An adsorption resin and a method for preparing the same

Abstract

The application belongs to the field of high polymer materials, and particularly relates to a kind of adsorption resin and its preparation method.The method comprises the following steps: 1) dissolving rosin-based multi-double bond crosslinking agent, vinyl functional monomer and oil-soluble initiator in hydrophobic organic solvent to form a uniform oil phase; 2) dissolving water-soluble electrolyte in deionized water to form an aqueous phase liquid; 3) under stirring conditions, continuously adding the aqueous phase obtained in step 2) to the oil phase obtained in step 1), and forming a stable water-in-oil high internal phase emulsion by high-speed emulsification; 4) performing thermal initiation polymerization on the emulsion obtained in step 3), and after the reaction is completed, the adsorption resin is obtained by solvent extraction and drying. The application uses high internal phase emulsion template method combined with rosin-based three-functionality crosslinking agent to construct three-dimensional through super-pore structure in one step, realize in-situ covalent anchoring of functional groups, significantly improve mass transfer efficiency compared with traditional methods, and the process is green and simple. Moreover, selective adsorption customization can be realized by replacing functional monomers.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, specifically relating to an adsorption resin and its preparation method. Background Technology

[0002] Adsorption resins are important separation and purification materials, and their core performance lies in their high specific surface area and suitable pore structure. Traditional macroporous adsorption resins mostly adopt suspension polymerization, using inert solvents as porogens. The resulting pores are mostly non-penetrating "ink bottle" pores with a wide pore size distribution and high mass transfer resistance, which limits their efficiency when processing high flow rates or large molecular pollutants.

[0003] Rosin, as a renewable biomass resource, is being explored for use in the synthesis of more environmentally friendly adsorption resins. Existing technology (CN110845660A) discloses a rosin-based anionic macroporous adsorption resin, which uses ethylene glycol propylene-piperidine acrylate as a crosslinking agent and dimethylaminoethyl methacrylate as a monomer. The resin is obtained through traditional suspension polymerization and complex post-modification (methylation and alkalization) to form a quaternary ammonium base resin. This method has the following drawbacks: 1) Limited pore structure: The resulting resin has a low average pore size within the mesoporous range and a low specific surface area, which is not conducive to the rapid diffusion of macromolecules; 2) Complex process: It requires two steps of methylation and alkalization after polymerization, resulting in a long process, high energy consumption, and the toxicity of the reagent iodomethane; 3) Single function and post-introduction: The functional groups are introduced through post-modification, which may lead to uneven distribution or weak bonding.

[0004] The high internal phase emulsion template method is an advanced technique for preparing macroporous polymer monolithic materials with highly interconnected and uniform pore sizes. Using an emulsion with an internal phase volume fraction greater than 74% as a template, the continuous phase is polymerized, and then the internal phase is removed to replicate the interconnected macroporous structure. This method allows for precise control of pore size, porosity, and connectivity. However, research combining the high internal phase emulsion template method with bio-based rosin raw materials for the one-step preparation of in-situ functionalized adsorption resins has not yet been reported.

[0005] Therefore, developing a novel adsorption resin that combines the green advantages of rosin-based raw materials, the structural advantages of the HIPE method, and the advantages of in-situ functionalization process is of great significance for overcoming the bottlenecks in mass transfer efficiency and preparation process of existing adsorption materials. Summary of the Invention

[0006] The present invention addresses the technical problems of existing rosin-based adsorption resins, such as small pore size, slow mass transfer, complex post-modification process, and outdated methods for introducing functional groups, by providing an adsorption resin and its preparation method.

[0007] The main objective of this invention is: I. An adsorption resin with a highly interconnected three-dimensional through-pore structure is provided, which can greatly reduce mass transfer resistance and improve adsorption kinetics performance. II. A preparation method is provided, which abandons the traditional post-modification process and achieves in-situ, uniform and stable introduction of functional groups through monomer copolymerization. The process is simple and green. 3. To provide an adsorption resin whose raw materials are partially or wholly derived from renewable rosin derivatives, and which has both good mechanical strength and thermal stability.

[0008] To achieve the above objectives, the present invention adopts the following technical solution. A method for preparing an adsorption resin, The method is based on a one-step polymerization of water-in-oil emulsions with high internal phase, and specifically includes: 1) A rosin-based multi-double bond crosslinking agent, a vinyl functional monomer, and an oil-soluble initiator are dissolved in a hydrophobic organic solvent to form a homogeneous oil phase; 2) Dissolve the water-soluble electrolyte in deionized water to form an aqueous phase solution; 3) Under stirring conditions, the aqueous phase obtained in step 2) is continuously added to the oil phase obtained in step 1), and a stable water-in-oil emulsion with high internal phase is formed through high-speed emulsification; 4) The emulsion obtained in step 3) is subjected to a thermally initiated polymerization reaction. After the reaction is completed, it is extracted with solvent and dried to obtain the adsorption resin.

[0009] As a preferred option Step 1) The rosin-based multi-double-bond crosslinking agent is a rosin derivative containing two or three polymerizable double bonds; Step 1) The vinyl functional monomer is a vinyl monomer containing carboxyl groups and / or sulfonic acid groups and / or hydroxyl groups; Step 1) The oil-soluble initiator is benzoyl peroxide or azobisisobutyronitrile; Step 1) The hydrophobic organic solvent is toluene and / or xylene and / or n-heptane and / or cyclohexane; The mass percentages of each component in step 1) are as follows: 30-50% rosin-based double bond crosslinking agent, 8-18% vinyl functional monomer, 0.5-2.5% oil-soluble initiator, and the balance being a hydrophobic organic solvent.

