High purity polyethylene and method of making and use thereof

Abstract

The application provides high-purity polyethylene, a preparation method and application thereof, wherein the content of single metal impurities in the polyethylene is less than 1.0 ppm, the content of total metal impurities is less than 3.0 ppm, and the content of total chlorine is less than 2 ppm. The application realizes the preparation of ultra-pure polyethylene to meet the low metal content requirement of polyethylene in the fields of semiconductors, medical treatment, ultra-pure reagent storage and transportation and power battery separators.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, and relates to a high-purity polyethylene, its preparation method, and its application. Background Technology

[0002] Domestically produced polyethylene products remain relatively low-end, and the polyethylene industry currently faces overcapacity pressure. Product quality cannot meet the requirements for applications in semiconductor manufacturing processes, such as wafer carriers, wafer cassettes, pipes, valves, high-end medical device packaging, ultrapure chemical storage and transportation containers, and power battery separators. These fields all require polyethylene to meet high purity and low impurity leaching requirements, and currently, this type of high-performance and high-purity polyethylene still needs to be imported. While deashing of polyolefins can be achieved by increasing the activity of the catalyst in the polymerization process, this method can only reduce the residual catalyst content in the polymer to below 50 ppm. Especially in the semiconductor field, this purity is still insufficient for application requirements. With the development of the semiconductor, medical, ultrapure reagent storage and transportation, and power battery separator fields, higher requirements will inevitably be placed on the metal content of polyethylene in the future. In addition to using efficient catalysts to reduce the residual metal impurities in polyethylene, further reduction of the metal impurity content in polyethylene through post-processing is also necessary.

[0003] Ultrapure polyethylene has a wide range of applications in many high-end industries. In the semiconductor and chip industry, high-purity polyethylene can be used in key components such as photoresists and electronic gas delivery pipelines to ensure the precision and reliability of semiconductor manufacturing processes. In the new energy field, it is also used in lithium battery separators and solar cell encapsulation materials, which are of great significance for improving the performance of new energy products. In the field of ultrapure reagents, polyethylene has excellent chemical stability and can resist the corrosion of many chemical substances. It is used in the preparation of hollow containers to ensure the long-term stability of containers when containing various electronic-grade chemicals, preventing the chemicals from reacting with the container and deteriorating. In the field of medical devices, polyethylene has excellent biocompatibility and stability, and is highly favored in the manufacture of medical devices, especially in some scenarios with extremely high requirements for material cleanliness and biosafety.

[0004] The main factor affecting the purity of polyethylene is metal ions, and many anions coexist with metal ions. The introduction of metal ions into conventional polyethylene mainly occurs during the polyolefin production process. Factors such as catalyst residues, additives, and impurities in reaction equipment and the environment can introduce metal impurities into polyolefins. Excessive ash content in polyolefins leads to a decline in quality, thus limiting their practical applications.

[0005] CN114471471A discloses an adsorbent for removing residual metals from polyolefins, its preparation method, and its application. The method involves preparing a polyolefin solution and passing it through an adsorption column filled with a novel adsorbent. By adjusting the flow rate, temperature, and adsorption time of the solution through the adsorption column, residual metals in the polyolefin can be removed. However, this process is only suitable for polyolefins that easily form polymer solutions and is not applicable to polyolefins produced by non-solution methods or those that are difficult to dissolve, thus lacking broad applicability. Furthermore, the removal effect of metal elements other than aluminum is not significant in this method.

[0006] CN113856637A discloses a method for preparing chelate adsorption packing and its application. The method involves injecting a cyclic olefin polymer reaction solution into a packed column. After the reaction solution flows through the column filled with the novel chelate adsorption packing, a deashed reaction solution is obtained. This deashed reaction solution is then injected into ethanol to obtain a cyclic olefin polymer sample. However, this process is only suitable for removing metal residues from the COC and COP production processes, and its impurity removal effect is poor; the metal residue in the polymer after impurity removal using this process can only reach a level within 100 ppm.

[0007] Solvent washing is a simple and widely applicable process that has attracted increasing attention from researchers. For example, CN115124635A discloses a deashing method for polyolefin materials, which removes metal elements from polyolefins through impregnation elution. The specific impregnation elution process is as follows: polyolefin powder and hydrocarbon solvent are added to a reaction vessel and impregnated or dissolved at a certain temperature for 0.5–3 hours; reagents are added to the impregnated / dissolved solution, and a pretreatment temperature is set; a suitable complexing agent is added to the pretreated solution, and a metal complexation reaction is carried out at an adjusted temperature for 0.5–4 hours; the solution after the complexation reaction is eluted 2–5 times with an eluent, with an optimal elution time of 4–20 hours, finally yielding the deashed polyolefin. However, this process is complex, consumes a large amount of solvent, has low efficiency, and is time-consuming.

[0008] CN 117798121 A discloses a method of adding the polyolefin resin material to be treated and a mixed solvent (hydrocarbon solvent, alcohol solvent and cyclic ether compound solvent) into a reaction vessel in a certain proportion, and performing simple stirring and washing for 0.5 to 4 hours at a temperature of 60 to 150°C and a stirring linear speed of 0.24 to 2.36 m / s. This method can remove the ash content of the raw material (>200 ppm) and, after several washing and deashing processes, reduce the content of aluminum, magnesium, titanium, and iron in the polyolefin resin material to ≤10 ppm; the content of calcium, chromium, zinc, and phosphorus to <5 ppm; and the total ash content in the polyolefin resin material after deashing to <20 ppm.

