Ion exchange resin and method for producing the same

Abstract

The application provides an ion exchange resin and a preparation method thereof. The preparation method of the ion exchange resin comprises the following steps: performing a polymerization reaction on a mixed system comprising a support material, an acrylate monomer, a crosslinking agent and an initiator to obtain a composite microsphere; performing a chloromethylation reaction on the composite microsphere, a second solvent and a chloromethylation reagent to obtain a composite chloromicrosphere; and performing an amination reaction or a sulfonation reaction on the composite chloromicrosphere to obtain the ion exchange resin. The ion exchange resin prepared by the preparation method has the advantages of high mechanical strength and strong adsorption capacity. When the ion exchange resin is applied to the purification of a crude terephthalic acid diethylene glycol ester, the ion exchange resin can be stably operated in a water system, the generation of a hydrolysis byproduct is reduced, the product purity is significantly improved, and the industrial purification of waste polyester alcoholysis products is effectively supported.

Description

Technical Field

[0001] This invention relates to the field of waste polyester recycling, and more particularly to an ion exchange resin and its preparation method. Background Technology

[0002] Diethylene terephthalate (BHET), a product of alcoholysis in waste textiles, can be used for the repolymerization of high-quality polyester after decolorization and purification. Besides colored dyes, BHET obtained through alcoholysis also contains some anionic and cationic impurities, including sodium (Na₂O₃) as a cation. + Ca 2+ Fe 2 / 3+ Sb + Mg 2+ Co 2+ Anions include Cl. - SO4 2- NO3 - These impurity ions mainly originate from catalysts and additives in the polyester production process. Their presence can affect the subsequent repolymerization of BHET and the quality of recycled polyester.

[0003] Resin adsorption is currently the mainstream technology for BHET ion removal due to its advantages such as simple operation, controllable operating costs, and no secondary pollution. Chinese patent CN117680204A discloses a purification method for monomers obtained from the depolymerization of waste polyester in ethylene glycol, which removes ions from crude BHET by connecting cation exchange resin columns and anion exchange resin columns in series. However, the high viscosity of the ethylene glycol system significantly reduces ion exchange efficiency. Furthermore, in the series ion exchange process, BHET is exposed between the resin columns for a long time, making it prone to hydrolysis and generating byproducts, further reducing product purity.

[0004] In existing technologies, traditional resins used for BHET ion removal suffer from problems such as low ion exchange efficiency, low mechanical strength, easy generation of hydrolysis byproducts, and poor product recovery rate. Therefore, developing an ion exchange resin with high ion exchange efficiency, high mechanical strength, and reusability has become an urgent need to overcome existing technological bottlenecks and meet the industrialization needs of waste polyester alcoholysis recycling. Summary of the Invention

[0005] This invention provides an ion exchange resin and its preparation method. The ion exchange resin prepared by the method of this invention has advantages such as high mechanical strength and strong adsorption capacity. When applied to the purification of diethylene terephthalate, it can operate stably in an aqueous system, reduce the generation of hydrolysis byproducts, and significantly improve product purity, thus strongly supporting the industrial purification of waste polyester alcoholysis products.

[0006] This invention provides a method for preparing an ion exchange resin, comprising the following steps: polymerizing a mixture including a supporting material, an acrylate monomer, a crosslinking agent, and an initiator to obtain composite microspheres; mixing the composite microspheres, a second solvent, and a chloromethylating agent and then performing a chloromethylation reaction to obtain composite chlorospheres; and subjecting the composite chlorospheres to an amination reaction or a sulfonation reaction to obtain the ion exchange resin.

[0007] According to one embodiment of the present invention, the mass ratio of the support material to the acrylate monomer is (1~2):1.

[0008] According to one embodiment of the present invention, the mass ratio of the acrylate monomer, the crosslinking agent and the initiator is 1:(0.05~0.07):(0.02~0.1).

[0009] According to one embodiment of the present invention, the crosslinking agent comprises divinylbenzene; and / or, the initiator comprises azobisisobutyronitrile.

[0010] According to one embodiment of the present invention, the support material comprises polystyrene material, wherein the median particle size of the polystyrene material is 0.45 mm to 1.25 mm.

[0011] According to one embodiment of the present invention, the mixed system further includes a first solvent, wherein the first solvent includes toluene.

[0012] According to one embodiment of the present invention, the preparation process of the mixed system includes: mixing the acrylate monomer, crosslinking agent and initiator with a first solvent to obtain a first mixture; mixing the support material with the first mixture, and swelling for 2 h to 4 h to obtain the mixed system.

[0013] According to one embodiment of the present invention, the polymerization reaction is carried out at a temperature of 60°C to 80°C and for a reaction time of 8h to 10h.

[0014] According to one embodiment of the present invention, the second solvent comprises dichloroethane.

[0015] According to one embodiment of the present invention, the mass ratio of the second solvent to the composite microspheres is (2~3):1.

[0016] According to one embodiment of the present invention, the chloromethylating agent includes chloroethyl ether and / or chloromethyl ether.

[0017] According to one embodiment of the present invention, the mass ratio of the chloromethylating agent to the composite microspheres is (2~3):1.

[0018] According to one embodiment of the present invention, the process of mixing the composite microspheres, the second solvent, and the chloromethylating agent and then carrying out the chloromethylation reaction includes: mixing the composite microspheres, the second solvent, and the chloromethylating agent, swelling for 2 h to 4 h, then adding a catalyst, and then carrying out the chloromethylation reaction to obtain the composite chlorospheres; wherein the catalyst includes zinc chloride.

[0019] According to one embodiment of the present invention, the reaction temperature of the chloromethylation reaction is 40°C to 45°C, and the reaction time is 8 h to 10 h.

