Polyolefin deliming method

Abstract

The invention relates to the field of preparation of polymer materials, and discloses a polyolefin deliming method which comprises the following steps: S1, mixing a polyolefin raw material glue solution with an ionization reagent and a chelating agent for reaction to obtain a polyolefin material containing a complex; s2, the polyolefin material containing the complex and a diluent are subjected to first mixing, and the content of polyolefin in every 100 mL of first mixed material liquid is smaller than or equal to 1 g; and S3, carrying out second mixing on the first mixed material liquid and an extraction precipitant, and then separating a solid-phase material from the second mixed material. According to the method, the wrapping of the polyolefin on the metal compound can be reduced, the de-ashing effect is improved, and complex operation and too high material and equipment investment are avoided.

Description

Technical Field

[0001] This invention relates to the field of polymer material preparation, and more specifically, to a method for deashing polyolefins. Background Technology

[0002] With my country's economic development, the demand for high-end polyolefin materials is increasing, such as POE elastomers prepared by copolymerizing ethylene, propylene, and various α-olefins and cyclic olefins, cyclic olefin polymers (COC), linear low-density polyethylene (LLDPE), and ethylene propylene diene monomer (EPDM). These materials possess high volume resistivity, low dielectric constant, excellent optical properties, and outstanding heat and chemical resistance, making them promising for applications in electrical engineering, high-end optics, medical packaging, and medical implants. However, the residual catalyst ash content in polyolefins directly affects their appearance, dielectric, and optical properties, and can also cause degradation and reduce biocompatibility during processing, thus limiting their applications. Therefore, the removal of residual catalysts from polyolefin materials is of great significance for their high-end applications.

[0003] Currently, deashing methods for polyolefins mainly include chelation adsorption, solvent washing and extraction, and coagulation washing. Chelation adsorption involves the use of specialized adsorbents, which need to be specifically designed according to the type of metal ash being removed. These adsorbents are used in large quantities and cannot be regenerated after adsorption, resulting in significant production costs. Furthermore, the non-specific adhesion of polyolefins to the adsorbent inevitably leads to a reduction in production yield. Solvent washing and extraction is simple to operate, typically involving sequentially washing the solid polyolefin in solutions containing acids, alkalis, or chelating agents to remove ash. To enhance the washing effect, multiple washes are usually required to achieve deashing. For example, CN107417796A uses acid, alkali, and water to sequentially wash water-insoluble polymers for deashing, and CN115124635A discloses a deashing process that sequentially washes polyolefins with hydrocarbon solvents, acidic reagents, chelating reagents, and elution reagents. These methods are complex, time-consuming, and resource-intensive, and are not conducive to continuous industrial production. The coagulation-washing method involves using a jet coagulation vessel or similar device to cause high-speed collisions between a polyolefin solution and a precipitant capable of dissolving metal ash. This disperses the solution into fine droplets, ensuring thorough contact between the precipitant and the solution, thereby extracting residual metal compounds. Examples of methods and equipment disclosed in CN106967189A, CN104941558B, and CN101928387A illustrate this approach. However, while this method can achieve highly dispersed polymers, it requires the design of specialized coagulation vessels and jetting systems, increasing equipment costs and the difficulty of operation and industrial implementation. Furthermore, its deashing efficiency is not high.

[0004] Therefore, how to reduce the encapsulation of metal compounds by polyolefins, improve the deashing effect, and avoid complex operations and excessive material and equipment investment are urgent problems to be solved. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem in the prior art where polymer agglomeration during polymer coagulation causes the metal complexes to be encapsulated, resulting in poor deashing effect. This invention provides a method for deashing polyolefins that greatly reduces the encapsulation of metal complexes by polymer agglomeration during polymer coagulation, allowing the metal ion complexes to be completely transferred to the precipitant. This method achieves significant deashing effect, avoids complex operations and excessive material and equipment investment, and is easy to implement industrially.

[0006] To achieve the above objectives, the present invention provides a method for deashing polyolefins, wherein the method includes the following steps:

[0007] S1. The polyolefin raw material solution is mixed with an ionizing reagent and a chelating agent and reacted to obtain a polyolefin material containing a complex.

