A method for polymer deashing

Abstract

The present invention provides a method for polymer deashing. The method comprises the following steps: after mixing and reacting a polymer solution to be treated with one or a combination of several of dicarboxylic acids and their derivatives, a mixed solution is obtained; the mixed solution is washed with water, and the obtained oil phase is the deashed polymer solution; wherein, 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 terms of spatial configuration. The method of the present invention uses dicarboxylic acids and their derivatives having a cis structure in terms of spatial configuration as metal complexing reagents, which form stable metal complexes after reacting with metal ions in the polymer solution, and has the advantages of high-efficiency metal complexing and removal, and can significantly improve the metal removal rate of the polymer solution. The method of the present invention has the advantages of high deashing efficiency, simple process, low cost, etc., and has broad industrialization prospects.

Description

Technical Field

[0001] The present invention relates to a method for polymer deashing, belonging to the technical field of polymer deashing. Background Art

[0002] As a functional polyolefin material, the copolymer of ethylene with α-olefins and cycloolefins has excellent mechanical strength, machining properties, and excellent chemical corrosion resistance. At the same time, its optical properties, gas barrier properties, chemical resistance, light resistance, etc. are excellent, and it plays an irreplaceable role in industry, agriculture, national defense, transportation, and people's daily lives, with broad application prospects.

[0003] Currently, the industry mostly uses highly efficient metallocene olefin polymerization catalyst systems for the production of polyolefin products. Generally, metallocene catalysts contain elements of Groups IVB, VB, and VIB of the periodic table, especially vanadium, titanium, and zirconium. The cocatalysts mainly contain elements such as aluminum. These catalysts are usually called transition metal catalysts, and they have high olefin polymerization catalytic activity. However, once the polymerization is completed, the metals in the catalysts remain in the polyolefin products, which will have a negative impact on the appearance, dielectric properties, optical properties, medical material properties, etc. of the end products. Therefore, for polyolefin products, especially high-end polyolefin products such as medical grade and optical grade, how to efficiently remove metal residues (referred to as deashing) is of top priority.

[0004] The commonly used deashing methods in the polymer industrialization process mainly include aqueous phase extraction method, coagulation sedimentation method, and complexation adsorption method. Among them, the complexation adsorption method is the most commonly used deashing method in polymer industrial production, with the advantages of simple process, large adsorption capacity, high deashing efficiency, few interference factors, and good stability. Complexing agents are roughly divided into inorganic and organic categories. Among them, inorganic complexing agents are usually easily decomposed at high temperatures and are only applicable to alkaline media, with limited application scope. Although organic complexing agents have a wider application range, it is usually difficult to reduce the metal content in the polymer solution to below 10 ppm. In addition, in the industrialization process, supported adsorbent fillers are often used for complexation deashing. This type of adsorbent is a solid filler obtained by impregnating and calcining an alumina carrier and a complexing agent material, and the effective loading amount of the complexing agent is low, which is subject to certain limitations in application.

[0005] US4992529A discloses a method for removing metals with a mixed acid. The characteristic of this method is that a monocarboxylic acid reacts with metals in the organic phase to form carboxylates insoluble in the organic phase. These carboxylates react with the inorganic acids in the mixed acid to form inorganic salts soluble in the aqueous phase, and the carboxylic acid is reduced and returns to the organic phase, then reacts with the metals in the polymer solution to form carboxylates. This cycle continues until all the metals in the polymer solution are completely transferred to the aqueous phase, thus achieving the removal of metal residues. Here, the carboxylic acid acts as a phase transfer catalyst. The idea of this method is relatively novel, but the removal effect is not ideal, and a large amount of water is also required.

[0006] CN114534694A discloses a complexing adsorption filler, its preparation method and application. The adsorption filler is a molecular sieve filler loaded with a hydroxyquinoline compound, and an organic acid can be loaded on the molecular sieve loaded with the hydroxyquinoline compound. This adsorption filler can effectively remove the residual catalyst in the polyolefin solution, and has the advantages of fast deashing speed, large adsorption capacity, and low pressure drop, etc., and is suitable for the removal of catalysts in various olefin solution polymerization processes. However, the preparation process of this adsorption filler is complex and cumbersome, and at the same time, the loading amount of hydroxyquinoline is relatively low, resulting in a low adsorption capacity of the adsorption filler and a high operating cost.

[0007] CN114989331A discloses a method for complexing deashing of a polyolefin solution. This method includes the following steps: 1) adding diminazene to the polyolefin solution to complex and adsorb metal ions in the solution to form a complex; 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. This deashing method can efficiently remove the residual metals in the polyolefin solution, has a simple process, low swelling of the filler, low system pressure drop, and a long service life of the deashing filler and a long replacement cycle of the adsorption column, and can significantly save the treatment cost. However, due to the general complexing ability of diminazene to metals, the metal removal rate is relatively low, especially the content of metal aluminum in the polymer is relatively high.

[0008] CN102875702A discloses a method for removing metals from a polymer. This method uses adding an organic base, such as n-butyllithium, phenyllithium, etc., to the glue solution, then adding an oxidant, washing with water after the reaction, and finally centrifuging to achieve the purpose of removing metal residues in the glue solution. Although this method has a relatively high efficiency in removing metal residues from the polymer, since organic bases are used, some metal ions are introduced, resulting in higher raw material input and the cost of removing residual catalysts, and the requirements for equipment by the externally added organic bases are high.

