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
• • 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
  • C14C3/28—Multi-step processes

Definitions

• the present invention relates to a process for retanning (post-chrome plating) chrome leather, in which chrome (III) salts are used and a very high chromium consumption of the liquor is achieved.
• the chrome leathers are washed, treated with a chromium (III) salt, possibly in the presence of a syntan, and then in a new or the same liquor with the known acid-binding agents such as sodium or ammonium bicarbonate, sodium formate and others pH values between 4 and 7, depending on the type of leather.
• a chromium (III) salt possibly in the presence of a syntan
• the known acid-binding agents such as sodium or ammonium bicarbonate, sodium formate and others pH values between 4 and 7, depending on the type of leather.
• the chrome tanning agent offered is often fixed by the leather.
• a further part of the unbound chromium is removed from the leather (see S.C. O'Connor, The Leather Manufacturer 1984, 8, 20-29).
• the retanning is expediently carried out in the case of liquor lengths of over 100% (based on the fold weight) and liquor temperatures of 35-55 ° C. over a period of 1.5 to 4 Hours at final pH values above 4.0.
• the Cr 2 0 3 range is 0.3-1.0% (based on shaved weight), preferably 0.4 - 0.6% (based on shaved weight).
• Suitable chromium (III) salts for retanning are the usual chromium (III) salts which can be used for chromium tanning, in particular chromium (III) sulfates, basic chromium (III) sulfates, furthermore with organic acids, for example formic acid or Acetic acid, masked chromium (III) salts, chromium tanning agents which, in addition to chromium (III) salts, also contain inorganic salts, such as sodium sulfate, or reaction products of hexavalent chromium compounds with reducing agents.
• chromium (III) salts which can be used for chromium tanning, in particular chromium (III) sulfates, basic chromium (III) sulfates, furthermore with organic acids, for example formic acid or Acetic acid, masked chromium (III) salts, chromium tanning agents which, in addition to chromium
• Aliphatic dicarboxylic acids with 4 to 6 carbon atoms are, for example, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, aspartic acid, glutamic acid or mixtures thereof. Glutaric acid and adipic acid or mixtures of these acids, if appropriate with other dicarboxylic acids, are preferably used.
• Aliphatic dicarboxylic acids with 4 to 6 carbon atoms which contain a hydroxy group alpha to the carboxyl group and / or the sulfonic acid groups, should only be used up to about 1/3 of the total amount of dicarboxylic acid used.
• Aromatic dicarboxylic acids with 8 to 12 carbon atoms are those of the benzene and naphthalene series which, in addition to the carboxyl groups, also contain hydroxyl, amino or nitro groups and / or may contain halogen atoms. Phthalic acid and isophthalic acid are preferably used.
• the carboxylic acids can be used both in the form of free acids, in the form of mixtures of the free acids and the salts of such carboxylic acids, and alone in the form of the salts, advantageously the alkali metal salts.
• Suitable syntans are, for example, naphthalenesulfonic acid-formaldehyde, diaryl ether sulfonic acid-formaldehyde, polyphenylsulfonic acid-formaldehyde, phenolsulfonic acid-formaldehyde, naphthalenesulfonic acid-4,4'-dihydroxydiphenylsulfone-formaldehyde condensates, polyphenylsulfonic acids and their lignin sulfonic acids.
• Protein hydrolyzates are also suitable as synthetic organic tanning agents (see K. Faber, Library of Leather, Volume 3, Umschau-Verlag, Franktfurt am Main, p. 236).
• Dicyandiamide-formaldehyde condensates and mixtures thereof with anionic dispersants are preferred based on lignin sulfonate or naphthalene sulfonic acid.
• alkali or ammonium carbonates and magnesium oxide are suitable as deadening agents.
• Magnesium oxide or sodium bicarbonate or mixtures thereof are preferably used.
• MgC0 3 which has a content of 20-40 X CaO, preferably 25-35 X Ca0 and an MgO content of 10-25%, preferably 16-24% MgO, understood.
• calcium carbonate and / or dolomite and the other dulling agents depend on the basicity of the chromium salts used and the degree of neutralization of the dicarboxylic acids used. They are to be dimensioned such that, taking into account the dicarboxylic acids or their salts, the calcium carbonate and / or dolomite and the other deadening agents, the resulting theoretical basicity of the chromium salt is 80-120%.
• the wet blues which have been chrome-tanned, withered and folded in the usual manner are preferably retanned in the manner described without prior washing.
• the leather can be dulled if necessary by adding deacidifying agents in the same or in a new liquor. They are then dyed in the usual way, possibly retanned with vegetable tannins and / or syntans, greased etc.
• the value of the process consists in the fact that, with a very simple method of working, it leads to leather of all colors, full, soft, fine-grain and grain-resistant, and at the same time high chrome depletion of the retanning brisk.
• the residual liquors have, depending on the liquor length, duration and temperature of chromium oxide of less than 0.5 g Cr 2 0. 3/1
• the chrome-syntan mixed tanning agent used has the following composition.
• the Cr 2 0 3 content of the retanning liquor is 0.1 g / l.
• the leathers obtained are identical to those produced according to Example 1.
• the syntan part of the mixed tanning agent consists of 140 parts by weight. of a commercial auxiliary tanning agent based on ditolyl ether sulfonic acid.
• the leathers have a somewhat lighter color than those produced according to Example 1. Otherwise, they are comparable in all properties.
• composition (in parts by weight):
• composition in parts by weight
• Example 1 Retanning as in Example 1. Instead of 0.5% (based on the chromium oxide content of the mixed product), 0.6% (based on chromium oxide content of the mixed product) are offered.
• the leather has a deeper color than that obtained in Example 1.
• Furniture leather is obtained which is characterized by a soft, full handle, a level, deep color and a fine mill grain.
• the final pH of the retanning liquor is 4.9 and the Cr 2 0 3 content is 0.2 gll.

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)

Applications Claiming Priority (2)

Publications (2)

Family

ID=6271940

Family Applications (1)

Country Status (7)

Cited By (1)

Citations (4)

• 1985
  • 1985-05-30 DE DE19853519287 patent/DE3519287A1/de not_active Withdrawn
• 1986
  • 1986-05-21 DE DE8686106874T patent/DE3660208D1/de not_active Expired
  • 1986-05-21 EP EP86106874A patent/EP0204213B1/fr not_active Expired
  • 1986-05-26 JP JP61119392A patent/JPS61278599A/ja active Granted
  • 1986-05-28 CA CA000510138A patent/CA1275755C/fr not_active Expired - Lifetime
  • 1986-05-29 ZA ZA864008A patent/ZA864008B/xx unknown
  • 1986-05-30 ES ES555543A patent/ES8707767A1/es not_active Expired
• 1988
  • 1988-04-22 US US07/185,198 patent/US4834763A/en not_active Expired - Lifetime

Patent Citations (4)

Non-Patent Citations (1)

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