Methods for polymer decalcification

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 excellent in performance such as optical performance, gas barrier property, chemical resistance, light resistance, etc. They play an irreplaceable role in industry, agriculture, national defense, transportation and people's daily life, 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] Common decalcification methods used in the polymer industrialization process include aqueous extraction, coagulation and sedimentation, and complexing adsorption. Complexing adsorption is the most widely used decalcification method in polymer industrial production, offering advantages such as a simple process, large adsorption capacity, high removal efficiency, fewer interfering factors, and good stability. Complexing agents are broadly classified into two types: inorganic and organic. Inorganic complexing agents are generally easily decomposed at high temperatures and are only applicable to alkaline media, thus limiting their range of application. Organic complexing agents have a wide range of application, but it is usually difficult to reduce the metal content in polymer solutions to below 10 ppm. Furthermore, in industrialization processes, supported adsorbent fillers are generally used for complexing and decalcification. Such adsorbents are solid fillers produced by immersing and roasting an alumina carrier with the complexing agent material, resulting in a low effective load capacity for the complexing agent and certain limitations in their application.

[0005] US4992529A discloses a method for removing metals using mixed acids. This method is characterized by the reaction of a monocarboxylic acid with a metal in the organic phase to produce a carboxylate salt that does not dissolve in the organic phase, the reaction of this carboxylate salt with an inorganic acid in the mixed acid to produce an inorganic salt that dissolves in the aqueous phase, the reduction of the carboxylic acid to return to the organic phase, and the subsequent reaction with the metal in the polymer solution to produce a carboxylate salt, and the repetition of this process until the metal in the polymer solution has completely moved to the aqueous phase, thereby achieving the removal of the remaining metal. Here, the carboxylic acid acts as a phase-transfer catalyst. Although the concept of this method is novel, the removal effect is undesirable and a large amount of water is required.

[0006] CN114534694A discloses a complexed adsorption filler, a method for producing the same, and its use. The adsorption filler is a molecular sieve filler supporting a quinolinol compound, and an organic acid can be supported on the molecular sieve supporting the quinolinol compound. The adsorption filler can effectively remove residual catalysts in polyolefin solutions and has advantages such as a fast demineralization rate, high adsorption capacity, and low pressure loss, making it suitable for catalyst removal in various olefin solution polymerization processes. However, the manufacturing process for the adsorption filler is complex and cumbersome, and at the same time, due to the low amount of quinolinol supported, the adsorption capacity of the adsorption filler is low and the operating cost is high.

[0007] CN114989331A discloses a method for complexing decalcification of polyolefin solutions. The method comprises (1) adding triazaamidine to a polyolefin solution to complexe and adsorb metal ions in the solution and form a complex, and (2) passing the polyolefin solution containing the complex through an adsorption column packed with porous metal oxides to perform adsorption treatment and obtain a purified polyolefin solution. This decalcification method can efficiently remove residual metals from polyolefin solutions, is simple in process, exhibits low filler swelling and low system pressure drop, and has a long service life for the decalcified filler, a long adsorption column replacement cycle, and significantly reduces processing costs. However, since triazaamidine has only average complexing ability with metals, the metal removal rate is low, and the content of metallic aluminum in polymers is particularly high.

[0008] CN102875702A discloses a method for removing metals from polymers. This method, in order to achieve the objective of removing residual metals from latex, employs a system in which an organic base, such as n-butyllithium or phenyllithium, is added to a colloidal solution, an oxidizing agent is added, the reaction is followed by washing with water, and finally centrifugation is performed. While this method has high efficiency in removing residual metals from polymers, the use of organic bases and the introduction of some metal ions result in high costs for raw material input and removal of residual catalysts, as well as high equipment requirements due to the addition of organic bases.

