Method for tanning without chromium

Abstract

The invention relates to a method for tanning hide without using chromium as a tanning agent, which uses a nanometric tanning additive and which enables reduced usage, as well as improved quality, of processing water used during the hide tanning process in comparison with tanning using chromium.

Description

[0001] CHROMIUM-FREE TANNING METHOD

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The present invention relates to the technical field of leather tanning. Specifically, it relates to a method of tanning leather without the use of chromium as a tanning agent.

[0004] BACKGROUND OF THE INVENTION

[0005] The leather tanning industry has long used chromium as a tanning agent due to its unique properties in providing stability and durability to the material. However, this traditional method faces a number of challenges and limitations that raise growing concerns about its environmental impact and consequences for human health.

[0006] The general process of chrome tanning of hides consists mainly of the following stages:

[0007] Cleaning (Wet or bank treatment): In this initial phase, residues such as salt, dirt, and meat are removed, and the hides, also known as leathers, are degreased. Depending on the intended end use, the top and bottom layers are separated by adjusting the thickness of the hide. However, very thin hides are not separated at this stage, as they have not yet been stabilized by the tanning process.

[0008] Tanning: During this essential phase, the protein structure of the hides is stabilized, giving them strength, durability against chemicals, and reducing their susceptibility to decomposition. This is where the hides undergo their transformation into leather. Historically, traditional methods such as chromium-based tanning or vegetable tanning have been used. If the hides were not separated during the initial cleaning stage, it is common to do so after the tanning process. At the end of this phase, chromium-tanned leather is called "wet-blue," while leather tanned with tannins, without chromium, is known as "wet-white." Leather obtained with vegetable tannins is known as "vegetable leather" or "veg-leather."

[0009] Retannage (Semi-finished): This is where the leather's essence is defined. It will be dyed to obtain the desired color and oiled to achieve softness and feel. This is the stage where the specific characteristics required for different end products, such as car seats, footwear, or clothing, are established. At this stage, the leather is considered semi-finished.

[0010] Fulling: After retanning, the leather may be subjected to a dry drum fulling process to further soften it. This action enhances the natural grain structure and gives the leather a softer, more natural finish. Leather treated in this way is known as "fulled" or "fulonado."

[0011] Finishing: This final stage involves the application of various surface treatments for protection, fashion effects, or improved feel. These treatments may include additional coatings, dyes, waxes, oils, or embossing. Once this process is complete, the leather is considered finished and ready for final use in product manufacturing.

[0012] Each of these stages contributes significantly to defining the specific characteristics of the leather, adapting it for a wide variety of end applications and ensuring its quality and functionality for diverse uses.

[0013] Although the chrome tanning method has been used to obtain fast and durable leather, it faces considerable challenges in both environmental and health terms. Tannery workers face health risks due to exposure to hexavalent chromium fumes and residues, which can cause respiratory problems and dermatitis, as well as long-term effects on the respiratory system and skin. The application of chromium in the tanning process involves additional washing and scraping steps to remove the resulting dyes. The long rinsing time for chrome-dyed leather (wet blue), which can range from 3 to 8 hours, not only consumes substantial amounts of energy but also increases operating costs.

[0014] The presence of hexavalent chromium, a highly toxic form of chromium, can be released during the manufacturing and handling of leather. These residues pose considerable health risks to workers in the tanning industry and threaten the integrity of the natural environment by contaminating soil and water.

[0015] The dependence on specific resources to obtain chromium and increasingly stringent regulations on its use have increased pressure on the tanning industry. This has led to the search for more sustainable and environmentally friendly alternatives.

[0016] Chromium tends to have limited dispersion during the tanning process, which leads to suboptimal use of the material and lower efficiency in terms of utilization of the chromium used.

[0017] In the state of the art, there are several alternatives to corm tanning of hides, however, all have limitations in their application and effectiveness, such as:

[0018] Vegetable Tanning: Although more environmentally friendly, vegetable tanning faces technical challenges, such as a potential decrease in the leather's durability and strength, as well as longer processing times and higher costs.

