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
• • 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
  • C14C9/00—Impregnating leather for preserving, waterproofing, making resistant to heat or similar purposes

Definitions

• the present invention relates to a method for the preservation of leather semi-finished products and a correspondingly preserved leather semi-finished product.
• Rawhide as well as pre- and intermediate stages of leather production ie leather semi-finished products, such as wet-white or wet-blue material, are exposed to attacks by microorganisms. These attacks can lead to the destruction of the precursors of leather production.
• the preservative treatment using biocides is one way to prevent the growth of microorganisms.
• Canning is understood as meaning the improvement of the durability of a substance degradable by microorganisms, in particular of leather semi-finished products.
• the wet stages during leather production in the tannery are endangered by microorganisms and therefore require a preserving treatment.
• This treatment can in principle be carried out at any stage of leather production.
• the typical tanning process includes, among others, the steps of pimpling, chrome, vegetable or wet white tanning, blunting, greasing, coloring, wilting and trimming.
• biocides of the corresponding fleet can be added. This requires a high amount of biocide, since it is not completely absorbed by the leather semi-finished product. A large proportion of biocide remains in the fleet and is fed to the wastewater. The contamination of the waste water with biocide is a major disadvantage of this process.
• the addition to the liquor has the disadvantage that the Aufzieh and the distribution of the active ingredients is not very efficient.
• Biocides, or at least building blocks thereof are sensitive to nucleophiles and can be decomposed by them.
• the presence of nucleophiles in the liquor is unavoidable because nucleophiles (e.g., sulfides, amines, etc.) are transferred from fleet to liquor. This requires a high concentration of biocide in the fleet and a corresponding pollution of the wastewater by unincorporated biocide.
• Another problem is the presence of natural fats, which emulsify the active ingredients (biocides) and thus lead to an undesirable fate of the active ingredients in the fleet.
• the losses of active biocide can therefore be between 50-90% of the amount used, which is not only an economic problem, but also a potential toxicological problem, as the active ingredients get into the wastewater, which must be treated accordingly.
• the leather stock provided in step a) was not treated with a biocide in previous steps and especially in a previous treatment in the liquor.
• at least one biocide is applied to the leather semi-finished product in step b) of the present method.
• the Aufzieh and the distribution of biocides within the treated leather semi-finished product is very good and in particular more efficient than the addition of biocide in the fleet, as proposed in the prior art.
• the treatment is more economical. This is achieved through greater efficiency as well as improved control of the biocide content.
• unripened biocide can be specifically collected and reused, which is not possible when used in the fleet.
• the same applies to a subsequent wash cycle.
• the usual losses of biocide during treatment in the fleet 50 - 90% the amount used
• the pollution of the wastewater is drastically reduced.
• the composition of step b) contains microcapsules and the at least one biocide is encapsulated in these microcapsules and / or the at least one biocide is immobilized.
• the biocide may be prepared by lift or binding (adsorption) to an inert carrier material, such as e.g. Zeolites, to be immobilized.
• Leather semi-finished product is preferably understood to mean the nakedness which has undergone the basic operation of tanning. It is a finished intermediate and at the same time substrate of the inventive method.
• Leather semi-finished products (substrates), which are particularly suitable for this separate treatment step are already finished leather semi-finished or semi-finished leather products. In particular, it is hides or skins that are present in the wet "free-of-chrome" (wet-white) tanned, preferably in the wet, chrome-tanned (wet-blue) state.
• the leather semi-finished products are used in a dehydrated state.
• Dewatering of the leather semifinished product can be done by known methods, for example by wilting.
• a special Abwelkmaschine (sammying machine) is usually used; but this can also be done for example by means of a centrifuge.
• the water content of the leather semi-finished products, such as hides and skins is from 60-70% by weight to 50-65% by weight.
• the water content of the leather semifinished product after wilting in the dewatered state is 50-60 wt .-%.
• Other common mechanical operations that may occur on the semi-finished leather prior to application of the composition containing at least one biocide are splitting and leveling and stretching immediately after wilting.
• the semi-finished leather product was dehydrated prior to application of the composition in step b), wherein the water content of the leather semi-finished product is preferably 50-60 wt .-%.
• the leather semi-finished product of step a) is a wet-blue or wet-white material.
• biocides customary for the preservation of semi-finished leather biocides can be used as biocides.
• biocides contained in the composition of step b) selected from the group comprising OIT (2-n-octylisothiazolin-3-one), TCMTB (2-thiocyanatomethylbenzothiazole), OPP (ortho-phenylphenol), CMK ( Chloro-3-methylphenol, p-chloro-m-cresol), BCM (benzimidazolylcarbamic acid methyl ester), MBT (methylene bis-thiocyanate), p - [(diiodomethyl) sulfonyl] toluene, carbendazim (methyl-1H-benzimidazol-2-ylcarbamate ) or mixtures thereof. Mixtures of two or more than two different biocides may also be used.
• the proportion of biocide in the composition of step b) is preferably from 10% to 0.001% by weight, based on the total amount of the composition. In a further preferred embodiment, the proportion of biocide in the composition of step b) is preferably 5% by weight to 0.001% by weight, more preferably 2% by weight to 0.001% by weight and most preferably 1% by weight. % to 0.001% by weight, based on the total amount of the composition.
