JP7457086B2 - Waste polarizing plate collection system and method - Google Patents

Description

The present invention relates to a waste collection system, and particularly to a waste polarizing plate collection system and method.

Polarizer is one of the main raw materials of liquid crystal display (LCD), and its structure can include a polarizing layer, upper and lower adhesive layers, upper and lower protection/release layers, and a reflective film. can. The above-mentioned polarizing layer is basically made by dyeing and stretching PVA (polyvinyl alcohol) film, and this layer is the main part of the polarizing plate, and it affects the polarizing performance and transmission of the polarizing plate. At the same time, it also affects the color tone and optical durability of the polarizing plate. After cleaning, the other upper and lower protective/mold release layers and reflective film plastic can be recovered and used for processing. The dyeing material for the polarizing layer mentioned above is usually iodine, but since iodine sublimates with a small amount of heat, purple smoke is generated when waste polarizing plates are incinerated, causing environmental protection problems. It is already prohibited to process waste polarizers in this way. Therefore, how to dispose of waste polarizing plates has become a focus of research in various fields. In addition, polarizing plates have complicated components, making them difficult to classify, and fluffy waste polarizing plates occupy space, making it difficult to collect them.

The present invention provides a waste polarizing plate recovery system that can not only remove iodine within the polarizing plate, but also recover and reuse iodine and plastic.

The present invention also provides a waste polarizing plate recovery method that can reduce recovery costs by purifying and concentrating the extracted iodine ion solution and recovering the solvent for reuse.

The waste polarizing plate recovery system of the present invention includes a first extraction unit, a first separation unit, a second extraction unit, a second separation unit, and a purification and concentration system. The first extraction unit is used to receive the iodine-containing waste polarizer fragments and extract the iodine-containing waste polarizer fragments using an extraction solvent to obtain an extraction mixture. A first separation unit is used to receive the extraction mixture from the first extraction unit and perform separation to obtain an iodine-containing extract and plastic debris of the waste polarizer. The second extraction unit is used to receive the plastic debris of the waste polarizer from the first separation unit and perform re-extraction to obtain a re-extraction mixture. The second separation unit is used to receive the re-extraction mixture from the second extraction unit and perform separation to obtain the re-extraction liquid and the plastic debris of the waste polarizer. The purification concentration system includes a plurality of serially connected filtration units, membrane separation units, and distillation concentration units. The filtration unit is used to receive the iodine-containing extract and filter out the jelly-like material to obtain an iodine-containing filtrate. The membrane separation unit includes at least one reverse osmosis membrane and is used to receive the iodine-containing filtrate and perform reverse osmosis to separate it into an iodine reverse osmosis solution and a osmotic solvent. The distillation concentration unit is used to receive and distill the iodine reverse osmosis solution to obtain an iodine concentrate and a distilled solution. The re-extraction solvent in the second extraction unit includes the permeation solvent and the distillate.

The waste polarizing plate recovery method of the present invention involves mixing plastic fragments of waste polarizing plates containing iodine with an extraction solvent, stirring the mixture to obtain an extraction mixture, and then separating the extraction mixture to obtain an iodine-containing extract. and separating waste polarizers into plastic pieces. and filtering the iodine-containing extract to remove jelly-like substances to obtain an iodine-containing filtrate, and then treating the iodine-containing filtrate using a membrane separation unit including at least one reverse osmosis membrane. Separates into iodine reverse osmosis solution and osmosis solvent. Thereafter, the iodine reverse osmosis solution obtained from the membrane separation unit is distilled to obtain an iodine concentrate and a distilled solution. After recovering the permeation solvent and the distillate to create the re-extraction solvent or the extraction solvent, the re-extraction solution and Separate the waste polarizer into plastic pieces. The resulting re-extraction liquid is recovered and used to create the extraction solvent.

