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
  • C14C1/08—Deliming; Bating; Pickling; Degreasing
• • 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

• Chrome tanning is an essential step in leather production.
• chromium salts are offered in a concentration which corresponds to an equivalent of 2 to 2.5% by weight of Cr 2 O 3, based on nakedness, in order to achieve a cookable leather. Of these, however, only 70 to 80% are actually permanently fixed in the skin, so that 20 to 30% of the chromium tannin offered ends up in the wastewater.
• the degree of exhaustion of the chrome tanning agents can be improved beyond the usual level.
• the increased astringency of the chrome tanning agents leads to scarring i.e. lower quality leathers. In most cases, a loss of space also has to be accepted.
• aromatic di- and tricarboxylic acids such as phthalic acid and / or their salts
• aromatic di- and tricarboxylic acids are used in the pimple or in the chrome tanning in order to achieve better fixation of the chromium in the skin. If they are used in the pimple, however, this leads to a significant reduction in the penetration rate of the subsequent chrome tanning agents, an uneven chrome distribution and, in the case of stronger, unsplit nakedness, even insufficient tanning in some cases.
• tanning must usually be carried out in two stages in order to reduce these deficiencies by using mild organic tanning which is carried out with mostly organically masked chromium (III) sulfate tanning agent and then adding the aromatic di- and tricarboxylic acids follow alone or in the presence of further chrome tanning agent and / or a base agent.
• mild organic tanning which is carried out with mostly organically masked chromium (III) sulfate tanning agent and then adding the aromatic di- and tricarboxylic acids follow alone or in the presence of further chrome tanning agent and / or a base agent.
• chrome-saving tanning process US Pat. No. 4,715,861 in which 0.1 to 2% by weight of an aldehyde or keto carboxylic acid, preferably glyoxylic acid, is used as a replacement or partial substitute for the sulfuric acid or formic acid usually used before tanning in the pimple bath will.
• the chrome tanning is carried out in the same bath. This process results in very soft leather with tightly fitting scars and improved physical properties. The consumption of the chrome tanning liquor is improved significantly, but without meeting the increased demands in all cases.
• chromium tanning process with high exhaustion uses chromium (III) salts which are tanned with 0.5 to 12% by weight, preferably 3 to 6% by weight, based on the pelt weight Peel, a combination of basifying agents such as magnesium oxide and aldehyde and / or ketocarboxylic acids and subsequent addition of sodium aluminum silicates.
• the pelts are tanned with 0.5 to 2.0% by weight of an aldehyde or keto carboxylic acid, preferably glyoxylic acid and 0.5 to 1.0% by weight of one, before tanning Mixture of chromium (III) salts, acid-binding agents and aromatic di- and tricarboxylic acids pretreated. Thereafter, tanning is carried out in the same bath in the customary manner and then tanned with 1 to 3% by weight of a mixture of chromium (III) salts, acid-binding agents and aromatic di- or tricarboxylic acids or their salts.
• the object of the invention is to provide a chrome tanning process which does not have the aforementioned disadvantages and which, in addition to improved chromium exhaustion of the tanning liquor, guarantees greater abundance, better softness and grain resistance of the leather.
• the invention relates to a process for chrome tanning and chrome fill tanning, in which the pelts in the pimple bath are mixed with an aldehyde and / or ketocarboxylic acid and then tanned, characterized in that before the addition of the aldehyde and / or ketocarboxylic acid and optionally other organic and / or inorganic acids, the decalcified and pickled pelts are pretreated with an anionic, colloidal silicate solution.
• Anionic colloidal silicate solutions are usually aqueous dispersions of colloidally distributed, anionically charged silicon dioxide particles, preferably so-called silica sols.
• the aqueous dispersions are usually prepared by "in situ" growth of silicon dioxide micro-nuclei and not by redispersion of particles which have already formed.
• the silicon dioxide particles produced in this way are non-porous and amorphous.