[0020] According to one embodiment of the present invention, the ion exchange resin is an anion exchange resin, and the process of amination reaction of the composite chloride spheres includes: mixing the composite chloride spheres with an aqueous solution containing an amination reagent and then carrying out the amination reaction to obtain the anion exchange resin.

[0021] According to one embodiment of the present invention, the amination agent includes trimethylamine.

[0022] According to one embodiment of the present invention, the mass ratio of the amination reagent to the composite chlorine ball is (2~4):1.

[0023] According to one embodiment of the present invention, the amination reaction is carried out at a temperature of 40°C to 50°C and for a reaction time of 12 h to 24 h.

[0024] According to one embodiment of the present invention, the ion exchange resin is a cation exchange resin, and the process of sulfonating the composite chlorine ball includes: mixing the composite chlorine ball with a third solvent, swelling for 2 h to 4 h, and then adding a sulfonating agent to carry out the sulfonation reaction to obtain the cation exchange resin.

[0025] According to one embodiment of the present invention, the mass ratio of the third solvent to the composite chlorine ball is (2~4):1.

[0026] According to one embodiment of the present invention, the sulfonating agent comprises concentrated sulfuric acid.

[0027] According to one embodiment of the present invention, the mass ratio of the sulfonating agent to the composite chlorine ball is (2~4):1.

[0028] According to one embodiment of the present invention, the sulfonation reaction is carried out at a temperature of 80°C to 90°C for a reaction time of 6 to 8 hours.

[0029] In another aspect, the present invention provides an ion exchange resin prepared according to the method for preparing the ion exchange resin.

[0030] In another aspect, the present invention provides a method for purifying diethylene terephthalate, comprising the following steps: purifying the diethylene terephthalate to be purified using a resin material to obtain purified diethylene terephthalate; wherein the resin material comprises a cation exchange resin and an anion exchange resin; the anion exchange resin is prepared according to the method for preparing ion exchange resins, wherein the composite chloride spheres are subjected to the amination reaction to obtain the anion exchange resin; the cation exchange resin is prepared according to the method for preparing ion exchange resins, wherein the composite chloride spheres are subjected to the sulfonation reaction to obtain the cation exchange resin.

[0031] According to one embodiment of the present invention, the diethylene terephthalate to be purified includes crude diethylene terephthalate obtained from polyester raw material by alcoholysis.

[0032] According to one embodiment of the present invention, the volume ratio of the anion exchange resin to the cation exchange resin is 1:(2~3).

[0033] According to one embodiment of the present invention, the purification process includes: mixing the diethylene terephthalate to be purified with water to obtain an ion exchange stock solution; passing the ion exchange stock solution through an ion exchange column provided with the resin material to obtain an ion exchange liquid; and crystallizing the ion exchange liquid to obtain the purified diethylene terephthalate.

[0034] The implementation of this invention has at least the following beneficial effects: The ion exchange resin prepared by the method of this invention has a three-dimensional cross-linked network structure, which helps to enhance the mechanical strength and stability of the resin and solves the problem of the easy breakage of traditional resins in aqueous systems. Simultaneously, the quaternary ammonium groups and sulfonic acid groups introduced through chloromethylation, amination, or sulfonation reactions endow the resin with highly efficient adsorption capacity for anions and cations. When applied to the purification of diethylene terephthalate, it can operate stably in aqueous systems and is not easily broken, while efficiently removing anions and cations, significantly reducing the generation of hydrolysis byproducts and improving product purity, providing strong support for the industrial purification of waste polyester alcoholysis products. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. The specific embodiments listed below are merely descriptions of the principles and features of this invention, and the examples given are only for explaining this invention and are not intended to limit the scope of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0036] This invention provides a method for preparing an ion exchange resin, comprising the following steps: polymerizing a mixture including a supporting material, an acrylate monomer, a crosslinking agent, and an initiator to obtain composite microspheres; mixing the composite microspheres, a second solvent, and a chloromethylating agent and then performing a chloromethylation reaction to obtain composite chlorospheres; and subjecting the composite chlorospheres to an amination reaction or a sulfonation reaction to obtain the ion exchange resin.

[0037] When the above-mentioned composite chlorine balls are subjected to an amination reaction, the resulting ion exchange resin is an anion exchange resin; when the above-mentioned composite chlorine balls are subjected to a sulfonation reaction, the resulting ion exchange resin is a cation exchange resin.

[0038] According to the inventors' research, in the above preparation method, a supporting material serves as the backbone substrate, and acrylate monomers undergo polymerization under the synergistic effect of crosslinking agents and initiators. The molecular chains of the acrylate monomers grow on the surface and within the pores of the supporting material, forming a three-dimensional network structure. This three-dimensional network structure endows the composite microspheres with both excellent skeletal stability and adsorption potential, providing a foundation for high mechanical strength and chemical stability in ion exchange resins. A second solvent permeates the composite microspheres, causing them to swell, which increases the reaction contact area and introduces active chloromethyl groups, providing key active sites for functionalization modification. The composite chlorospheres undergo amination or sulfonation reactions, allowing the chloromethyl groups to undergo nucleophilic substitution with the amination reagent or sulfonation with the sulfonation reagent, thereby introducing ion exchange active groups such as quaternary ammonium groups or sulfonic acid groups, enhancing the adsorption capacity of the ion exchange resin. The ion exchange resin prepared by this method effectively solves the problem of the fragility of traditional resins with its three-dimensional crosslinked network structure, while simultaneously achieving efficient ion adsorption based on highly active functional groups, balancing stability and adsorption performance.

[0039] In some embodiments, the mass ratio of the support material to the acrylate monomer can be (1~2):1, for example, 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2:1, or any combination thereof. A mass ratio of not less than 1:1 helps to enhance the skeletal strength of the composite microspheres and avoid microsphere breakage during subsequent swelling and modification processes; a mass ratio of not more than 2:1 helps to provide sufficient active components for the polymerization reaction and promotes the full progress of the polymerization reaction.

