Liquid crystal alignment agent waste liquid recycling device

Abstract

This utility model discloses a device for recycling and reusing liquid crystal alignment agent waste liquid, relating to the field of waste liquid recycling technology. It includes a reaction vessel and a dewatering assembly. The dewatering assembly includes a gas supply pipe and a gas extraction pipe both located on the reaction vessel. The gas supply pipe introduces a non-reactive gas into the reaction vessel to remove water and organic solvents from the liquid crystal alignment agent. The gas extraction pipe performs a vacuum operation on the inner cavity of the reaction vessel to reduce the vacuum level. The gas extraction pipe also serves as an outlet channel for supplying non-reactive gas. This utility model achieves synergistic dewatering through the dual action of non-reactive gas purging and vacuum pressure. The gas supply pipe introduces non-reactive gas to remove water / organic solvent vapors from the waste liquid, while the gas extraction pipe simultaneously reduces the vacuum level of the reaction vessel, significantly improving evaporation efficiency without causing loss of polymers in the liquid crystal alignment agent, effectively ensuring recycling efficiency.

Description

Technical Field

[0001] This utility model relates to the field of waste liquid recycling technology, specifically to a device for recycling and reusing liquid crystal alignment agent waste liquid. Background Technology

[0002] Liquid crystal display (LCD) elements are widely used in daily life, work, medical care, and leisure entertainment as affordable, high-volume, thin, light, and high-quality display devices. Currently, liquid crystal alignment films mainly use polyamic acid or soluble polyimide resin solutions as liquid crystal alignment agents. In application, the film is uniformly coated onto a substrate and then baked at high temperature. Alignment is achieved by rubbing the coating surface with rayon or nylon cloth, or by irradiating the liquid crystal alignment film with linear ultraviolet light.

[0003] Liquid crystal alignment agents can be applied using a transfer printing method. This involves adhering the alignment agent to a specialized APR (Adjustable Partition) plate with precise dimensions, which is then transferred to the glass substrate. The APR plate uses a mesh structure to absorb the alignment agent. During printing, the alignment agent is extruded from the mesh and transferred onto the glass substrate. A significant amount of alignment agent is scraped off the APR plate by a squeegee during the printing process, resulting in a 20wt%–40wt% mass loss. The actual utilization rate of the alignment agent is only 60wt%–80wt%.

[0004] Liquid crystal alignment agents have a stable molecular structure and are not prone to chain breakage or chain growth in the working environment, nor do they easily react with other substances. However, organic solvents can absorb moisture from the environment, causing an increase in the water content of polyimide waste liquid. When liquid crystal alignment agents come into contact with metal materials on the equipment, it will lead to an increase in the metal ion content of the waste liquid. Therefore, the water content and metal ion content of directly recycled liquid crystal alignment agent waste liquid are too high, which cannot meet the requirements of panel manufacturers for direct reuse.

[0005] Because the polyamic acid component in liquid crystal alignment agents is unstable at high temperatures, a common method for purifying liquid crystal alignment agents is to add an azeotropic organic solvent to the liquid crystal alignment solution waste at room temperature, and then use a vacuum distillation apparatus to remove the water and azeotropic organic solvent from the liquid crystal alignment agent through azeotropic methods. Metal ions are then removed through the adsorption of a cationic adsorbent. While this method can remove water and metal ions from the liquid crystal alignment agent waste solution, the purification time is long and the efficiency is low, requiring the continuous addition of azeotropic organic solvent in the later stages of distillation.

[0006] Based on this, patent document CN217829973U discloses a liquid crystal alignment agent purification device. The purification device includes a reaction tank, and a closed jacketed cooling structure is provided outside the reaction tank, forming a cavity between the jacketed cooling structure and the reaction tank. Both the reaction tank and the jacketed cooling structure are connected to a temperature control device. The jacketed cooling structure is provided with a feed port for adding materials to the reaction tank. The bottom of the reaction tank is provided with a discharge port. The cavity is provided with an exhaust port, and the exhaust port is connected to a pressure reducing device.