[0009] Shandong Jingbo Petrochemical Co., Ltd. has conducted extensive research on polypropylene deashing to improve the electrical properties of polypropylene for use in the electrical field. CN 115612005 A discloses a highly efficient solvent deashing method for polypropylene resin. In this method, polypropylene powder is sequentially mixed with a mixture 1 and a mixer 2, requiring 1-5 repetitions to obtain ultra-low ash polypropylene powder. Mixture 1 mainly consists of alkanes and a coordinating agent, while mixture 2 mainly consists of alkanes and alcohols. This invention can reduce the ash content in polypropylene to below 20 ppm, and effectively control the content of magnesium, aluminum, and titanium to 1-3 ppm. While this method can reduce the ash content in polypropylene to below 20 ppm, it requires repeated processing, resulting in high solvent consumption and low efficiency.

[0010] CN 117645680 A discloses a method for reducing the ash content of polypropylene and the application of imidazolium ionic liquid. By mixing polypropylene powder with imidazolium ionic liquid, followed by filtration and washing, a low-ash polypropylene product is obtained. This invention can reduce the ash content in polypropylene to below 10 ppm, with magnesium, aluminum, and titanium content all controlled within 1-3 ppm. Using ionic liquid can further reduce the ash content to below 10 ppm, but ionic liquid is more expensive and less economical, hindering industrial application.

[0011] CN 115124635 B discloses a method for deashing polyolefin materials. The method involves pretreating the polyolefin with an acidic reagent and alkanes, preparing the polyolefin into a solution, adding a complexing agent to the pretreatment mixture to induce a complexation reaction with metallic impurities, and finally using an eluent to wash away the solvent and impurities, ultimately obtaining the deashed polyolefin material. This invention can reduce ash content to below 20 ppm and the content of magnesium, aluminum, and titanium to below 5 ppm. However, the process is relatively cumbersome, requires a large number of reagents, and has a heavy burden of waste liquid treatment, resulting in high investment costs and hindering industrial application.

[0012] CN117798121A discloses a cleaning process and device for removing impurities from polyolefins. The process involves using a mixed solvent (containing 90-99 wt% hydrocarbon solvent, 0.5-5 wt% alcohol solvent, and 0.5-5 wt% cyclic ether compound solvent) to clean polyolefin resin materials multiple times. This invention can control the total ash content in polyolefin resin materials to within 20 ppm, but it is still not suitable for scenarios with extremely high requirements for material cleanliness and biosafety. Summary of the Invention

[0013] To address the shortcomings of existing technologies, the present invention aims to provide a high-purity polyethylene, its preparation method, and its applications. The high-purity polyethylene of this invention has a single metal content of <1 ppm, a total metal content of <3 ppm, and a Cl element content of <2 ppm. This invention achieves the preparation of ultra-pure polyethylene to meet the low metal content requirements of polyethylene in fields such as semiconductors, medical applications, ultra-pure reagent storage and transportation, and power battery separators. Furthermore, this invention is applicable to polyethylene with a molecular weight range of 50,000 g / mol to 2,000,000 g / mol, i.e., solid deashing treatment from low molecular weight polyethylene to ultra-high molecular weight polyethylene, meeting the needs of different fields.

[0014] To achieve this objective, the present invention adopts the following technical solution: On one hand, the present invention provides a high-purity polyethylene, wherein the content of a single metal impurity in the polyethylene is less than 1.0 ppm, the content of total metal impurities is less than 3.0 ppm, and the content of total chlorine is less than 2 ppm.

[0015] In this invention, the content of a single metal impurity in the polyethylene is less than 1.0 ppm, for example, it can be 0 ppm, 0.1 ppm, 0.2 ppm, 0.3 ppm, 0.4 ppm, 0.5 ppm, 0.6 ppm, 0.7 ppm, 0.8 ppm, or 0.9 ppm; the content of total metal impurities is less than 3.0 ppm, for example, 0 ppm, 0.4 ppm, 0.8 ppm, 1.2 ppm, 1.6 ppm, 2 ppm, 2.4 ppm, 2.8 ppm, or 2.9 ppm; the content of total chlorine is less than 2 ppm, for example, 0 ppm, 0.3 ppm, 0.6 ppm, 0.9 ppm, 1.2 ppm, 1.5 ppm, 1.8 ppm, or 1.9 ppm.

[0016] Preferably, the metallic impurities include, but are not limited to, any one or a combination of at least two of Na, Ti, Mg, Al, Ca, Fe, Cr, Zn, Ni, Mn, Co, and Mo.

[0017] Preferably, the weight-average molecular weight of the polyethylene is 50,000 to 2,000,000 g / mol, such as 50,000 g / mol, 250,000 g / mol, 450,000 g / mol, 650,000 g / mol, 850,000 g / mol, 1,050,000 g / mol, 1,250,000 g / mol, 1,450,000 g / mol, 1,650,000 g / mol, or 2,000,000 g / mol.

[0018] Preferably, the bulk density of the polyethylene is 0.1-0.5 g / mL, such as 0.1 g / mL, 0.2 g / mL, 0.3 g / mL, 0.4 g / mL or 0.5 g / mL.

