A polyhydroxy complex tanning agent, its preparation method and application

Abstract

The application discloses a kind of polyhydroxy complex tanning agent and its preparation method and application, belong to leather tanning technical field.The polyhydroxy complex tanning agent disclosed in the application uses polyethylene glycol as polyhydroxy polymer, and the polyhydroxy polymer contains rich hydroxyl groups, which synergistically acts with the remaining ingredients, has certain masking effect, slows down the combination rate of metal ion zirconium on the skin surface, and the weight average molecular weight is 1000g / mol-5000g / mol, which ensures the uniform penetration of the tanning agent in the hide, thereby improving the absorption rate, ensuring the uniformity of distribution, and improving the tanning efficiency.The application of the polyhydroxy complex tanning agent in leather tanning produces leather with fine grain, good shrinkage temperature and tensile strength, mild reaction conditions, simple operation, no secondary pollution during the process, and can be produced on a large scale.

Description

Technical Field

[0001] This invention belongs to the field of leather tanning technology, specifically relating to a polyhydroxy complex tanning agent, its preparation method, and its application. Background Technology

[0002] Tanning is a crucial step in transforming raw hides into leather products. Currently, chrome tanning agents remain the most widely used tanning agent due to their strong penetrating power and excellent leather-forming properties. However, the use of chrome tanning agents generates significant amounts of chromium-containing wastewater and solid waste, causing environmental pollution. Under certain conditions, trivalent chromium in the wastewater can easily be oxidized to hexavalent chromium, a potentially carcinogenic form, which, when released into the environment, can cause permanent harm to human health. This severely limits the use of chrome tanning agents. Therefore, the development and promotion of chrome-free tanning processes is currently a top priority for the leather industry.

[0003] Zirconium-tanned leather has a high shrinkage temperature, a white body, a tight grain, and a full hand feel. Its tanning effect is second only to chrome tanning agents. However, the ligand of zirconium in water ([Zr(H2O)]) 6～8 ] 4+ It is highly hydrolyzed, causing it to combine with the surface of raw hide too quickly, resulting in surface over-tanning and poor penetration of tanning agents. Aluminum-tanned leather is soft and light in color, but it is not resistant to washing and has low bonding strength with the leather collagen. Summary of the Invention

[0004] The purpose of this invention is to provide a polyhydroxy complex tanning agent, its preparation method, and its application, in order to solve the technical problem of weak binding and low tanning efficiency of existing aluminum tanning agents.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] This invention discloses a polyhydroxy complex tanning agent, wherein the components of the polyhydroxy complex tanning agent, by mass parts, include:

[0007] 50-100 parts of polyhydroxy polymer, 30-50 parts of magnesium oxide, 30-50 parts of trivalent aluminum salt, 60-100 parts of tetravalent zirconium salt, 300-600 parts of sodium carbonate aqueous solution, and the balance being water;

[0008] The polyhydroxy polymer is polyethylene glycol, and the weight-average molecular weight of the polyethylene glycol is 1000 g / mol to 4000 g / mol, and the polydispersity index is 1.5 to 3.

[0009] Furthermore, the trivalent aluminum salt is one of aluminum sulfate, aluminum chloride, or aluminum nitrate; the tetravalent zirconium salt is one of zirconium sulfate, zirconium chloride, or zirconium nitrate.

[0010] Furthermore, the weight-average molecular weight of the polyhydroxy complex tanning agent is 1000 g / mol to 5000 g / mol.

[0011] This invention also discloses a method for preparing the above-mentioned polyhydroxy complex tanning agent, comprising the following steps:

[0012] The polyhydroxy polymer and water were mixed evenly under heating conditions to obtain an initial polymer solution; magnesium oxide was added to the initial polymer solution and stirred to obtain mixed solution A; the pH value of mixed solution A was adjusted to obtain a polymer mixed solution.

[0013] Trivalent aluminum salt and tetravalent zirconium salt were added to water and stirred evenly to obtain a mixed salt solution. Anhydrous sodium carbonate solution was then added dropwise to the mixed salt solution to obtain mixed solution B. Mixed solution B was heated and the pH value was adjusted. Subsequently, it was filtered, dried and ground to obtain zirconium-aluminum mixed salt.

