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
  • C14C3/00—Tanning; Compositions for tanning
  • C14C3/02—Chemical tanning
  • C14C3/04—Mineral tanning

Definitions

• leathers which are pure white and fast to light including the cut, can be obtained by means of aluminum or zirconium compounds, but compared with chrome-tanned leathers, these leathers have certain disadvantages during processing and also as finished products; they have, therefore, been accepted only to a limited extent and for special purposes, even when aftertreated with suitable synthetic tanning agents, fillers and fat-liquoring agents.
• the leather treated with aluminum compounds is harder, less plump, less elastic and resilient than chrometanned leather, it presents more difficulties for dyeing, dressing and processing and is substantially less serviceable.
• Tanning with zirconium has brought a substantial advance in the production of pure white leathers, but these are still not wholly satisfactory in some important respects.
• Zirconium-tanned leathers are still too firm or not sufficiently elastic and they are not so easily fat-liquored and processed.
• the zirconium, aluminum and chromium salts can be used either separately in any desired sequence or in the form of a mixture, but it is advisable to apply first the zirconium salt and subsequently the aluminum and chromium salts. It is also advantageous to use one of the three stated metal salts by itself and the other two metal salts in a mixture or in the form of a mixed complex by applying, for example, first the zirconium salt and then a mixture or a mixed complex of the aluminum and chromium salts.
• a preferred and particularly advantageous method of carrying out the tanning process according to the invention consists in using a mixed complex of zirconium, aluminum and chromium salts, as can be obtained, for example, by heating and/or dehydrating the aqueous solutions, for example by the heating of concentrated solutions, evaporation and/or spray-drying or roller-drying.
• zirconium, aluminum, and chromium are the sulphates.
• zirconium sulphates there may also be used, inter alia, technical zirconium sulphates which may contain finely divided silica gel.
• Zirconium sulphate or the corresponding ions can also be obtained during the tanning process by using zirconium oxychloride in the presence of sodium sulphate.
• aluminum sulphate other aluminum salts may also be used, for example aluminum chloride and aluminum acetate.
• chromium sulphate there may also be employed, inter alia, chromium nitrate, chromic chloride, chromium acetate, chromium formate, chrome alum and the like.
• the salts of zirconium, aluminum, and chromium may obviously also be used in complex form, for example, in the form of the known complexes of chromium and aluminum with organic and inorganic acids.
• the zirconium, aluminum, and chromium salts are present in the ranges of basicity customary for tanning purposes.
• these salts there may be used nontanning inorganic or organic salts and acids, as are commonly employed in the tanning industry, e.g., sodium sulphate, sodium sulphophthalate, sodium phthalate, sodium sulphosuccinate, sodium tartrate, as well as the acids from which these salts are derived, such as formic acid, acetic acid, phthalic acid, sulphophthalic acid, lactic acid, glycollic acid, sulphosuccinic acid, and citric acid.
• the zirconium, aluminum, and chromium salts acting as tanning agents are preferably used in the form of highly concentrated solutions or in the form of powders, tanning without a liquor being of particular advantage.
• tanning without a liquor in the meaning of the present invention comprises tanning processes in which the tanning agents are used without water or without substantial amounts of water.
• Tanning can also be performed with not so highly concentrated solutions, especially in the case of lighter leathers; the tanning through then proceeds more slowly.
• the tanning process itself is chiefly carried out by milling the pelts or leathers with the tanning agents in a rotating drum.
• the tanning can be performed in such a manner that pickled pelts the final pH value of which preferably lies between 2.0 and 3.5, are treated, after removal of the liquor, with a highly concentrated solution or a powder of a mixed complex of zirconium, aluminum, and chromium salts of the composition stated above, until they are completely tanned through, and the resultant leathers are deacidified and worked up in the usual manner.
• the tanning can also be carried out first .with a zirconium salt in concentrated or powdered form and subsequently continued in any desired sequence, but preferably first with an aluminum salt and then with a chromium salt or also with a mixed complex of these two metal salts. In all these cases the sulphates of zirconium, aluminum, and chromium are preferred.
• zirconium, aluminum, and chromium salts offer many advantages over the known tanning with one of these salts by itself or with a mixture of two of these salts.
• the effects obtained in respect of resistance to hot water, whiteness, feel, plumpness, elasticity, grain firmness and fineness of grain have hitherto not been achieved by purely mineral tanning, while the wearing properties of the leathers is improved.
• the proportion between the zirconium, aluminum, and chromium salts, referred to the metal oxides, ZrO :Al O :Cr O amounts to 100:5 to 50:2 to 30, preferably to 100:10 to 20:3 to 8 parts by weight.
• the use of such mixed complexes is a particular advantageous method of carrying out the process of the invention, but does not constitute any limitation thereof.