[0010] As a preferred option The rosin-based multi-double bond crosslinking agent is fumarate-piperidine glycol trimethacrylate; The vinyl functional monomer is methacrylic acid and / or acrylic acid and / or 2-acrylamide-2-methylpropanesulfonic acid and / or hydroxyethyl methacrylate.

[0011] As a preferred option Step 2) The water-soluble electrolyte is sodium chloride; Step 2) The mass concentration of the water-soluble electrolyte in deionized water is 2.0%–3.0%. When the NaCl concentration is below 2.0%, the ionic strength of the aqueous phase is insufficient, the electric double-layer repulsion between droplets is large, and the emulsion is prone to coalescence and stratification. When the concentration is above 3.0%, the excessively high ionic strength leads to a significant increase in the viscosity of the aqueous phase, and may also trigger a "salting out" effect that damages the hydration layer of the emulsifier, resulting in increased droplet deformation and coalescence during emulsification, ultimately leading to smaller pore sizes and wider distribution. Within the range of 2.0%–3.0%, the ionic strength is sufficient to shield the electrostatic repulsion between droplets, and the viscosity of the aqueous phase is moderate, which is beneficial for obtaining stable HIPE with uniform droplet size.

[0012] As a preferred option Step 2) The aqueous phase is added with an oil-soluble emulsifier, sorbitan monooleate, at a concentration of 0-0.5% of the total mass of the aqueous phase.

[0013] As a preferred option Step 3) The volume ratio of the aqueous phase to the oil phase is (3-5):1; Step 3) The high-speed emulsification is carried out at a stirring speed of 2000-4000 rpm and an ambient temperature of 20-30 ℃ for 20-50 min.

[0014] As a preferred option Step 4) The thermally initiated polymerization reaction is carried out under a nitrogen atmosphere, using a staged temperature control program that matches the kinetics of high internal phase emulsion polymerization: firstly, the reaction is carried out at 60-65 °C for 4-8 h, and then the temperature is lowered to 55-58 °C to continue the reaction for 16-30 h, with a total reaction time of 24-36 h.

[0015] As a preferred option Step 4) The solvent extraction involves sequentially extracting the polymerization product with ethanol or methanol and deionized water using a Soxhlet extraction method for 24–48 h. Step 4) involves drying the product in a vacuum oven at a temperature of 60–80 °C until it reaches a constant weight.

[0016] An adsorbent resin.

[0017] This invention provides a high-performance adsorption resin with a three-dimensional through-hole structure and in-situ bonded functional groups, which is formed in one step using a high internal phase emulsion template method with a rosin-based multifunctional crosslinking agent as the core and a rosin-based multifunctional crosslinking agent as the core. The resin is characterized by a three-dimensional through-hole structure and in-situ bonded functional groups.

[0018] This invention addresses the problems of poor pore connectivity, low mass transfer efficiency, complex post-modification processes, and insufficient performance of bio-based raw materials in existing adsorption resin synthesis technologies. It provides a structured preparation strategy based on a high internal phase emulsion template method. This strategy utilizes a stable water-in-oil high internal phase emulsion as a reaction template and structural blueprint to achieve in-situ simultaneous construction of a functionalized rosin-based polymer network within pre-defined pores, thereby obtaining an adsorption material with interconnected macropores, high functional group loading, and excellent stability.

[0019] The core of this invention lies in constructing and precisely controlling an irreversible process of "template-guided in-situ polymerization-structure locking." The core of this process is the formation and stabilization of a water-in-oil emulsion with a water volume fraction strictly exceeding 74%. In this emulsion, aqueous droplets stabilized by surface-active components (provided by functional monomers and rosin derivatives, along with selectively added emulsifiers) are tightly packed together, compressing each other to form a polyhedral structure, constituting the "negative template" for continuous phase (oil phase) polymerization. The polymerization reaction does not occur simply as monomer solidification, but rather, at this highly ordered microscopic liquid-liquid interface, triggered by an initiator, the rosin-based crosslinking agent copolymerizes with the vinyl functional monomer, thereby "freezing" the microstructure of the emulsion and transforming it into a permanent polymer macroporous framework. Functional groups are directly anchored to the pore wall surface through covalent bonds during this process.