[0019] Aluminum Salt and Polymer Tanning: While aluminum salt and polymer tanning shows encouraging results, its large-scale application is restricted by issues of strength and durability of the treated leather, along with the availability and cost of raw materials. These alternatives, despite their advantages, have not yet fully overcome the technical and performance challenges associated with the conventional use of chromium. High operating costs and lower efficiency in terms of time and final product quality have hampered its widespread adoption in the leather tanning industry.

[0020] To address these problems in the state of the art, various patent documents such as CN108368558A, which describes a method for re-tanning hides from chromium-free tanned hides, which includes the steps of: contacting a hide previously tanned with vegetable tannins (wet-white) with a re-tanning mixture comprising 2% to 15%, by solid weight, of a polymer composition comprising amine functional units and acid functional units; and (b) applying a polymeric layer containing an acrylic copolymer with one or more metal transition elements, with a thickness of no more than 100 microns. This method allows re-tanning “Wet-White” type hides or those tanned with vegetable tannins, so it is possible to re-taen hides without the use of chromium; however, it is not a method that allows initially tanning a hide from a general riverbank or cleaning process without the use of leather.Likewise, this method uses an application of an acrylic polymer layer in conjunction with metallic transition elements, which constitutes an additional step to the methods for tanning leather, so this method does not allow for reducing the amount of time or water required to carry out the entire tanning process.

[0021] There is patent document CN109234476A, which describes a method for preparing chrome-free tanned leather, which consists of the steps of neutralizing and washing the raw leather, subsequently, a highly hydrophilic solvent is used for dehydration treatment and drying to obtain a highly dispersed leather fiber structure with high porosity, thereby forming a porous thermal insulation structure in a leather fiber network structure, which significantly improves the thermal stability of the leather; The highly dispersed leather fiber structure with high porosity is fixed by a hydrophobic surface treatment to obtain chrome-free tanned leather with a hydrophobic and highly dispersed leather fiber structure. This patent document describes the use of nanoparticles and high-density polymers that are added and mixed through the use of ultrasonic treatment.While this patent document describes a method for obtaining tanned hide without the use of chromium, it uses a specialized ultrasound technique, thus adding an additional processing step to traditional hide tanning treatments, so this method does not allow for reducing the amount of time required to fully tan the hide.

[0022] While most of the identified solutions use various types of mixtures and compounds other than chromium to tan or re-tan leather, none of the identified documents directly replaces the use of chromium in relation to its addition in traditional leather tanning processing processes, that is, it can be added as a compound in tumbling as is currently done in the addition of chromium salts in the chrome tanning process.

[0023] Therefore, in the state of the art, there is still no method for tanning leather that does not use chromium as a tanning material, which allows reducing the time of the general tanning method and which allows reducing consumption and improving the quality of the process water used for leather tanning.

[0024] OBJECTS OF THE INVENTION

[0025] It is therefore an object of the present invention to provide a method for the production of an additive for leather tanning.

[0026] Another object of the present invention is to provide an additive for leather tanning.

[0027] A further object of the present invention is to provide a method for tanning leather without the use of chromium. Yet another object of the present invention is to provide a method for tanning leather that allows for a reduction in the overall tanning process time compared to the chromium tanning process.

[0028] Yet another object of the present invention is to provide a method for tanning leather that allows for reducing overall water consumption.

[0029] A still further object of the present invention is to provide a method for tanning leather that allows improving the quality of the process water produced by the leather tanning process.

[0030] A still further object of the present invention is to obtain a tanned leather without the use of chromium.

