A purification device for ultra-high purity polyethylene

Abstract

This utility model relates to an ultra-high purity polyethylene purification device. The device includes a carbon dioxide storage unit, a mixing unit, a washing unit, a vacuum separation unit, and a refrigeration unit connected in sequence. The mixing unit is also connected to an entrainer storage unit. The outlet of the refrigeration unit is connected to the carbon dioxide storage unit to form a circulation loop. The entrainer storage unit includes tanks for acidic solutions, alcohol solvents, chelating agents, surfactants, etc. This device utilizes supercritical carbon dioxide fluid in conjunction with an entrainer to deeply clean polyethylene powder, effectively removing organic residues and metallic impurities. The carbon dioxide is recyclable, with a high recovery rate and high purification efficiency, making it suitable for ultra-high purity polyethylene production.

Description

Technical Field

[0001] This utility model relates to the field of ultra-high purity polymer production technology, specifically to an ultra-high purity polyethylene purification device. Background Technology

[0002] The application of high-end polyolefin materials, represented by ultra-high purity polyethylene (UHPE), is increasingly prominent in cutting-edge fields such as semiconductor manufacturing and biomedicine. In the semiconductor industry, UHPE can be used as a core membrane material in ultrapure water preparation devices, but it must meet the stringent requirement of ASTM D4326 standard, which stipulates that the total content of 12 metallic impurities, including sodium (Na), iron (Fe), and chromium (Cr), must be below 50 ppb. In the medical field, as an implant material, it must comply with the ISO 5835 standard. Furthermore, in semiconductor process auxiliary materials such as photoresist carriers, it must also meet the extreme control requirements for metal ion content in industry standards such as SEMI F57. Current polyethylene production processes still have significant limitations in preparing UHPE, making it difficult to achieve the ultra-low levels of metallic and other impurities required for high-end applications. While existing purification technologies such as solvent washing and devolatilization can reduce impurity content to some extent, they still cannot achieve deep, stable, and economically feasible purification effects, thus restricting the production of UHPE. Therefore, developing production equipment with deep purification capabilities is crucial to overcoming these barriers. Utility Model Content

[0003] The purpose of this invention is to provide an ultra-high purity polyethylene purification device to solve the above-mentioned problems, for producing ultra-clean, high-purity polyethylene.

[0004] The objective of this utility model is achieved through the following technical solution:

[0005] An ultra-high purity polyethylene purification device, comprising:

[0006] A carbon dioxide storage unit for providing liquid carbon dioxide;

[0007] Entrainer storage unit, used to store entrainer;

[0008] A mixing unit, the inlet of which is connected to the carbon dioxide storage unit and the entrainer storage unit respectively, is used to mix liquid carbon dioxide with the entrainer;

[0009] The washing unit, whose inlet is connected to the outlet of the mixing unit, is used to wash polyethylene powder under supercritical carbon dioxide conditions.

[0010] The pressure reduction and separation unit has its inlet end connected to the outlet end of the washing unit, and is used to reduce pressure and separate impurities from the fluid filtered after washing.

[0011] A refrigeration unit is located between the pressure reduction and separation unit and the carbon dioxide storage unit, and is used to condense and liquefy carbon dioxide gas for recovery.

[0012] As a preferred embodiment of the present invention, the entrainer storage unit includes an acidic solution storage tank, an alcohol solvent storage tank, and a chelating agent storage tank.

[0013] As a preferred embodiment of the present invention, the entrainer storage unit further includes a surfactant storage tank.

[0014] As a preferred embodiment of the present invention, the pressure reduction separation unit includes a pressure reduction separation unit I and a pressure reduction separation unit II arranged in series.

[0015] As a preferred embodiment of the present invention, a purification unit is further provided at the inlet front end of the refrigeration unit.

[0016] As a preferred technical solution of the present invention, the purification unit is a deashing contact tower or an activated carbon adsorption tower.

[0017] As a preferred technical solution of the present invention, the washing unit is a pressure-resistant mixing tank with a temperature-controlled heat exchange jacket and a stirring mechanism.

