Method for removing newly generated organic impurities in stripping liquid recycling process

Abstract

The invention relates to the technical field of stripping liquid purification, and particularly discloses a method for removing new organic impurities in a stripping liquid recycling process. An additive is added into the waste stripping liquid, the waste stripping liquid is heated to 60 DEG C or above and preheated for at least 0.5 h, then evaporation deslagging and rectification purification are sequentially carried out, the regenerated stripping liquid is obtained, the newly generated organic impurity is 4-(diethylamino)-2-butanone, and the additive comprises a hydrazine compound and citric acid. The new impurity 4-(diethylamino)-2-butanone in the waste stripping liquid can be effectively removed, no impurity is introduced, and the method has the advantage of low cost.

Description

Technical Field

[0001] The invention relates to the technical field of stripping liquid purification, and in particular to a method for removing newly generated organic impurities in the recycling process of stripping liquid. Background Art

[0002] The display panel production process involves cleaning, coating, photolithography, etching / stripping, and other processes. Numerous wet electronic chemicals are used throughout the process, with stripping fluid being the most widely used wet electronic chemical. Its primary component is a mixed organic solvent with excellent photoresist removal capabilities. Waste stripping fluid is the waste liquid generated after the stripping process. Because waste stripping fluid is relatively expensive, it is typically recycled after regeneration to save costs.

[0003] However, during the reuse process, the concentration of an unknown substance in the stripping fluid waste was found to be increasing. This concentration accumulated with each reuse, exceeding 0.5%, significantly impacting product quality and reducing the proportion of recycled fluid in the fresh fluid. However, the absolute concentration of the unknown substance was low, making it difficult to separate and identify effectively, further complicating its targeted removal. Furthermore, achieving cost-effective and efficient removal without introducing impurities and compromising product quality was a significant challenge. Summary of the Invention

[0004] The object of the present invention is to provide a method for removing newly generated organic impurities in the recycling process of a stripping solution, which can effectively reduce or even remove the newly generated impurity 4-(diethylamino)-2-butanone in the waste stripping solution.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for removing newly generated organic impurities during the recycling process of a stripping solution comprises adding an additive to the waste stripping solution, heating the solution to above 60°C for at least 0.5h, and then sequentially performing evaporation, deslagging, and distillation purification to obtain a regenerated stripping solution, wherein the newly generated organic impurity is 4-(diethylamino)-2-butanone, and the additive comprises a hydrazine compound and citric acid.

[0007] The invention adds hydrazine compounds and citric acid to the waste stripping liquid, preheats the liquid to above 60° C. and keeps the temperature for a period of time, and then performs conventional evaporation, deslagging, and distillation purification, thereby effectively reducing or even removing the newly generated organic impurities in the waste stripping liquid, namely 4-(diethylamino)-2-butanone.

[0008] In addition, the waste stripping liquid of the present invention contains photoresist. If only hydrazine compounds are added to remove newly generated organic impurities, the photoresist will agglomerate and solidify during the treatment of the waste stripping liquid, affecting the operation of the entire treatment system and the removal efficiency of newly generated organic impurities. Mainly, the agglomerated and solidified photoresist will form scale in the evaporator, which not only affects the removal efficiency of newly generated organic impurities, but also seriously causes equipment blockage.

[0009] The present invention simultaneously adds a hydrazine compound and citric acid to a waste stripping solution, utilizes the hydrazine compound to remove the newly generated organic impurity 4-(diethylamino)-2-butanone, and the citric acid can prevent the photoresist from agglomerating and solidifying, thereby ultimately improving the removal efficiency of the newly generated organic impurity 4-(diethylamino)-2-butanone.

[0010] In a preferred embodiment, the preheating temperature is 70-100°C.

[0011] In a preferred embodiment, the preheating temperature is 70-80°C.

[0012] The preheating temperature affects the removal effect of the newly generated organic impurity 4-(diethylamino)-2-butanone in the waste stripping liquid. When the temperature is lower than 50°C, the removal effect of the newly generated organic impurity 4-(diethylamino)-2-butanone is poor, and as the temperature increases, the removal effect of the newly generated organic impurity 4-(diethylamino)-2-butanone improves. When the temperature is increased to 80°C, after treatment by the method of the present invention, the regenerated stripping liquid almost does not contain the newly generated organic impurity 4-(diethylamino)-2-butanone.