[0009] CN114392724A discloses a deashcrete adsorbent specifically for polyolefins, as well as its manufacturing method and use. The deashcrete adsorbent is prepared by using pyridine-3-carboxylic acid as a complexing agent and supporting it on an oxide carrier. This deashcrete adsorbent can efficiently remove residual metals from polyolefin solutions, significantly reducing the amount of residual metals in polyolefin products. Compared to conventional chelate adsorption methods, it has advantages such as a faster deashcrete rate, higher adsorption capacity, lower swelling, and lower solution pressure loss. However, the manufacturing process for this deashcrete adsorbent is complex and cumbersome, and because the amount of pyridine-3-carboxylic acid supported is low, the adsorption capacity of the adsorbent is low, resulting in high operating costs.

[0010] CN113856637A discloses a method for removing residual metals in the COC and COP production process using a complexing adsorption filler. Compared to conventional adsorption resins, this adsorption filler has advantages such as a fast metal demineralization rate and a large adsorption capacity, while simultaneously not exhibiting swelling. The adsorption filler is manufactured by reacting silica solid, a solvent, and phosphorus tribromide in a specified proportion to obtain silica bromide solid, further reacting it with an appropriate amount of diethyl iminodate to obtain a yellow solid, acidifying it with hydrochloric acid, and then obtaining the adsorption filler. However, the manufacturing process for this adsorption filler is complex and cumbersome, and the heavy metal removal rate is not high.

[0011] US5073621A discloses a demetallation method using water as a solubilizer. This method can suitably remove metals from latex by first dissolving a dicarboxylic acid in water and then adding it to the latex. However, this method is prone to causing emulsification of the latex, which is unfavorable for the reaction between the dicarboxylic acid and metal ions, affecting the rate of metal removal and making the process difficult to control.

[0012] CN1067898A discloses a method for removing residual metal catalysts after the hydrogenation of a polymer. In this method, hydrogen peroxide is added as an oxidizing agent and sebacic acid as a precipitating agent to a hydrogenated butadiene-styrene random copolymer latex. The sebacic acid is then dissolved in an aqueous solution of diethylene glycol-butyl ether to form a sebacic acid solution, which significantly improves the metal removal effect from the latex. However, the sites of the two carboxyl groups of the dicarboxylic acid used in this method are not constant, resulting in poor complexing effect with the metal and thus a low metal removal rate.

[0013] Conventional polymer decalcification technologies have drawbacks such as complex adsorbent preparation processes, long demetallation processes, and low removal efficiency. Therefore, developing novel polymer decalcification methods is one of the urgent issues that needs to be addressed in this field. [Overview of the Initiative]

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

[0015] To achieve the above objective, the present invention Step (1): The polymer solution to be treated is mixed with one or more combinations of dicarboxylic acids and their derivatives and reacted to obtain a mixture. Step (2): Wash the mixture with water to ensure that the resulting oil phase is a deashed polymer solution. Includes, 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, resulting in a cis structure in spatial arrangement. This provides a method for polymer decalcification.

[0016] In the polymer decalcification method described above, preferably, the dicarboxylic acid has a structure represented by the following formula I. [ka] (In Formula I, R1 and R2 are the same or different, and R1 and R2 are each independently selected from an H atom and a linear or branched alkyl group of C1 to C10, preferably R1 and R2 are the same or different, and R1 and R2 are each independently selected from an H atom and a linear or branched alkyl group of C1 to C5.)

[0017] In the polymer demineralization method described above, preferably, the dicarboxylic acid derivative includes one or more combinations of acid anhydrides, acid halides, amides, esters, and nitriles obtained from the dicarboxylic acid. More preferably, the dicarboxylic acid derivative includes a dicarboxylic acid anhydride.

[0018] In the polymer decalcification method described above, preferably, the acid anhydride of the dicarboxylic acid has a structure represented by the following formula II. [ka] (In Formula II, R1 and R2 are the same or different, and R1 and R2 are each independently selected from an H atom and a linear or branched alkyl group of C1 to C10, preferably R1 and R2 are the same or different, and R1 and R2 are each independently selected from an H atom and a linear or branched alkyl group of C1 to C5.)

