Method for polymer deashing

Abstract

A method for polymer deashing is provided. The method includes mixing a polymer solution to be treated with one or a combination of a plurality of dicarboxylic acids and their derivatives for reaction to obtain a mixed solution, and washing the mixed solution with water, wherein the obtained oil phase is the polymer solution after deashing. The method of the present invention adopts a dicarboxylic acid having a cis structure in its spatial arrangement and its derivatives as a metal complexing agent to react with metal ions in the polymer solution to form a stable metal complex, has the advantage of efficiently complexing and removing metals, and can significantly improve the removal rate of metals in the polymer solution.

Description

Technical Field

[0001] The present invention relates to a method for polymer deashing and belongs to the technical field of polymer deashing.

Background Art

[0002] Copolymers of ethylene and α-olefins, cycloolefins have, as functional polyolefin materials, advantages such as excellent mechanical strength, machinability, and excellent chemical corrosion resistance, and are also excellent in performance such as optical performance, gas barrier properties, chemical resistance, and light resistance. They play an irreplaceable role in industry, agriculture, national defense, transportation, and people's daily lives, and have broad application prospects.

[0003] Currently, in the industry, the production of polyolefin products is often carried out using an efficient metallocene olefin polymerization catalyst system. Generally, metallocene catalysts contain elements of Groups IVB, VB, and VIB of the periodic table, especially vanadium, titanium, and zirconium, and cocatalysts mainly contain elements such as aluminum. These catalysts are generally called transition metal catalysts and have high olefin polymerization catalytic activity. However, once the polymerization is completed, the metal in the catalyst remains in the polyolefin product, which has an adverse effect on the appearance performance, dielectric properties, optical performance, medical material performance, etc. of the final product. Therefore, for polyolefin products, especially high-grade polyolefin products such as medical grades and optical grades, how to efficiently remove the residual metal (abbreviated as deashing) is of the utmost importance.

[0004] In the process of polymer industrialization, the commonly used ash removal methods mainly include aqueous phase extraction method, coagulation sedimentation method and complexation adsorption method. Here, the complexation adsorption method is the most used ash removal method in polymer industrial production, which has the advantages of simple process, large adsorption capacity, high removal efficiency, few interference factors and good stability. Complexing agents are roughly classified into two types: inorganic and organic. Inorganic complexing agents are usually easy to decompose at high temperatures and are only applicable to alkaline media, so their application range is limited. Although organic complexing agents have a wide application range, it is usually difficult to reduce the metal content in the polymer solution to less than 10 ppm. In addition, in the industrialization process, complexation and ash removal are generally carried out using a supported adsorbent filler. Such an adsorbent is a solid filler produced by immersing and roasting an alumina carrier and a complexing agent material, and the effective loading amount of the complexing agent is low, so there are certain limitations in application.

[0005] US4992529A discloses a method for removing metals with a mixed acid. The method generates a carboxylate that does not dissolve in the organic phase by reacting a monocarboxylic acid with a metal in the organic phase, and generates an inorganic salt that dissolves in the aqueous phase by reacting the carboxylate with an inorganic acid in the mixed acid. The carboxylic acid is reduced and returns to the organic phase again, and further reacts with the metal in the polymer solution to generate a carboxylate. This process is repeated until the metal in the polymer solution completely migrates to the aqueous phase, thereby achieving the removal of residual metals. Here, the carboxylic acid acts as a phase transfer catalyst. Although the concept of this method is novel, the removal effect is not satisfactory, and a large amount of water is required.

[0006] CN114534694A discloses a chelating adsorption filler, its manufacturing method and use. The adsorption filler is a molecular sieve filler carrying a quinolinol compound, and an organic acid can be carried on the molecular sieve carrying the quinolinol compound. The adsorption filler can effectively remove the residual catalyst in the polyolefin solution, and has advantages such as a fast ash removal rate, a large adsorption capacity, and a small pressure loss, and is suitable for the removal of catalysts in various olefin solution polymerization processes. However, the manufacturing process of the adsorption filler is complex and cumbersome. At the same time, due to the low loading amount of quinolinol, the adsorption capacity of the adsorption filler is low and the operation cost is high.

[0007] CN114989331A discloses a method for chelating and deashing a polyolefin solution. The method includes: (1) adding triazaamidine to the polyolefin solution to chelate and adsorb metal ions in the solution to form a complex; and (2) passing the polyolefin solution containing the complex through an adsorption column filled with a porous metal oxide for adsorption treatment to obtain a purified polyolefin solution. The deashing method can efficiently remove the residual metal in the polyolefin solution, the process is simple, the swelling of the filler is low, the pressure loss of the system is low, the service life of the deashing filler is long, the exchange cycle of the adsorption column is long, and the treatment cost can be significantly reduced. However, since the complexing ability of triazaamidine with respect to metals is ordinary, the removal rate of metals is low, especially when the content of metal aluminum in the polymer is high.

[0008] CN102875702A discloses a method for removing metals in a polymer. To achieve the purpose of removing the residual metal in the latex, the method adopts the method of adding an organic base, such as n-butyllithium, phenyllithium, etc. to the colloidal solution, adding an oxidizing agent, washing with water after the reaction, and finally centrifuging. This method has a high removal efficiency of the residual metal in the polymer, but because an organic base is used and some metal ions are introduced, the cost of raw material input and residual catalyst removal is high, and the requirements for equipment due to the addition of the organic base are high.