[0013] In a preferred embodiment, based on the volume of the waste stripping liquid, the added amount of the hydrazine compound is greater than or equal to 0.3%, and the added amount of the citric acid is 1.0-2.0%.

[0014] In a preferred embodiment, the amount of the hydrazine compound added is 0.3-1.0% based on the volume of the waste stripping solution.

[0015] In a preferred embodiment, the amount of the hydrazine compound added is 0.6-1.0% based on the volume of the waste stripping liquid.

[0016] In a preferred embodiment, based on the volume of the waste stripping liquid, the amount of the hydrazine compound added is 0.6-0.8%, and the amount of the citric acid added is 1.0%.

[0017] The amount of hydrazine compound added affects the removal effect of the newly generated organic impurity 4-(diethylamino)-2-butanone in the waste stripping liquid. Based on the volume of the waste stripping liquid, when the amount of hydrazine compound added is less than 0.3%, the removal effect of the newly generated organic impurity 4-(diethylamino)-2-butanone in the waste stripping liquid is very weak. When the amount of hydrazine compound added is 0.3%, the content of the newly generated organic impurity 4-(diethylamino)-2-butanone in the waste stripping liquid can be significantly reduced. When the amount of hydrazine compound added is 0.6%, after treatment by the method of the present invention, the regenerated stripping liquid hardly contains the newly generated organic impurity 4-(diethylamino)-2-butanone. At this time, further increasing the amount of hydrazine compound added is equivalent to the addition amount of 0.6%.

[0018] In a preferred embodiment, the preheating time is 1-4 hours, or the preheating time is 1-2 hours.

[0019] In a preferred embodiment, the method comprises the following steps:

[0020] S1, adding the waste stripping liquid, hydrazine compound and citric acid into a preheater, heating to above 60° C. for at least 0.5 h to obtain a pretreated waste stripping liquid;

[0021] S2, introducing the pre-treated waste stripping liquid into an evaporation kettle for evaporation and slag removal to obtain an evaporated liquid;

[0022] S3, introducing the evaporated liquid into the distillation tower 1 for the first distillation purification to remove light components;

[0023] S4. The heavy components produced in the distillation tower 1 are introduced into the distillation tower 2 for a second distillation and purification to remove the heavy components. The light components produced in the distillation tower 2 are the product regeneration stripping liquid.

[0024] In a preferred embodiment, the waste stripping liquid, the hydrazine compound and the citric acid are first added to a mixing tank for mixing, and then the mixed solution is added to a preheater for preheating.

[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0026] 1. The method of the present invention adds a hydrazine compound and citric acid to the waste stripping liquid and preheats it to above 60°C for a period of time, and then performs conventional evaporation and deslagging and distillation purification. The newly generated organic impurity 4-(diethylamino)-2-butanone in the waste stripping liquid can be effectively reduced or even removed. The content of the newly generated organic impurity 4-(diethylamino)-2-butanone in the regenerated stripping liquid can be reduced to as low as 0.01%, thereby greatly improving the quality of the regenerated stripping liquid.

[0027] 2. The method of the present invention does not introduce impurities (the added hydrazine compound can react with the newly generated organic impurity 4-(diethylamino)-2-butanone to produce a high-boiling-point conjugate, and the excess hydrazine compound and the high-boiling-point conjugate can be removed by distillation). No expensive reagents are introduced, and the method has the advantage of low cost. That is, the present invention not only improves the quality of the product regeneration stripping liquid, but also increases the reuse ratio of the recovered liquid in the new liquid. At the same time, no new safety and environmental risks are added in production, and it is a green and efficient treatment method. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0029] Figure 1 The process flow chart of treating waste stripping liquid in the prior art;

[0030] Figure 2 The process flow of treating waste stripping liquid of the present invention is as follows Figure 1 ;

[0031] Figure 3 The process flow of treating waste stripping liquid of the present invention is as follows Figure 2 . DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the examples. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention. The embodiments described below are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0033] In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that these specific details are not necessarily required to practice the present invention. In other examples, well-known structures, materials, or methods are not specifically described to avoid obscuring the present invention. The materials, instruments, and reagents used in the following examples, unless otherwise specified, are commercially available. The techniques used in the examples, unless otherwise specified, are conventional techniques well known to those skilled in the art.

