Polymer for water treatment and its use in scale inhibition

Abstract

The application belongs to the technical field of water treatment, and particularly relates to a polymer for water treatment and application of the polymer in scale inhibition. The polymer for water treatment is obtained by free radical copolymerization of mixed monomers, wherein the mixed monomers comprise monomer a, monomer b and monomer c, the monomer a is 2-(3-allylureido)benzohydroxamic acid monomer, the monomer b is at least one of mesaconic acid, aconitic acid or citraconic acid; and the monomer c is at least one of 3-allyloxy-2-hydroxy-1-propanesulfonic acid, 2-methyl-2-propen-1-sulfonic acid sodium or p-vinylbenzenesulfonic acid. The polymer can maintain good scale inhibition effect under static scale inhibition, dynamic flow anti-scouring, reverse osmosis membrane dynamic scale inhibition and high-temperature high-salt long-period operation conditions, and can especially slow down scale inhibition performance attenuation caused by shear scouring under dynamic working conditions.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a polymer for water treatment and its application in scale inhibition. Background Technology

[0002] With the development of water treatment scenarios such as industrial circulating water, reverse osmosis membrane systems, high-salinity wastewater treatment, and oilfield water injection, the calcium content in water bodies is increasing. 2+ Mg 2+ CO3 2- SO4 2- PO4 3- Plasma readily deposits on heat exchange surfaces, pipe inner walls, membrane surfaces, or equipment interfaces, forming inorganic scale such as CaCO3, CaSO4, and Ca3(PO4)2. Scale formation reduces heat exchange efficiency and membrane flux, increases operating energy consumption, and may cause equipment blockage, corrosion, and increased cleaning frequency. Therefore, developing efficient and stable scale inhibitors suitable for complex operating conditions is of great significance. Existing scale inhibitors mainly include organophosphonates, polycarboxylic acid polymers, sulfonic acid copolymers, and polyaspartic acid modified products. These scale inhibitors typically rely on functional groups such as carboxyl, sulfonic acid, phosphonic acid, hydroxyl, or amide groups to complex calcium and magnesium ions, or adsorb onto the scale crystal surface to interfere with crystal nucleation and growth, thereby achieving scale inhibition. While these systems exhibit certain effects under static conditions, their structural designs often focus on aqueous phase complexation, dispersion, and crystal distortion, neglecting the interfacial adhesion stability under dynamic flow, membrane crossflow, and high-temperature, high-salt conditions.

[0003] Chinese patent CN108503819A discloses a phosphine-containing hyperbranched scale inhibitor polymer, which mainly enhances complexation and dispersion through conventional functional groups such as phosphonic acid groups; WO2023245197A2 discloses the use of labeled polymers as phosphate substitutes in water treatment, focusing on formulation monitoring and phosphate substitution applications. Neither of these technologies constructs a spatially pre-organized, dual-anchored interfacial unit at the molecular structure level of polymerizable functional monomers, nor do they adequately address the problem of insufficient stability of the scale inhibitor interfacial adsorption layer under dynamic high shear, membrane crossflow, and high-temperature, high-salt, long-term operation conditions.

[0004] In practical industrial systems, scale inhibitors not only need to maintain their complexing, dispersing, and salt-resistant capabilities in the aqueous phase, but also need to form a relatively stable interfacial layer on scale crystals, metal, or membrane surfaces to resist performance degradation caused by high-flow-rate erosion and long-term operation. Hydroxyxamic acid groups possess coordination sites such as carbonyl oxygen and N-hydroxy oxygen, which can form coordination or strong polar interactions with metal ions or active sites on the scale crystal surface; urea groups contain multiple NH and carbonyl oxygen groups, which can form multiple hydrogen bonds with carbonate, sulfate, surface oxygen atoms, or the interfacial hydration layer. However, existing scale inhibitor polymers lack structural designs that fix the hydroxyxamic acid and urea groups in the same rigid aromatic backbone at adjacent positions and introduce them into the polymer chain as synergistic interfacial anchoring units.

[0005] Therefore, although existing technologies disclose various scale inhibitor polymers containing carboxyl, sulfonic acid, phosphonic acid, or amide groups, they still lack molecular-level interfacial anchoring designs for dynamic high-shear, membrane cross-flow, and high-temperature, high-salt, long-term operating conditions. It is necessary to develop a polymerizable functional monomer with a specific spatial configuration that can improve the polymer's interfacial adhesion stability on scale, metal, or membrane surfaces while maintaining its aqueous complexing, dispersion, and salt resistance properties, thereby improving its long-term scale inhibition performance under complex operating conditions. Summary of the Invention

[0006] The purpose of this invention is to provide a polymer for water treatment to solve the problem that although existing scale inhibitors can inhibit the deposition of inorganic salt scale such as CaCO3 and CaSO4 under static conditions through complexation, dispersion or lattice distortion, their interfacial adhesion stability is insufficient and their scale inhibition effect is easily reduced under high shear dynamic flow, reverse osmosis membrane crossflow and high temperature and high salt long-term operation conditions; this invention also provides the application of the polymer for water treatment in scale inhibition.

[0007] The water treatment polymer of the present invention is obtained by free radical copolymerization of mixed monomers, wherein the mixed monomers include monomer a, monomer b, and monomer c. Monomer a is a 2-(3-allylureo)benzylhydroxamic acid monomer, and the structural formula of monomer a is as follows: ; Monomer b is at least one of citralic acid, aconitic acid, or citric acid; Monomer c is at least one of 3-allyloxy-2-hydroxy-1-propanesulfonic acid, sodium 2-methyl-2-propene-1-sulfonate, or p-vinylbenzenesulfonic acid.

[0008] The mixed monomers also include monomer d, which is at least one of allylphosphonic acid, vinylphosphonic acid, dimethyl vinylphosphonate, isopropenylphosphonic acid, or (2-acryloylaminoethyl)phosphonic acid, and the molar ratio of monomer a to monomer d is 1:0.2-0.5.

[0009] The content of monomer a in the mixed monomers is 5-20 mol%, preferably 5-15 mol%, more preferably 8-12 mol%; the molar ratio of monomer b to monomer a is 2-12:1, and the molar ratio of monomer c to monomer a is 1-7:1.

[0010] The weight-average molecular weight of the polymer for water treatment is 20,000-100,000 Da, preferably 30,000-70,000 Da, and more preferably 40,000-60,000 Da.

[0011] The free radical copolymerization reaction is a free radical polymerization reaction carried out in water or a mixture of water and a water-miscible organic solvent using an initiator. The water-miscible organic solvent is one or more of methanol, ethanol, isopropanol, acetone, tetrahydrofuran, N,N-dimethylformamide, or dimethyl sulfoxide. The polymerization temperature is 40-80℃, the polymerization time is 4-8 hours, and the initiator is at least one of ammonium persulfate, potassium persulfate, hydrogen peroxide, a persulfate / bisulfite redox initiation system, or a hydrogen peroxide / ascorbic acid redox initiation system, preferably ammonium persulfate or potassium persulfate.

