JP2010089075A - Method of recovering liquid crystal from waste lcd panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of continuously recovering a liquid crystal from a waste panel and a device to be used for this method. <P>SOLUTION: This method includes (i) a process to crush a waste LCD panel, then dissolve the liquid crystal and a cell material, both of the waste LCD panel in a solvent by soaking the crushed waste LCD panel in the solvent and thereby, form an extraction liquid, (ii) a process to cool the extraction liquid in order to lower the solubility of the cell material and easily remove the cell material from the extraction liquid by filtering and adsorption, (iii) a process to form the recovered solvent by forming a solvent vapor through heating the extraction liquid and condensing the solvent vapor, (iv) a process to form the extraction liquid by soaking the crushed waste LCD panel in the recovered solvent, and (v) a process to repeat the processes (ii) to (iv) until none of the liquid crystal remains in the crushed waste LCD panel. Also, a recovery device to execute the above method is provided. The recovered liquid crystal shows a low residual solvent content and also, a low impurity content ratio, as well as the recovery of not less than 95%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  This application is filed with Taiwan Patent Application No. 097130508 filed on August 11, 2008, Taiwan Patent Application No. 098125319 filed on July 28, 2009, and Korean Patent Application No. 10- filed on December 31, 2008. No. 2008-0137744, all of which are hereby incorporated by reference.

  The present invention relates to a liquid crystal recovery method and apparatus for LCD waste panels, and more particularly, to recycling extraction of extracted liquid crystal.

  A liquid crystal display (hereinafter sometimes referred to as LCD) is thin, lightweight, low power consumption, non-radioactive, and has advantages such as compatibility with semiconductor processes. And the amount of waste is increasing dramatically. Although the long-term adverse effects of liquid crystal waste are unknown, incineration or landfilling of LCD panels with liquid crystals can contaminate the environment. The proportion of the liquid crystal in the LCD panel is only 0.1% by mass to 0.2% by mass, but the presence of this liquid crystal prevents the reuse of the LCD glass panel. In addition, Taiwan is currently one of the world's leading LCD panel producers, and according to the Waste Electrical and Electronics Equipment Directive (WEEE) established by the European Union in 2003, producers and sellers It is required to reuse the products that are manufactured and sold. The amount of LCD waste panels is expected to increase in the future, and efficient recovery of liquid crystals from the LCD waste panels and reuse of the recovered liquid crystals achieve economic effects and environmental protection.

  In recent years, many patents relating to the handling of waste panels have been published. In Patent Document 1 (Japanese Patent Laid-Open No. 2001-337305), the polarizing plate is peeled off by hand, the sealing agent is cut, the panel is pulverized, and then the liquid crystal of the panel is recovered by solvent cleaning. This method is complicated because the polarizing plate and the sealant must be removed in advance, and a large amount of solvent is consumed for solvent cleaning.

  In patent document 2 (Unexamined-Japanese-Patent No. 2002-166259), the liquid crystal is isolate | separated from water by melt | dissolving a liquid crystal in hot water, and cooling a liquid crystal solution to room temperature after that. However, the present inventors have found that many liquid crystals are difficult to dissolve in warm water, and that this method consumes a lot of heat to recover a low yield of liquid crystals.

  In Patent Document 3 (Japanese Patent Application Laid-Open No. 2002-254059), a waste liquid crystal panel is crushed by electro-separation in water, and the liquid crystal of the waste panel is washed with a solvent. Here, dissolution of the liquid crystal is supported by ultrasonic treatment or stirring, and then the liquid crystal solution is dried to recover the liquid crystal. After pulverization of the waste panel by electrical separation, the cell material of the waste panel (including sealant, color filter, spacer, ITO film, black matrix and PI) is dissolved in the solvent. However, this method does not mention the problem of the cell material dissolved in the solvent and the method for purifying the liquid crystal. That is, the recovered liquid crystal contains many cell materials, and the recovered liquid crystal cannot be reused as it is.