[0034] The waste stripping liquid mainly contains organic matter 1 and organic matter 2, wherein organic matter 1 is diethylene glycol butyl ether; organic matter 2 is nitrogen methylethanolamine or nitrogen methylformamide. Depending on the manufacturer generating the waste liquid, organic matter 2 is different, namely nitrogen methylethanolamine or nitrogen methylformamide.

[0035] like Figure 1 As shown, the existing treatment process of waste stripping liquid (waste liquid) is as follows: the waste stripping liquid is directly introduced into an evaporator for evaporation and slag removal to obtain an evaporated liquid (solvent); the evaporated liquid is introduced into a distillation tower 1 for a first distillation and purification to remove the light components (wastewater) produced in the distillation tower 1, and the heavy components produced in the distillation tower 1 are introduced into a distillation tower 2 for a second distillation and purification to remove the heavy components (diethanolamine / triethanolamine, etc.) produced in the distillation tower 2. The light components obtained in the distillation tower 2 are the product (regenerated stripping liquid). In addition to organic matter 1 and organic matter 2, the regenerated stripping liquid also contains a newly generated impurity 4-(diethylamino)-2-butanone.

[0036] Existing processes are unable to remove 4-(diethylamino)-2-butanone from waste stripping fluid. As the stripping fluid is recycled, new impurities gradually accumulate. Furthermore, because the boiling point of this organic impurity lies between those of the two active components in the stripping fluid, it is extracted along with the active components during the distillation process and remains in the recycled fluid, rendering it impossible to remove. Furthermore, this impurity is generated again during the use of the recycled stripping fluid by customers, leading to a gradual accumulation of organic impurities.

[0037] Therefore, the existing waste stripping liquid treatment method cannot remove the newly generated impurities when treating the waste stripping liquid after the customer's process change. The present invention uses gas chromatography to detect the newly generated impurity in the waste stripping liquid as 4-(diethylamino)-2-butanone. 4-(diethylamino)-2-butanone is an existing substance, and its structure is shown below:

[0038]

[0039] In order to remove the newly emerged impurity 4-(diethylamino)-2-butanone in the waste stripping solution, Figure 2 As shown, this embodiment provides a method for removing newly generated organic impurities during the recycling process of the stripping liquid, adding additives to the waste stripping liquid, heating it to above 60°C for at least 0.5h, and then performing evaporation and deslagging, distillation and purification in sequence to obtain a regenerated stripping liquid, the newly generated organic impurity is 4-(diethylamino)-2-butanone, and the additives include hydrazine compounds and citric acid.

[0040] The method of this embodiment adds a hydrazine compound to the waste stripping liquid and preheats it to above 60° C. for a period of time, and then performs conventional evaporation, deslagging, and distillation purification. This method can effectively reduce or even remove the newly generated organic impurity 4-(diethylamino)-2-butanone in the waste stripping liquid. The content of the newly generated organic impurity 4-(diethylamino)-2-butanone in the regenerated stripping liquid can be reduced to as low as 0.01%, greatly improving the quality of the regenerated stripping liquid.

[0041] The hydrazine compound of the present invention can react with the newly generated organic impurity 4-(diethylamino)-2-butanone. Theoretically, as long as it contains the structure of hydrazine, it can react with the newly generated organic impurity 4-(diethylamino)-2-butanone. Therefore, the hydrazine compound can be an organic hydrazine compound or an inorganic hydrazine compound. Among them, the organic hydrazine compound includes methylhydrazine, dimethylhydrazine, ethylhydrazine or phenylhydrazine; the inorganic hydrazine compound includes hydrazine and hydrazine salts (hydrazine sulfate or hydrazine nitrate, etc.).

