Preparation method and application of ethylene glycol glycidyl ether modified tannic acid-based chrome-free tanning agent

Abstract

The invention discloses a preparation method and application of a low-tannic acid-based chrome-free tanning agent modified with ethylene glycol glycidyl ether. The phenolic hydroxyl groups of tannic acid are chemically cross-linked with the epoxy groups of ethylene glycol glycidyl ether to prepare a crude product mixed solution. A solid powder of the tannic acid-based chrome-free tanning agent modified with ethylene glycol glycidyl ether is obtained through liquid separation and vacuum drying. The chrome-free tanning agent is prepared using ethylene glycol glycidyl ether and tannic acid as raw materials. The preparation method is environmentally friendly and simple. The prepared chrome-free tanning agent is used in tanning experiments. Crust leather tanned with the tanning agent has a high shrinkage temperature, physical and mechanical properties, and water-washing resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of leather tanning, and particularly relates to a preparation method and application of a chrome-free tannic acid tanning agent modified with ethylene glycol glycidyl ether. Background Art

[0002] As a traditional light processing industry, the leather industry plays an irreplaceable and important role in improving the quality of life and promoting economic benefits. Leather manufacturing refers to the process of converting discarded animal fur resources into high-value-added leather products, such as clothing and car interiors, through a series of processes. Among them, the most important process is tanning, which is the process of converting raw hides into leather by cross-linking tanning agents with skin collagen fibers. In the leather making process, chrome tanning has always dominated leather production due to its excellent tanning properties. However, the chromium-containing wastewater, sludge and solid waste currently generated in the tanning process may lead to a series of ecological and environmental risks. And the chrome tanning agent used is Cr 3+ , which will be transformed into Cr during the processing 6+ Under certain conditions, it is carcinogenic to humans and harmful to human health. These factors have become a bottleneck restricting the development of leather, prompting us to seek and develop cleaner and greener chrome-free tanning agents. Summary of the Invention

[0003] In order to overcome the above-mentioned deficiencies of the prior art, the object of the present invention is to provide a preparation method and application of a tannic acid-based chrome-free tanning agent modified with ethylene glycol glycidyl ether.

[0004] To achieve the above object, the technical solution adopted by the present invention is:

[0005] The preparation method of ethylene glycol glycidyl ether modified tannic acid-based chrome-free tanning agent comprises the following steps:

[0006] Step S1, heating 2 g to 20 g of ethylene glycol glycidyl ether to obtain a heated ethylene glycol glycidyl ether solution;

[0007] Step S2, dissolving 5 g to 20 g of tannic acid in water, adding 60 mL to 100 mL of distilled water until completely dissolved to obtain a tannic acid solution, then adjusting the pH of the tannic acid solution to 8.0 to 10.0 with sodium hydroxide, then adding the pH-adjusted tannic acid solution to the heated ethylene glycol glycidyl ether solution, while maintaining the heating temperature unchanged, reacting, and adjusting the pH to obtain a mixed solution;

[0008] Step S3, cooling the mixed solution, removing unreacted ethylene glycol glycidyl ether and then vacuum drying to obtain a solid powder, which is the ethylene glycol glycidyl ether modified tannic acid-based chrome-free tanning agent.

[0009] In step S1, ethylene glycol glycidyl ether is heated to 40°C to 50°C.

[0010] In step S2, the tannic acid solution is added to the heated ethylene glycol glycidyl ether solution, and the heating temperature is maintained at 40° C. to 50° C. for a reaction of 2 h to 5 h.

[0011] In step S2, the pH value of the mixed solution is 5.5.

[0012] In step S3, the cooling temperature is reduced to room temperature, and vacuum drying is performed at 40° C. to obtain a solid powder.

[0013] The molecular weight of the tannic acid is 1000-2000.

[0014] The ethylene glycol glycidyl ether modified tannic acid-based chrome-free tanning agent prepared by the above preparation method.

