Method for removing metal compounds in polyolefin glue solution

Abstract

The invention relates to the field of polymer material preparation, and discloses a method for removing a metal compound in a polyolefin glue solution, and the method comprises the following steps: S1, mixing the polyolefin glue solution with an acidic reagent and a chelating reagent, and carrying out a reaction to obtain a polyolefin feed liquid containing a complex; and S2, mixing the polyolefin feed liquid containing the complex with alcohol, and then separating out polyolefin from the mixed material. According to the method, the metal compound removal effect is remarkable, the problems that a complex special adsorption reagent is prepared and cannot be regenerated are solved, material consumption is reduced, the problem that the yield is reduced due to the fact that polyolefin is adsorbed in the adsorbent in the adsorption process is solved, meanwhile, primary removal of a large amount of solvent can be achieved while the metal compound is removed, and the method is suitable for industrial production. Subsequent volatile matter removal is facilitated, operation is easy, and continuous operation and large-scale industrial implementation are easy.

Description

Technical Field

[0001] This invention relates to the field of polymer material preparation, and more specifically, to a method for removing metal compounds from polyolefin adhesives. 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, the main methods for removing metal compounds from polyolefins include chelation adsorption and solvent washing extraction. Chelation adsorption involves the use of specialized adsorbents, which need to be specifically designed according to the type of metal compound being removed. For example, CN113967460A uses alumina treated with metal hydroxide as the adsorbent; CN114392724A uses alumina treated with pyridine-3-carboxylic acid as the adsorbent; CN114950368A uses sulfuric acid-acidified metal oxide supported on hydroxypiperidine compounds as a deashing adsorbent; and CN113856637A discloses a polyhydroxyamino-modified... Silica is used as an adsorbent for removing metal compounds. CN115926047A discloses an adsorbent for removing metal compounds obtained by copolymerizing unsaturated acid anhydrides, unsaturated carboxylic acids, and unsaturated sulfonic acids. CN115779858A discloses a cross-linked adsorbent for removing metal compounds using unsaturated acid anhydrides, unsaturated carboxylic acids, and unsaturated sulfonic acids supported on activated carbon. CN115739007A discloses an adsorbent for removing metal compounds obtained by reacting ultrafine coal powder, silane coupling agent, and dicarboxylic acid. These types of adsorbents for removing metal compounds often require 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.

[0004] Solvent washing and extraction methods are simple to operate, typically involving washing solid polyolefins in a solution containing acid, alkali, or chelating agents to remove metal compounds. Current methods generally involve directly washing polyolefin particles; however, the contact area between the particles and these solutions is limited, making it difficult to extract and wash away the large number of metal ions encapsulated within the particles. Therefore, it is often necessary to first use a large amount of good solvent to swell or dissolve the polyolefin particles before washing. Furthermore, to enhance the washing effect, multiple washes are usually required to achieve the goal of removing metal compounds. For example, CN107417796A discloses a process for removing metal compounds by sequentially washing water-insoluble polymers with acid, alkali, and water, while CN115124635A discloses a process for removing metal compounds from polyolefins by sequentially washing with hydrocarbon solvents, acidic reagents, chelating reagents, and elution reagents. These methods can only reduce metal compounds to above 100 ppm, showing limited effectiveness in removing metal compounds. Moreover, the numerous steps and long processing time make them unsuitable for industrial production.

[0005] Therefore, there is an urgent need to develop a novel method for removing metal compounds from polymer solutions that can avoid the high material consumption problem in complex chelation adsorption methods, reduce the limited effectiveness of solvent washing and extraction methods, and simultaneously achieve the initial removal of a large amount of solvent while removing metal compounds, facilitating the subsequent removal of volatiles. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of poor removal efficiency and low polyolefin yield in existing technologies. This invention provides a method for removing metal compounds from polyolefin solutions. This method uses an acidic reagent and a chelating reagent to treat the polyolefin solution in a single step. This process generates coordination compounds from the metal compounds, which are then mixed with an alcohol. This process both extracts the chelated metal ions from the polyolefin solution and condenses the polyolefin, resulting in a purified polyolefin solid. This method is highly efficient, simple to operate, avoids the complex preparation of specialized metal compound removal reagents, reduces material consumption, and simultaneously removes most of the solvent while removing the metal compounds, facilitating subsequent deep devolatilization and yielding a high-purity polyolefin product.