[0007] When the above-mentioned purification device is in use, the temperature of the reaction tank and the jacket cooling structure is adjusted, the evacuation valve and the Roots pump vacuum pump group are opened to draw a vacuum, and the temperature of the horizontal stainless steel shell heat exchanger is reduced so that the evaporated water and organic solvents condense in the horizontal stainless steel shell heat exchanger and enter the storage tank, thereby realizing the separation of water and organic solvents from the liquid crystal alignment agent.

[0008] However, the purification device described above evaporates water and organic solvents from the liquid crystal alignment agent by adjusting the temperature of the reaction tank and the jacket cooling structure. During this heating process, the polymers in the liquid crystal alignment agent (especially materials containing sensitive groups such as imide and amide) may undergo oxidative degradation or thermal cross-linking during the heating process, which reduces the subsequent recycling rate.

[0009] To address this, we propose a liquid crystal alignment agent waste liquid recycling and reuse device to overcome the shortcomings of the aforementioned temperature-controlled method. Utility Model Content

[0010] The purpose of this invention is to solve the problems in the prior art by proposing a liquid crystal alignment agent waste liquid recycling device. This device uses a combination design of gas supply pipe and gas extraction pipe to remove water by the dual action of non-reactive gas purging and vacuum pressure. This method will not cause any loss to the polymer in the liquid crystal alignment agent and effectively ensures the recycling efficiency.

[0011] To solve the above problems, this utility model provides the following technical solution:

[0012] A device for recycling and reusing liquid crystal alignment agent waste liquid includes a reaction vessel and a dehydration assembly. The dehydration assembly includes a gas supply pipe and a gas extraction pipe both disposed on the reaction vessel. The gas supply pipe is used to introduce non-reactive gas into the reaction vessel to remove water and organic solvents from the liquid crystal alignment agent. The gas extraction pipe is used to perform a vacuuming action on the inner cavity of the reaction vessel to reduce the vacuum degree of the inner cavity of the reaction vessel. The gas extraction pipe also constitutes an outlet channel for supplying non-reactive gas.

[0013] As a further embodiment of this utility model: an external condenser is provided on the air extraction pipe, and the external condenser is connected to a collection tank.

[0014] As a further aspect of this utility model, the device also includes a built-in condenser inside the reactor. The reactor is provided with a cylinder for accommodating the built-in condenser, and the cylinder is used to receive water and organic solvents liquefied on the surface of the built-in condenser.

[0015] As a further embodiment of this utility model: a discharge pipe extending to the outside of the reaction vessel is connected to the bottom end of the cylinder.

[0016] As a further embodiment of this utility model: the built-in condenser is configured as a condenser coil, and the exhaust pipe passes through the cylinder and is located in the middle of the condenser coil.

[0017] As a further embodiment of this utility model: multiple sets of the gas supply pipes are arranged in a circumferential array at the bottom edge of the reactor.

[0018] As a further aspect of this invention, the device also includes a stirring assembly disposed on the reactor and used to stir the inner cavity of the reactor.

[0019] As a further embodiment of this utility model: the stirring assembly includes a drive motor located at the top of the reactor, and the output shaft of the drive motor extends into the inner cavity of the reactor and is equipped with a transfer frame. A stirring ring is fixedly provided at the bottom of the transfer frame, and multiple paddles are arranged in a circumferential array on the stirring ring.

[0020] As a further embodiment of this utility model: the top of the reactor is provided with a feed pipe extending into its inner cavity at one end.

[0021] As a further embodiment of this utility model: the bottom of the reactor is provided with a transfer pipe with one end communicating with its inner cavity.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. Water removal is achieved through the combined action of non-reactive gas purging and vacuum pumping. Non-reactive gas is introduced into the gas supply pipeline to remove water / organic solvent vapors from the waste liquid, while the gas extraction pipeline simultaneously reduces the vacuum level of the reactor, significantly improving the volatilization efficiency. This process does not cause any loss to the polymer in the liquid crystal alignment agent, effectively ensuring the recovery efficiency.