[0019] On the other hand, the present invention provides a method for preparing high-purity polyethylene as described above, the method comprising the following steps: Polyethylene is added to a purifying agent for purification to obtain high-purity polyethylene. The purifying agent consists of hydrocarbon solvents, alcohol solvents, and additives.

[0020] In this invention, polyethylene with relatively low metal content is prepared by using a highly active catalyst. After purification, the single metal content in the polyethylene is reduced to <1 ppm, the total metal content to <3 ppm, and the Cl element content in the polyethylene to <2 ppm, thus achieving the preparation of ultrapure polyethylene.

[0021] The polyethylene is polyethylene with a total metal content ranging from 50 to 120 ppm (e.g., 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, 100 ppm, 110 ppm or 120 ppm, etc.).

[0022] Preferably, the polyethylene is obtained by copolymerizing ethylene under the catalysis of a Ziegler-Natta catalyst.

[0023] Preferably, the copolymerization reaction is carried out under the protection of a high-purity inert gas, wherein the inert gas is selected from nitrogen.

[0024] Preferably, the copolymerization reaction further includes the addition of a co-catalyst, which is selected from at least one of triethylaluminum, triisobutylaluminum, trimethylaluminum, or trioctylaluminum.

[0025] Preferably, the molar ratio of the co-catalyst to the Ziegler-Natta catalyst is 100:1-30:1 (e.g., 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1 or 100:1, etc.).

[0026] Preferably, the temperature of the copolymerization reaction is 60-90℃ (e.g., 60℃, 63℃, 66℃, 69℃, 72℃, 75℃, 78℃, 81℃, 84℃ or 90℃, etc.), and the reaction time is 1-4h (e.g., 1h, 1.5h, 2h, 2.5h, 3h, 3.5h or 4h, etc.).

[0027] Preferably, the copolymerization reaction is carried out at a pressure of 0.5-2.0 MPa (e.g., 0.5 MPa, 0.875 MPa, 1.25 MPa, 1.625 MPa or 2 MPa).

[0028] Preferably, the raw materials for the copolymerization reaction also include hydrogen. In this invention, the partial pressures of ethylene and hydrogen are adjusted to achieve the experimental values, thereby controlling the resin density and molecular weight distribution.

[0029] Preferably, the partial pressure of ethylene in the reaction system is 0.3-1.5 MPa (e.g., 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa or 1.5 MPa, etc.), and the partial pressure of hydrogen is 0.2-0.5 MPa (e.g., 0.2 MPa, 0.25 MPa, 0.3 MPa, 0.35 MPa or 0.5 MPa, etc.).

[0030] Preferably, the hydrocarbon solvent includes at least one selected from n-pentane, isopentane, n-hexane, cyclohexane, n-heptane, n-octane, benzene, toluene, xylene, p-isopropyltoluene, or decahydronaphthalene. To reduce the residual volatile components in the polymer, a low-boiling-point alkane compound is preferred: at least one selected from n-pentane, isopentane, n-hexane, cyclohexane, n-heptane, or n-octane.

[0031] Preferably, the alcohol solvent includes at least one selected from methanol, ethanol, ethylene glycol, isopropanol, n-butanol, butanediol, sec-butanol, n-pentanol, isopentanol, tert-pentanol, cyclopentanol, or n-hexanol. To reduce the residual volatile components in the polymer, a low-boiling-point alkane compound is preferred: at least one selected from methanol, ethanol, isopropanol, n-butanol, butanediol, sec-butanol, n-pentanol, isopentanol, or tert-pentanol.

[0032] Preferably, the additive is selected from any one or a combination of at least two of the following: ethylenediaminetetraacetic acid (EDTA), aminotriacetic acid (NTA), sodium tripolyphosphate, sodium hexametaphosphate, benzohydroxyxamic acid, salicylic acid, dimercaptopropanol, penicillamine, HEDP, ATMP, citric acid (CA), tartaric acid (TA), gluconic acid (GA), hydroxyethylethylenediaminetriacetic acid (HEDTA), or dihydroxyethylglycine (DEG).

[0033] Preferably, the additive is selected from β-diketones or bisβ-diketones.

[0034] Preferably, the additive is selected from any one or a combination of at least two of the following: acetylacetone (Hacac), dibenzoylmethane (DBM), hexafluoroacetylacetone (Hhfac), trifluoroacetylacetone (Htfac), ethyl acetoacetate, 1,3-bis(acetylacetonyl)propane, and 1,4-bis(benzoylacetoneyl)benzene.

[0035] Preferably, the additive is selected from acidic or alkaline substances.

[0036] Preferably, the additive is selected from any one or a combination of at least two of the following: hydrochloric acid, sulfuric acid, nitric acid, hypochlorous acid, phosphoric acid, sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, or potassium bicarbonate.

[0037] Preferably, the purifying agent contains the following components in weight percentage: 50-99 wt% (e.g., 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, or 99 wt%) of hydrocarbon solvent, 0.5-45 wt% (e.g., 0.5 wt%, 6 wt%, 12 wt%, 18 wt%, 24 wt%, 30 wt%, 36 wt%, or 45 wt%) of alcohol solvent, and 0.5-5 wt% (e.g., 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, or 5 wt%) of additives.