[0042] The present invention simultaneously adds a hydrazine compound and citric acid to a waste stripping solution, utilizes the hydrazine compound to remove the newly generated organic impurity 4-(diethylamino)-2-butanone, and the citric acid can prevent the photoresist from agglomerating and solidifying, thereby ultimately improving the removal efficiency of the newly generated organic impurity 4-(diethylamino)-2-butanone.

[0043] Preferably, the preheating temperature is 70-100°C.

[0044] More preferably, the preheating temperature is 70-80°C.

[0045] Preferably, based on the volume of the waste stripping liquid, the added amount of the hydrazine compound is greater than or equal to 0.3%; and the added amount of citric acid is 1.0-2.0%.

[0046] More preferably, the amount of the hydrazine compound added is 0.3-1.0% based on the volume of the waste stripping liquid.

[0047] More preferably, the amount of the hydrazine compound added is 0.6-1.0% based on the volume of the waste stripping liquid.

[0048] More preferably, based on the volume of the waste stripping liquid, the added amount of the hydrazine compound is 0.6-0.8%; and the added amount of citric acid is 1.0%.

[0049] Preferably, the preheating time is 1-4 hours, more preferably, the preheating time is 1-2 hours.

[0050] In a specific case, Figure 2 、 Figure 3 As shown, a method for removing newly generated organic impurities in the recycling process of stripping liquid comprises the following steps:

[0051] S1. Add the waste stripping liquid, hydrazine compound and citric acid into a preheater, heat to above 60° C. and preheat for at least 0.5 h to obtain a pretreated waste stripping liquid; preferably, first add the waste stripping liquid, hydrazine compound and citric acid into a mixing tank and mix them, and then add the mixed solution into the preheater for preheating treatment;

[0052] S2, introducing the pre-treated waste stripping liquid into an evaporation kettle for evaporation and slag removal to obtain an evaporated liquid;

[0053] S3, introducing the evaporated liquid into the distillation tower 1 for the first distillation purification to remove light components;

[0054] S4. The heavy components produced in the distillation tower 1 are introduced into the distillation tower 2 for a second distillation and purification to remove the heavy components. The light components produced in the distillation tower 2 are the product regeneration stripping liquid.

[0055] In order to better illustrate the effect of the method described in this embodiment, the following specific cases are used for illustration:

[0056] Example 1:

[0057] A method for removing newly generated organic impurities in a stripping solution recycling process comprises the following steps:

[0058] First, 50 mL of waste stripping liquid, 0.15 mL of hydrazine compound and 0.5 g of citric acid are added to a mixing tank for mixing, and then the mixed solution is added to a preheater for preheating treatment at a temperature of 80°C for 1 hour to obtain a pretreated waste stripping liquid; then the pretreated waste stripping liquid is evaporated and deslagging, and purified by secondary distillation to obtain a regenerated stripping liquid.

[0059] In this embodiment, based on the volume of the waste stripping liquid, the added amount of the hydrazine compound is 0.3%, and the added amount of citric acid (m / v) is 1.0%; the hydrazine compound is methylhydrazine, and the original waste stripping liquid contains organic matter 1, organic matter 2, and impurities, among which the content of the newly generated impurity 4-(diethylamino)-2-butanone is 0.55; organic matter 1 is diethylene glycol butyl ether; and organic matter 2 is nitrogen-methylethanolamine.

[0060] Example 2:

[0061] This embodiment is based on Example 1, and differs from Example 1 in that the amount of the hydrazine compound added is different. In this embodiment, the amount of the hydrazine compound added is 0.4% based on the volume of the waste stripping liquid. Specifically:

[0062] First, 50 mL of waste stripping liquid, 0.2 mL of hydrazine compound and 0.5 g of citric acid were added to a mixing tank for mixing, and then the mixed solution was added to a preheater for preheating at 80° C. for 1 hour.

[0063] Example 3:

[0064] This embodiment is based on Example 1, and differs from Example 1 in that the amount of the hydrazine compound added is different. In this embodiment, the amount of the hydrazine compound added is 0.6% based on the volume of the waste stripping liquid. Specifically:

[0065] First, 50 mL of waste stripping liquid, 0.3 mL of hydrazine compound and 0.5 g of citric acid were added to a mixing tank for mixing, and then the mixed solution was added to a preheater for preheating at 80° C. for 1 hour.

