A method of treating spent diluent

Abstract

The embodiment of the present application discloses a waste diluent treatment method, wherein the method comprises the following steps: adding solutions in positive photoresist, negative photoresist and auxiliary material tank into a distillation stirred tank to mix to generate a mixed solution; distilling the mixed solution to obtain a distillate and a post-distillation mixture; performing pressure filtration on the post-distillation mixture to obtain a filtrate and a residue, and adding the filtrate into the auxiliary material tank; separating the distillate to obtain propylene glycol methyl ether acetate and a saturated solution of propylene glycol methyl ether acetate, and adding the saturated solution of propylene glycol methyl ether acetate into the auxiliary material tank; and the propylene glycol methyl ether acetate is used to generate a diluent product. By using the present application, the loss of organic solvents can be reduced, and the cost of outsourcing incineration treatment of kettle bottom liquid and treatment of waste water containing diluent can be reduced.

Description

Technical Field

[0001] This invention belongs to the field of waste diluent treatment and relates to a method for treating waste diluent. Background Technology

[0002] In the manufacturing of liquid crystal display panels, photoresist technology is widely used. Photoresists are classified into two main categories based on the image they form: positive and negative. In the photoresist process, after exposure and development, the exposed portion dissolves, leaving the unexposed portion. This coating material is a positive photoresist, used in the Array process of liquid crystal panel production, and its main component is phenolic resin photoresist. Conversely, this coating material is a negative photoresist, used in the CF process of liquid crystal panel production, and its main component is acrylic resin photoresist. In both processes, a diluent is used to clean the nozzles used for coating the photoresist and the photoresist after the photoreaction. The main component of the diluent is propylene glycol methyl ether acetate. It also contains one or more solvents such as methyl 3-methoxypropionate, cyclohexanone, ethyl 3-ethoxypropionate, and 3-methoxybutylacetic acid ester, as well as resin monomers, resin, pigments, carbon black, dispersants, and photoinitiators.

[0003] Currently, waste diluents are mainly utilized through distillation, which involves three main processes: degumming, dehydration, and heavy metal removal to produce the final product. During the photoresist removal process, heating reduces the organic solvent in the autoclave heat exchanger, causing the photoresist to become viscous and easily form a gel in the heat exchanger tubes. This leads to three problems: severely impacting heat exchange efficiency, lengthy cleaning cycles reducing production efficiency, and shortening the lifespan of the heat exchanger tubes. Therefore, in current production, the bottom liquid is only discharged before severe gel formation. At this point, the bottom liquid still contains a large amount of organic solvent, which not only wastes a significant amount of organic solvent but also increases the amount of bottom liquid that needs to be outsourced for processing, greatly reducing the yield and profitability of waste diluents during resource utilization.

[0004] There is limited research on solid-liquid separation technology for waste diluent distillation bottom liquid. Currently, a method has been discovered that involves adding Lewis base to the bottom liquid, allowing it to settle and separate into layers, and then centrifuging to achieve solid-liquid separation. However, this method still has three drawbacks: (1) It requires the addition of auxiliary materials other than the components of the waste diluent bottom liquid, and these auxiliary materials need to be removed by re-distillation during the product recovery process, resulting in high industrialization costs. (2) The settling process takes a long time (3 days), leading to low production efficiency. (3) The filter residue is viscous, making it difficult to transport in actual production and difficult to remove from the vessel.

[0005] To recover the large amount of organic solvents still present in the bottom liquid, reduce the amount of bottom liquid to be disposed of through outsourced incineration, and improve the resource utilization efficiency of waste diluent, this paper proposes a method that overcomes the technical defects of the above methods, is low in cost, and is conducive to industrial production. Summary of the Invention

[0006] This invention addresses the shortcomings of existing technologies by proposing a waste diluent treatment method to solve the problem of large-scale organic solvent loss in the bottom liquid of waste diluent recycling reactors, maximizing the recovery of organic solvents and reducing the generation of secondary waste from photoresist. The invention comprises three points.