• the new process also permits the rapid tanning through of very thick hide materials.
• the tanning combination of salts of the three metals is completely absorbed by the hide material so that the finished leather may have a very high total oxide content of over 13%, depending on the amount used for tanning, and exhibit a corresponding plumpness and compactness of the fibre structure, while remaining soft and elastic.
• Hides of any thickness can be worked up according to the new process in a short time to produce the corresponding type of leather from glove leather to heavy upper leather, harness, belting and sole leather, and the additional use of other mineral, synthetic, vegetable or resin tanning agents and of fillers of organic or inorganic nature is also possible.
• the leather After shaving, the leather is deacidified with calcium formate and sodium bicarbonate or other conventional neutralising agents in a short liquor, until a level blue-green to blue coloration of the leather cut is achieved with gromocresol green, it is then fat-liquored with 36% pure fat calculated as pure fat content in the form of fat-liquoring products commonly used for the fat-liquoring of white leather, and dried.
• Tanning agent 800 parts of a technical zirconium sulphate containing 25% ZrO about 1 mol silicic acid and about 1 mol sodium sulphate per mol ZrO and having a basicity of about 45%, are mixed with 200 parts of an aluminum-chromium complex compound obtained according to the instruction given below, stirred with water in a ratio of 1:2 and heated to C. Heating of the solution is continued at 80 C. for about 15 minutes, and the reaction mixture is subsequently cooled to 40 C. and spray-dried.
• the powder thus obtained contains the metal oxides in the following proportion: parts ZrO 14 parts M 0 27 parts Cr O
• Preparation of the Al-Cr mixed complex A mixture of 17 parts technical aluminum sulphate (Al (SO -18H O) and 7 parts of a chromic sulphate lye with a basicity of 33% and a Cr O content of 18%, dissolved with heating in 15 parts water, is adjusted by the addition of 4 parts calcined sodium carbonate in 13 parts water to a total basicity of 50%.
• One part anhydrous sodium acetate in 2 parts water is added to this mixture at a temperature of 50 C.
• the mixed complex compound formed after a reaction time of about 5 hours is dried by the spraydrying method.
• the powdered product contains about A1203 and Cr203- EXAMPLE 2 Production of white cow leather (full grain upper leather, suede leather, nubuk) Cow pelts are tanned as described in Example 1 with the tanning agent described below. After shaving, the leather is deacidified and retanned with calcium formate and sodium bicarbonate with the addition of about 3% (referred to the shaved weight) of a syntan (condensation product from 1 mol dihydroxydiphenylsulphone, 2 to 2.5 mols formaldehyde and 1 to 1.25 mols sodium sulphite) and fat-liquored, as described in Example 1.
• a syntan condensation product from 1 mol dihydroxydiphenylsulphone, 2 to 2.5 mols formaldehyde and 1 to 1.25 mols sodium sulphite
• Tanning agent 100 parts of a technical zirconium sulphate containing 23% ZrO and about 1 mol silicic acid and about 1 mol sodium sulphate per mol ZrO and having a basicity of about 10%, are stirred with about 200 parts water and mixed with an aqueous solution of 21.5 parts of a technical aluminum sulphate (with 15% A1 0 and 8.9 parts of a technical chromic sulphate lye (with 18% Cr O and a basicity of 33%) in about 30 parts water. This mixture is heated at 80 C. for 15 minutes, cooled and dried by the spray-drying method. The resultant powder contains the metal oxides in the following proportion: 100 parts ZrO :14 parts Al O :7 parts CI2O3.
• EXAMPLE 3 Production of white or dyed sheep leather (for full grain leather and sude leather) Patras sheep skins which are prepared in the normal way and thoroughly degreased are pickled with sodium chloride, calcium formate and sulphuric acid in the usual manner so that the final pH is between 2.7 and 3.2. The pickling liquor is then discharged and 12% (referred to the pelt weight) of the technical zirconium sulphate described in Examples 1 and 2 are added through the drum door in powdered form by sprinkling over the hides or pasted with water about 1:1, and the pelts are drummed for about 2 hours until completely tanned through.
• 12% referred to the pelt weight
• the liquor is thoroughly discharged, and 3% of the aluminum-chromium mixed complex described in Example 1 are added through the drum door, again in powdered form.
• the amount of metal oxides used for the tanning corresponds to a ratio of 100 parts ZrO 14 parts Al O :7 parts C 0
• 2.5% of a commercial cation-active fat-liquoring agent are added through the hollow shaft of the drum, and drumming is continued for 90 minutes.
• the leather thus obtained is deacidified and retanned with calcium formate and sodium bicarbonate with the addition of about 4% (referred to the shaved weight) of, for example, the syntan mentioned in Example 2 as described in Example 1, and subsequently fat-liquored with 4 to 6% pure fat in the form of fat-liquoring products commonly used for white leather with the addition of wheat flour and kaolin or titanium dioxide pigment, and then dried.