[0015] The invention relates to an application of the ethylene glycol glycidyl ether modified tannic acid-based chrome-free tanning agent in leather tanning.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The preparation method of the present invention chemically crosslinks the phenolic hydroxyl groups of tannic acid with the epoxy groups of ethylene glycol glycidyl ether to produce a crude product mixture. After filtration and vacuum drying, a solid powder of a tannic acid-based chrome-free tanning agent modified with ethylene glycol glycidyl ether is obtained. The chrome-free tanning agent is prepared using ethylene glycol glycidyl ether (EGDE) and tannic acid (TA) as raw materials. The preparation method is simple and environmentally friendly. Tanning tests have shown that crust leather tanned with this tanning agent exhibits excellent shrinkage temperature, physical and mechanical properties, washability, and yellowing resistance. The chrome-free tanning agent of the present invention provides a new approach to clean and sustainable development in the leather industry. The preparation method is simple, environmentally friendly, and does not use toxic raw materials. The chrome-free tanning agent prepared can be used in chrome-free tanning systems to address the issue of chromium pollution in the leather industry. Crust leather tanned with TA-EGDE exhibits a high shrinkage temperature and excellent physical and mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the infrared spectrum of the epoxidized tannic acid-based chrome-free tanning agent prepared from ethylene glycol glycidyl ether, tannic acid and ethylene glycol glycidyl ether-modified tannic acid in the present invention.

[0019] Figure 2 This is the nuclear magnetic spectrum of tannic acid of the present invention.

[0020] Figure 3 This is the nuclear magnetic spectrum of the epoxidized tannic acid-based chrome-free tanning agent prepared by modifying tannic acid with ethylene glycol glycidyl ether in the present invention.

[0021] Figure 4 This is a comparison chart of the shrinkage temperature of leather tanned with the epoxidized tannic acid-based chrome-free tanning agent prepared from the medium-acid leather of the present invention, ethylene glycol glycidyl ether-modified tannic acid, F-90, and TWS chrome-free tanning agents.

[0022] Figure 5 This is a comparison chart of the mechanical properties of leather tanned with the epoxidized tannic acid-based chrome-free tanning agent prepared from the medium-acid leather of the present invention, ethylene glycol glycidyl ether-modified tannic acid, F-90, and TWS chrome-free tanning agents.

[0023] Figure 6 This is a comparison chart of the mechanical properties of leather tanned with the epoxy-modified low-tannic acid-based chrome-free tanning agent prepared by modifying tannic acid with ethylene glycol glycidyl ether in the present invention and the F-90 and TWS chrome-free tanning agents, as well as acid leather. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0025] The preparation method of ethylene glycol glycidyl ether modified tannic acid-based chrome-free tanning agent comprises the following steps:

[0026] Step S1, heating 2 g to 20 g of ethylene glycol glycidyl ether to obtain a heated ethylene glycol glycidyl ether solution;

[0027] Step S2, dissolving 5 g to 20 g of tannic acid in water, adding 60 mL to 100 mL of distilled water until completely dissolved to obtain a tannic acid solution, then adjusting the pH of the tannic acid solution to 8.0 to 10.0 with sodium hydroxide, then adding the pH-adjusted tannic acid solution to the heated ethylene glycol glycidyl ether solution, while maintaining the heating temperature unchanged, reacting, and adjusting the pH to obtain a mixed solution;

[0028] Step S3, cooling the mixed solution, removing unreacted ethylene glycol glycidyl ether and then vacuum drying to obtain a solid powder, which is the ethylene glycol glycidyl ether modified tannic acid-based chrome-free tanning agent.

[0029] In step S1, ethylene glycol glycidyl ether is heated to 40°C to 50°C.

[0030] In step S2, the tannic acid solution is added to the heated ethylene glycol glycidyl ether solution, and the heating temperature is maintained at 40° C. to 50° C. for a reaction of 2 h to 5 h.

[0031] In step S3, the cooling temperature is reduced to room temperature, and vacuum drying is performed at 40° C. to obtain a solid powder.