[0009] CN114392724A discloses a dedicated deashing adsorbent for polyolefins, its manufacturing method and use. The deashing adsorbent is prepared by using pyridine-3-carboxylic acid as a complexing agent and supporting it on an oxide carrier. The deashing adsorbent can efficiently remove residual metals in a polyolefin solution, significantly reduce the residual metals in polyolefin products, and has advantages such as a fast deashing rate, a large adsorption capacity, low swelling, and low solution pressure loss compared with the conventional chelating adsorption method. However, the manufacturing process of the deashing adsorbent is complex and cumbersome, and due to the low loading amount of pyridine-3-carboxylic acid, the adsorption capacity of the adsorbent is low and the operating cost is high.

[0010] CN113856637A discloses a method for removing residual metals in the production process of COC and COP by a complexing adsorption filler. Compared with the conventional adsorption resin, the adsorption filler has advantages such as a fast metal deashing rate and a large adsorption capacity, and at the same time, there is no swelling phenomenon. The adsorption filler is produced by reacting silica solid, a solvent, and phosphorus tribromide in a specified ratio to obtain silica bromide solid, further reacting with an appropriate amount of diethyl iminodiacetate to obtain a yellow solid, and then acidifying with hydrochloric acid to obtain the adsorption filler. The manufacturing process of the adsorption filler is complex and cumbersome, and the removal rate of heavy metals is not high.

[0011] US5073621A discloses a method for demetallization using water as a solubilizing agent. The method can preferably remove metals in the latex by first dissolving dicarboxylic acid in water and then adding it to the latex. However, this method is likely to cause emulsification of the latex, is disadvantageous for the reaction between the dicarboxylic acid and metal ions, affects the removal rate of metals, and the process is difficult to control.

[0012] CN1067898A discloses a method for removing residual metal catalysts after hydrogenation of polymers. This method involves adding hydrogen peroxide solution as an oxidizing agent and sebacic acid as a precipitating agent to a hydrogenated butadiene-styrene random copolymer latex. Sebacic acid is dissolved in a diethylene glycol-butyl ether aqueous solution to form a sebacic acid solution, which significantly improves the effect of removing metals in the latex. However, the sites of the two carboxyl groups of the dicarboxylic acid used in this method are not fixed, and the complexing effect on metals is poor, resulting in a low metal removal rate.

[0013] Conventional polymer deashing techniques have drawbacks such as a complex adsorbent preparation process, a long demetallization process, and low removal efficiency. Therefore, developing a novel polymer deashing method has become one of the urgent problems to be solved in this field.

Summary of the Invention

[0014] To solve the above technical problems, the present invention aims to provide a method for polymer deashing. This method has advantages such as high deashing efficiency, a simple process, and low cost.

[0015] To achieve the above object, the present invention Step (1): Mixing a polymer solution to be treated with one or a combination of multiple dicarboxylic acids and their derivatives and reacting them to obtain a mixed solution. Step (2): Washing the mixed solution with water, and the resulting oil phase is a polymer solution after deashing. including The dicarboxylic acid contains a carbon-carbon double bond, and the two carboxyl groups are arranged on the same side of the carbon-carbon double bond, with a cis structure in the spatial configuration. A method for polymer deashing is provided.

[0016] In the method for polymer deashing, preferably, the dicarboxylic acid has a structure represented by the following formula I.

Chemical formula

[0017] In the method for polymer deashing, preferably, the derivative of the dicarboxylic acid includes one or a combination of a plurality of types such as an acid anhydride, an acid halide, an amide, an ester, and a nitrile obtained from the dicarboxylic acid. More preferably, the derivative of the dicarboxylic acid includes an anhydride of the dicarboxylic acid.

[0018] In the method for polymer deashing, preferably, the acid anhydride of the dicarboxylic acid has a structure represented by the following formula II. [Chemical formula] (In formula II, R1 and R2 are the same or different, and R1 and R2 are each independently selected from an H atom, a linear or branched alkyl group having 1 to 10 carbon atoms. Preferably, R1 and R2 are the same or different, and R1 and R2 are each independently selected from an H atom, a linear or branched alkyl group having 1 to 5 carbon atoms.)

[0019] In the method for polymer deashing, preferably, the dicarboxylic acid and its derivative include one or a combination of a plurality of types such as cis-butenedioic acid (i.e., maleic acid), cis-butenedioic anhydride (i.e., maleic anhydride), cis-methylbutenedioic acid (i.e., 2-methylmaleic acid), cis-methylbutenedioic anhydride (i.e., 2-methylmaleic anhydride), 2,3-dimethylmaleic acid, and 2,3-dimethylmaleic anhydride.

[0020] The present invention provides a method for polymer deashing, particularly a method for removing residual catalyst metals in polymers (mainly polyolefins). This method employs dicarboxylic acids and their derivatives having a cis structure in the spatial arrangement as metal complexing agents. Such dicarboxylic acids and their derivatives react with metal ions in the polymer solution to form stable water-soluble metal complexes. Subsequently, the removal of the water-soluble metal complexes is completed by water washing, and the resulting oil phase is the polymer solution after deashing.

[0021] In some specific embodiments of the present invention, the structural formula of the metal complex formed from the dicarboxylic acid and its derivatives and metal ions is represented by the following formula III.