[0031] BRIEF DESCRIPTION OF THE INVENTION

[0032] These and other objects are achieved by a method for the production of an additive for leather tanning, said method comprising the steps of: i) Adding softened, deionized, distilled, double-distilled or triple-distilled water in a proportion of 25-32% w / w weight / weight to a reaction tank; i) Selecting at least one oxide of general formula M20x and at least one organic acid of general formula nR-COOH where “x” and “n” can take values ​​from 1 to 4; iii) Adding to the reaction tank an oxide of general formula M20x with 40% solids in a proportion of 40-48% w / w weight / weight, to obtain a mixture; iv) Stirring said mixture at a speed of 25-30 Hz for 30-35 minutes; v) Add to the reaction tank an organic acid of general formula R-COOH in a proportion of 15%-20% w / w and stir at a speed of 40-45 Hz for 160-165 minutes; vi) Add ethyl alcohol to the reaction tank in a proportion of 0.5% and 1% w / w and stir at a speed of 40-45 Hz for 25-35 minutes; vii) Adjust the temperature between 20-80°C and maintain stirring for a time of 30 to 300 minutes and; viii) Remove the product from the previous mixture which has a general formula xR - C00. n M + nH + and has a particle size range between 300 nm and 800 nm. In a second aspect, the invention relates to a nanomethod leather tanning additive of the general formula xR - COO n M + nH + with a range of particle sizes between 300 nm-800 nm which allows tanning leather without the use of Chromium.

[0033] In a third aspect, the invention relates to a method for tanning leather without the use of chromium, wherein said method comprises the steps of: i) Selecting a hide for animal tanning for the tanning process among the common types used in the leather tanning industry, such as cow, calf, goat, pig, sheep, lamb and other exotic skins such as ostrich, crocodile or snake, considering the desired properties of the final leather; i) Carrying out the Ribera (cleaning) processes on the selected hide; iii) Placing the hide produced by the Ribera (cleaning) process inside a rotating drum; iv) Adding to the rotating drum a solution of the nanomethicone leather tanning additive of general formula xR - C00 n M + nH +at a ratio of 30% w / w per kilo of hide, maintaining a pH of 2.7, a temperature between 30-35°C and agitation at 10 rpm for 1.5 h to allow penetration and stabilization of the hide fibers; v) Adjust the pH to 6 using a mixture of Sodium Bicarbonate at a ratio of 0.5% w / w per kilo of hide and Calcium Carbonate at 0.8% w / w per kilo of hide, for 1.5 hours at 10 rpm to promote fiber closure and fixation of the additive within the hide and; vi) Remove the tanned hide from the rotating drum.

[0034] The additional features and advantages of the invention should be more clearly understood by the detailed description of the preferred embodiment thereof, given by means of a non-limiting example with reference to the attached figures, in which:

[0035] BRIEF DESCRIPTION OF THE FIGURES

[0036] Figure 1 is a comparison image showing the percentage of shrinkage of a bovine hide tanned with chromium and another hide tanned using the nanomethco leather tanning additive. Figure 2 is a comparison table showing the percentage of weight gain of a bovine hide tanned with chromium and another hide tanned using the nanomethco leather tanning additive.

[0037] Figure 3 is a comparative image showing the increase in thickness of a rawhide sample, a product of Ribera's work (Cleaning) compared to a sample of leather tanned using the nanométhco leather tanning additive.

[0038] DETAILED DESCRIPTION OF THE INVENTION

[0039] The first aspect of the present invention relates to a method for the production of an additive for leather tanning, where the properties and advantages of the present invention will be evident to a person skilled in the art from its manufacturing method, which is made up of the following main stages: i) Add softened, deionized, distilled, double-distilled or th-distilled water to a reaction tank in a proportion of 25-32% w / w weight / weight;

[0040] ¡i) Select at least one oxide of general formula M2Ox and at least one organic acid of general formula nR-COOH where “x” and “n” can take values ​​from 1 to 4; iii) Add to the reaction tank an oxide of general formula M2Ox with 40% solids in a proportion of 40-48% w / w weight / weight, to obtain a mixture; iv) Stir said mixture at a speed of 25-30 Hz for 30-35 minutes; v) Add to the reaction tank an organic acid of general formula R-COOH in a proportion of 15%-20% w / w and stir at a speed of 40-45 Hz for 160-165 minutes; vi) Add ethyl alcohol to the reaction tank in a proportion of 0.5% and 1% w / w and stir at a speed of 40-45 Hz for 25-35 minutes; vii) Adjust the temperature between 20-80°C and maintain stirring for a time of 30 to 300 minutes and; viii) Remove the product from the previous mixture which has a general formula xR - C00 n M + nH +and has a particle size range between 300 nm-800 nm.