[0038] Preferably, the polyethylene is added to the purifying agent and mixed to obtain a suspension. The polyethylene content in the suspension is 5wt%-50wt%, for example, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, or 50wt%. If the polyethylene solid content in the suspension exceeds 50wt%, some solids will not dissolve in the purifying agent, resulting in low impurity removal efficiency and insignificant deashing effect. If the polyethylene solid content in the suspension is less than 5wt%, the purification process cost will increase, and the deashing effect will be limited and will not improve significantly.

[0039] Preferably, the purification process is carried out at 80℃-110℃ (e.g., 80℃, 82℃, 84℃, 86℃, 88℃, 90℃, 92℃, 94℃, 96℃, 98℃, 100℃, 102℃, 104℃, 106℃ or 110℃, etc.) and at a pressure of 0.1-1.0MPa (e.g., 0.1MPa, 0.2MPa, 0.3MPa, 0.4MPa, 0.5MPa, 0.6MPa, 0.7MPa, 0.8MPa or 1MPa, etc.).

[0040] Preferably, the purification process takes 1-5 hours, such as 1 hour, 1.6 hours, 2.2 hours, 2.8 hours, 3.4 hours, 4 hours, 4.6 hours, or 5 hours.

[0041] On the other hand, the present invention provides an application of the high-purity polyethylene described above in the preparation of wafer carriers, wafer cassettes, pipes, valve components, high-end medical device packaging, ultrapure chemical storage and transportation containers, or power battery separators.

[0042] Compared with the prior art, the present invention has the following beneficial effects: The high-purity polyethylene of this invention has a single metal content of <1 ppm, a total metal content of <3 ppm, and a Cl element content of <2 ppm. This invention achieves the preparation of ultra-pure polyethylene to meet the low metal content requirements of polyethylene in the semiconductor, medical, ultra-pure reagent storage and transportation, and power battery separator fields. Furthermore, this invention is applicable to polyethylene with a molecular weight range of 50,000 g / mol to 2,000,000 g / mol, i.e., solid deashing treatment from low molecular weight polyethylene to ultra-high molecular weight polyethylene, meeting the needs of different fields. Detailed Implementation

[0043] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0044] Preparation Example A1 250 ml of n-hexane was poured into a 500 ml stainless steel reactor, which was then closed. The air in the reactor was replaced with nitrogen at least three times, followed by the replacement of nitrogen with ethylene at least three times. The pressure was increased to 0.7 MPa, and the hydrogen partial pressure was adjusted to 0.3 MPa. Stirring was then started. Triethylaluminum and Zn catalyst were added sequentially. The Zn catalyst was prepared according to Example 1 of patent CN202311271050.9. The molar ratio of triethylaluminum to Zn catalyst was 70:1, and the ratio of ethylene to catalyst was 30 g ethylene / 1 mg catalyst. The reactor was then heated to 80 °C and reacted for 2 hours. The reactor temperature was then lowered to room temperature, and the liquid in the reactor was drained by opening the bottom valve. The solution and polyethylene were poured out and separated. The polyethylene was washed three times with ethanol and then dried in a vacuum oven to obtain polyethylene resin.

[0045] Preparation Example A2 250 ml of n-hexane was poured into a 500 ml stainless steel reactor, which was then closed. The air in the reactor was replaced with nitrogen at least three times, followed by the replacement of nitrogen with ethylene at least three times. The pressure was increased to 0.7 MPa, and the hydrogen partial pressure was adjusted to 0.3 MPa. Stirring was then started. Triethylaluminum and Zn catalyst were added sequentially, with the Zn catalyst prepared according to Example 1 of patent CN202311271050.9. The molar ratio of triethylaluminum to Zn catalyst was 30:1, and the ratio of ethylene to catalyst was 30 g ethylene / 1 mg catalyst. The reactor was then heated to 80 °C and reacted for 1 hour. After the reaction was completed, the reactor was cooled to room temperature, and the liquid in the reactor was drained by opening the bottom valve. The solution and polyethylene were poured out and separated. The polyethylene was washed three times with ethanol and then dried in a vacuum oven to obtain polyethylene resin.

[0046] Preparation Example A3 250 ml of n-hexane was poured into a 500 ml stainless steel reactor, which was then closed. The air in the reactor was replaced with nitrogen at least three times, followed by the replacement of nitrogen with ethylene at least three times. The pressure was increased to 0.7 MPa, and the hydrogen partial pressure was adjusted to 0.3 MPa. Stirring was then started. Triethylaluminum and Zn catalyst were added sequentially, with the Zn catalyst prepared according to Example 1 of patent CN202311271050.9. The molar ratio of triethylaluminum to Zn catalyst was 100:1, and the ratio of ethylene to catalyst was 30 g ethylene / 1 mg catalyst. The reactor was then heated to 80 °C and reacted for 1 hour. After the reaction was completed, the reactor was cooled to room temperature, and the liquid in the reactor was drained by opening the bottom valve. The solution and polyethylene were then separated. The polyethylene was washed three times with ethanol and dried in a vacuum oven to obtain polyethylene resin.