[0008] S2. The polyolefin material containing the complex is mixed with the diluent in the first mixing, so that the content of polyolefin in each 100mL of the first mixed liquid is less than or equal to 1g.

[0009] S3. The first mixed liquid and the extraction precipitant are mixed a second time, and then the solid phase material is separated from the second mixed material.

[0010] The beneficial effects of the present invention through the above technical solution include at least the following:

[0011] (1) The method of dilute solution coagulation in this invention greatly reduces the size of polyolefin coagulation and increases the specific surface area of ​​coagulated particles, reduces the encapsulation of metal complexes by polyolefin particles, and allows the metal complexes to be completely extracted into the extraction precipitant, which greatly improves the deashing effect.

[0012] (2) In this invention, a large amount of solvent can be initially removed while deashing, which facilitates the subsequent deep devolatilization to obtain high-purity polyolefin.

[0013] (3) The diluents and extraction precipitants used in this invention can be reused or recycled by distillation after use, thus avoiding the huge material consumption problem caused by the preparation of special adsorbents and their non-renewability in the chelation adsorption method.

[0014] (4) The chelation reaction used in this invention can efficiently transform free metal compounds and polyolefin-encapsulated metal compounds in solution into complexes that are easily soluble in precipitants, thereby improving the removal efficiency.

[0015] The deashing method used in the preferred embodiment of the present invention can ultimately remove more than 99.7% of the metal ash residue in polyolefins, reducing the metal ash content to below 5 ppm, and the deashing effect is significant. Detailed Implementation

[0016] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0017] This invention provides a method for deashing polyolefins, wherein the method includes the following steps:

[0018] S1. The polyolefin raw material solution is mixed with an ionizing reagent and a chelating agent and reacted to obtain a polyolefin material containing a complex.

[0019] S2. The polyolefin material containing the complex is mixed with the diluent in the first mixing, so that the content of polyolefin in each 100mL of the first mixed liquid is less than or equal to 1g.

[0020] S3. The first mixed liquid and the extraction precipitant are mixed a second time, and then the solid phase material is separated from the second mixed material.

[0021] In this invention, a polyolefin raw material solution is mixed with an ionizing reagent to ionize the metal compounds in the polyolefin raw material solution. This solution is then mixed with a chelating agent, which chelates the metal ions to form complexes, making them readily soluble in the extraction precipitant. The polyolefin material containing the complexes is diluted with a diluent and then mixed with the extraction precipitant. The metal complexes are extracted into the extraction precipitant, while the polyolefin directly agglomerates to form highly dispersed fine particles or loose debris with a high specific surface area, achieving separation of metal ash and polymer. After solid-liquid separation, purified polyolefin is obtained. The deashing method in this invention can effectively remove metal compounds from polyolefins, with a significant deashing effect. This method utilizes dilute solution agglomeration to greatly reduce the agglomeration size of polyolefins and increase the specific surface area of ​​the agglomerated particles, reducing the encapsulation of metal complexes by polyolefin particles. This allows the metal complexes to be completely extracted into the extraction precipitant, greatly improving the deashing effect. Simultaneously, a large amount of solvent can be initially removed during deashing, facilitating subsequent deep devolatilization. On the other hand, it also avoids the problems of complicated preparation of special adsorption reagents and their non-renewability, reduces material consumption, and is easy to operate continuously and implement on a large scale.

[0022] The present invention does not particularly limit the type of polyolefin in the polyolefin raw material adhesive. The method provided by the present invention is applicable to any polyolefin raw material adhesive. Preferably, the polyolefin in the polyolefin raw material adhesive is selected from at least one of cyclic olefin copolymers, ethylene propylene diene monomer (EPDM) rubber and linear low-density polyethylene, and more preferably cyclic olefin copolymers.

[0023] The inventors have discovered that the method provided by this invention has a better deashing effect on cyclic olefin copolymers (COC), ethylene propylene diene monomer (EPDM), or linear low-density polyethylene (LLDPE) than on other types of polyolefins. The method provided by this invention is particularly effective for cyclic olefin copolymers.