[0041] In a second aspect, the invention relates to a nanometric leather tanning additive of general formula xR - C00 n M + nH + with a range of particle sizes between 300 nm-800 nm which allows tanning the leather without the use of Chromium, where the synthesis reaction is: nR — COOH S + M¿O X -> xR — C00 n M + nH +

[0042] In a third aspect, the invention relates to a method for tanning leather without the use of Chromium, wherein said method comprises the steps of: i) Selecting an animal tanning hide for the tanning process among the common types used in the leather tanning industry, such as cow, calf, goat, pig, sheep, lamb and other exotic skins such as ostrich, crocodile or snake, considering the desired properties of the final leather;

[0043] i) Carry out the Ribera (cleaning) processes on the selected hide; iii) Place the hide produced by the Ribera (cleaning) process inside a rotating drum; iv) Add to the rotating drum a solution of the nanometric leather tanning additive with the general formula xR - C00 n M + nH + at a ratio of 0.03-0.05% w / w per kilo of hide, maintaining a pH of 2.7, a temperature between 30-35°C and agitation at 10 rpm for 1.5 h to allow penetration and stabilization of the hide fibers; v) Adjust the pH to 6 using a mixture of Sodium Bicarbonate at a ratio of 0.5% w / w per kilo of hide and Calcium Carbonate at 0.8% w / w per kilo of hide, for 1.5 hours at 10 rpm to promote fiber closure and fixation of the additive within the hide and; vi) Remove the tanned hide from the rotating drum.

[0044] Regarding the present method for tanning leather using the nanometric leather tanning additive, it is important to mention that the tanned leather obtained at the end of the tanning method does not require additional washing compared to chrome tanning, which allows reducing not only the total time of the tanning process but also reduces the process water used in the method of the present invention.

[0045] The tanning mechanism achieved using the method and additive for nanometric leather tanning of the present invention is based on the interaction between the nanometric zinc particles and the specific functional groups of the collagen proteins present in the leather. At the molecular level, this interaction occurs directly with the carboxyl and amide groups of collagen. The carboxyl groups present in the amino acid residues of the collagen chains form covalent bonds and electrostatic interactions with the additive nanoparticles. In the case of amides, the additive particles interact with these groups through electrostatic forces and coordination bonds, thus contributing to the modification of the molecular structure of the collagen proteins.These types of interactions are stable mainly due to the regular size (300-800nm) and the surface properties of the nanometric leather tanning additive particles, which achieves surface adsorption on the collagen fibers, partially modifying their three-dimensional structure and therefore the typical properties of a leather tanned by another method such as chrome tanning.

[0046] In order to demonstrate the capabilities of the additive and the method for tanning leather as a substitute for chromium, of the present invention, the following physicochemical tests were carried out:

[0047] Shrinkage test.

[0048] The shrinkage test is a common assessment for determining the tanning quality of hides. This test involves subjecting a tanned hide sample to a controlled shrinkage process to evaluate its ability to contract or shrink under specific conditions. The shrinkage of tanned hides can be indicative of the quality of the tanning process and the stability of its structure. The shrinkage test is performed by immersing a tanned hide sample in hot water at a defined temperature for a specified time. After this process, the shrinkage is measured in different directions of the sample, usually using a ruler or caliper to compare the dimensions before and after the test.A quality, well-tanned sample should exhibit minimal shrinkage during this test, suggesting a more stable molecular structure and less susceptibility to drastic changes in size and shape when exposed to water or humidity. Shrinkage testing is a useful method for evaluating the effectiveness of tanning and the leather's resistance to dimensional changes under specific conditions, providing information on its quality and structural stability.

[0049] In order to compare the shrinkage capacity exhibited by a hide tanned using the tanning method using nanometric zinc lactate as a tanning agent, the shrinkage test was performed on hides of bovine origin tanned using the chrome tanning method and tanned using the tanning method using nanometric zinc lactate of the present invention.