[0047] Preparation Example A4 250 ml of n-hexane was poured into a 500 ml stainless steel reactor, which was then closed. The air in the reactor was replaced with nitrogen at least three times, followed by the replacement of nitrogen with ethylene at least three times. The pressure was increased to 0.7 MPa, and the hydrogen partial pressure was adjusted to 0.2 MPa. Stirring was then started. Triethylaluminum and a high-efficiency Zn catalyst were added sequentially. The Zn catalyst was prepared according to Example 1 of patent CN202311271050.9. The molar ratio of triethylaluminum to Zn catalyst was 70:1, and the ratio of ethylene to catalyst was 30 g ethylene / 1 mg catalyst. The reactor was then heated to 90 °C and reacted for 3 hours. After the reaction was completed, the reactor was cooled to room temperature, and the liquid in the reactor was drained by opening the bottom valve. The solution and polyethylene were poured out and separated. The polyethylene was washed three times with ethanol and then dried in a vacuum oven to obtain polyethylene resin.

[0048] Preparation Example A5 250 ml of n-hexane was poured into a 500 ml stainless steel reactor, which was then closed. The air in the reactor was replaced with nitrogen at least three times, followed by the replacement of nitrogen with ethylene at least three times. The pressure was increased to 0.7 MPa, and the hydrogen partial pressure was adjusted to 0.01 MPa. Stirring was then started. Triethylaluminum and Zn catalyst were added sequentially, with the Zn catalyst prepared according to Example 1 of patent CN202311271050.9. The molar ratio of triethylaluminum to Zn catalyst was 70:1, and the ratio of ethylene to catalyst was 30 g ethylene / 1 mg catalyst. The reactor was then heated to 60 °C and reacted for 3 hours. After the reaction was stopped, the reactor was cooled to room temperature, and the liquid in the reactor was drained by opening the bottom valve. The solution and polyethylene were then separated. The polyethylene was washed three times with ethanol and dried in a vacuum oven to obtain polyethylene resin.

[0049] Preparation Example A6 250 ml of n-hexane was poured into a 500 ml stainless steel reactor, which was then closed. The air in the reactor was replaced with nitrogen at least three times, followed by the replacement of nitrogen with ethylene at least three times. The pressure was increased to 0.7 MPa, and the hydrogen partial pressure was adjusted to 0.15 MPa. Stirring was then started. Triisobutylaluminum and Zn catalyst were added sequentially, with the Zn catalyst prepared according to Example 1 of patent CN202311271050.9. The molar ratio of triisobutylaluminum to Zn catalyst was 70:1, and the ratio of ethylene to catalyst was 30 g ethylene / 1 mg catalyst. The reactor was then heated to 80 °C and reacted for 2 hours. After the reaction was completed, the reactor was cooled to room temperature, and the liquid in the reactor was drained by opening the bottom valve. The solution and polyethylene were then separated. The polyethylene was washed three times with ethanol and dried in a vacuum oven to obtain polyethylene resin.

[0050] The molecular weight and molecular weight distribution of the polyethylene resin materials in the above preparation examples were tested according to GB / T-36214.4-2018, and the test results are shown in Table 1.

[0051] Table 1 The results of metal element content determination of the polyethylene resin materials in the above preparation examples are shown in Table 2.

[0052] Table 2 In the table, " / " indicates that it was not detected.