  In Patent Document 4 (Taiwan Patent Application Publication No. 2004-04484), first, the sealant of the waste panel is removed, and then the liquid crystal is dissolved in a solvent, or by blowing or centrifuging. Collecting. Thereafter, impurities in the liquid crystal are removed by vacuum distillation, or ionic components in the liquid crystal are removed by an adsorbent. Finally, the recovered liquid crystal is added to the liquid crystal monomer corresponding to the raw liquid crystal composition. This method is complicated because the sealant must be removed in advance to prevent contamination. Further, purification is performed by chromatography, and the recovered liquid crystal cannot be reused as it is without adding liquid crystal monomers. This method is therefore complex and expensive.

  In Patent Document 5 (Japanese Patent Laid-Open No. 2006-089605), a liquid crystal taken out from a waste panel with a mixed solvent of a polar solvent and a nonpolar solvent is purified by chromatography. Chromatography is unsuitable for mass recycling, and in order to reuse the recovered liquid crystal, liquid crystal monomer must be added to the recovered liquid crystal.

  In Patent Document 6 (Japanese Patent Laid-Open No. 2006-184376), liquid crystals and organic substances contained in a waste panel are vaporized by vacuum heating, and carrier gas, vaporized liquid crystals, and vaporized organic substances are separated by condensation. ing. In this method, since the waste panel is not directly pulverized, the liquid crystal and other organic matter such as cell material are simultaneously recovered from the waste panel by vacuum heating. This method also does not describe any method for purifying the recovered liquid crystal. Therefore, the recovered liquid crystal contains a large amount of cell material, and the recovered liquid crystal cannot be reused as it is.

JP 2001-337305 A JP 2002-166259 A JP 2002-254059 A Taiwan Patent Application Publication No. 2004-04484 JP 2006-089605 A JP 2006-184376 A Taiwan Patent No. I282359 Specification Taiwan Patent I297282 Specification

  As described above, the methods described in the above-mentioned patent documents have problems that the process is complicated, only specific liquid crystals can be used, or the composition ratio of the liquid crystals changes. There was room for further improvement. Accordingly, the present invention provides a method for continuously recovering liquid crystal from waste panels and an apparatus used in the method. The present invention can be applied to the processing of many commercially available liquid crystal panels. The recovered liquid crystal has a low impurity content and the same composition as the original liquid crystal. Furthermore, the recovered liquid crystal purified by the method disclosed in Patent Document 7 (Taiwan Patent I282359) and Patent Document 8 (Taiwan Patent I297282) can be reused as it is without adding any liquid crystal monomer. can do.

  The present invention includes (i) crushing an LCD waste panel and immersing the crushed LCD waste panel in a solvent to dissolve liquid crystal and cell material of the LCD waste panel to form an extract; (ii) cell Cooling the extract to reduce the solubility of the material, then filtering and adsorbing the extract; (iii) heating the extract to form a solvent vapor and condensing the solvent vapor. Forming a recovered solvent; (iv) immersing the crushed LCD waste panel in the recovered solvent to form an extract; and (v) ending the liquid crystal in the crushed LCD waste panel. Provided is a liquid crystal recovery method for an LCD waste panel, which includes a step of repeating steps (ii) to (iv) to remove a solvent in an extract to obtain a recovered liquid crystal.

  The present invention also provides a liquid crystal recovery device for LCD waste panels. The liquid crystal recovery device for the LCD waste panel includes an extraction tank having a filtration-adsorption device below the bottom surface; a temperature control device provided in the extraction tank or between the filtration device and the filtration-adsorption device; A collection tank having a heating device for heating the tank; a first storage tank provided at an upper part of the extraction tank and connected to the extraction tank; a first storage tank provided at a lower part of the extraction tank and the filtration-adsorption device 2 storage tanks; connected to each of the collection tank and the extraction tank, and having a condenser provided at the upper part of the collection tank and the extraction tank, the extraction tank, the collection tank, and the second storage tank, Each is connected to a three-way valve by a pipe, and the filtration-adsorption device is provided between the extraction tank and the three-way valve.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The invention will be more fully understood by reading the following detailed description and examples together with the reference symbols appended to the accompanying drawings.
FIG. 1 is a flowchart showing one embodiment of the liquid crystal recovery process of the LCD waste panel of the present invention. FIG. 2 is a diagram showing an embodiment of the liquid crystal recovery device for the LCD waste panel of the present invention. FIG. 3 is a GCMS spectrum diagram of the original liquid crystal TN-Q1 in Experimental Example 1 of the present invention. FIG. 4 is a GCMS spectrum diagram of the recovered liquid crystal in Experimental Example 1 of the present invention. FIG. 5 is a GCMS spectrum diagram of the recovered liquid crystal after the cooling and filtration-adsorption steps of Experimental Example 1 of the present invention. FIG. 6 is a GCMS spectrum diagram of the recovered liquid crystal in Experimental Example 2 of the present invention. FIG. 7 is a GCMS spectrum diagram of the original liquid crystal VA-C1 in Experimental Example 3 of the present invention. FIG. 8 is a GCMS spectrum diagram of the recovered liquid crystal in Experimental Example 3 of the present invention. FIG. 9 is a GCMS spectrum diagram of the original liquid crystal VA-C2 in Experimental Example 4 of the present invention. FIG. 10 is a GCMS spectrum diagram of the recovered liquid crystal in Experimental Example 4 of the present invention.

