Classifications

• • C—CHEMISTRY; METALLURGY
  • C14—SKINS; HIDES; PELTS; LEATHER
  • C14C—CHEMICAL TREATMENT OF HIDES, SKINS OR LEATHER, e.g. TANNING, IMPREGNATING, FINISHING; APPARATUS THEREFOR; COMPOSITIONS FOR TANNING
  • C14C1/00—Chemical treatment prior to tanning
  • C14C1/06—Facilitating unhairing, e.g. by painting, by liming

Definitions

• the invention relates to a novel hair-preserving liming process from 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.
• 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, as are found in many technical enzyme preparations.
• 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.
• 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.
• the method can be carried out as follows.
• 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, if appropriate 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.
• the switch is expediently carried out overnight, preferably in the temperature range 25-28 ° C.
• the switch process can be carried out in a liquor which contains enzymes suitable for the switch process.
• proteolytic enzymes EC3.4.
• alkaline is particularly preferred Proteases with an optimum activity, approximately in the range of pH 7.5-13.
• a combination of enzymes is advantageously used, a proportion of bacterial protease being appropriate.
• the proportion of the bacterial protease e.g. of type *) at 20 - 70% of the total enzymatic activity.
• enzyme components e.g. Fungal proteases, e.g. of the type **), for example in proportions of 10-30% and / or pancreatic enzymes in proportions of 10-20% of the total activity.
• 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.
• Löhlein-Volhard unit is to be understood as the amount of enzyme which is 1.725 mg under the specific conditions of the method Digests casein 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 .
• 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 or AU-C 558 447, or mixtures of the two. (See F. Stather, tanning chemistry and tanning technology, Akademie-Verlag, Berlin, 1967).
• 0.1 to 1, preferably 0.1 to 0.3% by weight of the surfactants T 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.
• Surfactants of the following types may be mentioned, for example:
• 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 in 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.
• 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.
• 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
• 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 to leave those of the outer hair keratin largely intact.
• Red-S organic sulfur compounds which have a reducing action are preferably those of the formula I.
• R1 SH I wherein 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 substituted by hydroxy or thiol, 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 including a further nitrogen, oxygen or sulfur atom form a (preferably saturated) heterocycle and p represents an integer from 2 to 6 or for a residue -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 bonded to a primary, secondary or tertiary carbon atom and wherein R5 is hydrogen or an alkyl radical
• 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 ⁇ - (di-n-amylamino) ethyl mercaptan, these compounds being predominantly present in the form of their salts in accordance with the pH.
• n-alkyl mercaptans such as n-butyl mercaptan, n-amyl mercaptan, n-dodecyl mercaptan,
• 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
• Suitable hydrotropes HY are described, for example, in H. Rath et al. Melliands textile report 43 (7) 718 (1962).
• 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.
• 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 another nitrogen or Oxygen atoms form a 5- or 6-membered heterocycle with the proviso that when a heterocycle R6 is also hydrogen.
• amine component A can be a primary, secondary or tertiary amine, or a mixture of several amines.
• hydroxyl-substituted alkylamines such as ethanolamine, diethanolamine and triethanolamine is favorable.
• Dimethylamine, diethylamine, cyclohexylamine and piperidine may also be mentioned.
• 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.
• inorganic bases such as those used in liming, for example, can be used as bases B. find, are used, such as alkalis.
• lime or hydrated lime cf. F. Stather, tanning chemistry and tanning technology, Akademie-Verlag, Berlin, 1967, p. 169.
• the addition of lime hydrate to the liquor lies 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.
• the hair loosening step uses inorganic sulfide as an effective agent, i.e. the sulfide or hydrogen sulfide anions.
• 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 minimum exposure time is 20 - 30 minutes and up to 1 to 3 hours.
• the temperature here is also advantageously at 25 to 28 degrees C.
• the treatment separates hair and skin.
• the hair 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.
• the liming step is used to remove the base hair and to complete the skin disruption. After the previous operations, the pelts are not fully ashed, 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.
• 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 20-24 hours (process variant 5A). One obtains nakednesses of desirable smoothness and basic purity and observed little draft.
• a dimensional gain can also be achieved.
• proceeding from a skin proceed as follows: The liquor is first drained off, the skins removed and washed, preferably using acids which are acceptable from a gerberic point of view, such as, for example, organic acids such as, for example, acetic acid or phosphonic acids (cf. 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).
• the scar gaps are expediently treated further with the immunization liquor (which is obtained 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 gap scrubber for 6-36 hours.
• the fleet originating from the grain scarifier is expediently kept in the tank for further use / recycling.
• the meat cracks are - advantageously in the fleet originating from the scar ash scrubber, 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.
• Elemental sulfur is deposited under the action of the oxidizing agents, usually in colloidal form. In this way, the sulfide content of the liquors can be reduced by 70 to 95%.
• 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, since there is no risk of immunization in the hair roots if the treatment with hydrated lime is too long.
• COD chemical oxygen demand
• the percentages are percentages by weight based on the weight of the skins and skins used.
• Intermediate splitting means that the skins are washed after depilation and are fleshed and split in a non-swollen, only partially ashed state. The scar splits are finally washed through in the depilatory liquor with the improvement of washing water (see above) lime and sulfides.
• the meat column was washed through in the fleet of scar-gap washer with the addition of hydrated lime. In the liming of the meat column, with the addition of manganese-II-sulfate and with strong movement (oxygenation), an oxidation of residual sulfide is carried out at the same time.
• the liquor is drained off and stored in a tank A.
• the skins are then washed.
• the liming of the meat column is carried out with the addition of lime in the fleet of the scarifier.
• 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.
• Example 1 Is carried out analogously to Example 1, except that 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 wt% urea ad 100 wt .-% water
• the sulphide content and COD value of the ashtray are almost identical to Example 1
• Example 5 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 of thiourea-S, S-dioxide
• a liming aid of the following composition is used: 25% by weight urea 75% by weight of thiourea-S, S-dioxide
• Example 2 The procedure is analogous 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.

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Treatment And Processing Of Natural Fur Or Leather (AREA)
• Cosmetics (AREA)
• Medicines Containing Material From Animals Or Micro-Organisms (AREA)
• Enzymes And Modification Thereof (AREA)

Applications Claiming Priority (2)

Publications (3)

Family

ID=6346234

Family Applications (1)

Country Status (6)

Cited By (5)

Families Citing this family (21)

Family Cites Families (8)

• 1988
  • 1988-01-29 DE DE3802640A patent/DE3802640A1/de not_active Withdrawn
• 1989
  • 1989-01-23 DE DE58908425T patent/DE58908425D1/de not_active Expired - Fee Related
  • 1989-01-23 AT AT89101120T patent/ATE112322T1/de not_active IP Right Cessation
  • 1989-01-23 ES ES89101120T patent/ES2061743T3/es not_active Expired - Lifetime
  • 1989-01-23 EP EP89101120A patent/EP0326059B1/fr not_active Expired - Lifetime
  • 1989-01-26 US US07/303,270 patent/US4960428A/en not_active Expired - Lifetime
  • 1989-01-27 BR BR898900352A patent/BR8900352A/pt not_active IP Right Cessation

Also Published As

Similar Documents

Legal Events