DE639787C - Process for the production of iron leather - Google Patents

Description

Process for the production of iron leathers When tanning with inorganic In contrast to tanning with chromium and aluminum salts, it is not iron salts possible to produce ready-to-use tanning solutions by increasing the basicity, because iron hydroxide is precipitated in the process. It has already been suggested the acidity the iron salt solutions gradually dull during the tanning process; here receives one leather that does not swell when washed, but otherwise tinny and hard and dry up empty and have a very poor shelf life. Better leather you get when you work with complex iron compounds that are organic in the complex Containing acids with one or more carbon atoms, tans the iron leather obtained in this way if necessary post-treated with synthetic tanning agents. It has already been suggested have been to add protein degradation products to the tanning liquors. All of these procedures own however, they have disadvantages and are therefore not put to practical use.

It has now been found that leather of good quality can be obtained in a simple manner Color, firm scars and a good grip are obtained when you get pelts with such complex ones Iron compounds tanned, the organic substitution products of ammonia in the complex -contain. Such a complex iron compound is e.g. B. the hexahurea iron chloride of the formula [Fe (H @ N-CO-NHZ),] C13, It is produced by adding an iron chloride solution with the calculated amount of urea. An iS percent solution of this salt shows a pH value of 2.5 and can after the addition of sodium chloride, sulfate or -acetate can be used directly for tanning, instead of urea other organic nitrogen compounds are also bound in complexes in the iron salts be e.g. B. Acid amides, such as formamide and acetamide, condensation products between Aldehydes and amines or ammonia, such as hexamethylenetetramine, and also urethanes; Amines and similar connections.

The tanning of the pelts with the complex iron salts mentioned takes place in a few hours - and the leather - can be done immediately, better after a short time Storage, rinsed if necessary,! Blunted, or -neutralized and ;; as usual, be trimmed. To protect sensitive leather, you can also use it during the Tanning by adding soda, sodium carbonate, sodium acetate or sodium phosphate solution dull, - without iron hydroxide precipitating.

The leather obtained in the manner described can be compared with synthetic Post-treatment of tanning materials, expediently those that are neutral cide'r, weakly acidic, wodu @ zh in many cases a softer and fuller leather is obtained; do you want to obtain a tan-colored leather, one must avoid such synthetic tanning agents, which contain oxy groups.

Instead of the pelts with the synthetic tanning agents only after tanning To treat with the iron salts, you can do both treatments at the same time. make. The inorganic acid residues outside of the iron complex salts are thereby removed replaced in whole or in part by residues of such: acids that have a high affinity have to the skin. Finally, one can also use the complex iron salts with dissociable, inorganic acid residues and the alkali salts of synthetic tanning agents, e.g. B. from hexahurea iron chloride or its components and the sodium salt of a Condensation product from - naphthalenesulfonic acid and formaldehyde, the corresponding Manufacture and isolate complex iron salts that directly affect the Leather that would otherwise only be obtained through retanning with synthetic tanning agents receives.

Other acids with a high affinity for the skin can, for. B. the condensation products of aromatic sulfonic acids, such as phenolsulfonic acids, cresol sulfonic acids, with low molecular weight Aldehydes and ketones, as well as the action products of urea and formaldehyde apply to the aforementioned condensation products. Also sulphonic auxiliaries, those obtained by treating the residues obtained from anthracene cleaning with concentrated sulfuric acid come as salt formers for the present Complex compounds into consideration.

With these high molecular weight sulfonic acids arise easily in water soluble, complex iron compounds, either as solid, glassy masses or thick, viscous pastes can be obtained and after redissolving in water directly Results in solutions with excellent tanning properties. After about 5 to 10 hours Fulling, the tanning is already over, and you get a full-grip, good dyed and tight-grain leather, which, as usual, is greased and trimmed can. The leathers are also characterized by a very high yield for iron leather (up to about 50 ° 1a) off; it can be used with these tanning agents according to the The usual method of vegetable tanning even produces hanging colors.

Some of the nitrogen-containing compounds that are complexed in the tanning agents described -: Ilerbindungen can also by other _ '= i @ rbindungen, z. B. weak organic Acids, replace, whereby the liquor gets a darker color: You can here especially the extraction of the tannin from the broth due to the lightening that occurs watch well.

