Weichdauer zu rechnen; praktisch gesehen führt man die Weiche zweckmäßig über Nacht durch, vorzugsweise im Temperaturbereich 25 - 28 Grad C. Bei einer bevorzugten Ausführungsart kann der Weichvorgang in einer Flotte durchgeführt werden, die für den Weichvorgang geeignete Enzyme enthält. Vorzugsweise handelt es sich dabei um proteolytische Enzyme [E.C.3.4.]. Besonders bevorzugt ist die Verwendung alkalischer Proteasen, mit einem Wirkungsoptimum, etwa im Bereich von pH 7,5 - 13. (Vgl. Kirk-Othmer, 3rd. Ed. loc.cit. Vol. 9, K. Aunstrup in B. Spencer Ed. "Industrial Aspects of Biochemistry", Vol. 30, (I), pp. 23-46; North Holland, 1974).
  Im allgemeinen kommen in Frage:
  • Proteasen tierischen Ursprungs, wie die pankreatischen Enzyme (Pancreatin, E.C. 3.4.23).
  • Proteasen mikrobiellen Ursprungs (vgl. L. Keay in "Process Biochemistry" 1971, pp. 17-21).
  • α) aus Bacillus-Arten
    wie B.subtilis, B.licheniformis, B.alkalophilus, B.cereus, B.natto, B.vulgatus, B.mycoides,
  • β) aus Streptococcus-Arten
  • γ) aus Streptomyces-Arten
    wie Streptomyces fradiae, S.griseus, S.rectus
  • δ) aus Aspergillus-Arten
    wie Aspergillus flavus-oryzae, A.niger, A. saitoi, A.usamii
  • ε) aus Mucor- und Rhizopus-Arten
    wie Mucor pusillus, M.mietrei
  • ζ) Endothia-Arten
    wie Endothia parasitica
  • η) aus Trametes-Arten
    wie Trametes sanguinea
  Mit Vorteil wird eine Kombination von Enzymen angewendet, wobei ein Anteil an Bakterienprotease zweckmäßig ist. Vorteilhaft liegt der Anteil der Bakterienprotease, z.B. vom Typ*) bei 20 - 70 % der enzymatischen Gesamtaktivität. Als weitere Enzymkomponenten sind z.B. Pilzproteasen, z.B. vom Typ δ**), etwa in Anteilen von 10 - 30 % und/oder Pankreasenzyme in Anteilen von 10 - 20 % der Gesamtaktivität gut geeignet.
  Als Anhalt soll die Dosierung der proteolytischen Enzyme so erfolgen, daß Quantitäten in der Weiche vorliegen, die 2 000 bis 20 000 Löhlein-Volhard-Einheiten pro kg Salz- oder Frischgewicht der Häute und Felle entsprechen.
  Die proteolytische Wirksamkeit von Enzymen wird gebräuchlicherweise nach der Anson-Haemoglobin-Methode (M.L. Anson,, J.Gen. Physiol. 22, 79 (1939) bzw. nach der Löhlein-Volhard-Methode (die Löhlein-Volhard'sche-Methode zur Bestimmung der proteolytischen Aktivität. Gerbereichem. Taschenbuch, Dresden-Leipzig, 1955) als "LVE" (Löhlein-Volhard-Einheit) bestimmt.
  Unter einer Löhlein-Volhard-Einheit ist diejenige Enzymmenge zu verstehen, die unter den spezifischen Bedingungen der Methode 1,725 mg Casein verdaut. Weiter werden im folgenden für die Aktivitätsbestimmung der im sauren Bereich wirksamen Enzyme Einheiten verwendet, die aus der Anson-Methode abgeleitet sind. Diese werden als "Proteinase-Units (Haemoglobin)" U_Hb bezeichnet. Eine U_Hb entspricht der Enzymmenge, welche die Freisetzung von trichloressigsäure-löslichen Bruchstücken aus Haemoglobin äquivalent 1 uMol Tyrosin pro Minute bei 37 Grad C (gemessen bei 280 nm) katalysiert. (1 mU_Hb = 10⁻³ U_Hb.)
  Die Weiche wird in Gegenwart mindestens eines Tensids T durchgeführt. Als Tenside T werden vorzugsweise anionische und insbesondere neutrale Tenside, wie sie z.B. in der DE-A 33 12 840 bzw. der AU-C 558 447 beschrieben werden, bzw. Mischungen beider eingesetzt. (Vgl. F. Stather, Gerbereichemie und Gerbereitechnologie, Akademie-Verlag, Berlin, 1967). In der Regel werden 0,1 bis 1, vorzugsweise 0,1 bis 0,3 Gew.-% der Tenside T bezogen auf das Salzgewicht der Häute und Felle angewendet. Besonders bevorzugt ist die gleichzeitige Anwendung neutraler und anionischer Tenside, wobei sich - als Anhalt - ein Verhältnis 3 : 1 bis 10 : 1 Gew.-Teile als zweckmäßig erwiesen hat.
  Genannt seien Tenside beispielsweise der folgenden Typen:
  • A. Polyglykolderivate (in Klammer beispielhafte Handelsprodukte)
    • α) Fettsäurepolyglykolen (EMULPHOR®)
    • β) Fettalkoholpolyglykolether (FORYL D®)
    • γ) Alkylphenolpolyglykolether (EUMULGIN®) 286, (FLUIDOL W100®, IGEPAL C®
    • δ) Fettsäureethanolamidpolyglykolether (C®, FORYL KW®) EUMULGIN
  • B. Glycerinderivate
    • α) Fettsäuremonoglyceride (TEGOMOL S®)
    • β) Fettsäurepolyglycerinester
    Weiter anionische Emulgatoren beispielsweise der folgenden Typen:
  • C. Sulfate R′-OSO₃Na
    • α) Fettalkoholsulfate, primäre EPPOL DL conc.®, PERAMIT ML® und sekundäre TEEPOL®
    • β) Fettalkohol-ethoxyliert-Sulfate (TEXAPON Q®)
    • γ) Monoglyceridsulfate (VEL®)
    • δ) Sulfatierungsprodukte von ungesättigten Ölen und Fettsäuren (LEDEROLINOR DKMS®)
  • D. Sulfonate R SO₃Na
    • α) Alkylbenzolsulfonate (ABS, TPS) (MARLOPON®, MARLON®)
    • β) Alkylsulfonat (MERSOLAT®)
    • γ) Fettsäurekondensationsprodukte (IGEPON A®, IGEPON I®)
    • δ) Petrolsulfonate (enthalten in: GRASSAN B®)
    • ε) Sulfitierungsprodukte von ungesättigten fetten Ölen und Fettsäuren (CUTISAN BS®)
    • ζ) kurzkettige Alkylbenzolsulfonate, z.B. des Cumols, Toluols oder Xylenols,
     wobei der Rest R′ (falls nicht anders ausgewiesen) einen langkettigen Alkylrest, vorzugsweise mit 8 - 28 Kohlenstoffatomen bedeutet.
  Die Weiche kann - innerhalb des erfindungsgemäßen Verfahrens - beispielsweise so durchgeführt werden, daß man das gesalzene Hautmaterial in das Weichwasser einlegt, dem eine oder mehrere Tenside T, vorzugsweise in den angegebenen Konzentrationen, zugefügt sind oder im Verlauf des Weichverfahrens zugefügt werden. Das Weichverfahren kann in den für solche Verfahren üblichen Geräten, beispielsweise im Mischer, Faß, Gerbmaschine oder Haspel, durchgeführt werden.
• b) Der Inkubationsschritt
  wird vorzugsweise mit einer frischen, wäßrigen Flotte durchgeführt, unter anderem um die Konstanz der Reaktionsbedingungen sicherzustellen. Die Flotte, in der die geweichten Häute oder Felle inkubiert werden, ist im wesentlichen frei von
  anorganischem Sulfid. Vorzugsweise macht die Flotte 50 - 80 Gew.-% bezogen auf die gesalzenen bzw. frischen Häute oder Felle aus.
  Die Flotte enthält ein Enthaarungsmittel EM mit den folgenden Komponenten:
  • mindestens eine, im vorliegenden System reduzierend wirkende, organische Schwefelverbindung RED-S in Mengen von 0,05 bis 5 Gew.-% bezogen auf das Salzgewicht bzw. das Frischgewicht der Häute und Felle,
  • mindestens ein Hydrotropikum HY in Mengen von 0,05 bis 2 Gew.-% auf das Salzgewicht bzw. das Frischgewicht der Häute und Felle,
  • ein oder mehrere Amine A in Mengen von 0 bis 2 Gew.-%, vorzugsweise 0,05 bis 2 Gew.-% bezogen auf das Salzgewicht bzw. das Frischgewicht der Häute und Felle,
  die im Sinne der gestellten Aufgabe synergistisch zusammenwirken.
  Der pH-Wert der Flotte beim Inkubationsschritt liegt bei 9 -11, vorzugsweise bei 9,5 - 10,5; dieser pH-Wert kommt teils durch das Amin A, teils durch eingesetztes Alkali, beispielsweise in Form von Alkalimercaptiden zustande.
  Die Wirksamkeit der reduzierend wirkenden, organischen Schwefelverbindungen RED-S kann dahingehend gedeutet werden, daß sie bei pH 10 - 12,5 imstande sind die Disulfidbrücken des Präkeratins zu spalten, jedoch jene des äußeren Haarkeratins weitgehend intakt zu lassen. In anderen Worten, das (pH-abhängige) Redoxpotential der organischen Schwefelverbindung RED-S kann im System EM höher sein als das des Keratins (E₀ = -420 mV). Ohne sich notwendig auf diese Modellvorstellung festzulegen, erlaubt diese doch die Auswahl geeigneter organischer Schwefelverbindungen.
  Vorzugsweise kommen als reduzierend wirkende, organische Schwefelverbindungen RED-S solche der Formel I
  