[0018] As a preferred technical solution of the present invention, multiple washing units are provided, and the multiple washing units are connected in parallel or in series in the device.

[0019] As a preferred technical solution of the present invention, the connecting pipeline of the device is equipped with a control valve and a high-pressure metering pump.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] This device uses supercritical carbon dioxide fluid as the cleaning medium, combining the high permeability of gas with the strong dissolving power of liquid to efficiently remove organic residues and oligomers from polyethylene powder. By introducing entrainers such as acidic solutions, alcohol solvents, chelating agents, and surfactants, the device enhances its ability to remove ionic and metallic impurities, achieving deep purification of polyethylene. The entire device integrates cleaning and drying, boasts high carbon dioxide recovery and recycling rates, and is energy-saving and environmentally friendly, meeting the production requirements of ultra-high purity polyethylene for electronic and medical grades. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of an ultra-high purity polyethylene purification device according to an embodiment;

[0023] In the diagram: 100 - Carbon dioxide storage unit; 200 - Entrainer storage unit; 201 - Acidic solution storage tank; 202 - Alcohol solvent storage tank; 203 - Chelating agent storage tank; 204 - Surfactant storage tank; 300 - Mixing unit; 400 - Washing unit; 500 - Vacuum separation unit; 501 - Vacuum separation unit I; 502 - Vacuum separation unit II; 600 - Refrigeration unit; 700 - Purification unit. Detailed Implementation

[0024] The present invention will now be described in detail. Any content not described in detail herein is known in the art.

[0025] Reference Figure 1 A purification device for ultra-high purity polyethylene is disclosed, based on a supercritical carbon dioxide cleaning purification process. The device includes a carbon dioxide storage unit 100, an entrainer storage unit 200, a mixing unit 300, a washing unit 400, a vacuum separation unit 500, and a refrigeration unit 600. The entire device integrates supercritical cleaning and drying. Multiple washing units 400 can be provided as needed, and can be arranged in parallel or series.

[0026] In a preferred embodiment, the carbon dioxide storage unit 100 stores high-purity liquid carbon dioxide (e.g., a liquid carbon dioxide storage tank) as a solvent medium for washing polyethylene. The entrainer storage unit 200 includes an acidic solution storage tank 201, an alcohol solvent storage tank 202, and a chelating agent storage tank 203. The acidic solution storage tank 201 stores inorganic acids (such as dilute nitric acid, hydrochloric acid, or dilute sulfuric acid, prepared from ultrapure water) or organic acids (such as oxalic acid, citric acid, formic acid, tartaric acid, or their ultrapure aqueous solutions); the alcohol solvent storage tank 202 stores alcohol solvents, including isopropanol, ethanol, methanol, n-propanol, n-butanol, etc., preferably anhydrous ethanol; the chelating agent storage tank 203 stores chelating agents soluble in supercritical carbon dioxide, such as hexafluoroacetylacetone, trifluoroacetylacetone, pentafluoropropionylacetone, etc.

[0027] As a further preferred technical solution, the entrainer storage unit 200 also includes a surfactant storage tank 204, which stores CO2-affinity surfactants, such as fluorocarbon chain surfactants (e.g., perfluorooctyl sulfonate), perfluorocarboxylic acid and its salt surfactants (e.g., ammonium perfluorooctanoate, sodium perfluorohexanoate), perfluorosulfonate surfactants (e.g., potassium perfluorobutyrate, sodium perfluorohexanesulfonate), perfluoroalkyl quaternary ammonium salt surfactants (e.g., perfluorohexyltrimethylammonium chloride), and perfluoropolyether surfactants (e.g., ... BH-50V).

[0028] Both the carbon dioxide storage unit 100 and the entrainer storage unit 200 are connected to the mixing unit 300. The mixing unit 300 is preferably a pressure-resistant stirred mixing tank. The outlet pipeline of the carbon dioxide storage unit 100 is equipped with a control valve and a high-pressure metering pump to precisely control the injection of liquid carbon dioxide. Each storage tank in the entrainer storage unit 200 is connected to the mixing unit 300 via a feeding pipeline: liquid entrainer is added via a high-pressure metering pump, and solid entrainer can be added via intermittent feeding or a rotary valve feeder. The uniformly mixed liquid carbon dioxide containing entrainer is sent to the washing unit 400 to treat the polyethylene powder contained therein.

