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
  • C14C3/28—Multi-step processes
• • 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
  • C14C3/08—Chemical tanning by organic agents
  • C14C3/22—Chemical tanning by organic agents using polymerisation products

Definitions

• the main tanning is usually carried out with mineral tanning agents, such as basic chromium, aluminum and / or zirconium salts, alone or in combination with synthetic tanning agents.
• mineral tanning agents such as basic chromium, aluminum and / or zirconium salts
• synthetic tanning agents serve to improve the sensory properties of the leather, such as feel, softness, grain and fullness. So it is not a tanning in the strict sense of the word, i. H. there is generally no marked increase in the shrinkage temperature of the leather.
• syntans i.e. water-soluble condensation products from e.g. B.
• naphthalenesulfonic acid and formaldehyde or from phenolsulfonic acid, formaldehyde and urea also lignosulfonic acids and, for some years now, water-soluble polymers and copolymers based on acrylic acid and other unsaturated polymerizable carboxylic acids, generally in combination with the aforementioned syntans. They are all anionic in character, which means that the dyeings are lightened to a greater or lesser extent with the usual anionic dyes.
• Tanning agents according to DE-A-28 43 233 offer progress in this regard, in which, in contrast to conventional syntans, small amounts of aromatic amines are condensed. Although these products give the leather good coloring properties when used alone for retanning, they are not able to deepen the coloration of leather that has been retanned with conventional syntans. In addition, their filling effect is less than that of commercially available polymer tanning agents based on acrylic acid or methacrylic acid.
• DE-A-2 127 959 describes polyampholytic resins with a ratio of carboxyl to amino groups of 97.5: 2.5 to 35: 45.
• Basic amino esters preferably dimethylaminoethyl methacrylate, emerge in particular as monomers containing amino groups.
• the basic esters have the disadvantage that they are sensitive to hydrolysis, and the coloring properties of a leather treated with such a polymer tanning agent leave something to be desired.
• the invention was therefore based on the object of developing a tanning process which avoids these disadvantages, i. H. that gives the leather favorable coloring properties and a good fullness even when anionic tanning and retanning agents are used.
• the polymer tanning agent to be used according to the invention must be water-soluble, i.e. H. at least 2, preferably at least 10% by weight aqueous solutions should be prepared under the conditions usually present during retanning (pH 3.5 to 6, preferably 4 to 5.5; temperature 10 to 70, preferably 30 to 45 ° C.) be.
• the polymer does not necessarily have to be completely genuine (clear) in this case, a colloidal (ie more or less cloudy) solution is also sufficient. Real solutions are preferred.
• the amount of polymer tanning agent used is 0.025 to 2.5, preferably 0.25 to 1.6%, based on the shaved weight.
• carboxyl groups Depending on the pH, a more or less large part of the carboxyl groups is present in salt form in aqueous solution.
• the type of cation is practically irrelevant; the most common are sodium, potassium and especially ammonium ions.
• ammonium ions are mono-, di- and trialkylammonium ions with 1 to 6 carbon atoms in the alkyl radical.
• the polymer tanning agent to be used according to the invention is obtained in the usual way by copolymerization in aqueous or organic solution, in dispersion or in bulk with the customary free radical initiators (for example peroxides, azodiisobutyronitrile).
• the customary free radical initiators for example peroxides, azodiisobutyronitrile.
• the polymer has a K value according to Fikentscher (Cellulose-Chemie 13, 1932, pages 58 to 64 and 71 to 74), measured in dimethylformamide, from 15 to 80, preferably 20 to 60. The measurement is carried out at 60 ° C. in one Mixture of 60 parts of dimethylformamide and 40 parts of glacial acetic acid at a concentration of 1 g / 100 ml.
• Fikentscher Cellulose-Chemie 13, 1932, pages 58 to 64 and 71 to 74
• the number ratio of amino to acid groups in the polymer tanning agent according to the invention should be 1:20 to 17:20, preferably 1: 8 to 1: 2, and the carboxyl group content should be 6 to 40, preferably 12 to 30% by weight of the total Polymers.
• the term «carboxyl groups is also intended to include carboxylate groups here.
• the retanning according to the invention can be carried out separately in a separate operation or together with the coloring and oiling. As mentioned, it is possible and even preferred to combine them with a conventional retanning, ie with anionic retanning agents, or to connect them to it.
• the polymer tanning agents to be used according to the invention impart not only a good fullness but above all good coloring properties to the leather.