[0050] The Shrinkage test was carried out by cutting the leather tanned using the chrome tanning method (Sample A) and the tanning method using nanometric zinc lactate of the present invention (Sample B). A base template containing the precise measurements of the perimeter contour was then created before starting the test, both for the chrome tanned leather sample (A) and the leather sample tanned using nanometric zinc lactate (B). Each sample was then immersed in water for one minute, using an increase in water temperature with each immersion, starting at 65 S C, later 80 s C and finally 90 sC degrees. The objective of this test was to determine the leather's response to varying temperatures and evaluate its shrinkage capacity. The evaluation was carried out by comparing the sample dimensions before and after each immersion, compared to the initially established base template.

[0051] In relation to Figure 1, the samples of chrome tanned leather (Sample A) and using nanometric zinc lactate (Sample B) can be observed, after having been immersed in water at one-minute intervals, with temperature ranges of 65 S C, 80 s C and 90 sC. Sample A is the chrome-tanned sample, and Sample B is a sample of leather tanned with nanometer-sized zinc lactate. Both samples showed a shrinkage that did not exceed 3% in relation to the base template measured before starting the test. Since the shrinkage test parameters are within the established parameters for tanning using chrome and zinc lactate, it can be observed that the sample was tanned correctly and has a structure that gives it dimensional stability at specific temperatures. This evaluation is crucial and definitive to confirm the effectiveness of the tanning process using zinc lactate and the final quality of the leather, without the use of chromium.

[0052] Moisture absorption test by weight.

[0053] In this test, a tanned hide sample is immersed in water for a defined time and then removed to remove excess water remaining on the surface of the tanned hide. Once the surface water has been removed, the tanned hide sample is weighed immediately after removal from the water, and this initial weight is recorded. The sample is then allowed to dry at room temperature or under controlled conditions until it reaches a constant weight, indicating that it is no longer losing moisture. Finally, the sample is reweighed, and the dry weight is recorded. The difference between the initial and dry weights is used to calculate the percentage of water absorption by the sample during the test. This test provides a quantitative measure of the water absorption capacity of the tanned hide. A high-quality, well-tanned hide will show lower water absorption, indicating a more closed and moisture-resistant structure.On the other hand, a high percentage of water absorption may suggest deficiencies in the tanning process, such as a more open and water-permeable structure.

[0054] In order to compare the water absorption capacity exhibited by a hide tanned using the tanning method using nano-methicone zinc lactate as a tanning agent, a moisture absorption by weight test was performed on hides of bovine origin tanned using the chrome tanning method and tanned using the tanning method using nano-methicone zinc lactate of the present invention.

[0055] The moisture absorption by weight test was carried out by taking a cut of the leather tanned using the chrome tanning (Sample A) and the tanning using nanomethco zinc lactate (Sample B) of the present invention. Each sample was weighed using an analytical balance and the weight recorded for sample A was 90.78 g and for sample B it was 12.86 g. Subsequently, each sample was immersed in water for 1 h, maintaining a room temperature (25 s C-30 s C) from the immersion water. After 1 h, both samples were removed from the water and drained by gravity until the surface water present in each sample was eliminated. Finally, each sample was weighed again, and the recorded weight for sample A was 98.11 g, and for sample B it was 120.36 g.

[0056] In relation to Figure 2, we can observe a comparative table of the percentage of weight increase, where we can see how both samples showed a weight increase that did not exceed 15% in relation to the weight initially recorded and that obtained when performing the test, which indicates that tanning using Zinc Lactate (Sample B) is even more effective as a tanning additive than the use of Chromium (Sample A).

[0057] Post-tanning thickness test.

