EP3670675A1 - Leather agents for beamhouse - Google Patents

Abstract

On the basis of pseudoalkali metal, alkali metal and alkaline earth metal salts of the sugar acids, new leather auxiliaries have been made available for the water workshop, which have a balanced profile of properties with regard to the swelling and firmness of the leather to be produced on the one hand and the nitrogen or COD entry into the wastewater on the other Page.

Description

During the production of leather, leather is made from a raw skin in several process steps. The process steps summarized as a water workshop are at the beginning of this process and prepare the raw skin for tanning, i.e. takes place before the actual tanning. The water workshop includes the typical steps in this sequence: switch, liming, descaling, pickling and pimples.

The liming takes place in aqueous liquor typically in so-called liming barrels or alternatively in liming reels. The addition of process chemicals and the action of movement remove the hair and other non-leather components of the skin and open up the skin by separating the collagen fibers. For hair removal, either reducing sulfur-containing products (eg Na ₂ S, NaHS, mercaptoethanol, thioglycolic acids) or strong oxidizing agents (eg H ₂ O ₂ ) are usually added. Lime or other alkaline substances are usually added to the skin.

By adding these substances, the pH in the liquor and in the skin usually rises to approximately 11.8 - 12.5. This leads to a significant alkaline swelling of the skin. Depending on the amount of water, the addition of product, the effects of movement and the structure of the skin, this swelling of the skin is pronounced differently. A strong alkaline swelling in connection with the barrel / reel movement leads to a loss of quality in the finished leather in the form of pronounced mast marks ("growth marks") or scars ("lime draw") in loosely structured skin areas. The use of swelling regulators reduces the scar swelling, so that pronounced mast striations and scar tension can be avoided. However, a strong reduction in swelling usually has the disadvantage of increased loose grain in the loosely structured skin areas, i.e. the upper layer of the skin no longer adheres properly to the corium. This then manifests itself when the leather is bent by bulging the scars, i.e. in poor firmness.

In the state of the art, ethanolamines and partly also sugars (eg molasses) are mostly used as swelling regulators, but the latter have to be used in relatively large quantities because of their low efficiency.

All products added during the water workshop are not permanently bound in the skin, but remain in the liming liquor, the washing liquors or the liquors of the subsequent processes (e.g. descaling). The addition of all process chemicals ultimately leads to an increase in the pollution load of the wastewater.

The requirements for avoiding waste water and reducing the amount of dirt have risen steadily in recent years and are likely to become even more stringent. In addition to high COD contents, the additional input of nitrogen leads to capacity bottlenecks in the sewage treatment plants. Therefore, the reduction of nitrogen and COD input is a continuous development focus of the leather auxiliary industry. However, for quality reasons, these aminoethanol and molasses-containing products cannot be dispensed with, despite the poorer wastewater values. You can find them in almost all tanneries in the world.

Against this background, there was a need for alternative swelling regulators which avoid the disadvantages of the prior art and have a balanced property profile with regard to the swelling and graininess of the leather to be produced on the one hand and the nitrogen or COD entry into the waste water on the other hand.

Surprisingly, it has now been found that the object according to the invention is achieved by using pseudoalkali metal, alkali metal and / or alkaline earth metal salts of the sugar acids in leather production, in particular when using these substances as swelling regulators in the liming.

Ammonium, sodium, potassium, calcium and / or magnesium salts of the sugar acids are preferably used in the present invention.

Sodium and / or potassium salts of the sugar acids are particularly preferably used, very particularly preferably sodium salts of the sugar acids.

Sugar acids are understood to be polyhydroxycarboxylic acids that are formed by oxidation from simple sugars (monosaccharides). These include aldonic acids (e.g. D-gluconic acid), uronic acids (e.g. D-glucuronic acid), aldar acids (e.g. D-glucaric acid, D-threaric acid, D-mannosugaric acid) and ketoaldonic acids (e.g. D-2-oxo-gluconic acid).