[0007] To achieve the above objectives, the present invention provides a method for removing metal compounds from polyolefin adhesives, wherein the method includes the following steps:

[0008] S1. The polyolefin adhesive solution is mixed with an acidic reagent and a chelating reagent and reacted to obtain a polyolefin liquid solution containing a complex.

[0009] S2. Mix the polyolefin liquid containing the complex with alcohol, and then separate the polyolefin from the mixture.

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

[0011] (1) This invention employs chelation extraction to treat polyolefin solutions for the removal of metal compounds. During the chelation reaction, the chelating agent comes into full contact with the polyolefin solution, resulting in a thorough reaction that effectively transforms the metal compounds encapsulated in the polyolefin into complexes readily soluble in alcohol extractants. During extraction, the metal complexes come into full contact with the alcohol extractant, thus being effectively extracted, achieving highly efficient removal of metal compounds.

[0012] (2) In this invention, polyolefins are directly precipitated in solid form during the process of removing metal compounds, achieving primary devolatilization, which facilitates subsequent deep devolatilization to obtain high-purity polyolefins.

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

[0014] (4) The operation method of this invention is simple, avoiding the complicated operation of the washing and extraction method for removing metal compounds, and the effect of removing metal compounds is far superior to that of the washing and extraction method.

[0015] (5) The metal compound removal reagent used in this invention can be simply compounded with commercially available reagents, thus avoiding the complex adsorbent preparation process in the adsorption method. 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 removing metal compounds from polyolefin adhesives, wherein the method includes the following steps:

[0018] S1. The polyolefin adhesive solution is mixed with an acidic reagent and a chelating reagent and reacted to obtain a polyolefin liquid solution containing a complex.

[0019] S2. Mix the polyolefin liquid containing the complex with alcohol, and then separate the polyolefin from the mixture.

[0020] In this invention, a polyolefin solution is mixed with an acidic reagent to ionize the metal compounds in the polyolefin solution. This ionization is then combined with a chelating reagent, which chelates the metal ions to form a complex. The polyolefin solution containing the complex is then mixed with an alcohol. Simultaneously, the metal complex is extracted, and the polyolefin precipitates directly, achieving separation of the metal compound and the polymer. The method of this invention significantly removes metal compounds, avoiding the complex preparation and non-renewable nature of specialized adsorption reagents, reducing material consumption, and minimizing yield reduction caused by polyolefin adsorption in the adsorbent. Furthermore, it achieves preliminary removal of a large amount of solvent while removing metal compounds, facilitating subsequent removal of volatiles. The method is simple to operate and suitable for continuous operation and large-scale industrial implementation.

[0021] This invention does not particularly limit the type of polyolefin in the polyolefin adhesive. The method provided by this invention is applicable to any polyolefin adhesive. Preferably, the polyolefin in the polyolefin adhesive is selected from at least one of cyclic olefin copolymers, ethylene propylene diene monomer (EPDM) rubber, and linear low-density polyethylene, and is preferably a cyclic olefin copolymer.

[0022] The inventors have discovered that the method provided by this invention has a better effect on removing metal compounds from cyclic olefin copolymer (COC) adhesives, ethylene propylene diene monomer (EPDM) adhesives, or linear low-density polyethylene (LLDPE) adhesives than on other types of polyolefin adhesives. The method provided by this invention is particularly effective at removing metal compounds from cyclic olefin copolymer adhesives.

[0023] In a preferred embodiment of the present invention, the COC in the COC adhesive solution has a weight-average molecular weight of 20,000-150,000 g / mol, a molecular weight distribution coefficient of 1.2-3, a glass transition temperature of 50-200℃, and a molar content of structural units derived from norbornene in the COC of 30-80%; based on a volume of 100 mL of COC adhesive solution, the COC content in the COC raw material adhesive solution is 1-80 g. The method provided by the present invention has a better effect on removing metal compounds from COC adhesive solutions that meet these conditions.

[0024] To obtain a COC adhesive solution that meets the aforementioned conditions, in a preferred embodiment of the present invention, the preparation method of the COC adhesive 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 adhesive solution, the molar ratio of ethylene to norbornene is 1:(7-13), and the weight ratio of norbornene to toluene is 1:(6-12); the polymerization reaction temperature is 50-150℃, the pressure is 1-3 MPaG, and the time is 25-35 min; based on a volume of 1 L of the obtained mixture, the catalyst content is (5-8) × 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.

[0025] The present invention does not have any particular limitation on the type of acidic reagent, as long as it can ionize the metal compounds in the polyolefin adhesive. It can be selected from inorganic acids or organic acids. Preferably, in S1, 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.