[0053] Example B1 First, 200g of n-hexane, 50g of isopropanol, and 5g of acetylacetone were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from preparation example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500 rpm, and the temperature was simultaneously turned on to 95°C. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and the purifying agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0054] Example B2 First, 200g of n-hexane, 50g of ethanol, and 5g of acetylacetone were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from preparation example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500 rpm, and the temperature was simultaneously turned on to 95°C. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and purification agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0055] Example B3 First, 200g of n-hexane, 50g of sec-butanol, and 5g of acetylacetone were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from preparation example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500rpm, and the temperature was simultaneously turned on to 95℃. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and the purifying agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0056] Example B4 First, 200g of n-hexane, 50g of isopropanol, and 5g of ethylenediaminetetraacetic acid (EDTA) were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from preparation example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500 rpm, and the temperature was simultaneously turned on to 95°C. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and purification agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0057] Example B5 First, 200g of n-hexane, 50g of isopropanol, and 5g of nitric acid triacetic acid (NTA) were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from preparation example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500 rpm, and the temperature was simultaneously turned on to 95°C. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and the purifying agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0058] Example B6 First, 200g of n-octane, 50g of isopropanol, and 5g of HCl were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from preparation example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500rpm, and the temperature was simultaneously turned on to 95℃. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and purification agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0059] Example B7 First, 200g of n-hexane, 50g of isopropanol, and 5g of sulfuric acid were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from preparation example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500 rpm, and the temperature was simultaneously turned on to 95°C. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and purification agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0060] Example B8 First, 200g of n-hexane, 50g of isopropanol, and 5g of citric acid were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from preparation example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500 rpm, and the temperature was simultaneously turned on to 95°C. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and purification agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0061] Example B9 First, 200g of n-hexane, 50g of isopropanol, and 5g of tartaric acid were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from preparation example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500 rpm, and the temperature was simultaneously turned on to 95°C. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and the purifying agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0062] Example B10 First, 200g of n-octane, 50g of isopropanol, and 5g of gluconic acid were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from preparation example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500rpm, and the temperature was simultaneously turned on to 95℃. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and the purifying agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0063] Example B11 First, 200g of decahydronaphthalene, 50g of isopropanol, and 5g of acetylacetone were poured into a 500ml PTFE-lined stainless steel reactor. Then, 50g of polyethylene from preparation example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500rpm, and the temperature was simultaneously turned on to 95℃. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and the purifying agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0064] Example B12 First, 200g of n-octane, 50g of isopropanol, and 5g of acetylacetone were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from preparation example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500rpm, and the temperature was simultaneously turned on to 90℃. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and purification agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0065] Example B13 First, 200g of toluene, 50g of isopropanol, and 5g of acetylacetone were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from preparation example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500 rpm, and the temperature was simultaneously turned on to 100°C. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and the purifying agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0066] Example B14 First, 200g of n-hexane, 50g of isopropanol, and 2g of acetylacetone were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from preparation example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500rpm, and the temperature was simultaneously turned on to 95℃. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and purification agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0067] Example B15 First, 200g of n-hexane, 50g of isopropanol, and 10g of acetylacetone were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from preparation example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500rpm, and the temperature was simultaneously turned on to 95℃. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and the purifying agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0068] Example B16 First, 200g of n-hexane, 50g of isopropanol, and 5g of acetylacetone were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene produced in Preparation Example A2 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500 rpm, and the temperature was simultaneously turned on to 95°C. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and the purifying agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0069] Example B17 First, 200g of n-hexane, 50g of isopropanol, and 5g of acetylacetone were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene produced in Preparation Example A3 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500rpm, and the temperature was simultaneously turned on to 95°C. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and purification agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0070] Example B18 First, 200g of n-hexane, 50g of isopropanol, and 5g of acetylacetone were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene produced in Preparation Example A4 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500 rpm, and the temperature was simultaneously turned on to 95°C. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and purification agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0071] Example B19 First, 200g of n-hexane, 50g of isopropanol, and 5g of acetylacetone were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene (Example A5) was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500 rpm, and the temperature was simultaneously turned on to 95°C. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and purification agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0072] Example B20 First, 200g of n-hexane, 50g of isopropanol, and 5g of acetylacetone were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of the A6 polyethylene raw material for preparation example was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. Then, the stirring was started at 500rpm, and the temperature was simultaneously turned on to 95℃. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. Then, the polyethylene and purification agent were filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0073] Example B21 First, 200g of n-hexane, 50g of isopropanol, and 5g of acetylacetone were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from preparation example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500rpm, and the temperature was simultaneously turned on to 70°C. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and the purifying agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0074] Example B22 First, 200g of n-hexane, 50g of isopropanol, and 5g of acetylacetone were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from preparation example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500 rpm, and the temperature was simultaneously turned on to 110°C. After being kept at a constant temperature for 1 hour and washed, the temperature was lowered to room temperature. The polyethylene and purification agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0075] Example B23 First, 200g of n-hexane, 50g of isopropanol, and 5g of acetylacetone were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene powder (a commercially available product with a molecular weight of 1.69 million g / mol, a PDI of 15, a bulk density of 0.4g / ml, and a total metal content of 76.4ppm) was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500 rpm, and the temperature was simultaneously turned on to 95°C. After being kept at a constant temperature for 4 hours and washed, the mixture was cooled to room temperature. The polyethylene and purification agent were then filtered, washed three times with ethanol, and vacuum dried to obtain the product.

[0076] Example B24 First, 200g of n-hexane, 50g of sec-butanol, and 5g of dibenzoylmethane (DBM) were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from Preparation Example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500 rpm, and the temperature was simultaneously turned on to 95°C. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and the purifying agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0077] Example B25 First, 200g of n-hexane, 50g of sec-butanol, and 5g of ethyl acetoacetate were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from Preparation Example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500 rpm, and the temperature was simultaneously turned on to 95°C. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and the purifying agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0078] Example B26 First, 200g of n-hexane, 50g of sec-butanol, and 5g of 1,3-bis(acetylacetonyl)propane were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from Preparation Example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500 rpm, and the temperature was simultaneously turned on to 95°C. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and the purifying agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0079] Example B27 First, 200g of n-hexane, 50g of sec-butanol, and 5g of sodium hydroxide were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from preparation example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500rpm, and the temperature was simultaneously turned on to 95℃. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and the purifying agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0080] Example B28 First, 200g of n-hexane, 50g of sec-butanol, and 5g of sodium carbonate were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from Preparation Example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500rpm, and the temperature was simultaneously turned on to 95℃. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and the purifying agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0081] Implementation Example B29 First, 200g of n-hexane, 50g of tert-amyl alcohol, and 5g of acetylacetone were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from preparation example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500rpm, and the temperature was simultaneously turned on to 95℃. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and the purifying agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0082] Example B30 First, 200g of n-hexane, 50g of cyclopentanol, and 5g of acetylacetone were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene (from Preparation Example A1) was added. The reactor was then closed, and the air in the reactor was purged three times with nitrogen. The stirring was then started at 500rpm, and the temperature was simultaneously raised to 95℃. After maintaining this temperature for 4 hours, the mixture was washed and then cooled to room temperature. The polyethylene and purifying agent were then filtered, washed three times with ethanol, and vacuum dried to obtain the product. Example B31 First, 200g of n-hexane, 50g of butanediol, and 5g of acetylacetone were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene (from Preparation Example A1) was added. The reactor was then closed, and the air in the reactor was purged three times with nitrogen. The stirring was then started at 500 rpm, and the temperature was simultaneously raised to 95°C. After maintaining this temperature for 4 hours and washing, the mixture was cooled to room temperature. The polyethylene and purifying agent were then filtered, washed three times with ethanol, and vacuum dried to obtain the product. Example B32 First, 200g of xylene, 50g of butanediol, and 5g of acetylacetone were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene (from Preparation Example A1) was added. The reactor was then closed, and the air in the reactor was purged three times with nitrogen. The stirring was then started at 500rpm, and the temperature was simultaneously raised to 95℃. After maintaining this temperature for 4 hours and washing, the mixture was cooled to room temperature. The polyethylene and purifying agent were then filtered, washed three times with ethanol, and vacuum dried to obtain the product. Example B33 First, 200g of p-isopropyltoluene, 50g of butanediol, and 5g of acetylacetone were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from preparation example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500 rpm, and the temperature was simultaneously turned on to 95°C. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and the purifying agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0083] Comparative Example B1 First, 204g of n-hexane and 51g of isopropanol were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from preparation example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500rpm, and the temperature was simultaneously turned on to 95°C. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and solvent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0084] Comparative Example B2 First, 204g of n-hexane and 51g of isopropanol were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene (preparation example A4) was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500rpm, and the temperature was simultaneously turned on to 95°C. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and solvent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0085] Comparative Example B3 First, 204g of isopropanol and 51g of methanol were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from Preparation Example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500rpm, and the temperature was simultaneously turned on to 95°C. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and solvent were then filtered, washed three times with ethanol, and vacuum dried to obtain the product.