  The following description is considered to be the best mode for carrying out the invention. The description is intended to illustrate the general principles of the invention and is not intended to limit the invention. The scope of the invention is defined by the appended claims.

FIG. 1 is a flow chart illustrating the method of the present invention for recovering liquid crystals from a waste LCD panel. First, in order to form an extract, the LCD waste panel is crushed and immersed in a solvent to dissolve the liquid crystal of the LCD waste panel in the solvent. LCD waste panel sources are scrap products from factory processes and recycled products used for a period of time. In the present invention, the LCD waste panel may be directly crushed or may be disassembled and the LCD panel frame removed. Here, the cell material such as the sealant remains in the LCD panel frame unless it is removed in advance. The size of the LCD waste panel after being crushed is preferably, for example, less than 100 cm ² . _Examples of the solvent used in the present invention include C _6-10 alkanes such as n-hexane, C _3-5 alcohols such as isopropanol, C _2-4 ethers such as ethyl ether, acetone, butanone or pentanone. C _3-5 ketones such as these, or a mixed solvent thereof (co-solvents). It should be noted that in the present invention, the liquid crystal is dissolved by a dipping method, not a flushing method. In the flushing method, the solvent cannot enter the gap between the crushed LCD waste panels and dissolve the liquid crystal present there, and the recovery efficiency decreases. In contrast, in the immersion method, the solvent can flow into the gap between the LCD waste panels. In one embodiment, in the immersion method, the surface of the solvent is higher than the top of the crushed LCD waste panel. The immersion time is, for example, between 10 minutes and 1 hour. In this step, part of the cell material is also dissolved in the solvent.

  Thereafter, the extract is cooled to reduce the solubility of the cell material, and the cell material is precipitated from the extract as a solid. The deposited cell material and the extract are subjected to solid-liquid separation, and then the extract is passed through a filtration-adsorption device in order to remove impurities in the extract. The cooling step is performed between 10 ° C. and −60 ° C., for example. The filtration-adsorption process is performed by natural filtration (gravity) or pressure filtration using an inert gas such as nitrogen, helium, argon or a mixture thereof having a purity of 99.99%. Can do.

  Thereafter, the filtrate (filtrate) after filtration and adsorption is heated to evaporate the solvent. The condensed vapor is again used to dip the crushed LCD waste panel to form a second batch extract. In order to reuse the crushed LCD waste panel as a solvent for immersing, the second batch extract is cooled to precipitate the cell material, filtered, adsorbed and then heated. The cycle is repeated, for example, 2 to 10 times until there is no liquid crystal on the crushed LCD waste panel. Finally, the extract is heated to vaporize the solvent, the solvent vapor is condensed to form a recovered solvent, and stored in a storage tank. Therefore, even if a complicated purification process is not performed, the collection tank contains only high-purity recovered liquid crystals.

  The recovered liquid crystal is then placed in a hood and the residual solvent is evaporated. In one aspect, the solvent is removed by heating or blowing an inert gas such as high purity nitrogen, helium, argon, or mixtures thereof. An inert gas is used to remove the solvent. Also, reactions between the solvent and inert gas should be avoided. Cell material is deposited in the cooling process, and impurities are removed in the filtration-adsorption process. Therefore, the recovered liquid crystal after removing the residual solvent has a recovery rate of 95% or more and the same purity as the original material. Yes. The recovered liquid crystal according to the present invention and the commercially available liquid crystal have the same characteristics and composition. If metal ions and water are removed from the recovered liquid crystal, the recovered liquid crystal can be used as it is without adding any liquid crystal monomer.