[0040] In some embodiments, the mass ratio of the acrylate monomer, the crosslinking agent, and the initiator can be 1:(0.05~0.07):(0.02~0.1), for example, 1:0.05:0.02, 1:0.05:0.1, 1:0.07:0.02, 1:0.07:0.1, 1:0.06:0.08, or any combination thereof. Controlling the mass ratio within the above range is beneficial for preparing composite microspheres with uniform structure, high mechanical strength, and polymerization stability.

[0041] Specifically, the aforementioned acrylate monomers include butyl acrylate.

[0042] In some embodiments, the crosslinking agent includes divinylbenzene. The two C-C double bonds in the molecular structure of divinylbenzene can participate in free radical polymerization reactions, crosslinking the molecular chains of acrylate monomers into a three-dimensional network structure, thereby improving the structural stability of the ion exchange resin.

[0043] In some embodiments, the initiator comprises azobisisobutyronitrile (AIBN). AIBN decomposes at a stable rate, avoiding the problem of uneven internal structure of microspheres caused by excessively rapid local reactions, thus contributing to the obtaining of composite microspheres with uniform particle size distribution.

[0044] In some embodiments, the supporting material comprises polystyrene, the median particle size of which can be 0.45 mm to 1.25 mm, for example, 0.45 mm, 0.65 mm, 0.85 mm, 1.05 mm, 1.25 mm, or any combination thereof. Polystyrene helps improve the solvent resistance and mechanical stability of the composite microspheres, extending the service life of the ion exchange resin; and the well-developed pore structure of the polystyrene framework facilitates the grafting of subsequent functional groups and ion transport. A median particle size of not less than 0.45 mm helps reduce bed resistance during ion exchange and improves the flow efficiency of the feed solution; a median particle size of not more than 1.25 mm helps increase the specific surface area of ​​the composite microspheres, providing more ion exchange sites; controlling the median particle size of the polystyrene within the above range is beneficial for balancing the efficiency and capacity of ion exchange.

[0045] Specifically, the aforementioned polystyrene material includes polystyrene white spheres.

[0046] In some embodiments, the above-described mixing system further includes a first solvent, which includes toluene. The first solvent helps improve the uniformity of the polymerization system and avoids the problem of uneven particle size of the composite microspheres caused by excessively high local monomer concentrations.

[0047] Specifically, the mass ratio of the first solvent to the acrylate monomer is (3~6):1, for example, a range of 3:1, 4:1, 4.5:1, 5:1, 6:1 or any two of them.

[0048] In some embodiments, the preparation process of the above-mentioned mixed system includes: mixing the above-mentioned acrylate monomers, crosslinking agents, and initiators with a first solvent to obtain a first mixture; mixing the above-mentioned support material with the first mixture, and swelling for 2 h to 4 h to obtain the above-mentioned mixed system. Using the first mixture to swell the support material for a swelling time of not less than 2 h helps the acrylate monomers to fully penetrate into the pores of the support material; a swelling time of not more than 4 h helps to avoid structural deformation caused by excessive swelling of the support material and maintain its skeletal stability; controlling the swelling time within the above range is beneficial for obtaining composite microspheres with a uniform internal structure.

[0049] In some embodiments, the reaction temperature of the above polymerization reaction can be 60°C to 80°C, for example, a range of 60°C, 65°C, 70°C, 75°C, 80°C, or any combination thereof; the reaction time can be 8 h to 10 h, for example, a range of 8 h, 8.5 h, 9 h, 9.5 h, 10 h, or any combination thereof. A reaction temperature not lower than 60°C helps promote efficient polymerization; a reaction temperature not higher than 80°C helps avoid uneven microsphere structure caused by excessively rapid initiator decomposition. A reaction time not lower than 8 h helps improve monomer polymerization conversion; a reaction time not higher than 10 h helps avoid decreased porosity caused by excessive crosslinking.

[0050] Specifically, after the above-mentioned mixed system undergoes the above-mentioned polymerization reaction, a reaction mother liquor is obtained; the reaction mother liquor is washed sequentially with ethanol solution and deionized water, and then dried at 40℃~60℃ for 10 h~14 h to obtain composite microspheres.

[0051] In some embodiments, the second solvent comprises dichloroethane. The second solvent has good swelling properties and can penetrate into the three-dimensional network structure of the composite microspheres, expanding the pore volume of the microspheres; at the same time, the second solvent is miscible with the chloromethylating agent, achieving uniform dispersion of the chloromethylating agent on the surface and inside of the composite microspheres.

[0052] In some embodiments, the mass ratio of the second solvent to the composite microspheres is (2~3):1, for example, 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, 3:1, or any combination thereof. A mass ratio not lower than 2:1 helps to increase the swelling degree of the composite microspheres; a mass ratio not higher than 3:1 helps to avoid excessive dilution of the chloromethylation reagent and increase the reaction rate; controlling the mass ratio within the above range is beneficial to improving the efficiency and uniformity of the chloromethylation reaction.

[0053] In some embodiments, the chloromethylating agent includes chloroethyl ether and / or chloromethyl ether. The active chloromethyl group in the chloromethylating agent can undergo an electrophilic substitution reaction with the composite microspheres, grafting the active chloromethyl group onto the active sites on the surface and inside of the composite microspheres, providing a basis for subsequent reactions.

[0054] In some embodiments, the mass ratio of the chloromethylating agent to the composite microspheres can be (2~3):1, for example, 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, 3:1, or any combination thereof. A mass ratio of not less than 2:1 helps to increase the grafting rate of active chloromethyl groups; a mass ratio of not more than 3:1 helps to avoid excessive adsorption of the chloromethylating agent and reduces the difficulty of subsequent washing processes.

[0055] Specifically, the chloromethylation reaction described above is carried out in the presence of a catalyst.