In the present invention, ammonium, sodium, potassium, calcium and / or magnesium salts of aldonic acids, particularly preferably D-gluconic acid, are preferably used.

In a preferred embodiment, ammonium, sodium and / or potassium gluconate, preferably sodium and / or potassium gluconate and particularly preferably sodium gluconate are used.

Pseudoalkali metal salts are understood to be salts whose cations are not alkali metals, but largely behave as such. For the purposes of the present invention, the term is to be understood as ammonium and / or tetraalkylammonium salts.

The effect of the salts of the sugar acids according to the invention can be improved by using them together with alkaline earth metal formates, preferably magnesium and / or calcium formate, particularly preferably with calcium formate.

Furthermore, the effect of the salts of the sugar acids according to the invention can be optimized by combining them with alkaline earth metal salts of C ₁ -C ₃ carboxylic acids, preferably magnesium and / or calcium salts of formic, acetic or propionic acid, particularly preferably magnesium and / or Calcium salts of formic acid and most preferably used with calcium formate.

An increase in activity can also be achieved by using the salts of the sugar acids according to the invention together with ethanolamines (i.e. monoethanolamine, diethanolamine and / or triethanolamine) or urea.

Last but not least, the effect of the above salts of the sugar acids can be increased by using a combination of alkaline earth metal salts of C ₁ -C ₃ carboxylic acids and ethanolamines or urea.

Alternatively, it is possible to use the salts of the sugar acids according to the invention in combination with alkali metal salts of the C ₁ -C ₃ carboxylic acids, in particular sodium formate, sodium acetate, sodium propionate, potassium formate, potassium acetate and / or potassium propionate, which may be used together with alkaline earth metal salts of C ₁ -C ₃ carboxylic acids, Ethanolamines or urea can be done.

The present invention also relates to processes for the treatment of animal skins in the liming using pseudoalkali metal, alkali metal and / or alkaline earth metal salts of sugar acids, these being added to the liquor in which the treatment of the skins takes place. This treatment also includes variants in which the pseudoalkali metal, alkali metal and / or alkaline earth metal salts of the sugar acids are added to the liquor before the liming in the switch.

In a preferred embodiment, the compounds listed above which support the action of the swelling regulators, such as alkaline earth metal formates, alkaline earth metal acetates, alkaline earth metal propionates, ethanolamines and / or urea, are additionally added to the liquor.

The liquor in which the skins are treated in the liming typically contains further compounds known to the person skilled in the art, such as reducing sulfur-containing products (for example Na ₂ S, NaHS, mercaptoethanol, thioglycolic acids), strong oxidizing agents (for example H ₂ O ₂ ) and / or strongly alkaline substances (e.g. lime).

The present invention also relates to processes for the production of leather comprising the treatment of animal hides according to the invention. Said methods may further include steps of leather production familiar to those skilled in the art, such as Softening, fleshing, splitting, decalcification, enzymatic pickling, degreasing, pimples, tanning, dewatering, folding, bleaching, retanning, dyeing, greasing, stretching, drying, moistening, softening and dry dressing.

The tanning is preferably carried out with mineral tanning agents such as aluminum salts, in particular alums, trivalent chromium salts, zirconium salts, iron, zinc or titanium salts, with polyphosphates, with aldehydes such as formaldehyde and glutardialdehyde, with synthetic tanning agents based on phenol derivatives (syntans) or with polymer tanning agents (Resin tanning agents) such as acrylates and polyurethanes or vegetable dyes. The tanning is particularly preferably carried out using trivalent chromium salts or syntans. Most preferably tanning is carried out with trivalent chromium salts.

In preferred embodiments, the addition of ethanolamines and urea is dispensed with in the process according to the invention or in the use of salts of the sugar acids according to the invention, since the introduction of nitrogen into the waste water can thereby be reduced.

In preferred embodiments, alkali metal salts of gluconic acids, particularly preferably sodium gluconate, are used in the processes according to the invention or in the use according to the invention.