  
  
          R₁ SH   I
  
  
  
     worin R₁ für einen gegebenenfalls verzweigten, gegebenenfalls cyclischen Alkylrest mit 2 bis 24 Kohlenstoffatomen, insbesondere 2 bis 18 Kohlenstoffatomen, speziell 2 bis 12 Kohlenstoffatomen, wobei der Alkylrest hydroxy- oder thiol-substituiert sein kann, oder für einen Rest -(CH₂)p-NR₂ R₃
     worin R₂ und R₃ unabhängig voneinander für Wasserstoff oder einen Alkylrest mit 1 bis 6 Kohlenstoffatomen steht, oder unter Einbeziehung eines weiteren Stickstoff-, eines Sauerstoff- oder eines Schwefelatoms einen (vorzugsweise gesättigten) Heterocyclus bilden und p für eine ganze Zahl von 2 bis 6 steht oder für einen Rest -R₄-COOR₅, worin
     R₄ für einen, gegebenenfalls verzweigten, gegebenenfalls mit einer weiteren COOR₅-Gruppe substituierten Alkylrest mit 2 bis 6 Kohlenstoffatomen, wobei -SH an einem primären, sekundären oder tertiären Kohlenstoffatom gebunden sein kann und worin R₅ für Wasserstoff oder einen Alkylrest mit 1 bis 6 Kohlenstoffatomen steht
  oder die Formamidinsulfonsäure in Frage.
  Besonders genannt seien als Verbindungen der Formel I Mercaptane, speziell n-Alkylmercaptane, wie n-Butylmercaptan, n-Amylmercaptan, n-Dodecylmercaptan, Mercaptane aus LOROL®-Typen, n-Tetradecylmercaptan sowie hydroxy substituierte Alkylmercaptane wie 2-Mercaptoethanol, 3-Mercapto-1,2-propandiol, weiter Amin-substituierte Alkylmercaptane wie das β-(Di-n-amylamino)ethylmercaptan, wobei diese Verbindungen dem pH-Wert gemäß vorwiegend in Form ihrer Salze vorliegen werden. Desweiteren seien genannt die Mercapto-mono- und die -Dicarbonsäuren bzw. deren Salze wie die Mercaptoessigsäure, die 2-Mercaptopropionsäure, die 3-Mercaptopropionsäure, die Mercaptobernsteinsäure. Ferner sei genannt die Formamidinsulfinsäure (Thioharnstoffdioxid).
  Geeignete Hydrotropika HY sind z.B. in der Literaturstelle H. Rath et al. Melliands Textilbericht 43 (7) 718 (1962) bezeichnet worden.
  Vorzugsweise finden Hydrotropica der Formel II
  
  worin R für Wasserstoff, -NH₂, -CH₃ oder -NH-CN und X fur Sauerstoff, Schwefel oder NH steht oder X zusammen mit R ein heterocyclisches System bildet mit der Maßgabe, daß das heterocyclische System nur Stickstoff-Heteroatome aufweist und/oder die davon abgeleiteten Säureadditionssalze z.B. Hydrochloride, Sulfate, Phosphate sowie Rhodanide, Anwendung.
  Genannt seien insbesondere Harnstoff, Thioharnstoff, Acetamid, Formamid, Guanidin, Melamin, Dicyandiamid. Apparativ kann wie bei der Weiche verfahren werden. Auch hier beträgt die Verfahrenstemperatur vorzugsweise 25 - 28 Grad C.
  Als weitere Komponente des Enthaarungsmittels EM kann gegebenenfalls ein geeignetes Amin A anwesend sein. Zweckmäßig handelt es sich dabei um ein toxikologisch bzw. ökologisch unbedenkliches Amin, beispielsweise ein nicht stark flüchtiges.
  Vorzugsweise werden die Amine A durch die Formel III
  
  
  