[0020] The key innovation of this scheme lies in integrating the formation of the pore structure and the formation of the functional network in both time and space. Template formation is a prerequisite: only under specific emulsification intensities, temperatures, and internal phase volume fractions can a stable, uniformly sized aqueous droplet emulsion with a high internal phase be formed, which is the foundation for obtaining regular, interconnected macropores. Any parameters deviating from this range may lead to emulsion instability, phase separation, or uneven pore size, thus failing to replicate the target pore structure. In-situ copolymerization is the core: the polymerization reaction must be initiated and completed at a mild temperature within the stable existence time of the emulsion template. Premature or delayed polymerization will damage the template or cause structural collapse. The introduction of rosin-based multi-double-bond crosslinking agents not only provides a bio-based source, but their rigid tricyclic diterpenoid skeleton and high double-bond density ensure that the polymer network possesses sufficient mechanical strength while forming a macroporous structure. Compared with flexible petroleum-based crosslinking agents (such as divinylbenzene), the trifunctional rosin-based crosslinking agent used in this invention enhances performance through a dual mechanism: firstly, its rigid skeleton structure itself has a high glass transition temperature (Tg); secondly, the trifunctional design forms a denser crosslinking network. The high crosslinking density significantly reduces the average molecular weight between crosslinking points. Through the synergistic effect of the rigid skeleton and high-density crosslinking, the freedom of chain segment movement is restricted, while also inhibiting chain segment slippage during thermal degradation. Therefore, the material exhibits higher thermal stability and mechanical strength. Simultaneously, the trifunctional design ensures the formation of a high-density crosslinking network. Compared to bifunctional crosslinking agents, trifunctional monomers do tend to cause early gelation in conventional bulk polymerization. However, in the water-in-oil HIPE system of this invention, firstly, the crosslinking agent in the continuous phase (oil phase) is physically separated by the internal phase droplets, effectively "diluting" its concentration. The polymerization reaction mainly occurs at the liquid-liquid interface, forming an interfacial polymer layer rather than a bulk gel. Secondly, the aqueous droplets specifically introduced in this invention as "physical crosslinking points" also limit the unlimited growth of the polymer network. Therefore, the trifunctional crosslinking agent in this specific system provides both high crosslinking density and a rigid framework while maintaining processability. The covalent anchoring of functional groups is an advantage: as a copolymer component, the vinyl functional monomer's double bonds directly participate in network formation, resulting in a uniform and stable distribution of functional groups such as carboxyl and sulfonic acid groups on the inner surface of the large pore walls, avoiding the problems of uneven distribution, low loading, and easy detachment caused by post-modification methods.

[0021] Meanwhile, from the perspective of material formation mechanism, the preparation process of this invention is a structural transformation from a "dynamic emulsion template" to a "rigid polymer replica." The size and stacking mode of the aqueous droplets directly determine the final pore size and porosity; the composition and degree of crosslinking of the monomers in the oil phase determine the chemical properties and mechanical strength of the pore walls. The synergy and locking of these three elements (template, crosslinking network, and functional groups) make the structure and properties of the final resin highly predictable and controllable.

[0022] The thermally initiated polymerization reaction involved in this invention employs a staged temperature control program. Its principle is based on the unique kinetic characteristics and structural molding requirements of high internal phase emulsion polymerization systems, aiming to synergistically achieve the two core objectives of "precise replication of the template structure" and "deep curing of the polymer network." The first stage is the high-temperature stage, where the main functions are to rapidly initiate the reaction and achieve structural stabilization. Utilizing the high decomposition activity of the initiator within this temperature range, the polymerization reaction is rapidly initiated within the critical time window after emulsion preparation. The rapidly growing polymer chains cause a sharp increase in the system viscosity, quickly surpassing the gel point, thereby "fixing" the tightly packed aqueous droplet morphology in the water-in-oil emulsion with high internal phase density, achieving the replication from a "dynamic emulsion template" to a "rigid polymer skeleton." This stage is crucial for obtaining a uniform, highly interconnected three-dimensional macroporous structure.

[0023] The second stage is the low-temperature stage, whose main functions are diffusion control and network maturation. With the primary network framework already formed and the template structure locked, it promotes the full reaction of residual monomers to achieve high conversion rates and high uniformity of the network. After gelation, the polymerization rate is controlled by the diffusion process of monomers and free radicals within the polymer network. Appropriately lowering the temperature slows down the ineffective consumption of initiators, preventing insufficient reaction kinetics due to premature initiator depletion. It also creates a mild thermal environment, which is conducive to the migration and full reaction of larger molecular weight, slowly diffusing rosin-based crosslinking agents and functional monomers to active sites, thereby increasing the crosslinking density and functional group anchoring strength of the final network. Simultaneously, it reduces thermal stress, protects the formed macroporous structure from damage, and ensures the mechanical integrity of the material.

[0024] This phased temperature control strategy effectively resolves the surface contradiction between "short initiator half-life" and "long reaction time required for structure replication" faced by isothermal polymerization in high internal phase emulsion systems. It is a necessary process to achieve the resin of this invention with ideal through-pore structure, excellent mechanical strength and high thermal stability.

[0025] Furthermore, this method is carried out entirely in an aqueous phase, avoiding the use of large amounts of organic porogens; polymerization and functionalization are completed in one step, resulting in a simple process; the rosin-based raw material used is renewable, aligning with the development direction of green chemistry. The entire reaction condition is mild and controllable, and the emulsion system exhibits good fluidity, making it easily adaptable to continuous production equipment.

[0026] The beneficial effects of this invention are: This invention employs a high internal phase emulsion template method combined with a rosin-based trifunctional crosslinking agent to construct a three-dimensional interconnected ultraporous structure in one step, achieving in-situ covalent anchoring of functional groups. Furthermore, through staged temperature control of "medium-temperature setting + low-temperature curing," a high-performance adsorption resin with a porosity >80%, compressive strength of 4-7 MPa, and thermogravimetric temperature >285 ℃ is obtained. Compared with traditional methods, the mass transfer efficiency is improved by 3 to 5 times. The process is green and simple, and selective adsorption can be customized by changing the functional monomers. Detailed Implementation

[0027] The present invention will be further described clearly and in detail below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0028] Unless otherwise specified, all raw materials used in the embodiments of the present invention are commercially available or obtainable by those skilled in the art; unless otherwise specified, all methods used in the embodiments of the present invention are methods mastered by those skilled in the art.