[0024] 2. The extraction pipe is reused as a non-reactive gas outlet, which simplifies the structure and forms a gas circulation path to avoid gas stagnation.

[0025] 3. Add an external condenser to achieve cascade condensation and recovery: The gaseous organic solvents and water carried out by the exhaust pipe are directly condensed and connected to a collection tank for easy resource recovery. This design effectively prevents volatile substances from entering the corresponding vacuum equipment.

[0026] 4. Built-in condenser combined with a cylindrical design enables active condensation inside the reactor: Volatile components are directly condensed inside the reactor, while the cylindrical body acts as a collection container to catch the condensate, preventing it from dripping back into the waste liquid and causing secondary pollution. The combined use of built-in and external condensers complements each other, enhancing separation efficiency.

[0027] 5. The built-in condenser is optimized into a spiral coil shape to maximize the condensation surface area; the exhaust pipe runs through the cylinder and is centrally located, allowing gas to pass evenly through the coil gaps and improving condensation efficiency. The structure is compact and facilitates airflow distribution.

[0028] 6. Multiple sets of circumferentially arrayed gas supply pipes form a ring-shaped gas distribution network at the bottom of the vessel, ensuring that non-reactive gases penetrate the waste liquid layer uniformly, avoiding localized drying or dead zones, and significantly improving gas-liquid contact efficiency and dehydration uniformity.

[0029] 7. The introduction of the stirring component is designed to address the characteristics of high-viscosity waste liquids. It forcibly breaks the surface tension of the liquid layer, accelerates the escape of water / organic solvent molecules, and promotes the mixing of non-reactive gases with waste liquids, thus solving the problem of low static treatment efficiency.

[0030] 8. The stirring structure adopts a combination of frame and annular vane: the transition frame enhances structural stability, and the circumferential vane generates a radial and tangential composite flow field, effectively dispersing bubbles and expanding the gas-liquid interface. The stirring ring is selected in an annular configuration to avoid interference with the installation position of the cylinder. Attached Figure Description

[0031] The present invention will be further described below with reference to the accompanying drawings.

[0032] Figure 1 This is a cross-sectional structural schematic diagram of the present invention;

[0033] Figure 2 This is a top view schematic diagram of the stirring ring and the swivel plate of this utility model;

[0034] Figure 3 This is a schematic diagram of the waste liquid treatment process of this utility model.

[0035] In the diagram: 1. Reactor; 2. Gas supply pipe; 3. Gas extraction pipe; 4. External condenser; 5. Internal condenser; 6. Shell; 7. Discharge pipe; 8. Drive motor; 9. Adapter frame; 10. Stirring ring; 11. Paddle; 12. Feed pipe; 13. Adapter pipe; 14. Raw material tank; 15. Coarse filter; 16. Cation exchange resin unit; 17. Compounding vessel; 18. Fine filter. Detailed Implementation

[0036] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0037] like Figures 1-3 As shown, a method for treating liquid crystal alignment agent waste liquid generally includes the following steps:

[0038] Step 1: The waste liquid temporarily stored in the raw material tank 14 is subjected to coarse filtration through the coarse filter 15. This is to remove insoluble particulate impurities from the waste liquid to avoid blockage and damage to pumps and pipelines during subsequent transportation.

[0039] Step 2: The waste liquid treated in Step 1 is transported to the dewatering device. After being treated by the dewatering device, the waste liquid will be separated into light components (water and organic solvents) and heavy components.

[0040] Step 3: The heavy components are transported to the cation exchange resin device 16, which removes metal ion impurities from the heavy components.

[0041] Step 4: The recombinant components processed in Step 3 are transported to the compounding reactor 17, and relevant organic solvents are added to it to achieve the same non-volatile content, viscosity, etc. as the liquid crystal alignment agent stock solution.