          R₆NR₇R₈   III
  
  
  
  worin R₆ für einen gegebenenfalls mit einer OH-Gruppe substituierten, gegebenenfalls cyclischen Alkylrest mit 1 bis 8 Kohlenstoffatomen und R₇ und R₈ für Wasserstoff stehen oder die gleichen Bedeutungen wie R₁ besitzen oder worin R₂ und R₃ zusammen mit dem Stickstoff und gegebenenfalls einem weiteren Stickstoff- oder Sauerstoffatomen einen 5- oder 6-gliedrigen Heterocyclus bilden mit der Maßgabe, daß beim Vorliegen eines Heterocyclus R₆ auch für Wasserstoff stehen kann.
  Definitionsgemäß kann es sich bei der Aminkomponente A um ein primäres, sekundäres oder tertiäres Amin handeln, bzw. auch um Mischungen mehrerer Amine. Günstig ist beispielsweise die Anwendung hydroxyl-substituierter Alkylamine wie z.B. des Ethanolamins, des Diethanolamins und des Triethanolamins.
  Weiter seien das Dimethylamin, das Diethylamin, das Cyclohexylamin und das Piperidin genannt. c) Die Immunisierungsphase
  ist gleichbedeutend mit der Alkali-Aktivierung des Systems EM (während der Inkubationsschritt technisch gesehen ein Vorlaufen des Reduktionsmittels bei niedrigerem pH bedeutet). Sie ist gekennzeichnet durch den Zusatz bzw. die Anwesenheit von Basen B zu der Flotte, wodurch ein pH-Wert von 10 - 14, vorzugsweise 12 - 14, eingestellt wird. Im allgemeinen liegt der pH-Wert der Immunisierungsphase somit oberhalb des pH-Werts des Inkubationsschritts, beispielsweise um mindestens 0,5 - 1 pH-Einheiten. Es liegt die mechanistische Deutung nahe, daß in der Immunisierungsphase beim Keratin eine Umwandlung des Cysteins in Lanthionin eintritt.
  In diesem Zusammenhang muß die durch die pH-Erhöhung herbeigeführte Erhöhung des Redoxpotentials des Systems EM mit der reduzierend wirkenden, organischen Schwefelverbindung RED-S gesehen werden.
  Die Dauer der Immunisierungsphase beträgt in der Regel ca. 1 bis 5 Stunden, insbesondere 1 - 3 Stunden, vorzugsweise näher bei 1 Stunde. Als zweckmäßig hat sich das Arbeiten im Gerbfaß bzw. der Haspel erwiesen, wobei - vorzugsweise diskontinuierliches - Bewegen Vorteile mit sich bringt. Als Faustregel kann gelten, daß die Hälfte der Zeit bewegt wird, in etwa 10 minütigem Rhythmus. Vorzugsweise wird bei 25 - 28 Grad C gearbeitet. Prinzipiell können als Basen B vorwiegend anorganische Basen wie sie z.B. im Äscher Verwendung finden, angewendet werden, wie z.B. Alkalien. Besonders bewährt hat sich aber die Verwendung von Calciumoxid in der beim Äscher üblichen Hydratform (Äscherkalk bzw. Kalkhydrat: Vgl. F. Stather, Gerbereichemie und Gerbereitechnologie, Akademie-Verlag, Berlin, 1967, S. 169. Der Zusatz von Kalkhydrat zur Flotte liegt gewöhnlich bei 0,5 - 5 Gew.% bezogen auf das Gewicht der Felle bzw. Häute. Allerdings können der Inkubationsschritt und die Immunisierungsphase auch ineinander übergehen, in dem z.B. die Bestandteile des Enthaarungsmittels EM gleichzeitig mit der Base B, speziell mit dem Kalkyhydrat angewendet werden.
  d) Der Haarlockerungsschritt
  bedient sich anorganischen Sulfids als wirksames Agens, also der Sulfid- bzw. Hydrogensulfidanionen. Zweckmäßigerweise werden diese in Form von NaHS bzw. Na₂S zugesetzt, wobei im ersten Fall ca. 0,7 bis 1,2 Gew.-% Natriumhydrogensulfid (gewöhnlich 72 %ig), im letzteren Fall 1 - 2 Gew.-% bezogen auf das Gewicht der Felle bzw. Häute eingesetzt werden. Der pH-Wert soll im Bereich 10 - 14, vorzugsweise 12 - 14, sein. Die Einwirkungsdauer liegt bei 20 - 30 Minuten im Minimum und bis zu 1 bis 3 Stunden. Die Temperatur liegt auch hier vorteilhaft bei 25 bis 28 Grad C. Es kann vermutet werden, daß für die Haarlockerung das unter den angewandten Bedingungen beträchtlich hohe Redoxpotential der sulfidhaltigen Lösung (E_o = -500 bis -550 mV) verantwortlich ist, welches zur mehr oder weniger vollständigen Reduktion des Präkeratins ausreicht, ohne das immunisierte äußere Haarkeratin zu zerstören.
• e) Die Haarabtrennung
  Durch die Behandlung kommt es zur Trennung von Haar und Haut. Durch Umpumpen der Enthaarungsflotte über ein extern angebrachtes Sieb kann das Haar vollständig entfernt und anschließend gewaschen und entwässert werden. Es kann aber auch das Haar in der Flotte belassen und anschließend der Äscher bzw. Hautaufschluß durchgeführt werden. Die Haarabtrennung erfolgt dann nachträglich im Sinne einer mechanischen Vorklärung.
• f) Der Äscherschritt
  Zur Entfernung des Grundhaars sowie zur Vervollständigung des Hautaufschlusses dient der Äscherschritt. Nach den vorausgegangenen Operationen sind die Blößen nicht vollständig, als Anhaltspunkt zu 1/3 bis allenfalls 1/2 der Blößenstärken durchgeäschert. Die vollständige Äscherung der Häute geschieht im allgemeinen unter Aufbesserung von Wasser, Alkali und Äscherhilfsmitteln AH. Im einzelnen bestehen verschiedene Möglichkeiten der Durchführung des Äschers. So können nochmals Äscherhilfsmittel AH und Kalk, vorzugsweise in Mengen von 1 - 4 Gew.-% bezogen auf die Häute und anorganische Sulfide in Mengen von 0,3 - 0,6 Gew.-% bezogen auf die Häute der Flotte zugesetzt werden. Die Äscherdauer liegt im allgemeinen bei 20 - 24 Stunden (Verfahrensvariante 5A).
  Man erhält Blößen von wünschenswerter Glätte, und Grundreinheit und beobachtet wenig Zug. Insgesamt läßt sich auch ein Maßgewinn erzielen.
  Bei einer anderen Variante wird, ausgehend von einer (durchschnittlich zu 1/3 durchgeäscherten) Haut, wie folgt verfahren:
  Man läßt zunächst die Flotte ab, entnimmt die Häute und wäscht sie vorzugsweise unter Verwendung von unter gerberischen Gesichtspunkten vertretbaren Säuren, wie z.B. organische Säuren wie z.B. Essigsäure oder Phosphonsäuren (vgl. DE-A 35 33 203) oder sauren Polyphosphaten, um die Schlüpfrigkeit der Häute herabzusetzen und die Handhabung zu verbessern. Anschließend wird in an sich bekannter Weise entfleischt und gespalten. (Vgl. F. Stather, Gerbereichemie und Gerbereitechnologie, Akademie-Verlag, Berlin, 1967).