[0032] The molecular weight of the tannic acid is 1000-2000. Example

[0033] Step S1, heating 4 g of ethylene glycol glycidyl ether to 40° C. to obtain a heated ethylene glycol glycidyl ether solution;

[0034] Step S2: 10 g of tannic acid was placed in a 250 mL beaker, and then 60 mL of distilled water was added to dissolve the tannic acid solution. The pH of the tannic acid solution was adjusted to 8.0 with sodium hydroxide until the tannic acid solution was completely dissolved to obtain a tannic acid solution. The tannic acid solution was poured into a constant pressure separatory funnel.

[0035] 4 g of ethylene glycol glycidyl ether was added to a three-necked flask and heated in an oil bath at 40°C to obtain a heated ethylene glycol glycidyl ether solution. The constant pressure separatory funnel containing the tannic acid solution was then inserted into the three-necked flask. The tannic acid solution was slowly added dropwise to the three-necked flask under mechanical stirring. After the addition was complete, the mixture was reacted for 2.5 hours until the reaction was complete to form a mixed solution. The pH value of the mixed solution in the three-necked flask was adjusted to 5.5.

[0036] Step S3, cooling the mixed solution to room temperature, separating the liquid, removing unreacted ethylene glycol glycidyl ether, and vacuum drying at 40° C. to obtain ethylene glycol glycidyl ether modified tannic acid-based chrome-free tanning agent. Example

[0037] Step S1, heating 6 g of ethylene glycol glycidyl ether to 45° C. to obtain a heated ethylene glycol glycidyl ether solution;

[0038] Step S2: 10 g of tannic acid was placed in a 250 mL beaker, and then 60 mL of distilled water was added to dissolve it. The pH of the tannic acid solution was adjusted to 9.0 with sodium hydroxide until it was completely dissolved to obtain a tannic acid solution. The tannic acid solution was poured into a constant pressure separatory funnel;

[0039] 6 g of ethylene glycol glycidyl ether was added to a three-necked flask and heated in an oil bath at 45°C to obtain a heated ethylene glycol glycidyl ether solution. The constant pressure separatory funnel containing the tannic acid solution was then inserted into the three-necked flask. The tannic acid solution was slowly added dropwise to the three-necked flask under mechanical stirring. After the addition was complete, the mixture was reacted for 2.5 hours until the reaction was complete to form a mixed solution. The pH value of the mixed solution in the three-necked flask was adjusted to 5.5.

[0040] Step S3, cooling the mixed solution to room temperature, separating the liquid, removing unreacted ethylene glycol glycidyl ether, and vacuum drying at 40° C. to obtain ethylene glycol glycidyl ether modified tannic acid-based chrome-free tanning agent. Example

[0041] Step S1, heating 8 g of ethylene glycol glycidyl ether to 50° C. to obtain a heated ethylene glycol glycidyl ether solution;

[0042] Step S2: 10 g of tannic acid was placed in a 250 mL beaker, and then 60 mL of distilled water was added to dissolve it. The pH of the tannic acid solution was adjusted to 10.0 with sodium hydroxide until it was completely dissolved to obtain a tannic acid solution. The tannic acid solution was poured into a constant pressure separatory funnel;

[0043] 8 g of ethylene glycol glycidyl ether was added to a three-necked flask and heated in an oil bath at 50°C to obtain a heated ethylene glycol glycidyl ether solution. The constant pressure separatory funnel containing the tannic acid solution was then inserted into the three-necked flask. The tannic acid solution was slowly added dropwise to the three-necked flask under mechanical stirring. After the addition was complete, the mixture was reacted for 3 hours until the reaction was complete to form a mixed solution. The pH value of the mixed solution in the three-necked flask was adjusted to 5.5.