[0056] In some embodiments, the process of mixing the composite microspheres, the second solvent, and the chloromethylating agent and then carrying out the chloromethylation reaction includes: mixing the composite microspheres, the second solvent, and the chloromethylating agent, allowing them to swell for 2-4 hours, then adding a catalyst, and then carrying out the chloromethylation reaction to obtain the composite chlorospheres; wherein the catalyst includes zinc chloride. This stepwise operation of swelling followed by catalyst addition helps increase the swelling capacity of the composite microspheres; simultaneously, zinc chloride, as a catalyst, can accept electron pairs from the chloromethylating agent molecules, activating the chloromethyl groups and making them more readily electrophilic substitution reactions with the composite microsphere matrix, significantly improving the reaction rate and group grafting rate.

[0057] Specifically, the mass ratio of the catalyst to the composite microspheres can be (0.3~0.4):1, for example, 0.3:1, 0.32:1, 0.34:1, 0.36:1, 0.38:1, 0.4:1 or any combination thereof.

[0058] In some embodiments, the reaction temperature of the above-mentioned chloromethylation reaction can be 40°C to 45°C, for example, a range of 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, or any combination thereof; the reaction time can be 8 h to 10 h, for example, a range of 8 h, 8.5 h, 9 h, 9.5 h, 10 h, or any combination thereof. A reaction temperature not lower than 40°C helps maintain the catalytic activity of zinc chloride and promotes efficient reaction; a reaction temperature not higher than 45°C helps avoid side reactions and maintain the structural stability of the composite microspheres. A reaction time not lower than 8 h helps improve the reaction conversion rate; a reaction time not higher than 10 h helps avoid structural aging of the microspheres.

[0059] Specifically, the composite microspheres, the second solvent, and the chloromethylating reagent are mixed and subjected to a chloromethylation reaction to obtain a reaction solution. The reaction solution is then washed sequentially with ethanol solution and deionized water, and dried at 40℃~60℃ for 10 h~14 h to obtain the composite chlorospheres.

[0060] In some embodiments, the ion exchange resin is an anion exchange resin, and the process of amination of the composite chloride spheres includes: mixing the composite chloride spheres with an aqueous solution containing an amination reagent and then performing the amination reaction to obtain the anion exchange resin; wherein the amination reagent includes a trimethylamine solution. The amination reagent undergoes a nucleophilic substitution reaction with the chloromethyl groups on the surface of the composite chloride spheres, thereby attaching quaternary ammonium groups to the composite chloride spheres. The quaternary ammonium groups are anion exchange active sites and can bind target anions through electrostatic adsorption.

[0061] Specifically, in the above-mentioned trimethylamine solution, the mass percentage of trimethylamine can be 30% to 40%, for example, 30%, 32%, 34%, 36%, 38%, 40%, or any combination thereof.

[0062] In some embodiments, the mass ratio of the amination reagent to the composite chlorine ball can be (2~4):1, for example, a range of 2:1, 2.5:1, 3:1, 3.5:1, 4:1, or any two of these. A mass ratio of not less than 2:1 helps to provide sufficient reagent dosage, increase the grafting rate of quaternary ammonium groups, and thus increase the anion exchange capacity; a mass ratio of not more than 4:1 helps to avoid excessive reagent, reduce washing difficulty and production costs.

[0063] In some embodiments, the reaction temperature of the above-mentioned amination reaction can be 40°C to 50°C, for example, a range of 40°C, 42°C, 44°C, 46°C, 48°C, 50°C, or any combination thereof; the reaction time can be 12 h to 24 h, for example, a range of 12 h, 15 h, 18 h, 21 h, 24 h, or any combination thereof. A reaction temperature not lower than 40°C helps to enhance the reaction rate and increase the grafting rate of quaternary ammonium groups; a reaction temperature not higher than 50°C helps to reduce the volatilization of trimethylamine and improve reagent utilization; a reaction time not lower than 12 h helps to improve the reaction conversion rate; and a reaction time not higher than 24 h helps to avoid resin structure aging caused by excessively long reaction times.

[0064] In some embodiments, the ion exchange resin is a cation exchange resin. The process of sulfonating the composite chlorine balls includes: mixing the composite chlorine balls with a third solvent, swelling for 2-4 hours, and then adding a sulfonating agent to carry out the sulfonation reaction to obtain the cation exchange resin. This process, through a stepwise approach of swelling followed by sulfonation, combined with control of the swelling time, achieves efficient and stable preparation of the cation exchange resin, while enhancing the adsorption capacity of the cation exchange resin for cationic impurities.

[0065] In some embodiments, the mass ratio of the third solvent to the composite chlorine sphere can be (2~4):1, for example, a range of 2:1, 2.5:1, 3:1, 3.5:1, 4:1, or any two of these. The addition of the third solvent allows it to penetrate into the pores of the composite chlorine sphere, causing it to swell and increasing the contact area between the sulfonating agent and the chloromethyl group. A mass ratio of not less than 2:1 helps to increase the reaction contact area; a mass ratio of not more than 4:1 helps to avoid excessive dilution of the sulfonating agent and increases the reaction rate.

[0066] Specifically, the third solvent mentioned above includes dichloroethane.

[0067] In some embodiments, the sulfonating agent includes concentrated sulfuric acid. A strong sulfonating agent can react with the chloromethyl groups on the surface of the composite chlorine ball to introduce sulfonic acid groups; these sulfonic acid groups are cation exchange active sites and can bind target cations through ion exchange.

[0068] Specifically, the mass percentage of the concentrated sulfuric acid can be 60% to 70%, for example, 60%, 62%, 64%, 66%, 68%, 70%, or any combination thereof.