[0029] The washing unit 400 is a pressure-resistant mixing tank with a stirrer and a temperature-controlled heat exchange jacket, enabling precise temperature control. After the polyethylene powder to be purified is loaded into the washing unit 400, liquid carbon dioxide containing an entrainer is injected. The temperature and pressure are adjusted to bring the carbon dioxide to a supercritical state, thus washing the polyethylene. The washing time can be 0.1–10 hours, preferably 0.5–8 hours, and more preferably 1–4 hours.

[0030] Downstream of the washing unit 400 is a pressure-reducing separation unit 500, which includes pressure-reducing separation units I 501 and II 502 connected in series to achieve complete separation of impurities and carbon dioxide, preventing contaminants from being re-introduced into the system during circulation and ensuring unobstructed pipeline flow. After washing, carbon dioxide containing impurities is discharged from the bottom of the washing unit 400, while solid polyethylene remains in the tank. Subsequently, the residual liquid carbon dioxide in the tank is discharged, the pressure is released, and the temperature is increased to remove residual carbon dioxide, achieving material drying and ultimately collecting ultra-high purity polyethylene product. Gaseous carbon dioxide is recovered and reused, condensed by the refrigeration unit 600, and collected in the carbon dioxide storage unit 100 for recycling.

[0031] Carbon dioxide discharged from the bottom of the washing unit 400 enters the pressure-reducing separation unit 500 for pressure reduction and impurity separation. Adjusting the pressure values ​​of pressure-reducing separation units I and II significantly reduces the solubility of impurities due to the decreased CO2 pressure, achieving effective separation of CO2 and impurities. The separated impurities are discharged from the bottom, while the separated CO2 gas is discharged from the top and condensed into liquid CO2 by the refrigeration unit 600 (e.g., a condenser). This liquid CO2 is then stored in the carbon dioxide storage unit 100 for recycling, avoiding CO2 waste. The CO2 recycling rate can reach over 99%. In a preferred embodiment, a purification unit 700 (e.g., using a de-ashing contact tower, activated carbon adsorption tower, or other clean equipment) is installed before the refrigeration unit 600. This purification process removes various impurities before the gaseous carbon dioxide enters the refrigeration unit 600, ensuring the purity of the recycled carbon dioxide and meeting the purification requirements for producing ultra-clean high-purity polyethylene.

[0032] This device utilizes supercritical carbon dioxide containing an entrainer to purify polyethylene powder. Supercritical carbon dioxide combines the characteristics of high gas diffusivity and high liquid solubility, exhibiting low viscosity and good mass transfer performance, effectively removing organic residues and oligomers from polyethylene. Its near-zero surface tension and low supercritical temperature allow it to penetrate deep into the powder for cleaning without damaging the material. Carbon dioxide itself is non-toxic, non-flammable, chemically stable, and easily recyclable. No additional drying is required after cleaning, offering both economic and environmental advantages.

[0033] Because carbon dioxide is highly nonpolar, its solubility for ionic impurities and some metallic impurities is limited. This device incorporates an entrainer storage unit 200, including an acidic solution storage tank 201, an alcohol solvent storage tank 202, a chelating agent storage tank 203, and / or a surfactant storage tank 204. The acidic solution, alcohol solvent, and chelating agent are added along with the carbon dioxide as entrainers. During the washing process, the acidic solution reacts with residual alkaline impurities and metal oxides, decomposing metal compounds and releasing metal ions. These metal ions further react with the chelating agent to form chelates soluble in supercritical CO2. Supercritical CO2 has a swelling effect on polyethylene powder, allowing it to diffuse into the interior of the polyethylene powder and fully release the aforementioned impurities, thus facilitating deep purification. Alcohol solvents can hydrolyze metal residues (such as TiCl4, AlRXCl3-x) into metal hydroxides and volatile components, causing the catalyst residue to expand and loosen, enhancing the permeability of supercritical CO2 to the pores. In this process, impurities, including metals, that are not originally soluble in supercritical CO2 are converted into soluble components and separated from polyethylene powder with supercritical CO2, thus achieving deep purification of polyethylene.