[0009] CN114392724A discloses a special deashing adsorbent for polyolefins, its preparation method and application. The deashing adsorbent is prepared by using pyridine-3-carboxylic acid as a complexing agent and loading it on an oxide carrier. The deashing adsorbent can efficiently remove residual metals in polyolefin solutions, significantly reduce the metal residues in polyolefin products, and has the advantages of fast deashing rate, large adsorption capacity, low swelling, and low solution pressure drop compared with traditional chelating adsorption methods. However, the preparation process of the deashing adsorbent is complex and cumbersome, and the loading amount of pyridine-3-carboxylic acid is relatively low, resulting in a low adsorption capacity of the adsorbent and high operating costs.

[0010] CN113856637A discloses a method for removing metal residues in the production process of COC and COP by using a complexing adsorption filler. Compared with traditional adsorption resins, the adsorption filler has the advantages of fast metal deashing speed and large adsorption capacity, and there is no swelling phenomenon at the same time. The adsorption filler is prepared by the following method: reacting silica solid, solvent, and phosphorus tribromide in proportion to prepare brominated silica solid, and then reacting with an appropriate amount of diethyl iminodiacetate to obtain a yellow solid, which is acidified with hydrochloric acid to obtain the adsorption filler. The preparation process of the adsorption filler is cumbersome and complex, and the heavy metal removal rate is not high.

[0011] US5073621A discloses a method for demetallization using water as a solubilizer. The method first dissolves a dicarboxylic acid in water and then adds it to the glue solution, which can better remove metals in the glue solution. However, this method is prone to cause emulsification of the glue solution, which is not conducive to the reaction between the dicarboxylic acid and metal ions, affects the metal removal rate, and the process is difficult to control.

[0012] CN1067898A discloses a method for removing residual metal catalysts after polymer hydrogenation. In this method, hydrogen peroxide is added as an oxidant and sebacic acid is added as a precipitant in a hydrogenated butadiene-styrene random copolymer glue solution. Sebacic acid is dissolved in a diethylene glycol-butyl ether aqueous solution to form a sebacic acid solution, which greatly improves the metal removal effect in the glue solution. However, the positions 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] Existing polymer deashing technologies have deficiencies such as cumbersome preparation processes of adsorbents, long metal removal process flows, and low removal efficiency. Therefore, developing a new 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 purpose of the present invention is to provide a polymer deashing method. This method has the advantages of high deashing efficiency, simple process, and low cost.

[0015] To achieve the above object, the present invention provides a method for polymer deashing, which comprises the following steps:

[0016] (1) Mixing and reacting a polymer solution to be treated with one or a combination of several of dicarboxylic acids and their derivatives to obtain a mixed solution;

[0017] (2) Washing the mixed solution, and the obtained oil phase is the deashed polymer solution;

[0018] Wherein, 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 configuration.

[0019] In the above method for polymer deashing, preferably, the dicarboxylic acid has the structure shown in the following formula I:

[0020]

[0021] In formula I, R 1 , R 2 are the same or different, and R 1 and R 2 each independently selected from H atom, a linear or branched alkyl group having 1 to 10 carbon atoms; preferably, R 1 , R 2 are the same or different, and R 1 and R 2 each independently selected from H atom, a linear or branched alkyl group having 1 to 5 carbon atoms.

[0022] In the above method for polymer deashing, preferably, the derivatives of the dicarboxylic acid include one or a combination of several of acid anhydrides, acyl halides, amides, esters, nitriles, etc. formed by the dicarboxylic acid. More preferably, the derivatives of the dicarboxylic acid include acid anhydrides of the dicarboxylic acid.

[0023] In the above method for polymer deashing, preferably, the acid anhydride of the dicarboxylic acid has the structure shown in the following formula II:

[0024]

[0025] In formula II, R 1 , R 2 are the same or different, and R 1 and R 2 each independently selected from H atom, a linear or branched alkyl group having 1 to 10 carbon atoms; preferably, R 1 , R 2 are the same or different, and R 1 and R 2 each independently selected from H atom, a linear or branched alkyl group having 1 to 5 carbon atoms.

[0026] In the above method for polymer deashing, preferably, the dicarboxylic acid and its derivatives include one or a combination of several of maleic acid (i.e., cis-butenedioic acid), maleic anhydride, cis-methylbutenedioic acid (i.e., 2-methylmaleic acid), cis-methylbutenedioic anhydride (i.e., 2-methylmaleic anhydride), 2,3-dimethylmaleic acid, 2,3-dimethylmaleic anhydride, etc.

[0027] The present invention provides a method for polymer deashing, especially a method for removing residual metals of catalysts in polymers (mainly polyolefins). This method uses a dicarboxylic acid and its derivatives with a cis structure in the spatial configuration as a metal complexing reagent. After reacting with metal ions in the polymer solution, this dicarboxylic acid and its derivatives with a cis structure form a stable water-soluble metal complex, and then the water-soluble metal complex is removed by water washing, and the obtained oil phase is the deashed polymer solution.