• dispersions of different particle size or different specific surface can be produced.
• the dispersions are stabilized with organic or inorganic bases, such as ammonia, amines, for example ethanolamines, and sodium, potassium or lithium hydroxide.
• the silicon dioxide particles usually have a particle size between 5 and 135 nm, preferably 5 to 25 nm and a specific surface area between 50 and 500 m2 / g, preferably between 100 and 150 m2 / g.
• the pH of the dispersion is generally between 5 and 10.
• the aqueous dispersions of colloidally distributed, anionically charged silicon dioxide particles preferably include so-called silica sols, as are known from Ralph K. Iler, The Chemistry of Silicium, John Wiley and Sons, New York 1979. The manufacture and properties of these silica sols are discussed in Chapter 4, pages 312 to 461.
• silica sols are available under the name ®Klebosol (trademark of governing civile Hoechst) and are described in the brochure of cioslaube Hoechst "Klebosol, sols de silice-silicasols-Kieselsole".
• Anionic colloidal silicate solutions are generally 5 to 65% by weight, preferably 20 to 40% by weight, aqueous dispersions of colloidally distributed, anionically charged silicon dioxide particles.
• the decalcified and pickled pelts are preferably 0.3 to 5.0% by weight, particularly preferably 0.3 to 0.6% by weight, of an anionic, colloidal silicate solution, based on the weight of the Bare, pretreated.
• the pH is then adjusted to a pH of less than 6, preferably 2.8 to 4.3, by adding an aldehyde and / or ketocarboxylic acid, preferably glyoxylic acid or pyruvic acid and optionally other organic and / or inorganic acids.
• an aldehyde and / or ketocarboxylic acid preferably glyoxylic acid or pyruvic acid and optionally other organic and / or inorganic acids.
• the addition of 0.25 to 2.5% by weight of the aldehyde and / or keto carboxylic acid, based on the pimple weight of the pimple, is usually sufficient for this.
• Glyoxylic acid is preferably used alone or in combination with other organic and / or inorganic acids, such as formic acid and sulfuric acid.
• the tanning is then carried out in the same bath with the customary commercially available chromium (III) tannins, whereby the modern, self-dulling chromium (III) tannins can also be used without any problems.
• colloidal silicate solutions with a particle size of 5 to 25 nm are combined with those between 26 and 135 nm and glyoxylic acid in the pimple, a "wet white” is obtained which is easily subjected to the mechanical processes of splitting or folding (splitting waste and folding waste are Aldehyde, chrome and aluminum free; they can be recycled or disposed of in an environmentally friendly manner and then tanned with chrome tanning agents (or other tanning agents).
• chrome tanning agents or other tanning agents.
• the character of the chrome leather is not affected by the pretreatment.
• the residual chromium content of the exhausted tanning liquors is less than 100 mg Cr2O3 per liter.
• the process according to the invention is distinguished by the very high degree of exhaustion of the chrome tanning agents.
• the residual chromium content of the exhausted tanning liquors is less than 200 mg Cr2O3 per liter.
• the wet blue produced is particularly full, soft and strikingly bright.
• the bright wet blue color does not have a negative effect on the color build-up in the subsequent dyeing. Due to the fullness and softness already achieved in the tanning process, the retanning and fat supply in the wet finish can be significantly reduced.

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• 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)

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• 1993
  • 1993-08-05 EP EP93112579A patent/EP0583697A2/de not_active Withdrawn
  • 1993-08-07 TW TW082106335A patent/TW248571B/zh active
  • 1993-08-11 JP JP5199649A patent/JPH06166900A/ja not_active Withdrawn
  • 1993-08-12 KR KR1019930015599A patent/KR940004061A/ko not_active Application Discontinuation
  • 1993-08-12 US US08/105,380 patent/US5501709A/en not_active Expired - Fee Related
  • 1993-08-13 CN CN93116221A patent/CN1082613A/zh active Pending
  • 1993-08-13 ZA ZA935923A patent/ZA935923B/xx unknown
  • 1993-08-13 BR BR9303380A patent/BR9303380A/pt not_active Application Discontinuation
  • 1993-08-13 AU AU44590/93A patent/AU4459093A/en not_active Abandoned

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