[0012] The method for preparing 2-(3-allylureo)benzylhydroxamic acid monomer includes the following steps: (1) Methyl 2-aminobenzoate was dissolved or dispersed in an anhydrous organic solvent. Under nitrogen protection and stirring, allyl isocyanate was added dropwise. After the addition was complete, the reaction was stirred. After the reaction was completed, the solution was concentrated under reduced pressure to obtain a concentrated solution. The concentrated solution was treated to obtain a crude product. The crude product was purified and dried to obtain methyl 2-(3-allylureo)benzoate intermediate. (2) Add the methyl 2-(3-allylureo)benzoate intermediate obtained in step (1) to the first solvent and stir to dissolve or disperse to obtain an intermediate solution or intermediate dispersion; add hydroxylamine hydrochloride to the second solvent and stir to dissolve, cool down, add alkaline reagent to adjust pH to obtain hydroxylamine reaction solution; (3) Add the hydroxylamine reaction solution to the intermediate solution or intermediate dispersion, stir the reaction, cool the resulting reaction solution to room temperature, filter, adjust the pH of the filtrate, let it stand, filter, wash the resulting filter cake, and vacuum dry to obtain 2-(3-allylureo)benzylhydroxyoxime monomer.

[0013] In step (1), the molar ratio of methyl 2-aminobenzoate and allyl isocyanate is 1:1.1-1.2, and the anhydrous organic solvent is one or more of tetrahydrofuran, acetonitrile, dichloromethane, N,N-dimethylformamide or dimethyl sulfoxide, preferably one or more of tetrahydrofuran, acetonitrile or N,N-dimethylformamide; the dropping temperature is 0-10℃, the stirring reaction temperature is 25-35℃, and the stirring reaction time is 4-8 hours; the concentrated solution treatment step is to pour the concentrated solution into deionized water to precipitate the solid, filter and collect the precipitated solid to obtain the crude product, or to extract the concentrated solution with ethyl acetate, collect the organic phase and wash it successively with deionized water and saturated sodium chloride solution, and obtain the crude product after drying, filtration and vacuum concentration; the purification is one or both of recrystallization or washing.

[0014] In step (2), the first solvent is one or more of methanol, water, ethanol or N,N-dimethylformamide, the second solvent is one or more of methanol, water or ethanol, the temperature is lowered to 0-10℃, the molar ratio of methyl 2-(3-allylureo)benzoate intermediate to hydroxylamine hydrochloride is 1:2.0-4.0, the alkaline reagent is one or more of sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, potassium carbonate solution, sodium methoxide or sodium ethoxide, and the pH is adjusted to 8.3-8.5.

[0015] In step (3), the temperature is 0-10℃, the stirring temperature is 25-40℃, the pH of the stirring reaction is 8.0-8.5, the stirring reaction time is 2-8 hours, the pH is adjusted to 3.5-4.5, the standing temperature is 0-10℃, the standing time is 1-6 hours, the vacuum drying temperature is 35-50℃, and the vacuum drying time is 8-16 hours.

[0016] The preparation method of 2-(3-allylureo)benzylhydroxamic acid monomer includes the following specific steps: (1) Methyl 2-aminobenzoate is dissolved or dispersed in an anhydrous organic solvent. To avoid the side polymerization of the allyl structure during the reaction and post-treatment, a small amount of polymerization inhibitor can be added. The polymerization inhibitor is selected from one or more of p-methoxyphenol, hydroquinone, or 2,6-di-tert-butyl-p-cresol. Under nitrogen protection and stirring conditions, allyl isocyanate is added dropwise. After the addition is complete, the reaction is stirred to allow the amino group in methyl 2-aminobenzoate to undergo an addition reaction with allyl isocyanate to generate methyl 2-(3-allylureo)benzoate intermediate containing an allylureoyl structure. After the reaction is completed, the solvent is removed by vacuum concentration to obtain a concentrated solution. The concentrated solution is treated to obtain a crude product. The crude product is purified and dried to obtain methyl 2-(3-allylureo)benzoate intermediate. The purification is carried out by recrystallization or washing purification using one or more of ethanol, water, ethyl acetate, or petroleum ether. (2) Add the methyl 2-(3-allylureo)benzoate intermediate obtained in step (1) to the first solvent and stir to dissolve or disperse to obtain an intermediate solution or intermediate dispersion; add hydroxylamine hydrochloride to the second solvent and stir to dissolve, cool down, add alkaline reagent to adjust pH to release free hydroxylamine, and obtain hydroxylamine reaction solution; (3) Add the hydroxylamine reaction solution to the intermediate solution or intermediate dispersion and stir to react. During the reaction, hydroxylamine undergoes a nucleophilic acyl substitution reaction on the carbonyl group in the methyl benzoate structure, converting the methyl ester group into a hydroxamic acid group, while the ortho-allyl urea group structure remains unchanged, generating 2-(3-allylurel)benzyl hydroxamic acid. After the reaction is completed, cool the obtained reaction solution to room temperature, filter to remove insoluble matter, adjust the pH of the obtained filtrate with dilute hydrochloric acid to precipitate the solid product, let it stand, collect the precipitated solid through filtration, wash the obtained filter cake 2-3 times with cold deionized water, and then wash 1-2 times with cold ethanol or ethanol-water mixed solvent to remove residual salt, hydroxylamine and small molecule impurities. The filter cake can also be further purified by recrystallization or recrystallization using ethanol-water, methanol-water or N,N-dimethylformamide-water mixed solvent. Vacuum dry to obtain 2-(3-allylurel)benzyl hydroxamic acid monomer.

[0017] The synthetic reaction equation for the monomer of 2-(3-allylureo)benzylhydroxamic acid is as follows: .

[0018] The application of the water treatment polymer described in this invention in scale inhibition involves using the water treatment polymer as an active ingredient to prepare a scale inhibitor, which is used to inhibit the deposition of inorganic salt scale in industrial circulating cooling water systems, reverse osmosis membrane systems, high-salt wastewater treatment systems, boiler feedwater systems, or oilfield water injection systems.

[0019] The inorganic scale includes CaCO3, CaSO4, Ca3(PO4)2, iron scale, or a mixture thereof.

[0020] When in use, the dosage of the polymer for water treatment is 2.5-10 mg / L, preferably 5-10 mg / L.

[0021] The specific technical advantages of this invention are detailed below: I. The electronic structure of bifunctional groups and the irreplaceability of ortho-position fixation Monomer a is a 2-(3-allylureo)benzylhydroxamic acid monomer, whose molecular structure simultaneously contains a hydroxamic acid group, a urea group, and an allyl group that can be polymerized by free radicals. The hydroxamic acid group and the urea group are located in the ortho position on the same aromatic ring, forming an ortho-hydroxamic acid-urea group double-anchored structural unit with spatial pre-organization characteristics.

[0022] Hydroxamic acid group (-C(=O)NHOH) and urea group (-NH-C(=O)-NH-) have natural complementarity in electronic structure, but this complementarity can only be effectively exerted under extremely close spatial distance and specific relative orientation.

[0023] From an electronic perspective: the hydroxamic acid group contains two coordinating atoms, a carbonyl oxygen and an N-hydroxy oxygen, which can react with Ca... 2+ Metal ions form stable five-membered ring chelate structures. This bidentate coordination is stronger than monodentate coordination (such as carboxylate coordination) and has a specific directionality requirement. The urea group contains two NH bonds and one carbonyl oxygen, which can act as a donor and acceptor for multiple hydrogen bonds. However, when the urea group is used alone, the hydrogen bonds of the urea group are easily weakened by ionic strength and thermal motion under high temperature or high salt environment; when the hydroxamic acid group is used alone, intermolecular self-aggregation or insoluble complexes with calcium ions are likely to occur, which will reduce the scale inhibition efficiency.