[0028] In some specific embodiments of the present invention, the structural formula of the metal complex formed by the dicarboxylic acid and its derivatives and metal ions is as shown in Formula III below:

[0029]

[0030] In Formula III, R 1 and R 2 are the same or different, and R 1 and R 2 each independently selected from an H atom, a straight-chain or branched-chain alkyl group having 1 to 10 carbon atoms, and M is a metal ion; preferably, R 1 and R 2 are the same or different, and R 1 and R 2 each independently selected from an H atom, a straight-chain or branched-chain alkyl group having 1 to 5 carbon atoms, and M is a metal ion.

[0031] In the above method for polymer deashing, preferably, the solid content in the polymer solution to be treated is 5% - 50% (mass percentage), more preferably 10% - 40% (mass percentage).

[0032] In the above method for polymer deashing, preferably, the polymer in the polymer solution to be treated may include one or a combination of several of cycloolefin copolymer (COC), cycloolefin polymer (COP), polyethylene, polypropylene, polyolefin plastomer (POP), polyolefin elastomer (POE), etc.

[0033] In the above method for polymer deashing, preferably, the solvent in the polymer solution to be treated includes one or a combination of several of toluene, cyclohexane, methylcyclohexane, etc.

[0034] In some specific embodiments of the present invention, the polymer solution to be treated can be from the polymerization reaction unit in the polymer production process. Specifically, it can be from the polymerization reaction kettle in the solution polymerization process.

[0035] In the above method for polymer deashing, preferably, the mixing ratio of the polymer solution to be treated and the combination of one or more of the dicarboxylic acids and their derivatives is 1 g of polymer: 10 -3 -10 -5 mol of the combination of one or more of the dicarboxylic acids and their derivatives.

[0036] In the above method for polymer deashing, preferably, the combination of one or more of the dicarboxylic acids and their derivatives is mixed with the polymer solution to be treated in the form of a solution. The concentration of the solution of the combination of one or more of the dicarboxylic acids and their derivatives is 0.1 - 10 mol / L, more preferably 0.1 - 5 mol / L.

[0037] In some specific embodiments of the present invention, the solvent in the solution of the combination of one or more of the dicarboxylic acids and their derivatives can include one or more combinations of water, alcohols, ketones, and hydrocarbons, etc. Preferably, it includes one or more combinations of water, ethanol, and acetone, etc.

[0038] In the above method for polymer deashing, preferably, in step (1), the process of mixing and reacting the polymer solution to be treated and the combination of one or more of the dicarboxylic acids and their derivatives is carried out under stirring conditions. The rotation speed of the stirring can be adjusted by those skilled in the art according to the production scale, and preferably vigorous stirring is adopted.

[0039] In the above method for polymer deashing, preferably, in step (1), the temperature of the mixing and reaction of the polymer solution to be treated and the combination of one or more of the dicarboxylic acids and their derivatives is 60 - 150 °C, more preferably 80 - 130 °C.

[0040] In the above method for polymer deashing, preferably, in step (1), the reaction time of the polymer solution to be treated and the combination of one or more of the dicarboxylic acids and their derivatives is 2 - 120 minutes, more preferably 5 - 60 minutes.

[0041] In the above method for polymer deashing, preferably, step (2) specifically includes: separating the oil and water of the mixture, washing the obtained oil phase, separating the oil and water after washing, and the obtained oil phase is the deashed polymer solution.

[0042] In the above method for polymer deashing, preferably, in step (2), the number of water washing times is 1 - 5 times; more preferably, the number of water washing times is 1 - 3 times.

[0043] In the above method for polymer deashing, preferably, in step (2), the temperature of the water washing is 30 - 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 - 20:1. The amount of water used is the amount of water used for each water washing.

[0044] Those skilled in the art can understand that when multiple water washings are carried out, oil - water separation is carried out after each water washing to obtain the oil phase. The water - soluble metal complex is in the water phase and is removed after the oil - water separation.

[0045] In some specific embodiments of the present invention, the oil - water separation can be carried out using a conventional centrifugal separator.

[0046] According to the specific embodiments of the present invention, preferably, the above method for polymer deashing further includes step (3): mixing the deashed polymer solution with an alcohol so that the deashed polymer precipitates out to obtain the deashed polymer. More preferably, the alcohol used includes one or a combination of several of methanol, ethanol, propanol, isopropanol, etc.; further preferably, the alcohol used is ethanol, etc. More preferably, the mixing volume ratio of the deashed polymer solution to the alcohol is 1:(1 - 20). In some specific embodiments of the present invention, the alcohol used can be an alcohol solution, and its mass fraction or volume fraction can be conventionally adjusted by those skilled in the art.

[0047] In some specific embodiments of the present invention, step (3) can further include: subjecting the deashed polymer precipitated in the form of a precipitate to conventional operations such as solid - liquid separation (such as filtration), drying, etc. to obtain the deashed polymer.

[0048] The present invention provides a method for polymer deashing, especially 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 and its derivatives having a cis - structure in the spatial configuration as a metal complexing reagent. This dicarboxylic acid and its derivatives having a cis - structure can form a cyclic transition state with metal ions in the polymer solution, and then form a stable water - soluble metal complex. Then, the water - soluble metal complex is removed by water washing, and the obtained oil phase is the deashed polymer solution.