EXAMPLE 1 100 parts by weight of veal pelts picked in the usual way are drummed for a few minutes with 100 ° 10 water and 20% sodium chloride, then 10 ° 10 hexahurea iron chloride (Barbieri, C. 1913, Il. 1034), 501, table salt and 100 ° J0 Water added. It is drummed until it is completely tanned. Soda solution is then added for about 8 hours at intervals of 21/2 hours each until the reaction is Congo-neutral. The leather is then rinsed cold and warm, greased and finished in a known manner.

Example 2 100 parts by weight of beef pelts picked in the usual way are drummed for a few minutes with 1000 /, water and 2010 table salt. Be afterwards them with 25,010 of the complex iron salt, which is obtained by concentrating an aqueous solution of iron chloride and acetamide in a molar ratio of i: 6 is obtained in vacuo, furthermore mixed with 12.5 ° 1o table salt and 100 ° 1a water and drummed for 8 hours in the barrel, after which complete tanning is achieved. The leather is then treated with 100% water and io ° Jo of the neutral sodium salt of a condensation product of naphthalenesulfonic acid and formaldehyde aftertreated for a further 2 hours and finished in the usual way. A light-colored, storage-stable, good-grip leather is obtained in this way.

Example 3 A solution containing 1 mole of a conventionally prepared Complex salt of ferric chloride and hexamethylenetetramine is made up of 3 equivalents of the acidic condensation product of naphthalenesulfonic acid and formaldehyde are added. The solution is made slightly acidic to the Congo by adding sodium hydroxide solution. By Concentrating in a vacuum gives the tannin as a thick, viscous, red syrup.

The tanning is carried out in such a way that 100 parts by weight of beef pelts picked in the customary manner are drummed with 100% water and 2% sodium chloride for a few minutes and then 12% iron tanning agent, dissolved in 360 % water and 60% /, Table salt, add and roll the whole thing in the barrel until it is completely tanned, which is the case after 6 to 10 hours, depending on the nature of the pelts. The leather is then rinsed cold and warm and in the usual. Way greased and dressed. A firm, smooth-grain, full leather is obtained in this way: Example q.

By adding 6 moles of formamide to an aqueous solution of i mole Iron chloride gives hexaformamide iron chloride. 3 equivalents are stirred into this solution of the acidic condensation product of naphthalenesulfonic acid and formaldehyde and makes the solution slightly acidic to the Congo by adding sodium hydroxide solution. By constricting in a vacuum you get a thick, viscous, red syrup, which in the same way as in Example 3 can be used as a tanning agent.

Example 5 30 equivalents of the sodium salt of the condensation product of naphthalenesulfonic acid and formaldehyde are added to an aqueous solution of 12.5 mol of iron chloride, 20 mol of sodium acetate and 15 mol of urea; the resulting solution is concentrated in vacuo at 30 ° to 40 °, a thick, viscous syrup being obtained which, when air-dried, gives a solid, glassy mass with an appearance similar to that of natural tannins. This tanning agent is used as indicated in Example 3. Example 6 An aqueous solution of 1 mole of hexahurea iron chloride is mixed with 3 moles of the sulfonation product from residues of the anthracene purification and made slightly acidic to Congo by adding sodium hydroxide solution. Concentration in a vacuum gives the tannin as a thick, viscous syrup, which is used in a manner similar to that in Example 3.

Claims (3)

PATENT CLAIM i. Process for the manufacture of iron leathers, thereby characterized in that one pelts with solutions of such complex iron compounds treated that contain organic substitution products of ammonia in the complex, and optionally the leather obtained in this way, an aftertreatment with synthetic Subjects to tanning agents. 2. Embodiment of the method according to claim i, characterized characterized in that solutions of such complex iron compounds are used, which contain organic substitution products of ammonia in the complex and their External valences are completely or partially saturated with such acids, the affinity have to the skin. 3. embodiment of the method according to claims i or 2, characterized in that one uses solutions of such complex iron compounds, the weak acids, especially the lower ones, in addition to the substitution products of ammonia aliphatic acids, contained in the complex.