* bacillus subtilis
** aspergillus parasiticusIn detail, the method can be carried out as follows.

• Turnout a)
  The pH of the aqueous soft liquor is adjusted in a manner known per se by using alkali, in particular sodium or less preferably potassium hydroxide, carbonate or bicarbonate, optionally also by means of ammonium compounds such as ammonia or by a combination of alkalis.
  The liquor length is - in adaptation to the vessels used - generally 100-500, preferably 100-500% by weight, based on the salted hides or skins. In the absence of suitable enzymes as softening agents, an extended softening time is to be expected; In practical terms, the switch is expediently carried out overnight, preferably in the temperature range 25-28 ° C. In a preferred embodiment, the softening process can be carried out in a liquor which contains enzymes suitable for the softening process. These are preferably proteolytic enzymes [EC3.4.]. The use of alkaline is particularly preferred Proteases with an optimum activity, approximately in the range of pH 7.5-13. (See Kirk-Othmer, 3rd. Ed. Loc.cit. Vol. 9, K. Aunstrup in B. Spencer Ed. "Industrial Aspects of Biochemistry ", Vol. 30, (I), pp. 23-46; North Holland, 1974).
  In general, the following are possible:
  • Proteases of animal origin, such as the pancreatic enzymes (pancreatin, EC 3.4.23).
  • Proteases of microbial origin (see L. Keay in "Process Biochemistry" 1971, pp. 17-21).
  • α) from Bacillus species
    such as B.subtilis, B.licheniformis, B.alkalophilus, B.cereus, B.natto, B.vulgatus, B.mycoides,
  • β) from Streptococcus species
  • γ) from Streptomyces species
    such as Streptomyces fradiae, S.griseus, S.rectus
  • δ) from Aspergillus species
    such as Aspergillus flavus-oryzae, A.niger, A. saitoi, A.usamii
  • ε) from Mucor and Rhizopus species
    such as Mucor pusillus, M.mietrei
  • ζ) Endothia species
    like Endothia parasitica
  • η) from Trametes species
    like Trametes sanguinea
  A combination of enzymes is advantageously used, a proportion of bacterial protease being appropriate. The proportion of bacterial protease, for example of the type *) is advantageously 20-70% of the total enzymatic activity. Fungus proteases, for example of the type δ **), for example in proportions of 10-30% and / or pancreatic enzymes in proportions of 10-20% of the total activity, are well suited as further enzyme components.
  As a guide, the dosage of the proteolytic enzymes should be such that quantities are present in the switch which correspond to 2,000 to 20,000 Löhlein-Volhard units per kg of salt or fresh weight of the hides and skins.
  The proteolytic activity of enzymes is customarily determined according to the Anson-Hemoglobin method (ML Anson, J.Gen. Physiol. 22, 79 (1939) or according to the Löhlein-Volhard method (the Löhlein-Volhard'sche method Determination of proteolytic activity, Gerbereichem paperback, Dresden-Leipzig, 1955) determined as "LVE" (Löhlein-Volhard unit).
  A Löhlein-Volhard unit is the amount of enzyme that digests 1.725 mg casein under the specific conditions of the method. Continue are used in the following for the activity determination of the enzymes effective in the acidic range, which are derived from the Anson method. These are referred to as "proteinase units (hemoglobin)" U _Hb . A U _Hb corresponds to the amount of enzyme which catalyzes the release of trichloroacetic acid-soluble fragments from hemoglobin equivalent to 1 µmol of tyrosine per minute at 37 degrees C (measured at 280 nm). (1 mU _Hb = 10⁻³ U _Hb .)
  The switch is carried out in the presence of at least one surfactant T. The surfactants T used are preferably anionic and, in particular, neutral surfactants, as described, for example, in DE-A 33 12 840 and AU-C 558 447, or mixtures of the two. (See F. Stather, tanning chemistry and tanning technology, Akademie-Verlag, Berlin, 1967). As a rule, 0.1 to 1, preferably 0.1 to 0.3% by weight of the surfactants T, based on the salt weight of the hides and skins, are used. The simultaneous use of neutral and anionic surfactants is particularly preferred, a ratio of 3: 1 to 10: 1 parts by weight having proven to be expedient as a guide.
  Surfactants of the following types may be mentioned, for example:
  • A. Polyglycol derivatives (exemplary commercial products in brackets)
    • α) fatty acid polyglycols (EMULPHOR®)
    • β) fatty alcohol polyglycol ether (FORYL D®)
    • γ) Alkylphenol polyglycol ether (EUMULGIN®) 286, (FLUIDOL W100®, IGEPAL C®
    • δ) Fatty acid ethanol amide polyglycol ether (C®, FORYL KW®) EUMULGIN
  • B. glycerol derivatives
    • α) fatty acid monoglycerides (TEGOMOL S®)
    • β) fatty acid polyglycerol esters
    Further anionic emulsifiers, for example of the following types:
  • C. sulfates R'-OSO₃Na
    • α) Fatty alcohol sulfates, primary EPPOL DL conc.®, PERAMIT ML® and secondary TEEPOL®
    • β) fatty alcohol ethoxylated sulfates (TEXAPON Q®)
    • γ) monoglyceride sulfates (VEL®)
    • δ) Sulfation products of unsaturated oils and fatty acids (LEDEROLINOR DKMS®)
  • D. Sulfonate R SO₃Na
    • α) Alkylbenzenesulfonates (ABS, TPS) (MARLOPON®, MARLON®)
    • β) alkyl sulfonate (MERSOLAT®)
    • γ) fatty acid condensation products (IGEPON A®, IGEPON I®)
    • δ) Petroleum sulfonates (contained in: GRASSAN B®)
    • ε) Sulfitation products of unsaturated fatty oils and fatty acids (CUTISAN BS®)
    • ζ) short-chain alkylbenzenesulfonates, for example of cumene, toluene or xylenol,
  where the radical R '(unless stated otherwise) is a long-chain alkyl radical, preferably having 8-28 carbon atoms.
  In the process according to the invention, the switch can be carried out, for example, by inserting the salted skin material into the soft water to which one or more surfactants T, preferably in the stated concentrations, have been added or added during the course of the soft process. The softening process can be carried out in the devices customary for such processes, for example in a mixer, drum, tanning machine or reel.
• b) The incubation step
  is preferably carried out with a fresh, aqueous liquor, inter alia to ensure that the reaction conditions are constant. The liquor in which the soaked hides or skins are incubated is essentially free of
  inorganic sulfide. The liquor preferably makes up 50-80% by weight, based on the salted or fresh hides or skins.
  The fleet contains an EM depilatory with the following components:
  • at least one organic sulfur compound RED-S, which has a reducing action in the present system, in quantities of 0.05 to 5% by weight, based on the salt weight or the fresh weight of the hides and skins,
  • at least one hydrotropic HY in amounts of 0.05 to 2% by weight based on the salt weight or the fresh weight of the hides and skins,
  • one or more amines A in amounts of 0 to 2% by weight, preferably 0.05 to 2% by weight, based on the salt weight or the fresh weight of the hides and skins,
  that work together synergistically in the sense of the task at hand.
  The pH of the liquor in the incubation step is 9-11, preferably 9.5-10.5; this pH value comes partly from the amine A, partly from the alkali used, for example in the form of alkali mercaptides.
  The effectiveness of the reducing, organic sulfur compounds RED-S can be interpreted to mean that at pH 10 - 12.5 they are able to cleave the disulfide bridges of the preceratin, but leave those of the outer hair keratin largely intact. In other words, the (pH-dependent) redox potential of the organic sulfur compound RED-S can be higher in the EM system than that of keratin (E₀ = -420 mV). Without having to commit yourself to this model concept, it allows the selection of suitable organic sulfur compounds.
  RED-S organic sulfur compounds which preferably have a reducing action are those of the formula I.
  