[0049] The method for deashing polymers of the present invention has at least the following beneficial technical effects: 1. The present invention uses a dicarboxylic acid and its derivatives with a cis structure in the spatial configuration as metal complexing reagents, which can form a cyclic transition state with metal ions, promote the formation of metal complexes, and form stable water-soluble metal complexes, having the advantages of high-efficiency metal complexation and metal removal, and significantly improving the metal removal rate of polymer solutions; 2. The present invention uses water washing to remove metal complexes, having the advantages of simple operation and low cost. Therefore, the method for deashing polymers of the present invention can efficiently remove residual metal ions in polymer solutions, and significantly reduce the metal residues in polymer products, especially polyolefin products. Compared with traditional polymer deashing technologies, 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 to the field of polymer metal removal, has universality and high efficiency, and has broad industrialization prospects. Detailed implementation modes

[0050] 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 construed as a limitation on the scope of implementation of the present invention.

[0051] According to the specific implementation mode of the present invention, preferably, the method for deashing polymers provided by the present invention includes the following steps:

[0052] (1) Under the conditions of 60 - 150 °C (preferably 80 - 130 °C) and vigorous stirring, one or a combination of several of dicarboxylic acids and their derivatives is added to the polymer solution to be treated, and the reaction is carried out for 2 - 120 minutes (preferably 5 - 60 minutes) under the condition of vigorous stirring. One or a combination of several of dicarboxylic acids and their derivatives forms a water-soluble metal complex with metal ions in the polymer solution to be treated, obtaining a mixed solution;

[0053] Among them, the dicarboxylic acid has the structure shown in the following formula I:

[0054]

[0055] In formula I, R 1 and R 2 are the same or different, and R 1 and R 2 each independently selected from an H atom, a straight-chain or branched-chain alkyl group with 1 - 10 carbon atoms; preferably, R 1 and R 2 are the same or different, and R 1 and R 2 each independently selected from an H atom, a straight-chain or branched-chain alkyl group with 1 - 5 carbon atoms;

[0056] The derivatives of the dicarboxylic acid include one or a combination of several of the acid anhydrides, acyl halides, amides, esters, nitriles, etc. formed by the dicarboxylic acid; preferably, the derivatives of the dicarboxylic acid include the acid anhydride of the dicarboxylic acid; the acid anhydride of the dicarboxylic acid has the structure shown in Formula II below:

[0057]

[0058] In Formula II, R 1 , R 2 are the same or different, and R 1 and R 2 each independently selected from an H atom, a straight-chain or branched-chain alkyl group having 1 to 10 carbon atoms; preferably, R 1 , R 2 are the same or different, and R 1 and R 2 each independently selected from an H atom, a straight-chain or branched-chain alkyl group having 1 to 5 carbon atoms;

[0059] The solid content in the polymer solution to be treated is 5% - 50% (mass percentage), preferably 10% - 40% (mass percentage); the polymer in the polymer solution to be treated may include one or a combination of several of cycloolefin copolymer (COC), cycloolefin polymer (COP), polyethylene, polypropylene, polyolefin plastomer (POP), polyolefin elastomer (POE), etc.; the solvent in the polymer solution to be treated includes one or a combination of several of toluene, cyclohexane, methylcyclohexane, etc.; the polymer solution to be treated may come from the polymerization reaction unit in the polymer production process, specifically, it may come from the polymerization reaction kettle in the solution polymerization process;

[0060] The mixing ratio of the polymer solution to be treated and one or a combination of several of the dicarboxylic acid and its derivatives is 1 g of polymer: 10 -3 -10 -5 mol of one or a combination of several of the dicarboxylic acid and its derivatives;

[0061] One or a combination of several of the dicarboxylic acid and its derivatives is mixed with the polymer solution to be treated in the form of a solution, and the concentration of the solution of one or a combination of several of the dicarboxylic acid and its derivatives is 0.1 - 10 mol / L, preferably 0.1 - 5 mol / L; the solvent in the solution of one or a combination of several of the dicarboxylic acid and its derivatives may include one or a combination of several of water, alcohols, ketones, hydrocarbons, etc., preferably including one or a combination of several of water, ethanol, and acetone;

[0062] (2) After separating the oil and water of the said mixed liquid, subject the obtained oil phase to water washing at 30 - 60°C, and the number of water washing times is 1 - 5 times (preferably 1 - 3 times). The volume ratio of the water consumption for each water washing to the volume of the oil phase is 1 - 20:1. After each water washing, separate the oil and water again, and the obtained oil phase is the polymer solution after deashing;

[0063] (3) Add the polymer solution after deashing to alcohol, so that the polymer after deashing precipitates out in the form of a precipitate to obtain the polymer after deashing;

[0064] Among them, the alcohol used includes one or a combination of several of methanol, ethanol, propanol, isopropanol, etc.; preferably, the alcohol used is ethanol, etc.; the mixing volume ratio of the polymer solution after deashing to the alcohol is 1:(1 - 20); the alcohol used can be an alcohol solution, and its mass fraction can be adjusted conventionally by those skilled in the art.