[0007] Firstly, positive and negative photoresist bottom solutions are mixed in a 1:1 ratio, and then water or wastewater containing low-concentration diluent generated from the resource utilization of waste diluent is added. The water and the diluent (propylene glycol methyl ether acetate) in the bottom solution azeotropically carry out a large amount of propylene glycol methyl ether acetate. After distillation, the product in the receiving tank exhibits stratification, with a high-concentration propylene glycol methyl ether acetate solution on top and a saturated propylene glycol methyl ether acetate solution on the bottom. The distillation vessel contains a small amount of propylene glycol methyl ether acetate, other small amounts of organic solvents, and most of the water and photoresist. Because the photoresist is easily soluble in propylene glycol methyl ether acetate and has hygroscopic properties, as a large amount of propylene glycol methyl ether acetate is carried out, the photoresist absorbs water and clumps together. The mixture is stirred in the distillation vessel, released, and filtered. The filter residue is then dried by a coil-type vacuum dryer connected to a condenser to recover the solvent in the filter residue. Finally, the filter residue is incinerated to achieve harmlessness. Compared to the current commercially available methods of directly incinerating bottom liquid, the author's method has a higher recovery rate of propylene glycol methyl ether acetate, which greatly reduces the loss of organic solvents, lowers the cost of outsourced bottom liquid incineration and wastewater treatment containing diluents, and increases product output and production profits.

[0008] Secondly, water is a component that is already present in waste diluents. Using water or wastewater generated during the production process as a production auxiliary material is inexpensive and readily available. Furthermore, it can be recycled during the production process, avoiding the introduction of new impurities into the product and eliminating the need for further separation and purification.

[0009] Thirdly, with the dilution of water, the water and photoresist are mixed more evenly after stirring, which makes it easier to release and solves the problem of the difficulty in transporting the originally viscous bottom liquid in the pipeline, which is beneficial to industrial production.

[0010] One embodiment of this application provides a method for treating waste diluent, which may include:

[0011] Positive photoresist, negative photoresist, and the solution in the auxiliary material tank are added to a distillation stirred tank and mixed to generate a mixed solution; the auxiliary material tank includes waste diluent;

[0012] The mixed solution is distilled to obtain a fraction and a mixture after distillation; the fraction consists of two layers, the upper layer being propylene glycol methyl ether acetate and the lower layer being a saturated solution of propylene glycol methyl ether acetate; the mixture after distillation includes photoresist and water;

[0013] The distilled mixture is filtered under pressure to obtain filtrate and residue, and the filtrate is added to the auxiliary material tank;

[0014] The fraction is separated to obtain saturated solutions of propylene glycol methyl ether acetate and propylene glycol methyl ether acetate. The saturated solution of propylene glycol methyl ether acetate is added to the auxiliary material tank. The propylene glycol methyl ether acetate is used to generate a diluent product.

[0015] In one feasible embodiment, the waste diluent includes one or more of the following solvents: propylene glycol methyl ether acetate, methyl 3-methoxypropionate, cyclohexanone, ethyl 3-ethoxypropionate, and 3-methoxybutylacetic acid ester, as well as resin monomers, resins, pigments, carbon black, dispersants, and photoinitiators.

[0016] In one feasible embodiment, the positive photoresist comprises phenolic resin photoresist; the negative photoresist comprises acrylic resin photoresist.

[0017] In one feasible implementation, the ratio of the positive photoresist to the negative photoresist added to the distillation stirring vessel is 1:1.

[0018] In one feasible implementation, the fraction is collected at a temperature below 96 degrees Celsius.

[0019] In one feasible implementation, the pressure filtration includes filtration and centrifugation. Attached Figure Description

[0020] Figure 1 This is a schematic flowchart of a waste diluent treatment method provided in an embodiment of this application;

[0021] Figure 2 This is a schematic diagram of a system for recovering waste diluent from the bottom of the vessel.

[0022] The symbols for the main components are explained below:

[0023] (1) First raw material storage tank; (2) Second raw material storage tank; (3) Auxiliary material storage tank; (4) Distillation stirring vessel; (5) First condenser; (6) Layered liquid storage tank; (7) Lower liquid storage tank; (8) Upper liquid storage tank; (9) Distillation column; (10) Reboiler; (11) Second condenser; (12) Fore-fraction liquid storage tank; (13) Product liquid storage tank; (14) Filter press; (15) Filtrate storage tank; (16) Vacuum drying oven; (17) Third condenser; (18) Condensate storage tank; (19) Iron drum. Detailed Implementation

[0024] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] Furthermore, for ease of understanding, please refer to Figure 1 , Figure 1 This is a schematic flowchart of the waste diluent treatment method provided in the embodiments of this application.