  The present invention also provides an apparatus for recovering the liquid crystal of the LCD waste panel shown in FIG. The apparatus of the present invention includes an extraction tank 11, storage tanks 12 and 14, and a collection tank 13. The extraction tank 11 and the collection tank 13 are connected by a pipe 18A. The filtration plate 22, the valve 43, and the filtration-adsorption device 15 are continuously provided under the extraction tank 11. The apparatus of the present invention further includes a condensing device 17 connected to each of the collection tank 13 and the storage tank 12 by pipes 18B and 18C. For example, the relative height of the collection tank 13 and the filtration-adsorption device 15 can be adjusted so that the distance between the collection tank 13 and the condenser device 17 is shortened (the same applies to the distance to the pipe 18B). ). When the pipe 18B is short, the energy consumption for vaporizing the solvent is reduced. When the collection tank 13 is provided at a position lower than the filtration-adsorption device 15, the filtered and adsorbed extract liquid can flow into the collection tank 13 by gravity. On the other hand, when the collection tank 13 is provided at a position higher than the filtration-adsorption device, a pump 16 connected to the three-way valve 29 and the collection tank 13 is required to pump the extract into the collection tank 13. There is.

  The solvent can be supplied to the storage tank 12 through the refill valve 24. The solvent in the storage tank is caused to flow into the extraction tank 11 through the valve 42, and the liquid crystal of the crushed panel and the cell member are dissolved in the solvent to form an extract. The extract is cooled and then flows into the collection tank 13 through the filtration plate 22, the valve 43, the filtration-adsorption device 15, the three-way valve 29, the pipe 18 </ b> A and the valve 44. The solvent in the collection tank 13 may be heated to be sent to the condenser 17 through the pipe 18B, and the solvent vapor is condensed into droplets and flows into the storage tank 12 through the pipe 18C and the valve 41. This completes the solvent cycle. The solvent may be added not only to the storage tank 12 but also to the collection tank 13 from the beginning via the supply valve 25. The solvent cycle in this case is the same as described above. The device of the present invention further includes a pneumatic device and a storage tank 14 for storing the solvent after liquid crystal recovery. The pneumatic device includes a gas cylinder 31 for pressurizing and filtering the extract, an atmospheric pressure controller 33, and a pipe 32 connecting both. During the pressure filtration, the atmospheric pressure controller 33 may control the pressure of the extraction tank 11 to be 0 psi to 60 psi (0 to 413.686 kPa). In the pressurization-filtration step, the valve 41 must be closed when maintaining the pressure in the extraction tank 11, and after the pressurization-filtration step, the valve 41 is opened to release the pressure in the extraction tank 11. To do.

  The extraction tank 11 has an inlet / outlet 21. In addition, one in which the observation window 23 for observing whether or not the upper part of the crushed panel is covered with the solvent is provided on the side wall of the extraction tank 11 is one embodiment of the present invention. The injection / discharge port 21 is used to inject / discharge the crushed panel in the extraction tank 11, and the injection / discharge port 21 can take in and out 1 kg to 1000 kg in mass.

  The filtration plate 22 located under the extraction tank 11 is used in order to prevent mixing of glass pieces. The coarse impurities of the glass piece and the liquid crystal are filtered out by a filtration plate 22 having an appropriate pore size (for example, 0.2 μm to 10 μm). The filtration plate may be used with a filtration mesh to secure the filtration plate. Examples of the filtration mesh include stainless steel or plastic, and the pore diameter is 0.1 mm to 1 mm. Examples of the filtration plate include those made of polyethylene (PE), polypropylene (PP), or borosilicate glass (commercially available Pyrex (registered trademark)). The filtration device 15 may have a single layer structure or a multiple layer structure in order to remove other impurities. For example, examples of the multi-layer structure include a structure in which a filtration mesh, a filtration plate, an adsorbent, a filtration membrane, a filtration plate, and a filtration mesh are combined. The above-mentioned thing is mentioned as a raw material of a filtration plate and a filtration mesh. Examples of the filtration membrane include those made of polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE). Both are so-called Teflon (registered trademark). Moreover, it is preferable that a hole diameter is about 0.1 micrometer-0.5 micrometer. In one embodiment of the present invention, examples of the adsorbent include aluminum oxide, silicon oxide, aluminum silicate, and molecular sieve. The filtration material and the adsorbent adsorb impurities in the extract flowing into the collection tank 13 from the extraction tank 11.