As described above, in the recovery of waste polarizing plates of the present invention, the first extraction unit and the first separation unit not only extract the iodine-containing extract, but also install a purification and concentration system to collect the iodine-containing extract after extraction. The extract is subjected to steps such as filtration and membrane separation to gradually increase the iodine concentration of the iodine-containing extract, thereby increasing the recovery efficiency and lowering the recovery cost. In addition, the second extraction unit and the second separation unit can recover all trace amounts of iodine by re-extracting the plastic fragments from the waste polarizing plate that the first separation unit has separated. The fragments contain little iodine, which is advantageous for subsequent recovery. In addition, since the re-extracted liquid contains only a trace amount of iodine, it can be directly recovered as a raw material for the next extraction solvent, and both the permeation solvent and distilled liquid from the membrane separation and distillation stages mentioned above are recovered. can be reused, saving material costs, preventing cross-contamination, and achieving energy savings and carbon reduction goals.

In order to make the above features of the present invention more understandable, some embodiments will be described below in conjunction with the drawings.

The accompanying drawings are included to provide a further understanding of the principles of the invention, and are incorporated into and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

FIG. 1 is a block diagram of a waste polarizing plate recovery system according to a first embodiment of the present invention. FIG. 7 is a step diagram of a waste polarizing plate recovery flow according to a second embodiment of the present invention. FIG. 3 is a graph of KI concentration vs. conductivity curve prepared using a calibration solution. It is an absorption spectrum diagram obtained by performing UV absorption measurement on a plastic solution before and after removing iodine.

Although the accompanying drawings in the following embodiments are intended to more fully illustrate embodiments of the invention, the invention may be implemented using many different forms and may be implemented in a manner similar to that described. It is not limited to the embodiment. Furthermore, terms such as "including," "containing," and "having" used in the text are open terms. In other words, it includes, but is not limited to.

FIG. 1 is a block diagram of a waste polarizing plate recovery system according to a first embodiment of the present invention.

Referring to FIG. 1, the waste polarizing plate recovery system 100 of this embodiment basically includes a first extraction unit 110, a first separation unit 112, a second extraction unit 114, a second separation unit 116, and a purification and concentration system 120. The first extraction unit 110 is used to receive the waste polarizing plate fragments WP containing iodine and an extraction solvent, and the extraction solvent may include alkalis and a solvent, and the extraction solvent may be first prepared in a solvent preparation unit (not shown) and then put into the first extraction unit 110, or the extraction solvent raw materials prepared based on the respective ratios may be added into the first extraction unit 110 to prepare the extraction solvent. In the first extraction unit 110, the above-mentioned extraction solvent and the waste polarizing plate fragments WP containing iodine are used to perform extraction to obtain an extraction mixture. The first extraction unit 110 may include a stirring element and a heating element. The alkalis in the extraction solvent may be selected from sodium hydroxide, potassium hydroxide, or alkaloids, and the solvent in the extraction solvent may include alcohols. In one embodiment, the solvent is, for example, an ethanol solution, but the present invention is not limited thereto. The above-mentioned extraction solvent may adopt an existing extraction solvent. In one embodiment, when the extraction solvent contains potassium hydroxide, a potassium iodide (KI) solution is obtained by a chemical reaction. The first separation unit 112 is installed between the first extraction unit 110 and the purification and concentration system 120, and is used to receive the extraction mixture from the first extraction unit 110 and perform separation to obtain an iodine-containing extract and plastic fragments of the waste polarizing plate. The iodine-containing extract is conveyed to the purification and concentration system 120, and the plastic fragments of the waste polarizing plate are conveyed to the second extraction unit 114. The first separation unit 112 may include a filter or a centrifugal separator, but the present invention is not limited thereto. The first separation unit 112 may adopt other solid-liquid separation equipment. The above-mentioned second extraction unit 114 is used to re-extract the plastic fragments of the waste polarizing plate and obtain a re-extracted mixture after being installed in the first separation unit 112. In one embodiment, the re-extraction solvent used by the second extraction unit 114 may be an ethanol solution with a concentration similar to that of the extraction solvent described above. In another embodiment, the re-extraction solvent may include an alkali and a solvent, where the alkali is sodium hydroxide, potassium hydroxide, or an alkaloid, and the solvent may include ethanol.