[0026] S101, positive photoresist, negative photoresist and the solution in the auxiliary material tank are added to a distillation stirring vessel and mixed to generate a mixed solution; the auxiliary material tank includes waste diluent;

[0027] The aforementioned positive and negative photoresists refer to the process in which, after the coating is exposed and developed, the exposed portion dissolves, leaving the unexposed portion. This type of coating material is positive photoresist, used in the Array process of LCD panel production, and its main component is phenolic resin photoresist. Conversely, the coating material is negative photoresist, used in the CF process of LCD panel production, and its main component is acrylic resin photoresist.

[0028] The aforementioned waste diluent is generated by the liquid crystal display panel manufacturing industry and consists of one or more solvents such as propylene glycol methyl ether acetate, methyl 3-methoxypropionate, cyclohexanone, ethyl 3-ethoxypropionate, and 3-methoxybutylacetic acid ester, as well as resin monomers, resins, pigments, carbon black, dispersants, and photoinitiators.

[0029] S102, the mixed solution is distilled to obtain a fraction and a distilled mixture; the fraction comprises two layers, the upper layer being propylene glycol methyl ether acetate and the lower layer being a saturated solution of propylene glycol methyl ether acetate; the distilled mixture comprises photoresist and water;

[0030] Distillation is a common method for separating substances with different boiling points and can be used in conjunction with rectification.

[0031] S103, the distilled mixture is filtered by pressure to obtain filtrate and residue, and the filtrate is added to the auxiliary material tank;

[0032] Pressure filtration is a common method for solid-liquid separation, which can be pressure filtration, simple filtration, or centrifugation.

[0033] S104, the fraction is separated to obtain a saturated solution of propylene glycol methyl ether acetate and propylene glycol methyl ether acetate, and the saturated solution of propylene glycol methyl ether acetate is added to the auxiliary material tank; the propylene glycol methyl ether acetate is used to generate a diluent product.

[0034] In this embodiment, a mixed solution is generated by adding positive photoresist, negative photoresist, and a solution from an auxiliary material tank to a distillation stirred vessel; the mixed solution is then distilled to obtain a fraction and a distillate mixture; the distillate mixture is then filtered to obtain a filtrate and a residue, and the filtrate is added to the auxiliary material tank; the fraction is separated to obtain propylene glycol methyl ether acetate and a saturated solution of propylene glycol methyl ether acetate, and the saturated solution of propylene glycol methyl ether acetate is added to the auxiliary material tank; the propylene glycol methyl ether acetate is used to generate a diluent product. Using this application can reduce the loss of organic solvents and lower the costs of outsourcing the incineration of bottom liquid and treating wastewater containing diluents.