  In one aspect of the present invention, a temperature control device is provided in the extraction tank to cool the extract and deposit the dissolved cell material as a solid. As another aspect, the temperature control device may be provided between the filtration plate 22 and the filtration-adsorption device 15, and in this case, the above-described function is exhibited.

  Actually, the solvent is put into the storage tank 12, and then the solvent is allowed to flow into the extraction tank 11, and the crushed LCD waste panel is immersed to form an extract. This extract contains liquid crystal dissolved in a solvent and some cell material. The extract is then cooled by a temperature control device. The gas for filtration is supplied from the gas cylinder 31 through the pipe 32 to the extraction tank 11 to pressurize and filter the extract. Next, the pressure is controlled by the atmospheric pressure controller 33, and the extract is filtered by the filtration plate 22 and the filtration-adsorption device 15 to remove impurities, and flows into the collection tank 13 through the pipe 18A. The extraction liquid is heated by the heating device 27 of the collection tank 13, and the solvent is turned into vapor to leave the liquid crystal in the collection tank 13. The heating temperature by the heating device 27 may be determined according to the boiling point of the solvent. The solvent vapor flows into the condenser 17 via the pipe 18B, where it is condensed into droplets. These droplets flow into the storage tank 12 from the pipe 18C. After all the extraction liquid in the extraction tank 11 has been cooled, filtered and adsorbed and all flowed into the collection tank 13, the valve 42 is opened to flow into the extraction tank 11, and the crushed LCD waste panel is recycled. The recovered solvent for forming the second batch extract is formed in the storage tank 12 by dipping. After the cooling step, the pressure-filtration step, and the adsorption step, the second batch extract is supplied to the collection tank 13 and is heated and condensed to recover the solvent. The cycle of immersion, cooling, filtration and adsorption, and solvent recovery described above is repeated until there is no liquid crystal on the crushed LCD waste panel. The collected liquid crystal in the collection tank 13 is discharged through the discharge valve 26 and collected. Finally, the solvent in the extraction tank 11 (which does not dissolve any liquid crystal) flows into the storage tank 14 instead of the collection tank 13 after filtration and adsorption. In one embodiment, the extract / solvent entering the collection tank 13 / storage tank 14 is controlled by a three-way valve 29.

  The pipes 18A, 18B, 18C, and 32 may be made of PTFE, stainless steel, or glass that is commercially available as Pyrex (registered trademark). The extraction tank 11, the collection tank 13, the condensing device 17, the storage tanks 12 and 14, and the filtration-adsorption device 15 are independent components and can be easily assembled and disassembled for cleaning and maintenance.

  The liquid crystal recovered by the above-described recovery method and apparatus of the present invention has a very low content of solvent and impurities, and the recovery rate is 95% or more.

  Therefore, the present invention has several advantages over the prior art. First, in the present invention, the waste panel is pulverized as it is without previously removing the cell material such as the sealant. This reduces the complexity of recovery. Second, since the method of the present invention uses an immersion method rather than a cleaning method to dissolve the liquid crystal, the amount of solvent used can be reduced and the solubility of the liquid crystal can be improved. Thirdly, in the present invention, the extract is cooled to deposit cell material dissolved in the extract, and solid-liquid separation can simplify the purification of the recovered liquid crystal. Finally, the recovered liquid crystal has a high purity and a composition ratio similar to that of the original liquid crystal that is commercially available. The liquid crystal simply purified by the method disclosed by the present inventors can be reused as it is without adding any liquid crystal monomer.