[0029] Example 1 A method for preparing an adsorption resin, The method is characterized in that it is a one-step polymerization method based on water-in-oil emulsion with high internal phase, and the method includes: 1) Dissolve 30% fumarate-piperazine glycol methacrylate, 8% methacrylic acid, and 0.5% benzoyl peroxide in toluene by mass percentage, with the remaining mass percentage of toluene being 61.5%, and stir to form a homogeneous oil phase.

[0030] 2) Dissolve sodium chloride in deionized water at a mass concentration of 2.0% to form a homogeneous aqueous phase. No water-soluble co-emulsifiers are added.

[0031] 3) Under the conditions of stirring speed of 2000 rpm and ambient temperature of 20 ℃, the aqueous phase obtained in step 2) is continuously added to the oil phase obtained in step 1) at a volume ratio of water phase to oil phase of 3:1, and emulsified for 20 min under these conditions to form a stable water-in-oil type high internal phase emulsion. However, in this embodiment, the surface activity of fumarate ethylene glycol trimethacrylate molecules is used to form self-emulsification under specific high shear conditions, but the stability is relatively limited, so subsequent operations need to be performed immediately.

[0032] 4) The emulsion obtained in step 3) was first reacted at 60 °C for 6 h under a nitrogen atmosphere, and then the temperature was adjusted to 55 °C and the reaction continued for 30 h, for a total reaction time of 36 h. After the reaction, the resulting polymer material was subjected to Soxhlet extraction with ethanol and deionized water for 48 h in sequence, and then dried to constant weight in a vacuum oven at 60 °C to obtain carboxyl-functionalized rosin-based macroporous adsorption resin, labeled as RB-1.

[0033] The materials prepared in the examples were subjected to performance testing. The pore structure was characterized by mercury intrusion porosimetry and nitrogen adsorption-desorption; the chemical structure was analyzed by Fourier transform infrared spectroscopy; the adsorption performance was evaluated by static adsorption experiments (using crystal violet as a model); the thermal stability was determined by thermogravimetric analysis; and the mechanical strength was measured by a particle strength tester. The characterization results are shown in the table below.

[0034] Analysis of the above characterization results shows that the adsorption resin RB-1 prepared in this example has significant performance advantages. Its most probable pore size reaches 22.0 μm, indicating the formation of a highly interconnected macroporous structure within the material. This provides efficient channels for mass transfer, greatly shortening the adsorption equilibrium time. The porosity is as high as 81.5%, with a binding capacity of 165.5 μm. 2 The BET specific surface area of ​​ / g further confirms that the material maintains a large specific surface area while ensuring high porosity, which is beneficial for improving adsorption capacity. Furthermore, the 1715 cm⁻¹ in the Fourier transform infrared spectrum... -1 The strong absorption peaks that appear clearly indicate that carboxyl functional groups have been successfully and uniformly introduced onto the material surface.

[0035] Static adsorption experiments showed that the resin achieved 90% adsorption of crystal violet in just 50 minutes, with a saturated adsorption capacity as high as 305.4 mg / g. This data is significantly superior to adsorbents prepared by traditional post-modification methods, demonstrating the advantages of in-situ functionalization in improving the uniformity of functional group distribution and loading. Thermogravimetric analysis showed that the material's 5% thermal weight loss temperature reached 285.6 ℃, exhibiting good thermal stability and adaptability to a wide operating temperature range. Mechanical property test results were equally satisfactory, with a radial compressive strength of 4.1 MPa, indicating that the material has strong resistance to deformation in practical applications and can withstand certain operating pressures.

[0036] Example 2 A method for preparing an adsorption resin, The method is characterized in that it is a one-step polymerization method based on water-in-oil emulsion with high internal phase, and the method includes: 1) Dissolve 40% fumarate-piperazine glycol methacrylate, 13% methacrylic acid, and 1.5% benzoyl peroxide in toluene by mass percentage, with the remaining mass percentage of toluene being 45.5%, and stir to form a homogeneous oil phase.

[0037] 2) Dissolve sodium chloride in deionized water at a mass concentration of 2.5%, and add 0.25% of dehydrated sorbitan monooleate by mass of the total aqueous phase to form an aqueous phase.

[0038] 3) Under the conditions of stirring speed of 3000 rpm and ambient temperature of 25 ℃, the aqueous phase liquid obtained in step 2) is continuously added to the oil phase obtained in step 1) at a volume ratio of aqueous phase liquid to oil phase of 4:1, and emulsified for 35 min under these conditions to form a stable water-in-oil type high internal phase emulsion.

[0039] 4) The emulsion obtained in step 3) was first reacted at 62 °C for 6 h under a nitrogen atmosphere, and then the temperature was adjusted to 57 °C and the reaction continued for 24 h, for a total reaction time of 30 h. After the reaction, the resulting polymer material was subjected to Soxhlet extraction with ethanol and deionized water for 36 h in sequence, and then dried to constant weight in a vacuum oven at 70 °C to obtain carboxyl-functionalized rosin-based macroporous adsorption resin, labeled as RB-2.

[0040] The materials prepared in the examples were subjected to performance testing. The pore structure was characterized by mercury intrusion porosimetry and nitrogen adsorption-desorption; the chemical structure was analyzed by Fourier transform infrared spectroscopy; the adsorption performance was evaluated by static adsorption experiments (using crystal violet as a model); the thermal stability was determined by thermogravimetric analysis; and the mechanical strength was measured by a particle strength tester. The characterization results are shown in the table below.