[0044] Step S3, cooling the mixed solution to room temperature, separating the liquid, removing unreacted ethylene glycol glycidyl ether, and vacuum drying at 40° C. to obtain ethylene glycol glycidyl ether modified tannic acid-based chrome-free tanning agent. Example

[0045] Step S1, heating 10 g of ethylene glycol glycidyl ether at 46° C. to obtain a heated ethylene glycol glycidyl ether solution;

[0046] Step S2: 20 g of tannic acid was placed in a 250 mL beaker, and 100 mL of distilled water was added to dissolve the tannic acid. The pH of the tannic acid solution was adjusted to 9.5 with sodium hydroxide until the tannic acid was completely dissolved to obtain a tannic acid solution. The tannic acid solution was poured into a constant pressure separatory funnel.

[0047] 10 g of ethylene glycol glycidyl ether was added to a three-necked flask and heated in an oil bath at 46°C to obtain a heated ethylene glycol glycidyl ether solution. The constant pressure separatory funnel containing the tannic acid solution was then inserted into the three-necked flask. The tannic acid solution was slowly added dropwise to the three-necked flask under mechanical stirring. After the addition was complete, the mixture was reacted for 3 hours until the reaction was complete to form a mixed solution. The pH value of the mixed solution in the three-necked flask was adjusted to 5.5.

[0048] Step S3, cooling the mixed solution to room temperature, separating the liquid, removing unreacted ethylene glycol glycidyl ether, and vacuum drying at 40° C. to obtain ethylene glycol glycidyl ether modified tannic acid-based chrome-free tanning agent. Example

[0049] Step S1, heating 5 g of ethylene glycol glycidyl ether to 44° C. to obtain a heated ethylene glycol glycidyl ether solution;

[0050] Step S2: 20 g of tannic acid was placed in a 250 mL beaker, and 100 mL of distilled water was added to dissolve the tannic acid. The pH of the tannic acid solution was adjusted to 9.5 with sodium hydroxide until the tannic acid was completely dissolved to obtain a tannic acid solution. The tannic acid solution was poured into a constant pressure separatory funnel.

[0051] 5 g of ethylene glycol glycidyl ether was added to a three-necked flask and heated in an oil bath at 44°C to obtain a heated ethylene glycol glycidyl ether solution. The constant pressure separatory funnel containing the tannic acid solution was then inserted into the three-necked flask. The tannic acid solution was slowly added dropwise to the three-necked flask under mechanical stirring. After the addition was complete, the mixture was reacted for 2.5 hours until the reaction was complete to form a mixed solution. The pH value of the mixed solution in the three-necked flask was adjusted to 5.5.

[0052] Step S3, cooling the mixed solution to room temperature, separating the liquid, removing unreacted ethylene glycol glycidyl ether, and vacuum drying at 40° C. to obtain ethylene glycol glycidyl ether modified tannic acid-based chrome-free tanning agent. Example

[0053] Step S1, heating 9 g of ethylene glycol glycidyl ether to 47° C. to obtain a heated ethylene glycol glycidyl ether solution;

[0054] Step S2: 20 g of tannic acid was placed in a 250 mL beaker, and 100 mL of distilled water was added to dissolve the tannic acid. The pH of the tannic acid solution was adjusted to 9.5 with sodium hydroxide until the tannic acid was completely dissolved to obtain a tannic acid solution. The tannic acid solution was poured into a constant pressure separatory funnel.

[0055] 9 g of ethylene glycol glycidyl ether was added to a three-necked flask and heated in an oil bath at 47°C to obtain a heated ethylene glycol glycidyl ether solution. The constant pressure separatory funnel containing the tannic acid solution was then inserted into the three-necked flask. The tannic acid solution was slowly added dropwise to the three-necked flask under mechanical stirring. After the addition was complete, the mixture was reacted for 2.5 hours until the reaction was complete to form a mixed solution. The pH value of the mixed solution in the three-necked flask was adjusted to 5.5.