[0014] A zirconium-aluminum mixed salt was added to a polymer mixture solution and stirred to carry out the reaction. After the reaction was completed, a polyhydroxy complex tanning agent was obtained.

[0015] Further, when obtaining mixed solution A, the ratio of the polyhydroxy polymer, magnesium oxide and water is (50-100):(30-50):(100-600); when obtaining mixed solution B, the ratio of the trivalent aluminum salt, tetravalent zirconium salt and water is (30-50) parts:(60-100) parts:500 parts.

[0016] Adjust the pH of mixed solution A to 2-6.

[0017] Furthermore, when obtaining the initial polymer solution, the heating condition is water bath heating, and the temperature of the water bath heating is 30℃~50℃.

[0018] Further, the mixed solution B is heated and the pH value is adjusted to 8-12. The heating method is water bath heating, and the water bath heating temperature is 50℃-80℃. The drying method is freeze drying, and the freeze drying time is 24h-48h.

[0019] Further, the ratio of the zirconium-aluminum mixed salt to the polymer mixed solution by mass is (10-50):(700-3000); the reaction time is 1-24 hours.

[0020] The stirring time is 6h to 24h.

[0021] This invention also discloses the application of the above-mentioned polyhydroxy complex tanning agent in leather tanning, specifically including the following steps:

[0022] The mass of the sourdough was used as the baseline mass for leather tanning. 80%–250% of the baseline mass of water and 4%–10% of the baseline mass of sodium chloride were added to a 0.5%–2.5% baseline mass of sodium bicarbonate solution to obtain a mixed solution. The pH of the mixed solution was adjusted to 6.5–8.5. The sourdough was then placed in the solution and rotated. Subsequently, 1%–10% of a polyhydroxy complex tanning agent (based on the baseline mass) was added for tanning. During tanning, the pH was fixed at 6.5–8.5 using a 0.5%–2.5% sodium bicarbonate solution, the temperature was adjusted, and after rotation, tanned leather was obtained.

[0023] Further, the tanning agent is placed in the tanned leather and rotated for 30 minutes; the tanning time is 4 to 8 hours; the temperature for temperature adjustment is 40°C, and the rotation time is 2 hours.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] This invention discloses a polyhydroxy complex tanning agent, comprising a polyhydroxy polymer, magnesium oxide, trivalent aluminum salt, tetravalent zirconium salt, sodium carbonate aqueous solution, and water. Polyethylene glycol is used as the polyhydroxy polymer, which contains abundant hydroxyl groups. These hydroxyl groups work synergistically with the other components to exhibit a certain masking effect, slowing down the binding rate of zirconium ions on the hide surface. The weight-average molecular weight of 1000 g / mol to 5000 g / mol ensures uniform penetration of the tanning agent into the raw hide, thereby improving absorption rate, ensuring uniform distribution, and increasing tanning efficiency.

[0026] Furthermore, the multi-hydroxyl composite tanning agent disclosed in this invention has a large number of hydroxyl groups, which can form certain cross-links with amino, carboxyl and hydroxyl groups on the side chains of skin collagen, enhance the binding effect of aluminum salt on the surface of skin collagen, improve the cross-linking strength of aluminum ions inside skin collagen, and thus improve the quality of finished leather. Its components are green and environmentally friendly, do not contain chromium, and do not produce chromium-containing wastewater or chromium-containing solid waste after tanning, thus solving the pollution problem of traditional chromium tanning.

[0027] This invention also discloses a method for preparing the aforementioned polyhydroxy complex tanning agent. This method is simple to operate and consumes little energy. A zirconium-aluminum mixed salt is introduced into a mixed solution of the polyhydroxy polymer and magnesium oxide, and a multi-hydroxy complex tanning agent is obtained after a coordination reaction. The multi-hydroxy complex tanning agent obtained during the preparation process has abundant hydroxyl groups, which can effectively bind with skin collagen fibers, thereby carrying Zr into the interior of the skin collagen fibers and effectively slowing down the binding of Zr on the skin collagen surface. Furthermore, the molecular weight is moderate, ranging from 1000 g / mol to 5000 g / mol, ensuring uniform penetration of the tanning agent into the raw hide. The multi-hydroxy complex tanning agent obtained by this invention contains a large amount of the metal elements zirconium and aluminum. These metals can form covalent cross-links with active groups such as carboxyl groups on the side chains of skin collagen fibers, thereby improving tanning efficiency.

