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
  • C14C1/00—Chemical treatment prior to tanning
  • C14C1/08—Deliming; Bating; Pickling; Degreasing

Definitions

• the peeling material is tanned with standard chrome (III) salts after picking. After mechanical dewatering and possible splitting, the resulting wet blue is folded to the desired thickness.
• the chrome leather produced with the help of the substances described above differs significantly in leather character in terms of handle (see, for example, Das Leder 37 (1986) 12, 221-224), fullness, softness and dyeability from conventionally chrome-tanned and folded leather. Experience has shown that such serious deviations in the property profile are not tolerated by the leather manufacturer and / or processor.
• a pretreatment can also be carried out using special non-tanning condensation products which give a substrate which can be machine-dewatered and folded or split or folded without problems.
• the skin material pretreated in this way can be stored indefinitely after appropriate preservation under normal conditions.
• the resulting leather after chrome tanning does not differ in its application properties from conventionally chrome-tanned and folded leather.
• the invention thus relates to a process for the production of chrome leather, characterized in that the descaled, pickled and pickled skin material in the usual manner is pretreated in an aqueous liquor with a non-tanning condensation product and folded or, after mechanical dewatering, split and folded (in the case of uncleaved pelt material) and then chrome-tanned with commercially available chromium (III) salts and, as usual, post-treated.
• the usual aftertreatment generally includes neutralization, retanning, coloring and oiling.
• the pretreatment agents used according to the invention are condensation products of aromatic sulfonic acids which do not contain any phenolic hydroxyl groups, e.g. those of C6-C24 aromatics such as naphthalene, or the diaryl ether, e.g. the ditolyl ether, preferably the ⁇ -naphthalenesulfonic acid, with formaldehyde.
• Aromatic sulfonic acids preferred for the condensation contain 0.8 to 3, preferably 1 to 2 sulfonic acid groups per molecule,
• condensation products to be used according to the invention is described below using the example of ⁇ -naphthalenesulfonic acid / formaldehyde: 1.1 to 1.8, preferably 1.4 to 1.5 mol of 100% sulfuric acid can be used per mole of naphthalene.
• the sulfonation is generally carried out at temperatures from 120 to 160, preferably 140 to 150 ° C; it is usually completed within 1 to 3 hours.
• 0.4 to 0.8, preferably 0.55 to 0.65, mol of formaldehyde are added (mostly in the form of its aqueous solution).
• the condensation can take place at temperatures from 95 to 120 ° C, preferably from 110 to 120 ° C; it is usually completed within 2 to 5 hours.
• the mixture is neutralized to a pH of 5 to 8, preferably 6 to 6.5, with alkali metal hydroxide solution or to a pH of 2 to 5, preferably 3 to 3.5, using ammonia.
• these products are adjusted to an acid number (mgKOH / g) of 20 to 60 with 1 to 8, preferably 3 to 4% by weight, based on the condensation product, of C4-C8-dicarboxylic acid (for example glutaric acid).
• the condensation products used according to the invention have no sole genetic action (Bibliothek des Leders, Vol. 3, p. 65, Umschau-Verlag, Frankfurt / Main, 1st ed. 1985) in the sense of a covalent collagen crosslinking, as is the case, for example, with polyfunctional aldehydes and isocyanates or in Collagen cross-linking by hydrogen bonding with phenol-containing exchange / vegetable tannins or in the sense of collagen cross-linking by complex formation of mineral tannins.
• shrinkage temperatures of less than 65 ° C. are achieved. At the same time, however, they cause extremely strong drainage of the skin material on the wilting machine and enable problem-free mechanical folding without any signs of burns.
• the fold thickness of the skin material pretreated in this way corresponds to the thickness of the chrome-tanned finished leather and makes additional folding unnecessary.
• Another advantage is that the timing of this wet white process largely corresponds to the production rhythm of conventional chrome leather production.
• the pestle material obtained by customary soaking and liming is descaled in the usual way, pickled and with pH values of organic and / or inorganic acids 2 to 6, preferably 2.5 to 4.5 set (pounded).
• the pretreatment is then carried out with 3 to 15, preferably 4 to 8% by weight (based on the pelt weight) of the above-mentioned condensation products, calculated as a solid.
• the skins pretreated in this way can be folded perfectly or, in the case of uncleaved nakedness, split and folded.
• the skins are then chrome-tanned with commercially available chromium (III) salts and finished in the usual way.
• the finished leather obtained by the process according to the invention has no differences in the property profile compared to conventionally produced chrome leather.
• the leathers can be dyed brilliantly and are therefore particularly suitable for the production of high-quality aniline leathers for processing into furniture, shoe upper and clothing leathers.
• the shavings obtained by the process according to the invention are chromium-free and offer various options for disposal.
• condensation products used according to the invention can be used in spray-dried form or as an aqueous solution.
• dilution ratios mentioned in the following examples relate to parts by weight, the larger number in each case meaning the parts of water.
• the concentrations of the acids to be diluted correspond to the usual practice: formic acid 85%, sulfuric acid 96%.
• naphthalene 1 mol of naphthalene is sulfonated with 1.43 mol of 100% sulfuric acid at 145 ° C for 3 hours.
• the sulfonation mixture is allowed to cool somewhat and is condensed for 3 hours at 115-117 ° C. with 0.64 mol of formaldehyde, which is used in the form of its 30% strength aqueous solution.
• the reaction mixture is then allowed to cool to 80 ° C. and aqueous ammonia is then added to a pH of 3.5.