[0034] As a preferred embodiment, the entrainer can be added all at once or in stages. For example, the entrainer can be added all at once with CO2 to wash the polyethylene; as a preferred embodiment, the entrainer can be added step by step with CO2 in the following steps: (1) first, an acidic solution and an alcohol solvent are added to wash for a period of time, and the supercritical CO2 containing the acidic solution and alcohol solvent is used to acid wash the polyethylene powder to dissolve alkaline impurities and metal oxides; (2) then a chelating agent is added to capture free metal ions and form chelates that can be dissolved in supercritical CO2, and a surfactant is further added. Stepwise washing can better utilize the role of the entrainer and achieve deep and efficient purification. By adding supercritical CO2 containing acid and alcohol to dissolve alkaline impurities and oxides; in the chelation stage, supercritical CO2 containing chelating agent and alcohol is added to capture free metal ions, and finally supercritical CO2 containing surfactant is used for deep cleaning, which can meet the needs of deep purification scenarios with extremely high purity requirements (such as electronic grade and medical grade).

[0035] The above description of the embodiments is provided to enable those skilled in the art to understand and use the utility model. It will be apparent to those skilled in the art that various modifications can be easily made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present utility model is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present utility model without departing from its scope should be within the protection scope of the present utility model.

Claims

1. An ultra-high purity polyethylene purification apparatus, characterized by, include: A carbon dioxide storage unit (100) is used to provide liquid carbon dioxide; Entrainer storage unit (200) for storing entrainer; A mixing unit (300) is connected at its inlet to the carbon dioxide storage unit (100) and the entrainer storage unit (200) respectively, for mixing liquid carbon dioxide with an entrainer; The washing unit (400) is connected at its inlet to the outlet of the mixing unit (300) and is used to wash polyethylene powder under supercritical carbon dioxide conditions. The pressure reduction separation unit (500) has its inlet end connected to the outlet end of the washing unit (400) and is used to reduce pressure and separate impurities from the filtered fluid after washing. A refrigeration unit (600) is located between the pressure reduction and separation unit (500) and the carbon dioxide storage unit (100) for condensing and liquefying carbon dioxide gas for recovery.

2. The ultra-high purity polyethylene purification device according to claim 1, characterized in that, The entrainer storage unit (200) includes an acidic solution storage tank (201), an alcohol solvent storage tank (202), and a chelating agent storage tank (203).

3. The ultra-high purity polyethylene purification device according to claim 2, characterized in that, The entrainer storage unit (200) also includes a surfactant storage tank (204).

4. The ultra-high purity polyethylene purification device according to claim 1, characterized in that, The pressure reduction separation unit (500) includes pressure reduction separation unit I (501) and pressure reduction separation unit II (502) arranged in series.

5. The ultra-high purity polyethylene purification device according to claim 1, characterized in that, A purification unit (700) is also provided at the inlet front end of the refrigeration unit (600).

6. The ultra-high purity polyethylene purification apparatus according to claim 5, characterized in that, The purification unit (700) is a deashing contact tower or an activated carbon adsorption tower.

7. The ultra-high purity polyethylene purification device according to claim 1, characterized in that, The washing unit (400) is a pressure-resistant mixing tank with a temperature-controlled heat exchange jacket and a stirring mechanism.

8. The ultra-high purity polyethylene purification device according to claim 1, characterized in that, Multiple washing units (400) are provided, and the multiple washing units (400) are connected in parallel or in series in the device.

9. The ultra-high purity polyethylene purification device according to claim 1, characterized in that, The device is equipped with a control valve and a high-pressure metering pump in its connecting pipeline.

Images