• polymeric tanning agents are usually used in combination with syntans. As a rule, it is observed that this combination lightens the color even more than the use of syntan alone.
• the polymeric tanning agents according to the invention do not have this disadvantage, depending on the type of monomer containing amino groups used, a more or less significant color deepening compared to the coloring of the leather which has only been treated with syntans, can be enough.
• the polymer tanning agents according to the invention are surprisingly clearly superior to the syntans containing amino groups known from DE-A-28 43 233. This is particularly surprising because the number of carboxyl groups in the polymer tanning agent according to the invention exceeds that of the amino groups. In addition, there is usually a better filling effect and better light fastness.
• the starting materials mentioned in the examples, apart from the polymer tanning agents according to the invention, are commercially available.
• the polymerizations were carried out under a protective gas atmosphere (nitrogen).
• the solution obtained was used for retanning in the following way: First, 100 parts of seam-damp chrome cowhide were deacidified in 100 parts of water at 30 ° C. with 1 part of sodium formate and 0.4 part of sodium hydrogen carbonate. The mixture was then drummed in 100 parts of fresh, aqueous liquor at a temperature of 40 ° C. first with 1 part of a commercially available neutralized dyeing aid based on phenolsulfonic acid for 20 minutes, after which 7 parts of tannin solution were added. After drumming for a further 40 minutes, 4 parts of a commercially available full tanning agent based on phenol were added to the liquor and drumming for a further 60 minutes. Then 1 part of the Acid Brown 161 dye was added. After drumming for a further 30 minutes, 6 parts of a commercially available fat licker based on natural fat were used for greasing. Finally, 1 part of formic acid was acidified.
• a second leather was regged, dyed and greased in exactly the same way, except that instead of the retanning agent to be used according to the invention, a commercially available polymeric tanning agent based on acrylic acid / acrylonitrile was used.
• the leather treated according to the invention was dyed significantly deeper.
• the solution obtained was used for retanning as follows: First, 100 parts of seam-damp chrome cowhide were deacidified in 100 parts of water at 30 ° C. with 1 part of sodium formate and 0.3 part of sodium hydrogen carbonate. Subsequently, in 100 parts of fresh, aqueous liquor, it was first tumbled for 20 minutes at a temperature of 40 ° C. with 2 parts of a commercially available neutralized auxiliary tanning agent based on naphthalenesulfonic acid. Thereafter, 9 parts of the tannin solution obtained as described above were added to the liquor and drummed for a further 60 minutes. It was then colored with 1 part of Acid Brown 165 in the same liquor and then greased with 5 parts of a commercially available combination licker. Finally, it was acidified with 1 part of formic acid.
• the leather treated with the tanning agent according to the invention was again dyed significantly deeper.
• the tanning agent obtained was used according to Example 2. A very deeply colored leather was obtained.
• the leather thus produced as in Example 2 was dyed very deeply.
• the leather thus produced as in Example 2 was dyed in a deep tone.
• the leather thus produced as in Example 2 was dyed in a deep tone.
• a reaction vessel provided with a reflux condenser and a stirrer, 61 parts of acrylonitrile, 30 parts of acrylic acid, 9.6 parts of dimethylaminopropyl methacrylamide, 80 parts of dimethylformamide (DMF) and 20 parts of acetone were mixed and heated to 75.degree. Then 4 parts of AIBN were added in 4 portions within 60 minutes. After polymerization for one hour at 75 ° C., the reaction mixture was cooled and dissolved in a mixture of 286 parts of water and 30 parts of concentrated aqueous ammonia solution (NH 3 ). A solution with a solids content of 18.7% was obtained.
• NH 3 concentrated aqueous ammonia solution
• the leather thus produced as in Example 2 was dyed in a full tone.
• the tanning agent obtained was used according to Example 2. A deeply colored leather was obtained.
• the tanning agent obtained was used according to Example 2. A very deeply colored leather was obtained.

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 (3)

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• 1982
  • 1982-01-16 DE DE19823201226 patent/DE3201226A1/de not_active Withdrawn
  • 1982-12-16 DE DE8282111711T patent/DE3272390D1/de not_active Expired
  • 1982-12-16 EP EP82111711A patent/EP0084134B1/de not_active Expired
• 1983
  • 1983-01-10 JP JP58001273A patent/JPS58125800A/ja active Granted
• 1985
  • 1985-05-10 US US06/732,808 patent/US4596581A/en not_active Expired - Lifetime

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