[0026] The present invention does not have any particular limitation on the type of chelating reagent, as long as it can chelate metal ions to generate a coordination compound that is easily soluble in alcohol. Preferably, in S1, the chelating reagent is a β-dicarbonyl compound, preferably at least one of acetylacetone, benzoylacetone, dibenzoylacetone and trifluoroacetylacetone.

[0027] In this invention, the acidic reagent and the chelating reagent can be added simultaneously or sequentially. The acidic reagent and the chelating reagent can be added directly or prepared into a solution using a gel solvent before being added.

[0028] To further improve the effect of ionizing the metal compound, preferably, in S1, the amount of acidic reagent used is such that the molar equivalent ratio of the acidic reagent to the metal compound in the polyolefin adhesive is (0.1-10):1.

[0029] To further improve the effect of chelating metal ions to form coordination compounds, preferably, in S1, the volume ratio of the acidic reagent to the chelating reagent is 1:(0.1-10).

[0030] 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.

[0031] 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.

[0032] This invention does not impose any particular limitation on the type of alcohol. The type of alcohol is selected according to the type of polyolefin. The alcohol should be selected to have a certain solubility for the metal complex in the polyolefin solution, enabling its extraction. The alcohol should also be miscible with the solvent in the polyolefin solution and be able to precipitate the polyolefin. Preferably, in S2, the alcohol is selected from C1-C4 monohydric alcohols, such as at least one selected from methanol, ethanol, n-propanol, and butanol.

[0033] In order to further improve the extraction efficiency of metal complexes and the precipitation efficiency of polyolefins, thereby further improving the removal effect of metal compounds in polyolefin colloids, preferably, in S2, the amount of alcohol used is such that the volume ratio of alcohol to polyolefin colloid is (1-50):1, and the weight ratio of alcohol to polyolefin in polyolefin colloid is (20-500):1.

[0034] The present invention does not impose any particular restrictions on the mixing method of the polyolefin liquid containing the complex and the alcohol. The polyolefin liquid containing the complex can be added directly to the alcohol in one go, or the polyolefin liquid containing the complex can be added to the alcohol drop by drop. Preferably, the polyolefin liquid containing the complex is added to the alcohol drop by drop.

[0035] This invention does not impose particular restrictions on the mixing conditions of the polyolefin feed solution containing the complex and the alcohol. The mixing pressure can be atmospheric pressure, and the mixing temperature can be greater than or equal to 20°C and less than or equal to the boiling point of the alcohol at the same pressure. To ensure more complete extraction of the metal complex by the alcohol and more thorough precipitation of the polyolefin, in a preferred embodiment, the mixing is carried out under stirring conditions, with a stirring speed of 50-1000 rpm and a stirring time of 0.1-12 h.

[0036] This invention does not impose any particular limitation on the method for separating polyolefins from the mixture in step S2. Conventional solid-liquid separation methods in the art can be used, as long as a dry polyolefin product can be separated. Preferably, the method for separating polyolefins from the mixture includes: filtering the mixture and then drying it. Filtration can be performed using centrifugal filtration, positive pressure filtration, or negative pressure filtration, etc., and drying can be performed using vacuum heating. In a preferred embodiment, the drying temperature is 40-100°C, and the drying time is 5-72 hours.

[0037] 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.

[0038] Preparation Example

[0039] This preparation example illustrates the method for preparing cyclic olefin copolymer (COC) solutions.

[0040] Preparation of the toluene reaction solution for cyclic olefin polymer (COC): 10g of norbornene was dissolved in 90g of purified toluene and added to a polymerization reactor. The reactor temperature was raised to 60℃, and then high-purity ethylene (dehydrated and deoxygenated) was introduced into the reactor. The molar ratio of ethylene to norbornene was 1:10. After the pressure inside the reactor reached 1MPa, rac-[Et(Ind)2]ZrCl2 catalyst and methylaluminoxane (MAO) co-catalyst were added. The catalyst dosage was 6 × 10⁻⁶ L, based on a total volume of 1L for norbornene, ethylene, toluene, catalyst, and co-catalyst. -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 30 min, a COC toluene reaction solution was obtained. The COC content in 100 mL of the solution was determined to be 8 g after precipitation with ethanol. Using trichlorobenzene as solvent, the weight-average molecular weight of the obtained COC was 70,000 g / mol and the molecular weight distribution coefficient was 1.9, as determined by high-temperature GPC. NMR analysis showed that the molar content of structural units from norbornene was 50%. The glass transition temperature was determined to be 145 °C by differential scanning calorimetry. The aluminum content was 4500 ppm and the zirconium content was 50 ppm by inductively coupled plasma atomic emission spectrometry (ICP).