[0065] Example 1

[0066] This example provides a method for deashing a polymer, which includes the following steps:

[0067] (1) Heat 500 mL of a COC toluene solution with a solid content of 10% (mass percentage) to 80°C, add 5 mL of an aqueous maleic acid solution with a concentration of 0.1 mol / L under vigorous stirring conditions, and continue to react for 5 minutes under vigorous stirring conditions. Then, maleic acid forms a stable water-soluble metal complex with metal ions in the COC toluene solution to obtain a mixed liquid;

[0068] (2) Use a centrifugal separator to separate the oil and water of the said mixed liquid, subject the obtained oil phase to water washing at 30°C, and the number of water washing times is 3 times. The volume ratio of the water consumption for each water washing to the volume of the oil phase is 1:1. After each water washing, use a centrifugal separator to separate the oil and water again. After separating the oil and water, retain the oil phase for the next water washing. The oil phase obtained after the 3rd water washing and oil-water separation is the polymer solution after deashing, and this oil phase is denoted as S1;

[0069] (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%, so that the polymer after deashing precipitates out in the form of a white precipitate. After filtering and drying the said white precipitate, obtain the polymer product after deashing, denoted as P1.

[0070] Use the method of this example to conduct long-term deashing on the COC toluene solution, and the long-term operation time is 600 hours.

[0071] Obtain the polymer without deashing 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.

[0072] The Zr content in the polymer product P1 measured by the ignition method is 0.02 ppm, and the Al content is 0.17 ppm.

[0073] The specific steps for measuring the metal content in the polymer by the ignition method are conventional technical means in the art. In the examples and comparative examples of the present invention, the ignition method specifically includes: taking 100 g of the unashed polymer or the ashed polymer product and placing it in a muffle furnace. Using a programmed temperature rise, it is heated to 650 °C in 1 hour, and then kept at a constant temperature for 2 hours to ensure complete combustion of the polymer. After that, it is cooled to room temperature. The ash residue after ignition is added to 5 mL of hydrochloric acid solution (the mass fraction of this hydrochloric acid solution is 19%), and after the ash is completely digested, the metal content in the solution is analyzed by ICP-MS.

[0074] Example 2

[0075] This example provides a method for polymer deashing, which includes the following steps:

[0076] (1) Heat 500 mL of a COP cyclohexane solution with a solid content of 15% (mass percentage) to 90 °C, and add 15 mL of a maleic anhydride ethanol solution with a concentration of 0.5 mol / L under vigorous stirring conditions. After continuing to react for 10 minutes under vigorous stirring conditions, maleic anhydride forms a stable water-soluble metal complex with the metal ions in the COP cyclohexane solution, obtaining a mixed solution;

[0077] (2) Use a centrifugal separator to separate the oil and water of the mixed solution, wash the obtained oil phase at 40 °C, and the number of water washing times is 2 times. The volume ratio of the water used for each water washing to the volume of the oil phase is 5:1. After each water washing, a centrifugal separator is used for oil-water separation, and the oil phase is retained for the next water washing after the oil-water separation. The oil phase obtained after the second water washing and oil-water separation is the deashed polymer solution, and this oil phase is denoted as S2;

[0078] (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%, so that the deashed polymer precipitates in the form of a white precipitate. After filtering and drying the white precipitate, the deashed polymer product is obtained, denoted as P2.

[0079] Using the method of this example for long-term deashing of the COP cyclohexane solution, the long-term operation time is 800 hours.

[0080] The unashed polymer obtained by subjecting the COP cyclohexane solution to step (3) of this example is measured for its metal content by the ignition method, as shown in Table 1.

[0081] The Zr content in the polymer product P2 measured by the ignition method is 0.03 ppm, and the Al content is 0.25 ppm.

[0082] Example 3

[0083] This example provides a method for polymer deashing, which includes the following steps:

[0084] (1) Heat 500 mL of a COC methylcyclohexane solution with a solid content of 20% (mass percentage) to 100 °C. Under vigorous stirring conditions, add 100 mL of a cis-methylbutenedioic acid acetone solution with a concentration of 1 mol / L. After continuing to react for 20 minutes under vigorous stirring conditions, cis-methylbutenedioic acid forms a stable water-soluble metal complex with metal ions in the COC methylcyclohexane solution, obtaining a mixed solution;

[0085] (2) Use a centrifugal separator to perform oil-water separation on the mixed solution. Wash the obtained oil phase at 50 °C, and the number of washing times is 4 times. The volume ratio of the water used for each washing to the volume of the oil phase is 10:1. After each washing, use a centrifugal separator to perform oil-water separation. After the oil-water separation, retain the oil phase for the next washing. The oil phase obtained after the 4th washing and oil-water separation is the deashed polymer solution, and this oil phase is denoted as S3;

[0086] (3) Take 500 mL of the oil phase S3 and add it to 2000 mL of an ethanol solution with a volume fraction of 95%. The deashed polymer precipitates in the form of a white precipitate. After filtering and drying the white precipitate, the deashed polymer product is obtained, denoted as P3.

[0087] Use the method of this example to perform long-term deashing on the COC methylcyclohexane solution, and the long-term operation time is 900 hours.

[0088] The undedashed polymer is obtained from the COC methylcyclohexane solution through step (3) of this example, and its metal content is measured by the ignition method, as shown in Table 1.