[0069] In some embodiments, the mass ratio of the sulfonating agent to the composite chlorine ball can be (2~4):1, for example, a range of 2:1, 2.5:1, 3:1, 3.5:1, 4:1, or any two of these. A mass ratio of not less than 2:1 helps to provide sufficient sulfonating agent, increase the grafting rate of sulfonic acid groups, and thus increase the cation exchange capacity; a mass ratio of not more than 4:1 helps to avoid excessive corrosion by concentrated sulfuric acid and maintain the mechanical stability of the resin.

[0070] In some embodiments, the reaction temperature of the sulfonation reaction can be 80°C to 90°C, for example, a range of 80°C, 82°C, 84°C, 86°C, 88°C, 90°C, or any combination thereof; the reaction time can be 6 h to 8 h, for example, a range of 6 h, 6.5 h, 7 h, 7.5 h, 8 h, or any combination thereof. A reaction temperature not lower than 80°C helps to increase the grafting rate of sulfonic acid groups; a reaction temperature not higher than 90°C helps to prevent the detachment of sulfonic acid groups and maintain the exchange performance of the resin. A reaction time not lower than 6 h helps to increase the reaction conversion rate; a reaction time not higher than 8 h helps to prevent resin structural aging; controlling the reaction temperature and time within the above ranges is beneficial for obtaining a stable cation exchange resin.

[0071] In specific implementation, acrylate monomers, crosslinking agents, and initiators are mixed with a first solvent to obtain a first mixture; the supporting material is mixed with the first mixture, and after swelling for 2-4 hours, a mixed system is obtained; the mixed system is subjected to a polymerization reaction, filtered, and the product is washed sequentially with ethanol solution and deionized water, and dried at 40℃-60℃ for 10-14 hours to obtain composite microspheres; the composite microspheres, a second solvent, and a chloromethylating agent are mixed, swelled for 2-4 hours, then a catalyst is added, and a chloromethylation reaction is carried out; the product is filtered, washed sequentially with ethanol solution and deionized water, and dried at 40℃-60℃ for 10-14 hours to obtain composite chlorospheres; the composite chlorospheres are mixed with an aqueous solution containing an amination agent and subjected to an amination reaction; after the amination reaction, the reactants are washed repeatedly with ethanol and deionized water to obtain an anion exchange resin; the composite chlorospheres are mixed with a third solvent and swelled for 2-4 hours. h, then add sulfonating reagent to carry out sulfonation reaction, after the sulfonation reaction is completed, the reactants are serially diluted to obtain the above cation exchange resin.

[0072] The ion exchange resin prepared by the method of this invention has a three-dimensional cross-linked network structure, which helps to enhance the mechanical strength and stability of the resin and solves the problem of the easy breakage of traditional resins in aqueous systems. At the same time, the quaternary ammonium groups and sulfonic acid groups introduced through chloromethylation, amination or sulfonation reactions endow the resin with a high-efficiency adsorption capacity for anions and cations.

[0073] This invention also provides an ion exchange resin, which is prepared according to the above-described method for preparing ion exchange resin.

[0074] According to the inventors' research, the ion exchange resin has high mechanical stability and is grafted with quaternary ammonium groups or sulfonic acid groups on its surface. These groups provide active sites for ion exchange and can bind target anions or cations through electrostatic adsorption or ion exchange.

[0075] This invention also provides a purification method for diethylene terephthalate (BHET), comprising the following steps: purifying the diethylene terephthalate to be purified using a resin material to obtain purified diethylene terephthalate; wherein the resin material includes a cation exchange resin and an anion exchange resin; the anion exchange resin is prepared according to the above-described method for preparing ion exchange resins, wherein the composite chloride spheres are subjected to the above-described amination reaction to obtain the anion exchange resin; the cation exchange resin is prepared according to the above-described method for preparing ion exchange resins, wherein the composite chloride spheres are subjected to the above-described sulfonation reaction to obtain the cation exchange resin.

[0076] According to the inventor's research, a resin material composed of cation exchange resin and anion exchange resin is used. The sulfonic acid groups of the cation exchange resin can adsorb cationic impurities in the BHET to be purified, and the quaternary ammonium groups of the anion exchange resin can adsorb anionic impurities in the BHET to be purified. The two resins work synergistically to remove cationic and anionic impurities from the BHET to be purified.

[0077] Specifically, the cation exchange resin needs to be pretreated before purifying the diethylene terephthalate to be purified. The pretreatment includes the following steps: washing the cation exchange resin with HCl solution at a flow rate of 2 m / h to 4 m / h; after washing for 80 min to 100 min, continuing to wash the cation exchange resin with deionized water until the pH of the effluent is 6.5 to 7.0, thus obtaining the washed cation exchange resin.

[0078] Specifically, the mass percentage of the HCl solution can be 2% to 6%, for example, 2%, 3%, 4%, 5%, 6% or any combination thereof.

[0079] Specifically, the anion exchange resin needs to be pretreated before purifying the diethylene terephthalate to be purified. The pretreatment includes the following steps: washing the anion exchange resin with NaOH solution at a flow rate of 2 m / h to 4 m / h; after washing for 80 min to 100 min, continuing to wash the anion exchange resin with deionized water until the pH of the effluent is 7 to 7.5, thus obtaining the washed anion exchange resin.

[0080] Specifically, the mass percentage of the NaOH solution can be 2.5% to 6.5%, for example, a range of 2.5%, 3.5%, 4.5%, 5.5%, 6.5%, or any combination thereof.

[0081] In some embodiments, the diethylene terephthalate to be purified comprises crude diethylene terephthalate obtained from the alcoholysis of polyester raw materials. The crude diethylene terephthalate (BHET) obtained from the alcoholysis of the polyester raw materials contains cationic and anionic impurities. The cationic impurities include Na. + Ca 2+ Fe 2+ Fe 3+ Sb + Mg 2 + Co 2+ One or more of the above; the above anions include Cl. - SO4 2- NO3 - One or more of them.