[0066] Example 4:

[0067] This embodiment is based on Example 1, and differs from Example 1 in that the amount of the hydrazine compound added is different. In this embodiment, the amount of the hydrazine compound added is 0.8% based on the volume of the waste stripping liquid. Specifically:

[0068] First, 50 mL of waste stripping liquid, 0.4 mL of hydrazine compound and 0.5 g of citric acid were added to a mixing tank for mixing, and then the mixed solution was added to a preheater for preheating at 80° C. for 1 hour.

[0069] Example 5:

[0070] This embodiment is based on Example 1, and differs from Example 1 in that the amount of the hydrazine compound added is different. In this embodiment, the amount of the hydrazine compound added is 1.0% based on the volume of the waste stripping liquid. Specifically:

[0071] First, 50 mL of waste stripping liquid, 0.5 mL of hydrazine compound and 0.5 g of citric acid were added to a mixing tank for mixing, and then the mixed solution was added to a preheater for preheating at 80° C. for 1 hour.

[0072] Comparative Example 1:

[0073] This comparative example is based on Example 1, and differs from Example 1 in that no hydrazine compound is added.

[0074] Comparative Example 2:

[0075] This comparative example is based on Example 1, and differs from Example 1 in that the amount of organic alkali added is different. In this comparative example, the amount of hydrazine compound added is 0.2% based on the volume of the waste stripping liquid. Specifically:

[0076] First, 50 mL of waste stripping liquid, 0.1 mL of hydrazine compound and 0.5 g of citric acid were added to a mixing tank for mixing, and then the mixed solution was added to a preheater for preheating at 80° C. for 1 hour.

[0077] Comparative Example 3:

[0078] This embodiment is based on embodiment 4, and differs from embodiment 4 in that citric acid is not added.

[0079] Comparative Example 4:

[0080] This embodiment is based on embodiment 4, and differs from embodiment 4 in that the amount of citric acid added is different, that is, the amount of citric acid added is 0.2 g.

[0081] Gas chromatography was used to detect the content of the newly generated impurity 4-(diethylamino)-2-butanone and the content of the two active ingredients in the regeneration stripping solutions prepared in Examples 1 to 5 and Comparative Examples 1 and 2. The results are shown in Table 1:

[0082] Table 1

[0083]

[0084]

[0085] Among them, organic compound 1 is diethylene glycol butyl ether; organic compound 2 is nitrogen methylethanolamine.

[0086] Among them, the chromatographic conditions of gas chromatography are as follows:

[0087] Chromatographic column: DB-1 column or other columns that can achieve the same degree of separation;

[0088] Column temperature: start at 60°C and increase to 270°C at a rate of 20°C / min;

[0089] Inlet temperature: 250°C;

[0090] Detector temperature: 300°C;

[0091] Carrier gas (nitrogen) flow rate: 1.0 mL / min;

[0092] Hydrogen flow rate: 35 mL / min;

[0093] Air flow rate: 350 mL / min;

[0094] Split ratio: 80:1;

[0095] Injection volume: 0.2uL.

[0096] From the data in Table 1, we can see that:

[0097] The content of the newly generated organic impurity 4-(diethylamino)-2-butanone in the regenerated stripping liquid decreases with the increase of the amount of hydrazine compound used. When the added amount of hydrazine compound is less than 0.3%, the removal effect of the newly generated organic impurity 4-(diethylamino)-2-butanone in the waste stripping liquid is very weak. When the added amount of hydrazine compound is 0.3%, the content of the newly generated organic impurity 4-(diethylamino)-2-butanone in the waste stripping liquid can be significantly reduced. When the added amount of hydrazine compound is 0.6%, after treatment by the method of the present invention, the regenerated stripping liquid almost does not contain the newly generated organic impurity 4-(diethylamino)-2-butanone. At this time, further increasing the added amount of hydrazine compound is equivalent to the addition amount of 0.6%.

[0098] Without the use of hydrazine compounds, the removal of newly generated impurities during the treatment of waste stripping liquid is completely ineffective.

