CS208461B2 - Method of chromtanning of leathers - Google Patents

Description

(54) Method of leather tanning i '

The present invention relates to a process for the chromo-tanning of leather using a composition comprising neutral or basic aluminum chlorides and / or aluminum sulphates and a complexing agent in the environment. acidified, for example, with hydrochloric and / or sulfuric acid.

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The use of aluminum salts in tanning is well known, using for example aluminum sulfate or aluminum chloride, more or less basic.

However, the results of such tanning are not entirely satisfactory because of the low water resistance and low temperature of the leather to be detached. ·

The use of chromium salts in tanning leads to technologically good results, but they do not cause environmental problems. In addition, a significant shortage of chromium-containing minerals is expected in the future to increase the consumption of this raw material in a wide variety of industries.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method which is suitable for tanning leather without the aforementioned drawbacks and which is easy to use on an industrial scale.

According to the method of the present invention, these objectives are achieved by tanning leather using an aluminum-containing composition which is characterized in that the leather is treated with an acidic tanning agent containing neutral or basic aluminum chlorides and / or aluminum sulphates in an amount of 0.6 to 2%. and a complex-forming agent consisting of polycarboxylic organic acids or their alkali salts, wherein the amount of chromium is expressed as chromium oxide. is at least 0.2% by weight based on the weight of the raw leather.

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It has been found, surprisingly, that the use of said aluminum-containing composition in a normal tanning process results in a substantial reduction in the usually necessary chromium, while achieving results similar to or even better than in normal chromium tanning.

In normal chromium tanning, the amount of basic chromium sulphate used, calculated on chromium trioxide, is about 3%, usually 2% to 4% chromium trioxide, based on the weight of the raw leather. In the process according to the invention, however, the basic chromium trichloride, calculated on chromium trioxide, can be reduced to less than 0.2%, even if it is added such an amount of the preparation according to the invention so that the aluminum content is Aluminum, 0.6 to 2%, based on the raw material's roughness. Leather tanned in this way has similar or better properties to that of conventional chrome. The process according to the invention achieves a softer and more compact change, a soft touch and uniformly shiny coloring.

Best results are obtained using 0.7% basic chromium (III) sulphate, expressed as chromium trioxide, based on the roughness of the raw leather.

When using the product according to the invention, it is also advantageous that the waste water which has to be treated is cleaner because the concentration of chromium, partly or completely replaced by aluminum, can be substantially reduced, so that the waste water is completely chromium free in some cases.

The preparation of the composition according to the invention is described in detail below.

The complexing agent is added to the aluminum salt with stirring under acidic conditions, for example hydrochloric and / or sulfuric. Organic polycarboxylic acids or their alkali salts are particularly suitable for this purpose. ,

The smallest and best possible coppexing agent varies depending on its nature. For example, when co-exfoliating agents are used to stabilize the solution at a pH of about 4 citric acid, a minimum of 50 parts citric acid monohydrate per 100 parts alumina at a concentration of 100% is required, while the best solution is 70 to 80 parts. 100% citric acid per 100 parts alumina.

The solution thus prepared is allowed to stand until the temperature drops to 25-30 ° C. An analyte, usually an alkali metal or alkaline earth metal hydroxide, or a de-carbonate or carbonate (III) carbonate is then added to a pH of 3.9-4.3.

Any concentration of aluminum in the solution may be suitable, but it is usually preferred that the concentration of aluminum in the solution, expressed as alumina, be 3 to 11%.

The product can also be used in the solid state if water is separated from it.

The invention is illustrated by the following examples, which are not intended to limit the scope of the invention in any way.

Percentages and parts are always intended to be used unless otherwise stated.

They diligently work

100 kg of the preparation are prepared in this way;

To 33 kg of a solution containing basic aluminum chloride and basic aluminum sulphate having an aluminum concentration, calculated as 11% alumina and a pH of 1.7, was added 2.8 kg of citric acid monohydrate dissolved in. 11 kg of water.

After a short -míchání was added 5.0 kg of sulfuric acid 66 Bé stirring, cooled the TN ^{p 2} Lot 5 ° C was added p ^. ^{16 kg} water and ²⁷ kg ^P and a RTZ aq ^eh ^ with 5.4 kg of sodium hydroxide. This adjusts the pH to 4.1 to 4.2.