By directly connecting the purification and concentration system 120 and the first separation unit 112, the extracted iodine-containing extract can be directly input to the purification and concentration system 120, but the present invention is not limited thereto. In another embodiment, a temporary storage tank (not shown) may be installed between the first separation unit 112 and the purification and concentration system 120 to temporarily store the iodine-containing extract. The purification and concentration system 120 includes a filtration unit 122, a membrane separation unit 124, and a distillation concentration unit 126 connected in series. Although only one filtration unit 122, one membrane separation unit 124, and one distillation concentration unit 126 are illustrated in FIG. 1, the quantity of these units can be increased as needed, e.g. Before the unit 122, coarse filtration may be performed first, and the filtration unit 122 may be a filter using different filter membranes, such as an ultra-filtration (UF) membrane, a nano-filtration (NF) membrane, etc. , or the UF membrane and the NF membrane connected in series can be used. Taking an ultrafiltration (UF) membrane as an example, a filter membrane with a pore size of 0.02 μm or less can be used. The filtration unit 122 is used to receive the above-mentioned iodine-containing extract and filter out the jelly-like substance to obtain an iodine-containing filtrate. The filtered filtrate is conveyed to the membrane separation unit 124, and the jelly-like material, which may include PVA and an adhesive (such as a hydrogel or UV adhesive), is discharged together and then separated from the PVA and solid waste. Things can be recovered again.

Continuing to refer to FIG. 1, the membrane separation unit 124 includes at least one reverse osmosis membrane and is used to receive and reverse osmose an iodine-containing filtrate to separate it into an iodine reverse osmosis solution and a osmotic solvent. The number of reverse osmosis membranes in the membrane separation unit 124 can be increased as needed. For example, two types of reverse osmosis membranes may be used to concentrate the filtrate. In one embodiment, the total dissolved solids (TDS) filtration rate of the reverse osmosis membrane may be greater than 90%. In other words, most of the solvent contained in the iodine-containing filtrate can be permeated and separated through the membrane separation unit 124, and can also be transmitted to the first extraction unit 110 or the second extraction unit 114 through the pipe for extraction. A solvent or re-extraction solvent can be created. Further, after the distillation concentration unit 126 receives the iodine reverse osmosis liquid from the membrane separation unit 124, it performs distillation to obtain an iodine concentrated liquid and a distilled liquid. The distillation concentration unit 126 is, for example, a room temperature distillation concentration unit or a vacuum distillation concentration unit. Before the distillation concentration unit 126 carries out the distillation, most of the penetrating solvent in the iodine-containing filtrate has already been removed by the membrane separation unit 124, which greatly reduces the energy consumption required for the distillation concentration process and reduces the recovery cost. Since it can significantly reduce the amount of waste, it can be applied to industrial processing where a large amount of recovery is required.

The distillate collected by the distillation concentrator unit 126 is transmitted to a collection tank (not shown) through a pipe and used to make the extraction solvent or re-extraction solvent, thus saving the cost of materials and It can prevent secondary pollution and achieve the goals of energy saving and carbon dioxide reduction. Based on the system design described above, solvent recovery rates of 90% or more can be achieved. To explain in detail, the permeate solvent discharged from the membrane separation unit 124 and the distillate discharged from the distillation concentration unit 126 are collected into the conveyance path of the second extraction unit 114, and a collection tank (not shown) is further installed. Alternatively, the concentration may be adjusted first based on the concentration of the re-extraction solvent required for the second extraction unit 114, and then the re-extraction solvent may be sent from the recovery tank to the second extraction unit 114. In addition, the second extraction unit 114 is mainly used to re-extract the plastic fragments of the waste polarizing plate separated by the first separation unit 112 , and the plastic fragments of these waste polarizing plates include the unextracted plastic fragments. Since the re-extracted mixture received from the second extraction unit 114 may contain trace amounts of iodine, the re-extraction mixture received from the second extraction unit 114 is placed in a second separation unit 116 to remove the plastic debris of the waste polarizer and the solvent, as well as trace amounts of iodine. It can be separated into a re-extracted liquid. The re-extracted liquid containing the solvent and a trace amount of iodine can be recovered to create an extraction solvent and used to enter the first extraction unit 110 again. The above-mentioned plastic fragments of waste polarizing plates include plastics present in common polarizing plates such as TAC (triacetyl cellulose), PMMA (polymethyl methacrylate resin), COP (cycloolefin polymer), and PET (polyethylene terephthalate). Since the iodine content is <0.1% w/w, it can be directly incinerated or separated and then reused. The second separation unit 116 may include a filter or centrifugation equipment. Since the alkali concentration and iodine equivalent of the extraction solvent in the first extraction unit 110 are related to each other, in order to be able to maintain the alkali concentration within a preset range, the alkali concentration and the iodine equivalent of the extraction solvent in the first extraction unit 110 are discharged from the second separation unit 116. A temporary storage tank 118 may also be installed with the re-extraction liquid in the conveying path of the first extraction unit 110, so that water replenishment or pH value adjustment can be carried out immediately.