[0099] The comparison of the removal efficiency of the newly generated organic impurity 4-(diethylamino)-2-butanone with or without the addition of citric acid is shown in Table 2:

[0100] Table 2

[0101]

[0102]

[0103] From the data in Table 2, we can see that:

[0104] Compared with adding hydrazine compounds alone, adding hydrazine compounds and citric acid simultaneously has a higher removal efficiency for the newly generated organic impurity 4-(diethylamino)-2-butanone, and when the addition amount of citric acid is low, the removal efficiency for the newly generated organic impurity 4-(diethylamino)-2-butanone is correspondingly reduced.

[0105] The added citric acid will be removed in the subsequent distillation (citric acid is non-volatile and will be removed during the evaporation and deslagging process)

[0106] Example 6:

[0107] This embodiment is based on embodiment 5, and differs from embodiment 5 in that the preheating temperature is different. Specifically:

[0108] First, 50 mL of waste stripping liquid, 0.5 mL of hydrazine compound and 0.5 g of citric acid were added to a mixing tank for mixing, and then the mixed solution was added to a preheater for preheating at 60° C. for 1 hour.

[0109] Example 7:

[0110] This embodiment is based on embodiment 5, and differs from embodiment 5 in that the preheating temperature is different. Specifically:

[0111] First, 50 mL of waste stripping liquid, 0.5 mL of hydrazine compound and 0.5 g of citric acid were added to a mixing tank for mixing, and then the mixed solution was added to a preheater for preheating at 70° C. for 1 hour.

[0112] Comparative Example 5:

[0113] This comparative example is based on Example 5, and differs from Example 5 in that the preheating temperature is different. Specifically:

[0114] First, 50 mL of waste stripping liquid, 0.5 mL of hydrazine compound and 0.5 g of citric acid were added to a mixing tank for mixing, and then the mixed solution was added to a preheater for preheating at 50° C. for 1 hour.

[0115] Gas chromatography was used to detect the content of the newly generated impurity 4-(diethylamino)-2-butanone and the content of the two active ingredients in the regeneration stripping solutions prepared in Examples 6-7 and Comparative Example 5. The results are shown in Table 3:

[0116] Table 3

[0117] Preheating temperature Organic matter 1 Organic Matter 2 New impurities Comparative Example 5 50℃ 9.21 90.08 0.36 Example 6 60℃ 9.44 89.89 0.22 Example 7 70℃ 9.46 89.89 0.07 Example 5 80℃ 9.50 90.03 0.01

[0118] From the data in Table 3, we can see that:

[0119] The preheating temperature affects the removal effect of the newly generated organic impurity 4-(diethylamino)-2-butanone in the waste stripping liquid. When the temperature is lower than 50°C, the removal effect of the newly generated organic impurity 4-(diethylamino)-2-butanone is poor, and as the temperature increases, the removal effect of the newly generated organic impurity 4-(diethylamino)-2-butanone is improved. When the temperature is increased to 80°C, after treatment by the method of the present invention, the regenerated stripping liquid hardly contains the newly generated organic impurity 4-(diethylamino)-2-butanone.

[0120] Example 8:

[0121] This embodiment is based on embodiment 5, and differs from embodiment 5 in that the hydrazine compound is different, and this embodiment adopts phenylhydrazine.

[0122] Example 9:

[0123] This embodiment is based on embodiment 5, and differs from embodiment 5 in that the hydrazine compound is different, and this embodiment uses hydrazine.

[0124] Example 10:

[0125] This embodiment is based on Example 5, and differs from Example 5 in that the hydrazine compound is different, and this embodiment uses hydrazine sulfate.

[0126] Comparative Example 6:

[0127] This comparative example is based on Example 5, and differs from Example 5 in that no hydrazine compound is used.

[0128] Comparative Example 7:

[0129] This comparative example is based on Example 5, and differs from Example 5 in that an equal amount of sodium hydroxide is used to replace the hydrazine compound.

[0130] Comparative Example 8:

[0131] This comparative example is based on Example 5, and differs from Example 5 in that an equal amount of calcium oxide is used to replace the hydrazine compound.

[0132] Comparative Example 9:

[0133] This comparative example is based on Example 5, and differs from Example 5 in that triethanolamine is used to replace the hydrazine compound.