In preferred embodiments, in the process according to the invention or in the use according to the invention, based on the salt weight of the raw skin used, from 0.05 to 5.0% by weight, preferably from 0.1 to 2.0% by weight and particularly preferably from 0.2 to 1.0% by weight of pseudoalkali metal, alkali metal and / or alkaline earth metal salts of the sugar acids are used.

The tanner understands by the salt weight the weight that the skin has after the preservation with salt. The preserved skin typically has a moisture content of 35% by weight.

Further preferred embodiments of the method according to the invention or the use according to the invention relate to the combination of alkali metal salts of gluconic acids with alkaline earth metal formates alone or together with alkaline earth metal acetates, and / or alkaline earth metal propionates.

Further preferred embodiments of the method according to the invention or of the use according to the invention relate to the combination of sodium gluconate with magnesium and / or calcium formate.

Further preferred embodiments of the method according to the invention or of the use according to the invention relate to the combination of sodium gluconate with magnesium and / or calcium formate and alkali or alkaline earth metal acetates and / or alkaline earth metal propionates.

The present invention also includes leather auxiliary compositions comprising one or more pseudoalkali metal, alkali metal and / or alkaline earth metal salts of the sugar acids, preferably ammonium, sodium and / or potassium salts of the sugar acids, particularly preferably sodium salts of the sugar acids.

Leather auxiliary compositions according to the invention advantageously contain one or more pseudoalkali metal, alkali metal and / or alkaline earth metal salts of gluconic acid, preferably ammonium, sodium and / or potassium gluconate, particularly preferably sodium gluconate.

Further advantageous leather auxiliary compositions additionally contain one or more compounds from the group comprising alkaline earth metal salts of C ₁ -C ₃ carboxylic acids, monoethanolamine, diethanolamine, triethanolamine and urea, preferably magnesium and / or calcium salts of formic, acetic or propionic acid, monoethanolamine, diethanolamine, Triethanolamine and urea, particularly preferably magnesium and / or calcium salts of formic or acetic acid and most preferably calcium formate.

Further advantageous leather auxiliary compositions contain ammonium, sodium and / or potassium gluconate in combination with magnesium formate, calcium formate magnesium acetate and / or calcium acetate, preferably sodium and / or potassium gluconate in combination with magnesium formate and / or calcium formate.

The leather auxiliary composition preferably contains sodium gluconate and one or more compounds from the group comprising calcium formate and magnesium formate, preferably calcium formate.

In particularly advantageous embodiments, the ratio of the pseudoalkali metal, alkali metal, and / or alkaline earth metal salts of the sugar acids to the compounds from the group comprising alkaline earth metal formates, alkaline earth metal acetates, alkaline earth metal propionates, monoethanolamine, diethanolamine, 90 to urethane composition and from triethanolamine 90 10, preferably from 20:80 to 80:20 and particularly preferably from 30:70 to 70:30. The ratio is determined as the quotient from the total mass of the compounds of the above salts of the sugar acids to the total mass of the compounds of the above formates, acetates and propionates.

The leather auxiliary compositions according to the invention are typically swelling regulators, in particular swelling regulators for the water workshop.

The leather auxiliary compositions according to the invention can be in liquid or in solid form. In a preferred embodiment, the leather auxiliary composition according to the invention is at 25 ° C. as a solid, ideally in particulate form, such as, for example, as a powder, granulate or pellet.

Examples Sample preparation:

The screening tests were carried out on raw skin samples DIN A4. These were cut from the core area of a salted raw skin, so that all samples had a similar fiber structure. The samples of a series were taken from the same skin because the fiber structure of the skin differs from animal to animal. The test specimens were weighed individually. All percentages of the process recipe refer to this weight (the raw skin salt weight).

The test procedure included the process steps "switch" and "liming". The amounts of chemicals and products used in the process as well as the amount of water are in percent by weight based on the raw skin salt weight of the individual samples. The quantities were weighed on a balance with an accuracy of 0.5 g.

The tests were carried out in small test tanning drums, diameter 300 mm with temperature regulation (manufacturer Dose). The process temperature was kept constant at 28 ° C +/- 1 ° C.