  
  
  R₁ SH I
  
  
  
  in which R₁ represents an optionally branched, optionally cyclic alkyl radical having 2 to 24 carbon atoms, in particular 2 to 18 carbon atoms, especially 2 to 12 carbon atoms, where the alkyl radical can be hydroxy- or thiol-substituted, or for a radical - (CH₂) p- NR₂ R₃
  wherein R₂ and R₃ independently represent hydrogen or an alkyl radical having 1 to 6 carbon atoms, or with the inclusion of a further nitrogen, oxygen or sulfur atom form a (preferably saturated) heterocycle and p represents an integer from 2 to 6 or for a radical -R₄-COOR₅, wherein
  R₄ is an optionally branched, optionally substituted with another COOR₅ group alkyl radical having 2 to 6 carbon atoms, where -SH can be bound to a primary, secondary or tertiary carbon atom and wherein R₅ is hydrogen or an alkyl radical having 1 to 6 carbon atoms
  or the formamidine sulfonic acid in question.
  Particularly suitable compounds of the formula I are mercaptans, especially n-alkyl mercaptans, such as n-butyl mercaptan, n-amyl mercaptan, n-dodecyl mercaptan, mercaptans from LOROL® types, n-tetradecyl mercaptan and hydroxy-substituted alkyl mercaptans such as 2-mercaptoethanol, 3-mercapto -1,2-propanediol, further amine-substituted alkyl mercaptans such as β- (di-n-amylamino) ethyl mercaptan, these compounds being predominantly present in the form of their salts in accordance with the pH. Also to be mentioned are the mercapto-mono- and the -dicarboxylic acids or their salts such as mercaptoacetic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, mercapto-succinic acid. Formamidine sulfinic acid (thiourea dioxide) may also be mentioned.
  Suitable hydrotropes HY are described, for example, in H. Rath et al. Melliands textile report 43 (7) 718 (1962).
  Hydrotropics of the formula II are preferably found
  
  wherein R is hydrogen, -NH₂, -CH₃ or -NH-CN and X is oxygen, sulfur or NH or X together with R forms a heterocyclic system with the proviso that the heterocyclic system has only nitrogen heteroatoms and / or acid addition salts derived therefrom, for example hydrochlorides, sulfates, phosphates and rhodanides, application.
  Urea, thiourea, acetamide, formamide, guanidine, melamine, dicyandiamide may be mentioned in particular. The same procedure can be used as for the turnout. Here too, the process temperature is preferably 25-28 degrees C.
  A suitable amine A may optionally be present as a further component of the depilatory agent EM. Appropriately, it is a toxicologically or ecologically harmless amine, for example a not very volatile one.
  The amines A are preferably represented by the formula III
  
  
  
  R₆NR₇R₈ III
  
  
  
  wherein R₆ is an optionally substituted with an OH group, optionally cyclic alkyl radical having 1 to 8 carbon atoms and R₇ and R₈ are hydrogen or have the same meanings as R₁ or wherein R₂ and R₃ together with the nitrogen and optionally a further nitrogen or Oxygen atoms form a 5- or 6-membered heterocycle with the proviso that when a heterocycle R₆ is also hydrogen.
  By definition, amine component A can be a primary, secondary or tertiary amine, or a mixture of several amines. For example, the use of hydroxyl-substituted alkylamines such as ethanolamine, diethanolamine and triethanolamine is favorable.
  Dimethylamine, diethylamine, cyclohexylamine and piperidine may also be mentioned. c) The immunization phase
  is synonymous with the alkali activation of the EM system (while the incubation step technically means that the reducing agent runs at a lower pH). It is characterized by the addition or the presence of bases B to the liquor, as a result of which a pH of 10-14, preferably 12-14, is set. In general, the pH of the immunization phase is thus above the pH of the incubation step, for example by at least 0.5-1 pH units. The mechanistic interpretation suggests that the conversion of cysteine to lanthionine occurs in keratin in the immunization phase.
  The increase in the redox potential of the EM system with the reducing, organic sulfur compound RED-S caused by the pH increase must be seen in this context.
  The duration of the immunization phase is usually about 1 to 5 hours, in particular 1 to 3 hours, preferably closer to 1 hour. Working in the tanning drum or the reel has proven to be expedient, with - preferably discontinuous - moving having advantages. As a rule of thumb, you can move half of the time in approximately 10 minute intervals. It is preferred to work at 25-28 degrees C. In principle, inorganic bases such as those used in liming, for example, can be used as bases B. find, are used, such as alkalis. However, the use of calcium oxide in the hydrate form common with liming (liming lime or hydrated lime: cf. F. Stather, tanning chemistry and tanning technology, Akademie-Verlag, Berlin, 1967, p. 169) has proven particularly useful usually 0.5 - 5% by weight based on the weight of the skins or skins, however, the incubation step and the immunization phase can also merge into one another, for example by using the constituents of the depilatory agent EM simultaneously with base B, especially with the calcium hydroxide will.
  d) The hair loosening step
  uses inorganic sulfide as an effective agent, i.e. the sulfide or hydrogen sulfide anions. Appropriately, these are added in the form of NaHS or Na₂S, in the first case about 0.7 to 1.2% by weight sodium hydrogen sulfide (usually 72%), in the latter case 1 - 2% by weight based on that Weight of the skins or skins can be used. The pH should be in the range 10-14, preferably 12-14. The exposure time is a minimum of 20 - 30 minutes and up to 1 to 3 hours. The temperature here is also advantageously at 25 to 28 degrees C. It can be assumed that for the hair loosening the considerably high redox potential of the sulfide-containing solution under the conditions used (E _o = -500 to -550 mV) is responsible, which is sufficient for the more or less complete reduction of the preceratin without destroying the immunized outer hair keratin.
• e) The hair separation
  The treatment separates hair and skin. By pumping the depilatory liquor over an externally attached sieve, the hair can be completely removed and then washed and dewatered. However, the hair can also be left in the liquor and the liming or skin digestion can then be carried out. The hair is then separated in the sense of a mechanical preliminary clarification.
• f) The liming step
  The liming step is used to remove the base hair and to complete the skin disruption. After the previous operations, the pelts are not completely erased, as a guide to 1/3 to 1/2 of the pelvis thicknesses. The complete cremation of the skins generally takes place with the improvement of water, alkali and liming aids AH. There are various options for carrying out the liming. Liming aids AH and lime, preferably in amounts of 1-4% by weight, based on the hides, and inorganic sulfides in amounts of 0.3-0.6% by weight, based on the hides, can be added to the liquor. The liming time is generally 20 to 24 hours (process variant 5A).
  One obtains nakednesses of desirable smoothness and basic purity and little draft is observed. Overall, a dimensional gain can also be achieved.
  In another variant, proceeding from a skin (on average 1/3 washed through), proceed as follows:
  The liquor is first drained off, the skins are removed and washed preferably using acids which are acceptable from a gerberic point of view, such as organic acids such as acetic acid or phosphonic acids (cf. DE-A 35 33 203) or acidic polyphosphates, in order to reduce the slipperiness To reduce skins and improve handling. It is then fleshed and split in a manner known per se. (See F. Stather, tanning chemistry and tanning technology, Akademie-Verlag, Berlin, 1967).