Chemical formula

[0022] In the method for polymer deashing, preferably, the solid content in the polymer solution to be treated is 5 to 50% (mass percentage), more preferably 10 to 40% (mass percentage).

[0023] In the method for polymer deashing, preferably, the polymer in the polymer solution to be treated can include one or a combination of multiple types such as cycloolefin copolymer (COC), cycloolefin polymer (COP), polyethylene, polypropylene, polyolefin plastomer (POP), and polyolefin elastomer (POE).

[0024] In the method for polymer deashing, preferably, the solvent in the polymer solution to be treated includes one or a combination of multiple types such as toluene, cyclohexane, and methylcyclohexane.

[0025] In some specific embodiments of the present invention, the polymer solution to be treated may be from a polymerization reaction unit in a polymer production process. Specifically, it can be from a polymerization reaction kettle in a solution polymerization process.

[0026] In the method for polymer deashing, preferably, the mixing ratio of the polymer solution to be treated and one or more combinations of the dicarboxylic acid and its derivatives is 1 g of polymer: 10 -3 ~10 -5 mol of one or more combinations of the dicarboxylic acid and its derivatives.

[0027] In the method for polymer deashing, preferably, one or more combinations of the dicarboxylic acid and its derivatives are mixed with the polymer solution to be treated as a solution, and the concentration of the solution of one or more combinations of the dicarboxylic acid and its derivatives is 0.1 - 10 mol / L, more preferably 0.1 - 5 mol / L.

[0028] In some specific embodiments of the present invention, the solvent in the solution of one or more combinations of the dicarboxylic acid and its derivatives may include one or more combinations such as water, alcohols, ketones, and hydrocarbons. Preferably, it includes one or more combinations such as water, ethanol, and acetone.

[0029] In the method for polymer deashing, preferably, in step (1), the process of mixing and reacting the polymer solution to be treated with one or more combinations of the dicarboxylic acid and its derivatives is carried out under stirring, and the rotation speed of the stirring can be adjusted by those skilled in the art according to the production scale. Preferably, vigorous stirring is adopted.

[0030] In the method for polymer deashing, preferably, in step (1), the temperature at which the polymer solution to be treated is mixed and reacted with one or more combinations of the dicarboxylic acid and its derivatives is 60 to 150 °C, more preferably 80 to 130 °C.

[0031] In the method for polymer deashing, preferably, in step (1), the reaction time between the polymer solution to be treated and one or more combinations of the dicarboxylic acid and its derivatives is 2 to 120 minutes, more preferably 5 to 60 minutes.

[0032] In the method for polymer deashing, preferably, in step (2), specifically, the mixture is subjected to oil-water separation, the obtained oil phase is washed with water, oil-water separation is performed after the water washing, and the obtained oil phase is the polymer solution after deashing.

[0033] In the method for polymer deashing, preferably, in step (2), the number of times of the water washing is 1 to 5 times, more preferably, the number of times of the water washing is 1 to 3 times.

[0034] In the method for polymer deashing, preferably, in step (2), the temperature of the water washing is 30 to 60 °C, and the volume ratio of the amount of water used for the water washing to the volume of the oil phase is 1 to 20:1. This amount of water used is the amount of water used for each water washing.

[0035] Those skilled in the art can understand that when performing multiple water washings, oil-water separation is performed after each water washing to obtain an oil phase. The water-soluble metal complex is in the water phase and is removed after the oil-water separation.

[0036] In some specific embodiments of the present invention, the oil-water separation can be performed using a general centrifuge.

[0037] According to a specific embodiment of the present invention, preferably, the method for polymer deashing further includes step (3) of mixing the polymer solution after deashing with alcohol to precipitate the polymer after deashing as a precipitate to obtain the polymer after deashing. More preferably, the alcohol used includes one or a combination of more than one of methanol, ethanol, propanol, isopropanol, etc., and even more preferably, the alcohol used is ethanol, etc. More preferably, the mixing volume ratio of the polymer solution after deashing to the alcohol is 1:(1 - 20). In some specific embodiments of the present invention, the alcohol used may be an alcohol solution, and its mass fraction or volume fraction may be generally adjusted by those skilled in the art.

[0038] In some specific embodiments of the present invention, step (3) may further include performing normal operations such as solid-liquid separation (such as filtration) and drying on the polymer after deashing precipitated as a precipitate to obtain the polymer after deashing.

[0039] The present invention provides a method for polymer deashing, in particular, a method for removing residual metals of the main catalyst and cocatalyst in a polymer (mainly polyolefin). The method of the present invention uses a dicarboxylic acid having a cis structure in its spatial arrangement and its derivatives as a metal complexing agent. Such a dicarboxylic acid having a cis structure and its derivatives form a cyclic transition state with metal ions in the polymer solution, and further form a more stable water-soluble metal complex. Then, the removal of the water-soluble metal complex is completed by washing with water, and the obtained oil phase is the polymer solution after deashing.