[0024] By fixing the hydroxamic acid group and the urea group to the adjacent position on the same benzene ring, the rigid framework of the benzene ring forces the two groups into an almost coplanar conformation, with their active regions pointing to the same side of the benzene ring plane. Their spatial distance is precisely within a range that allows them to cooperate without interfering with each other. This geometric arrangement brings about two key electronic effects: First, coordination-induced hydrogen bonding is enhanced. When the oxygen atom of the hydroxamic acid group coordinates with a calcium ion, the positive charge of the calcium ion is transferred to the adjacent urea group through the π-conjugation system of the benzene ring, increasing the polarity of the NH bond of the urea group and significantly enhancing its hydrogen bond donor capacity. This "electron transcyclic transfer" effect is greatly weakened in meta or para structures (because the transfer path becomes longer or blocked), but it is completely absent in random copolymerization of different monomers.

[0025] Second, effective avoidance of intramolecular competition. It is generally believed in the art that when two strongly polar groups are in adjacent positions, they easily form intramolecular hydrogen bonds (e.g., the OH group of hydroxamic acid and the C=O group of urea), thus locking up activity. This invention, through experiments, has found that under the rigid constraint of the benzene ring, the active centers of the two groups tend to extend outward to interact with solvents or ions, rather than pairing inward. This is because the formation of intramolecular hydrogen bonds requires specific bond angles and distances, and the adjacent positions of the benzene ring precisely cause the active centers of the two groups to point outward, forming an "outward pre-organized" conformation. This result, contrary to conventional understanding, was unexpectedly discovered through experimental screening.

[0026] II. Spatial Matching of Adjacent Structures and Scale Surface Interaction Scale crystals (such as CaCO3 and CaSO4) exhibit a periodic ionic arrangement on their surface. Although the specific spacing between different crystal planes varies, generally, the distance between surface calcium ions and adjacent anions (carbonate or sulfate) falls within a characteristic range (typically on the order of 2.5–4.5 Å). In this invention, the ortho-hydroxyxamic acid-urea unit, when the hydroxyxamic acid coordinates with a surface calcium ion, allows the ortho-urea group to form a hydrogen bond with the adjacent anion or surface oxygen atom, thus achieving the effect of simultaneously anchoring a structural unit to two adjacent sites on the scale crystal surface.

[0027] The key to this "intramolecular dual-site anchoring" lies in the fact that the distance between the two functional groups must roughly match the spacing between adjacent active sites on the scale surface. If the distance is too small (e.g., hydroxamic acid and urea groups are attached to the same carbon atom), the urea group will deviate from the appropriate hydrogen bond position after coordination; if the distance is too large (e.g., meta, para, or belonging to different monomers), the urea group cannot form effective hydrogen bonds with sites near the hydroxamic acid anchoring region and can only interact with more distant sites, significantly reducing synergy. This invention chooses the ortho position of the benzene ring based on a reasonable judgment and experimental verification of the spatial distribution of active sites on the scale surface. This spatial matching relationship is crucial in determining the synergistic effect and cannot be naturally obtained by any "combination".

[0028] III. Entropy Advantages of Pre-organized Conformations The adsorption stability of scale-inhibiting polymers at the interface depends not only on the adsorption enthalpy (the strength of the interaction) but is also significantly affected by the adsorption entropy. When the polymer chain transitions from a freely coiled state in solution to an adsorbed state at the interface, the degree of conformational freedom decreases, resulting in entropy loss. If the polymer requires significant conformational adjustments to allow both functional groups to act simultaneously at the interface, the entropy loss will be even greater, and the adsorption driving force will be correspondingly weakened.

[0029] In this invention, the hydroxamic acid and urea groups are fixed in an ortho-ortho relationship by a rigid aromatic skeleton at the monomer stage, forming a "pre-organized" bifunctional unit. When the polymer approaches the scale surface, this unit does not require additional conformational folding or rotation to allow both groups to simultaneously face the interface and find matching action sites. Therefore, the entropy loss during adsorption is much smaller than in the following two contrasting scenarios: first, when the hydroxamic acid and urea groups are located at different positions on the polymer chain, requiring chain segment movement to bring them closer; second, when they are located at the meta or para positions on the same aromatic ring, requiring overall molecular orientation adjustment to simultaneously contact the interface.

[0030] This entropy advantage is particularly important under dynamic flow conditions: when water flow attempts to pull the polymer away from the interface, the pre-organized units can quickly re-adsorb because they can re-anchor without having to find a suitable conformation after desorption. This is equivalent to reducing the energy barrier asymmetry of adsorption / desorption and prolonging the interfacial residence time.

[0031] IV. The Indivisible Nature of Multi-Unit Synergistic Scale Inhibition The polymer of this invention is composed of monomer a (ortho-anchored dual unit), monomer b (carboxylic acid unit), and monomer c (sulfonic acid unit), and optionally monomer d (phosphonic acid unit). Each unit plays a different role in the scale inhibition process, but they are interdependent: The carboxyl group provided by monomer b rapidly complexes with free Ca in the aqueous phase. 2+ and Mg 2+ This reduces the nucleation rate; The sulfonic acid groups provided by monomer C endow the polymer with strong negative charge and high solubility, which can stably disperse microcrystals under high salt and high hardness conditions and prevent aggregation and deposition. The phosphonic acid groups provided by monomer d further enhance the affinity for calcium ions and scale surfaces, and extend the ability to inhibit calcium phosphate scale.

[0032] The adjacent dual anchoring unit provided by monomer a is responsible for forming a durable adsorption layer on the surface of scale, metal or membrane, resisting desorption by water flow.

[0033] The absence of any one of these units will expose performance shortcomings under specific operating conditions: without monomer a, the scale inhibition rate will decrease significantly under dynamic scouring; if monomer a is replaced with a monomer containing only urea groups and no hydroxamic acid, the scouring resistance under high temperature and high salt conditions will be significantly insufficient; if the ratio of monomer b or monomer c is unbalanced, the complexing or dispersing ability of the aqueous phase will decrease.

[0034] V. Unpredictability of Overall Performance Based on the aforementioned synergistic mechanism at the molecular level, the polymer of this invention exhibits excellent comprehensive performance under various operating conditions, including static scale inhibition, dynamic flow erosion resistance, dynamic scale inhibition in reverse osmosis membranes, and long-term operation under high temperature and high salt conditions.

[0035] Compared with existing technologies, the most significant improvement of this invention lies in the following: under dynamic high-shear conditions (flow rate 1.0-4.0 m / s), the scale inhibition rate does not decrease significantly with increasing flow rate, demonstrating excellent anti-erosion stability; under high-temperature and high-salt conditions (85℃, 3.5% NaCl), it maintains high scale inhibition activity even after 72 hours of continuous operation. These technical effects directly stem from the electronic synergy and spatial matching of the ortho-hydroxyoxime acid-urea group, rather than the simple addition of any monomer or functional group.

[0036] The beneficial effects of this invention are as follows: This invention introduces a 2-(3-allylureo)benzyl hydroxamic acid monomer, resulting in a polymer chain containing ortho-hydroxyxamic acid-urea structural units. The core of this structure lies in the following: the hydroxamic acid group, with its carbonyl oxygen and N-hydroxy oxygen as bidentate coordinating atoms, forms a stable chelating effect with calcium ions or metal sites on scale surfaces; the urea group, with its two NH groups and one carbonyl oxygen as multiple hydrogen bond donors and acceptors, forms a hydrogen bond network with carbonate, sulfate, or interfacial oxygen atoms. With both fixed in the ortho position on the same aromatic ring, the rigid framework of the benzene ring forces the active regions of both functional groups to point to the same side of the ring plane, with a spatial distance precisely within a range that allows for mutual coordination without intramolecular competition. This configuration achieves two key effects: Firstly, there is the intercyclic electron coordination. When hydroxamic acid coordinates with a metal ion, the positive charge of the metal ion is transferred to the adjacent urea group through the π-conjugated system of the benzene ring, enhancing the polarity of the NH bond of the urea group and improving its hydrogen bond donor capacity. Conversely, after the urea group forms a hydrogen bond, it can also stabilize the hydroxamic acid-metal coordination bond through an inductive effect. This positive coordination is significantly weakened in meta- or para-position structures due to the elongated transfer path, and is completely absent in random copolymerization of different monomers.