[0056] Step S3, cooling the mixed solution to room temperature, separating the liquid, removing unreacted ethylene glycol glycidyl ether, and vacuum drying at 40° C. to obtain ethylene glycol glycidyl ether modified tannic acid-based chrome-free tanning agent. Example

[0057] Step S1, heating 13 g of ethylene glycol glycidyl ether at 42° C. to obtain a heated ethylene glycol glycidyl ether solution;

[0058] Step S2: 20 g of tannic acid was placed in a 250 mL beaker, and 100 mL of distilled water was added to dissolve the tannic acid solution. The pH of the tannic acid solution was adjusted to 9 with sodium hydroxide until the tannic acid solution was completely dissolved to obtain a tannic acid solution. The tannic acid solution was poured into a constant pressure separatory funnel.

[0059] 13 g of ethylene glycol glycidyl ether was added to a three-necked flask and heated in an oil bath at 42° C. to obtain a heated ethylene glycol glycidyl ether solution. The constant pressure separatory funnel containing the tannic acid solution was then inserted into the three-necked flask. The tannic acid solution was slowly added dropwise to the three-necked flask under mechanical stirring. After the addition was complete, the mixture was reacted for 3 hours until the reaction was complete to form a mixed solution. The pH value of the mixed solution in the three-necked flask was adjusted to 5.5.

[0060] Step S3, cooling the mixed solution to room temperature, separating the liquid, removing unreacted ethylene glycol glycidyl ether, and vacuum drying at 40° C. to obtain ethylene glycol glycidyl ether modified tannic acid-based chrome-free tanning agent. Example

[0061] Step S1, heating 17 g of ethylene glycol glycidyl ether to 49° C. to obtain a heated ethylene glycol glycidyl ether solution;

[0062] Step S2: 20 g of tannic acid was placed in a 250 mL beaker, and 100 mL of distilled water was added to dissolve the tannic acid. The pH of the tannic acid solution was adjusted to 9 with sodium hydroxide until the tannic acid was completely dissolved to obtain a tannic acid solution. The tannic acid solution was poured into a constant pressure separatory funnel.

[0063] 17 g of ethylene glycol glycidyl ether was added to a three-necked flask and heated in an oil bath at 49°C to obtain a heated ethylene glycol glycidyl ether solution. The constant pressure separatory funnel containing the tannic acid solution was then inserted into the three-necked flask. The tannic acid solution was slowly added dropwise to the three-necked flask under mechanical stirring. After the addition was complete, the mixture was reacted for 3 hours until the reaction was complete to form a mixed solution. The pH value of the mixed solution in the three-necked flask was adjusted to 5.5.

[0064] Step S3, cooling the mixed solution to room temperature, separating the liquid, removing unreacted ethylene glycol glycidyl ether, and vacuum drying at 40° C. to obtain ethylene glycol glycidyl ether modified tannic acid-based chrome-free tanning agent.

[0065] The tannic acid-based chrome-free tanning agent modified with ethylene glycol glycidyl ether prepared in the above example was used in the tanning process of sheep acid hides. Table 1 shows the specific operating procedures of the sheep acid hide tanning experiment using TA-EGDE.

[0066]

[0067] According to the process in Table 1, the tanning agents obtained in Examples 1, 2, 3 and 4 were used to tan sheep acid hides, and the tanning results were compared with leather tanned with commercially available tanning agents.

[0068] Figures 2 to 4The chrome-free tanning agent (TA-EGDE-1) prepared by modifying tannic acid with ethylene glycol glycidyl ether prepared in Example 1, tannic acid (TA) and ethylene glycol glycidyl ether (EGDE) were characterized by infrared and nuclear magnetic resonance respectively; see Figure 1 , visible, 835cm -1 The characteristic absorption peak of the terminal epoxy group of TA-EGDE-1 appears at Figures 2 to 3 , the typical characteristic peaks of epoxy groups appeared at 2.74ppm, 2.92ppm and 3.08ppm respectively. FTIR and 1 HNMR results showed that a tannic acid-based chrome-free tanning agent (TA-EGDE-1) modified with ethylene glycol glycidyl ether was successfully synthesized.