[0086] Comparative Example B4 First, 255g of n-hexane was poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from preparation example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. Then, the stirring was started at 500rpm, and the temperature was simultaneously turned on to 95°C. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. Then, the polyethylene and solvent were filtered, and the product was washed three times with ethanol and dried under vacuum to obtain the product.

[0087] Comparative Example B5 First, 248.8g of n-hexane and 6.2g of acetylacetone were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene from preparation example A1 was added. The reactor was then closed, and the air in the reactor was replaced with nitrogen three times. The stirring was then started at 500rpm, and the temperature was simultaneously turned on to 95℃. After being kept at a constant temperature for 4 hours and washed, the temperature was lowered to room temperature. The polyethylene and purification agent were then filtered, washed three times with ethanol, and dried under vacuum to obtain the product.

[0088] Comparative Example B6 The only difference from Example B1 is that acetylacetone is replaced with an equal mass of 4-methyl-2-pentanone.

[0089] First, 200g of n-hexane, 50g of isopropanol, and 5g of 4-methyl-2-pentanone were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene (from Preparation Example A1) was added. The reactor was then closed, and the air in the reactor was purged three times with nitrogen. The stirring was then started at 500rpm, and the temperature was simultaneously raised to 95℃. After maintaining this temperature for 4 hours and washing, the mixture was cooled to room temperature. The polyethylene and purifying agent were then filtered, washed three times with ethanol, and vacuum dried to obtain the product. Comparative Example B7 The only difference from Example B1 is that acetylacetone is replaced with an equal mass of butyl acetate.

[0090] First, 200g of n-hexane, 50g of isopropanol, and 5g of butyl acetate were poured into a 500ml PTFE-lined stainless steel reactor. Then, 25g of polyethylene (from Preparation Example A1) was added. The reactor was then closed, and the air in the reactor was purged three times with nitrogen. The stirring was then started at 500rpm, and the temperature was simultaneously raised to 95℃. After maintaining this temperature for 4 hours and washing, the mixture was cooled to room temperature. The polyethylene and purifying agent were then filtered, washed three times with ethanol, and vacuum dried to obtain the product. The content of metal elements and chlorine elements in the polyethylene resin materials before and after purification in the above embodiments and comparative embodiments was determined. The detection method for metal elements was SEMI F48, and the detection method for chlorine elements was GB / T 40111-2021. The detection and analysis results are shown in Table 3.

[0091] Table 3 In the table, " / " indicates that it was not detected.

[0092] From the data in Table 3, we can obtain: By using the purification agent of the present invention to post-treat polyethylene, the total content of single metals can be reduced to <1 ppm.

[0093] Compared with Comparative Examples B6 and B7, Example B1 shows that butyl acetate and 4-methyl-2-pentanone are difficult to react with metal elements, thus their effect on removing metal impurities from polyethylene is poor. The complexing agents β-diketones, as well as acids and bases used in the examples, can effectively react with residual metal elements in polyethylene. The resulting metal compounds dissolve in the solvent, thereby significantly reducing the metal impurity content in polyethylene.

[0094] The selection and ratio of alkanes and alcohols have little impact on deashing and are mainly used for impregnation of polyethylene and leaching of metals and their compounds. Therefore, low-boiling-point alkanes and alcohols should be optimized from the perspective of subsequent recycling.

[0095] Increasing the additive content is beneficial for deashing, but it is undesirable for too many additives to remain in the polymer. Therefore, the total amount of additives is selected to be less than or equal to 5 wt.

[0096] While increasing the processing temperature and extending the processing time are beneficial for deashing, it is not advisable to increase the temperature and extend the time excessively, as this would increase energy consumption and also pose a risk of some oligomers dissolving from the polymer.

[0097] Reducing the stirring speed, deashing temperature, and stirring time is detrimental to the deashing effect, mainly because these two parameters have a significant impact on the kinetic diffusion of polar metals and their compounds. Higher stirring speed, higher temperature, and longer stirring time are conducive to diffusion.