[0041] The following examples and comparative examples illustrate a method for removing metal compounds from the cyclic olefin copolymer (COC) solution prepared in the preparation example.

[0042] Example 1

[0043] Take 10 mL of the COC gel solution prepared in the preparation example, add 0.4 mL of hydrochloric acid and 2 mL of acetylacetone, heat to 100 °C, react at 500 rpm for 1 h, then add to 100 mL of ethanol, stir at 25 °C and 500 rpm for 10 min to precipitate polyolefin solids. The obtained polyolefin solids are filtered and dried at 60 °C for 72 h. ICP analysis revealed an aluminum content of 28 ppm, a zirconium content of 0.8 ppm, and a residual chlorine content of 0 ppm; headspace chromatography determined a residual acetylacetone content of 0.2 ppm.

[0044] Example 2

[0045] Take 10 mL of the COC gel solution prepared in the preparation example, add 1 mL of sulfuric acid and 2 mL of benzoyl acetone, heat to 100°C, react at 500 rpm for 1 h, then add to 100 mL of methanol, stir at 25°C and 500 rpm for 10 min to precipitate polyolefin solids. The obtained polyolefin solids are filtered and dried at 60°C for 72 h. ICP analysis revealed an aluminum content of 23 ppm, a zirconium content of 0 ppm, and a sulfur residue of 0.1 ppm; headspace chromatography analysis revealed a benzoyl acetone residue of 0.1 ppm.

[0046] Example 3

[0047] 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 150 °C, and react for 2 h at a stirring speed of 500 rpm. Then add it to 100 mL of n-propanol and stir for 10 min at 30 °C and a stirring speed of 600 rpm to precipitate polyolefin solids. The obtained polyolefin solids are filtered and dried at 60 °C for 72 h. ICP analysis shows that the aluminum content is 24 ppm and the zirconium content is 0 ppm; headspace chromatography shows that the residual acetylacetone is 0.1 ppm and ion chromatography shows that the residual nitric acid is 0.8 ppm.

[0048] Example 4

[0049] Take 10 mL of the COC gel solution prepared in the preparation example, add 2 mL of propionic acid and 2 mL of benzoylacetone, heat to 100°C, react at 500 rpm for 1 h, then add to 100 mL of butanol, stir at 20°C and 600 rpm for 10 min to precipitate polyolefin solids. The obtained polyolefin solids are filtered and dried at 60°C for 72 h. ICP analysis shows an aluminum content of 21 ppm and a zirconium content of 0 ppm; headspace chromatography analysis shows a residual benzoylacetone content of 0.1 ppm and a residual propionic acid content of 0 ppm.

[0050] Example 5

[0051] Take 10 mL of the COC gel solution prepared in the preparation example, add 1 mL of acetic acid and 2 mL of benzoyl acetone, heat to 100°C, react at 600 rpm for 1 h, then add to 100 mL of ethanol, stir at 40°C and 500 rpm for 20 min to precipitate polyolefin solids. The obtained polyolefin solids are filtered and dried at 60°C for 72 h. ICP analysis shows that the aluminum content is 23 ppm, the zirconium content is 0 ppm, and the residual chlorine content is 0 ppm. Headspace chromatography analysis shows that the residual benzoyl acetone is 0.1 ppm and the residual acetic acid is 0 ppm.

[0052] Example 6

[0053] Take 10 mL of the COC gel solution prepared in the preparation example, add 1 mL of acetic acid and 2 mL of acetylacetone, heat to 100°C, and react for 1 h at a stirring speed of 600 rpm. Then add it to 200 mL of methanol and stir for 10 min at 40°C and a stirring speed of 600 rpm to precipitate polyolefin solids. The obtained polyolefin solids are filtered and dried at 60°C for 72 h. ICP analysis shows that the aluminum content is 25 ppm and the zirconium content is 0 ppm. Headspace chromatography analysis shows that the residual acetylacetone is 0.1 ppm and the residual acetic acid is 0.2 ppm.

[0054] Example 7

[0055] Metal compounds were removed from the isotactic polypropylene solution according to the method in Example 1. The isotactic polypropylene solution was prepared 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. Each 100 mL of solution contained 10 g of isotactic polypropylene, 180 ppm of aluminum, 50 ppm of magnesium, and 30 ppm of titanium. ICP analysis revealed that the obtained polyolefin solid contained 31 ppm of aluminum, 2.3 ppm of magnesium, 0.8 ppm of titanium, and 0 ppm of residual chlorine; headspace chromatography determined the residual acetylacetone to be 0.5 ppm.