[0028] This invention also discloses the application of the above-mentioned polyhydroxy complex tanning agent in leather tanning. The resulting leather has a fine grain, good shrinkage temperature and tensile strength, mild reaction conditions, simple operation, no secondary pollution generated during the process, and can be produced on a large scale. Attached Figure Description

[0029] Figure 1 A comparison of shrinkage temperature diagrams of leather tanned with the polyhydroxy complex tanning agent prepared in this invention and pure raw leather. Detailed Implementation

[0030] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0031] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0032] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0033] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0034] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0035] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0036] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0037] Example 1

[0038] A method for preparing a polyhydroxy complex tanning agent includes the following steps:

[0039] S1: By mass, 50 parts of polyethylene glycol and 100 parts of water are mixed evenly in a water bath at 35°C to obtain an initial polymer solution; then 30 parts of magnesium oxide are added to the initial polymer solution and stirred evenly. The pH value of the initial polymer solution is adjusted to 2 with formic acid aqueous solution to obtain a polymer mixed solution.

[0040] S2: Mix 30 parts aluminum sulfate, 60 parts zirconium sulfate, and 500 parts deionized water to obtain a mixed salt solution. Then, add 300 parts of 2M anhydrous sodium carbonate solution dropwise to obtain a mixed solution. Heat the mixed solution to 50°C in a water bath, maintain the pH at 8 with sodium bicarbonate solution, and stir continuously for 6 hours. Then, filter, freeze-dry for 24 hours, and grind to obtain a zirconium-aluminum mixed salt.

[0041] S3: Add 10 parts of zirconium-aluminum mixed salt to 700 parts of polymer mixed solution and stir for 1 hour to obtain a polyhydroxy complex tanning agent.

[0042] Example 2

[0043] A method for preparing a polyethylene glycol zirconium aluminum complex tanning agent includes the following steps:

[0044] S1: By mass, 70 parts of polyethylene glycol and 400 parts of water are mixed evenly in a water bath at 35°C to obtain an initial polymer solution; then 40 parts of magnesium oxide are added to the initial polymer solution and stirred evenly. The pH value of the initial polymer solution is adjusted to 3 with formic acid aqueous solution to obtain a polymer mixed solution.

[0045] S2: 40 parts aluminum chloride, 70 parts zirconium nitrate, and 500 parts deionized water were stirred until homogeneous to obtain a mixed salt solution. Then, 400 parts of 2M anhydrous sodium carbonate solution were added dropwise to obtain a mixed solution. The mixed solution was heated to 60°C in a water bath, and the pH was maintained at 12 using sodium bicarbonate solution, with continuous stirring for 9 hours. The solution was then filtered, freeze-dried for 30 hours, and ground to obtain a zirconium-aluminum mixed salt.

[0046] S3: Add 20 parts of zirconium-aluminum mixed salt to 1000 parts of polymer mixed solution and stir for 7 hours to obtain a polyhydroxy complex tanning agent.

[0047] Example 3

[0048] A method for preparing a polyethylene glycol zirconium aluminum complex tanning agent includes the following steps:

[0049] S1: By mass, 80 parts of polyethylene glycol and 500 parts of water are mixed evenly in a water bath at 40°C to obtain an initial polymer solution; then 45 parts of magnesium oxide are added to the initial polymer solution and stirred evenly. The pH value of the initial polymer solution is adjusted to 4 with formic acid aqueous solution to obtain a polymer mixed solution.

[0050] S2: 45 parts aluminum nitrate, 80 parts zirconium sulfate, and 500 parts deionized water were stirred until homogeneous to obtain a mixed salt solution. Then, 500 parts of 2M anhydrous sodium carbonate solution were added dropwise to obtain a mixed solution. The mixed solution was heated to 70°C in a water bath, and the pH was maintained at 9.5 using sodium bicarbonate solution, with continuous stirring for 12 hours. The solution was then filtered, freeze-dried for 35 hours, and ground to obtain a zirconium-aluminum mixed salt.

