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
  • C14C3/06—Mineral tanning using chromium compounds

Definitions

• the invention relates to a process for tanning skins with a highly basic chromium sulfate tanning agent which has a basicity of 57 to 63% and which can be masked by up to 10% by the rest of an organic acid, for tanning skins.
• a widespread tanning agent is, for example, a chromium III sulfate with 33% basicity, it also being possible to use chromium III sulfate; which are masked by formate residues, since a slightly higher basicity, up to 50%, can be achieved with these complexes.
• the basicity of the chromium salts indicates the mol-X of hydroxyl groups which are bonded to the trivalent chromium cation, 3-hydroxyl groups corresponding to a basicity of 100%.
• the old rule for practice is that for a quick tanning of hides the basicity should be low, for example at 33%, and an increase is only made in the course of the tanning process.
• Chrome tanning agents with a higher basicity are already available on the market. However, these are not uniform, but represent mixtures of low-basic chromium salts with, for example, dolomite, calcium carbonate and / or magnesium oxide. They are set so that the basicity increases during the tanning process.
• Lower alkane carboxylic acids in particular formic and acetic acid, but also dicarboxylic acids, such as adipic acid, and aromatic carboxylic acids, in particular phthalic acid, are suitable as organic acids or acid anions for the production of a masked, highly basic chromium sulfate.
• dicarboxylic acids such as adipic acid
• aromatic carboxylic acids in particular phthalic acid
• acetic acid and formic acid are particularly preferred.
• the invention precludes the general prejudice that chromium III sulfates with more than 50% basicity in tanning are not advantageously used that can be overcome.
• the surprising advantage of the method according to the invention is that, despite the high basicity, even thick skins can be tanned relatively quickly without difficulty and without special measures.
• the tanning agent to be used according to the invention can be prepared in a conventional manner by adjusting the basicity, for example using sodium hydroxide solution and, if appropriate, converting it with the appropriate masking agent in the form of the acid or a salt from a sulfuric acid chromium (III) salt solution.
• Such tanning agents can also be obtained, for example, from a by reducing chromate / dichromate solutions with sulfite or sulfur dioxide or another reducing agent, e.g. Methanol, obtained chromium III saline solution and appropriate adjustment with a base and masking agent.
• the basicity is set to about 60%, the degree of masking is about 5% and the chromium dioxide content, calculated on dry weight, is about 23-25%.
• chromium salt solutions prepared in the manner described above can easily be used as chromium tanning solutions. They can also be dried in a spray dryer or other dryer to a powder that is stable in storage and clearly soluble in water when used.
• a chromium sulfate tanning agent in powder form which can be used according to the invention and thus obtained contains 15 to 30% by weight of chromium oxide.
• the tanning according to the invention also takes place in the same way as has previously been done with conventional chromium salts.
• the procedure is generally such that a decalcified and pickled pelts are then in the same or a fresh liquor in an amount of 30 to 100%, based on the pelvis weight, with a chromium oxide range of 0.5 to 2.5, preferably 1 , 4 to 1.8 Gew.-X, based on the pelt weight, rolls for about 3 to 10 hours and then processed in the well-known manner.
• the chromium sulfate tanning agents to be used according to the invention can also be used in conjunction with other vegetable or synthetic tanning agents like the previous chrome tanning agents. They can also be modified, for example in accordance with DE-AS 23 34 636, with water-soluble mono- or polyglycols.
• the process with the highly basic salts enables a simplified and safe guidance of the chrome tanning with at the same time good chrome absorption and chrome fixation, due to the fact that in comparison to the conventional tanning agents drive the opportunity to reduce the amount of chromium oxide offered without reducing the chromium oxide content in the finished leather.

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 (1)

Family

ID=6191660

Family Applications (1)

Country Status (4)

Cited By (2)

Citations (4)

• 1983
  • 1983-02-24 DE DE19833306374 patent/DE3306374A1/de not_active Withdrawn
• 1984
  • 1984-02-16 EP EP84101626A patent/EP0121697A1/de not_active Withdrawn
  • 1984-02-21 JP JP2969184A patent/JPS59159900A/ja active Pending
  • 1984-02-23 ES ES529988A patent/ES8501000A1/es not_active Expired

Patent Citations (4)

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