[0056] Example 8

[0057] Metal compounds were removed from the linear low-density polyethylene (LLDPE) solution according to the method in Example 1. The LLDPE solution was prepared as follows: LLDPE granules (weight-average molecular weight 90,000 g / mol, molecular weight distribution coefficient 3.1, melting point 122°C) were added to hexane and heated at 800 rpm and 60°C for 60 min to obtain the solution. Each 100 mL of 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 25 ppm of aluminum, 2.1 ppm of magnesium, 1.2 ppm of titanium, and 0 ppm of residual chlorine; headspace chromatography determined the residual acetylacetone content to be 0.4 ppm.

[0058] Example 9

[0059] The method of Example 1 was used to remove metal compounds from the COC solution, except that the type of COC in the COC solution was different. The weight-average molecular weight of the 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 solution with a weight-average molecular weight of 80,000 g / mol, a molar content of structural units from norbornene of 20%, a molecular weight distribution coefficient of 2.52, and a glass transition temperature of 80°C. Each 100 mL of the solution contained 5 g of COC, 3100 ppm of aluminum, and 44 ppm of zirconium. ICP analysis revealed that the resulting polyolefin solid contained 31 ppm of aluminum, 1.2 ppm of zirconium, and 0 ppm of residual chlorine; headspace chromatography determined the residual acetylacetone to be 0.8 ppm.

[0060] Example 10

[0061] The method described in Example 1 was used to remove metal compounds from the COC solution, except that the type of acidic reagent was different. Specifically, "0.4 mL citric acid" was used instead of "0.4 mL hydrochloric acid". ICP analysis showed that the aluminum content in the obtained polyolefin solid was 35 ppm, the zirconium content was 2.0 ppm, and headspace chromatography analysis showed that the residual citric acid was 0.2 ppm and the residual acetylacetone was 0.5 ppm.

[0062] Example 11

[0063] The method described in Example 1 was used to remove metal compounds from the COC solution, except that the type of alcohol was different. Specifically, "add it to 100 mL of 1-pentanol" was used instead of "add it to 100 mL of ethanol". ICP analysis showed that the resulting polyolefin solid contained 45 ppm aluminum, 5.0 ppm zirconium, and 0 ppm residual chlorine; headspace chromatography determined the residual acetylacetone to be 0.8 ppm.

[0064] Example 12

[0065] The method described in Example 1 was used to remove metal compounds from the COC solution, except that the volume ratio of the acidic reagent and the chelating reagent was different. Specifically, "adding 0.05 mL of hydrochloric acid and 2 mL of acetylacetone" was used instead of "adding 0.4 mL of hydrochloric acid and 2 mL of acetylacetone". ICP analysis revealed that the resulting polyolefin solid contained 65 ppm aluminum, 3.1 ppm zirconium, and 0 ppm residual chlorine; headspace chromatography determined the residual acetylacetone content to be 0.8 ppm.

[0066] Example 13

[0067] The method described in Example 1 was used to remove metal compounds from the COC solution, except that the amount of alcohol used was different. Specifically, "add it to 5 mL of ethanol" was used instead of "add it to 100 mL of ethanol". ICP analysis showed that the aluminum content in the obtained polyolefin solid was 35 ppm, the zirconium content was 2.3 ppm, and the residual chlorine content was 0 ppm; headspace chromatography analysis showed that the residual acetylacetone content was 0.8 ppm.

[0068] Comparative Example 1

[0069] The metal compounds in the COC adhesive were removed according to the method in Example 1, except that "adding 1 mL of hydrochloric acid" was used instead of "adding 0.4 mL of hydrochloric acid and 2 mL of acetylacetone". ICP analysis revealed that the resulting polyolefin solid contained 437 ppm aluminum, 23 ppm zirconium, and 0 ppm residual chlorine.

[0070] Comparative Example 2

[0071] The method described in Example 1 was used to remove metal compounds from the COC solution, except that "adding 1 mL of acetylacetone" was used instead of "adding 0.4 mL of hydrochloric acid and 2 mL of acetylacetone". ICP analysis showed that the aluminum content in the resulting polyolefin solid was 3800 ppm and the zirconium content was 37 ppm; headspace chromatography determined that the residual acetylacetone was 0.1 ppm.