bacillus subtilis
** aspergillus parasiticus

The scar gaps, preferably in the barrel, are expediently treated further with the immunization liquor (which comes from the immunization step c) with the addition of liming lime and sulfide in analogy to process variant 5A) see above, usually in the scar splitter ashes for 6-36 hours. The fleet originating from the grain scarifier is appropriately stored in the tank for further use / recycling.

The meat splits are - advantageously in the fleet originating from the grain splitting ash-maker with the improvement of liming lime and water; So "open" recycling is practiced. A liming time of 6 - 36 hours is also recommended here, preferably at 25 - 28 degrees C.
An oxidizing agent suitable for the oxidation of sulfur in the sulfide stage is advantageously added to the meat splitter, preferably from the group consisting of per compounds such as peroxides or iron-II salts, Mn-II salts, permanganates, quinones, generally in amounts of 0.001 up to 1% by weight based on the weight of the meat split.
The meat splitter with sulfide oxidation is carried out, for example, in a mixer while pumping around the liquor. As a guide, about 50-150 ppm of a Mn-II salt, for example manganese sulfate, is added. Elemental sulfur, mostly in colloidal form, separates out under the action of the oxidizing agents. In this way, the sulfide content of the liquors can be reduced by 70 to 95%.

ADVANTAGEOUS EFFECTS

• Reduzierung der Abwasserfracht im Äscher bezüglich CSB um ca. 30 - 50 %, Sulfid von 40 - 60 %, Stickstoff um 30 - 40 % sowie der Feststoffe um 60 - 70 %.
• Gute Erhaltung der Haarstruktur und dadurch verbesserte Entwasserbarkeit.
• Die Möglichkeit des Spaltens im nativen Zustand der Haut, da nach der Haarentfernung lediglich 20 - 25 % der Haut durchgeäschert sind. Spalten in diesem Zustand ergibt sehr glatte Leder.
• Ein hohes Maß an Betriebssicherheit, da Gefahr der Immunisierung in den Haarwurzeln bei zu langer Behandlung mit Kalkhydrat ausgeschlossen ist.

The method according to the invention in the intended sequence of technological measures offers a number of unexpected advantages, which in particular also have an advantageous effect on the ecology, for example:

• Reduction of the wastewater load in the liming with respect to COD by approx. 30 - 50%, sulfide from 40 - 60%, nitrogen by 30 - 40% and the solids by 60 - 70%.
• Good maintenance of the hair structure and thus improved dewaterability.
• The possibility of splitting in the native state of the skin, since only 20-25% of the skin has been erased after hair removal. Splitting in this condition results in very smooth leather.
• A high degree of operational safety, as there is no risk of immunization in the hair roots if the treatment with hydrated lime is too long.

The following examples serve to illustrate the invention. The chemical oxygen demand (COD) is determined according to Ullmann, 4th edition, loc.cit., Vol. 6, p. 376 (1981).

EXAMPLES

Unless otherwise noted, the percentages are percentages by weight based on the weight of the skins and skins used.

example 1

Hair-preserving liming process of cowhides in tanning barrels for the production of upper leather; Process without intermediate splitting of the skins.

Starting material:

Dirt-soaked German cowhide (25 - 29 kg); Percentages relate to salt weight or green weight.

Main switch

150% water, 28 degrees C.
0.25% proteolytic enzyme based on bacterial proteases, activity 4500 LVU / g
0.2% sodium hydroxide solution, 50%
0.3% non-ionic surfactant (nonylphenol with 8 - 9 mol ethylene oxide)
Let run for 270 minutes, density 3 degrees Be, pH 9 - 9.5. Drain the fleet.

Incubation phase

50% water, 27 degrees C.
1.2% ash ash aid consisting of
10% by weight of triethanolamine, 20% by weight of thioglycerol, 14% by weight of guanidine hydrochloride, 66% by weight of water
Move for 30 minutes, rest for 30 minutes, pH 10 - 10.8.

Immunization phase

+ 1% hydrated lime, move for 60 minutes.

Hair loosening phase

+ 0.7% sodium sulfhydrate (72%).
After 20 minutes of hair loosening; Hair is continuously separated using an external sieve. Skins are hair-free after approx. 90 - 120 minutes. The fleet is also largely free of hair.

Main ashtray

+ 100% water, 26 degrees C.
0.3% sodium sulfhydrate
2.5% hydrated lime
Move for 15 minutes.
0.2% sodium hydroxide 50%
for 14 hours: move 1 minute per hour; Drain the fleet.

Waste water values of the grayling residue fleet

Sulfide content 1150 mg / l COD content 20 300 mg 0₂ / l

for comparison

Conventional hair-destroying liming with the same sulfide supply and the same liming time (without post-liming): Sulfide content 1260 mg / l COD value ¹⁾ 31 700 mg O₂ / l ¹⁾ COD values increase due to the necessary post-washing by approx. 16,000 - 18,000 mg 0₂ / l (150% water, 3.5 hydrated lime, 8 hours).

To wash

Twice with each
200% water
0.1% 1,1-hydroxyethane diphosphonic acid, 60%
washed for 15 minutes each.

Example 2

Hair-preserving liming process of cowhides in tanning barrels for the production of upper leather; Procedure with "intermediate splitting" of the skins.

“Intermediate splitting” means that the skins are washed after depilation and are fleshed and split in a non-swollen, only partially ashed state.
The scars are finally washed through in the depilatory liquor with the addition of washing water (see above) lime and sulfides. The meat column was cremated in the fleet of scar-gap washer with the addition of hydrated lime. In the liming of the meat slice, with the addition of manganese-II-sulfate and with strong movement (oxygenation), an oxidation of residual sulfide is carried out at the same time.