[0089] The Zr content in the polymer product P3 measured by the ignition method is 0.04 ppm, and the Al content is 0.27 ppm.

[0090] Example 4

[0091] This example provides a method for polymer deashing, which includes the following steps:

[0092] (1) Heat 500 mL of a COC toluene solution with a solid content of 25% (mass percentage) to 110 °C. Under vigorous stirring conditions, add 0.6 mL of a 2-methylmaleic anhydride aqueous solution with a concentration of 2 mol / L. After continuing to react for 30 minutes under vigorous stirring conditions, 2-methylmaleic anhydride forms a stable water-soluble metal complex with metal ions in the COC toluene solution, obtaining a mixed solution;

[0093] (2) Use a centrifugal separator to separate the oil and water in the said mixed liquid, subject the obtained oil phase to water washing at 60 °C, with the number of water washing times being 1 time, the volume ratio of the water consumption for water washing to the volume of the oil phase being 15:1. After water washing, use a centrifugal separator to separate the oil and water, and the obtained oil phase is the polymer solution after ash removal, which is denoted as S4;

[0094] (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%, so that the polymer after ash removal precipitates in the form of a white precipitate. After filtering and drying the said white precipitate, obtain the polymer product after ash removal, which is denoted as P4.

[0095] Use the method of this example to conduct long-term ash removal on the COC toluene solution, and the long-term operation time is 1000 hours.

[0096] Obtain the polymer without ash removal 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.

[0097] The Zr content in the polymer product P4 measured by the ignition method is 0.03 ppm, and the Al content is 0.36 ppm.

[0098] Example 5

[0099] This example provides a method for polymer ash removal, which includes the following steps:

[0100] (1) Heat 500 mL of a COC cyclohexane solution with a solid content of 30% (mass percentage) to 120 °C, add 5 mL of a 2,3-dimethylmaleic anhydride ethanol solution with a concentration of 3 mol / L under vigorous stirring conditions, and continue to react for 40 minutes under vigorous stirring conditions. Then, 2,3-dimethylmaleic anhydride forms a stable water-soluble metal complex with the metal ions in the COC cyclohexane solution to obtain a mixed liquid;

[0101] (2) Use a centrifugal separator to separate the oil and water in the said mixed liquid, subject the obtained oil phase to water washing at 45 °C, with the number of water washing times being 5 times, the volume ratio of the water consumption for each water washing to the volume of the oil phase being 20:1. After each water washing, use a centrifugal separator to separate the oil and water, and retain the oil phase for the next water washing after oil-water separation. The oil phase obtained after the 5th water washing and oil-water separation is the polymer solution after ash removal, which is denoted as S5;

[0102] (3) Take 500 mL of the oil phase S5 and add it to 2000 mL of an ethanol solution with a volume fraction of 95%, so that the polymer after ash removal precipitates in the form of a white precipitate. After filtering and drying the said white precipitate, obtain the polymer product after ash removal, which is denoted as P5.

[0103] Using the method of this embodiment to carry out long-term deashing on the COC cyclohexane solution, the long-term operation time is 1200 hours.

[0104] The undedusted polymer is obtained from the COC cyclohexane solution through step (3) of this embodiment, and its metal content is measured by the ignition method, as shown in Table 1.

[0105] The Zr content in the polymer product P5 measured by the ignition method is 0.04 ppm, and the Al content is 0.12 ppm.

[0106] Example 6

[0107] This embodiment provides a method for polymer deashing, which includes the following steps:

[0108] (1) Heat 500 mL of a COC methylcyclohexane solution with a solid content of 40% (mass percentage) to 130 °C, add 40 mL of a 5 mol / L acetone solution of 2,3-dimethylmaleic anhydride under vigorous stirring conditions, and continue to react for 60 minutes under vigorous stirring conditions. 2,3-dimethylmaleic anhydride forms a stable water-soluble metal complex with metal ions in the COC methylcyclohexane solution to obtain a mixed solution;

[0109] (2) Use a centrifugal separator to carry out oil-water separation on the mixed solution, wash the obtained oil phase at 55 °C, the number of washing times is 3 times, the volume ratio of the water used for each washing to the volume of the oil phase is 3:1, and after each washing, a centrifugal separator is used for oil-water separation. After the oil-water separation, the oil phase is retained for the next washing. The oil phase obtained after the 3rd washing and oil-water separation is the deashed polymer solution, and this oil phase is denoted as S6;

[0110] (3) Take 500 mL of the oil phase S6 and add it to 2000 mL of an ethanol solution with a volume fraction of 95%, so that the deashed polymer precipitates in the form of a white precipitate. After filtering and drying the white precipitate, the deashed polymer product is obtained, denoted as P6.

[0111] Using the method of this embodiment to carry out long-term deashing on the COC methylcyclohexane solution, the long-term operation time is 1500 hours.

[0112] The undedusted polymer is obtained from the COC methylcyclohexane solution through step (3) of this embodiment, and its metal content is measured by the ignition method, as shown in Table 1.

[0113] The Zr content in the polymer product P6 measured by the ignition method is 0.03 ppm, and the Al content is 0.35 ppm.

