CH85164A - Process for the preparation of a tanning agent. - Google Patents

Description

  

  Process for the preparation of a tanning agent. The present process for the preparation of a tanning agent is based on first condensing naphthol monosulphonic acid 2: 6 along with naphthylamine monosulphonic acid 2: 7 with form aldehyde in sufficient dilution in the presence of a little sulfuric acid at 70-80 o C, and then condensing the solution obtained, which contains the contains a condensation product, which is a high quality tanning substance, in a dissolved state, together with free sulfuric acid, at least partially with a hydroxide of a metal whose salts themselves have a tanning effect.

    Such metal hydroxides are the hydrate of chromium, aluminum, iron, etc.



  The tanning agent solution obtained by the process in a strength of 24-280 B6 is completely ready to use, in commercially available form and does not require any cleaning or other treatment. In addition to its very high tanning effect, it also has the property of giving the leather tanned with it a yellow color, so that further coloring of the leather can either remain undone or only a weak re-coloring to a desired color tone has to take place. The yellow color of the leather obtained during tanning also gives off a good basic shade in order to achieve a deep, rich black.



  <I> Example </I> 20 kg of beta-naphtol are sulfonated at 105 ° C. with 30 kg of concentrated sulfuric acid of <B> 660 </B> Be. The sulfonic acid (or the mixture of sulfonic acid and free sulfuric acid) is dissolved in 100 liters of water, then 34.2 kg of 2 # 7-naphty laminmonosulfonic sodium (corresponding to 31.2 kg of free acid) are added and the mixture is adjusted to <B. > 70-800 </B> C heated. 32 kg of thirty percent formaldehyde, which is diluted with 50 liters of water and heated to <B> 70 '</B>, is allowed to run into this mixture.



  After the condensation (after two hours at the earliest), 86.4 kg of chromium hydroxide paste (containing 10,236 kg of Crz (OH) 6 or 7.555 kg of Cr 2 O 3) are added and then another 5 kg of 98% soda are introduced. A tanning analysis according to the main powder filter method showed the following composition:
EMI0002.0001
  
    Tanning <SEP> substances <SEP> 26.08
<tb> Non-tanning agents <SEP> 5.040o
<tb> Insoluble <SEP> <B> 0.180 /, </B>
<tb> Water <SEP> <B> 68,700 /, </B>

 

Claims (1)

PATENT CLAIM: Process for the preparation of a tanning agent, characterized in that first naphthol monosulfonic acid 2: 6 together with naphthyl amine sulfonic acid 2: 7 condenses with formaldehyde in sufficient dilution in the presence of a little sulfuric acid at 70-80 ° C. and then the resulting solution, which contains the condensation product, which is a high-quality tanning agent, in a dissolved state together with free sulfuric acid, is neutralized, at least partially with a hydroxide of a lyletalles, the salts of which have a self-tanning effect. The cerium solution, obtained in a strength of 2-t-28 B8, is completely ready for use, in commercially available form and does not require any cleaning or other treatment. In addition to its very high tanning effect, it also has the property of giving the leather tanned with it a yellow color, so that further coloring of the leather can either be omitted or only a weak re-coloring to a desired color tone has to take place. The yellow color of the leather obtained during the tanning process also gives off a good basic tone in order to achieve a deep, rich black.