[0040] The method for polymer deashing of the present invention has at least the following beneficial technical effects: 1. The present invention uses dicarboxylic acids and their derivatives having a cis structure in the spatial arrangement as metal complexing agents, forms a cyclic transition state with metal ions, promotes the formation of metal complexes, and forms stable water-soluble metal complexes, thereby having the advantage of efficiently complexing and removing metals, and significantly improving the removal rate of metals in the polymer solution; 2. Since the present invention removes metal complexes by washing with water, it has the advantages of simple operation and low cost. Therefore, the method for polymer deashing of the present invention can efficiently remove metal ions remaining in the polymer solution, and can significantly reduce the residual metals in polymer products, especially polyolefin products. Compared with the conventional polymer deashing technology, the technical solution of the present invention has the advantages of high deashing efficiency, fast speed, simple process, and low cost, can be widely applied in the field of polymer metal removal, has versatility and efficiency, and has broad prospects for industrialization.

Embodiments for Carrying out the Invention

[0041] For a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the technical solution of the present invention will be described in detail below, but it should not be understood as limiting the scope of implementation of the present invention.

[0042] According to a specific embodiment of the present invention, preferably, the method for polymer deashing provided by the present invention includes the following steps.

[0043] Step (1): At 60 to 150 °C (preferably 80 to 130 °C), under intense stirring, add one or a combination of multiple kinds of dicarboxylic acids and their derivatives to the polymer solution to be treated, and react for 2 to 120 minutes (preferably 5 to 60 minutes) under intense stirring to form a water-soluble metal complex with one or a combination of multiple kinds of dicarboxylic acids and their derivatives and metal ions in the polymer solution to be treated, and obtain a mixed solution.

[0044] Here, the dicarboxylic acid has a structure represented by the following formula I. [Chemical formula] (In formula I, R1 and R2 are the same or different, and R1 and R2 are each independently selected from an H atom, a linear or branched alkyl group having 1 to 10 carbon atoms. Preferably, R1 and R2 are the same or different, and R1 and R2 are each independently selected from an H atom, a linear or branched alkyl group having 1 to 5 carbon atoms.)

[0045] The derivative of the dicarboxylic acid includes one or a combination of a plurality of acid anhydrides, acid halides, amides, esters, nitriles, etc. obtained from the dicarboxylic acid. Preferably, the derivative of the dicarboxylic acid includes the anhydride of the dicarboxylic acid, and the anhydride of the dicarboxylic acid has a structure shown in the following formula II. [Chemical formula] (In formula II, R1 and R2 are the same or different, and R1 and R2 are each independently selected from an H atom, a linear or branched alkyl group having 1 to 10 carbon atoms. Preferably, R1 and R2 are the same or different, and R1 and R2 are each independently selected from an H atom, a linear or branched alkyl group having 1 to 5 carbon atoms.)

[0046] The solid content in the polymer solution to be treated is 5 to 50% (mass percentage), preferably 10 to 40% (mass percentage). The polymer in the polymer solution to be treated can include one or a combination of a plurality of cycloolefin copolymers (COC), cycloolefin polymers (COP), polyethylene, polypropylene, polyolefin plastomers (POP), and polyolefin elastomers (POE), etc. The solvent in the polymer solution to be treated includes one or a combination of a plurality of toluene, cyclohexane, and methylcyclohexane, etc. The polymer solution to be treated may be from a polymerization reaction unit in a polymer production process, specifically, it may be from a polymerization reaction kettle in a solution polymerization process.

[0047] The mixing ratio of the polymer solution to be treated and one or more combinations of the dicarboxylic acid and its derivatives is 1 g of polymer: 10 -3 ~10 -5 mol of one or more combinations of the dicarboxylic acid and its derivatives.

[0048] One or more combinations of the dicarboxylic acid and its derivatives are mixed with the polymer solution to be treated as a solution, and the concentration of the solution of one or more combinations of the dicarboxylic acid and its derivatives is 0.1 to 10 mol / L, preferably 0.1 to 5 mol / L. The solvent in the solution of one or more combinations of the dicarboxylic acid and its derivatives may include one or more combinations of water, alcohols, ketones, and hydrocarbons, etc., and preferably includes one or more combinations of water, ethanol, and acetone, etc.

[0049] Step (2): After separating the oil and water of the mixture, the obtained oil phase is washed with water at 30 to 60 °C, the number of times of water washing is 1 to 5 times (preferably 1 to 3 times), and the volume ratio of the amount of water used for each water washing to the volume of the oil phase is 1 to 20:1. After each water washing, oil-water separation is performed, and the obtained oil phase is the polymer solution after deashing.

[0050] Step (3): Add the polymer solution after deashing to alcohol, precipitate the polymer after deashing as a precipitate, and obtain the polymer after deashing.

[0051] Here, the alcohol used includes one or more combinations of methanol, ethanol, propanol, isopropanol, etc., and preferably, the alcohol used is ethanol, etc. The mixing volume ratio of the polymer solution after deashing and the alcohol is 1:(1 to 20). The alcohol used may be an alcohol solution, and its mass fraction may be generally adjusted by those skilled in the art.

[0052] Example 1 This example provides a method for polymer deashing, which includes the following steps.

[0053] Step (1): Heat a 500 mL COC toluene solution with a solid content of 10% (mass percentage content) to 80 °C. Under intense stirring, add 5 mL of an aqueous maleic acid solution with a concentration of 0.1 mol / L. After continuously reacting for 5 minutes under intense stirring, maleic acid and metal ions in the COC toluene solution form a stable water-soluble metal complex to obtain a mixed solution.