[0058] Comparing the thickness of raw and tanned hides is a technique used to assess the quality of the tanning process. This test focuses on measuring how the tanning process has affected the hide's thickness relative to its original untanned state. First, a raw hide sample is taken and its initial thickness is measured using a suitable measuring instrument. This sample then undergoes the specific tanning process. After tanning, the thickness of the treated hide sample is measured again. The difference in thickness between the raw and tanned hides is used to calculate the percentage change in thickness. A significant decrease in thickness after tanning may indicate excessive compression of the collagen fibers during the process, which in turn can negatively affect the leather's strength and durability.On the other hand, a positive change in thickness could suggest a more careful and controlled tanning process, better preserving the leather's natural structure. This thickness comparison provides valuable information on how the tanning process has physically affected the leather and can help determine the quality and suitability of the treatment for specific applications.

[0059] In order to know the tanning capacity using the tanning method using nanometre zinc lactate as a tanning agent, a post-tanning thickness test was performed on bovine hides tanned using the tanning method using nanometre zinc lactate of the present invention.

[0060] The post-tanning thickness test was carried out by making a cut of a bovine hide obtained from a riverbank process (cleaning) (Sample A) and a cut of said bovine hide tanned using nanometre zinc lactate of the present invention (Sample B). Both cuts were measured using a millimetric precision vernier caliper, obtaining thickness measurements for sample A of 2.7 mm and for sample B of 3.2 mm, thus observing an increase in thickness in the hide tanned using nanometre zinc lactate. In Figure 3, said increase in thickness can be observed, since the comparison in thickness of sample B overlaid with Sample A is shown, so that it can be identified that by using the tanning method using nanometre zinc lactate of the present invention, a greater thickness is obtained, which is indicative that the tanning method allows the natural structure of the leather to be adequately preserved.

[0061] Having described the invention in a general manner, below are some examples of the method for preparing the additive for tanning nanomethicone leather and of the method for tanning leather using nanomethicone zinc lactate, without chromium, as a tanning additive, which serves only as an illustration of the procedure and is not intended in any way to be limiting.

[0062] EXAMPLE

[0063] Example 1. Preparation of 1kg of nanometric Zinc Lactate additive for leather tanning: Add 0.25kg of deionized water to a reaction tank; Add 0.4kg of zinc oxide with 40% solids to the reaction tank; Stir said mixture at a speed of 25Hz for 30 minutes; Add 0.15kg of lactic acid to the reaction tank and stir at a speed of 40Hz for 160 minutes. Add 0.05kg of ethyl alcohol to the reaction tank and stir at a speed of 40Hz for 25 minutes; Adjust the temperature to 20 s C and continue stirring for 30 minutes. Remove the product from the previous mixture, which is zinc lactate (CeHiO2ZnOe) as a leather tanning additive with a particle size of 300 nm–800 nm.

[0064] Example 2. Tanning 1 Kg of bovine leather using Zinc Lactate as a tanning agent, without Chromium: Select a hide for tanning animal of bovine origin; Carry out the Ribera processes (cleaning) of the selected hide; Place 1 Kg of the hide product of the Ribera process (cleaning) inside a rotating drum; Add 0.3 Kg of a nanometric zinc lactate solution to the rotating drum in a proportion of maintaining a pH of 2.7, a temperature between 32 ° C and agitation of 10 rpm for a time of 1.5 h to allow penetration and stabilization of the hide fibers; Adjust the pH to 6 using a mixture of 0.05 kg of Sodium Bicarbonate and 0.08 kg of Calcium Carbonate, for 1.5 hours at 10 rpm to promote fiber closure and fixation of the nanometric zinc lactate additive within the hide and; Remove the tanned hide from the rotating drum.

[0065] Since various aspects of various embodiments of this invention have been described, it should be noted that various alterations, modifications, and improvements can be made by those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this description and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and the aforementioned figures are for exemplary purposes only.