Make up to 100 kg by adding water. The sensation is 10 times from the back of cattle weighing 230 kg of raw leather.

Conventional pickling and pickling of leather is made in a bath of the following composition (the percentages always refer to the gross weight of the raw).

To 20% water, 1.8% sodium (sodium chloride), add 7.25% of the above preparation containing 0.26% aluminum, calculated on aluminum oxide. The leather is treated in a barrel bath for 4.5 hours, then left to rest overnight in the bath, further worked in a barrel for 30 minutes, and 2.4% basic chromium sulphate containing 25% chromium, calculated to chromium trioxide corresponding to 0.6% of the tanning bath content, also calculated as chromium trioxide.

The mixture was stirred for an additional 50 minutes and after addition of 0.5% cationic liquor, the bath was stirred for an additional two hours, followed by 0.9% sodium hydrogencarbonate. Stir for 2 and a quarter hours; the pH of the solution is 3.6.

20% by weight, based on the weight of the raw leather, of the composition prepared above, corresponding to a content of 0.72% of aluminum, calculated on alumina, is now added. The mixture was stirred for a further 2.5 hours, 0.55% sodium bisulfite was added to raise the pH to 3.9, and the reaction was stirred for an additional two hours and then left to stand overnight. Further, the leather is processed in a manner known per se.

In fact, tanned leather is very similar to the usual wreckage.

Example 2

The preparation is prepared as follows:

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Mixed with 322 kg of hlinKého hydroxide containing 57% alumina, 756 kg of 20.6% hydrochloric acid and 293 kg of 98% of the sulfur kkyseiny К solution was added 133 kg acid monohydrate ^ 0 ^ (^ at 90 ⁰ C with -Ю kg -zoty.

1530 kg of a 30% sodium carbonate solution are then added over a period of two hours while maintaining the temperature, reaching a final temperature of 50 ° C.

This gives 3,350 kg of a salt of 5.5% oxide and a pH of 3.9.

After removal of water, 1,025 kg of solid product was obtained with 18% oxide získáίη ^ δΐηζ.

8 calf skins are made with a weight of 130 kg of raw leather. After the usual decalcification, pickling and pickling, the leather is made in the following way (percentages relate to the weight of the raw desserts):

To 25% of water, 2% of salt (sodium chloride), add 1.5% of the above-prepared dry preparation of 18% aluminum, calculated on aluminum oxide equivalent to 0.27% aluminum, calculated on aluminum oxide, in the tanning bath. .

In the tanning bath, the raw leather is treated in the barrel after two hours of heat, and then added

2,8% of basic chromium sulphate (25% of chromium, calculated on chromium trioxide), corresponding to

0,7% of chromium in the tanning bath, expressed as chromium oxide.

It is processed in the barrel for an additional two hours, after which 0.7% sodium hydrogen carbonate is added in three or four portions to a pH of 3.7 to 3.8, at which time 4%, still based on the weight of raw leather, is added, prepared dry preparation, corresponding to 0,72% aluminum, calculated on alumina, in the tanning bath.

Working in a barrel for two and a half hours, the solution is made alkaline by addition of sodium bicarbonate in three or four. doses with a concentration of 0.2 to 0.3% up to. pH values 3.9 to 4.

The leather is then left overnight in a paddle barrel and further processed in a manner known per se.

The characteristics of tanned leather are similar to standard chrome.

Example 3

The preparation is prepared as described in Example 2, but instead of 133 kg of citric acid monohydrate, 186 kg of sodium citrate dihydrate and 1194 kg are used instead of 1530 kg of 30% sodium carbonate. After removal of water, the preparation contains 18% alumina.

25 bovine leather is made of 100 kg of raw leather. After descaling, pickling and pickling, the leather is made under the following conditions (percentages are based on the weight of the raw leather):

Up to 25% water and 2% salt. (sodium chloride), 1.5% of the above preparation containing 18% aluminum, calculated on alumina, corresponding to 0.27% aluminum, calculated on alumina, is added in the tanning bath.