[0037] Secondly, spatial matching and entropy advantage. The distance between calcium ions and adjacent anions on the scale surface (such as CaCO3, CaSO4) falls within a certain characteristic range. The span of the adjacent bifunctional groups in this invention roughly corresponds to this range, allowing a structural unit to simultaneously anchor to two adjacent active sites on the scale surface (hydroxyxamic acid coordinating with calcium ions, and urea group hydrogen bonding with adjacent anions). Since this unit is "pre-organized" into an active conformation by a rigid framework before adsorption, the conformational entropy loss during adsorption is much smaller than that of structures that require folding or rotation to work synergistically (such as meta / para sites, or random copolymers). This entropy advantage is particularly crucial under dynamic high-shear conditions, facilitating faster re-anchoring of the polymer after desorption, thereby extending the interfacial residence time.

[0038] Compared to conventional scale inhibitors that rely solely on carboxyl, sulfonic acid, phosphonic acid, or common amide groups, the polymer of this invention, while maintaining aqueous complexation, dispersion, and salt resistance, further enhances interfacial adhesion stability on scale crystals, metal, or membrane surfaces. This enhancement does not stem from the simple superposition of the effects of various functional groups, but rather from the combined effects of electronic synergy, spatial matching, and pre-organized entropy advantage induced by ortho-position fixation. Experimental results show that the polymer of this invention maintains good scale inhibition performance under static scale inhibition, dynamic flow erosion resistance, reverse osmosis membrane dynamic scale inhibition, and high-temperature, high-salt, long-term operation conditions, especially mitigating the scale inhibition performance degradation caused by shear erosion under dynamic operating conditions. In contrast, if hydroxamic acid and urea groups are placed at the meta or para positions, or randomly copolymerized with different monomers, the aforementioned synergistic effect is significantly weakened or even disappears.

[0039] Therefore, the technical effect of this invention stems from the synergistic effect of the ortho-hydroxyoxime acid-urea group structure with the carboxyl, sulfonic acid, and optionally phosphonic acid groups. Specifically, the ortho-hydroxyoxime acid-urea group structure provides multi-point interfacial interaction and erosion resistance, while the carboxyl, sulfonic acid, and optionally phosphonic acid groups provide aqueous phase complexation, dispersion, and salt resistance support. This structural design enables the polymer to adapt to complex water treatment environments such as high shear, high salinity, high temperature, and long-term operation. Furthermore, the aforementioned comprehensive performance cannot be reasonably predicted from the simple summation of the existing functions of the individual monomers, thus possessing substantial technological advancement and industrial application value. Attached Figure Description

[0040] Figure 1 This is the infrared spectrum of methyl 2-(3-allylureo)benzoate from Example 1.

[0041] Figure 2 This is the 1H NMR spectrum of methyl 2-(3-allylureo)benzoate from Example 1.

[0042] Figure 3 This is the infrared spectrum of the 2-(3-allylureo)benzohydroxyoxime monomer in Example 1.

[0043] Figure 4 This is the 1H NMR spectrum of the 2-(3-allylureo)benzylhydroxamic acid monomer in Example 1.

[0044] Figure 5 This is the infrared spectrum of the polymer in Example 1. Detailed Implementation

[0045] The present invention will be further described below with reference to embodiments.

[0046] Example 1 I. Preparation of 2-(3-allylureo)benzylhydroxamic acid monomer (1) Add 0.10 mol of methyl 2-aminobenzoate and 150 mL of anhydrous tetrahydrofuran to a dry three-necked flask. After stirring and dissolving, cool the reaction system to 3°C under nitrogen protection and stirring. Then, slowly add 0.115 mol of allyl isocyanate dropwise over 30 minutes, controlling the temperature of the reaction system at 5°C during the dropwise addition. After the dropwise addition is complete, raise the temperature of the reaction system to 25°C and continue stirring for 8 hours. After the reaction is complete, concentrate the solution to about 50 mL under reduced pressure at 40°C to obtain a concentrated solution. Slowly pour the concentrated solution into 500 mL of deionized water to precipitate the solid product. Collect the precipitated solid by filtration and wash it three times with deionized water. Dry the obtained solid under vacuum at 45°C for 10 hours to obtain 19.1 g of solid methyl 2-(3-allylureo)benzoate intermediate with a yield of 81.6% and a melting point of 152-153°C. The structure of the obtained methyl 2-(3-allylureo)benzoate intermediate was determined by infrared spectroscopy (IR) and nuclear magnetic resonance (NMR) spectroscopy (NMR). 1 Characterization and confirmation were performed using 1H NMR and EI-MS, and the results are shown in [Figure number missing]. Figure 1 and Figure 2 .

[0047] Infrared spectroscopy display ( Figure 1 The intermediate was at 3298 cm. -1 The presence of a broad absorption peak nearby can be attributed to the N–H stretching vibration of the urea group, indicating that a urea group structure has been introduced into the molecule, and there may be some hydrogen bonding interaction; 2983 cm⁻¹ -1 2917cm -1 and 2848cm -1 The nearby absorption peaks can be attributed to aliphatic C–H stretching vibrations in the methoxy and allyl methylene groups. In the carbonyl absorption region, at 1696 cm⁻¹… -1 The strong absorption peak at 1610 cm⁻¹ can be attributed to the C=O stretching vibration of the ester group in the methyl benzoate structure. -1 The nearby absorption peaks can be attributed to the C=O stretching vibration of the urea group and may overlap with the vibrations of the aromatic ring skeleton. (1523 cm⁻¹) -1 The nearby absorption peak can be attributed to the coupled absorption of the urea group's N–H bending vibration and C–N stretching vibration; 1369 cm⁻¹ -1 The nearby absorption peak can be attributed to a complex absorption of aromatic ring skeletal vibrations, C–H bending vibrations, and C–N stretching vibrations. (1165 cm⁻¹) -1 1110cm -1 and 1060cm -1 The nearby absorption peaks can be attributed to the C–O and C–O–C stretching vibrations of the ester group and the C–N stretching vibration of the urea group. (944 cm⁻¹) -1 The nearby absorption peak can be attributed to the out-of-plane bending vibration of the allyl double bond =CH2; 735 cm⁻¹ -1646cm -1 and 560cm -1 The nearby absorption peaks can be attributed to the out-of-plane bending vibrations of the substituted benzene rings and the related out-of-plane vibrations of the aromatic rings. The aforementioned characteristic absorption peaks indicate that the intermediate simultaneously contains methyl benzoate, urea, aromatic ring, and allyl structures, confirming the formation of the methyl 2-(3-allylureo)benzoate intermediate.