[0019] In the polymer demineralization method described above, preferably, the dicarboxylic acid and its derivatives include one or a combination of several such substances, including cis-butenioic acid (i.e., maleic acid), cis-butenioic anhydride (i.e., maleic anhydride), cis-methylbutenioic acid (i.e., 2-methylmaleic acid), cis-methylbutenioic 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 metal catalysts 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 washing with water, and the obtained 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 derivative and the metal ion 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, and more specifically, from a polymerization reaction vessel in a solution polymerization process.

[0026] In the polymer demineralization method described above, preferably, the mixing ratio of the polymer solution to be treated and one or more combinations of the dicarboxylic acid and its derivatives is 1g of polymer:10 -3 ~10 -5 This is a combination of one or more types of dicarboxylic acids and their derivatives in moles.

[0027] In the polymer demineralization method described above, 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 to 10 mol / L, more preferably 0.1 to 5 mol / L.

[0028] In some specific embodiments of the present invention, the solvent in a 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, and preferably includes one or more combinations of water, ethanol, and acetone.

[0029] In the polymer demineralization method described above, preferably, in step (1), the process of mixing the polymer solution to be treated with a combination of one or more dicarboxylic acids and their derivatives and reacting them is carried out under stirring, and the rotational speed of the stirring can be adjusted by those skilled in the art according to the scale of production, preferably by using vigorous stirring.

[0030] In the polymer demineralization method described above, 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 polymer demineralization method described above, 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 polymer deashilation method described above, preferably, step (2) specifically includes separating the oil and water from the mixture, washing the resulting oil phase with water, performing oil and water separation after washing, and the resulting oil phase being the deashilated polymer solution.

[0033] In the polymer decalcification method described above, preferably, in step (2), the number of times the water is washed is 1 to 5 times, and more preferably, the number of times the water is washed is 1 to 3 times.

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

[0035] Those skilled in the art will understand that when multiple washes are performed, oil-water separation is carried out after each wash to obtain the oil phase. The water-soluble metal complex is in the aqueous 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-purpose centrifugal separator.

[0037] In specific embodiments of the present invention, the method for polymer demineralization preferably further comprises the step (3) of mixing the demineralized polymer solution with alcohol to precipitate the demineralized polymer as a precipitate to obtain the demineralized polymer. More preferably, the alcohol used includes one or more combinations such as methanol, ethanol, propanol, and isopropanol, and even more preferably, the alcohol used is ethanol. More preferably, the volume ratio of the demineralized polymer solution 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 commonly adjusted by those skilled in the art.

[0038] In some specific embodiments of the present invention, step (3) may further include obtaining the decalcified polymer after performing a standard operation such as solid-liquid separation (e.g., filtration) and drying of the decalcified polymer precipitated as a precipitate.

[0039] The present invention provides a method for polymer decalcification, and more particularly, a method for removing residual metals from the main catalyst and co-catalysts in polymers (mainly polyolefins). The method of the present invention uses dicarboxylic acids and their derivatives having a cis structure in spatial arrangement as metal complexing agents. Such dicarboxylic acids and their derivatives having a cis structure form a cyclic transition state with metal ions in the polymer solution, further forming a stable water-soluble metal complex. Subsequently, the removal of the water-soluble metal complex is completed by washing with water, and the resulting oil phase is the decalcified polymer solution.

[0040] The polymer decalcification method 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 spatial arrangement as metal complexing agents, forming a cyclic transition state with metal ions to promote the formation of metal complexes and create stable water-soluble metal complexes, thereby efficiently complexing and removing metals, and significantly improving the rate of metal removal from polymer solutions; 2. The present invention removes metal complexes by washing with water, thus having advantages such as simple operation and low cost. Therefore, the polymer decalcification method of the present invention can efficiently remove metal ions remaining in polymer solutions, and can significantly reduce residual metals in polymer products, especially polyolefin products. Compared with conventional polymer decalcification technologies, the present invention has advantages such as high decalcification efficiency, high speed, simple process, and low cost, and can be widely applied in the field of polymer metal removal, possessing versatility and efficiency, and has broad potential for industrialization. [Modes for carrying out the invention]

[0041] To provide a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the proposed technical aspects of the invention will be described in detail below, but this should not be understood as limiting the scope of the invention's applicability.