[0042] Step 5: The recombinant components processed in Step 4 are subjected to fine filtration through fine filter 18 to obtain liquid crystal alignment agent repair solution.

[0043] like Figures 1-2 As shown, the dehydration device described above includes a reactor 1 and a dehydration assembly. A feed pipe 12, extending from the top of the reactor 1 into its inner cavity, is connected at the other end to a raw material tank 14 via a pump. The pump can pump the waste liquid from the raw material tank 14 into the reactor 1. The dehydration assembly includes a gas supply pipe 2 and a gas extraction pipe 3, both mounted on the reactor 1 and extending at one end into the inner cavity of the reactor 1. The gas supply pipe 2 is used to supply non-reactive gas (nitrogen can be selected) into the reactor 1; the gas extraction pipe 3 is used to perform a suction action into the inner cavity of the reactor 1 to ensure a certain degree of vacuum within the reactor 1. The presence of this vacuum allows the water and organic solvents in the waste liquid to be in a volatile state.

[0044] During the dehydration process, the extraction pipe 3 evacuates the reactor 1 to maintain a certain vacuum level within its cavity. The supply pipe 2 delivers nitrogen gas to the reactor 1. The nitrogen enters the waste liquid, carrying away water and organic solvents, and flows to the top of the waste liquid. At this point, the water and organic solvents are in the gas phase and together constitute the light component, while the waste liquid, having lost water and organic solvents, becomes the heavy component. Simultaneously, the extraction pipe 3 also serves as an outlet channel, supplying nitrogen gas containing water and organic solvents to exit the reactor 1, thus separating the light and heavy components. Furthermore, a transfer pipe 13, with one end connected to the inner cavity of the reactor 1, is installed at the bottom of the reactor 1. This transfer pipe 13 allows the heavy components to be transported to the cation exchange resin device 16 for further processing.

[0045] To increase the amount of water and solution carried away by nitrogen in the waste liquid per unit time, multiple sets of gas supply pipes 2 can be placed at the bottom edge of the reactor 1 in a circumferential array.

[0046] When the extraction pipe 3 is used as an outlet channel, to prevent the water and organic solvents in the gas phase from interfering with the vacuuming operation, this invention includes an external condenser 4 on the extraction pipe 3. The external condenser 4 is connected to a collection tank. The external condenser 4 can liquefy the water and organic solvents in the gas phase inside the extraction pipe 3, and the liquefied water and organic solvents are collected in the collection tank. It should be noted that the external condenser 4 is a conventional technical means in the prior art, and will not be described in detail here to avoid cumbersome writing.

[0047] Based on the shortcomings of using the aforementioned extraction pipe 3 as an outlet channel, this utility model adds a channel for nitrogen discharge. Specifically, a cylinder 6 is provided inside the reactor 1, and a built-in condenser 5 is installed inside the cylinder 6. A discharge pipe 7 extending to the outside of the reactor 1 is connected to the bottom end of the cylinder 6. When nitrogen is introduced into the waste liquid and escapes to the top of the waste liquid, the waste liquid contains gaseous water and organic solvents. When it encounters the built-in condenser 5, it will liquefy on its surface and flow into the cylinder 6 in the form of water droplets, and then be discharged from the reactor 1 through the discharge pipe 7 at the bottom of the cylinder 6.

[0048] In summary, based on the added discharge pipe 7, nitrogen can be discharged through two channels, building upon the existing gas outlet channel.

[0049] Preferably, both the external condenser 4 and the internal condenser 5 are conventional technologies in the prior art. When the internal condenser 5 is set as a condenser coil, the extraction pipe 3 can be placed in the middle of the condenser coil. At the same time, one end of the extraction pipe 3 is inserted into the cylinder 6. When the extraction pipe 3 is working, a certain negative pressure is generated inside the cylinder 6, causing nitrogen gas containing water and organic solvents to tend to flow into the inner cavity of the cylinder 6. That is, a large amount of nitrogen gas containing water and organic solvents will act on the internal condenser 5 per unit time, achieving rapid liquefaction.

