TWI598157B - Polarizer waste disposal methods - Google Patents

Description

Polarizer waste disposal method

The invention relates to a method for treating a waste material of a polarizing plate, in particular to a method for treating a polarized plate waste product which is effective for separating components in a polarizing plate for recycling plastic or embedding treatment.

According to the liquid crystal display, it is widely used in computers, communication, consumer electronics and other applications. The polarizing plate is a key component of the liquid crystal display. Its function is mainly to control the polarization direction of specific light waves, plus the liquid crystal torsional characteristics. In order to achieve control of the passage of light, to form light and dark and to provide the necessary display characteristics, the polarizing plate is of considerable importance to the LCD.

Referring to Fig. 1, the main structure of the polarizing plate 1 comprises a polyethylene terephthalate (PET) protective layer, Pressure Sensitive Adhesive (PSA), and triacetate (Tri- Cellulose Acetate (TAC) consisting of a support layer, a polyvinyl alcohol (PVA) and a release film, the structure of which is the upper support layer 10 (PET/TAC), the polarizing layer 20 (PVA), and the lower support layer 30. (PET/TAC), pressure sensitive adhesive 40 (PSA), and release layer 50 (PET) are formed, and the upper support layer 10 is usually covered with a transparent surface protective layer (PET). At present, the polarizing plate 1 is generally produced by first performing iodine dyeing and then stretching, so that iodine molecules form a directed arrangement on the PVA film, and the polarized light can be controlled by the electric field.

At present, the discarded polarizing plate 1 contains iodine, which causes secondary environmental pollution during burial or incineration, and the plastic materials such as PET and TAC in the polarizing plate 1 have the potential to be reused, especially TAC. The upper support layer 10 and the lower support layer 30 of the material account for more than one-half of the overall cost of the polarizing plate 1. Therefore, as disclosed in the publication No. I462786 "Polarization method for polarizing plate", a immersion of alkaloid at room temperature to remove iodine in the polarizing plate is provided. And the method of recycling plastic, but the reaction consumed by the method The time is quite long, and the organic chemical materials such as alkaloids have volatile characteristics, and it is necessary to continuously monitor and add drugs in the process to maintain the treatment efficiency and quality. Therefore, how to remove the iodine in the waste polarizing plate 1 by a low-cost treatment method for subsequent resource utilization or treatment/disposal is an important research topic at present.

The object of the present invention is to solve the problem that the polarizing plate cannot be effectively processed or recovered in the above prior art.

In order to achieve the above object, the present invention provides a method for processing a polarized plate waste product, comprising the steps of: step S1. providing a polarizing plate waste product, and pulverizing the polarized plate waste product into pieces according to a preset size; and step S2. transporting the pieces to the An alkali washing tank, the alkaline washing tank has an alkaline solution containing sodium hydroxide; step S3. soaking the pieces in the alkaline solution for a predetermined time, and adjusting the alkaline solution to maintain the preset temperature, After the iodine molecules in the fragments are dissolved in the alkaline solution, the preliminary processing of the fragments is carried out; step S4. transferring the preliminary treated chips and the alkaline solution to a dehydrator, and using the dehydrator to treat the preliminary processed fragments and the The alkaline solution is separated, and the preliminary treated chips are washed and dehydrated at least once to obtain a finished product.

Further, the method for processing the polarized plate waste product further includes a step S0 performed before the step S1: determining whether to peel the film according to the waste type of the polarizing plate, and cleaning and dehydrating the polarized plate waste product.

Further, either side of the fragments is 2 to 3 cm long.

Further, the alkaline solution has a sodium hydroxide concentration of 1% to 5%.

Further, the predetermined time for the fragments to be immersed in the alkaline solution is 1 to 6 hours.

Further, the preset temperature of the alkaline solution is 40 to 80 °C.

Further, the liquid-solid ratio of the alkaline solution to the fragments in step S3 is 3 to 10.

Therefore, the present invention has the following beneficial effects over the prior art:

1. The method for treating waste paper of the polarizing plate of the invention can effectively separate the PVA film with iodine molecules in the polarizing plate from PET and TAC, so that the PET and the TAC can be recycled or incinerated and buried, and used for caustic washing. The sodium hydroxide solution can be recycled to the next stage for repeated reaction utilization, and the overall treatment cost is relatively low, and it is not like the organic chemical solution is volatile and difficult to recycle, and the wastewater treatment is difficult and easily pollutes the environment.

1‧‧‧Polar plate

10‧‧‧Upper support layer

20‧‧‧ polarizing layer

30‧‧‧ lower support layer

40‧‧‧pressure adhesive

50‧‧‧ release layer

S0~S4‧‧‧Steps

Figure 1: A schematic plan view of a conventional polarizing plate.

Figure 2 is a flow chart of the method of the present invention.

For a more detailed description of the technical features and operation modes of the present application, and with reference to the illustrations, please refer to the review. In addition, the present invention is not intended to limit the scope of the invention as claimed.