[0134] Gas chromatography was used to detect the content of the newly generated impurity 4-(diethylamino)-2-butanone and the content of the two active ingredients in the regeneration stripping solutions prepared in Example 5, Example 8-Example 10, and Comparative Example 6-Comparative Example 9. The results are shown in Table 4:

[0135] Table 4

[0136] additive Organic matter 1 Organic Matter 2 New impurities Comparative Example 6 citric acid 8.90 89.89 0.55 Comparative Example 7 Sodium hydroxide and citric acid 8.91 89.89 0.54 Comparative Example 8 Calcium oxide and citric acid 8.91 89.89 0.55 Comparative Example 9 Triethanolamine and citric acid 8.84 89.89 0.54 Example 5 Methylhydrazine and citric acid 9.50 90.03 0.01 Example 8 Phenylhydrazine and citric acid 9.52 90.06 0.01 Example 9 Hydrazine and citric acid 9.50 90.02 0.01 Example 10 Hydrazine sulfate and citric acid 9.53 90.04 0.01

[0137] The data in Table 4 show that, except for hydrazine compounds, which are effective in removing the newly formed impurity 4-(diethylamino)-2-butanone in the regenerated stripping solution, other bases are ineffective against the newly formed impurity 4-(diethylamino)-2-butanone, and the effects of organic and inorganic hydrazine compounds are comparable.

[0138] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for removing newly generated organic impurities in the recycling process of stripping liquid, characterized in that: Additives are added to the waste stripping liquid, which is heated to above 60° C. for at least 0.5 h, and then evaporated, deslagging, and distilled for purification to obtain a regenerated stripping liquid, wherein the newly generated organic impurity is 4-(diethylamino)-2-butanone, and the additives include hydrazine compounds and citric acid.

2. The method for removing newly generated organic impurities in the recycling process of stripping solution according to claim 1, characterized in that: The preheating temperature is 70-100℃.

3. The method for removing newly generated organic impurities in the recycling process of stripping solution according to claim 2, characterized in that: The preheating temperature is 70-80℃.

4. The method for removing newly generated organic impurities in the recycling process of stripping solution according to claim 1, characterized in that: Based on the volume of the waste stripping liquid, the added amount of the hydrazine compound is greater than or equal to 0.3%, and the added amount of the citric acid is 1.0-2.0%.

5. The method for removing newly generated organic impurities in the recycling process of stripping solution according to claim 4, characterized in that: The added amount of the hydrazine compound is 0.3-1.0% based on the volume of the waste stripping liquid.

6. The method for removing newly generated organic impurities in the recycling process of stripping solution according to claim 4, characterized in that: The added amount of the hydrazine compound is 0.6-1.0% based on the volume of the waste stripping liquid.

7. The method for removing newly generated organic impurities in the recycling process of stripping solution according to claim 4, characterized in that: Based on the volume of the waste stripping liquid, the added amount of the hydrazine compound is 0.6-0.8%, and the added amount of the citric acid is 1.0%.

8. The method for removing newly generated organic impurities in the recycling process of stripping solution according to claim 1, characterized in that: The preheating time is 1-4 hours, or the preheating time is 1-2 hours.

9. A method for removing newly generated organic impurities in a stripping solution recycling process according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1, adding the waste stripping liquid, the hydrazine compound and the citric acid into a preheater, heating to above 60° C. and preheating for at least 0.5 h to obtain a pretreated waste stripping liquid; S2, introducing the pre-treated waste stripping liquid into an evaporation kettle for evaporation and slag removal to obtain an evaporated liquid; S3, introducing the evaporated liquid into the distillation tower 1 for the first distillation purification to remove light components; S4. The heavy components produced in the distillation tower 1 are introduced into the distillation tower 2 for a second distillation and purification to remove the heavy components. The light components produced in the distillation tower 2 are the product regeneration stripping liquid.

10. The method for removing newly generated organic impurities in the recycling process of stripping solution according to claim 9, characterized in that: The waste stripping liquid, the hydrazine compound and the citric acid are first added to a mixing tank for mixing, and then the mixed solution is added to the preheater for preheating.

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