EP3924523B1 - Leather agents for beamhouse - Google Patents

Description

During leather production, leather is made from a rawhide in several process steps. The process steps summarized as a water workshop are at the beginning of this process and prepare the rawhide for tanning, i.e. takes place before the actual tanning. The water workshop includes the work steps soaking, liming, deliming, pickling and pickling, which are typically carried out in this order.

The liming takes place in an aqueous liquor, typically in so-called liming barrels or alternatively in liming reels. The hair and other non-leather parts of the skin are removed through the addition of process chemicals and the action of movement, and the skin is opened up ("opening up") by separating the collagen fibers. In this case, 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 for hair removal. Lime or other alkaline substances are usually added to open the skin.

By adding these substances, the pH in the liquor and in the skin usually rises to around 11.8 - 12.5. This leads to a significant alkaline swelling of the skin. Depending on the amount of water, product addition, exposure to movement and skin structure, this swelling of the skin varies in severity. Strong alkaline swelling in connection with the drum/reel movement leads to quality losses in the finished leather in the form of pronounced growth marks or lime draw in loosely structured skin areas. Scar swelling is reduced by using swelling regulators, so that pronounced skin marks and scarring can be avoided. However, a strong reduction in swelling usually has the disadvantage of increased loose scarring in the loosely structured areas of the skin, 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 of the grain, i.e. poorer tightness of the grain.

In the prior art, mostly ethanolamines and sometimes also sugar (eg molasses) are used as swelling regulators, although the latter have to be used in relatively large amounts 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 liquor or the liquors of the subsequent processes (e.g. deliming). The addition of all process chemicals thus ultimately leads to an increase in the dirt load of the wastewater.

The requirements for avoiding waste water and reducing pollution loads have increased steadily in recent years and will probably become more stringent. In addition to high COD levels, the additional input of nitrogen in particular leads to capacity bottlenecks in the sewage treatment plants. Therefore, the reduction of both nitrogen and COD input is a continuous focus of development in the leather auxiliaries industry. However, for quality reasons, these aminoethanol and molasses-containing products cannot currently be dispensed with, despite the poorer wastewater values. They can therefore be found in almost all tanneries in the world.

Yuhanf Zeng et al.: "A Cleaner Deliming Process Using Sodium Gluconate for Reduction in Nitrogen Pollution in Leather Manufacture", JALCA, Vol 113, 2018, pages 19 to 25 , describes a formulation containing sodium gluconate, ammonium sulfate and citric acid for environmentally friendly deliming of limed animal skins.

CH 647 259 and DE 39 03 499 disclose a use of sodium gluconate in a tanning solution containing an iron salt or titanium and aluminum ions.

CN 107 653 350 A describes a formulation for leather coloring containing sodium gluconate.

Against this background, there was a need for alternative swelling regulators that avoid the disadvantages of the prior art and have a balanced property profile with regard to swelling and tight graining of the leather to be produced on the one hand and nitrogen or COD entry into the waste water on the other. Surprisingly, it has now been found that the object of the invention is achieved by using pseudoalkali metal, alkali metal and/or alkaline earth metal salts of sugar acids in leather production, when using these substances as swelling regulators in the soak, in the liming or in the soak and in the liming, especially in the ash.

Ammonium, sodium, potassium, calcium and/or magnesium salts of 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.

Saccharic acids are polyhydroxycarboxylic acids that are formed from simple sugars (monosaccharides) by oxidation. These include aldonic acids (e.g. D-gluconic acid), uronic acids (e.g. D-glucuronic acid), aldaric acids (e.g. D-glucaric acid, D-threaric acid, D-mannosugar acid) and ketoaldonic acids (e.g. D-2-oxo-gluconic acid).

In the present use according to the invention, preference is given to using ammonium, sodium, potassium, calcium and/or magnesium salts of aldonic acids, particularly preferably D-gluconic acid.

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

Pseudo-alkali metal salts are understood to mean salts whose cations are not alkali metals but behave largely 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 sugar acid salts 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 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 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 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, the salts of sugar acids according to the invention can be used in combination with alkali metal salts of C ₁ -C ₃ carboxylic acids, in particular sodium formate, sodium acetate, sodium propionate, potassium formate, potassium acetate and/or potassium propionate, which can certainly 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 methods as defined in claim 9 for treating animal hides in liming using pseudoalkali metal, alkali metal and/or alkaline earth metal salts of sugar acids, these being added to the liquor in which the hides are treated. 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 liming in the soak.