[0041] Analysis of the above characterization results shows that the most probable pore size in this example is 15.0 μm, with a porosity as high as 87.2%, and a binding density of 220.8 μm. 2 The BET specific surface area of ​​ / g indicates that the material forms an ideal porous structure that combines excellent connectivity and high specific surface area. Fourier transform infrared spectroscopy at 1715 cm⁻¹... -1 The strong absorption peak at the point confirms the efficient introduction of the carboxyl group.

[0042] Of particular note is its adsorption performance, achieving 90% adsorption of crystal violet in just 35 minutes, with a saturated adsorption capacity as high as 380.3 mg / g. These two key indicators are the best among the three, fully verifying the decisive role of optimized formulation and process conditions in improving adsorption kinetics and capacity. Simultaneously, the material maintains excellent thermal stability and mechanical strength.

[0043] Example 3 A method for preparing an adsorption resin, The method is characterized in that it is a one-step polymerization method based on water-in-oil emulsion with high internal phase, and the method includes: 1) Dissolve 50% fumarate-piperazine glycol methacrylate, 18% methacrylic acid, and 2.5% benzoyl peroxide in toluene by mass percentage, with the remaining mass percentage of toluene being 29.5%, and stir to form a homogeneous oil phase.

[0044] 2) Dissolve sodium chloride in deionized water at a mass concentration of 3.0%, and add 0.50% of dehydrated sorbitan monooleate by mass of the total aqueous phase to form an aqueous phase.

[0045] 3) Under the conditions of stirring speed of 4000 rpm and ambient temperature of 30 ℃, the aqueous phase liquid obtained in step 2) is continuously added to the oil phase obtained in step 1) at a volume ratio of aqueous phase liquid to oil phase of 5:1, and emulsified for 50 min under these conditions to form a stable water-in-oil type high internal phase emulsion.

[0046] 4) The emulsion obtained in step 3) was first reacted at 65 °C for 4 h under a nitrogen atmosphere, and then the temperature was adjusted to 58 °C and the reaction continued for 20 h, for a total reaction time of 24 h. After the reaction, the resulting polymer material was subjected to Soxhlet extraction with ethanol and deionized water for 24 h in sequence, and then dried to constant weight in a vacuum oven at 80 °C to obtain carboxyl-functionalized rosin-based macroporous adsorption resin, labeled as RB-3.

[0047] The materials prepared in the examples were subjected to performance testing. The pore structure was characterized by mercury intrusion porosimetry and nitrogen adsorption-desorption; the chemical structure was analyzed by Fourier transform infrared spectroscopy; the adsorption performance was evaluated by static adsorption experiments (using crystal violet as a model); the thermal stability was determined by thermogravimetric analysis; and the mechanical strength was measured by a particle strength tester. The characterization results are shown in the table below.

[0048] Analysis of the characterization results shows that this example possesses a high water-to-oil ratio and emulsification strength, resulting in a smaller most probable pore size while maintaining high porosity and a good specific surface area. The extremely high crosslinking agent content significantly enhances the bulk properties of the material, with a 5% thermogravimetric temperature reaching 321.4 ℃ and a radial compressive strength as high as 7.2 MPa, both of which are the best among the three, demonstrating excellent thermal stability and structural rigidity.

[0049] Although the adsorption kinetics and saturation capacity are slightly inferior to those of Example 2, they are still significantly superior to traditional methods, and their high strength properties are suitable for applications requiring higher material durability. This example demonstrates that, at the upper limit of the parameter range, the method of this invention can directionally prepare functional resins emphasizing ultra-high strength and high stability.

[0050] Comparative Example 1 Based on Example 2, this example examines the fundamental differences in pore structure and functionalization efficiency between the traditional suspension polymerization method (simulating the CN110845660A process) combined with the post-modification path and the HIPE in-situ polymerization method of the present invention. The specific settings are as follows: The performance testing method for the comparative product is completely consistent with that of Example 1. Partial performance characterization was performed, and the characterization results are shown in the table below.

[0051] *Note: The proportion of through holes was estimated by calculating the hysteresis loop area of ​​the mercury intrusion and retraction curves using the mercury intrusion method.

[0052] Analysis of the characterization results shows that D1-1 employs a traditional suspension polymerization and physical post-modification pathway. Its pores are typical non-penetrating mesopores with poor connectivity, resulting in significant mass transfer resistance and extremely slow adsorption kinetics. Although the BET specific surface area is high, the functional groups are mainly loaded through physical adsorption and are easily lost during the adsorption-desorption cycle, leading to low adsorption capacity and poor cycle stability. This comparison demonstrates that the traditional "pore-forming first, modification later" process cannot simultaneously obtain the "penetrating macroporous structure" and "stable covalently bonded functional groups" necessary for this invention.

[0053] Comparative Example 2 Based on Example 2, this example explores whether it is feasible to omit the participation of functional monomers in copolymerization and introduce functional groups only through post-impregnation while maintaining the macroporous framework obtained by the HIPE method. The specific setup is as follows: The performance testing method for the comparative product is completely consistent with that of Example 1. Partial performance characterization was performed, and the characterization results are shown in the table below.

