Complexing agent for chrome-free tanning of leather and preparation method of complexing agent

Abstract

The invention discloses a complexing agent for chrome-free tanning of leather. The complexing agent is prepared by reacting the following components in parts by mass: 50 to 100 parts of glycol polyol, 50 to 200 parts of unsaturated conjugated anhydride, 0.1 to 0.5 part of catalyst, 50 to 300 parts of anhydrous sodium sulfite and 150 to 600 parts of water. Aiming at the characteristics of zirconium tanning and titanium tanning, the invention provides the complexing agent for chrome-free tanning of leather, which has the advantages of easily available raw materials, simple production process operation and small environmental pollution.

Description

Technical Field

[0001] The present invention relates to tanning, and more specifically to a complexing agent for chromium-free tanning of leather and a preparation method thereof. Background Art

[0002] Tanning is a physical and chemical process that turns raw hides into leather through tanning agents. The tanned leather is called wet leather, which is an important leather semi-finished product. It can be further processed according to customer needs or used as a leather commodity. The blue wet leather obtained by chromium tanning has a high heat shrinkage temperature, a soft leather body, a plump handfeel, and certain antibacterial properties, and is resistant to storage. It is the most important tanning method in the production of upper leather. However, the use of chromium tanning agents has caused certain chromium pollution to the environment. Especially, hexavalent chromium is highly toxic, and it is under great pressure from ecological environmental protection and the change of consumption concepts. Therefore, chromium-free tanning of white wet leather is the fundamental way to solve this problem.

[0003] In recent years, leather researchers have conducted a large number of studies on chromium-free and formaldehyde-free tanning processes, constantly exploring methods to replace chromium tanning and aldehyde tanning. Through research, it has been found that in addition to chromium tanning, other metal tanning agents have certain problems when used alone. The shrinkage temperature of the leather tanned with zirconium tanning agent is the highest except for chromium-tanned leather, but the zirconium tanning agent has a low precipitation point and strong hydrolysis, and tanning must be completed in a strong acidic environment. Moreover, the tanned leather is flat and thin and not soft enough. The leather tanned with titanium tanning agent has high strength, firmness, and good filling properties, and is closer to chromium-tanned leather in state compared with other inorganic tanned leather; however, when used alone, its alkali resistance is low and it will precipitate in an aqueous solution with a low pH value, resulting in uneven penetration in the leather. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the purpose of the present invention is mainly to provide a complexing agent for chromium-free tanning of leather with easily available raw materials, simple production process operation, and little environmental pollution according to the characteristics of zirconium tanning and titanium tanning.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A complexing agent for chromium-free tanning of leather,

[0007] which is formed by reacting the following parts by mass:

[0008] Glycol-based polyols: 50 - 100 parts

[0009] Unsaturated conjugated anhydrides: 50 - 200 parts

[0010] Catalyst: 0.1 - 0.5 parts

[0011] Anhydrous sodium sulfite: 50 - 300 parts

[0012] Water: 150 - 600 parts.

[0013] As a further improvement of the present invention,

[0014] The diol of the glycol is diethylene glycol, triethylene glycol, or tetraethylene glycol.

[0015] As a further improvement of the present invention,

[0016] The unsaturated conjugated anhydride is maleic anhydride or 2-methylmaleic anhydride.

[0017] As a further improvement of the present invention,

[0018] The catalyst is p-toluenesulfonic acid.

[0019] As a further improvement of the present invention,

[0020] It also includes 2,2′-(ethylenedisulfonyl)diethanol: 200 - 250 parts.

[0021] As another object of the present invention, a method for preparing a complexing agent for chrome-free tanning is provided.

[0022] Step 1: Take a glycol polyol and add it to a reactor. Control the temperature at 65 - 70 °C, add the unsaturated conjugated anhydride and the catalyst, raise the temperature to 90 - 95 °C, react for 100 - 200 min, and then cool down to 70 °C to obtain a monoesterified intermediate.

[0023] Step 2: Add anhydrous sodium sulfite to the product obtained in Step 1 and react at 70 °C for 40 - 100 min.

[0024] Step 3: Add water to the product of Step 2, adjust the temperature to 80 - 85 °C and react for 150 - 200 min, then cool down to obtain the complexing agent.

[0025] As another object of the present invention, a method for preparing a complexing agent for chrome-free tanning is provided.

[0026] Step 1: Take a glycol polyol and add it to a reactor. Control the temperature at 65 - 70 °C, add the unsaturated conjugated anhydride and the catalyst, raise the temperature to 90 - 95 °C, react for 100 - 200 min, then add 2,2′-(ethylenedisulfonyl)diethanol and react for 30 - 60 min, and cool down to 70 °C to obtain an intermediate.

[0027] Step 2: Add anhydrous sodium sulfite to the product obtained in Step 1 and react at 70 °C for 40 - 100 min.