[0042] According to specific embodiments of the present invention, preferably, the polymer decalcification method provided by the present invention includes the following steps:

[0043] Step (1): At 60-150°C (preferably 80-130°C) and under vigorous stirring, one or more combinations of dicarboxylic acid and its derivatives are added to the polymer solution to be treated and reacted under vigorous stirring for 2-120 minutes (preferably 5-60 minutes) to form a water-soluble metal complex with the combination of dicarboxylic acid and its derivatives and the metal ions in the polymer solution to be treated, and a mixed solution is obtained.

[0044] Here, the dicarboxylic acid has a structure represented by the following formula I. [ka] (In Formula I, R1 and R2 are the same or different, and R1 and R2 are each independently selected from an H atom and a linear or branched alkyl group of C1 to C10, preferably R1 and R2 are the same or different, and R1 and R2 are each independently selected from an H atom and a linear or branched alkyl group of C1 to C5.)

[0045] The dicarboxylic acid derivative includes one or more combinations of acid anhydrides, acid halides, amides, esters, and nitriles obtained from the dicarboxylic acid, preferably the dicarboxylic acid derivative includes a dicarboxylic acid anhydride, and the dicarboxylic acid anhydride has the structure shown in formula II below. [ka] (In Formula II, R1 and R2 are the same or different, and R1 and R2 are each independently selected from an H atom and a linear or branched alkyl group of C1 to C10, preferably R1 and R2 are the same or different, and R1 and R2 are each independently selected from an H atom and a linear or branched alkyl group of C1 to C5.)

[0046] The solid content of the polymer solution to be treated is 5-50% (by mass), preferably 10-40% (by mass), the polymer in the polymer solution to be treated may include one or more combinations of cycloolefin copolymers (COC), cycloolefin polymers (COP), polyethylene, polypropylene, polyolefin plastomers (POP), and polyolefin elastomers (POE), the solvent in the polymer solution to be treated may include one or more combinations of toluene, cyclohexane, and methylcyclohexane, and the polymer solution to be treated may come from a polymerization reaction unit in a polymer production process, specifically from a polymerization reaction vessel 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 1g of polymer:10 -3 ~10 -5 This is a combination of one or more types of dicarboxylic acids and their derivatives in moles.

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

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

[0050] Step (3): Add the decalcified polymer solution to alcohol to precipitate the decalcified polymer, thereby obtaining the decalcified polymer.

[0051] The alcohol used here includes one or more types of alcohol such as methanol, ethanol, propanol, and isopropanol, and preferably the alcohol used is ethanol. The volume ratio of the demineralized polymer solution to the alcohol is 1:(1~20), and 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 embodiment provides a method for polymer decalcification comprising the following steps.

[0053] Step (1): A 500 mL COC toluene solution with a solid content of 10% (by mass percentage) was heated to 80°C, and 5 mL of a 0.1 mol / L aqueous maleic acid solution was added under vigorous stirring. The mixture was then reacted for 5 minutes under vigorous stirring until the maleic acid and the metal ions in the COC toluene solution formed a stable water-soluble metal complex, yielding a mixed solution.

[0054] Step (2): The mixture is separated into oil and water using a centrifuge, and the resulting oil phase is washed with water at 30°C for three washes, with a volume ratio of 1:1 between the amount of water used and the volume of the oil phase in each wash. After each wash, oil and water separation is performed using a centrifuge, and the oil phase is retained after the oil and water separation for the next wash. The oil phase obtained after the third wash and oil and water separation is the deashed polymer solution and is denoted as S1.

[0055] Step (3): Take 500 mL of oil phase S1 and add it to 2000 mL of a 95% volume fraction ethanol solution. The demineralized polymer will precipitate as a white precipitate. Filter and dry the white precipitate to obtain the demineralized polymer product, which is labeled P1.