[0024] In a preferred embodiment of the present invention, the COC in the COC raw material solution has a weight-average molecular weight of 10,000-200,000 g / mol, a molecular weight distribution coefficient of 1.1-4.2, a glass transition temperature of 40-200℃, and a molar content of structural units from norbornene in the COC of 20-80%; based on a volume of 100 mL of COC raw material solution, the COC content in the COC raw material solution is 1-80 g. The method provided by the present invention has a better deashing effect on COC raw material solutions that meet these conditions.

[0025] To obtain a COC raw material solution that meets the aforementioned conditions, in a preferred embodiment of the present invention, the preparation method of the COC raw material solution includes: mixing ethylene and norbornene in the presence of a catalyst, a co-catalyst, and a solvent to carry out a polymerization reaction; wherein the catalyst is a metallocene catalyst (rac-[Et(Ind)2]ZrCl2 catalyst), the co-catalyst is methylaluminoxane, and the solvent is toluene. When preparing the COC raw material solution, the molar ratio of ethylene to norbornene is 1:(6-10), and the weight ratio of norbornene to toluene is 1:(16-20); the polymerization reaction temperature is 70-150℃, the pressure is 1.5-5 MPaG, and the time is 15-25 min; based on a volume of 1 L of the obtained mixture, the catalyst content is (7-9) × 10⁻⁶. -5 mol; the amount of catalyst is calculated as Zr, the amount of co-catalyst is calculated as Al, and the molar ratio of co-catalyst to catalyst is (1000-2000):1.

[0026] The present invention does not have any particular limitation on the type of ionizing reagent, as long as it can ionize the metal compounds in the polyolefin raw material solution. Preferably, in S1, the ionizing reagent is an acidic reagent.

[0027] According to the present invention, preferably, the acidic reagent is selected from at least one of sulfuric acid, hydrochloric acid, nitric acid, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, and nonanoic acid.

[0028] The present invention does not have any particular limitation on the type of chelating agent, as long as it can chelate metal ions to generate a coordination compound that is easily soluble in the extraction precipitant. Preferably, in S1, the chelating agent is a β-dicarbonyl compound, more preferably at least one of acetylacetone, benzoylacetone, dibenzoylacetone and trifluoroacetylacetone.

[0029] In this invention, the ionizing reagent and the chelating agent can be added simultaneously or sequentially. The ionizing reagent and the chelating agent can be added directly or prepared into a solution using a gel solvent before being added.

[0030] To further improve the effect of ionizing the metal compound, preferably, in S1, the amount of the ionizing reagent is such that the molar equivalent ratio of the ionizing reagent to the metal compound in the polyolefin raw material solution is (0.1-100):1.

[0031] To further improve the effect of chelating metal ions to generate coordination compounds, preferably, in S1, the volume ratio of the ionizing reagent to the chelating agent is 1:(0.1-10).

[0032] To more fully form the metal compound into a coordination compound, preferably, in S1, the reaction temperature is 50-200°C, the pressure is 0.1-10 MPa, and the time is 0.5-12 h.

[0033] To more fully form the metal compound into a coordination compound, the reaction is preferably carried out at a stirring speed of 50-1000 rpm.

[0034] According to the present invention, preferably, in S2, the diluent is selected from at least one of toluene, cyclohexane and hexane, and more preferably toluene.

[0035] In this invention, the diluent is selected based on the principle of similar compatibility according to the type of polymer, ensuring good solubility of the polymer in the diluent. Preferably, when the polyolefin in the polyolefin raw material adhesive is a cyclic olefin copolymer, toluene is used; when the polyolefin in the polyolefin raw material adhesive is ethylene propylene diene monomer (EPDM) rubber, cyclohexane is used; and when the polyolefin in the polyolefin raw material adhesive is linear low-density polyethylene, hexane is used.

[0036] In S2, in order to accelerate the formation of a stable dilute solution of polyolefin, the first mixing can be carried out under heating conditions. The heating temperature should not exceed the boiling point of the diluent under operating conditions. Preferably, in S2, the first mixing is carried out at 40-100°C.