[0050] Furthermore, to improve dewatering efficiency, this invention also includes a stirring assembly on the reactor 1. The stirring assembly is used to stir the waste liquid inside the reactor 1. Specifically, the stirring assembly includes a drive motor 8 located at the top of the reactor 1, and the output shaft of the drive motor 8 extends into the reactor 1 and is fitted with a transfer frame 9. A stirring ring 10 is fixedly mounted at the bottom of the transfer frame 9, and the stirring ring 10 has multiple paddles 11 arranged in a circumferential array. This annular arrangement of the stirring ring 10 is intended to avoid interference with the installation position of the cylinder 6.

[0051] The following is an example of a water removal scenario:

[0052] (1) Take 50 kg of liquid crystal alignment agent waste liquid from raw material tank 14. It is found that the waste liquid contains 5.4 wt% non-volatile matter, 60.1 wt% N-methylpyrrolidone, 25.1 wt% ethylene glycol butyl ether, a total metal ion content of 964 ppb, and a water content of 9.3 wt%.

[0053] (2) The above waste liquid is subjected to coarse filtration through coarse filter 15 to remove insoluble particulate impurities in the waste liquid.

[0054] (3) Next, the waste liquid after coarse filtration is transported to the reactor 1 through the feed pipe 12. The temperature of the reactor 1 is set to 25°C, the temperature of the built-in condenser 5 is set to -10°C, and the temperature of the external condenser 4 is set to -40°C.

[0055] (4) Nitrogen gas is introduced into the waste liquid through the gas supply pipe 2 at a flow rate of 6L / min. During this process, the nitrogen gas will carry away the water in the waste liquid upward. Then, the suction pipe 3 is used to perform a suction action to make the vacuum degree of the inner cavity of the reactor 1 2000Pa and maintain it for 4 hours. After that, the water content in the waste liquid is sampled and tested until the water content is reduced to 2wt%.

[0056] (5) Close the gas supply pipe 2, start the stirring assembly, and add 1 kg of electronic-grade methanol (azeotropic organic solvent) to the reactor 1 while stirring. After adding the methanol, open the gas supply pipe 2 again and continue to introduce nitrogen into the waste liquid at a flow rate of 6 L / min. During this process, the water and azeotropic organic solvent in the waste liquid, as light components, will be carried away by the nitrogen and discharged from the reactor 1 through the gas outlet channel and the discharge pipe 7. After 6 hours of treatment, take a sample for testing. When the moisture content drops below 1500 ppm and the methanol content is below 0.01 wt%, close the gas supply pipe 2 and the extraction pipe 3, and pump the remaining heavy components into the cation exchange resin device 16. The cation exchange resin device 16 will absorb the metal ions in the heavy components.

[0057] (6) After the heavy components are processed in the cation exchange resin device 16, they enter the compounding kettle 17. Samples are taken to test the content of non-volatile substances and organic solvent components. 3899g of organic solvent NMP and 5446g of organic solvent BC are added. Stir for 30 minutes to complete the compounding.

[0058] (7) After filtration through fine filter 18, first open the circulation valve and close the finished product valve, circulate for 10 minutes, compact the filter element, then open the finished product valve and close the circulation valve, and finally obtain 46kg of liquid crystal alignment agent repair liquid product with a recovery rate of 92%.

[0059] The composition analysis of the liquid crystal alignment agent waste liquid before treatment, the liquid crystal alignment agent repair liquid after treatment, and the standard product specifications is shown in Table 1 below:

[0060]

[0061] Table 1

[0062] In Table 1 above, the liquid crystal alignment agent stock solution represents the unopened and unused finished product, which is used to compare with the liquid crystal alignment agent waste liquid before treatment and the liquid crystal alignment agent repair solution after treatment. As can be seen from Table 1, the content of each component in the liquid crystal alignment agent repair solution after treatment is within the qualified range.