[0082] In some embodiments, the volume ratio of the anion exchange resin to the cation exchange resin can be 1:(2~3), for example, 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3 or any combination thereof.

[0083] In some embodiments, the purification process includes: mixing the diethylene terephthalate to be purified with water to obtain an ion exchange stock solution; passing the ion exchange stock solution through an ion exchange column equipped with the resin material to obtain an ion exchange liquid; and crystallizing the ion exchange liquid to obtain the purified diethylene terephthalate. This stepwise purification method allows for the gradual removal of impurities, improving the purification accuracy of BHET; furthermore, the process is continuous, easily scaled up for industrial applications, and facilitates large-scale production.

[0084] Specifically, in the above-mentioned ion exchange stock solution, the mass percentage of diethylene terephthalate to be purified can be 5% to 15%, for example, 5%, 6%, 8%, 10%, 12%, 15%, or any combination thereof.

[0085] Specifically, the total mass of anions and cations in the above-mentioned ion exchange stock solution is less than 200 ppm.

[0086] Specifically, when the aforementioned ion exchange feed solution flows through an ion exchange column equipped with the aforementioned resin material, the temperature of the ion exchange feed solution is 60℃~70℃, for example, 60℃, 62℃, 64℃, 66℃, 68℃, 70℃, or any combination thereof. The flow rate of the aforementioned ion exchange feed solution is 4 BV / h~10 BV / h, for example, 4 BV / h, 5 BV / h, 6 BV / h, 7 BV / h, 8 BV / h, 9 BV / h, 10 BV / h, or any combination thereof.

[0087] In the specific implementation, the diethylene terephthalate to be purified is mixed with water to obtain the ion exchange stock solution; the cation exchange resin is washed with HCl solution at a flow rate of 2 m / h to 4 m / h; after washing for 80 min to 100 min, the cation exchange resin is washed again with deionized water until the pH of the effluent is 6.5 to 7.0, obtaining the washed cation exchange resin; the anion exchange resin is washed with NaOH solution at a flow rate of 2 m / h to 4 m / h; after washing for 80 min to 100 min, the anion exchange resin is washed again with deionized water until the pH of the effluent is 7 to 7.5, obtaining the washed anion exchange resin; the washed anion exchange resin and the washed cation exchange resin are mixed to obtain a mixed ion exchange column; the ion exchange stock solution is passed through the mixed ion exchange column to obtain the ion exchange solution; the ion exchange solution is crystallized to obtain the purified diethylene terephthalate (BHET premium).

[0088] The present invention will be further described below through specific embodiments.

[0089] Example 1

[0090] S1. Mix 20 g of butyl acrylate, 1.4 g of divinylbenzene, and 1.0 g of azobisisobutyronitrile with 50 g of toluene to obtain a first mixture; add 20 g of commercially available polystyrene white spheres (Suzhou Zhiyi Microsphere Technology, KBsphere) with a median particle size of 1 mm. ®1000 PS) was mixed with the first mixture and swollen at room temperature for 3 h to obtain a mixed system; the mixed system was heated to 60℃ and stirred at 150 rpm for 2.5 h; then heated to 70℃ for polymerization reaction for 4 h; then heated to 80℃ and continued to react for 2.5 h, and the reaction product was obtained by filtration; the reaction product was washed with ethanol solution and deionized water in turn, and then vacuum dried at 50℃ for 12 h to obtain composite microspheres;

[0091] S2. Mix 20 g of composite microspheres, 60 g of dichloroethane and 40 g of chloroethyl ether, and allow to swell for 3 h. Then add 6 g of zinc chloride and filter to obtain the reaction product. After the temperature of the reaction product drops to room temperature, wash the reaction product with ethanol solution and deionized water in turn, and then vacuum dry at 50 °C for 12 h to obtain composite chlorospheres.

[0092] S3. Mix 10 g of composite chlorine beads with 40 g of trimethylamine aqueous solution (the mass of trimethylamine accounts for 30% of the total mass of trimethylamine aqueous solution) and carry out an amination reaction at 45℃ and 150 rpm for 24 h. After the amination reaction is completed, wash the reactants with ethanol and deionized water several times in sequence to obtain anion exchange resin.

[0093] S4. Mix 10 g of composite chlorine balls with 30 g of dichloroethane, allow to swell for 2 h, then slowly add 20 g of concentrated sulfuric acid solution (the mass of concentrated sulfuric acid accounts for 60% of the total mass of concentrated sulfuric acid solution), and carry out sulfonation reaction at 85℃ for 7 h to obtain reaction solution; cool the reaction solution to room temperature, and after gradient dilution, obtain cation exchange resin.

[0094] S5. Wash the cation exchange resin with HCl solution (4% by mass) at a flow rate of 3 m / h. After washing for 90 min, continue washing the cation exchange resin with deionized water until the pH of the effluent is 7.0, obtaining the washed cation exchange resin. Wash the anion exchange resin with NaOH solution (3.5% by mass) at a flow rate of 3 m / h. After washing for 90 min, continue washing the anion exchange resin with deionized water until the pH of the effluent is 7.5, obtaining the washed anion exchange resin.

[0095] S6. Pour the crude BHET crystals obtained after alcoholysis of polyester raw material into a dissolving tank, add deionized water, and obtain a BHET ion exchange stock solution with a mass percentage of 10%; the total mass of anions and cations in the BHET ion exchange stock solution is 180 ppm; control the temperature of the BHET ion exchange stock solution at 65℃.

[0096] S7. A 100 mL mixed ion exchange column is prepared by packing cation exchange resin and anion exchange resin at a volume ratio of 1:2.5. Then, the BHET ion exchange stock solution is flowed through the mixed ion exchange column at a flow rate of 6 BV / h to obtain an ion exchange solution. The total mass of anions and cations in the ion exchange solution is 10 ppm. The ion exchange solution is then crystallized to obtain BHET premium product.