Regarding the technology of the present invention, please refer to FIG. 2, which is a flow chart of the method for processing the polarized plate waste of the present invention. Due to the different material sources of polarized plate waste materials, there may be structural differences, such as defective products such as polarized plates and defective products made by general factories. The structure is TAC/PET protective layer, PVA polarizing layer and TAC/PET protective layer. Five parts, such as PSA pressure sensitive adhesive and PET release layer, but if it is a semi-finished polarized plate, it contains the upper TAC/PET film, PVA and lower TAC/PET film. In order to achieve better work efficiency, step S0 can be performed in advance before starting to process the polarized plate waste product: whether the film is stripped according to the type of the polarized plate waste, and the polarized plate waste product is cleaned and dehydrated. If the polarized plate waste product is a semi-finished product as described above, it can be directly washed and dehydrated. If it is a defective product such as a defective product or a defective product, the PSA pressure sensitive adhesive is removed and then washed and dehydrated. After the above pre-operations, the main steps of the method of the present invention are started:

Step S1: providing a polarized plate waste product, and pulverizing the polarized plate waste product into pieces according to a preset size. In the present invention, the polarized plate waste product is pulverized into pieces of any side length of about 2 to 3 cm, and the longest side thereof is not more than 3 cm. This specification can be smashed by a pulverizer and sieved to avoid oversize. The thickness affects the efficiency of subsequent alkali washing and iodine dissolution.

Step S2: transporting the pieces to an alkali washing tank having an alkaline solution containing sodium hydroxide. In this step, solid caustic soda may be preliminarily placed in the alkali washing tank, and stirred in warm water to make the solution in the alkali washing tank alkaline.

Step S3: soaking the pieces in the alkaline solution for a predetermined time, and adjusting the alkaline solution to maintain a preset temperature, and after the iodine molecules in the pieces are dissolved in the alkaline solution, the preliminary processing of the pieces is left. In this step, the sodium hydroxide concentration of the alkaline solution is preferably 1% to 5%, and the liquid-solid ratio is between 3 and 10, and the predetermined time is 1 to 6 hours, and the preset temperature is 40. ~80 °C range. In the experiment, increasing the reaction temperature helps to dissolve the iodine molecules, but since PVA is a water-soluble polymer obtained by partially or completely hydrolyzing polyvinyl acetate, its performance is between plastic and rubber, and the glass transition temperature is about For 60~85 °C, when the temperature is high, the semi-finished waste polarizer sample in the impregnation solution will become thicker, which will increase the viscosity of the impregnation solution and affect the stirring effect. Therefore, it is recommended that the reaction temperature be 50. In the range of ~70 ° C, especially when it is below 55 ° C, PVA does not exhibit the characteristics of sticking into agglomerate, and it is easier to perform stirring and the like. In one embodiment, steam generated during the hood collection reaction can be provided, trapped and cooled, and then returned to the caustic tank for recycling.

Step S4: transferring the preliminary treatment fragments and the alkaline solution to a dehydrator, separating the preliminary treatment fragments and the alkaline solution by using a dehydrator, and washing the preliminary treatment fragments and dehydrating at least once to obtain the finished product. . In this embodiment, the separated alkaline solution can be recycled to the next alkali washing operation for reuse, or discharged into a wastewater treatment facility for filtration, chemical coagulation, flotation, neutralization, ion exchange, and The activated carbon adsorption operation is not limited herein. Finished product It is a piece of PET or TAC plastic that can be directly incinerated or buried without causing environmental pollution. It can also be melted and recycled as other finished plastic products.

In order to further illustrate the efficacy of this case, please refer to the following specific examples, and discuss the immersion washing and iodine dissolution of the semi-finished waste polarizing plate.

Specific case

Take 400g of the washed semi-finished waste polarizing plate and pulverize it into pieces, then put it into 1600g of 4% sodium hydroxide solution, heat it to 50 ° C and maintain it for 120 minutes, then find the semi-finished waste polarizer fragments. The concentration of iodine in the impregnation solution is 4864mg/l. From the naked eye, it can be seen that the color of the finished product is changed from blue black of the original semi-finished waste polarizing plate to transparent or light brown. It can also be observed by Raman spectroscopy. The characteristic peak of iodine in PVA disappears in the spectrum of Raman number of about 108 and 160 cm ^-1 , so the method of the present invention can achieve the effect of removing iodine molecules in the polarizing plate.

In summary, the present invention utilizes a sodium hydroxide solution to immerse the waste polarizing plate, and the iodine molecules used for dyeing the PVA film in the polarized plate waste product can be perfectly removed, and the treated PET/TAC fragments are not buried or incinerated. After the secondary environmental pollution, the finished product can also be used as recycled plastic in the textile or plastics manufacturing industry.

S0~S4‧‧‧Steps

Claims (2)

A method for treating a waste material of a polarizing plate comprises the following steps: Step S1. Providing a waste material of a polarizing plate, and pulverizing the waste material of the polarizing plate into pieces according to a preset size; Step S2: transporting the pieces to an alkali washing tank, the alkali washing The tank has an alkaline solution containing sodium hydroxide; step S3. soaking the fragments in the alkaline solution for a predetermined time, and adjusting the alkaline solution to maintain a preset temperature, and the iodine molecules in the fragments are dissolved. After the alkaline solution, the preliminary treatment of the fragments is left; and step S4. transferring the preliminary treated chips and the alkaline solution to a dehydrator, separating the preliminary treated chips and the alkaline solution by using a dehydrator, and The preliminary treatment of the debris is washed and then dehydrated at least once to obtain a finished product; wherein the sides of the fragments are 2 to 3 cm long, and the alkaline solution has a sodium hydroxide concentration of 1% to 5%, and the fragments are soaked in the The predetermined time of the alkaline solution is 1 to 6 hours, the preset temperature of the alkaline solution is 40 to 80 ° C, and the liquid-solid ratio of the alkaline solution to the fragments in step S3 is 3 to 10. The method for processing a polarized plate waste product according to claim 1 further includes a step S0 performed before the step S1: determining whether to strip the film according to the waste type of the polarizing plate, and cleaning and dehydrating the polarized plate waste product.