[0056] In this embodiment, long-period decalcification was performed on a COC toluene solution using the method described, and the long-period operation time was 600 hours.

[0057] The COC toluene solution was subjected to step (3) of this example to obtain an undecalcified polymer, and its metal content was measured by ignition, as shown in Table 1.

[0058] Measurements using the ignition method revealed that the Zr content in polymer product P1 was 0.02 ppm and the Al content was 0.17 ppm.

[0059] The specific steps for measuring the metal content in a polymer by ignition are common in this field. Specifically, the ignition method employed in the examples and comparative examples of the present invention involved placing 100 g of un-decalcified polymer or de-decalcified polymer product into a muffle furnace, raising the temperature to 650°C in 1 hour using a programmed heating method, then maintaining a constant temperature for 2 hours to allow the polymer to burn completely, then cooling to room temperature, adding the remaining ash after ignition to 5 mL of hydrochloric acid solution (the mass fraction of the hydrochloric acid solution was 19%), and after the ash was completely dissolved, the metal content in the solution was analyzed by ICP-MS.

[0060] Example 2 This embodiment provides a method for polymer decalcification comprising the following steps.

[0061] Step (1): A 500 mL COP-cyclohexane solution with a solid content of 15% (by mass percentage) was heated to 90°C, and 15 mL of a 0.5 mol / L maleic anhydride ethanol solution was added under vigorous stirring. The mixture was then reacted for 10 minutes under vigorous stirring until the maleic anhydride and the metal ions in the COP-cyclohexane solution formed a stable water-soluble metal complex, yielding a mixed solution.

[0062] Step (2): The mixture is separated into oil and water using a centrifuge, and the resulting oil phase is washed with water at 40°C for two washes. The ratio of the amount of water used for each wash to the volume of the oil phase is 5:1. After each wash, oil and water separation is performed using a centrifuge, and the oil phase is retained after the oil and water separation for the next wash. The oil phase obtained after the second wash and oil and water separation is the deashed polymer solution and is denoted as S2.

[0063] Step (3): Take 500 mL of oil phase S2 and add it to 2000 mL of a 95% volume fraction ethanol solution. The demineralized polymer will precipitate as a white precipitate. Filter and dry the white precipitate to obtain the demineralized polymer product, which is labeled P2.

[0064] In this example, long-period decalcification was performed on a COP-cyclohexane solution using the method described, and the long-period operation time was 800 hours.

[0065] The COP-cyclohexane solution was subjected to step (3) of this example to obtain an undecalcified polymer, and its metal content was measured by ignition, as shown in Table 1.

[0066] Measurements using the ignition method revealed that the Zr content in the polymer product P2 was 0.03 ppm and the Al content was 0.25 ppm.

[0067] Example 3 This embodiment provides a method for polymer decalcification comprising the following steps.

[0068] Step (1): A 500 mL COC methylcyclohexane solution with a solid content of 20% (by mass percentage) was heated to 100°C, and 100 mL of a 1 mol / L acetone solution of cis-butenioic acid was added under vigorous stirring. The mixture was then reacted for 20 minutes under vigorous stirring until the cis-butenioic acid and the metal ions in the COC methylcyclohexane solution formed a stable water-soluble metal complex, yielding a mixed solution.

[0069] Step (2): The mixture is separated into oil and water using a centrifuge, and the resulting oil phase is washed with water at 50°C for a total of four washes. The ratio of the amount of water used for each wash to the volume of the oil phase is 10:1. After each wash, oil and water separation is performed using a centrifuge. After the oil and water separation, the oil phase is retained for the next wash. The oil phase obtained after the fourth wash and oil and water separation is the deashed polymer solution and is denoted as S3.

[0070] Step (3): 500 mL of oil phase S3 was added to 2000 mL of a 95% volume fraction ethanol solution, and the demineralized polymer precipitated as a white precipitate. The white precipitate was filtered and dried to obtain the demineralized polymer product, which was labeled P3.

[0071] In this example, long-period decalcification was performed on a COC methylcyclohexane solution using the method described, and the long-period operation time was 900 hours.