Experimental example 1
A piece of 15-inch LCD waste panel from a company was selected in this experimental example. The liquid crystal contained in these LCD waste panels was a twisted nematic type (abbreviated as TN-Q1) liquid crystal. In order to recycle the liquid crystal, the LCD waste panel was crushed and then extracted with acetone by the method shown in FIG. 1 and the recovery device of the present invention shown in FIG. Note that the recovery device used in Experimental Example 1 was not provided with the temperature control device and the filtration-adsorption device 15. First, 1000 mL of the crushed panel was set in the extraction tank 11 having a capacity of 2000 mL. Subsequently, 3000 mL of acetone as an extraction solvent was put into the storage tank 12, the valve 42 was opened, the solvent was allowed to flow into the extraction tank 11, and the crushed waste LCD panel was immersed for 30 minutes to form an extract. . After filtration through the filter plate 22, the extract was poured into the collection tank 13 and heated in a 90 ° C. water bath to evaporate acetone in the extract. Thereafter, acetone vapor was condensed, and the generated droplets were allowed to flow into the storage tank 12. After all the extraction liquid in the extraction tank 11 has flowed into the collection tank 13, in order to immerse the crushed waste LCD panel again, the valve 42 is opened and the recovered solvent in the storage tank 12 flows into the extraction tank 11. I let you. The cycle of heating the solvent, evaporating the solvent, condensing the solvent vapor, and immersing the LCD waste panel took 45 minutes. The above cycle was repeated three times to complete one extraction. And after removing acetone, the collect | recovered liquid crystal was obtained. The theoretical recovered liquid crystal mass was 6.3 g, the actual recovered liquid crystal mass was 6.6 g, and the recovery rate was 95% or more. FIG. 3 shows the spectrum of the original liquid crystal by gas chromatography mass spectrometry (hereinafter referred to as GCMS), and FIG. 4 shows the GCMS spectrum of the recovered liquid crystal. Table 1 shows the characteristics of the original liquid crystal. As shown from the comparison between FIG. 3 and FIG. 4, a large amount of impurities are present in the recovered liquid crystal that has not been subjected to the cooling and filtration-adsorption steps. The recovered liquid crystal was dissolved in acetone, cooled to −20 ° C., and then the impurities were removed by the filtration-adsorption device 15. Suitable adsorbents included molecular sieves, aluminum oxide and borosilicate glass. FIG. 5 shows a GCMS spectrum of the recovered liquid crystal that has undergone the cooling and filtration-adsorption process, and Table 1 shows the characteristics of the recovered liquid crystal that has undergone the cooling and filtration-adsorption process. From the comparison between FIG. 3 and FIG. 5, it can be seen that the impurities in the recovered liquid crystal are significantly reduced after cooling and filtration-adsorption treatment.

Experimental example 2
The recovery process of Experimental Example 2 is the same as that of Experimental Example 1, but the difference between Experimental Example 1 and Experimental Example 2 is that n-hexane is used as the extraction solvent instead of acetone, and the water bath temperature in the collection tank 13 is 85 ° C. It is lowered to. Furthermore, in Experimental Example 2, a temperature control device was provided in the extraction tank 11, and a filtration-adsorption device 15 was provided between the collection tank 13 and the extraction tank 11. A GCMS spectrum of the recovered liquid crystal in Experimental Example 2 is shown in FIG. As can be seen from the comparison between FIG. 3 and FIG. 6, the recovered liquid crystal of Experimental Example 2 has the same composition as the original liquid crystal.