[0037] In order to ensure that the polyolefin completely forms a stable dilute solution, the polyolefin dilute solution (the first mixed solution) can be stirred magnetically or mechanically for a certain period of time during the preparation or dilution process. Preferably, the first mixing is carried out under stirring conditions, with a stirring speed of 50-1000 rpm and a stirring time of 0.5-10 h.

[0038] To further improve the extraction efficiency of chelated metal ion compounds and the precipitation efficiency of polyolefins, thereby further improving the deashing effect on polyolefin raw materials, preferably, the amount of the extraction precipitant is such that the weight ratio of the extraction precipitant to the polyolefin in the polyolefin raw material solution is (50-1000):1, and the volume ratio of the extraction precipitant to the total volume of the polyolefin raw material solution and the diluent is (1-100):1.

[0039] This invention does not impose any particular limitation on the type of extraction precipitant. The extraction precipitant is selected according to the type of polyolefin. The selection of the extraction precipitant should meet the following requirements: it should have a certain solubility for chelated metal ion compounds in dilute polyolefin solutions, enabling its extraction; it should also be miscible with or have a high solubility with the diluent, forming a homogeneous phase in which the polyolefin can aggregate to form highly dispersed fine particles or loose debris. Preferably, in S3, the extraction precipitant is selected from alcohols, preferably from C1-C20 monohydric alcohols, more preferably from C1-C4 monohydric alcohols, such as at least one of methanol, ethanol, n-propanol, and butanol.

[0040] The present invention does not impose any particular restrictions on the mixing method of the dilute polyolefin solution (the first mixed liquid) and the extraction precipitant. In S3, the dilute polyolefin solution can be poured directly into the extraction precipitant at once, or it can be added drop by drop to the extraction precipitant.

[0041] This invention does not impose particular restrictions on the mixing conditions of the dilute polyolefin solution (the first mixed solution) and the extraction precipitant. The pressure during the second mixing can be atmospheric pressure, and the temperature during the second mixing can be between room temperature and the boiling point of the selected extraction precipitant. The second mixing can be carried out under stirring or without stirring. To ensure more complete extraction of the metal complex by the extraction precipitant and to more thoroughly precipitate the polyolefin as fine particles or loose debris, preferably, the second mixing is carried out under stirring at a speed of 50-1000 rpm for 0.1-12 h.

[0042] This invention does not impose any particular limitation on the method for separating the solid phase material from the second mixed material in step S3. Conventional solid-liquid separation methods in the art can be used, as long as a dry solid phase material can be separated. Preferably, the method for separating the solid phase material from the second mixed material includes: filtering the second mixed liquid and then drying it. The filtration can be performed using centrifugal filtration, positive pressure filtration, or negative pressure filtration, etc., and the drying can be performed using vacuum heating. In a preferred embodiment, the drying temperature is 40-100℃, and the drying time is 5-72 hours.

[0043] The present invention will be described in detail below through examples and comparative examples. Unless otherwise specified, the methods used in the following examples are conventional; the reagents and materials used are commercially available unless otherwise specified.

[0044] Preparation Example

[0045] This preparation example illustrates the method for preparing cyclic olefin copolymer (COC) raw material solutions.

[0046] Preparation of COC raw material solution: Dissolve 5g of norbornene in 90g of refined toluene and add it to the polymerization reactor. Raise the reactor temperature to 120℃ and then introduce dehydrated and deoxygenated high-purity ethylene into the reactor. The molar ratio of ethylene to norbornene is 1:8. After the pressure inside the reactor reaches 2MPa, add rac-[Et(Ind)2]ZrCl2 catalyst and co-catalyst methylaluminoxane (MAO). Based on a total volume of 1L for norbornene, ethylene, toluene, catalyst, and co-catalyst, the catalyst dosage is 8×10⁻⁶. -5 The amount of catalyst used was calculated as Zr, and the amount of co-catalyst used was calculated as Al. The molar ratio of co-catalyst to catalyst was 2000:1. After reacting for 20 min, a COC toluene reaction solution was obtained. The COC content in 100 mL of the solution was determined to be 15 g after precipitation with ethanol. Using trichlorobenzene as solvent, the weight-average molecular weight of the obtained COC was 100,000 g / mol, the molecular weight distribution coefficient was 2.1, and the molar content of structural units from norbornene was 35%. The glass transition temperature was determined to be 80 °C by DSC. The aluminum content was 5300 ppm and the zirconium content was 65 ppm by inductively coupled plasma atomic emission spectrometry (ICP).