[0097] The purity of the BHET concentrate obtained in Example 1 was 99.45%, the L value was 99.2, the a value was 0.1, the b value was 0.4, the mass of the hydrolysis byproduct accounted for 0.44% of the total mass of the BHET concentrate, and the exchange ratio was 500 BV (the exchange ratio refers to the total volume of BHET ion exchange stock solution that the ion exchange resin provided by the present invention can stably process before the ion exchange capacity reaches saturation, which can reach 500 times the volume of the mixed ion exchange column).

[0098] The performance of the BHET products prepared in the examples and comparative examples was determined using the following methods:

[0099] (1) Determination of L value, a value and b value of BHET high-quality solid crystals

[0100] Calibrate the colorimeter (ColorFlex EZ); place the BHET sample into the colorimeter's sample chamber, perform color value detection, and record the measured L, a, and b values.

[0101] (2) Determination of the content of hydrolysis byproducts

[0102] The content of hydrolysis byproducts was determined by high-performance liquid chromatography (Agilent 1260 Infinity II). A test solution containing the BHET premium sample was prepared, and a standard curve was plotted using hydrolysis byproduct standards such as terephthalic acid and monohydroxyethyl terephthalate. A C18 column was used with methanol-phosphate buffer solution as the mobile phase, and gradient elution was performed at a detection wavelength of 240 nm. The mass of each hydrolysis byproduct in the test solution was quantitatively determined by the external standard method, and the percentage of total hydrolysis byproduct mass to the total mass of the BHET premium sample was calculated.

[0103] (3) Determination of the exchange ratio

[0104] The column-based dynamic exchange method was used for determination. The ion exchange resin provided by this invention was uniformly packed into an ion exchange column, and the actual column volume (BV) after resin packing was calibrated. The BHET ion exchange stock solution from an aqueous system was continuously passed through the exchange column for ion exchange. Samples were periodically taken to detect the content of anions and cations in the effluent. When the impurity content in the effluent reached the preset ion exchange breakthrough threshold, the injection was stopped. The total volume of BHET ion exchange stock solution treated was calculated, and the exchange ratio was determined. Exchange ratio = Total volume of stock solution treated / Resin-packed column volume (BV).

[0105] The difference between Examples 2 to 6 and Example 1 is that the amount of supporting material added is different, while other reaction conditions remain the same. See Table 1 for details.

[0106] The difference between Examples 7 to 9 and Example 1 is that the amounts of acrylate monomers, crosslinking agents, and initiators added are different, while other reaction conditions remain unchanged. See Table 1 for details.

[0107] The difference between Examples 10-12 and Example 1 is that the amount of chloromethylating agent added is different, while other reaction conditions remain the same. See Table 1 for details.

[0108] The difference between Examples 13 and 14 and Example 1 is that the amount of amination reagent added is different, while other reaction conditions remain the same. See Table 1 for details.

[0109] The difference between Examples 15-17 and Example 1 is that the amount of sulfonating agent added is different, while other reaction conditions remain the same, as detailed in Table 1.

[0110] The difference between Example 18 and Example 1 is that in step S7: the BHET ion exchange stock solution is flowed sequentially through a cation exchange resin column and an anion exchange resin column at a flow rate of 6 BV / h to obtain an ion exchange solution; the ion exchange solution is then crystallized to obtain high-quality BHET.

[0111] The difference between Example 19 and Example 1 is that in step S2: 20 g of composite microspheres, 60 g of dichloroethane, 40 g of chloroethyl ether and 6 g of zinc chloride are mixed evenly and swollen for 3 h. The mixture is then subjected to a chloromethylation reaction at 45 °C and 150 rpm for 9 h of stirring to obtain a reaction solution. The temperature of the reaction solution is then lowered to room temperature, and the reaction solution is washed sequentially with ethanol solution and deionized water. Finally, it is vacuum dried at 50 °C for 12 h to obtain composite chlorospheres.

[0112] The difference between Comparative Example 1 and Example 1 is that no supporting material was added in step S1, while other reaction conditions remained unchanged, as detailed in Table 1.

[0113] The difference between Comparative Example 2 and Example 1 is that no acrylate monomers were added in step S1, while other reaction conditions remained unchanged, as detailed in Table 1.

[0114] The difference between Comparative Example 3 and Example 1 is that no crosslinking agent was added in step S1, while other reaction conditions remained unchanged, as detailed in Table 1.

[0115] The difference between Comparative Example 4 and Example 1 is that no initiator was added in step S1, while other reaction conditions remained unchanged, as detailed in Table 1.

[0116] The difference between Comparative Example 5 and Example 1 is that no chloromethylating agent was added in step S1, while other reaction conditions remained unchanged, as detailed in Table 1.

[0117] Table 1

[0118]

[0119] Table 2

[0120]

[0121] As shown in Table 2, the ion exchange resin provided by this invention has advantages such as high mechanical strength and strong adsorption capacity. Compared with Comparative Examples 1 to 5, the ion exchange resins prepared in Examples 1 to 19, when applied to the purification of diethylene glycol terephthalate (DET), yielded BHET with a purity of not less than 99.29%, a hydrolysis byproduct content ≤0.61%, and an exchange ratio as high as 530 BV. However, Comparative Examples 1 to 5, lacking core components such as supporting materials, acrylate monomers, crosslinking agents, initiators, or chloromethylating agents, could not form a complete three-dimensional crosslinked network and effective ion exchange sites. Consequently, the mechanical strength and adsorption performance of the resins decreased significantly, the BHET purity was generally lower than that of Examples 1 to 19, the hydrolysis byproduct content was higher, and the exchange ratio was only in the range of 220 BV to 260 BV, far inferior to the examples. The comparative results fully demonstrate that the core preparation process can effectively construct a stable crosslinked structure and introduce ion-exchange active groups, fundamentally solving the technical defects of traditional resins such as easy breakage, low ion exchange efficiency, and easy generation of hydrolysis byproducts.