The leather is treated in a drum in the bath for two hours and then added 2.8% basic sulphate ctoomit it ^é ^ o ^{(^} c ^h contained RMU 25 ^ ^par e ^p octene to οΙιγοπι oxi ^{d 0} · ^^ which the ^dp OVI ^gives the chromium content, calculated on the chromium oxide, in the tanning liquor 0.7% · is also prepared in a barrel for two hours and - - three or four doses was placed about 0.7% 1уdroggenu! iččtanu solution until pH of the solution was 3.7 to 3.8.

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4% of the solid preparation prepared above, corresponding to a content of 0.72% of aluminum, calculated on alumina, is added in the tanning bath at this time, still based on the weight of the raw leather. Processed in a barrel - for two and a half hours, the solution is alkalinized with sodium carbonate in three or four portions of o ηοοΜ ^ θα! 0.2 to 0.3%, up to a pH of 3.9 to 4.0. The leather is then left in the drum vane over the noe.

It is further processed in a manner known per se. The characteristics of tanned leather are similar to those of standard chrome.

Example 4,

The preparation is prepared as follows:

97 kg of 57% alumina, 290 kg of 31% sodium hydroxide solution are mixed and 40 kg of citric acid are added after completion of the reaction; the solution obtained is gradually added over one hour with stirring and at room temperature. 50 ° C to another solution of the following composition:

kg of citric acid monohydrate, 540 kg of crystalline aluminum sulphate (17% alumina content) and 650 kg of vnd.

208461 The reaction mixture was stirred for two hours at 50 ° C to give 1,657 kg of a solution containing 8.9% alumina and having a pH of 3.9. After removal of water, 590 kg of solid preparation containing 25% alumina are obtained.

100 goats' leather weighing 106 kg of raw leather is made. Decalcification, pickling and picking are carried out in the usual way, whereupon the leather is made as follows (percentages are based on the weight of the raw leather):

To 25% water and 2% salt (sodium chloride) was added 1.04% of the above preparation (25% alumina concentration), which corresponds to the aluminum content, calculated as alumina, 0.26%.

The leather is treated in a barrel bath for two hours and 2.8% basic chromium sulphate (chromium content 25%, calculated on chromium oxide) is added, corresponding to the chromium content in the tanning bath 0.7%, calculated on chromium oxide.

After a two-hour barrel treatment, about three or four portions are added

0.7% sodium bicarbonate up to a bath pH of 3 _? 7 to 3.8. At this point, still taking into account the weight of the raw leather, 2.8% of the dry preparation prepared above, corresponding to 0.72% of aluminum, calculated on alumina, was added in the tanning bath.

It is worked in a barrel for two and a half hours and then made alkaline by adding 0.2 to 0.3% sodium bicarbonate in three or four portions up to a pH of 3.9 to 4. * The leather is then left overnight in the barrel with blades and then processed in a manner known per se.

Properties of tanned leather are similar to standard chrome tanning.

Example 5

The preparation was prepared as described in Example 3. After removal of water, a product with an alumina content of 18% was obtained.

10 skins of bovine animals weighing 150 kg of raw leather are made. After descaling, pickling and pickling, the leather is made as follows (percentages are based on the weight of the raw leather):

To 25% water, 2% salt (sodium chloride), add 1.5% of the above prepared aluminum concentration product, calculated on alumina, 18%, corresponding to the aluminum content, calculated on alumina, in a tanning bath of 0.26% .

The leather is made in a barrel for two hours, after which 0.8% of basic chromium sulphate (chromium content, calculated on chromium trioxide, 25%), corresponding to the chromium content, calculated on chromium trioxide, in a tanning bath is added. .

It is worked in a barrel for two hours and then about 0.7% sodium bicarbonate is added in three or four portions up to a pH of 3.7 to 3.8. Then, based on the weight of the raw leather, 6.8% of the dry preparation prepared above, corresponding to 1.22% of aluminum, calculated on alumina, is added in the tanning bath.

It is worked in a barrel for a further two and a half hours and then the solution is basified with 0.2 to 0.3% sodium bicarbonate in three to four portions up to a pH of 3.9 to 4.0. The leather is then left overnight in a barrel and further processed in a manner known per se.

The characteristics of tanned leather are very good.