[0054] Step (2): Use a centrifuge to separate the oil and water phases of the mixed solution. Wash the obtained oil phase with water at 30 °C. The number of water washing times is 3. The volume ratio of the water used for each water washing to the volume of the oil phase is 1:1. After each water washing, use a centrifuge to perform oil-water separation. Retain the oil phase after oil-water separation for the next water washing. The oil phase obtained after the third water washing and oil-water separation is the polymer solution after deashing, denoted as S1.

[0055] Step (3): Take 500 mL of the oil phase S1 and add it to 2000 mL of an ethanol solution with a volume fraction of 95% to precipitate the deashed polymer as a white precipitate. After filtering and drying the white precipitate, obtain a deashed polymer product, denoted as P1.

[0056] Perform long-term deashing on the COC toluene solution by the method of this example, and the long-term operation time is 600 hours.

[0057] Obtain an undashed polymer from the COC toluene solution through step (3) of this example, and measure its metal content by the ignition method, as shown in Table 1.

[0058] As a result of the measurement by the ignition method, the Zr content in the polymer product P1 is 0.02 ppm, and the Al content is 0.17 ppm.

[0059] The specific steps for measuring the metal content in the polymer by pyrolysis are common means in this field. The pyrolysis method adopted in the examples and comparative examples of the present invention is specifically as follows: Put 100 g of the unashed polymer or the polymer product after ash removal into a muffle furnace, heat it up to 650 °C in 1 hour by programmed temperature rise, then keep it at a constant temperature for 2 hours so that the polymer burns sufficiently, then cool it down to room temperature, add the ash remaining after pyrolysis to 5 mL of hydrochloric acid solution (the mass fraction of the hydrochloric acid solution was 19%), and after the ash was completely dissolved, analyze the metal content in the solution by ICP-MS.

[0060] Example 2 This example provides a method for polymer ash removal including the following steps.

[0061] Step (1): Heat a 500 mL COP cyclohexane solution with a solid content of 15% (mass percentage content) to 90 °C, add 15 mL of an ethanol solution of maleic anhydride with a concentration of 0.5 mol / L under intense stirring, and continue to react for 10 minutes under intense stirring. Then, maleic anhydride and metal ions in the COP cyclohexane solution form a stable water-soluble metal complex to obtain a mixed solution.

[0062] Step (2): Use a centrifuge to separate the oil and water of the mixed solution, wash the obtained oil phase with water at 40 °C, the number of water washings is 2 times, the volume ratio of the water used for each water washing to the volume of the oil phase is 5:1, perform oil-water separation using a centrifuge after each water washing, retain the oil phase after oil-water separation for the next water washing, and the oil phase obtained after the second water washing and oil-water separation is the polymer solution after ash removal, denoted as S2.

[0063] Step (3): Take 500 mL of the oil phase S2 and add it to 2000 mL of an ethanol solution with a volume fraction of 95% to precipitate the polymer after ash removal as a white precipitate. After filtering and drying the white precipitate, obtain the polymer product after ash removal, denoted as P2.

[0064] Using the method of this example, long-term deashing was performed on the COP cyclohexane solution, and the long-term operation time was 800 hours.

[0065] The COP cyclohexane solution was passed through step (3) of this example to obtain an undedusted polymer, and its metal content was measured by the ignition method and shown in Table 1.

[0066] As a result of the measurement by the ignition method, the Zr content in the polymer product P2 was 0.03 ppm, and the Al content was 0.25 ppm.

[0067] Example 3 This example provides a method for polymer deashing including the following steps.

[0068] Step (1): Heat a 500 mL COC methylcyclohexane solution with a solid content of 20% (mass percentage content) to 100 °C, add 100 mL of an acetone solution of cis-butenedioic acid with a concentration of 1 mol / L under vigorous stirring, and continue to react for 20 minutes under vigorous stirring. Then, cis-butenedioic acid and metal ions in the COC methylcyclohexane solution formed a stable water-soluble metal complex to obtain a mixed solution.

[0069] Step (2): Use a centrifuge to separate the oil and water of the mixed solution, wash the obtained oil phase with water at 50 °C, the number of water washings is 4 times, the volume ratio of the water used for each water washing to the volume of the oil phase is 10:1, perform oil-water separation using a centrifuge after each water washing, retain the oil phase after oil-water separation for the next water washing, and the oil phase obtained after the 4th water washing and oil-water separation is the deashed polymer solution, denoted as S3.

[0070] Step (3): Add 500 mL of the oil phase S3 to 2000 mL of an ethanol solution with a volume fraction of 95% to precipitate the deashed polymer as a white precipitate. After filtering and drying the white precipitate, obtain the deashed polymer product, denoted as P3.

[0071] The method of this example was used to perform long-term deashing on the COC methylcyclohexane solution, and the long-term operation time was 900 hours.

[0072] The COC methylcyclohexane solution was passed through step (3) of this example to obtain an undedusted polymer, and its metal content was measured by the ignition method and shown in Table 1.

[0073] As a result of the measurement by the ignition method, the Zr content in the polymer product P3 was 0.04 ppm, and the Al content was 0.27 ppm.

[0074] Example 4 This example provides a method for polymer deashing including the following steps.

[0075] Step (1): Heat a 500 mL COC toluene solution with a solid content of 25% (mass percentage content) to 110 °C, add 0.6 mL of an aqueous solution of 2-methylmaleic anhydride with a concentration of 2 mol / L under vigorous stirring, and continue to react for 30 minutes under vigorous stirring. Then, 2-methylmaleic anhydride and metal ions in the COC toluene solution formed a stable water-soluble metal complex to obtain a mixed solution.