[0054] Analysis of the characterization results shows that although D2-1 possesses a similar through-pore macroporous framework to RB-2, its pore surface zeta potential is close to neutral, indicating that the post-impregnation method almost failed to effectively introduce negatively charged carboxyl groups into the pore walls. This directly results in its adsorption capacity for CV being only 27.8% of that of RB-2. Simultaneously, its polymer network exhibits slightly higher swelling, suggesting that the absence of functional monomers not involved in copolymerization slightly affects the network structure. These results demonstrate that even with an ideal HIPE macroporous template, functional groups must be achieved through "in-situ copolymerization" to achieve high density, covalent bonding, and uniform distribution on the inner surface of the through-pores.

[0055] Furthermore, the adsorption process of D2-1 exhibited a significant hysteresis, further confirming the non-uniformity of functional groups introduced by the post-impregnation method. After multiple cycles, the adsorption capacity of D2-1 rapidly decreased, while RB-2 remained relatively stable. This contrast highlights the significant advantage of in-situ copolymerization in constructing durable functionalized channels. Simultaneously, the low Zeta potential of D2-1 also affects its dispersion stability in the aqueous phase, making it prone to particle aggregation in practical applications, which would have an additional negative impact on adsorption performance. These results fully demonstrate that relying solely on physical impregnation is insufficient to achieve effective loading of functional groups; chemical bonding is essential to ensure the stable existence and efficient function of functional groups.

[0056] Comparative Example 3 Based on Example 2, this example verifies the special role of high-functionality rosin-based crosslinking agents in constructing high-strength, high-thermal-stability networks in HIPE macroporous structures by comparing crosslinking agents of different functionalities and types. The specific setup is as follows: The performance testing method for the comparative product is completely consistent with that of Example 1. Partial performance characterization was performed, and the characterization results are shown in the table below.

[0057] Analysis of the above characterization results shows that, under identical HIPE processes and formulations, changing only the crosslinking agent leads to consistent differences in material properties. Example 2, using a trifunctional rosin-based crosslinking agent (R-FA), exhibits the highest heat distortion temperature and thermal decomposition initiation temperature, as well as the best mechanical strength. D3-1, using a difunctional rosin-based crosslinking agent (R-MA), performs second best, but is still superior to D3-2 using a petroleum-based difunctional crosslinking agent (DVB). This series of comparisons clearly demonstrates that: firstly, rosin-based crosslinking agents, due to their rigid framework, outperform traditional petroleum-based crosslinking agents in terms of thermal stability and mechanical strength; secondly, higher functionality (trifunctionality) significantly increases the crosslinking network density, thereby imparting superior heat resistance and structural strength to the material while maintaining high porosity. This confirms that the selection of a high-functionality rosin-based crosslinking agent is a key material innovation for achieving the synergistic effect of "high porosity, high strength, and high stability" described in this invention, and cannot be easily replaced.

[0058] Comparative Example 4 Based on Example 2, this example verifies the fine-tuning effect of aqueous electrolyte concentration on the stability of HIPE emulsion and the uniformity of the final resin pore structure by adjusting the concentration of the aqueous electrolyte. The specific settings are as follows: The performance testing method for the comparative product is completely consistent with that of Example 1. Partial performance characterization was performed, and the characterization results are shown in the table below.

[0059] Analysis of the characterization results shows that electrolyte concentration is crucial for controlling the stability of HIPE. When the concentration is too low, sufficient ionic strength is not provided to stabilize the emulsion droplets, leading to rapid demulsification and failure to form a regular pore structure. When the concentration is too high, although the emulsion can be stabilized, the excessively high ionic strength results in excessive viscosity of the aqueous phase, exacerbating droplet deformation and coalescence during emulsification, leading to a smaller final pore size and wider distribution. Only within the preferred concentration range as described in the examples can HIPE with excellent stability and uniform droplet size be obtained, thereby replicating the ideal macroporous structure with uniform pore size and high connectivity.

[0060] This further confirms the dual role of aqueous electrolyte concentration in the HIPE system: ensuring emulsion stability while avoiding pore structure degradation due to excessive concentration. The preferred 3% sodium chloride concentration in Example 2 precisely balances these two effects, resulting in a final resin material with both ideal pore size and uniform distribution. In contrast, D4-1, due to insufficient emulsion stability, cannot form a complete porous structure; while D4-2, although maintaining emulsion stability, suffers from excessively high viscosity that restricts droplet movement and rearrangement, hindering pore development. This result highlights the importance of precise control of aqueous electrolyte concentration in the method of this invention and demonstrates that simply adjusting formulation parameters is insufficient to obtain optimal pore structure characteristics.

[0061] Comparative Example 5 Based on Example 2, this example explores the key critical condition for the formation of high internal phase emulsions—the volume fraction of the internal phase (aqueous phase)—and verifies that it must be greater than 74% to form a stable HIPE and obtain an ideal through-pore structure. The specific settings are as follows: the raw material and formulation ratios are completely followed as in Example 2, only the volume ratio of the aqueous phase to the oil phase is changed, thereby changing the volume fraction of the internal phase.

[0062] The performance testing method for the comparative product is completely consistent with that of Example 1. Partial performance characterization was performed, and the characterization results are shown in the table below.

[0063] Analysis of the above characterization results shows that when the internal phase volume fraction is below the critical value of a high internal phase emulsion, aqueous droplets cannot achieve a close packing state in the oil phase, resulting in an unstable emulsion with low porosity and poor connectivity in the formed pore structure. This directly leads to a tortuous adsorption mass transfer path and significantly deteriorates the kinetic performance. This result critically demonstrates from both thermodynamic and geometric perspectives that the formation of a stable high internal phase emulsion (HIPE) with an internal phase volume fraction greater than 74% is an absolute prerequisite for replicating the highly interconnected, mass-transfer-efficient three-dimensional interconnected macroporous structure of this invention.