[0047] The following examples and comparative examples illustrate the deashing method for the cyclic olefin copolymer (COC) raw materials prepared in the preparation examples.

[0048] Example 1

[0049] Take 10 mL of the COC gel solution prepared in the preparation example, add 2 mL of hydrochloric acid and 2 mL of acetylacetone, heat to 100°C, and react for 8 h at a stirring speed of 500 rpm. Then, add 140 mL of toluene and dilute by stirring at 100°C and 300 rpm for 30 min, so that the COC content in each 100 mL of diluted solution is 1 g. Subsequently, add it to 400 mL of ethanol and stir at a stirring speed of 600 rpm for 15 min to precipitate it. The resulting polyolefin solid was filtered and dried at 60°C for 72 h. ICP analysis showed that the aluminum content was 2.98 ppm, the zirconium content was 0 ppm, and the chlorine content was 0 ppm. Headspace chromatography analysis showed that the residual acetylacetone was 0.1 ppm.

[0050] Example 2

[0051] Take 10 mL of the COC gel solution prepared in the preparation example, add 1 mL of nitric acid and 2 mL of acetylacetone (prepared as a 20% toluene solution), heat to 100°C, and react for 8 hours at a stirring speed of 500 rpm. Then, add 290 mL of toluene and dilute by stirring at 100°C and 300 rpm for 30 minutes to ensure that the COC content in each 100 mL of diluted solution is 0.5 g. Subsequently, add it to 600 mL of methanol and stir at a stirring speed of 600 rpm for 15 minutes to precipitate the product. The resulting polyolefin solid was filtered and dried at 60°C for 72 hours. ICP analysis showed that the aluminum content was 1.5 ppm and the zirconium content was 0 ppm. Headspace chromatography determined the residual acetylacetone content to be 0.11 ppm, and ion chromatography determined the residual nitric acid content to be 0.8 ppm.

[0052] Example 3

[0053] Take 10 mL of the COC solution prepared in the preparation example, add 2 mL of sulfuric acid and 3 mL of benzoylacetone, heat to 100°C, and react for 8 h at a stirring speed of 500 rpm. Then, add 1490 mL of toluene and dilute by stirring at 100°C and 300 rpm for 30 min, so that the COC content in each 100 mL of diluted solution is 0.1 g. Then, add it to 1500 mL of n-propanol and stir at a stirring speed of 600 rpm for 15 min to precipitate it. The resulting polyolefin solid is filtered and dried at 60°C for 72 h. ICP analysis shows that the aluminum content is 0.3 ppm, the zirconium content is 0 ppm, and the sulfur residue is 0.1 ppm; headspace chromatography analysis shows that the benzoylacetone residue is 0 ppm.

[0054] Example 4

[0055] Take 10 mL of the COC gel solution prepared in the preparation example, add 1 mL of acetic acid and 3 mL of benzoylacetone, heat to 150 °C, and react for 10 h at a stirring speed of 500 rpm. Then, add 1490 mL of toluene and dilute by stirring at 100 °C and 300 rpm for 30 min, so that the COC content in each 100 mL of diluted solution is 0.1 g. Then, add it to 1500 mL of butanol and stir at a stirring speed of 600 rpm for 15 min to precipitate it. The resulting polyolefin solid is filtered and dried at 60 °C for 72 h. ICP analysis shows that the aluminum content is 0.3 ppm and the zirconium content is 0 ppm; headspace chromatography analysis shows that the residual benzoylacetone is 0 ppm and the residual acetic acid is 0.2 ppm.