[0048] 1H NMR (1H NMR) Figure 2 () 1 H NMR, 400 MHz, DMSO-d6) δ: 9.68 (br s, 1H, Ar-NH-CO), 7.92 (dd, J = 7.8, 1.5 Hz, 1H, Ar-H), 7.55 (td, J = 7.8, 1.5 Hz, 1H, Ar-H), 7.26 (dd, J = 8.2, 1.2 Hz, 1H, Ar-H), 7.04 (td, J = 7.5, 1.2 Hz, 1H, Ar-H), 6.47 (brs, 1H, -CO-NH-CH2-), 5.88 (m, 1H, -CH=CH2), 5.23 (dd, J = 17.2, 1.6 Hz, 1H, =CH2trans), 5.12 (dd, J = 10.3, 1.5 Hz, 1H, =CH2 cis), 3.86 (m, 2H, -NH-CH2-CH=CH2), 3.81 (s, 3H, -COOCH3).

[0049] Mass spectrometry (EI-MS) shows the molecular ion peak [M]. + With an m / z of 234.10, the theoretical molecular formula of the intermediate methyl 2-(3-allylureo)benzoate is C2. 12 H 14 Consistent with N2O3.

[0050] (2) Add the methyl 2-(3-allylureo)benzoate intermediate obtained in step (1) to a methanol / water mixed solvent (120 mL methanol and 40 mL deionized water), stir to disperse it fully, and obtain an intermediate dispersion; separately add 0.30 mol hydroxylamine hydrochloride to a methanol / water mixed solvent (40 mL methanol and 40 mL deionized water), stir to dissolve, cool the system to 5°C, and then slowly add 30 wt.% sodium hydroxide solution to adjust the pH of the system to 8.5, and obtain hydroxylamine reaction solution.

[0051] (3) Under stirring conditions, the hydroxylamine reaction solution obtained in step (2) was added dropwise to the intermediate dispersion obtained in step (2) within 30 minutes. During the dropwise addition, the temperature of the reaction system was controlled at 10°C. After the dropwise addition was completed, the temperature of the reaction system was raised to 30°C, and the pH of the system was maintained at 8.5 with 30wt.% sodium hydroxide solution. The reaction was continued to be stirred for 6 hours. After the reaction was completed, the resulting reaction solution was cooled to 25°C, filtered to remove a small amount of insoluble matter, and then treated with 1mol / L sodium hydroxide solution. The pH of the filtrate was adjusted to 3.5 with hydrochloric acid to precipitate the solid product. The system was cooled to 3°C and allowed to stand for 2 hours. The precipitated solid was collected by filtration. The resulting filter cake was washed three times with 20 mL of deionized water at 3°C ​​each time, followed by two times with 20 mL of ethanol at 3°C ​​each time, to remove residual salts, hydroxylamine, and small molecule impurities. Finally, the obtained solid was vacuum dried at 45°C for 10 hours to obtain 14.6 g of solid 2-(3-allylureo)benzohydroxyoxime acid monomer, with a yield of 76.1% based on methyl 2-(3-allylureo)benzoate intermediate. The monomer has a melting point of 204-206°C and undergoes slight decomposition upon melting.

[0052] The structure of the obtained monomer was determined by infrared spectroscopy (IR) and nuclear magnetic resonance (NMR) spectroscopy (NMR). 1 Characterization and confirmation were performed using 1H NMR and mass spectrometry (MS), and the results are shown in the figure. Figure 3 and Figure 4 The presence of hydroxamic acid, urea, and allyl double bonds in the monomer structure indicates that the target functional monomer has been successfully prepared.

[0053] Infrared spectroscopy display ( Figure 3 The target single cell is located in the high wavenumber region at 3377 cm⁻¹. -1 The presence of a broad absorption peak nearby can be attributed to the overlapping absorption of the O–H stretching vibration in the hydroxamic acid structure and the N–H stretching vibration of the urea group / hydroxamic acid, indicating the presence of hydroxamic acid and urea groups in the product, possibly accompanied by some hydrogen bonding. (3021 cm⁻¹) -1 The nearby absorption peak can be attributed to the =C–H stretching vibration of the aromatic ring and allyl double bond, 2927 cm⁻¹. -1 and 2883cm -1 The nearby absorption peaks can be attributed to the aliphatic C–H stretching vibrations in the allyl methylene group. In the carbonyl absorption region, at 1750 cm⁻¹… -1 A strong absorption peak appears nearby, which can be attributed to the C=O stretching vibration of the hydroxyxamic acyl group. (1584 cm⁻¹) -1 and 1508cm -1 The nearby absorption peak can be attributed to the coupled absorption of the urea group's N–H bending vibration, C–N stretching vibration, and aromatic ring skeletal vibration. (1246 cm⁻¹) -1 The nearby absorption peak can be attributed to a complex absorption of C–N, N–O, and C–O stretching vibrations; 1088 cm⁻¹ -1The nearby absorption peaks can be further attributed to the N–O stretching vibration or C–N stretching vibration of hydroxamic acid. (840 cm⁻¹) -1 and 663cm -1 The nearby absorption peaks can be attributed to the out-of-plane bending vibrations of the substituted benzene ring (C–H) and the related out-of-plane vibrations of the aromatic ring. These characteristic absorption peaks indicate that the product simultaneously contains hydroxamic acid, urea, aromatic ring, and allyl structures. Combined with the presence of characteristic absorptions related to hydroxamic acid (O–H / N–H, C=O, and N–O), it can be confirmed that the target monomer 2-(3-allylureo)benzyl hydroxamic acid has been formed.

[0054] 1H NMR (1H NMR) Figure 4 () 1 ¹H NMR, 400 MHz, DMSO-d⁶) δ: 11.21 (br s, 1H, hydroxamic acid OH), 10.19 (br s, 1H, hydroxamic acid NH), 9.65 (br s, 1H, Ar-NH-CO), 7.87–7.85 (m, 1H, Ar-H), 7.60–7.48 (m, 1H, Ar-H), 7.29–7.27 (m, 1H, Ar-H), 7.06–7.04 (m, 1H, Ar-H), 6.66 (br s, 1H, -CO-NH-CH₂-), 5.96–5.87 (m, 1H, -CH=CH₂), 5.20–5.14 (m, 2H, =CH₂), 3.84–3.82 (m, 2H, -NH-CH2-CH=CH2).

[0055] Mass spectrometry (EI-MS) shows the molecular ion peak of the target product [M]. + Appearing at m / z 235.10, with the theoretical molecular formula C of the monomer 2-(3-allylureo)benzylhydroxamic acid. 11 H 13 The N3O3 molecular weight matches the theoretical molecular weight, further proving the formation of the target monomer.

[0056] II. Preparation of Polymers for Water Treatment 0.05 mol of 2-(3-allylureo)benzylhydroxamic acid monomer, 0.375 mol of medaconic acid and 0.075 mol of 3-allyloxy-2-hydroxy-1-propanesulfonic acid were added to 200 mL of deionized water and stirred until fully dissolved. The pH of the system was adjusted to 7.1 with 30 wt.% sodium hydroxide solution to obtain a mixed monomer solution. The above mixed monomer solution was transferred to a four-necked flask equipped with a mechanical stirrer, reflux condenser, thermometer, and nitrogen inlet tube. Nitrogen gas was bubbled through the flask for 30 minutes at room temperature to remove dissolved oxygen. Subsequently, the reaction system was heated to 65°C under continuous nitrogen protection and stirring. After the temperature stabilized, an aqueous solution of ammonium persulfate initiator (0.002 mol of ammonium persulfate dissolved in 10 mL of deionized water) was added dropwise at a uniform rate over 30 minutes. After the addition was completed, the reaction was continued at 65°C for 6 hours to allow 2-(3-allylureo)benzohydroxyoxime acid, medoconic acid, and 3-allyloxy-2-hydroxy-1-propanesulfonic acid to undergo a free radical copolymerization reaction. After the reaction was completed, the resulting polymer solution was cooled to room temperature and purified by dialyzing in flowing deionized water for 72 hours using a dialysis bag with a molecular weight cutoff of 3500 Da to remove unreacted monomers, inorganic salts and small molecule impurities. The dialyzed polymer solution was freeze-dried to obtain a sponge-like solid polymer product.