[0114] Comparative Example 1

[0115] This comparative example provides a method for polymer deashing, which includes the following steps:

[0116] (1) Heat 500 mL of a COC toluene solution with a solid content of 10% (mass percentage), which is the same as that in Example 1, to 80 °C. Under vigorous stirring conditions, add 5 mL of an aqueous adipic acid solution with a concentration of 0.1 mol / L. After continuing to react for 5 minutes under vigorous stirring conditions, a mixed solution is obtained;

[0117] (2) Use a centrifugal separator to separate the oil and water of the mixed solution, wash the obtained oil phase at 30 °C, and the number of washing times is 3 times. The volume ratio of the water used for each washing to the volume of the oil phase is 1:1. After each washing, use a centrifugal separator to separate the oil and water. After the oil-water separation, retain the oil phase for the next washing. The oil phase obtained after the 3rd washing and oil-water separation is the deashed polymer solution, and this oil phase is denoted as S7;

[0118] (3) Take 500 mL of the oil phase S7 and add it to 2000 mL of an ethanol solution with a volume fraction of 95%. The deashed polymer precipitates in the form of a white precipitate. After filtering and drying the white precipitate, the deashed polymer product is obtained, denoted as P7.

[0119] Use the method of this comparative example to perform long-term deashing on the COC toluene solution, and the long-term operation time is 600 hours.

[0120] The Zr content in the polymer product P7 measured by the ignition method is 1.9 ppm, and the Al content is 16 ppm.

[0121] Comparative Example 2

[0122] This comparative example provides a method for polymer deashing, which includes the following steps:

[0123] (1) Heat 500 mL of a COC toluene solution with a solid content of 10% (mass percentage), which is the same as that in Example 1, to 80 °C. Under vigorous stirring conditions, add 5 mL of an aqueous citric acid solution with a concentration of 0.1 mol / L. After continuing to react for 5 minutes under vigorous stirring conditions, a mixed solution is obtained;

[0124] (2) Use a centrifugal separator to separate the oil and water of the mixed solution, wash the obtained oil phase at 30 °C, and the number of washing times is 3 times. The volume ratio of the water used for each washing to the volume of the oil phase is 1:1. After each washing, use a centrifugal separator to separate the oil and water. After the oil-water separation, retain the oil phase for the next washing. The oil phase obtained after the 3rd washing and oil-water separation is the deashed polymer solution, and this oil phase is denoted as S8;

[0125] (3) Take 500 mL of the oil phase S8 and add it to 2000 mL of an ethanol solution with a volume fraction of 95%. The deashed polymer precipitates in the form of a white precipitate. After filtering and drying the white precipitate, the deashed polymer product, denoted as P8, is obtained.

[0126] Using the method of this comparative example to carry out long - cycle deashing on the COC toluene solution, the long - cycle operation time is 600 hours.

[0127] By the ignition method, the Zr content in the polymer product P8 is 2.4 ppm and the Al content is 17 ppm.

[0128] Comparative Example 3

[0129] This comparative example provides a method for polymer deashing, which includes the following steps:

[0130] (1) Take 250 mL of the powdered aluminum oxide used in step (2) of Example 1. After heating to 100 °C, add 100 mL of an aqueous maleic acid solution with a concentration of 0.005 mol / L, continue stirring for 2 hours, then filter, take the filter residue, and dry it at 120 °C for 8 hours to obtain the maleic acid - pretreated aluminum oxide powder; the bulk density of this maleic acid - pretreated aluminum oxide powder is 0.41 g / mL, the specific surface area is 212 m 2 / g, and the pore volume is 0.42 mL / g;

[0131] (2) Heat 500 mL of the COC toluene solution with a solid content of 10% (mass percentage) (the same as that in Example 1) to 50 °C. Under the temperature and pressure conditions of 50 °C and 0.2 Mpa, pass it through an adsorption column filled with the maleic acid - pretreated aluminum oxide powder at a volume space velocity of 0.5 h -1 for adsorption separation. The obtained filtrate is the deashed polymer solution, and this filtrate is denoted as S9;

[0132] (3) Take 500 mL of the filtrate S9 and add it to 2000 mL of an ethanol solution with a volume fraction of 95%. The deashed polymer precipitates in the form of a white precipitate. After filtering and drying the white precipitate, the deashed polymer product, denoted as P9, is obtained.

[0133] Using the method of this comparative example to carry out long - cycle deashing on the COC toluene solution, the long - cycle operation time is 600 hours, and the adsorbent is not replaced during the operation.

[0134] By the ignition method, the Zr content in the polymer product P9 is 4.8 ppm and the Al content is 38 ppm.

[0135] Comparative Example 4

[0136] This comparative example provides a method for polymer deashing, which includes the following steps:

[0137] (1) Heat 500 mL of a COC toluene solution with a solid content of 10% (mass percentage), the same as that in Example 1, to 80 °C. Under vigorous stirring conditions, add 5 mL of an aqueous solution of fumaric acid with a concentration of 0.1 mol / L. After continuing to react under vigorous stirring conditions for 5 minutes, a mixed solution is obtained;

[0138] (2) Use a centrifugal separator to perform oil-water separation on the mixed solution, wash the obtained oil phase at 30 °C, and the number of washing times is 3 times. The volume ratio of the water used for each washing to the volume of the oil phase is 1:1. After each washing, a centrifugal separator is used for oil-water separation. After oil-water separation, the oil phase is retained for the next washing. The oil phase obtained after the 3rd washing and oil-water separation is the deashed polymer solution, and this oil phase is denoted as S10;

[0139] (3) Take 500 mL of the oil phase S10 and add it to 2000 mL of an ethanol solution with a volume fraction of 95%, so that the deashed polymer precipitates in the form of a white precipitate. After filtering and drying the white precipitate, a deashed polymer product is obtained, denoted as P10.