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

[0073] Measurements using the ignition method revealed that the Zr content in the polymer product P3 was 0.04 ppm and the Al content was 0.27 ppm.

[0074] Example 4 This embodiment provides a method for polymer decalcification comprising the following steps.

[0075] Step (1): A 500 mL COC toluene solution with a solid content of 25% (by mass percentage) was heated to 110°C, and 0.6 mL of a 2 mol / L aqueous solution of 2-methylmaleic anhydride was added under vigorous stirring. The mixture was then reacted for 30 minutes under vigorous stirring until the 2-methylmaleic anhydride and the metal ions in the COC toluene solution formed a stable water-soluble metal complex, yielding a mixed solution.

[0076] Step (2): The mixture is separated into oil and water using a centrifuge, and the resulting oil phase is washed with water at 60°C for one wash. The ratio of the amount of water used for washing to the volume of the oil phase is 15:1. After washing, oil and water separation is performed using a centrifuge, and the resulting oil phase is the polymer solution after deashing, which is denoted as S4.

[0077] Step (3): Take 500 mL of oil phase S4 and add it to 2000 mL of a 95% volume fraction ethanol solution. The demineralized polymer will precipitate as a white precipitate. Filter and dry the white precipitate to obtain the demineralized polymer product, which is labeled P4.

[0078] In this embodiment, long-period decalcification was performed on a COC toluene solution using the method described, and the long-period operation time was 1000 hours.

[0079] The COC toluene solution was subjected to step (3) of this example to obtain an undecalcified polymer, and its metal content was measured by ignition, as shown in Table 1.

[0080] Measurements using the ignition method revealed that the Zr content in the polymer product P4 was 0.03 ppm and the Al content was 0.36 ppm.

[0081] Example 5 This embodiment provides a method for polymer decalcification comprising the following steps.

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

[0083] Step (2): The mixture is separated into oil and water using a centrifuge, and the resulting oil phase is washed with water at 45°C for a total of 5 washes. The ratio of the amount of water used for each wash to the volume of the oil phase is 20:1. After each wash, oil and water separation is performed using a centrifuge. After the oil and water separation, the oil phase is retained and the next wash is performed. The oil phase obtained after the 5th wash and oil and water separation is the deashed polymer solution and is denoted as S5.

[0084] Step (3): 500 mL of oil phase S5 is taken and added to 2000 mL of a 95% volume fraction ethanol solution to precipitate the demineralized polymer as a white precipitate. The white precipitate is filtered and dried to obtain the demineralized polymer product, which is labeled P5.

[0085] In this embodiment, long-period decalcification was performed on a COC cyclohexane solution using the method described, and the long-period operation time was 1200 hours.

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

[0087] Measurements using the ignition method revealed that the Zr content in the polymer product P5 was 0.04 ppm and the Al content was 0.12 ppm.

[0088] Example 6 This embodiment provides a method for polymer decalcification comprising the following steps.

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

[0090] Step (2): The mixture is separated into oil and water using a centrifuge, and the resulting oil phase is washed with water at 55°C for three washes. The ratio of the amount of water used for each wash to the volume of the oil phase is 3:1. After each wash, oil and water separation is performed using a centrifuge. After the oil and water separation, the oil phase is retained for the next wash. The oil phase obtained after the third wash and oil and water separation is the deashed polymer solution and is denoted as S6.

[0091] Step (3): Take 500 mL of oil phase S6 and add it to 2000 mL of a 95% volume fraction ethanol solution. The demineralized polymer will precipitate as a white precipitate. Filter and dry the white precipitate to obtain the demineralized polymer product, which is labeled P6.

[0092] In this embodiment, long-period decalcification was performed on a COC methylcyclohexane solution using the method described above, and the long-period operation time was 1500 hours.

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

[0094] Measurements using the ignition method revealed that the Zr content in 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 decalcification comprising the following steps.