• the solvent used is preferably water in the composition.
• step b) 1 to 50 g of the composition per m 2 of semi-finished leather are applied.
• the amount of biocide used is preferably within the lowest and highest levels stated by the respective manufacturers. Surprisingly, the process according to the invention shows a very good uptake behavior of the biocide and, compared with the use in the Fleet according to the prior art, at the same time allows a very good distribution of the biocide, ensures a lower total amount of biocide sufficient preservation of leather semifinished products.
• biocide OIT 2-n-octylisothiazolin-3-one
• the composition of step b) can be prepared with a biocide solid or liquid at room temperature or from a formulation containing biocide.
• the composition may contain, besides the at least one biocide, other common ingredients. These are, for example, thickeners, defoamers, substances for adjusting the pH, fragrances, dispersants, coloring or discoloration-preventing substances, complexing agents and stabilizers.
• Commercially available biocides contain the respective biocide (s) in emulsified or dispersed form.
• the biocide is used in the commercial form without further additives. It may be diluted to the appropriate concentration of biocide in the composition of step b).
• the diluent used is preferably water.
• the composition of step b) contains microcapsules and the at least one biocide is encapsulated in these microcapsules and / or the at least one biocide is immobilized.
• the encapsulation of the at least one biocide can be carried out in a conventional manner known to the person skilled in the art, for example, as in Ullmann's Encyclopedia of Industrial Chemistry, 6th edition, 1999, Electronic Release, "Microencapsulation Suitable biocides in already immobilized or else encapsulated or encapsulated form are commercially available
• An encapsulation has the advantages that one can not come into direct contact with the biocides when the composition of step a) is prepared and the biocides themselves
• Another advantage of encapsulation is the protection against possible contact with nucleophiles delayed release of the biocide (s) due to the encapsulation, which is advantageous for the preservation of the leather semi-finished products.
• the leather semi-finished products are preferably used in a dehydrated state in step b), such as e.g. after wilting and, where appropriate, subsequent splitting and leveling.
• This has the advantage that the leather semi-finished products then have largely dehydrated surfaces. The inclusion of the biocide in the leather semi-finished product is thus improved.
• the application of the composition in step b) with the aid of an application unit to the preferably dewatered leather semi-finished products can take place by means of special coating techniques. During the coating, the composition is applied to the leather semifinished product and remains after the optional drying on this. This is independent of how pronounced the affinity between substrate surface and active ingredient is. After step c) drying, the now-preserved leather semi-finished product is storable and transportable.
• the application of the composition comprising biocide in step b) with the aid of a coating unit preferably takes place on both sides of the leather semifinished product.
• the application of the composition to the leather semi-finished product in step b) can be carried out by known techniques, such as by means of spraying, dipping or roller application.
• a dip application can, for example, be carried out mechanically in a first preferred embodiment in such a way that the composition is applied by means of a through-feed machine in which the leather semifinished product is first dewatered by means of rollers and then immersed in a bath containing the composition containing biocide.
• the leather semifinished product is then pressed out again (squeezed) by means of rollers, so that the unapplied residual amount of composition can be collected and optionally reused. This is not possible with the methods of the prior art.
• the application in step b) can be carried out mechanically such that the composition is first applied to one side of the leather semifinished product by means of a roll coater (reverse roll (er) coating machine).
• a roll coater reverse roll (er) coating machine
• the speed of a support roller (support roller) and the distance between metering and application roller (metering and application roller) can be adjusted so that a particularly effective application of the composition is made possible.
• the application of the composition can be repeated after turning the leather semi-finished product on the other side of the leather semi-finished product.
• Another object of the present invention is a preserved leather semi-finished product, which is obtainable by the aforementioned method.
• a 1% solution of the Biozidfomulierung Acticide ® WB 909 from Thor was applied in water to a leather semifinished product, the commercial product having a content of 9% of the active ingredient OIT.
• Various amounts were applied by means of a roll coater to a freshly prepared wet-blue with a thickness of 2.2 mm.
• the water content of the substrate was 60% after wilting.
• the weight of the dewatered material was about 2200 g / m 2 .
• Table 3 shows the amounts of active ingredient used and the respective determined active ingredient content after use in comparison between the application according to the invention by means of a roller applicator (Table 1, Sample 3) and by means of conventional barrel application (Table 2, Sample 8).

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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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Cited By (1)

Citations (4)

• 2011
  • 2011-02-11 EP EP11154100A patent/EP2487264A1/fr not_active Withdrawn

Patent Citations (4)

Non-Patent Citations (3)

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