[0063] The molecular weight comparison of liquid crystal alignment agent stock solution, liquid crystal alignment agent waste solution, and liquid crystal alignment agent repair solution is shown in Table 2 below:

[0064] Liquid crystal alignment agent name Mp (g / mol) Mn(g / mol) Mw(g / mol) PD Liquid crystal alignment agent stock solution 131466 81919 118857 1.451 Liquid crystal alignment agent waste liquid 129834 83303 118488 1.422 Liquid crystal alignment agent repair solution 128222 82178 117326 1.428

[0065] Table 2

[0066] As shown in Table 2 above, the molecular weight of the treated liquid crystal alignment agent repair solution is close to that of the original liquid crystal alignment agent solution.

[0067] The above description provides a detailed account of one embodiment of the present invention. However, this description is merely a preferred embodiment and should not be construed as limiting the scope of the present invention. All equivalent variations and improvements made within the scope of the claims of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A liquid crystal alignment agent waste liquid recycling device characterized by comprising: The reactor includes a reaction vessel (1) and a dehydration assembly. The dehydration assembly includes a gas supply pipe (2) and a gas extraction pipe (3) both located on the reaction vessel (1). The gas supply pipe (2) is used to introduce non-reactive gas into the reaction vessel (1) to remove water and organic solvent from the liquid crystal alignment agent. The gas extraction pipe (3) is used to perform a vacuuming action on the inner cavity of the reaction vessel (1) to reduce the vacuum level in the inner cavity of the reaction vessel (1). The gas extraction pipe (3) also constitutes an outlet channel for supplying non-reactive gas.

2. The liquid crystal alignment agent waste liquid recycling and reuse device according to claim 1, characterized in that, An external condenser (4) is provided on the air extraction pipe (3), and the external condenser (4) is connected to a collection tank.

3. The liquid crystal alignment agent waste liquid recycling and reuse device according to claim 1, characterized in that, The device also includes a built-in condenser (5) disposed in the reactor (1), wherein the reactor (1) is provided with a cylinder (6) for accommodating the built-in condenser (5), and the cylinder (6) is used to receive water and organic solvents liquefied on the surface of the built-in condenser (5).

4. The liquid crystal alignment agent waste liquid recycling and reuse device according to claim 3, characterized in that, The bottom end of the cylinder (6) is connected to a discharge pipe (7) that extends to the outside of the reactor (1).

5. The liquid crystal alignment agent waste liquid recycling and reuse device according to claim 3, characterized in that, The built-in condenser (5) is configured as a condenser coil, and the exhaust pipe (3) passes through the cylinder (6) and is located in the middle of the condenser coil.

6. A liquid crystal alignment agent waste liquid recycling and reuse device according to any one of claims 1-3, characterized in that, Multiple sets of gas supply pipes (2) are arranged in a circumferential array at the bottom edge of the reactor (1).

7. A liquid crystal alignment agent waste liquid recycling and reuse device according to any one of claims 1-3, characterized in that, The device also includes a stirring assembly disposed on the reactor (1) and used to stir the inner cavity of the reactor (1).

8. The liquid crystal alignment agent waste liquid recycling and reuse device according to claim 7, characterized in that, The stirring assembly includes a drive motor (8) located at the top of the reactor (1), and the output shaft of the drive motor (8) extends into the inner cavity of the reactor (1) and is fitted with a transfer frame (9). A stirring ring (10) is fixedly installed at the bottom of the transfer frame (9), and multiple paddles (11) are arranged in a circumferential array on the stirring ring (10).

9. A liquid crystal alignment agent waste liquid recycling and reuse device according to any one of claims 1-3, characterized in that, The reactor (1) is provided with a feed pipe (12) at the top, one end of which extends into its inner cavity.

10. A liquid crystal alignment agent waste liquid recycling and reuse device according to any one of claims 1-3, characterized in that, The bottom of the reactor (1) is provided with a transfer pipe (13) that communicates with its inner cavity at one end.

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