[0098] If only polar alcohols are selected in the system, there is almost no deashing effect. Therefore, nonpolar alkanes must be selected, and their role may be related to the wetting of polyethylene. However, if only nonpolar alkanes are selected, the removal effect is also poor. This may be because nonpolar alkanes cannot dissolve polar metals and their compounds.

[0099] For polyethylene of different molecular weights, the purification process can achieve similar metal impurity removal effects, making it applicable to the removal of impurities of different molecular weights.

[0100] The applicant declares that the present invention illustrates the high-purity polyethylene, its preparation method, and its application through the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A high purity polyethylene, characterized in that, The high-purity polyethylene contains less than 1.0 ppm of a single metal impurity, less than 3.0 ppm of total metal impurities, and less than 2 ppm of total chlorine.

2. The high-purity polyethylene according to claim 1, characterized in that, The metallic impurities include any one or a combination of at least two of Na, Ti, Mg, Al, Ca, Fe, Cr, Zn, Ni, Mn, Co, and Mo.

3. The high-purity polyethylene according to claim 1 or 2, characterized in that, The weight-average molecular weight of the polyethylene is 50,000 to 2,000,000 g / mol.

4. The high-purity polyethylene according to any one of claims 1-3, characterized in that, The bulk density of the polyethylene is 0.1-0.5 g / mL.

5. The method for preparing high-purity polyethylene according to any one of claims 1-4, characterized in that, The preparation method includes the following steps: Polyethylene is added to a purifying agent for purification to obtain high-purity polyethylene. The purifying agent consists of hydrocarbon solvents, alcohol solvents, and additives.

6. The preparation method according to claim 5, characterized in that, The polyethylene is polyethylene with a total metal content ranging from 50 to 120 ppm; Preferably, the polyethylene is obtained by copolymerizing ethylene under the catalysis of a Ziegler-Natta catalyst; Preferably, the copolymerization reaction is carried out under the protection of an inert gas, wherein the inert gas is selected from nitrogen; Preferably, the copolymerization reaction further includes the addition of a co-catalyst, wherein the co-catalyst is selected from at least one of triethylaluminum, triisobutylaluminum, trimethylaluminum, or trioctylaluminum; Preferably, the molar ratio of the co-catalyst to the Ziegler-Natta catalyst is 100:1-30:1; Preferably, the copolymerization reaction is carried out at a temperature of 60-90°C and for a reaction time of 1-4 hours.

7. The preparation method according to claim 6, characterized in that, The copolymerization reaction is carried out at a pressure of 0.5-2.0 MPa. Preferably, the raw materials for the copolymerization reaction also include hydrogen gas; Preferably, the partial pressure of ethylene in the reaction system is 0.3-1.5 MPa, and the partial pressure of hydrogen is 0.01-0.5 MPa.

8. The preparation method according to any one of claims 5-7, characterized in that, The hydrocarbon solvent includes at least one of n-pentane, isopentane, n-hexane, cyclohexane, n-heptane, n-octane, benzene, toluene, xylene, p-isopropyltoluene, or decahydronaphthalene, and more preferably at least one of n-pentane, isopentane, n-hexane, cyclohexane, n-heptane, or n-octane; Preferably, the alcohol solvent includes at least one selected from methanol, ethanol, ethylene glycol, isopropanol, n-butanol, butanediol, sec-butanol, n-pentanol, isopentanol, tert-pentanol, cyclopentanol, or n-hexanol; more preferably, it includes at least one selected from methanol, ethanol, isopropanol, n-butanol, butanediol, sec-butanol, n-pentanol, isopentanol, or tert-pentanol. Preferably, the additive is selected from any one or a combination of at least two of the following: ethylenediaminetetraacetic acid, aminotriacetic acid, sodium tripolyphosphate, sodium hexametaphosphate, benzohydroxyxamic acid, salicylic acid, dimercaptopropanol, penicillamine, HEDP, ATMP, citric acid, tartaric acid, gluconic acid, hydroxyethylethylenediaminetriacetic acid, or dihydroxyethylglycine. Preferably, the additive is selected from β-diketones or bisβ-diketones; Preferably, the additive is selected from any one or a combination of at least two of the following: acetylacetone, dibenzoylmethane, hexafluoroacetylacetone, trifluoroacetylacetone, ethyl acetoacetate, 1,3-bis(acetylacetonyl)propane, 1,4-bis(benzoylacetonyl)benzene; Preferably, the additive is selected from acidic or alkaline substances; Preferably, the additive is selected from any one or a combination of at least two of hydrochloric acid, sulfuric acid, nitric acid, hypochlorous acid, phosphoric acid, sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, or potassium bicarbonate.

9. The preparation method according to any one of claims 5-8, characterized in that, The purifying agent contains the following components in weight percentage: 50-99 wt% hydrocarbon solvent, 0.5-45 wt% alcohol solvent, and 0.5-5 wt% additives; Preferably, the polyethylene is added to the purifying agent and mixed to obtain a suspension, wherein the polyethylene content in the suspension is 5wt%-50wt%. Preferably, the purification process is carried out at 80℃-110℃ and a pressure of 0.1-1.0MPa; Preferably, the purification process takes 1-5 hours.

10. The use of high-purity polyethylene according to any one of claims 1-4 in the preparation of wafer carriers, wafer cassettes, pipes, valve components, high-end medical device packaging, ultrapure chemical storage and transportation containers, or power battery separators.

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