[0057] The obtained polymer was characterized by infrared spectroscopy, and the results are shown in the figure. Figure 5 Infrared spectroscopy showed that the obtained polymer was at 3373 cm⁻¹ -1 The presence of a broad absorption peak nearby can be attributed to the overlapping stretching vibrations of hydroxyl groups, hydroxamic acid O–H groups, and urea / hydroxamic acid N–H groups, indicating the presence of various oxygen- and nitrogen-containing polar groups in the polymer. 2979 cm⁻¹ -1 and 2919cm -1 The nearby absorption peaks can be attributed to aliphatic C–H stretching vibrations in the polymer backbone and side chains. In the carbonyl and carboxylate absorption region, the peak at 1675 cm⁻¹... -1 The nearby absorption peaks can be attributed to the overlap of C=O absorptions related to hydroxyoxime acyl, urea carbonyl, and carboxyl groups; 1596 cm⁻¹ -1 and 1506cm -1 The nearby absorption peaks can be attributed to carboxylate COO. - A complex absorption involving asymmetric stretching vibrations, urea N–H bending vibrations, and aromatic ring skeletal vibrations. 1400 cm⁻¹ -1 and 1360cm -1 The nearby absorption peaks can be attributed to carboxylate COO. - Symmetrical stretching vibration and C–H bending vibration. 1175cm -1 1102cm -1 and 1025cm -1 The nearby absorption peak can be attributed to the S=O / S–O stretching vibration of sulfonates, and may be accompanied by complex absorptions of C–O, C–N, and N–O stretching vibrations. (975 cm⁻¹) -1 846cm -1 and 615cm -1The nearby absorption peaks can be attributed to the out-of-plane bending vibrations of the aromatic ring C–H and the low wavenumber vibrations associated with sulfonates. Compared with the 2-(3-allylureo)benzyl hydroxamic acid monomer, the characteristic absorption of the alkenyl group is significantly weakened, indicating that the carbon-carbon double bond in the monomer has participated in the free radical copolymerization reaction. The above infrared results show that the obtained product simultaneously contains hydroxamic acid groups, urea groups, carboxyl / carboxylate groups, sulfonates, aromatic rings, and polymer carbon chains, indicating that the 2-(3-allylureo)benzyl hydroxamic acid functional monomer has copolymerized with methylconacic acid and 3-allyloxy-2-hydroxy-1-propanesulfonic acid to form the target polymer.

[0058] The infrared results indicated that the obtained product simultaneously contained hydroxamic acid groups, urea groups, carboxyl / carboxylate groups, sulfonates, aromatic rings, and polymer saturated carbon chains, suggesting that the 2-(3-allylureo)benzyl hydroxamic acid functional monomer had copolymerized with methylconacic acid and 3-allyloxy-2-hydroxy-1-propanesulfonic acid to form the target scale inhibitor polymer. Gel permeation chromatography determined that the polymer's weight-average molecular weight was approximately 5.2 × 10⁻⁶. 4 Da. Based on the amount of raw materials, the polymer contains 10.0 mol% of 2-(3-allylureo)benzohydroxyoxime structural units.

[0059] III. Application Test Data ① Static scale inhibition performance test: The scale inhibition performance of calcium carbonate was tested according to GB / T 16632-2019 "Determination of Scale Inhibition Performance of Water Treatment Agents - Calcium Carbonate Deposition Method"; the scale inhibition performance of calcium sulfate was tested according to HG / T 5166-2017 "Evaluation Method for Scale Inhibition Performance of Reverse Osmosis Antiscalants" - Method B (Calcium Sulfate Deposition Method). The determination of calcium ion concentration in the solution was performed according to GB / T 15452-2009 "Determination of Calcium and Magnesium Ions in Industrial Circulating Cooling Water - EDTA Titration Method".

[0060] Preparation of Ca 2+ Concentration 300 mg / L (calculated as CaCO3), HCO3 -A 350 mg / L (calculated as CaCO3) test aqueous solution was prepared daily from calcium chloride standard solution and sodium bicarbonate standard solution. Experimental group: In a series of 250 mL stoppered conical flasks, a certain amount of water treatment agent sample solution (prepared from the polymer and water used in Example 1; polymer dosages were 2.5 mg / L, 5 mg / L, and 10 mg / L, based on the final total volume of the test solution) and the two standard solutions were added sequentially and accurately. Water was added to the specified total volume and the solution was shaken well. A control group without polymer was also prepared. All conical flasks were tightly stoppered and placed in a constant temperature water bath at 80 ± 0.5 °C for 10 hours, ensuring the water bath level was higher than the liquid level inside the flask. After the specified time, the flasks were removed and filtered while still hot using medium-speed qualitative filter paper. The filtrate was collected in a dry beaker and cooled to room temperature. The residual Ca in the filtrate was determined using EDTA complexometric titration. 2+ The concentration was determined, and the scale inhibition rate was calculated using the following formula (Equation 1) to evaluate the polymer's ability to inhibit CaCO3 deposition: , in, For scale inhibition rate, C 0 Ca before the experiment 2+ Initial concentration, C b Ca was used as the control group after the experiment. 2+ concentration, C t After the experimental group ended, Ca 2+ concentration.

[0061] Preparation of calcium hardness 1500 mg / L (calculated as CaCO3) and SO4 2- Concentration 4000 mg / L (as SO4) 2- Simulated concentrated water (calculated by volume) was used to induce a significant supersaturation of CaSO4 in the solution (SI>1.5) to simulate the harsh scaling environment of high-salt wastewater. Experimental group: Different amounts of the polymer prepared in Example 1 were added (2.5 mg / L, 5 mg / L, and 10 mg / L, respectively, based on the volume of simulated concentrated water), while a control group without polymer was prepared. The mixture was allowed to stand at 40±1℃ for 24 h. After the reaction, the precipitate was separated by filtration, and the remaining CaSO4 in the filtrate was determined by EDTA complexometric titration. 2+ The concentration is determined, and the scale inhibition rate is calculated according to Formula 1.

[0062] Each group was repeated three times, and the average value was taken. The results are shown in Table 1.

[0063] Table 1. Test data on scale inhibition performance of CaCO3 and CaSO4 under different polymer dosages.

[0064] Table 1 shows that the polymer synthesized in Example 1 exhibits good inhibition effects on both CaCO3 and CaSO4 in the static scale inhibition performance test. As the polymer dosage increased from 2.5 mg / L to 10 mg / L, the scale inhibition rates of both systems showed a significant upward trend, demonstrating a good dose-response relationship. At a low dosage of 2.5 mg / L, the scale inhibition rates for CaCO3 and CaSO4 were 63.6% and 67.7%, respectively; when the dosage increased to 5 mg / L, the scale inhibition rates increased to 84.4% and 82.2%, respectively; and when the dosage reached 10 mg / L, the scale inhibition rates for CaCO3 and CaSO4 further increased to 96.7% and 91.2%, respectively. These results indicate that the polymer can effectively inhibit the deposition of CaCO3 and CaSO4 at low dosages, possessing good static scale inhibition performance.

[0065] ② Dynamic flow erosion resistance test: In order to simulate the real working conditions of industrial circulating cooling water system under the conditions of flow, heat transfer, evaporation concentration and high shear erosion, this dynamic flow erosion resistance test is designed based on the dynamic deposition evaluation principle and combined with the dynamic simulation test method.