Starting material :

Dirt-soaked German, salted or fresh cowhide (25 - 29 kg); Percentages relate to salt or fresh weight.
The dirt-softened skins are soaked and depilated as in Example 1.

After the hair separation is complete, the liquor is drained off and stored in a tank A. The skins are then washed.

Washing :

200.0% water
0.1% hydroxyethyl diphosphonic acid (60%)
Move for 20 minutes.
Drain the liquor and store it in tank B for further use.

Skins are unloaded from the barrel, fleshed and split to a thickness of 2.5 - 3.5 mm. Scar and meat gaps are partially washed through and processed separately as follows.

Ashes of the grain gap (percentages refer to the weight of the grain gap).

100.0% wash water fleet from tank B
+ whole depilation fleet from tank A
+ 3.0% hydrated lime
0.3% sodium sulfate (72%)
Move for 5 minutes.
+ 0.2% sodium hydroxide solution, 50%
for 20 hours: move for 1 minute per hour, drain the liquor and store in tank C.

Waste water values of the liming fleet

Sulfide content 1010 mg / l COD value ¹⁾ 21 350 mg O² / l ¹⁾ In the case of a process variant with intermediate splitting of the skins, no post-refining of about 8 hours is required.

Wash the scar cleft

Wash 2 x 15 minutes with each
200.0% water
0.1% 1,1-hydroxyethane diphosphonic acid, 60%

Ashes of the meat column (percentages refer to the weight of the meat column).

The liming of the meat column is carried out with the addition of lime in the fleet of the scarifier. The addition of manganese-II-sulfate and abundant agitation in the drum, the reel or the mixer, that is to say by air circulation, simultaneously causes the oxidation of the sulfide formed.
Place the meat slice in a mixer equipped with equipment for pumping around the fleet.
+ Fleet from tank C.
+ 3.0% calcium hydroxide
+ 0.2% sodium hydroxide solution
+ 100 ppm Mn (II) sulfate (add 1:20 diluted in water) (dosage of Mn (II) sulfate refers to liquor length).
Move 14 hours.

Waste water values :

Sufid 75 mg / l COD 17 450 mg O₂ / l

These values are to be compared with those of a conventional hair-destroying method (see under example 1).

Washing the meat column :

Wash 2 x 15 minutes with each
200.0% water
0.1% 1,1-hydroxyethane diphosphonic acid, (60%)

Example 3

Hair-preserving liming process of salted veal skins in the reel.

Starting material :

Soiled salted veal skins (20 - 24 kg); Percentages refer to salt weight.

Main switch :

240.0% water, 22 degrees C.
0.2% non-ionic surfactant (nonylphenol with 8 - 9 mol ethylene oxide)
0.1% preservative (chloroacetamide)
Move for 15 minutes, let it rest for 120 minutes. Total soak time: 20 - 22 hours, drain the fleet.

Enzyme switch :

240.0% water
0.2% proteolytic enzyme based on a bacterial protease from Bacillus subtilis, activity 3,200 LVU / g
0.8% soda
Move for 3 hours; pH 9.3-9.7. Drain the fleet.

Incubation phase :

240.0% water
1.4% of a mixture consisting of 10% by weight of triethanolamine, 20% by weight of thioglycerol,
14.0% by weight guanidine hydrochloride, 66% water
Move for 30 minutes, leave for 30 minutes

Immunization phase :

+ 2% hydrated lime
Move 30 minutes, rest 30 minutes, move 30 minutes.

Hair loosening phase

+ 0.8% sodium sulfate (72%)
Move for 10 minutes
+ 0.8% sodium sulfate (72%)
Move for 90 minutes until skins are hair free, separate hair by recycling.

Liming :

+ 2.0% hydrated lime
Move for 30 minutes
0.6% sodium sulfide (60%)
Move 30 minutes,
then for 16-20 hours:
Move for 15 minutes, rest for 120 minutes; pH 12.2-12.6. Drain the fleet.

Washing :

2 x 15 minutes with each
250.0% water
0.1% 1,1-hydroxyethane diphosphonic acid, 60%

Example 4

Hair-preserving liming process of dried goat skins.

Starting material :

Dried goat skins, percentages relate to dry weight.

Switch :

800.0% water, 28 degrees C.
1.3% proteolytic enzyme based on bacterial proteases, activity 4,500 LVU / kg
1.0% non-ionic surfactant (nonylphenol with 8 - 9 mol ethylene oxide)
0.2% preservative based on chloroacetamide
4.5% soda
Move for 10 minutes
for 22 - 24 hours:
Move for 2 minutes, let stand for 30 minutes, drain pH 9.3 - 9.8 liquor, walk dry for 30 minutes.

Incubation and immunization phase :

250.0% water, 28 degrees C.
5.0% liming aid consisting of 10% by weight of triethanolamine, 20% by weight of thioglycerol, 14% by weight of guanidine hydrochloride, 66% by weight of water
3.5% hydrated lime
Move 60 minutes.

Hair loosening phase :

+ 50.0% water, 28 degrees C.
5.0% sodium sulfate (72%)
Add 3.5% soda solution, 33%, diluted 1: 5.
Move for 90 - 120 minutes until skins are hair free, separate hair by recycling.

Liming :

+ 100.0% water, 28 degrees C.
4.0% hydrated lime
0.7% sodium sulfate hydrate, 72%
Move 60 minutes,
then for 18 - 22 hours:
Move for 5 minutes, rest for 50 minutes, pH 12.3 - 12.6. Drain the fleet.

Washing :

Wash 2 x 15 minutes with each
400.0% water, 26 degrees C.
0.1% 1,1-hydroxyethane diphosphonic acid, 60%

Example 5

Is carried out analogously to Example 1, but 1.8% by weight (based on the salt weight) of the following mixture is used for the incubation phase:
15% by weight diethanolamine
10% by weight of thioglycolic acid
17% by weight urea
ad 100 wt .-% water
The sulphide content and COD value of the ashtray are almost identical to example 1

Example 6

Carrying out the process analogously to Example 1, but 1.5% by weight of a liming aid of the following composition is used for the incubation step:
22% by weight of a 5% aqueous solution of the sodium salt of mercaptoethanol
5% by weight dimethylamine
10% by weight ammonium cumene sulfonate
ad 100 wt .-% water

Example 7

Carried out analogously to Example 1, but in the incubation phase 1.0% by weight (based on the salt weight), a liming aid of the following composition is used:
25% by weight urea
75% by weight thiourea-S, S-dioxide
The mixtures according to Examples 5-7 can be used with equally good success in the process variant according to Example 2.