[0035] The following will combine Figure 2The following describes the specific implementation scenario provided by the embodiments of this application. The specific implementation scheme and drawings are as follows: 1. The bottom liquid containing positive photoresist (commonly known in the industry as "red material") and the bottom liquid containing negative photoresist (commonly known in the industry as "black material") stored in the first raw material tank (1) and the second raw material tank (2) are respectively transported to the distillation stirring vessel (4) by pump A and pump B in a 1:1 ratio according to the difference between the liquid level gauges of raw material tanks ① and ②. 2. The water in the auxiliary material storage tank (3) or the low-concentration organic wastewater generated in the production (hereinafter collectively referred to as "wastewater") is transported to the distillation stirring vessel (4) by pump C at a ratio of 2 to 2.5 times the total mass of the bottom liquid raw materials of positive and negative photoresist in step 1. After stirring and mixing evenly, it is heated. 3. Collect the fraction from the distillation stirred vessel (4) at a temperature below 96 degrees Celsius (at atmospheric pressure), (5) use the first condenser to condense the fraction, and (6) use the layered storage tank to receive the fraction from the distillation stirred vessel (4), which is in a layered state. Observe the liquid level of the layered storage tank (6) and release the lower and upper layers accordingly. The lower layer liquid is a saturated solution of propylene glycol methyl ether acetate, which is stored in the lower storage tank (7) and finally transported to the auxiliary material storage tank (3) for recycling via pump D. The upper layer liquid is a high-concentration propylene glycol methyl ether acetate solvent, which is stored in the upper storage tank (8) and then enters the distillation purification process. After being heated by the reboiler (10), purified by the distillation column (9), and condensed by the second condenser (11), the first fraction is wastewater, which is stored in the first fraction storage tank (12) and transported to the auxiliary material storage tank (3) for recycling via pump E. The middle fraction is propylene glycol methyl ether acetate product, which is stored in the product storage tank (13). 4. After the material in the distillation stirring vessel (4) is cooled, it is stirred. The mixture of positive and negative photoresist and water is evenly distributed and transported to the filter press (14) by pump J. The filtrate flows into the filtrate storage tank (15) and is transported to the auxiliary material storage tank (3) by pump G for recycling. Filter residue 1 enters the filter residue tank and then enters the vacuum drying box (16). It is dried by vacuum pump H under reduced pressure. The drying gas is condensed by the third condenser (17). The condensate enters the condensate storage tank (18) and is transported to the auxiliary material storage tank (3) by pump I for recycling. After the filter residue 1 is dried, filter residue 2 is obtained. Finally, it is loaded into the iron drum (19) and sent out for incineration for harmless treatment.

[0036] The following describes a specific implementation scenario provided by the embodiments of this application. Specifically, 50g of positive photoresist bottom solution (commonly known in the industry as "red material") and 50g of negative photoresist bottom solution (commonly known in the industry as "black material") are thoroughly mixed in a beaker. 82.93g of this mixture is added to a three-necked flask, followed by 207.44g of saturated PGMEA solution (Note: In industrial production, water is added in the first round, and saturated PGMEA solution is added in the second round of wastewater; therefore, saturated PGMEA solution is used in this experiment). Distillation is stopped at 96 degrees Celsius. The upper layer of 41.23g of high-concentration PGMEA solution (PGMEA content of 88.3%) and the lower layer of saturated PGMEA solution (PGMEA content of 50.29g) are collected in a test tube. The material in the three-necked flask is simply filtered through a 60-mesh nylon mesh to obtain 60.31g of filtrate and 138.25g of filter residue. The filter residue was dried in a forced-air oven at 105 degrees Celsius for 12 hours to obtain 28.03g of dry residue.

[0037] The above is only one specific embodiment of the present invention, but the present invention is not limited thereto. Any changes that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A method for treating waste diluent, characterized in that, include: The bottom solution containing positive photoresist, the bottom solution containing negative photoresist, and the solution in the auxiliary material tank are added to a distillation stirring vessel and mixed to generate a mixed solution; the auxiliary material tank includes waste diluent; The mixed solution is distilled to obtain a fraction and a mixture after distillation; the fraction consists of two layers, the upper layer being propylene glycol methyl ether acetate and the lower layer being a saturated solution of propylene glycol methyl ether acetate; the mixture after distillation includes photoresist and water; The distilled mixture is filtered under pressure to obtain filtrate and residue, and the filtrate is added to the auxiliary material tank; The fraction is separated to obtain saturated solutions of propylene glycol methyl ether acetate and propylene glycol methyl ether acetate. The saturated solution of propylene glycol methyl ether acetate is added to the excipient tank. The propylene glycol methyl ether acetate is used to generate a diluent product. The ratio of the bottom liquid containing positive photoresist to the bottom liquid containing negative photoresist added to the distillation stirring vessel is 1:1; Positive photoresists include phenolic resin photoresists; negative photoresists include acrylic resin photoresists.

2. The method according to claim 1, characterized in that, The waste diluent includes one or more of the following solvents: propylene glycol methyl ether acetate, methyl 3-methoxypropionate, cyclohexanone, ethyl 3-ethoxypropionate, and 3-methoxybutylacetic acid ester; resin monomers; resin; pigments; carbon black; dispersants; and photoinitiators.

3. The method according to claim 1, characterized in that, The fraction was collected at a temperature below 96 degrees Celsius.

4. The method according to claim 1, characterized in that, The pressure filtration includes filtration and centrifugation.

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