• 4%, based on the resulting ammonium salt of the condensation product, of glutaric acid are added to this solution and an acid number of 35 is thus obtained.
• the product is preferably spray-dried, but can also be used as a 40-60% strength aqueous solution.
• washed 800 kg of beef pelts (split by 2 mm) in the tanning drum are first washed with 100% (based on pelt weight; like all the following% data) water at 35 ° C. for 15 minutes.
• the fleet is drained and then is without liquor, decalcified for 45 minutes with 1.3% ammonium chloride and 0.4% citric acid, 80% water at 35 ° C was added and pickled with 0.2% of a commercial pickling agent (with 1500 tryptic units) for 120 minutes (pH value of the liquor 7.7).
• the cross-section of the nakedness no longer gives a red color with phenolphthalein. It is then washed with 100% water at 25 ° C.
• the wet whites are unloaded, wilted and, if necessary, folded to 1.0 mm thickness after 24 hours of intermediate storage. About 30 kg of chromium- free shavings are obtained per 100 kg of bare material used.
• chromium-syntan complex commercially available chromium-containing synthetic retanning agent with 12% chromium (III) oxide
• the remaining liquor has a chromium (III) oxide content of 1.8 g / l, a final pH of 3.3 and a final temperature of 35 ° C.
• the mixture is then neutralized to pH 6.5 in the usual way, greased and finished by intermediate drying.
• the descaled, pickled and pickled pelts (slit thickness 2 mm) in Example 1a) are mixed in the pickling liquor with 2.3% (based on pelt weight, like all the following% data) of a commercially available synthetic fat, and after 15 minutes 9% a commercially available, slightly organically masked chromium (III) sulfate solution with 15% chromium (III) oxide and 40% basicity (according to Schorlemmer) was added. After a running time of 90 minutes, 0.35% magnesium oxide is added and the process is continued for 10 hours. The final pH is 3.8 and the final temperature is 38 ° C. The chromium oxide (III) content of the remaining liquor is 5.9 g / l.
• the resulting wet blues (with approx. 3.8% chromium (III) oxide, based on anhydrous wet blue) are wilted and folded to a thickness of 1.0 mm.
• the folded wet blues have the same chromium (III) oxide content as that in example 1a) after the chrome-tanned wet whites.
• About 28 kg of chrome shavings with about 3.8% chromium (III) oxide, based on anhydrous chrome shavings, are obtained per 100 kg of bare material used.
• the mixture is then neutralized to pH 6.5 in the usual way, greased and finished by intermediate drying.
• Example 1a To produce furniture leather, the wet white leather produced in Example 1a) is wilted and folded. 100 kg of folded wet whites in 250% water (based on shaved weight; like all the following% data) are mixed with 1.5% of a commercially available synthetic fat and drummed for 15 minutes. Then 0.4% formic acid (diluted 1:10 with water) and after 45 minutes 7% of a commercially available chrome tanning agent with 26% chromium (III) oxide and 33% basicity (according to Schorlemmer) are added. After a further 15 minutes of running time, 3% fat is added (see above).
• the mixture is then neutralized to pH 6.5 in the usual way, greased and finished by intermediate drying.
• Example 1a After 24 hours, the wet whites are folded to a thickness of 1 mm and processed as in Example 1a). However, care must be taken here that the pH in the chrome tanning is increased to approximately 3.5 by adding 1.1% (instead of 0.9%) of sodium bicarbonate.
• Example 4 100 kg of beef peat pretreated as in Example 4 are diluted with 0.5% formic acid (1:10 with water) and 0.6% sulfuric acid (diluted 1:10 with water) (pimple pH 3.2). The pretreatment is carried out with 17% of an aqueous solution (50%) of the condensation product to be used according to the invention. The wet whites are then wilted, split and folded as in Example 4 and processed as in Example 2.
• condensation product 6% of the condensation product to be used according to the invention and 0.1% are now added to the pickling liquor Sodium bisulfite (for H2S elimination) added. After one hour, 1% of a commercially available natural fat (oil product) is added and the product is walked on for 12 hours.
• the final pH is 3.2 and the final temperature is 31 ° C.
• the wet whites are unloaded, wilted and, if necessary, folded to 1.8 mm thickness after 24 hours of intermediate storage. Approx. 36 kg of chrome-free shavings are obtained per 100 kg of bare material used.
• the mixture is then neutralized to pH 4.7 with 1.5% of a commercially available neutralizing tanning agent and 0.5% sodium bicarbonate, and the liquor is drained off after 45 minutes.
• the neutralized Chrome leather is retanned in the usual way (with a combination of exchange, resin or polymer and vegetable tannins), dyed and greased.
• condensation product to be used according to the invention 4% of the condensation product to be used according to the invention is added to the pickle liquor. After 30 minutes, 0.5% of a commercially available synthetic exchange tanning agent based on bis (4-hydroxyphenyl) sulfone is added. After a further 60 minutes, 1.5% of a commercially available synthetic fat is added and the process is continued for 12 hours.
• the final pH is 3.5 and the final temperature is 33 ° C.
• Example 1 After draining the remaining liquor, the wet whites are unloaded, wilted and folded, chrome-tanned and finished as in Example 1.

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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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• 1991
  • 1991-09-19 DE DE4131202A patent/DE4131202A1/de not_active Withdrawn
• 1992
  • 1992-09-07 EP EP92115270A patent/EP0533011B1/fr not_active Expired - Lifetime
  • 1992-09-07 ES ES92115270T patent/ES2063559T3/es not_active Expired - Lifetime
  • 1992-09-07 DE DE59200623T patent/DE59200623D1/de not_active Expired - Fee Related
  • 1992-09-09 US US07/942,651 patent/US5340365A/en not_active Expired - Fee Related
  • 1992-09-16 CA CA002078411A patent/CA2078411A1/fr not_active Abandoned
  • 1992-09-17 JP JP4272500A patent/JP3027480B2/ja not_active Expired - Lifetime

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