[0072] Comparative Example 3

[0073] The method of Example 1 was used to remove metal compounds from COC solution, except that "adding it to 100 mL of ethanol" was replaced with "adding it to 100 mL of toluene". The resulting system was still homogeneous, with no solid precipitation, and deashing could not be achieved.

[0074] Comparative Example 4

[0075] The method of Example 1 was used to remove metal compounds from COC adhesive solution, except that "add it to 100 mL of water" was used instead of "add it to 100 mL of ethanol". The system showed two phases of water and oil with no solid precipitation. After stirring and phase separation, the polymer solution was desolventized by dynamic equipment to obtain polyolefin solid. ICP analysis showed that the aluminum content was 3800 ppm and the zirconium content was 42 ppm. Deashing could not be achieved.

[0076] Comparative Example 5

[0077] The method described in Example 1 was used to remove metal compounds from the COC solution, except that 10 mL of the COC solution was first precipitated in ethanol, and then hydrochloric acid and acetylacetone were added. ICP analysis showed that the aluminum content in the resulting polyolefin solid was 2200 ppm and the zirconium content was 18 ppm; headspace chromatography determined that the benzoylacetone residue was 0.1 ppm.

[0078] Comparative Example 6

[0079] The method described in Example 1 was used to remove metal compounds from the COC adhesive solution. The difference was that, instead of precipitation in ethanol after treatment with hydrochloric acid and acetylacetone, activated alumina particles were added, and the solution was heated for 1 hour before filtration to obtain a polymer solution. After solvent removal using a dynamic apparatus, a polyolefin solid was obtained. ICP analysis revealed an aluminum content of 4400 ppm and a zirconium content of 37 ppm, indicating that under acidic conditions, the metals in the adsorbent dissolve into the polymer, resulting in no metal removal effect.

[0080] The results of the above examples and comparative examples show that the method provided by this invention in Examples 1-13 can efficiently remove metal compounds from polyolefin adhesives while introducing virtually no residue of chelating agents and acidic reagents. Comparative Examples 1 and 2 did not add chelating agents or acidic reagents, respectively; Comparative Examples 3 and 4 did not use alcohol, but instead used toluene and water to mix with the polyolefin liquid containing the complex; Comparative Example 5 first precipitated the polyolefin before adding chelating agents and acidic reagents; Comparative Example 6 did not precipitate the polyolefin liquid containing the complex in alcohol, but instead added activated alumina particles. Compared with Examples 1-13, Comparative Examples 1-6 could not effectively remove metal compounds from the adhesive.

[0081] Furthermore, Examples 7-9 changed the type of polyolefin, Example 10 changed the type of acidic reagent, Example 11 changed the type of alcohol, Example 12 changed the volume ratio of acidic reagent to chelating reagent, and Example 13 changed the amount of alcohol. Compared with Example 1, the content of metal compounds in the polyolefin solids obtained in Examples 7-13 increased, and the residual amount of chelating reagent or acidic reagent also increased. This shows that when the type of polyolefin, the type of acidic reagent, the type and amount of alcohol, and the volume ratio of acidic reagent to chelating reagent meet the preferred conditions, the effect of removing metal compounds can be further improved, and the residual amount of chelating reagent and acidic reagent can be further reduced.

[0082] 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 removing metal compounds from polyolefin adhesives, characterized in that, The method includes the following steps: S1. The polyolefin adhesive solution is mixed with an acidic reagent and a chelating reagent and reacted to obtain a polyolefin liquid solution containing a complex. S2. Mix the polyolefin liquid containing the complex with alcohol, and then separate the polyolefin from the mixture.

2. The method according to claim 1, characterized in that, The polyolefin in the polyolefin 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 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 acidic reagent used is such that the molar equivalent ratio of the acidic reagent to the metal compound in the polyolefin adhesive is (0.1-10):

1.

6. The method according to any one of claims 1-5, characterized in that, In S1, the volume ratio of the acidic reagent to the chelating reagent 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 alcohol is selected from C1-C4 monohydric alcohols.

9. The method according to any one of claims 1-8, characterized in that, In S2, the amount of alcohol used makes the volume ratio of alcohol to polyolefin adhesive (1-50):1, and the weight ratio of polyolefin in alcohol to polyolefin adhesive (20-500):

1.

10. The method according to any one of claims 1-9, characterized in that, In S2, the mixing temperature is greater than or equal to 20°C and less than or equal to the boiling point of the alcohol under the same pressure; Preferably, the mixing is carried out under stirring conditions, with a stirring speed of 50-1000 rpm and a stirring time of 0.1-12 h.