FIG. 2 is a step diagram of the waste polarizing plate collection flow according to the second embodiment of the invention, and since the collection system of the first embodiment can be adopted, the same unit will be described below with the configuration of FIG. 1. Display using element code.

In step 200, the fragments WP of the waste polarizing plate containing iodine and the extraction solvent are mixed and stirred to obtain an extraction mixture. The extraction solvent can include alkalis and solvents, the alkalis are, for example, sodium hydroxide, potassium hydroxide, or alkaloids, and the solvents can be alcohols, and are environmentally friendly. From this point of view, the solvent may be an ethanol solution.

In step 202, the above-mentioned extraction mixture is separated into an iodine-containing extract and plastic debris of the waste polarizer. Methods for separating the mixture are, for example, filtration or centrifugation.

In step 204, the plastic debris of the waste polarizer described above is re-extracted. The re-extraction solvent used may be an aqueous alcohol solution having a concentration close to that of the extraction solvent. Further, when the re-extraction mixture obtained in step 204 is further separated into a re-extraction liquid, it may be collected and used to create the extraction solvent in step 200, as shown in the direction of the dotted line. To give an example, the above-mentioned re-extraction mixture can be separated into a re-extracted liquid containing the plastic debris of the waste polarizing plate and the solvent and a trace amount of iodine by the method of filtration or centrifugation. The re-extraction solution containing iodine can be used as a raw material for the extraction solvent in step 200. The plastic debris of the waste polarizer described above may include plastics present in common polarizers such as TAC, PMMA, COP, PET, etc.

In step 206, the above-mentioned iodine-containing extract is filtered to remove the jelly-like material and obtain an iodine-containing filtrate. A method for filtering the iodine-containing extract is, for example, a method using an ultrafiltration (UF) membrane, a nanofiltration (NF) membrane, or a series connection of the UF membrane and the NF membrane. If the plastic debris WP of the waste polarizing plate containing iodine contains an adhesive or molecules with a high molecular weight, it can be filtered using a UF membrane, and the plastic debris WP of the waste polarizing plate containing iodine can be filtered using a UF membrane. When containing adhesives or molecules with low molecular weight, a UF membrane and a NF membrane may be connected in series, or an NF membrane may be used for filtration.

In step 208, the membrane separation unit 124 is used to process the iodine-containing filtrate and separate it into an iodine reverse osmosis solution and a osmotic solvent. The membrane separation unit 124 includes one or more reverse osmosis membranes, and the filtration rate of the reverse osmosis membranes is, for example, greater than 90%. The penetrating solvent separated in the process of processing the filtrate using the membrane separation unit 124 is recovered and, in step 204, the plastic fragments of the waste polarizer are re-extracted to create a re-extraction solvent, as shown in the direction of the broken line. It's okay. In another embodiment, the permeation solvent described above may be recovered to create the extraction solvent used in step 200.