[0096] Step (1): 500 mL of a 10% solids (by mass) COC toluene solution (same as in Example 1) was heated to 80°C, and 5 mL of a 0.1 mol / L aqueous adipic acid solution was added under vigorous stirring. The mixture was then reacted for 5 minutes under continued vigorous stirring to obtain the mixture.

[0097] Step (2): The mixture is separated into oil and water using a centrifuge, and the resulting oil phase is washed with water at 30°C for three washes, with a volume ratio of 1:1 between the amount of water used and the volume of the oil phase in each wash. After each wash, oil and water separation is performed using a centrifuge, and the oil phase is retained after the oil and water separation for the next wash. The oil phase obtained after the third wash and oil and water separation is the deashed polymer solution and is denoted as S7.

[0098] Step (3): Take 500 mL of oil phase S7 and add it to 2000 mL of a 95% volume fraction ethanol solution. The demineralized polymer will precipitate as a white precipitate. Filter and dry the white precipitate to obtain the demineralized polymer product, which is labeled P7.

[0099] Long-period decalcification was performed on a COC toluene solution using the method described in this comparative example, and the long-period operation time was 600 hours.

[0100] Measurements using the ignition method revealed that the Zr content in 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 decalcification comprising the following steps.

[0102] Step (1): 500 mL of a 10% solids (by mass) COC toluene solution (same as in Example 1) was heated to 80°C, and 5 mL of a 0.1 mol / L aqueous citric acid solution was added under vigorous stirring. The mixture was then reacted for 5 minutes under continued vigorous stirring to obtain the mixture.

[0103] Step (2): The mixture is separated into oil and water using a centrifuge, and the resulting oil phase is washed with water at 30°C for three washes, with a volume ratio of 1:1 between the amount of water used and the volume of the oil phase in each wash. After each wash, oil and water separation is performed using a centrifuge, and the oil phase is retained after the oil and water separation for the next wash. The oil phase obtained after the third wash and oil and water separation is the deashed polymer solution and is denoted as S8.

[0104] Step (3): Take 500 mL of oil phase S8 and add it to 2000 mL of a 95% volume fraction ethanol solution. The demineralized polymer will precipitate as a white precipitate. Filter and dry the white precipitate to obtain the demineralized polymer product, which is labeled P8.

[0105] In this comparative example, long-period decalcification was performed on a COC toluene solution using the method described above, and the long-period operation time was 600 hours.

[0106] Measurements using the ignition method revealed that the Zr content in 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 decalcification comprising the following steps.

[0108] Step (1): Take 250 mL of the powdered aluminum trioxide used in Step (2) of Example 1, raise the temperature to 100°C, add 100 mL of a 0.005 mol / L aqueous maleic acid solution, continue stirring for 2 hours, filter, remove the filtration residue, and dry at 120°C for 8 hours to obtain aluminum trioxide powder pretreated with maleic acid. The bulk density of the aluminum trioxide powder pretreated with maleic acid is 0.41 g / mL and the specific surface area is 212 m². 2 The pore volume was 0.42 mL / g.

[0109] Step (2): Heat 500 mL of a 10% solids content (by mass percentage) COC toluene solution (same as in Example 1) to 50°C and incubate for 0.5 hours at a temperature and pressure of 50°C and 0.2 MPa. -1 The alumina powder, pretreated with maleic acid, was passed through an adsorption column loaded with the aforementioned volume-space velocity for adsorption separation. The resulting filtrate was the decalcified polymer solution, denoted as S9.

[0110] Step (3): Take 500 mL of filtrate S9 and add it to 2000 mL of a 95% volume fraction ethanol solution to precipitate the decalcified polymer as a white precipitate. Filter and dry the white precipitate to obtain the decalcified polymer product, which is labeled P9.

[0111] In this comparative example, long-period decalcification was performed on a COC toluene solution using the method described above, with a long-period operation time of 600 hours, and the adsorbent was not replaced during the operation.

[0112] Measurements using the ignition method revealed that the Zr content in 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 decalcification comprising the following steps.