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

The present invention also relates to processes for the production of leather as defined in claim 10, including the treatment of animal hides according to the invention. Said methods can also include leather production steps familiar to the person skilled in the art, such as soaking, fleshing, splitting, deliming, enzymatic bating, degreasing, pickling, tanning, dewatering, folding, bleaching, retanning, dyeing, fatliquoring, stretching out, drying, moistening, softening and dry dressing.

Tanning is preferably carried out with mineral tanning agents such as aluminum salts, in particular alum, 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. Tanning is particularly preferably carried out with trivalent chromium salts or syntans. Tanning is most preferably 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 according to the invention of salts of sugar acids, since this can reduce the introduction of nitrogen into the waste water.

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

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

The tanner understands the salt weight to be the weight that the skin has after it has been preserved 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 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 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 additive compositions containing one or more pseudoalkali metal, alkali metal and/or alkaline earth metal salts of sugar acids, preferably ammonium, sodium and/or potassium salts of sugar acids, particularly preferably sodium salts of sugar acids.

Advantageously, leather auxiliary compositions according to the invention 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, the leather auxiliary compositions additionally containing one or more compounds from the group containing alkaline earth metal salts of C _{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, especially preferably magnesium and/or calcium salts of formic or acetic acid and most preferably calcium formate.

Other advantageous leather auxiliary compositions mentioned 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 containing calcium formate and magnesium formate, preferably calcium formate.

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

Typically, the leather auxiliary compositions according to the invention are swell regulators, in particular swell regulators for the water workshop, preferably swell regulators for use in soaking or liming, most preferably swell regulators for use in liming.

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 in the form of a solid at 25° C., ideally in particulate form, such as, for example, powder, granules or pellets.

examples Sample preparation:

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

The test procedure included the process steps "soaking" and "liming". The amounts of chemicals and products used in the process, as well as the amount of water, are percentages by weight based on the rawhide salt weight of each sample. The amounts were weighed on a scale with an accuracy of 0.5 g.

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

Soft:

The specimens were placed individually in 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. The specimen was then dabbed off, weighed and the average thickness determined at four measuring points.

liming:

The specimen was placed back into the test barrel and 200% water at a temperature of 28°C was added and rotated for 15 minutes. The remaining salt content of the liquor was then determined. This should not exceed 3.5°Bé. If the salt content is too high, the liquor must be changed once.

The swelling regulator was added to the liquor and the test barrel was rotated for 60 minutes. It was then weighed and the average thickness determined. The specimen was placed back in the float, 3% lime (Ca(OH) ₂ ) and 2.5% Na ₂ S added and rotated for 4 hours. This was followed by 15 hours of drum rotation at intervals (rotate 10 minutes/pause 50 minutes). The pH of the liquor was then measured (pH 12-12.5), the specimen is removed, weighed again and the average thickness measured. The swelling was determined from the increase in thickness.

The specimens were then washed and subjected to 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 the tightness of the grain was tested by bending the leather. If the surface in the bending fold was smooth, did not warp or curl, a positive grain tightness was judged.

The results of the swelling measurement and the assessment of the tightness of the scar are listed in Table 1.

The results show that the use of salts of sugar acids according to the invention makes it possible to dispense with the use of nitrogenous compounds, such as urea or ethanolamines, which means that the nitrogen input into the waste water can be significantly reduced, but at the same time the firm grain is maintained or improved can. The results also show that when salts of sugar acids are used according to the invention together with nitrogen-containing compounds such as urea or ethanolamines, ie with constant nitrogen input into the waste water, a significant improvement in the firm grain can be achieved. Table 1 No. additive % additive Thickness before (mm) Thickness after (mm) swelling (mm) swelling (%) Firm grain (crust) 1 0 without 3.1 5.8 2.7 87% ○ 2 0.5 urea 2.7 5.0 2.3 85% ○ 3 0.5 sodium sulfate 3.3 5.7 2.4 73% ○ 4 0.5 sodium acetate 3 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 2 24% ethanolamines 4 6.2 2.2 55% + 8th 0.5 calcium formate 3.4 5.4 2 59% ○ 9 1 calcium formate 3.4 5.0 1.6 47% ○ 10 0.5 magnesium formate 5.2 7.5 2.3 44% ○ 11 0.8 sodium gluconate 4 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 4 6.0 2 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 3 60% + 70% urea 16 0.5 10% magnesium acetate 3.2 5.2 2 63% + 20% sodium gluconate 70% calcium formate 17 0.5 70% sodium gluconate 5.2 7.7 2.5 48% + 30% magnesium formate 18 0.5 30% sodium gluconate 5.3 7.7 2.4 45% ++ 70% magnesium formate 19 0.5 70% sodium gluconate 4.9 7 2.1 43% +++ 30% calcium formate 20 0.5 30% sodium gluconate 5 7 2 40% ++ 70% calcium formate 21 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 (14)