[0066] The test used a circulating water dynamic simulation experimental device (MTDM-Ⅱ type, Motian Electronic Instruments Co., Ltd., Gaoyou City, Jiangsu Province). The core component is a detachable test metal pipe section made of 1Cr18Ni9Ti stainless steel, with specifications of outer diameter Φ10mm, wall thickness 1.0mm, and effective heating length of 1000mm. The outer wall is equipped with an electric heating and temperature control system. Before the experiment, the pipe section was cleaned according to standard procedures, dried at 105℃ to constant weight, and its initial mass (m0) was accurately measured.

[0067] The baseline water for the CaCO3 scaling test was: calcium hardness 125 mg / L (calculated as CaCO3, provided by CaCl2), total alkalinity 250 mg / L (calculated as CaCO3, provided by NaHCO3), with 1.0% (w / w) NaCl added as background electrolyte, and the initial pH adjusted to 8.8 ± 0.1 with NaOH or HCl solution.

[0068] CaSO4 scaling test base water: calcium hardness 400 mg / L (calculated as CaCO3, provided by CaCl2), SO4 2- The concentration was added at a molar ratio of 1.1:1 to calcium ions (approximately 423 mg / L, in the form of SO42-). 2- The initial pH was adjusted to 7.0 ± 0.1 by adding 1.0% (w / w) NaCl as a background electrolyte (provided by Na2SO4).

[0069] Both sets of tests included three gradients of polymer dosage prepared in Example 1: 2.5 mg / L, 5 mg / L, and 10 mg / L, as experimental groups, and a control group without polymer addition.

[0070] During the experiment, the prepared drug-containing test water was injected into the system, and the circulation flow rate was controlled at 1.0 m / s, 2.5 m / s, and 4.0 m / s to simulate different intensities of water flow shear force. The outer wall temperature of the test tube was controlled at 70.0 ± 1.0℃, and the system inlet water temperature was maintained at 40.0 ± 1.0℃. During the experiment, deionized water was automatically replenished to compensate for evaporation loss, and the system operated continuously for 24 hours. After the experiment, the test tube was carefully disassembled, and the inner wall and both ends of the tube were gently rinsed to remove loosely attached impurities. The tube was then placed in a forced-air drying oven at 60 ± 2℃ to dry to constant weight. After cooling to room temperature in a desiccator, the total mass (m1) of the scale was immediately weighed using the same precision analytical balance.

[0071] Deposition amount per unit internal surface area W (mg / cm²) 2 Calculate using the following formula: , Where A is the effective inner surface area (cm²) of the test pipe section. 2 ).

[0072] scale inhibition rate Calculate using the following formula: , In the formula, W 0 The deposition rate per unit internal surface area (mg / cm²) is for the control group. W 1 This represents the deposition rate per unit internal surface area (mg / cm²) in the experimental group. The study compared different polymer dosage groups at the same flow rate. W Evaluate scale inhibition efficiency and analyze the effects of the same dosage. W The rate of change of the flow rate with increasing flow velocity (1.0 m / s → 4.0 m / s) was used to quantitatively evaluate the erosion stability of the polymer. The results are shown in Table 2.

[0073] Table 2. Test data on dynamic flow erosion resistance under different polymer dosages.

[0074] Table 2 shows the erosion resistance of the polymer under dynamic flow conditions. As the flow velocity increased from 1.0 m / s to 4.0 m / s, the deposition of CaCO3 and CaSO4 in the control group increased, indicating that scaling was still significant under high-flow-velocity dynamic conditions. At a polymer dosage of 5 mg / L, the scale inhibition rates of CaCO3 and CaSO4 remained above 81% and 82%, respectively, within the range of 1.0–4.0 m / s, indicating that the polymer exhibited good erosion resistance at this dosage. When the dosage increased to 10 mg / L, the scale inhibition rates of both scale types remained above 91% at all flow velocities, with the inhibition rates for CaCO3 and CaSO4 still reaching 93.8% and 93.4%, respectively, under a high flow velocity of 4.0 m / s. These results indicate that when the polymer dosage reaches a certain level, it can form a relatively stable interfacial adsorption layer under dynamic flow conditions, thereby effectively improving the erosion resistance and scale inhibition performance.

[0075] ③Reverse osmosis membrane dynamic scale inhibition performance test This test uses the dynamic membrane filtration evaluation method to simulate the actual scaling conditions of a reverse osmosis (RO) membrane system under high pressure, cross-flow filtration, and high concentration conditions.

[0076] CaCO3 scaling test water: calcium hardness 200 mg / L (calculated as CaCO3, provided by CaCl2), total alkalinity 400 mg / L (calculated as CaCO3, provided by NaHCO3), 1000 mg / L NaCl added as background electrolyte, and the initial pH adjusted to 7.8 ± 0.1 with NaOH or HCl solution.

[0077] CaSO4 scaling test water: calcium hardness 400 mg / L (calculated as CaCO3, provided by CaCl2), SO4 2- Add at a concentration of approximately 423 mg / L (approximately 1.1:1 molar ratio to calcium ions, in the form of SO42-) 2- (Calculated by using Na2SO4), add 1000 mg / L NaCl as background electrolyte, and adjust the initial pH to 7.0 ± 0.1.

[0078] Both sets of tests included three dosage gradients (2.5 mg / L, 5 mg / L, 10 mg / L) of the polymer prepared in Example 1 as experimental groups, and a blank control group without polymer addition.

[0079] The assembled flat-plate reverse osmosis membrane element was placed in a Sepa CF II flat-plate cross-flow filtration experimental apparatus (Beijing Pinchaosiri Technology Co., Ltd.) and pre-pressurized for 30 minutes at 1.55 MPa and 25.0 ± 0.5℃. The initial permeate flux was then measured. J w0The test system was continuously run, with the permeate flux recorded every 30 minutes for 24 hours. The permeate flux at the end of the run was also recorded. J Wt Calculate the final flux decline rate using the following formula. J d : ; The dynamic scale inhibition rate η is calculated using the following formula: , In the formula, J d0 The final flux reduction rate is for the control group (without polymer). J d1 The final flux decline rate for the experimental group is shown. After the operation, the system was rinsed with deionized water, then the membrane elements were cleaned with a 0.1% citric acid solution under low-pressure circulation for 30 minutes, and finally rinsed clean with deionized water. The permeate flux was then measured again under the initial test conditions. J W1 Calculate the flux recovery rate (FRR) using the following formula: .

[0080] The test results are shown in Table 3.

[0081] Table 3. Test data on the dynamic scale inhibition performance of the reverse osmosis membrane of the polymer prepared in Example 1.

[0082] Table 3 shows the dynamic test results of the reverse osmosis membrane. The data shows that the polymer can significantly inhibit scaling on the membrane surface and slow down the decline in permeate flux. As the dosage increased from 2.5 mg / L to 10 mg / L, the final flux reduction rate of both the CaCO3 and CaSO4 systems gradually decreased, while the corresponding dynamic scale inhibition rate gradually increased. At a dosage of 10 mg / L, the final flux reduction rates of CaCO3 and CaSO4 were only 2.8% and 4.1%, respectively, corresponding to dynamic scale inhibition rates of 94.2% and 90.9%, respectively; simultaneously, the flux recovery rates after cleaning reached 97.5% and 96.8%, respectively, indicating that membrane surface deposition was effectively inhibited and the flux recovery after cleaning was good. At a dosage of 5 mg / L, the dynamic scale inhibition rates of CaCO3 and CaSO4 were 85.2% and 79.1%, respectively, still showing good membrane surface scale inhibition effects. These results indicate that the polymer can effectively inhibit the deposition of inorganic salt scale on the membrane surface under dynamic cross-flow filtration conditions and is suitable for membrane water treatment systems such as reverse osmosis.