She said d

The preparation is prepared as follows:

37 kg of aluminum sulphate containing 16% alumina, 19 kg of aluminum chloride hexahydrate and 20 kg of scalic acid dihydrate are dissolved from stirring at 90 DEG C. in 44 kg of water. To the solution thus obtained was added 174 kg of 2095 sodium lilithium solution with stirring to a final temperature of 40 ° C.

269 kg of a 3.71% alumina solution having a pH of 3.92 were obtained.

Ten leather is made from calves of 150 kg raw leather. After the usual decalcification, pickling and pickling, the leather is made under the following conditions (the percentages are based on the raw material leather content):

To the 20% water, 2% salt (sodium chloride) solution of 7% (containing 3.71% aluminum, calculated on alumina) corresponding to 0.26% aluminum, calculated on alumina , in the tanning bath.

It is processed in a barrel for two hours and then 2.8 95 basic chromium sulphate (at 25 95 chromium, calculated on chromium trioxide), corresponding to 0.7% chromium, calculated on chromium trioxide, are added in the tanning bath. It is worked in a barrel for two hours, then a 0.7% sodium hydrogencarbonate solution is added in three or four portions up to a bath pH of 3.7 to 3.8.

At this point, 19.4 95, based on the raw material hmoon content, of the above prepared solution, corresponding to 0.72 95 aluminum, calculated as alumina, is added.

It is treated in a barrel for two and a half hours, and then a 0.2-0.3% sodium hydrogencarbonate solution is added in two or four portions up to a pH of 3.9-4.0. The leather is then sampled at rest in a paddle barrel and further processed in a manner known per se.

The tanned leather obtained has similar properties to standard chromo-tin.

Example 7

The preparation is prepared as follows:

While stirring at 90 ° C, 37 kg of aluminum sulfate (16% alumina content), 19 kg of aluminum chloride hexahydrate and 20 kg of tartaric acid are dissolved in 44 kg of water. 148 kg of a 20% sodium nitrite solution are added to the solution thus obtained, with stirring, up to a final temperature of 40 ° C. 235 kg of a 4.24% nitric oxide solution having a pH of 3.91 are obtained.

25 cow leather weighing 100 kg raw leather is made. After the usual decalcification, pickling and picking, the leather is made according to the following conditions (the percentages always refer to the weight of the raw leather):

To 20% water, 2% salt (sodium chloride), add 6.13% of the above prepared 4.24% aluminum, calculated on alumina, which is 0.26% aluminum, calculated on alumina aluminum, in tanning bath.

It is worked in a barrel for two hours and then 2.8% of basic chromium sulphate (at 25% chromium, calculated on chromium oxide), corresponding to 0.7% chromium, calculated on chromium oxide, is added in the tanning bath.

206461

It is processed in a barrel for two hours and then added in about three or four portions of about 0.7%. sodium bicarbonate up to a pH of 3.7 to 3.6. At this point, still taking into account the weight of the raw leather, 17% of the above preparation is added, corresponding to 0.72% of aluminum, calculated on alumina,

It is worked in a barrel for two and a half hours, after which the bath is made alkaline by adding three or four portions of 0.2 to 3.3% sodium solution up to a pH of 3.6 to 3.9.

Leave the leather to rest overnight in a paddle barrel and then work in a manner known per se.

The tanning properties are similar to those of the standard tanning process.

Claims (5)

SUBJECT OF THE INVENTION 1. A process for the chromo-tanning of leather by an aluminum-containing element, characterized in that the leather is treated with an acid-containing chromium tin-containing mixture of neutral or basic aluminum chlorides and / or aluminum sulphates. % of polycarboxylic organic acids or their alkali salts, wherein the amount of chromium, calculated on chromium trioxide, is at least 0.2% by weight. 2. The method according to bo sulfuric acid. The composition of claim 1, wherein the mixture comprises hydrochloric acid and / or not 3. The method according to seline citoon. point wherein j and ^k are of ^{the P} omp exotvorného Mnidla. ^ ^ky užívř 4. @ The process according to 4.3. The method is characterized in that the final pH of the mixture is adjusted to 3.9 5. The process of claims 4 to 3, based on alumina, is from about 3 to about 11% by weight of alumina.