[0076] Step (2): Use a centrifuge to separate the oil and water of the mixed solution, wash the obtained oil phase at 60 °C. The number of times of water washing is 1, and the volume ratio of the water used for water washing to the volume of the oil phase is 15:1. After water washing, perform oil-water separation by a centrifuge. The obtained oil phase is a polymer solution after deashing, denoted as S4.

[0077] Step (3): Take 500 mL of the oil phase S4 and add it to 2000 mL of an ethanol solution with a volume fraction of 95% to precipitate the polymer after deashing as a white precipitate. After filtering and drying the white precipitate, obtain a polymer product after deashing, denoted as P4.

[0078] The method of this example was used to perform long-term deashing on the COC toluene solution, and the long-term operation time was 1000 hours.

[0079] The COC toluene solution was processed through step (3) of this example to obtain an unash-ded polymer, and its metal content was measured by the ignition method and shown in Table 1.

[0080] As a result of the measurement by the ignition method, the Zr content in the polymer product P4 was 0.03 ppm and the Al content was 0.36 ppm.

[0081] Example 5 This example provides a method for polymer ash removal including the following steps.

[0082] Step (1): A 500 mL COC cyclohexane solution with a solid content of 30% (mass percentage content) was heated to 120 °C, and 5 mL of an ethanol solution of 2,3-dimethylmaleic anhydride with a concentration of 3 mol / L was added under vigorous stirring. Subsequently, after reacting for 40 minutes under vigorous stirring, 2,3-dimethylmaleic anhydride and metal ions in the COC cyclohexane solution formed a stable water-soluble metal complex to obtain a mixed solution.

[0083] Step (2): The above mixed solution was separated into oil and water using a centrifuge. The obtained oil phase was washed with water at 45 °C, and the number of water washing times was 5. The volume ratio of the water used for each water washing to the volume of the oil phase was 20:1. After each water washing, oil-water separation was performed using a centrifuge. After oil-water separation, the oil phase was retained for the next water washing. The oil phase obtained after the 5th water washing and oil-water separation was the polymer solution after ash removal, denoted as S5.

[0084] Step (3): 500 mL of the oil phase S5 was taken and added to 2000 mL of an ethanol solution with a volume fraction of 95% to precipitate the polymer after ash removal as a white precipitate. After filtering and drying the white precipitate, a polymer product after ash removal was obtained, denoted as P5.

[0085] Long-term ash removal was performed on the COC cyclohexane solution by the method of this example, and the long-term operation time was 1200 hours.

[0086] The COC cyclohexane solution was processed through step (3) of this example to obtain an undemineralized polymer, and its metal content was measured by the ignition method and shown in Table 1.

[0087] As a result of the measurement by the ignition method, the Zr content in the polymer product P5 was 0.04 ppm, and the Al content was 0.12 ppm.

[0088] Example 6 This example provides a method for polymer demineralization including the following steps.

[0089] Step (1): A 500 mL COC methylcyclohexane solution with a solid content of 40% (mass percentage content) was heated to 130 °C, and 40 mL of an acetone solution of 2,3-dimethylmaleic anhydride with a concentration of 5 mol / L was added under vigorous stirring. Subsequently, after reacting for 60 minutes under vigorous stirring, 2,3-dimethylmaleic anhydride and metal ions in the COC methylcyclohexane solution formed a stable water-soluble metal complex to obtain a mixed solution.

[0090] Step (2): The above mixed solution was separated into oil and water using a centrifuge. The obtained oil phase was washed with water at 55 °C, and the number of water washings was 3 times. The volume ratio of the water used for each water washing to the volume of the oil phase was 3:1. After each water washing, oil-water separation was performed using a centrifuge, and the oil phase was retained after oil-water separation for the next water washing. The oil phase obtained after the third water washing and oil-water separation was a demineralized polymer solution, denoted as S6.

[0091] Step (3): 500 mL of the oil phase S6 was taken and added to 2000 mL of an ethanol solution with a volume fraction of 95% to precipitate the demineralized polymer as a white precipitate. After filtering and drying the white precipitate, a demineralized polymer product was obtained, denoted as P6.

[0092] Long-term demineralization was performed on the COC methylcyclohexane solution by the method of this example, and the long-term operation time was 1500 hours.

[0093] The COC methylcyclohexane solution was processed through step (3) of this example to obtain an unashlar polymer, and its metal content was measured by the ignition method and shown in Table 1.

[0094] As a result of the measurement by the ignition method, the Zr content in the polymer product P6 was 0.03 ppm, and the Al content was 0.35 ppm.

[0095] Comparative Example 1 This comparative example provides a method for polymer ash removal including the following steps.

[0096] Step (1): 500 mL of a COC toluene solution with a solid content of 10% (mass percentage content) (the same as in Example 1) was heated to 80°C, and 5 mL of an aqueous adipic acid solution with a concentration of 0.1 mol / L was added under vigorous stirring. After continuously reacting for 5 minutes under vigorous stirring, a mixed solution was obtained.

[0097] Step (2): The above mixed solution was separated into oil and water using a centrifuge. The obtained oil phase was washed with water at 30°C, and the number of water washing times was 3. The volume ratio of the water used for each water washing to the volume of the oil phase was 1:1. After each water washing, oil-water separation was performed using a centrifuge, and the oil phase was retained after oil-water separation for the next water washing. The oil phase obtained after the third water washing and oil-water separation was the polymer solution after ash removal, denoted as S7.