• the leather to be dyed is deacidified without the addition of synthetic tanning agents and subsequently dyed, fat-liquored and dried in the usual manner.
• the leathers obtained according to Examples 1 to 3 are characterised by their white colour and the great compactness of the fibre, in addition to good softness, plumpness and excellent tear resistance.
• EXAMPLE 4 Production of white or dyed sheep leather from pickled sheep skins (for full grain and sude leather) [In this case the assumed pelt weight is the pickled weight plus 25%]
• Pickled sheep skins are depickled in the usual manner, degreased and repickled by means of sodium chloride, calcium formate and sulphuric acid. The pH value of the residual liquor is between 2.7 and 3.2.
• the pelts are then tanned with 9.4% of a technically pure zirconium sulphate containing 32% ZrO but no silicic acid, and having a basicity of about 45 to 50%, deacidified, retanned or dyed and fat-liquored as described in Example 3.
• Example 3 instead of 3% of the Al-Cr mixed complex used in Example 3, there is employed a mixture of a technical aluminum chloride with a content of 22% A1 and a basicity of about 65% and a technical chromic sulphate with a content of 25% Cr O and a basicity of 33%.
• the amount employed of the first compound corresponds to 0.54% Al O that of the second compound to 0.21% Cr O referred to the pelt weight), so that the ratio of the metal oxide combination is as 100 parts ZrO 18 parts Al O :7 parts Cr O
• the leather thus obtained is characterised by good grain firmness of the plumpness, feel and tear resistance.
• Kid pelts prepared for glove leather in the usual manner are pickled, tanned, deacidified, optionally dyed, fat-liquored and dried as described in Example 1.
• the leather to be dyed is also wetted back in the usual manner after drying, then dyed, again fat-liquored, dried and dressed in conventional manner.
• the white leather is characterised by its whiteness, extraordinary plumpness and good handle, the dyed leather by its high brilliancy, good fastness to light and very good general fastness properties.
• the splits When tanned through, the splits are deacidified as described in Example 1 by means of calcium formate and sodium bicarbonate, and fat-liquored in the conventional manner with the addition of white pigments.
• the splits thus obtained are characterised by their whiteness, good feel and excellent tear resistance.
• EXAMPLE 7 Production of white belt leather Cow neck pelts of about 4.5 mm. thickness which have been prepared in the conventional manner are pickled' with sodium chloride, calcium formate and sulphuric acid so that the final pH is between 2.7 and 3. Tanning is carried out with 15% of the tanning agent described in Example 2, the amount of metal oxides employed being so chosen that ratio of parts ZrO :30 parts Al O :8 parts Cr O is obtained in the tanning agent. Tanning through is achieved within about 2.5 to 3 hours.
• the leather is then neutralised and retanned with calcium formate and sodium bicarbonate with the addition of 5% (referred to the shaved weight) of a commercial cyntan as described in Example 1, fat-liquored in the usual manner with the addition of white pigments, and dried in a slightly stretched state.
• the leather thus obtained is characterised by a very good whiteness, compactness of fibre, grain firmness dressing property.
• EXAMPLE 8 Production of sole leather Cow butt pelts 5 to 6 mm. thickness prepared in the manner customary for this type of leather, are pickled with sodium chloride and sulphuric acid in the usual manner so that the final pH is between 2.5 and 3. The pelts must be thoroughly pickled, and this takes several hours. Tanning is subsequently carried out with 18% of the tanning agent described in Example 2. About 3-4 hours are required for tanning through.
• the leather is then levelled in the conventional manner, neutralised with calcium formate and sodium bircarbon-ate as described in Example 1, sammed and retanned in a drying drum with about 20% (referred to the samrned weight of the leather) of a sulphited quebracho extract in powdered form with the addition of the conventional fillers and fatlrquoring agents, dressed and dried.
• the leather thus obtained is characterised by a pale level shade, compact fibre structure and extraordinary resistance to abrasion.
• EXAMPLE 9 Production of s-ole leather The treatment is carried out in the manner described in Example 8.
• a synthetic tanning agent for example, a tanning agent described in German patent specification No. 675,775, or a mixture of both tanning agents.
• EXAMPLE 10 Production of calf sude leather
• the calf skins chrome-tanned in the conventional manner are retanned with 3% (referred to the shaved weight) of the tanning agent described in Example 1 in powdered form and in a short liquor, neutralised and further processed in the usual manner to sude leather, with or without an intermediate drying of the skins before dyeing.