[0140] Use the method of this comparative example to perform long-term deashing on the COC toluene solution, and the long-term operation time is 600 hours.

[0141] The Zr content in the polymer product P10 measured by the ignition method is 5.1 ppm, and the Al content is 24.2 ppm.

[0142] The results of the polymer deashing methods provided in the above Examples 1-6 and Comparative Examples 1-4 are shown in Table 1.

[0143] Table 1 Experimental results of polymer deashing

[0144]

[0145] It can be seen from the experimental results in Table 1 that the polymer deashing methods of Examples 1-6 of the present invention have a significant effect on the removal of metals in the polymer, and the removal efficiency is significantly superior to that of Comparative Examples 1-4. At the same time, the polymer deashing method of the present invention is simple to operate, has a low cost, and has broad industrialization prospects.

Claims

1. A method for polymer deashing, which comprises the following steps: (1) After mixing and reacting a polymer solution to be treated with one or a combination of several of dicarboxylic acids and their derivatives, a mixed solution is obtained; (2) Washing the mixed solution, and the obtained oil phase is the deashed polymer solution; wherein, 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 it has a cis structure in the spatial configuration; the dicarboxylic acid and its derivatives are one or a combination of several of maleic anhydride, cis-methylbutenedioic acid, cis-methylmaleic anhydride, 2,3-dimethylmaleic acid, and 2,3-dimethylmaleic anhydride; The mixing ratio of the polymer solution to be processed 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; the polymer in the polymer solution to be treated is a polyolefin.

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

3. The method for polymer deashing according to claim 2, wherein, the solid content in the polymer solution to be treated is 10%-40%.

4. The method for polymer deashing according to claim 1 or 2, wherein, the polymer in the polymer solution to be treated includes one or a combination of several of cycloolefin copolymer, cycloolefin polymer, polyethylene, polypropylene, polyolefin plastomer, and polyolefin elastomer.

5. The method for polymer deashing according to claim 1, wherein, one or a combination of several of the dicarboxylic acid and its derivatives is mixed with the polymer solution to be treated in the form of a solution, and the concentration of the solution of one or a combination of several of the dicarboxylic acid and its derivatives is 0.1-10 mol / L.

6. The method for polymer deashing according to claim 5, wherein, the concentration of the solution of one or a combination of several of the dicarboxylic acid and its derivatives is 0.1-5 mol / L.

7. The method for polymer deashing according to claim 5, wherein, the solvent in the solution of one or a combination of several of the dicarboxylic acid and its derivatives includes one or a combination of several of water, alcohols, ketones, and hydrocarbons.

8. The method for polymer deashing according to claim 7, wherein, the solvent in the solution of one or a combination of several of the dicarboxylic acid and its derivatives includes one or a combination of several of water, ethanol, and acetone.

9. The method for polymer deashing according to claim 1, wherein, in step (1), the temperature for mixing and reacting the polymer solution to be treated with one or a combination of several of the dicarboxylic acid and its derivatives is 60-150 °C.

10. The method for polymer deashing according to claim 9, wherein, in step (1), the temperature for mixing and reacting the polymer solution to be treated with one or a combination of several of the dicarboxylic acid and its derivatives is 80-130 °C.

11. The method for polymer deashing according to claim 1, wherein, in step (1), the reaction time of the polymer solution to be treated with one or a combination of several of the dicarboxylic acid and its derivatives is 2-120 minutes.

12. The method for polymer deashing according to claim 11, wherein, in step (1), the reaction time of the polymer solution to be treated with one or a combination of several of the dicarboxylic acids and their derivatives is 5 - 60 minutes.

13. The method for polymer deashing according to claim 1, wherein, step (2) specifically includes: performing oil - water separation on the mixture, washing the obtained oil phase with water, performing oil - water separation after washing, and the obtained oil phase is the deashed polymer solution.

14. The method for polymer deashing according to claim 1 or 13, wherein, in step (2), the number of times of water washing is 1 - 5 times.

15. The method for polymer deashing according to claim 13, wherein, in step (2), the temperature of water washing is 30 - 60 °C, and the volume ratio of the amount of water used for water washing to the volume of the oil phase is (1 - 20):

1.

16. The method for polymer deashing according to claim 1, wherein, the method for polymer deashing further includes step (3): mixing the deashed polymer solution with an alcohol to precipitate the deashed polymer in the form of a precipitate, and obtaining the deashed polymer.

17. The method for polymer deashing according to claim 16, wherein, in step (3), the alcohol used includes one or a combination of several of methanol, ethanol, propanol, and isopropanol.

18. The method for polymer deashing according to claim 16, wherein, in step (3), the mixing volume ratio of the deashed polymer solution to the alcohol is 1:(1 - 20).

Images