Switch:

The test specimen was added individually to the sample barrel and 200% water (based on the salt weight) at a temperature of 28 ° C. and 0.3% Peltec BH softening agent (mixture of surfactant and bactericide from LANXESS Deutschland GmbH) were added. The test barrel was rotated at 10 RPM for 300 minutes. The liquor (process water) was then drained off. The specimen is now dabbed off, weighed and the average thickness is determined at four measuring points.

Liming:

The test specimen was put back into the test barrel and 200% water at a temperature of 28 ° C. was added and 15 min. rotates. The remaining salinity of the fleet was then determined. This should not exceed 3.5 ° Bé. If the salt content is too high, the fleet should be changed once.

The swelling regulator was added to the fleet and the test keg 60 min. rotates. The weight was then determined and the average thickness was determined. The test specimen was returned to the liquor, 3% lime (Ca (OH) ₂ ) and 2.5% Na ₂ S were added and the mixture was rotated for 4 hours. Then there were 15 hours. Barrel rotation in interval mode (rotate 10 min. / 50 min. Break). The pH of the liquor was then measured (pH 12-12.5), the specimen was removed, weighed again and the average thickness measured. The swelling was determined from the increase in thickness.

The test specimens were then washed and with a standard chrome tanning (as described for example in E. Heidemann, Fundamentals of Leather Manufacturing, pp. 295-340, E. Roether Verlag, Darmstadt, 1993 ) tanned and then checked for firmness by bending the leather. If the surface in the crease was smooth, did not rise, and did not curl, a positive firm grain was found.

The results of the swelling measurement and the assessment of the solid pitting are shown in Table 1.

The results show that the use of salts of the sugar acids according to the invention makes it possible to dispense with the use of nitrogen-containing compounds such as urea or ethanolamines, as a result of which the introduction of nitrogen into the wastewater can be substantially reduced, but at the same time the pitting can be maintained or improved . In addition, the results show that the use of salts of the sugar acids according to the invention together with nitrogen-containing compounds such as urea or ethanolamines, ie with a constant nitrogen input into the waste water, can achieve a substantial improvement in the solid grain. Table 1 No. Additive% Additive Thickness before (mm) Thickness after (mm) Swelling (mm) Swelling (%) Firmness (crust) 1 0 without 3.1 5.8 2.7 87% ○ 2nd 0.5 urea 2.7 5.0 2.3 85% ○ 3rd 0.5 Sodium sulfate 3.3 5.7 2.4 73% ○ 4th 0.5 Sodium acetate 3rd 5.8 2.8 93% ○ 5 0.5 Magnesium acetate 3.6 6.0 2.4 67% ○ 6 1 24% ethanolamines 3.3 5.5 2.2 67% + 7 2nd 24% ethanolamines 4th 6.2 2.2 55% + 8th 0.5 Calcium formate 3.4 5.4 2nd 59% ○ 9 1 Calcium formate 3.4 5.0 1.6 47% ○ 10th 0.5 Magnesium formate 5.2 7.5 2.3 44% ○ 11 0.8 Sodium gluconate 4th 6.5 2.5 63% + 12 0.8 10% magnesium acetate 3.3 5.1 1.8 55% + 20% sodium gluconate 70% calcium formate 13 0.8 33% magnesium acetate 4th 6.0 2nd 50% + 33% sodium gluconate 33% calcium formate 14 0.8 30% sodium gluconate 3.4 4.9 1.5 44% +++ 70% calcium formate 15 0.5 30% sodium gluconate 5 8th 3rd 60% + 70% urea 16 0.5 10% magnesium acetate 3.2 5.2 2nd 63% + 20% sodium gluconate 70% calcium formate 17th 0.5 70% sodium gluconate 5.2 7.7 2.5 48% + 30% magnesium formate 18th 0.5 30% sodium gluconate 5.3 7.7 2.4 45% ++ 70% magnesium formate 19th 0.5 70% sodium gluconate 4.9 7 2.1 43% +++ 30% calcium formate 20th 0.5 30% sodium gluconate 5 7 2nd 40% ++ 70% calcium formate 21st 1 20% ethanolamines 5.3 7.2 1.9 36% ++ 20% sodium gluconate 22 1 30% sodium gluconate 5.1 6.9 1.8 35% +++ 70% calcium formate