[0051] S3: Add 30 parts of zirconium-aluminum mixed salt to 1500 parts of polymer mixed solution and stir for 10 hours to obtain a polyhydroxy complex tanning agent.

[0052] Example 4

[0053] A method for preparing a polyethylene glycol zirconium aluminum complex tanning agent includes the following steps:

[0054] S1: By mass, 100 parts of polyethylene glycol and 600 parts of water are mixed evenly in a water bath at 50°C to obtain an initial polymer solution; then 50 parts of magnesium oxide are added to the initial polymer solution and stirred evenly. The pH value of the initial polymer solution is adjusted to 6 with formic acid aqueous solution to obtain a polymer mixed solution.

[0055] S2: Mix 50 parts aluminum sulfate, 100 parts zirconium chloride, and 500 parts deionized water to obtain a mixed salt solution. Then, add 600 parts of 2M anhydrous sodium carbonate solution dropwise to obtain a mixed solution. Heat the mixed solution to 80°C in a water bath, maintain the pH at 10 with sodium bicarbonate solution, and stir continuously for 24 hours. Then, filter, freeze-dry for 48 hours, and grind to obtain zirconium-aluminum mixed salt.

[0056] S3: Add 50 parts of zirconium-aluminum mixed salt to 3000 parts of polymer mixed solution and stir for 24 hours to obtain a polyhydroxy complex tanning agent.

[0057] Application Example 1

[0058] First, weigh the acid leather as the baseline mass for leather tanning. Then, add sodium chloride and water to the drum, with the water mass being 100% of the baseline mass and the sodium chloride mass being 8% of the baseline mass. Add the baseline 0.5% sodium bicarbonate aqueous solution to adjust the pH of the bath in the drum to 6.5. Place the acid leather in the drum and rotate for 30 minutes. Next, add the baseline 10% of the polyhydroxy complex tanning agent prepared in Example 1 to the bath and tan for 4 hours. Maintain the pH at 6.5 with sodium bicarbonate aqueous solution, adjust the temperature to 40°C, and rotate for 2 hours to obtain tanned leather.

[0059] Application Example 2

[0060] First, weigh the acid leather as the baseline mass for leather tanning. Then, add sodium chloride and water to the drum, with the water mass being 80% of the baseline mass and the sodium chloride mass being 6% of the baseline mass. Add the baseline 1.0% sodium bicarbonate aqueous solution to adjust the pH of the bath in the drum to 7.0. Place the acid leather in the drum and rotate for 30 minutes. Next, add the baseline 5% of the polyhydroxy complex tanning agent prepared in Example 2 to the bath and tan for 5 hours. Maintain the pH at 7.0 with sodium bicarbonate aqueous solution, adjust the temperature to 40°C, and rotate for 2 hours to obtain tanned leather.

[0061] Application Example 3

[0062] First, weigh the acid leather as the baseline mass for leather tanning. Then, add sodium chloride and water to the drum, with the water mass being 200% of the baseline mass and the sodium chloride mass being 4% of the baseline mass. Add the baseline 1.5% sodium bicarbonate aqueous solution to adjust the pH of the bath in the drum to 7.5. Place the acid leather in the drum and rotate for 30 minutes. Next, add the baseline 7% of the polyhydroxy complex tanning agent prepared in Example 3 to the bath and tan for 7 hours. Maintain the pH at 7.5 with sodium bicarbonate aqueous solution, adjust the temperature to 40°C, and rotate for 2 hours to obtain tanned leather.

[0063] Application Example 4

[0064] First, weigh the acid leather as the baseline mass for leather tanning. Then, add sodium chloride and water to the drum, with the water mass being 250% of the baseline mass and the sodium chloride mass being 10% of the baseline mass. Add the baseline 2.0% sodium bicarbonate aqueous solution to adjust the pH of the bath in the drum to 8.5. Place the acid leather in the drum and rotate for 30 minutes. Next, add the baseline 8% of the polyhydroxy complex tanning agent prepared in Example 4 to the bath and tan for 8 hours. Maintain the pH at 8.5 with sodium bicarbonate aqueous solution, adjust the temperature to 40°C, and rotate for 2 hours to obtain tanned leather.