Claims

MODIFIED CLAIMS received by the International Bureau on September 11, 2024

1. ] [Modified Method for the production of an additive for leather tanning characterized in that it comprises the steps of: i) Adding softened, deionized, distilled, double-distilled or triple-distilled water to a reaction tank in a proportion of 25-32% w / w weight / weight; ii) Selecting at least one oxide of general formula M20x and at least one organic acid of general formula "nR-COOH, where 'R' represents a short chain alkyl group (C1-C4) and 'n' is an integer from 1 to 4."; iii) Add to the reaction tank an oxide dispersion of general formula M20x with a concentration of 40% by mass, in a proportion of 40-48% w / w weight / weight, to obtain a mixture; iv) Stir said mixture at a speed in the range of 1500-1800 rpm for 30-35 minutes; v) Add to the reaction tank an organic acid of general formula R-COOH in a proportion of 15%-20% w / w and stir at a speed of 40-45 Hz for 160-165 minutes; vi) Add ethyl alcohol to the reaction tank in a proportion of 0.5% and 1% w / w and stir at a speed in the range of 2400-2700 rpm for 25-35 minutes; vii) Adjust the temperature between 20-80°C and maintain stirring for a time of 30 to 300 minutes and; viii) Remove the resulting product which has a general formula of xR-COOnM + nH and is a reaction compound obtained by neutralizing the oxide of general formula M20x and the organic acid of general formula nR- COOH and has a particle size range between 300 nm-800 nm.

2. The method for producing a leather tanning additive of claim 1 further characterized in that the water used is selected from the group consisting of: softened water, deionized water, distilled water, double-distilled water or triple-distilled water.

3. The method for producing an additive for leather tanning of claim 1 further characterized in that the oxide of general formula M2O xIt is selected from the group consisting of: barium oxide, cobalt oxide, zinc oxide, manganese oxide, nickel oxide, copper oxide, cadmium oxide, silicon dioxide, cerium oxide and aluminum oxide.

4. [Modified The method for the production of a leather tanning additive of claim 1 further characterized in that the organic acid of general formula nR-COOH is selected from the group consisting of: stearic acid, palmitic acid, lauric acid, myristic acid, citric acid, lactic acid and gluconic acid.

5. [Modified An additive for leather tanning characterized in that it comprises: a reaction compound of general formula xR-COOnM + nH with a range of particle sizes between 300 nm-800 nm, which is obtained by neutralizing an oxide of general formula M2Ox and an organic acid of general formula nR- COOH, where 'R' represents a short chain alkyl group (C1-C4) and 'n' is an integer from 1 to 4.

6. [Modified The use of the additive for tanning leather of claim 5 further characterized in that it allows tanning the leather without the use of Chromium, which is added to the tanning process in the order of 0.03%-0.05% based on the total weight of the treated leather.

7. [Modified Method for tanning leather without the use of Chromium, wherein said method comprises the steps of: i) Selecting an animal tanning hide for the tanning process from among the common types used in the leather tanning industry, such as cow, calf, goat, pig, sheep, lamb and other exotic skins such as ostrich, crocodile or snake, considering the desired properties of the final leather; ii) Carrying out the Ribera (cleaning) processes on the selected hide; iii) Placing the hide resulting from the Ribera (cleaning) process inside a rotating drum; v) Add to the rotating drum a solution of the general formula nanometric leather tanning additive [Math.] at a ratio of 0.03-0.05% w / w based on the total weight of the treated hide, maintaining a pH of 2.7, a temperature between 30-35°C and agitation at 10 rpm for a time of 1.5 h to allow penetration and stabilization of the hide fibers; v) Adjusting the pH to 6 using a mixture of Sodium Bicarbonate at a ratio of 0.5% based on the total weight of the treated hide and Calcium Carbonate at 0.8% w / w based on the total weight of the treated hide, for 1.5 hours at 10 rpm to promote fiber closure and fixation of the additive within the hide and; vi) Removing the tanned hide from the rotating drum.

8. The method for tanning leather without the use of Chromium of claim 7 further characterized in that the leather to be selected for tanning is selected from the group consisting of: animal skins of cow, calf, goat, pig, sheep, lamb and other exotic skins such as ostrich, crocodile or snake.

9. The method for tanning leather without the use of Chromium of claims 7 and 8, further characterized in that it allows reducing the consumption of process water compared to the Chromium tanning process.

10. The method for tanning leather without the use of Chromium of claims 7 to 9 further characterized in that it does not contaminate the process water used, compared to the Chromium tanning process.

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