[0056] Example 5

[0057] Take 10 mL of the COC gel solution prepared in the preparation example, add 1 mL of formic acid and 2 mL of benzoylacetone, heat to 100°C, and react for 8 h at a stirring speed of 500 rpm. Then, add 1490 mL of toluene and dilute by stirring at 100°C and 300 rpm for 30 min, so that the COC content in each 100 mL of diluted solution is 0.1 g. Subsequently, add it to 1500 mL of butanol and precipitate it directly without stirring. The resulting polyolefin solid was filtered and dried at 60°C for 72 h. ICP analysis showed that the aluminum content was 3.2 ppm and the zirconium content was 0 ppm. Headspace chromatography analysis showed that the residual benzoylacetone was 0 ppm and the residual formic acid was 0.8 ppm.

[0058] Example 6

[0059] Take 10 mL of the COC gel solution prepared in the preparation example, add 1 mL of propionic acid and 2 mL of trifluoroacetylacetone, heat to 100°C, and react for 8 hours at a stirring speed of 600 rpm. Then, add 1490 mL of toluene and dilute by stirring at 80°C and 400 rpm for 45 minutes to obtain a COC content of 0.1 g per 100 mL of diluted solution. This solution is then added to 1600 mL of n-propanol and stirred at 600 rpm for 6 minutes to precipitate the gel. The resulting polyolefin solid is filtered and dried at 60°C for 72 hours. ICP analysis revealed an aluminum content of 2.8 ppm and a zirconium content of 0 ppm. Headspace chromatography analysis showed a residual trifluoroacetylacetone of 0 ppm and a residual propionic acid of 0.5 ppm.

[0060] Example 7

[0061] The COC raw material solution was deashed according to the method in Example 1, except that the amount of extraction precipitant used was different. Specifically, "then added to 100 mL of ethanol" was replaced with "then added to 400 mL of ethanol". ICP analysis showed that the aluminum content in the obtained polyolefin solid was 8.9 ppm, the zirconium content was 1.1 ppm, and the residual chlorine content was 0 ppm; headspace chromatography analysis showed that the residual acetylacetone was 0.8 ppm.

[0062] Example 8

[0063] The isotactic polypropylene raw material solution was deashed according to the method in Example 1. The preparation method of the isotactic polypropylene raw material solution was as follows: isotactic polypropylene granules (weight-average molecular weight of 344,000 g / mol, molecular weight distribution coefficient of 5.4, isotacticity of 96.2%, melt flow index of 3.74 g / 10 min) were added to cyclohexane and heated to dissolve at 800 rpm and 60°C for 60 min to obtain the solution. The isotactic polypropylene raw material solution contained 10 g of isotactic polypropylene, 180 ppm of aluminum, 50 ppm of magnesium, and 30 ppm of titanium per 100 mL of the isotactic polypropylene raw material solution. ICP analysis revealed that the obtained polyolefin solid contained 8 ppm of aluminum, 1.2 ppm of magnesium, 0.5 ppm of titanium, and 0 ppm of residual chlorine; headspace chromatography determined the residual acetylacetone content to be 0.5 ppm.

[0064] Example 9

[0065] The linear low-density polyethylene (LLDPE) raw material solution was deashed according to the method in Example 1. The preparation method of the LLDPE raw material solution was as follows: LLDPE granules (weight-average molecular weight 90,000 g / mol, molecular weight distribution coefficient 3.1, melting point 122℃) were added to hexane and heated to dissolve at 800 rpm and 60℃ for 60 min to obtain the solution. Each 100 mL of the LLDPE raw material solution contained 8 g of LLDPE, 120 ppm of aluminum, 62 ppm of magnesium, and 25 ppm of titanium. ICP analysis revealed that the obtained polyolefin solid contained 7.2 ppm of aluminum, 2.1 ppm of magnesium, 0.5 ppm of titanium, and 0 ppm of residual chlorine; headspace chromatography determined the residual acetylacetone content to be 0.4 ppm.