In step 210, the iodine reverse osmosis solution obtained from the membrane separation unit 124 is distilled to obtain an iodine concentrate and a distilled solution. The iodine concentrate having a solids content of about 3-10% w/w recovered in accordance with the above steps may be incorporated into an iodine liquid recovery system already present in the polarizer equipment or purified to an industrial level. It may be made into a high-purity potassium iodide solid and reused as a raw material for polarizing plates. In this embodiment, the distilled liquid distilled in step 210 may be further collected as shown in the dashed line direction, and in step 204, a re-extraction solvent may be created by re-extracting the plastic fragments of the waste polarizing plate. In another embodiment, the distillate described above may be recovered to create the extraction solvent used in step 200.

Hereinafter, the effects of the present invention will be verified by enumerating experiments, but the present invention is not limited to the following contents.

<Analysis>

1. Concentration of potassium iodide (KI) in solution Test equipment: Conductivity meter, model number HTC-202U
Test environment: room temperature Calibration solution: KI concentration 0.01% w/w to 8% w/w, pH = up to 9.5

FIG. 3 is a plot of KI concentration versus conductivity prepared using a calibration solution. Therefore, by using the conductivity meter, the KI concentration in the solution can be detected online, and there is no need to extract the solution off line for further detection, making it suitable for use in industrial production. Can be done.

2. Quantitative measurement method for deiodination rate

A plastic solution containing no iodine (setting the deiodination rate to 99%) and a plastic solution without deiodination (setting the deiodination rate to 0%), respectively, using an ultraviolet-visible light spectrometer. UV absorption measurement was performed on the sample, and the iodine content was determined based on the absorption value at 225 nm. As shown in FIG. 4, the UV absorbance corresponding to a deiodination rate of 0% was 2.5, and the UV absorbance corresponding to a deiodination rate of 99% was 0.6. .

Therefore, based on the results in Figure 4, the following linear regression formula is obtained:

(Number 1)
Deiodination rate = -0.5211x + 1.3026

In the above formula, x represents UV absorbance.

<Example 1>

One waste polarizing plate recovery system shown in Figure 1 was prepared. The first extraction unit 110 was a 100 L double jacket stirred tank, and 53.52 kg of a 2% w/w aqueous potassium hydroxide (KOH) solution was added thereto and heated to 50°C. Thereafter, the waste polarizing plate containing 6.66 kg of iodine is crushed into 2-5 mm pieces and transported to the first extraction unit 110 until the pH reaches 9-10 and stops changing, that is, at the end point of the reaction. Extraction was carried out until the Subsequently, the extracted mixture was separated into plastic fragments of the waste polarizing plate and an iodine-containing extract using a centrifuge (used as the first separation unit 112).

Thereafter, the iodine-containing extract is first passed through a primary filter (1 μm, PALL, pressure 1 kg/cm ² ) in the filtration unit 112 and then filtered using the UF membrane listed in Table 1 below to form a jelly. The iodine-containing filtrate was obtained by removing the like substance. Subsequently, the iodine-containing filtrate was introduced into the membrane separation unit 124, and the KI was concentrated using the two-stage reverse osmosis (RO) membrane (RO1 and RO2) listed in Table 1. The first stage RO1 increases the KI concentration from 0.5% w/w to 0.7% w/w, and the second stage RO2 increases the KI concentration from 2.0% w/w to 3.0%. I raised it to w/w. The concentration of KI here can be obtained using the analysis method described above. After that, the reverse osmosis KI solution was put into the distillation concentration unit 126 (30L rotary concentrator, 40°C to 50°C, vacuum degree 10mmHg) again, and distilled until the solid content was 6% w/w KI aqueous solution. . Approximately 50 kg of the ethanol solution removed by the membrane separation unit 124 and the distillation concentration unit 126 is stored in a recovery tank and becomes a re-extraction solvent by adjusting the solvent ratio, so it can be recovered and used in the second extraction unit 114. Can be done.