[0114] Step (1): 500 mL of a 10% solids (by mass percentage) COC toluene solution (same as in Example 1) was heated to 80°C, and 5 mL of a 0.1 mol / L aqueous fumaric acid solution was added under vigorous stirring. The mixture was then reacted for 5 minutes under continued vigorous stirring to obtain the mixture.

[0115] Step (2): The mixture is separated into oil and water using a centrifuge, and the resulting oil phase is washed with water at 30°C for three washes, with a volume ratio of 1:1 between the amount of water used and the volume of the oil phase in each wash. After each wash, oil and water separation is performed using a centrifuge, and the oil phase is retained after the oil and water separation for the next wash. The oil phase obtained after the third wash and oil and water separation is the deashed polymer solution and is denoted as S10.

[0116] Step (3): Take 500 mL of oil phase S10 and add it to 2000 mL of a 95% volume fraction ethanol solution. The demineralized polymer will precipitate as a white precipitate. Filter and dry the white precipitate to obtain the demineralized polymer product, which is labeled as P10.

[0117] In this comparative example, long-period decalcification was performed on a COC toluene solution using the method described above, and the long-period operation time was 600 hours.

[0118] Measurements using the ignition method revealed that the Zr content in the polymer product P10 was 5.1 ppm and the Al content was 24.2 ppm.

[0119] Table 1 shows the results of the polymer decalcification methods provided in Examples 1-6 and Comparative Examples 1-4 above.

[0120] [Table 1]

[0121] As can be seen from the experimental results in Table 1, the polymer decalcification methods of Examples 1 to 6 of the present invention are remarkably effective in removing metals from polymers, and their removal efficiency is clearly superior to that of Comparative Examples 1 to 4. Furthermore, the polymer decalcification methods of the present invention are easy to operate, low-cost, and have great potential for widespread industrialization.

Claims

1. A method for polymer decalcification, Step (1): The polymer solution to be treated is mixed with one or more combinations of dicarboxylic acid and its derivatives and reacted to obtain a mixture. Step (2): Wash the mixture with water to ensure that the resulting oil phase is the polymer solution after deashification. Includes, 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, and has a cis structure in spatial arrangement. The dicarboxylic acid is one or more selected from cis-methylbutenioic acid and 2,3-dimethylmaleic acid, and the derivative of the dicarboxylic acid is one or more selected from cis-methylbutenioic anhydride and 2,3-dimethylmaleic anhydride. The polymer in the polymer solution to be treated includes one or more of the following: cycloolefin copolymer, cycloolefin polymer, polyethylene, polypropylene, polyolefin plastomer, and polyolefin elastomer. The polymer solution to be treated is produced by polymerization using a metallocene catalyst system. Methods for polymer decalcification.

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

3. 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 The polymer decalcification method according to claim 1, wherein the combination is one or more mol dicarboxylic acids and their derivatives.

4. The polymer demineralization method according to claim 1, wherein one or more combinations of the dicarboxylic acid and its derivatives are mixed as a solution with the polymer solution to be treated, 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.

5. The polymer demineralization method according to claim 4, wherein 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.

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

7. The polymer demineralization method according to claim 6, wherein 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.

8. The polymer demineralization method according to claim 1, wherein 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.

9. The polymer demineralization method according to claim 8, wherein 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.

10. The method for polymer deashing according to claim 1, wherein step (2) specifically includes separating the mixed liquid from the oil-water, washing the obtained oil phase with water, performing oil-water separation after washing, and the obtained oil phase being the deashed polymer solution.

11. The polymer decalcification method according to claim 1, wherein in step (2), the number of washes is 1 to 5 times.

12. The polymer deashilation method according to claim 10, wherein in step (2), the temperature of the water wash is 30 to 60°C, and the volume ratio of the amount of water used for the water wash to the oil phase is 1 to 20:

1.

13. The method for decalcifying a polymer according to claim 1, further comprising step (3) of mixing the decalcified polymer solution with alcohol to precipitate the decalcified polymer as a precipitate, thereby obtaining the decalcified polymer.

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