[0064] The pore characteristics of D5-1 exhibit a typical "ink bottle" effect, characterized by narrow pore openings and large pore cavities. This morphology significantly limits the diffusion efficiency of adsorbate molecules within the pores. Further observation of its mercury intrusion porosimetry (MIP) curve reveals a steep hysteresis loop, indicating significant resistance to droplet exit from the pores—a stark contrast to the well-connected pores. In contrast, Example 2 demonstrates superior pore connectivity, exhibiting a wide and parallel hysteresis loop in its mercury intrusion and exit curves, fully validating the unique advantages of the high internal phase emulsion template method for preparing interconnected macroporous structures.

[0065] Furthermore, adsorption kinetics data show that D5-1 requires over 90 minutes to reach 90% adsorption capacity, significantly longer than the 35 minutes in Example 2. This phenomenon not only reflects the decisive influence of pore connectivity on mass transfer rate but also reveals the necessity of tightly packed aqueous droplets in high internal phase emulsion systems for the formation of the final pore structure. When the internal phase volume fraction is below 74%, even with the same HIPE process and formulation, it is impossible to replicate a interconnected macroporous network with efficient mass transfer characteristics.

[0066] Comparative Example 6 Based on Example 2, this example examines the universality and customizability of the "in-situ copolymerization functionalization" strategy of the present invention by changing the types of functional monomers involved in copolymerization, and verifies that it can conveniently prepare selective adsorption resins for different target pollutants. The specific settings are as follows: the process flow and parameters of Example 2 are completely followed, except that the functional monomer methacrylic acid (MAA, containing carboxyl groups) in the oil phase is replaced with an equimolar amount of other vinyl functional monomers.

[0067] The performance testing method for the comparative product is completely consistent with that of Example 1. Partial performance characterization was performed, and the characterization results are shown in the table below.

[0068] Note: Adsorption selectivity is used to characterize the adsorption preference of a resin for a specific pollutant relative to background ions.

[0069] Analysis of the above characterization results shows that, while maintaining the exact same HIPE macroporous framework and rosin-based crosslinking network, resins with completely different surface chemistry and adsorption selectivity can be prepared simply by changing the functional monomers used in the copolymerization. Sulfonic acid-based resins exhibit Pb... 2+Exhibiting high adsorption capacity, the carboxyl resin is highly efficient for cationic dyes, while the hydroxyl resin shows good adsorption of phenol. Infrared spectroscopy confirms the successful introduction of the corresponding functional groups. This series of comparisons demonstrates the powerful flexibility and customizability of the "in-situ copolymerization functionalization" strategy of this invention. It is not only a method for resin preparation but also a highly efficient "material platform," allowing for precise control of the adsorption performance of the final product through modular replacement of functional monomers to meet diverse separation needs.

[0070] This clearly demonstrates that the selection of functional monomers plays a decisive role in the in-situ copolymerization functionalization strategy. Different functional groups can interact with specific target pollutants, such as the strong coordination between sulfonic acid groups and heavy metal ions, the electrostatic attraction between carboxyl groups and cationic dyes, and the hydrogen bonding between hydroxyl groups and polar organic compounds. This specific recognition mechanism based on intermolecular forces enables the adsorption resin to exhibit significant selective adsorption capacity for target pollutants in complex systems.

[0071] Meanwhile, it is worth noting that the introduction of different functional monomers also has a certain impact on the overall performance of the resin. For example, although the sulfonic acid group of D6-1 provides excellent adsorption performance for heavy metal ions, its adsorption capacity is relatively low, which may be related to its large steric hindrance. While the hydroxyl group of D6-2 can form hydrogen bonds with phenol, the relatively weak hydrogen bonding results in only a moderate level of adsorption selectivity. These phenomena indicate that in practical applications, it is necessary to comprehensively consider the type, density, and interaction mechanism between the functional monomers and the pollutants, based on the characteristics of the target pollutant, in order to obtain the best adsorption effect.

[0072] Furthermore, this series of comparisons reveals the unique advantages of in-situ copolymerization functionalization strategies in material design. Compared to traditional post-modification methods, this strategy can directly and uniformly introduce functional monomers into the resin backbone during polymerization, ensuring the uniform distribution of functional groups throughout the material. This not only improves the utilization rate of functional groups but also enhances their stability during use, thereby extending the material's service life. Therefore, the in-situ copolymerization functionalization strategy provided by this invention offers a promising technological platform for developing high-performance, customizable adsorbent materials.

[0073] Comparative Example 7 Based on Example 2, this example explores the impact on the final resin structure and properties when the key staged temperature-controlled polymerization process of this invention is replaced with conventional isothermal polymerization, under the premise of completely identical raw material formulation and emulsification process, thereby verifying the necessity and superiority of the staged temperature control strategy. The specific settings are as follows: The performance testing method for the comparative product was completely consistent with that of Example 1. Key performance characteristics were characterized, and the results are shown in the table below.