[0066] Example 10

[0067] The COC raw material solution was deashed according to the method in Example 1, except that the type of COC in the COC raw material solution was different. The weight-average molecular weight of COC and the content of structural units from norbornene were adjusted by regulating the molar ratio of norbornene and the reaction time, resulting in a COC raw material solution with a weight-average molecular weight of 80,000 g / mol, a molar content of structural units from norbornene of 15%, a molecular weight distribution coefficient of 1.8, and a glass transition temperature of 45°C. Each 100 mL of the COC raw material solution contained 1.5 g of COC, 3200 ppm of aluminum, and 31 ppm of zirconium. ICP analysis revealed an aluminum content of 6.5 ppm, a zirconium content of 1.3 ppm, and a residual chlorine content of 0 ppm in the obtained polyolefin solid; headspace chromatography determined a residual acetylacetone content of 0.8 ppm.

[0068] Example 11

[0069] The COC raw material colloid was deashed according to the method in Example 1, except that "2 mL maleic acid" was used instead of "2 mL acetylacetone". ICP analysis showed that the aluminum content in the obtained polyolefin solid was 18 ppm, the zirconium content was 1.2 ppm, and the residual chlorine content was 0 ppm; headspace chromatography analysis showed that the residual maleic acid was 0.2 ppm.

[0070] Example 12

[0071] The COC raw material colloid was deashed according to the method in Example 1, except that 1-pentanol was used as the extraction complex and the reagent for precipitating COC. ICP analysis showed that the aluminum content in the obtained polyolefin solid was 7.5 ppm, the zirconium content was 1.1 ppm, and the residual chlorine content was 0 ppm; headspace chromatography analysis showed that the residual acetylacetone was 0.8 ppm.

[0072] Comparative Example 1

[0073] The COC raw material colloid was deashed according to the method in Example 1, except that after reacting with hydrochloric acid and acetylacetone, toluene was not added for dilution; instead, it was directly added to 100 mL of ethanol to precipitate the colloid. ICP analysis showed that the obtained polyolefin solid contained 53 ppm aluminum, 3 ppm zirconium, and 0.3 ppm residual chlorine; headspace chromatography determined the residual acetylacetone content to be 1.2 ppm.

[0074] Comparative Example 2

[0075] The COC raw material colloid was deashed according to the method in Example 1, except that "adding 10 mL of toluene" was used instead of "adding 140 mL of toluene". ICP analysis showed that the aluminum content in the obtained polyolefin solid was 35 ppm, the zirconium content was 1.5 ppm, and the residual chlorine content was 0.2 ppm; headspace chromatography analysis showed that the residual acetylacetone content was 0.9 ppm.

[0076] Comparative Example 3

[0077] The COC raw material colloid was deashed according to the method in Example 1, except that "adding 140 mL of acetone" was used instead of "adding 140 mL of toluene". After adding acetone, it was observed that the COC directly agglomerated into clumps and could not be dispersed. ICP measured the aluminum content in the agglomerated sample to be 3800 ppm and the zirconium content to be 42 ppm, indicating that the diluent could not deash the polyolefin if it could not dissolve it.

[0078] Comparative Example 4

[0079] The COC raw material colloid was deashed according to the method in Example 1, except that the type of extraction precipitant was different. Specifically, "add it to 400 mL of benzaldehyde" was used instead of "add it to 400 mL of ethanol". ICP analysis showed that the aluminum content in the obtained polyolefin solid was 450 ppm and the zirconium content was 15 ppm, indicating that the deashing effect was poor when the extraction precipitant could not extract the metal chelate.

[0080] Comparative Example 5

[0081] The COC raw material colloid was deashed according to the method in Example 1, except that the type of extraction precipitant was different. Specifically, "add it to 400 mL of naphtha" was used instead of "add it to 400 mL of ethanol". No COC solid precipitation was observed, and the removal of metallic ash could not be achieved.

[0082] Comparative Example 6

[0083] The COC raw material colloid was deashed according to the method in Example 1, except that "it was added to 400 mL of ethanol" was replaced with "it was added to 400 mL of water". The system presented a two-phase system of water and oil, with no solid precipitation. After stirring and phase separation, the polymer solution was desolventized by a dynamic device to obtain a polyolefin solid. ICP analysis showed that the aluminum content was 4000 ppm and the zirconium content was 45 ppm; deashing could not be achieved.