Claims (15)

Use of pseudoalkali metal, alkali metal, and / or alkaline earth metal salts of the sugar acids in leather production. Use according to claim 1, wherein compounds selected from the group consisting of ammonium, sodium, potassium, calcium and magnesium salts of the sugar acids, preferably sodium and potassium salts of the sugar acids, particularly preferably sodium salts of the sugar acids. Use according to one or more of claims 1 and 2, wherein salts of aldonic acids, uronic acids, aldar acids or ketoaldonic acids, preferably aldonic acids and particularly preferably gluconic acid, are used. Use according to one or more of claims 1 to 3, wherein ammonium, sodium and / or potassium gluconate, preferably sodium and / or potassium gluconate and particularly preferably sodium gluconate is used. Use according to one or more of claims 1 to 4 in the water workshop, in particular as a swelling regulator in the liming. Use according to one or more of claims 1 to 5, the use together with alkaline earth metal salts of C ₁ -C ₃ carboxylic acids, preferably magnesium and / or calcium salts of formic, acetic or propionic acid, particularly preferably magnesium and / or calcium salts of Formic acid and most preferably with calcium formate. Use according to one or more of claims 1 to 6, wherein the use takes place together with monoethanolamine, diethanolamine, triethanolamine or urea. Use according to one or more of claims 1 to 7, wherein, based on the salt weight of the raw skin used, from 0.05 to 5.0% by weight, preferably from 0.1 to 2.0% by weight and particularly preferably from 0.2 up to 1.0% by weight of pseudoalkali metal, alkali metal and / or alkaline earth metal salts of the sugar acids are used. Process for the treatment of animal skins in the liming using pseudoalkali metal, alkali metal and / or alkaline earth metal salts of the sugar acids according to one or more of claims 1 to 8, wherein the pseudoalkali metal, Alkali metal and / or alkaline earth metal salts of the sugar acids are added to the liquor in which the skins are treated. A process for producing leather comprising the treatment according to claim 9. Leather auxiliary composition containing one or more pseudoalkali metal, alkali metal and / or alkaline earth metal salts of the sugar acids, preferably ammonium, sodium and / or potassium salts of the sugar acids, particularly preferably sodium salts of the sugar acids. Leather auxiliary composition according to claim 11 containing one or more pseudoalkali metal, alkali metal and / or alkaline earth metal salts of gluconic acid, preferably ammonium, sodium and / or potassium gluconate, particularly preferably sodium gluconate. Leather auxiliary composition according to one or more of claims 11 and 12 additionally containing one or more compounds from the group comprising alkaline earth metal salts of C ₁ -C ₃ carboxylic acids, monoethanolamine, diethanolamine, triethanolamine and urea, preferably magnesium and / or calcium salts of the ant, vinegar or propionic acid, monoethanolamine, diethanolamine, triethanolamine and urea, particularly preferably magnesium and / or calcium salts of formic or acetic acid and most preferably calcium formate. Leather auxiliary composition according to one or more of claims 11 to 13, containing sodium gluconate and one or more compounds from the group containing calcium formate and magnesium formate, preferably calcium formate. Leather auxiliary composition according to one or more of claims 13 to 15, wherein the ratio of the pseudoalkali metal, alkali metal, and / or alkaline earth metal salts of the sugar acids to the compounds from the group comprising alkaline earth metal formates, alkaline earth metal acetates, alkaline earth metal propionates, monoethamine amine trolane, monoethamine amine, monoethanolamine, monoethanolamine, monoethamine amine, monoethanolamine, and 90 to 90:10, preferably from 20:80 to 80:20 and particularly preferably from 30:70 to 70:30.