[0069] Figure 5 This chart compares the shrinkage temperatures of leather tanned with epoxy-modified low-tannic acid-based chrome-free tannins prepared with ethylene glycol glycidyl ether-modified tannic acid in Examples 1, 2, 3, and 4 of the present invention, and with F-90 and TWS chrome-free tannins. The thermal stability of leather reflects the degree of crosslinking between the tannin and the collagen in the leather. The Ts of crust leather tanned with the ethylene glycol glycidyl ether-modified tannic acid-based chrome-free tannin prepared in the present invention is higher than those tanned with F-90 and TWS tannins, indicating a better tanning effect.

[0070] Figure 6 The following is a comparison chart of the mechanical properties of leather tanned with epoxy-modified low-tannic acid-based chrome-free tanning agents prepared with ethylene glycol glycidyl ether modified tannic acid in Examples 1, 2, 3, and 4 of the present invention and leather tanned with F-90 and TWS chrome-free tanning agents, as well as acid leather. The mechanical strength of leather includes elongation at break, tensile strength, and tear strength. The physical and mechanical properties of leather determine the breadth of its application. The comprehensive mechanical properties of crust leather tanned with ethylene glycol glycidyl ether modified tannic acid-based chrome-free tanning agents prepared by the present invention are better than those of crust leather tanned with F-90 and TWS tanning agents.

[0071] In summary, this invention, for the first time, utilizes ethylene glycol glycidyl ether to modify tannic acid to produce a chrome-free tanning agent. This method is simple, environmentally friendly, and uses no toxic raw materials. The resulting chrome-free tanning agent can be applied to chrome-free tanning systems, addressing the chromium pollution problem in the leather industry. Crust leather tanned with TA-EGDE exhibits a high shrinkage temperature and excellent physical and mechanical properties.

[0072] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a tannic acid-based chrome-free tanning agent modified with ethylene glycol glycidyl ether, characterized in that: This includes the following methods: Step S1, heating 2 g to 20 g of ethylene glycol glycidyl ether to obtain a heated ethylene glycol glycidyl ether solution; Step S2, dissolving 5 g to 20 g of tannic acid in water, adding 60 mL to 100 mL of distilled water until completely dissolved to obtain a tannic acid solution, then adjusting the pH of the tannic acid solution to 8.0 to 10.0 with sodium hydroxide, then adding the pH-adjusted tannic acid solution to the heated ethylene glycol glycidyl ether solution, while maintaining the heating temperature constant, reacting, and adjusting the pH to obtain a mixed solution; Step S3, cooling the mixed solution, removing unreacted ethylene glycol glycidyl ether and then vacuum drying to obtain a solid powder, which is the ethylene glycol glycidyl ether modified tannic acid-based chrome-free tanning agent.

2. The method for preparing the ethylene glycol glycidyl ether modified tannic acid-based chrome-free tanning agent according to claim 1, characterized in that: In step S1, ethylene glycol glycidyl ether is heated to 40°C to 50°C.

3. The method for preparing the ethylene glycol glycidyl ether modified tannic acid-based chrome-free tanning agent according to claim 1, characterized in that: In step S2, the tannic acid solution is added to the heated ethylene glycol glycidyl ether solution, and the heating temperature is maintained at 40° C. to 50° C. for a reaction of 2 h to 5 h.

4. The method for preparing the tannic acid-based chrome-free tanning agent modified with ethylene glycol glycidyl ether according to claim 1, characterized in that: The pH value of the mixed solution is 5.

5.

5. The method for preparing the tannic acid-based chrome-free tanning agent modified with ethylene glycol glycidyl ether according to claim 1, characterized in that: In step S3, the cooling temperature is reduced to room temperature, and vacuum drying is performed at 40° C. to obtain a solid powder.

6. The method for preparing the ethylene glycol glycidyl ether modified tannic acid-based chrome-free tanning agent according to claim 1, characterized in that: The molecular weight of the tannic acid is 1000-2000.

7. The tannic acid-based chrome-free tanning agent modified with ethylene glycol glycidyl ether prepared according to the preparation method according to any one of claims 1 to 5.

8. Use of the ethylene glycol glycidyl ether modified tannic acid-based chrome-free tanning agent according to claim 7 in leather tanning.

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