[0084] The results of the above examples and comparative examples show that the method of the present invention used in Examples 1-12 can effectively deash the cyclic olefin copolymers. Comparative Example 1 did not dilute after reacting with the ionizing reagent and chelating agent; Comparative Example 2 changed the polyolefin content in the diluted solution; the diluent used in Comparative Example 3 could not dissolve the polyolefin; and the extraction and precipitating agents used in Comparative Examples 4-6 could not extract the complex or precipitate the polyolefin, all failing to achieve the purpose of deashing.

[0085] Furthermore, the polyolefin products obtained in Examples 1-6 contained less than 5 ppm of aluminum and less than 1 ppm of zirconium, while almost no residue of chelating agents and acidic reagents was introduced. Example 7 changed the amount of extraction precipitant; Example 8 deashed isotactic polypropylene raw material solution; Example 9 deashed linear low-density polyethylene raw material solution; Example 10 changed the type of COC in the COC raw material solution; Example 11 changed the type of chelating agent; and Example 12 changed the type of extraction precipitant. Compared with Example 1, the polyolefin products obtained in Examples 7-12 showed increased aluminum and zirconium content, and increased residue of chelating agents or acidic reagents. This demonstrates that when the type and amount of extraction precipitant, the type of polyolefin, and the type of chelating agent meet the preferred conditions, the deashing effect of the polyolefin product can be further improved, and the residue of chelating agents and acidic reagents can be further reduced.

[0086] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for deashing polyolefins, characterized in that, The method includes the following steps: S1. The polyolefin raw material solution is mixed with an ionizing reagent and a chelating agent and reacted to obtain a polyolefin material containing a complex. S2. The polyolefin material containing the complex is mixed with the diluent in the first mixing, so that the content of polyolefin in each 100mL of the first mixed liquid is less than or equal to 1g. S3. The first mixed liquid and the extraction precipitant are mixed a second time, and then the solid phase material is separated from the second mixed material.

2. The method according to claim 1, characterized in that, The polyolefin in the polyolefin raw material adhesive is selected from at least one of cyclic olefin copolymers, ethylene propylene diene monomer (EPDM) rubber, and linear low-density polyethylene, preferably cyclic olefin copolymers.

3. The method according to claim 1 or 2, characterized in that, In S1, the ionizing reagent is an acidic reagent; Preferably, the acidic reagent is selected from at least one of sulfuric acid, hydrochloric acid, nitric acid, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, and nonanoic acid.

4. The method according to any one of claims 1-3, characterized in that, In S1, the chelating agent is a β-dicarbonyl compound, preferably at least one of acetylacetone, benzoylacetone, dibenzoylacetone, and trifluoroacetylacetone.

5. The method according to any one of claims 1-4, characterized in that, In S1, the amount of the ionizing agent is such that the molar equivalent ratio of the ionizing agent to the metal compound in the polyolefin raw material solution is (0.1-100):

1.

6. The method according to any one of claims 1-5, characterized in that, In S1, the volume ratio of the ionizing reagent to the chelating agent is 1:(0.1-10).

7. The method according to any one of claims 1-6, characterized in that, In S1, the reaction temperature is 50-200℃, the pressure is 0.1-10MPa, and the time is 0.5-12h; Preferably, the reaction is carried out at a stirring speed of 50-1000 rpm.

8. The method according to any one of claims 1-7, characterized in that, In S2, the diluent is selected from at least one of toluene, cyclohexane, and hexane, preferably toluene.

9. The method according to any one of claims 1-8, characterized in that, In S2, the first mixing is carried out at 40-100°C; Preferably, the first mixing is carried out under stirring conditions, with a stirring speed of 50-1000 rpm and a stirring time of 0.5-10 h.

10. The method according to any one of claims 1-9, characterized in that, In S3, the amount of the extraction precipitant used is such that the weight ratio of the extraction precipitant to the polyolefin in the polyolefin raw material solution is (50-1000):1, and the ratio of the volume of the extraction precipitant to the total volume of the polyolefin raw material solution and the diluent is (1-100):

1. Preferably, the extraction precipitant is selected from alcohols, more preferably from C1-C20 monohydric alcohols, and even more preferably from C1-C4 monohydric alcohols.