[0028] Step 3: Add water to the product of Step 2, adjust the temperature to 80 - 85 °C and react for 150 - 200 min, then cool down to obtain the complexing agent.

[0029] The present invention has a hydrophilic complexing agent with good alkali resistance and can be used in high-concentration metal solutions to narrow the gap in the comprehensive performance between leather tanned with zirconium tanning agent or titanium tanning agent and chrome-tanned leather. The complexing agent of the present invention can effectively increase the precipitation point of traditional zirconium tanning agent and titanium tanning agent, improve the comprehensive performance of zirconium-tanned leather and titanium-tanned leather. When used in leather tanning, the shrinkage temperature of the leather can reach above 85°C.

[0030] The present invention can control the molecular weight and complexing ability of the complexing agent by controlling the molecular weight of the raw material glycol-based diol. The larger the n value in the raw material diol, the weaker the complexing ability of the corresponding product to zirconium ions and titanium ions; different complexing agents with different structures can be obtained by selecting raw materials with different n values. One or several complexing agent molecules can be selected to control the complexing ability of zirconium ions and titanium ions.

[0031] The method adopted in the present invention uses easily available raw materials, has mild reaction conditions, is simple to operate, and no secondary pollution is generated during the process. Detailed implementation mode

[0032] Example 1

[0033] (1) Weigh 100 parts of diethylene glycol, 200 parts of maleic anhydride, and 0.15 part of catalyst respectively by mass;

[0034] (2) Add diethylene glycol into the reactor, turn on the condensing water and stirrer, adjust the temperature to 70°C, add maleic anhydride and p-toluenesulfonic acid; after the feeding is completed, start heating up, when the temperature rises to 90°C, react for 150 minutes and then cool down to about 70°C to obtain a diethylene glycol monoesterification intermediate;

[0035] (3) Weigh 250 parts of anhydrous sodium sulfite solid by mass and add it to the monoesterification intermediate obtained in step (2), adjust the temperature to 70°C and react for 60 minutes;

[0036] (4) Weigh 500 parts of water by mass and add it to the product in step (3), adjust the temperature to 80°C and react for 180 minutes, then cool down and discharge to obtain a diethylene glycol sulfosuccinate salt-type organic complexing agent that is completely soluble in water.

[0037] Example 2

[0038] (1) Weigh 150 parts of triethylene glycol, 200 parts of maleic anhydride, and 0.15 part of catalyst respectively by mass;

[0039] (2) Add triethylene glycol into the reactor, turn on the condensing water and stirrer, adjust the temperature to 70°C, add maleic anhydride and p-toluenesulfonic acid; after the feeding is completed, start heating up, when the temperature rises to 90°C, react for 150 minutes and then cool down to about 70°C to obtain a triethylene glycol monoesterification intermediate;

[0040] (3) Add 250 parts by mass of anhydrous sodium sulfite solid to the monoesterified intermediate obtained in step (2), and adjust the temperature to 70 °C for reaction for 60 minutes;

[0041] (4) Weigh 500 parts by mass of water and add it to the product in step (3), adjust the temperature to 80 °C for reaction for 180 minutes, cool down and discharge to obtain a triglycol sulfosuccinate salt type organic complexing agent that is completely soluble in water.

[0042] Example 3

[0043] (1) Weigh 200 parts by mass of tetraethylene glycol, 200 parts by mass of maleic anhydride, and 0.15 parts by mass of a catalyst respectively;

[0044] (2) Add tetraethylene glycol to the reactor, turn on the condensing water and stirrer, adjust the temperature to 65 - 70 °C, add maleic anhydride and p-toluenesulfonic acid; after the feeding is completed, start heating up, when the temperature rises to 90 °C, react for 150 minutes and then cool down to about 70 °C to obtain a tetraethylene glycol monoesterified intermediate;

[0045] (3) Add 130 parts by mass of anhydrous sodium sulfite solid to the monoesterified intermediate obtained in step (2), and adjust the temperature to 70 °C for reaction for 60 minutes;

[0046] (4) Weigh 500 parts by mass of water and add it to the product in step (3), adjust the temperature to 80 °C for reaction for 180 minutes, cool down and discharge to obtain a tetraethylene glycol sulfosuccinate salt type organic complexing agent that is completely soluble in water.

[0047] Example 4:

[0048] (1) Weigh 100 parts by mass of diethylene glycol, 200 parts by mass of maleic anhydride, and 0.15 parts by mass of a catalyst respectively; 200 parts of 2,2′-(ethylenedisulfonyl)diethanol.