Example 8

Carried out analogously to Example 1, but 0.25% by weight (based on the salt weight) of nonionic surfactants of the following composition are used for the switch:
40 wt .-% C₁₁-C₁₅ oxo alcohol with 6 moles of ethylene oxide
20 wt .-% C₁₁-C₁₅ oxo alcohol with 9 moles of ethylene oxide
20 wt .-% C₁₁-C₁₅ oxo alcohol with 12 moles of ethylene oxide.

Example 9

The procedure was analogous to Example 1, except that 0.2% by weight (based on the salt weight of a surfactant of the following composition) was used in the switch:
20% by weight sodium dodecylbenzenesulfonate
40 wt .-% sodium salt of C₉-C₁₈ fatty alcohol ether sulfate
ad 100 wt .-% water

Example 10

Process procedure according to Example 1, but 0.2% by weight of an enzyme product based on bacterial protease, fungal protease and pancreatic protease of the following composition was used:
2 500 LVE / g bacterial protease, obtained from a Bacillus licheniformis strain
1,000 LVE fungal protease obtained from Aspergillus parasiticus
1 000 LVE pancreatic protease
* such as from Bac subtilis
** such as from aspergillus parasiticus

Claims (20)

1. A process for liming skins and hides, while maintaining and separating the hair, which comprises a soaking and subsequent liming process, the hair being immunised by a controlled pre-treatment with alkali, characterised in that the skins and hides are

   a) treated for 4 to 48 hours in a soak which consists of an aqueous float having a pH value of 7 to 10.5 containing at least one Tenside T, then,

   b) in an incubation step,
   the soaked skins and hides are treated at a pH value of 9 to 11 for 30 to 180, preferably 45 to 90 minutes, with an aqueous float which largely contains inorganic sulphide-free depilatory EM based on reductively active organic sulphur compounds RED-S, and hydrotropics HY, and then,

   c) in an immunisation phase,
   the float, having a pH value within the range of from 10 to 14 as a result of the addition of bases B, is allowed to act for 1 to 12 hours on the skins and hides, while being stirred, and then,

   d) in a hair-loosening step,
   the float, to which inorganic sulphide AS has been added in amounts of 0.5 to 3 weight %, based on the salted or fresh weight of the skins and hides, is allowed, within the pH range of from 10 to 14, to act on the skins and hides for 30 to 180 minutes and

   e) hair and skin are separated from one another and,

   f) in a liming step,
   the skins thus obtained are limed-through while adding water, alkali and liming auxiliaries AH, with the proviso that each float represents 50 to 500 weight % of the skin or hide material used.
2. A process according to claim 1, characterised in that the Tenside T is used in amounts of 0.1 to 1.0, preferably 0.1 to 0.3 weight %, based on the salted or fresh weight of the skins and hides.
3. A process according to claims 1 and 2, characterised in that the Tenside T is a neutral and/or an anionic Tenside.
4. A process according to claims 1 to 3, characterised in that the soak contains at least one proteolytic enzyme in amounts corresponding to 2,000 to 20,0000 Löhlein-Volbard-Units per kg of salted or fresh weight of the skins and hides.
5. A process according to claim 4, characterised in that a mixture of bacterial protease such as Bac. subtilis, fungus protease such as aspergillus parasiticus and pancreas protease is used, the amount of the bacterial protease being 20 to 70% of the total activity.
6. A process according to claims 1 to 5, characterised in that the reductive, organic sulphur compounds RED-S used are those of Formula I
   
   
   
           R₁ SH   I
   
   
   
      wherein R₁ represents an optionally branched, optionally cyclic alkyl group having 2 to 24 carbon atoms, in particular 2 to 18 carbon atoms, especially 2 to 12 carbon atoms, in which the alkyl group may be hydroxy or thiol-substituted, or a group -(CH₂)_p -NR₂R₃,
      wherein R₂ and R₃ independently represent hydrogen or an alkyl group having 1 to 6 carbon atoms, or by inclusion of a further nitrogen, oxygen or sulphur atom, form a (preferably saturated) heterocyclic group and p represents an integer of 2 to 6 or a group -R₄-COOR₅, wherein R₄ denotes an optionally branched alkyl group with 2 to 6 carbon atoms, which may optionally be substituted by a further -COOR₅ group, wherein
   -SH may be bonded to a primary, secondary or tertiary carbon atom, and wherein R₅ represents hydrogen or an alkyl group with 1 to 6 carbon atoms,
   or formamidine sulphinic acid.
7. A process according to claims 1 to 6, characterised in that the hydrotropics HY used are those of Formula II

   

   wherein R represents hydrogen, -NH₂, -CH₃ or -NH-CN and X represents oxygen, sulphur or NH, or X, together with R, forms a heterocyclic system with the proviso that the heterocyclic system only has nitrogen heteroatoms and/or the acid addition salts derived therefrom are used.
8. A process according to claims 1 to 7, characterised in that the depilatory EM additionally contains amines A of Formula III
   
   
   
           R₆NR₇R₈   III
   
   
   
   wherein R₆ represents an optionally cyclic alkyl group with 1 to 8 carbon atoms, which is optionally substituted by an OH group, and R₇ and R₈ represent hydrogen or have the same meanings as R₁ or wherein R₂ and R₃, together with the nitrogen and optionally a further nitrogen or oxygen atom, form a 5- or 6-membered heterocyclic group with the proviso that R₆ may also represent hydrogen if a heterocyclic group is present.
9. A process according to claims 1 to 8, characterised in that a new float is used for the incubation step.
10. A process according to claims 1 to 9, characterised in that calcium hydrate is used as a base B in the immunisation phase.
11. A process according to claim 1, characterised in that the liming is carried out for 12 to 36 hours, while maintaining the float, under the addition of water, alkali, inorganic sulphides and liming auxiliaries.
12. A process according to claims 1 to 10, characterised in that after depilation and removal of the hair the float is stored separately from the skins for re-use.
13. A process according to claim 12, characterised in that the skins separated from the float are treated for 10 to 30 minutes with fresh water while an agent is added which has been neutralised with alkali.
14. A process according to claims 12 and 13, characterised in that the washing float is collected for re-use and stored.
15. A process according to claims 12 and 13, characterised in that the resultant skins, only partially limed-through, are fleshed and split.
16. A process according to claims 12 and 15, characterised in that the resultant split leather is limed for 6 to 36 hours in the float, according to claim 12, to be re-used, while adding fresh water or the washing float according to claim 14, alkali, inorganic sulphides and liming auxiliaries.
17. A process according to claim 16, characterised in that the float formed in the liming of the split leather is stored for re-use.
18. A process according to claim 15, characterised in that the flesh split obtained during splitting in the float produced according to claim 17 is limed for 6 to 36 hours, while adding alkali, optionally water and oxidation agents known per se.
19. A process according to claim 18, characterised in that the oxidation agents are chosen from the group consisting of per compounds, more particularly peroxides, iron-III-salts, Mn-II-salts, permanganates, quinones, in amounts of 0.001 to 1 weight %, based on the weight of the split flesh.
20. A process according to claims 1 to 19, characterised in that the process is carried out at temperatures within the range of 20 to 30°C.