[0065] Figure 1The graph shows the shrinkage temperatures of leather and untanned leather after tanning with the polyhydroxyl complex tanning agents prepared in Examples 1, 2, 3, and 4. In the graph, 1 represents Example 1, 2 represents Example 2, 3 represents Example 3, and 4 represents Example 4. As can be seen from the graph, when the polyethylene glycol zirconium aluminum complex tanning agent prepared in Example 2 is applied to leather tanning, the shrinkage temperature of the leather sample tanned with the polyhydroxyl complex tanning agent can be increased by approximately 35°C or more compared to untanned leather, demonstrating better resistance to damp heat.

[0066] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a polyhydroxy complex tanning agent, characterized in that, Includes the following steps: The polyhydroxy polymer and water were mixed evenly under heating conditions to obtain an initial polymer solution; magnesium oxide was added to the initial polymer solution and stirred to obtain mixed solution A; the pH value of mixed solution A was adjusted to obtain a polymer mixed solution. Adjust the pH of mixed solution A to 2-6; Trivalent aluminum salt and tetravalent zirconium salt were added to water and stirred evenly to obtain a mixed salt solution. Sodium carbonate aqueous solution was then added dropwise to the mixed salt solution to obtain mixed solution B. Mixed solution B was heated and the pH value was adjusted. Subsequently, it was filtered, dried and ground to obtain zirconium-aluminum mixed salt. A zirconium-aluminum mixed salt was added to a polymer mixture solution and stirred to carry out the reaction. After the reaction was completed, a polyhydroxy complex tanning agent was obtained. When the initial polymer solution is obtained, the heating condition is water bath heating, and the temperature of the water bath heating is 30 ℃~50 ℃; The mixed solution B is heated and the pH value is adjusted to 8-12. The heating method is water bath heating, and the water bath heating temperature is 50 ℃-80 ℃. The drying method is freeze drying, and the freeze drying time is 24 h-48 h. The ratio of the zirconium-aluminum mixed salt to the polymer mixed solution by mass parts is (10~50):(700~3000); the reaction time is 1 h~24 h. The composition of the polyhydroxy complex tanning agent, by mass parts, is as follows: The mixture comprises 50-100 parts of a polyhydroxy polymer, 30-50 parts of magnesium oxide, 30-50 parts of a trivalent aluminum salt, 60-100 parts of a tetravalent zirconium salt, 300-600 parts of a sodium carbonate aqueous solution, and an appropriate amount of water. The appropriate amount of water means that the amount of water used, by mass fraction, is such that when a mixed solution A is obtained, the ratio of the polyhydroxy polymer, magnesium oxide, and water is (50-100):(30-50):(100-600); when a mixed solution B is obtained, the ratio of the trivalent aluminum salt, tetravalent zirconium salt, and water is (30-50) parts:(60-100) parts:500 parts. The polyhydroxy polymer is polyethylene glycol, and the weight-average molecular weight of the polyethylene glycol is 1000 g / mol to 4000 g / mol, and the polydispersity index is 1.5 to 3. The trivalent aluminum salt is one of aluminum sulfate, aluminum chloride, or aluminum nitrate; the tetravalent zirconium salt is one of zirconium sulfate, zirconium chloride, or zirconium nitrate.

2. The application of the polyhydroxy complex tanning agent prepared by the method of claim 1 in leather tanning, characterized in that, Specifically, the following steps are included: The mass of the sourdough is used as the baseline mass for leather tanning. 80% to 250% of the baseline mass of water and 4% to 10% of the baseline mass of sodium chloride are added to a 0.5% to 2.5% sodium bicarbonate solution to obtain a mixed solution. The pH of the mixed solution is adjusted to 6.5 to 8.

5. The sourdough is then placed in the solution and rotated. Subsequently, 1% to 10% of a polyhydroxy complex tanning agent (based on the baseline mass) is added for tanning. During tanning, the pH is fixed at 6.5 to 8.5 using a 0.5% to 2.5% sodium bicarbonate solution. The temperature is adjusted, and after rotation, tanned leather is obtained.

3. The application in leather tanning according to claim 2, characterized in that, The tanning process involves placing the tanned leather in the container and rotating it for 30 minutes; the tanning time is 4 to 8 hours; the temperature for temperature adjustment is 40 °C, and the rotation time is 2 hours.

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