[0098] Step (3): 500 mL of the oil phase S7 was taken and added to 2000 mL of an ethanol solution with a volume fraction of 95%. The polymer after ash removal was precipitated as a white precipitate. After filtering and drying the white precipitate, a polymer product after ash removal was obtained, denoted as P7.

[0099] Long-term ash removal was performed on the COC toluene solution by the method of this comparative example, and the long-term operation time was 600 hours.

[0100] As a result of the measurement by the ignition method, the Zr content in the polymer product P7 was 1.9 ppm, and the Al content was 16 ppm.

[0101] Comparative Example 2 This comparative example provides a method for polymer deashing comprising the following steps.

[0102] Step (1): 500 mL of a COC toluene solution with a solid content of 10% (mass percentage content) (the same as in Example 1) was heated to 80 °C, and 5 mL of an aqueous citric acid solution with a concentration of 0.1 mol / L was added under intense stirring. Subsequently, after reacting for 5 minutes under intense stirring, a mixed solution was obtained.

[0103] Step (2): The mixed solution was separated into oil and water using a centrifuge. The obtained oil phase was washed with water at 30 °C, and the number of water washing times was 3. The volume ratio of the water used for each water washing to the volume of the oil phase was 1:1. After each water washing, oil-water separation was performed using a centrifuge, and the oil phase was retained for the next water washing. The oil phase obtained after the third water washing and oil-water separation was the deashed polymer solution, denoted as S8.

[0104] Step (3): 500 mL of the oil phase S8 was taken and added to 2000 mL of an ethanol solution with a volume fraction of 95%. The deashed polymer was precipitated as a white precipitate. After filtering and drying the white precipitate, a deashed polymer product was obtained, denoted as P8.

[0105] Long-term deashing was performed on the COC toluene solution by the method of this comparative example, and the long-term operation time was 600 hours.

[0106] As a result of measurement by the ignition method, the Zr content in the polymer product P8 was 2.4 ppm, and the Al content was 17 ppm.

[0107] Comparative Example 3 This comparative example provides a method for polymer deashing comprising the following steps.

[0108] Step (1): Take 250 mL of the powdered aluminum oxide used in Step (2) of Example 1, heat it to 100 °C, then add 100 mL of a maleic acid aqueous solution with a concentration of 0.005 mol / L, continue to stir for 2 hours, then filter, take the filter residue, dry it at 120 °C for 8 hours to obtain aluminum oxide powder pretreated with maleic acid. The bulk density of the aluminum oxide powder pretreated with maleic acid is 0.41 g / mL, the specific surface area is 212 m 2 / g, and the pore volume is 0.42 mL / g.

[0109] Step (2): Heat 500 mL of a COC toluene solution with a solid content of 10% (mass percentage content) to 50 °C (the same as in Example 1), and at a temperature and pressure of 50 °C and 0.2 MPa, pass it through an adsorption column filled with the alumina powder pretreated with maleic acid at a volumetric space velocity of 0.5 h -1 for adsorption separation. The obtained filtrate is the polymer solution after ash removal, denoted as S9.

[0110] Step (3): Take 500 mL of the filtrate S9 and add it to 2000 mL of an ethanol solution with a volume fraction of 95% to precipitate the polymer after ash removal as a white precipitate. After filtering and drying the white precipitate, a polymer product after ash removal is obtained, denoted as P9.

[0111] Long-term ash removal was performed on the COC toluene solution by the method of this comparative example, and the long-term operation time was 600 hours, and the adsorbent was not replaced during the operation.

[0112] As a result of measurement by the ignition method, the Zr content in the polymer product P9 was 4.8 ppm, and the Al content was 38 ppm.

[0113] Comparative Example 4 This comparative example provides a method for polymer ash removal including the following steps.

[0114] Step (1): 500 mL of a COC toluene solution with a solid content of 10% (mass percentage content) (the same as in Example 1) was heated to 80 °C, and 5 mL of an aqueous fumaric acid solution with a concentration of 0.1 mol / L was added under vigorous stirring. Subsequently, after reacting for 5 minutes under vigorous stirring, a mixed solution was obtained.

[0115] Step (2): The above-mentioned mixed solution was separated into oil and water using a centrifuge. The obtained oil phase was washed with water at 30 °C, and the number of water washings was 3 times. The volume ratio of the water used for each water washing to the volume of the oil phase was 1:1. After each water washing, oil-water separation was performed using a centrifuge. After oil-water separation, the oil phase was retained for the next water washing. The oil phase obtained after the third water washing and oil-water separation was a polymer solution after ash removal, denoted as S10.

[0116] Step (3): 500 mL of the oil phase S10 was taken and added to 2000 mL of an ethanol solution with a volume fraction of 95%. The polymer after ash removal was precipitated as a white precipitate. After filtering and drying the white precipitate, a polymer product after ash removal was obtained, denoted as P10.

[0117] Long-term ash removal was performed on the COC toluene solution by the method of this comparative example, and the long-term operation time was 600 hours.

[0118] As a result of measurement by the strong heating method, the Zr content in the polymer product P10 was 5.1 ppm, and the Al content was 24.2 ppm.