[0049] (2) Add diethylene glycol to the reactor, turn on the condensing water and stirrer, adjust the temperature to 70 °C, add maleic anhydride and p-toluenesulfonic acid; after the feeding is completed, start heating up, when the temperature rises to 90 °C, react for 150 minutes, then add 2,2′-(ethylenedisulfonyl)diethanol, react for 30 minutes and then cool down to about 70 °C to obtain a diethylene glycol monoesterified intermediate;

[0050] (3) Weigh 250 parts by mass of anhydrous sodium sulfite solid and add it to the monoesterified intermediate obtained in step (2), and adjust the temperature to 70 °C for reaction for 60 minutes;

[0051] (4) Weigh 500 parts by mass of water and add it to the product in step (3). Adjust the temperature to 80 °C and react for 180 minutes. Then cool down and discharge the material to obtain a diethylene glycol sulfosuccinate salt-type organic complexing agent that is completely soluble in water.

[0052] Testing:

[0053] 1. Precipitation point: Prepare a 1.0 mol / L zirconium sulfate solution and measure its pH and precipitation point respectively. Take 20 ml of the zirconium sulfate solution in a 100 ml beaker, add 6 g of the complexing agent in the example, measure its pH value with a pH meter, and then titrate it with a 0.2 mol / L sodium hydroxide solution until precipitation occurs and the precipitate is evenly dispersed and does not disappear within 30 seconds. Measure the pH value of the mixed solution at this time, which is the precipitation point.

[0054] 2. Shrinkage temperature:

[0055] Take 1.0 mol / L zirconium sulfate, add 6 g of the complexing agent to make a tanning agent, and tan at normal temperature and pressure. Take the sheep acid skin (2 cm × 3 cm) during tanning, cut two holes at both ends respectively, and measure the shrinkage temperature of the sample in turn with a PS-83 type leather shrinkage temperature tester. And adjust the pH value of the tanning agent, and measure the shrinkage temperature at three pH values of 1, 3, and 5.

[0056] Test 1:

[0057] Precipitation point (pH) Example 1 5.4 Example 2 5.2 Example 3 5.4 Example 4 5.5

[0058] Test 2:

[0059]

[0060] Judging from the results of Test 1, for the complexing agent prepared in the examples of the present invention, its precipitation point is basically above 5. In the market, products with a precipitation point above 4.5 already belong to high-quality products. The zirconium tanning agent prepared by using the present invention is better than most products in the market.

[0061] It can be seen from Test 2 that the zirconium tanning agent prepared by using the present invention basically reaches a shrinkage temperature above 85 °C. And the tanning agent prepared by the complexing agent in Example 4 has better temperature resistance. The pH value has the least influence on the shrinkage temperature and has the best buffering performance.

[0062] The above is only the preferred embodiment of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A complexing agent for chromium-free tanning of leather, characterized in that: It is formed by reacting the following parts by mass: Glycol polyols: 50 - 100 parts Unsaturated conjugated anhydrides: 50 - 200 parts Catalyst: 0.1 - 0.5 parts Sodium sulfite anhydrous: 50 - 300 parts Water: 150 - 600 parts.

2. The complexing agent for chromium-free tanning of leather according to claim 1, characterized in that: The dihydric alcohol of the glycol is diethylene glycol, triethylene glycol, or tetraethylene glycol.

3. The complexing agent for chromium-free tanning of leather according to claim 1, characterized in that: The unsaturated conjugated anhydride is maleic anhydride or 2-methylmaleic anhydride.

4. The complexing agent for chromium-free tanning of leather according to claim 1, characterized in that: The catalyst is p-toluenesulfonic acid.

5. The complexing agent for chromium-free tanning of leather according to claim 1, characterized in that: It further includes 2,2′-(ethylenedisulfonyl)diethanol: 100 - 250 parts.

6. A preparation method of the complexing agent for chromium-free tanning as described in any one of claims 1 to 4, characterized in that: Step 1: Take the glycol polyol and add it to a reactor, control the temperature at 65 - 70°C, add the unsaturated conjugated anhydride and the catalyst, raise the temperature to 90 - 95°C, react for 100 - 200 min, and then cool down to 70°C to obtain a monoesterified intermediate; Step 2: Add sodium sulfite anhydrous to the product obtained in Step 1, and adjust the temperature to react at 70°C for 40 - 100 min; Step 3: Add water to the product of Step 2, adjust the temperature to 80 - 85°C and react for 150 - 200 min, and then cool down to obtain the complexing agent.

7. A preparation method of the complexing agent for chromium-free tanning as described in claim 5, characterized in that: Step 1: Take the glycol polyol and add it to a reactor, control the temperature at 65 - 70°C, add the unsaturated conjugated anhydride and the catalyst, raise the temperature to 90 - 95°C, react for 100 - 200 min, then add 2,2′-(ethylenedisulfonyl)diethanol and react for 30 - 60 min, and cool down to 70°C to obtain an intermediate; Step 2: Add sodium sulfite anhydrous to the product obtained in Step 1, and adjust the temperature to react at 70°C for 40 - 100 min; Step 3: Add water to the product of Step 2, adjust the temperature to 80 - 85°C and react for 150 - 200 min, and then cool down to obtain the complexing agent.

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