Experimental example 3
A piece of 32-inch LCD waste panel from a company was selected in this experimental example. The liquid crystal contained in these LCD waste panels was a vertical alignment type (abbreviated as VA-C1) liquid crystal. In order to recover the liquid crystal by the method of the present invention shown in FIG. 1 and the recovery device of the present invention shown in FIG. 2, the LCD waste panel was crushed and extracted with n-hexane. First, the crushed panel 20L was set in an extraction tank having a capacity of 30L. Subsequently, 40 L of n-hexane as an extraction solvent was put into a storage tank, which was allowed to flow into the extraction tank 11, and the crushed LCD waste panel was immersed for 30 minutes to form an extract. After cooling and filtration-adsorption, the extract was poured into the collection tank 13 and heated in a 90 ° C. water bath to evaporate n-hexane in the extract. Thereafter, the vapor of n-hexane was condensed into droplets, and these droplets were allowed to flow into the storage tank 12. After all the extraction liquid in the extraction tank 11 has flowed into the collection tank 13, the valve 42 is opened to immerse the crushed LCD waste panel, and the recovered solvent in the storage tank 12 flows into the extraction tank 11. I let you. The cycle of heating the solvent, evaporating the solvent, condensing the vapor, immersing the LCD waste panel, cooling the extract to precipitate the cell material, and filtration-adsorption took 40 minutes. The above cycle was performed three times to complete one extraction. After extraction, n-hexane was stored in a storage tank and liquid crystal containing some solvent was drained from the collection tank. Then, the residual solvent was removed to obtain a recovered liquid crystal. The theoretical recovered liquid crystal mass was 76 g, the actual recovered liquid crystal mass was 74.5 g, and the recovery rate was 95% or more. The recovered liquid crystal was further purified by the method described in Taiwan Patent No. I282359 and Taiwan Patent No. I297282. Table 2 shows the characteristics of the original liquid crystal, recovered liquid crystal, and recovered liquid crystal after purification. FIG. 7 shows the GCMS spectrum of the original liquid crystal, and FIG. 8 shows the GCMS spectrum of the recovered liquid crystal. From comparison between FIG. 7 and FIG. 8, it can be seen that the recovered liquid crystal obtained in Experimental Example 3 and the original liquid crystal have the same composition. Furthermore, when the recovery of the LCD waste panel was scaled up to 670 pieces, the theoretical recovered liquid crystal mass was 670 g, the actual recovered liquid crystal mass was 650 g, and the recovery rate was 95% or more. The scaled up recovery required a longer recovery time. Further, the recovered liquid crystal had a GCMS spectrum similar to that in FIG. Therefore, the recovery method of the present invention is also suitable for mass recovery.

  Further, the original liquid crystal and the recovered liquid crystal purified by the method disclosed in Taiwan Patent No. I282359 and Taiwan Patent No. I297282 are injected into the test cell, respectively, and the reliability at the center and at the end is obtained. Tests and characteristics such as voltage holding ratio (VHR) were measured. Reliability evaluation (RA) was performed for a long time at high temperature. As shown in Table 3, the purified recovered liquid crystal and the original liquid crystal had similar VHR values before and after the RA test at both the center and end of the test cell. This means that the recovery method of the present invention is suitable for mass recovery.

Experimental Example 4
Two types of 32 inch LCD waste panels from a company were selected in this experimental example. The liquid crystals contained in these LCD waste panels were different vertical alignment types (abbreviated as VA-C1 and VA-C2). In order to recycle the liquid crystal, the LCD waste panel was crushed using the recovery device of the present invention shown in FIG. 2 and extracted with n-hexane. The conditions at the time of recovery and the amount of solvent used were the same as in Experimental Example 3. The theoretical recovered liquid crystal mass was 60 g, the actual recovered liquid crystal mass was 60 g, and the recovery rate was 95% or more. FIG. 10 shows a GCMS spectrum of the recovered liquid crystal after purification, and FIG. 9 shows the original liquid crystal (VA-C2). As can be seen from the comparison of FIGS. 7, 9, and 10, the recovered liquid crystal of Experimental Example 4 and the original liquid crystal have the same composition. From the high recovery rate of Experimental Example 4, it can be seen that the recovery method of the present invention is suitable for recovering liquid crystals from commercial waste panels.

  Although the present invention has been described with reference to experimental examples and preferred embodiments, the present invention is not limited thereto. Rather, various modifications and similar modifications obvious to those skilled in the art are included within the scope of the present invention. Therefore, the protection scope of the present invention is consistent with the broadest interpretation including all of these changes and modifications.

Claims (20)