The plastic fragments of the waste polarizing plate separated by the centrifuge were placed in the second extraction unit 114 (100 L stirring tank), 50 kg of re-extraction solvent was added, and the mixture was stirred at room temperature for 1 hour. The re-extracted liquid was separated in the second separation unit 116 into a liquid containing washed plastic (KI<0.1% w/w), a solvent, and a trace amount of iodine. The deiodination rate of the plastic after washing can be estimated using the above-mentioned method for quantitatively measuring the deiodination rate. The UV absorbance was 0.70, and the deiodination rate was about 93.8%.

<Example 2>

The same collection system as in Example 1 is adopted, but the waste polarizing plate to be collected uses a simple polarizer (no adhesive layer, protective layer, etc.) instead, and the UF film is also different. For details, please refer to Table 1 below.

Using the same recovery method as in Example 1, the washed plastic was irradiated with UV. The obtained UV absorption was 0.73, and the estimated deiodination rate was about 92.1%.

As can be seen from Table 1, the waste polarizing plate recovery system of the present invention can efficiently remove iodine contained in waste polarizing plates.

As described above, the waste polarizing plate recovery system of the present invention has a purification and concentration system equipped with a filtration unit and a membrane separation unit, and can first filter and concentrate the iodine-containing extract after extraction. This reduces the energy consumption of the concentration process, thereby lowering recovery costs. In addition, the combined recovery system of permeating solvent, distillate, and re-extracting liquid can further save material costs, prevent cross-contamination, and achieve energy saving and carbon reduction goals.

As described above, this invention has been disclosed by way of embodiments, but this is not intended to limit this invention, and as can be easily understood by those skilled in the art, appropriate modifications can be made within the scope of the technical idea of this invention. Since significant changes and modifications may naturally be made, the scope of patent protection must be determined based on the scope of the claims and areas equivalent thereto.

The waste polarizer recovery system of the present invention can be applied to the waste treatment industry for polarizers in devices such as liquid crystal displays (LCDs).

100 Waste polarizing plate recovery system 110 First extraction unit 112 First separation unit 114 Second extraction unit 116 Second separation unit 118 Temporary storage tank 120 Purification concentration unit 122 Filtration unit 124 Membrane separation unit 126 Distillation concentration unit 200, 202, 204 , 206, 208, 210 Step WP Fragment of waste polarizing plate containing iodine

Claims (4)

a first extraction unit for obtaining an extraction mixture from fragments of waste polarizers containing iodine using an extraction solvent;
a first separation unit receiving the extraction mixture from the first extraction unit and performing separation to obtain an iodine-containing extract and plastic debris of the waste polarizer;
a second extraction unit that receives the plastic debris of the waste polarizer from the first separation unit and performs re-extraction to obtain a re-extraction mixture;
a second separation unit that receives the re-extraction mixture from the second extraction unit and performs separation to obtain a re-extraction liquid and plastic debris of the waste polarizer ;
a purification concentration system including a plurality of serially connected filtration units, membrane separation units, and distillation concentration units;
, the filtration unit is used to receive the iodine-containing extract and filter out the jelly-like material to obtain an iodine-containing filtrate;
the membrane separation unit includes at least one reverse osmosis membrane and is used to receive and reverse osmose the iodine-containing filtrate to separate it into an iodine reverse osmosis liquid and an osmotic solvent;
the distillation concentration unit is used to receive and distill the iodine reverse osmosis liquid to obtain an iodine concentrate and a distillate;
the re-extraction solvent in the second extraction unit includes the infiltration solvent and the distillate;
A waste polarizer recovery system in which the re -extraction liquid separated from the re-extraction mixture is recovered and used to create the extraction solvent. The waste polarizing plate recovery system according to claim 1, wherein the filtration unit includes an ultrafiltration (UF) membrane, a nanofiltration (NF) membrane, or a series connection of the UF membrane and the NF membrane. The waste polarizing plate recovery system of claim 1, wherein the total dissolved solids (TDS) filtration rate of the at least one reverse osmosis membrane is greater than 90%. 1. The extraction solvent and the re-extraction solvent each independently contain an alkali and a solvent, the alkali contains sodium hydroxide, potassium hydroxide, or an alkaloid, and the solvent contains ethanol. The waste polarizing plate collection system described in .