• EXAMPLE 11 Production of sheep sude leather Chrome-tanned goat skins prepared in the manner customary for nappa leather are retanned with 6% (referred to the shaved weight) of the tanning agent desoribed in Example 1 in powdered form and with the addition of about 3% of a cation-active fat-liquoring agent, neutralised and further processed to sude leather in the usual manner.
• 6% referred to the shaved weight
• a cation-active fat-liquoring agent neutralised and further processed to sude leather in the usual manner.
• EXAMPLE 13 Production of nubuk leather (cow and calf leather)
• the leather which has been chrome-tanned in the usual manner is retanned with 6% (referred to the shaved weight of the leather) of the tanning agent described in Example 1 in powdered form and in a short liquor, deacidified and dyed, fat-liquored, dried and further dressed in the conventional way.
• the leathers obtained according to Examples 10 to 13 are characterised by a very fine and level nap, as well as by brilliancy, fullness and levelness of the dyeing, and in the case of nubuk leather also by an extraordinary grain firmness.
• EXAMPLE 14 Production of wool sheep or fur skins
• the skins prepared in the conventional manner are pickled with sodium chloride and sulphuric acid so that a final pH value of about 3 to 3.5 results, and subsequently tanned with 18% of the tanning agent described in Example 1, in the case of short-haired skins in a short liquor, in the case of long-haired skins in the usual liquor which should be as highly concentrated as possible and can be used for several batches.
• the skins are then neutralised in the usual manner, optionally, dyed, fat-liquored and further processed.
• the finished dressed skins are characterised by an excellent tear resistance, fastness to wet processing, perspiration and light, they are very soft and of good handle.
• Kid pelts are pickled in the customary manner so that a final pH-value of about 2.5 to 3 results, and subsequently tanned with 12% (referred to the weight of the pelts) of the tanning agent described in Example 1, and according to the method given in Example 1.
• the leather is retanned with 25% (referred to the weight of the shaved material) of 33% basic technical chromium sulfate having a chromium oxide content of
• the tanned leather is than neutralised in usual manner, dyed, fat-liquored and finished.
• the leather obtained is distinguished by a level and brilliant shade and by fine and firm grain and good handle.
• EXAMPLE 16 Preparation of white leather Cow, calf, goat or sheep pelts are pickled in the customary manner so that a final pH-value of between 2.5-3.5 results.
• the liquor is than drained and the pickled material tanned with a mixture of 12% (referred to the weight of the pelts) of the tanning agent described in Example 1.
• a powdered, not astringent, lightfast auxiliary tanning agent e.g., as described in Example 1 and prepared by condensing 1 mol of dihydroxydiphenylsulphone, 22.5 mols of formaldehyde and 1-1.25 mols of sodium sulfit), sluried with the same amount of water; the tanning is continued until the leather is completely tanned through, which lasts l4 hours, depending 8 on the thickness of the pelts.
• the further treatment of the tanned leather is carried out as mentioned in Example 1.
• the leather obtained is distinguished by its good white colour, the excellent plumpness and softness.
• EXAMPLE 17 Production of shrunk leather with White cross section of the leather Completely delimed and well tawed cow, calf, goat or sheep pelts are well drained and drummed with 100% of water and 6% of sodium chloride for 5 minutes. 5-10% of a powdered, astringent, lightfast syntan (e.g., that described in Example 2 and prepared by condensation of 1 mol of dihydroxydiphenylsulphone, 22.5 mols of formaldehyde and 14.25 mols of sodium 'sulphite) are added. Before adding the syntan it is dissolved in three times the amount of water and 20% of its Weight of formic acid.
• a powdered, astringent, lightfast syntan e.g., that described in Example 2 and prepared by condensation of 1 mol of dihydroxydiphenylsulphone, 22.5 mols of formaldehyde and 14.25 mols of sodium 'sulphite
• the leather is distinguished by its white colour, a thin shrunk grain, as well as its softness and plumpness.
• metal salts are the sulphates of zicronium, aluminum, and chromium.
• pretanned chrome leather is retanned with said combination of the salts of zicronium, aluminum, and chromium.

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• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Treatment And Processing Of Natural Fur Or Leather (AREA)

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• 1965
  • 1965-03-26 DE DEF45647A patent/DE1257353B/de active Pending
  • 1965-10-28 FR FR36449A patent/FR1451814A/fr not_active Expired
  • 1965-10-29 BE BE671639D patent/BE671639A/xx unknown
• 1966
  • 1966-02-22 CH CH251866A patent/CH473896A/de not_active IP Right Cessation
  • 1966-03-21 US US535721A patent/US3423162A/en not_active Expired - Lifetime
  • 1966-03-25 GB GB13314/66A patent/GB1081648A/en not_active Expired
  • 1966-03-25 NL NL666603974A patent/NL143277B/xx unknown
  • 1966-03-25 ES ES0324715A patent/ES324715A1/es not_active Expired

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