[0122] Internal comparisons of the examples show that the tandem resin column process in Example 18 and the catalyst-pre-addition method for chloromethylation in Example 19 both resulted in a decrease in purification efficiency and exchange fold. This indicates that limiting the raw material ratio and reaction conditions can precisely control the resin structure and the grafting rate of active groups, achieving a synergistic improvement in purity, byproduct control, and treatment efficiency.

[0123] In summary, the ion exchange resin prepared by the method of this invention has advantages such as high mechanical strength and strong adsorption capacity. When applied to the purification of diethylene terephthalate, it can operate stably in an aqueous system, reduce the generation of hydrolysis byproducts, and significantly improve product purity, thus strongly supporting the industrial purification of waste polyester alcoholysis products.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an ion exchange resin, characterized in that, Includes the following steps: A polymerization reaction is carried out on a mixture including a support material, acrylate monomers, a crosslinking agent, and an initiator to obtain composite microspheres; The composite microspheres, the second solvent, and the chloromethylating agent were mixed and then subjected to a chloromethylation reaction to obtain composite chlorospheres. The composite chloride spheres are subjected to an amination or sulfonation reaction to obtain the ion exchange resin; The mass ratio of the supporting material to the acrylate monomer is (1~1.8):1, and the mass ratio of the chloromethylating agent to the composite microspheres is (2~3):

1.

2. The method for preparing the ion exchange resin according to claim 1, characterized in that, The mass ratio of the acrylate monomer, the crosslinking agent, and the initiator is 1:(0.05~0.07):(0.02~0.1). And / or, the crosslinking agent includes divinylbenzene; And / or, the initiator includes azobisisobutyronitrile; And / or, the support material includes polystyrene material, wherein the median particle size of the polystyrene material is 0.45 mm to 1.25 mm.

3. The method for preparing the ion exchange resin according to claim 1 or 2, characterized in that, The mixed system further includes a first solvent, which includes toluene; And / or, the preparation process of the mixed system includes: mixing the acrylate monomer, crosslinking agent and initiator with a first solvent to obtain a first mixture; mixing the support material with the first mixture, and swelling for 2 h to 4 h to obtain the mixed system; And / or, the polymerization reaction is carried out at a temperature of 60°C to 80°C for a reaction time of 8 h to 10 h.

4. The method for preparing the ion exchange resin according to claim 1, characterized in that, The second solvent includes dichloroethane; And / or, the mass ratio of the second solvent to the composite microspheres is (2~3):1; And / or, the chloromethylating agent includes chloroethyl ether and / or chloromethyl ether.

5. The method for preparing the ion exchange resin according to claim 1 or 4, characterized in that, The process of mixing the composite microspheres, the second solvent, and the chloromethylating agent and then carrying out the chloromethylation reaction includes: mixing the composite microspheres, the second solvent, and the chloromethylating agent, allowing them to swell for 2 h to 4 h, then adding a catalyst, and then carrying out the chloromethylation reaction to obtain the composite chlorospheres; wherein the catalyst includes zinc chloride; And / or, the chloromethylation reaction is carried out at a temperature of 40°C to 45°C for a time of 8 h to 10 h.

6. The method for preparing the ion exchange resin according to claim 1, characterized in that, The ion exchange resin is an anion exchange resin. The process of amination of the composite chloride beads includes: mixing the composite chloride beads with an aqueous solution containing an amination reagent and then carrying out the amination reaction to obtain the anion exchange resin; wherein: The amination reagent includes trimethylamine; And / or, the mass ratio of the amination reagent to the composite chlorine ball is (2~4):1; And / or, the amination reaction is carried out at a temperature of 40°C to 50°C for a reaction time of 12 h to 24 h.

7. The method for preparing the ion exchange resin according to claim 1, characterized in that, The ion exchange resin is a cation exchange resin. The process of sulfonating the composite chloride spheres includes: mixing the composite chloride spheres with a third solvent, allowing them to swell for 2-4 hours, and then adding a sulfonating agent to carry out the sulfonation reaction to obtain the cation exchange resin; wherein... The mass ratio of the third solvent to the composite chlorine ball is (2~4):1; And / or, the sulfonating agent includes concentrated sulfuric acid; And / or, the mass ratio of the sulfonating agent to the composite chlorine ball is (2~4):1; And / or, the sulfonation reaction is carried out at a temperature of 80°C to 90°C for a time of 6 h to 8 h.

8. An ion exchange resin, characterized in that, It is prepared according to the preparation method of the ion exchange resin according to any one of claims 1-7.

9. A method for purifying diethylene terephthalate, characterized in that, Includes the following steps: Diethylene terephthalate to be purified is purified using resin materials to obtain purified diethylene terephthalate; wherein, the resin materials include cation exchange resin and anion exchange resin. The anion exchange resin is prepared according to the preparation method of the ion exchange resin according to any one of claims 1-6, wherein the composite chloride spheres are subjected to the amination reaction to obtain the anion exchange resin; The cation exchange resin is prepared according to the preparation method of the ion exchange resin according to any one of claims 1-5 and 7, wherein the composite chloride spheres are subjected to the sulfonation reaction to obtain the cation exchange resin.

10. The purification method for diethylene terephthalate according to claim 9, characterized in that, The diethylene terephthalate to be purified includes crude diethylene terephthalate obtained from polyester raw materials through alcoholysis. And / or, the volume ratio of the anion exchange resin to the cation exchange resin is 1:(2~3). And / or, the purification process includes: mixing the diethylene terephthalate to be purified with water to obtain an ion exchange stock solution; passing the ion exchange stock solution through an ion exchange column equipped with the resin material to obtain an ion exchange liquid; and crystallizing the ion exchange liquid to obtain the purified diethylene terephthalate.

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