1. Use of pseudo-alkali metal salts, alkali metal salts and/or alkaline earth metal salts of the sugar acids in leathermaking in soaking, in liming or in soaking and in liming.
2. Use according to Claim 1, where compounds selected from the group of ammonium, sodium, potassium, calcium and magnesium salts of the sugar acids, preferably sodium and potassium salts of the sugar acids, more preferably sodium salts of the sugar acids, are employed.
3. Use according to either or both of Claims 1 and 2, where salts of aldonic acids, uronic acids, aldaric acids or ketoaldonic acids, preferably of aldonic acids and more preferably of gluconic acid, are employed.
4. Use according to one or more of Claims 1 to 3, where ammonium, sodium and/or potassium gluconate, preferably sodium and/or potassium gluconate and more preferably sodium gluconate, is employed.
5. Use according to one or more of Claims 1 to 4 as a swelling regulator in liming.
6. Use according to one or more of Claims 1 to 5, where the use takes place together with alkaline earth metal salts of C₁-C₃ carboxylic acids, preferably magnesium salts and/or calcium salts of formic, acetic or propionic acid, more preferably magnesium salts and/or calcium salts of formic acid, and most preferably with calcium formate.
7. Use according to one or more of Claims 1 to 6, where the use takes place together with monoethanolamine, diethanolamine, triethanolamine or urea.
8. Use according to one or more of Claims 1 to 7, where, based on the salt weight of the untreated hide employed, defined as the weight possessed by the hide after preservation with salt, at a moisture content of 35 wt%, from 0.05 to 5.0 wt%, preferably from 0.1 to 2.0 wt% and more preferably from 0.2 to 1.0 wt%, of pseudo-alkali metal salts, alkali metal salts and/or alkaline earth metal salts of the sugar acids are used.
9. Method for treating animal hides in liming using pseudo-alkali metal salts, alkali metal salts and/or alkaline earth metal salts of the sugar acids, according to one or more of Claims 1 to 8, where the pseudo-alkali metal salts, alkali metal salts and/or alkaline earth metal salts of the sugar acids are added to the liquor in which the hides are treated.
10. Method for producing leather, comprising the treatment according to Claim 9.
11. Leather assistant composition comprising one or more pseudo-alkali metal salts, alkali metal salts and/or alkaline earth metal salts of sugar acids, further comprising one or more compounds from the group containing alkaline earth metal salts of C₁-C₃ carboxylic acids, monoethanolamine, diethanolamine, triethanolamine and urea, preferably magnesium and/or calcium salts of formic, acetic or propionic acid, monoethanolamine, diethanolamine, triethanolamine and urea, more preferably magnesium and/or calcium salts of formic or acetic acid, and most preferably calcium formate.
12. Leather assistant composition according to Claim 11, in which the pseudo-alkali metal salts, alkali metal salts and/or alkaline earth metal salts of the sugar acids are ammonium, sodium and/or potassium salts of the sugar acids, more preferably sodium salts of the sugar acids; and/or comprising one or more pseudo-alkali metal salts, alkali metal salts and/or alkaline earth metal salts of gluconic acid, preferably ammonium, sodium and/or potassium gluconate, more preferably sodium gluconate.
13. Leather assistant composition according to either or both of Claims 11 and 12, comprising sodium gluconate and one or more compounds from the group containing calcium formate and magnesium formate, preferably calcium formate.
14. Leather assistant composition according to either or both of Claims 11 and 13, where the ratio of the pseudo-alkali metal salts, alkali metal salts and/or alkaline earth metal salts of the sugar acids to the compounds from the group containing alkaline earth metal formates, alkaline earth metal acetates, alkaline earth metal propionates, monoethanolamine, diethanolamine, triethanolamine and urea is from 10:90 to 90:10, preferably from 20:80 to 80:20 and more preferably from 30:70 to 70:30.