[0119] The results of the polymer ash removal methods provided in the above Examples 1 to 6 and Comparative Examples 1 to 4 are shown in Table 1.

[0120]

Table 1

[0121] As can be seen from the experimental results in Table 1, the polymer deashing methods of Examples 1 to 6 of the present invention have a remarkable effect of removing metals in the polymer, and the removal efficiency is clearly superior to that of Comparative Examples 1 to 4. Moreover, the polymer deashing method of the present invention is simple to operate, has low costs, and has broad prospects for industrialization in the future.

Claims

1. A method for polymer deashing, comprising: Step (1): reacting a polymer solution to be treated by mixing it with one or more combinations of dicarboxylic acids and their derivatives to obtain a mixed solution; Step (2): washing the mixed solution with water, wherein the obtained oil phase is the polymer solution after deashing; and the dicarboxylic acid contains a carbon-carbon double bond, and two carboxyl groups are arranged on the same side of the carbon-carbon double bond, and has a cis structure in the spatial arrangement. A method for polymer deashing.

2. The method for polymer deashing according to claim 1, wherein the dicarboxylic acid has a structure represented by the following formula I. 【Chemical 1】 (In formula I, R １ , R ２ are the same or different, and R １ and R ２ are each independently selected from an H atom, a linear or branched alkyl group having 1 to 10 carbon atoms)

3. In formula I, R １ , R ２ are the same or different, and R １ and R ２ are each independently selected from an H atom, a linear or branched alkyl group having 1 to 5 carbon atoms. The method for polymer deashing according to claim 2.

4. The method for polymer deashing according to claim 1, wherein the derivative of the dicarboxylic acid includes one or more combinations of an acid anhydride, an acid halide, an amide, an ester, and a nitrile obtained from the dicarboxylic acid.

5. The method for polymer deashing according to claim 4, wherein the derivative of the dicarboxylic acid includes a dicarboxylic acid anhydride, and the dicarboxylic acid anhydride has a structure represented by the following formula II. 【Chemical Formula 2】 (In formula II, R １ , R ２ are the same or different, and R １ and R ２ are each independently selected from an H atom, a linear or branched alkyl group having 1 to 10 carbon atoms)

6. In formula II, R １ , R ２ are the same or different, and R １ and R ２ are each independently selected from an H atom, a linear or branched alkyl group having 1 to 5 carbon atoms. The method for polymer ash removal according to claim 5.

7. The method for polymer deashing according to claim 1, wherein the dicarboxylic acid and its derivatives include one or more combinations of cis-butenedioic acid, cis-butenedioic anhydride, cis-methylbutenedioic acid, cis-methylbutenedioic anhydride, 2,3-dimethylmaleic acid, and 2,3-dimethylmaleic anhydride.

8. The method for polymer deashing according to claim 1, wherein the solid content in the polymer solution to be treated is 5 to 50%.

9. The method for polymer deashing according to claim 1, wherein the polymer in the polymer solution to be treated includes one or more combinations of a cycloolefin copolymer, a cycloolefin polymer, polyethylene, polypropylene, a polyolefin plastomer, and a polyolefin elastomer.

10. The mixing ratio of the polymer solution to be treated and one or a combination of two or more of the dicarboxylic acids and their derivatives is 1 g of polymer: 10 －３ to 10 －５ mol of one or a combination of two or more of the dicarboxylic acids and their derivatives. The method for polymer deashing according to claim 1.

11. The method for polymer deashing according to claim 1, wherein one or more combinations of the dicarboxylic acid and its derivatives are mixed with the polymer solution to be treated as a solution, and the concentration of the solution of one or more combinations of the dicarboxylic acid and its derivatives is 0.1 to 10 mol / L.

12. The solvent in the solution of one or more combinations of the dicarboxylic acid and its derivatives includes one or more combinations of water, alcohols, ketones, and hydrocarbons. The method for polymer deashing according to claim 11.

13. In step (1), the temperature at which the polymer solution to be treated is mixed and reacted with one or more combinations of the dicarboxylic acid and its derivatives is 60 to 150 °C. The method for polymer deashing according to claim 1.

14. In step (1), the temperature at which the polymer solution to be treated is mixed and reacted with one or more combinations of the dicarboxylic acid and its derivatives is 80 to 130 °C. The method for polymer deashing according to claim 13.

15. In step (1), the reaction time between the polymer solution to be treated and one or more combinations of the dicarboxylic acid and its derivatives is 2 to 120 minutes. The method for polymer deashing according to claim 1.

16. In step (1), the reaction time between the polymer solution to be treated and one or more combinations of the dicarboxylic acid and its derivatives is 5 to 60 minutes. The method for polymer deashing according to claim 15.

17. Step (2) specifically includes separating the oil and water of the mixed solution, washing the obtained oil phase with water, performing oil-water separation after washing, and the obtained oil phase being the polymer solution after deashing. The method for polymer deashing according to claim 1.

18. In step (2), the number of times of the water washing is 1 to 5 times. The method for polymer deashing according to claim 1.

19. In step (2), the temperature of the water washing is 30 to 60 °C, and the volume ratio of the amount of water used for the water washing to the volume of the oil phase is 1 to 20:

1. The method for polymer deashing according to claim 17.

20. The method for polymer deashing according to claim 1 further includes step (3) of mixing the polymer solution after deashing with alcohol, precipitating the polymer after deashing, and obtaining the polymer after deashing.

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