[0074] Analysis of the above characterization results shows that, under the same raw material formulation and emulsification process conditions, the staged temperature-controlled polymerization process has a significant impact on the structure and properties of the resin. Compared with Example 2, after D7-1 was polymerized at an isothermal temperature, the pore size of the resin increased to 18.5 μm, but the porosity decreased to 80.1%, indicating that the regularity and connectivity of the pore structure were damaged to some extent. Simultaneously, its saturated adsorption capacity for crystal violet decreased to 310.5 mg / g, a reduction of approximately 18.4% compared to Example 2, which may be related to uneven pore distribution and decreased utilization of surface functional groups. Furthermore, the thermal stability of D7-1 also decreased, with a 5% thermogravimetric temperature of 291.5 °C, lower than the 306.0 °C of Example 2. This may be due to insufficient crosslinking network formation during the isothermal polymerization process. The radial compressive strength also decreased from 6.3 MPa to 4.7 MPa, further verifying the superiority of the staged temperature-controlled strategy in improving the mechanical properties of the material.

[0075] The coefficient of variation for pore size distribution in D7-1 was as high as 28.2%, significantly higher than <15% in Example 2. This indicates that isothermal polymerization struggles to effectively control the uniformity of emulsion droplet size, resulting in a highly dispersed final pore structure. Furthermore, FT-IR estimation of the residual double bond content showed that the proportion of unreacted double bonds in D7-1 reached 8.1%, significantly higher than <2% in Example 2. This result suggests that reactive centers under isothermal polymerization conditions may not be fully converted, potentially leading to aging or performance degradation during long-term use.

[0076] Analyzing the comparative results in this example, the staged temperature-controlled polymerization process, by precisely regulating the reaction kinetics at different stages, effectively optimizes the formation of the cross-linked network, thereby endowing the resin with superior pore structure characteristics, thermal stability, and mechanical strength. In contrast, while isothermal polymerization simplifies the operation process, it is difficult to achieve precise control over the reaction process, resulting in the final material performing poorly in several key performance indicators. This comparison clearly demonstrates that the staged temperature control strategy is an indispensable core step in the method of this invention, playing an irreplaceable role in achieving the synergistic effect of "high porosity, high strength, and high stability."

Claims

1. A method for preparing an adsorption resin, characterized in that, The method includes: 1) A rosin-based multi-double bond crosslinking agent, a vinyl functional monomer, and an oil-soluble initiator are dissolved in a hydrophobic organic solvent to form a homogeneous oil phase; 2) Dissolve the water-soluble electrolyte in deionized water to form an aqueous phase solution; 3) Under stirring conditions, the aqueous phase obtained in step 2) is continuously added to the oil phase obtained in step 1), and a stable water-in-oil emulsion with high internal phase is formed through high-speed emulsification; 4) The emulsion obtained in step 3) is subjected to a thermally initiated polymerization reaction. After the reaction is completed, it is extracted with solvent and dried to obtain the adsorption resin.

2. The method for preparing an adsorption resin according to claim 1, characterized in that, Step 1) The rosin-based multi-double-bond crosslinking agent is a rosin derivative containing two or three polymerizable double bonds; Step 1) The vinyl functional monomer is a vinyl monomer containing carboxyl groups and / or sulfonic acid groups and / or hydroxyl groups; Step 1) The oil-soluble initiator is benzoyl peroxide or azobisisobutyronitrile; Step 1) The hydrophobic organic solvent is toluene and / or xylene and / or n-heptane and / or cyclohexane; The mass percentages of each component in step 1) are as follows: 30-50% rosin-based double bond crosslinking agent, 8-18% vinyl functional monomer, 0.5-2.5% oil-soluble initiator, and the balance being a hydrophobic organic solvent.

3. The method for preparing an adsorption resin according to claim 2, characterized in that, The rosin-based multi-double bond crosslinking agent is fumarate-piperidine glycol trimethacrylate; The vinyl functional monomer is methacrylic acid and / or acrylic acid and / or 2-acrylamide-2-methylpropanesulfonic acid and / or hydroxyethyl methacrylate.

4. The method for preparing an adsorption resin according to claim 1, characterized in that, Step 2) The water-soluble electrolyte is sodium chloride; Step 2) The mass concentration of the water-soluble electrolyte in deionized water is 2.0-3.0%.

5. A method for preparing an adsorption resin according to claim 1 or 4, characterized in that, Step 2) The aqueous phase is added with an oil-soluble emulsifier, sorbitan monooleate, at a concentration of 0-0.5% of the total mass of the aqueous phase.

6. The method for preparing an adsorption resin according to claim 1, characterized in that, Step 3) The volume ratio of the aqueous phase to the oil phase is (3-5):1; Step 3) The high-speed emulsification is carried out at a stirring speed of 2000-4000 rpm and an ambient temperature of 20-30 ℃ for 20-50 min.

7. The method for preparing an adsorption resin according to claim 1, characterized in that, Step 4) The thermally initiated polymerization reaction is carried out under a nitrogen atmosphere. First, the reaction is carried out at 60-65 °C for 4-8 h, and then the temperature is lowered to 55-58 °C to continue the reaction for 16-30 h, with a total reaction time of 24-36 h.

8. A method for preparing an adsorbent resin according to claim 1 or 7, characterized in that, Step 4) The solvent extraction involves sequentially extracting the polymerization product with ethanol or methanol and deionized water using a Soxhlet extraction method for 24–48 hours. Step 4) involves drying the product in a vacuum oven at a temperature of 60–80 °C until it reaches a constant weight.

9. An adsorption resin prepared by any one of claims 1 to 8.

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