A liquid crystal recovery method for LCD waste panels,
(I) crushing the LCD waste panel, immersing the crushed LCD waste panel in a solvent, and dissolving the liquid crystal and cell material of the LCD waste panel to form an extract;
(Ii) cooling the extract to reduce the solubility of the cell material, and then filtering and adsorbing the extract;
(Iii) heating the extract to form a solvent vapor, condensing the solvent vapor to form a recovered solvent;
(Iv) immersing the crushed LCD waste panel in the recovered solvent to form an extract; and
(V) repeating the steps (ii) to (iv) until no liquid crystal is left in the crushed LCD waste panel, and removing the solvent in the extract to obtain a recovered liquid crystal;
A method for recovering liquid crystal from an LCD waste panel.   The method for recovering liquid crystal of an LCD waste panel according to claim 1, wherein the crushing step of the LCD waste panel does not include prior removal of the sealant or the cell material. The LCD according to claim 1, wherein the solvent is a C _6-10 alkane, a C _3-5 alcohol, a C _2-4 ether, a C _3-5 ketone, or a combination thereof. Liquid crystal recovery method for waste panels.   The liquid crystal recovery method for an LCD waste panel according to claim 1, wherein, in the step (ii), the temperature at which the extract is cooled to deposit the seal member is 10 ° C to -60 ° C.   The method for recovering liquid crystal of an LCD waste panel according to claim 1, wherein the number of repetitions of steps (ii) to (iv) in step (v) is 2 to 10.   The liquid crystal recovery method for an LCD waste panel according to claim 1, further comprising a step of directly setting the recovered liquid crystal in a hood and removing a residual solvent in the recovered liquid crystal.   Furthermore, the liquid crystal collection method of the LCD waste panel of Claim 6 including the process of heating the collection | recovery liquid crystal in the said hood, and promoting the removal of a residual solvent.   The liquid crystal recovery method for an LCD waste panel according to claim 6, further comprising a step of blowing an inert gas to the recovered liquid crystal in the hood to remove residual solvent.   9. The liquid crystal recovery method for an LCD waste panel according to claim 8, wherein the inert gas is high-purity (> 99.99%) nitrogen, helium, argon, or a mixture thereof.   The liquid crystal recovery method for an LCD waste panel according to claim 1, wherein the filtration of the extract in the step (ii) is a pressure-filtration step.   The liquid crystal recovery method for an LCD waste panel according to claim 1, wherein the recovered liquid crystal can be used directly without adding a liquid crystal monomer. A liquid crystal recovery device for LCD waste panels,
An extraction tank having a filtration-adsorption device at the bottom of the bottom;
A temperature control device provided in the extraction tank or between the filtration device and the filtration-adsorption device;
A collection tank having a heating device for heating the collection tank;
A first storage tank provided at an upper part of the extraction tank and connected to the extraction tank;
A second storage tank provided below the extraction tank and the filtration-adsorption device;
A condenser connected to each of the collection tank and the extraction tank, and provided in the upper part of the collection tank and the extraction tank;
The extraction tank, the collection tank, and the second storage tank are each connected to a three-way valve by a pipe, and
A liquid crystal recovery device for an LCD waste panel, wherein the filtration-adsorption device is provided between the extraction tank and the three-way valve.   The extraction tank further has an injection / discharge port for injecting / discharging the crushed panel into / from the extraction tank, and an allowable injection / discharge mass of the injection / discharge port is 1 kg to 1000 kg. The liquid crystal recovery device for an LCD waste panel according to claim 12.   The liquid crystal recovery device for an LCD waste panel according to claim 12, wherein the filtration-adsorption device comprises a filtration plate, an adsorbent, a filtration membrane, and a filtration mesh.   The filtration plate has a pore size of 0.2 μm to 10 μm, the filtration plate is made of polyethylene, polypropylene, or borosilicate glass, and the filtration membrane has a pore size of 0.1 μm to 0.5 μm. The liquid crystal recovery device for an LCD waste panel according to claim 14, wherein the filtration membrane is made of polyvinylidene fluoride or polytetrafluoroethylene.   The liquid crystal recovery device for an LCD waste panel according to claim 14, wherein the adsorbent is aluminum oxide, silicon oxide, aluminum silicate, borosilicate glass or molecular sieve.   15. The liquid crystal recovery device for an LCD waste panel according to claim 14, wherein the pore size of the filtration mesh is 0.1 mm to 1 mm, and the filtration mesh is made of stainless steel or plastic.   The liquid crystal recovery device for an LCD waste panel according to claim 12, further comprising an air compression device connected to the extraction tank.   The liquid crystal recovery device for an LCD waste panel according to claim 12, wherein the filtration-adsorption device is provided at a position higher than the collection tank.   The LCD waste panel according to claim 12, wherein the filtration-adsorption device is provided at a lower position than the collection tank, and further includes a pump connected to each of the collection tank and a three-way valve. Liquid crystal recovery device.

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