[0083] ④ High temperature and high salt resistance limit test To simulate the long-term operation of an industrial circulating water system under extreme conditions of high temperature and high salinity, and to evaluate the chemical stability and durability of polymers under these conditions, this high-temperature and high-salinity limit performance test was designed. The test was conducted using a circulating water dynamic simulation experimental device (MTDM-Ⅱ type, Motian Electronic Instruments Co., Ltd., Gaoyou City, Jiangsu Province). The core test pipe section specifications were the same as those used in the dynamic erosion resistance test (material 1Cr18Ni9Ti stainless steel, outer diameter Φ10mm, effective heating length 1000mm). Before the experiment, the pipe section underwent standardized cleaning, drying, and initial mass (m0).

[0084] Test base water formulation (high salinity background): A high concentration of sodium chloride was used to simulate a salinity background, and supersaturated scale-forming ions were added: CaCO3 scaling test water: calcium hardness 125 mg / L (calculated as CaCO3, provided by CaCl2), total alkalinity 250 mg / L (calculated as CaCO3, provided by NaHCO3), background electrolyte NaCl concentration 3.5% (w / w). Adjust the initial pH to 8.8 ± 0.1 with NaOH or HCl solution.

[0085] CaSO4 scaling test water: calcium hardness 400 mg / L (calculated as CaCO3, provided by CaCl2), SO4 2- Add at a concentration of approximately 900 mg / L (approximately 1.1:1 molar ratio to calcium ions, in the form of SO42-) 2- The initial pH was adjusted to 7.0 ± 0.1, with the background electrolyte NaCl concentration being 3.5% (w / w) provided by Na2SO4.

[0086] Both sets of tests included three gradients of polymer dosage prepared in Example 1: 2.5 mg / L, 5 mg / L, and 10 mg / L, as experimental groups, and a control group without polymer addition.

[0087] During the experiment, the prepared test water containing the drug was injected into the system. The circulation flow rate was controlled at 1.0 m / s, and the temperature of the outer wall of the test pipe section was raised to 85.0 ± 1.0℃, while the system inlet water temperature was maintained at 45.0 ± 1.0℃; the experiment was run continuously for 72 hours.

[0088] After the experiment, the test tube section was carefully disassembled and its outer wall and both ends were gently rinsed with deionized water to remove any loosely attached impurities. The tube section was then placed in a forced-air drying oven at 60±2℃ to dry to constant weight. After cooling to room temperature in a desiccator, the total mass (m1) of the tube with scale was immediately weighed using the same precision analytical balance.

[0089] Deposition amount per unit internal surface area W (mg / cm²) 2 Calculate using the following formula: , Where A is the effective inner surface area (cm²) of the test pipe section. 2 ).

[0090] The scale inhibition rate η is calculated using the following formula: , In the formula, W 0 The deposition rate per unit internal surface area (mg / cm²) is for the control group. W 1 This represents the deposition rate per unit internal surface area (mg / cm²) in the experimental group. The study compared different polymer dosage groups at the same flow rate. W The scale inhibition efficiency was evaluated, and the high-temperature and high-salt resistance limits of the polymer were quantitatively assessed. The results are shown in Table 4.

[0091] Table 4. Test data on the high temperature and high salt resistance limits of the polymer prepared in Example 1.

[0092] Table 4 shows the long-term scale inhibition performance of the polymer after 72 hours of continuous operation under high temperature (85℃) and high salinity (3.5% NaCl) conditions. As the dosage increased from 2.5 mg / L to 10 mg / L, the deposition of both CaCO3 and CaSO4 decreased significantly, while the scale inhibition rate gradually increased. At a dosage of 10 mg / L, the scale inhibition rates for CaCO3 and CaSO4 reached 89.1% and 80.7%, respectively, indicating that the polymer maintains good scale inhibition activity even under harsh operating conditions. At a dosage of 5 mg / L, the scale inhibition rate for CaCO3 was 72.1%, and for CaSO4 it was 59.4%, a significant decrease compared to 10 mg / L, indicating that increasing the dosage helps maintain the scale inhibition effect under high temperature, high salinity, and long-term operation conditions. Compared with the dynamic flow erosion test, this experiment had a longer operating time and higher salinity. Even with sufficient dosage, the polymer effectively inhibited the deposition of CaCO3 and CaSO4, making it suitable for industrial circulating water systems under high temperature and high salinity conditions.

[0093] Example 2 I. Preparation of 2-(3-allylureo)benzylhydroxamic acid monomer (1) Add 0.10 mol of methyl 2-aminobenzoate and 150 mL of anhydrous acetonitrile to a dry three-necked flask. After stirring and dissolving, cool the reaction system to 4 °C under nitrogen protection and stirring. Then, slowly add 0.11 mol of allyl isocyanate dropwise over 40 minutes, controlling the temperature of the reaction system at 6 °C during the dropwise addition. After the dropwise addition is complete, raise the temperature of the reaction system to 28 °C and continue stirring for 6 hours. After the reaction is completed, concentrate the solution to 60 mL under reduced pressure at 40 °C to obtain a concentrated solution. Slowly pour the concentrated solution into 500 mL of deionized water to precipitate the solid product. Collect the precipitated solid by filtration and wash it three times with deionized water. The obtained solid is recrystallized from an ethanol-water mixed solvent (ethanol to water volume ratio of 4:1) and dried under vacuum at 40 °C for 12 hours to obtain 18.9 g of solid methyl 2-(3-allylureo)benzoate intermediate, with a yield of 80.8%.

[0094] (2) Add the methyl 2-(3-allylureo)benzoate intermediate obtained in step (1) to a methanol / water mixed solvent (110 mL methanol and 50 mL deionized water), stir to disperse it fully, and obtain an intermediate dispersion; separately add 0.25 mol hydroxylamine hydrochloride to a methanol / water mixed solvent (40 mL methanol and 40 mL deionized water), stir to dissolve, cool the system to 10 °C, and then slowly add 30 wt.% sodium hydroxide solution to adjust the pH of the system to 8.3, and obtain hydroxylamine reaction solution.

[0095] (3) Under stirring conditions, the hydroxylamine reaction solution obtained in step (2) was added dropwise to the intermediate dispersion obtained in step (2) within 40 minutes. During the dropwise addition, the temperature of the reaction system was controlled at 0°C. After the dropwise addition was completed, the temperature of the reaction system was raised to 25°C, and the pH of the system was maintained at 8.3 with 30wt.% sodium hydroxide solution. The reaction was continued to be stirred for 8 hours. After the reaction was completed, the resulting reaction solution was cooled to 25°C, filtered to remove a small amount of insoluble matter, and then the pH of the filtrate was adjusted to 3.6 with 1mol / L hydrochloric acid so that the solid... The product precipitated; the system was cooled to 0℃ and allowed to stand for 1 hour. The precipitated solid was collected by filtration. The resulting filter cake was washed three times with 20 mL of deionized water at 4℃ each time; then washed twice with 20 mL of ethanol at 4℃ each time to remove residual salts, hydroxylamine and small molecule impurities; finally, the obtained solid was vacuum dried at 35℃ for 16 hours to obtain 13.8 g of solid 2-(3-allylureo)benzohydroxyoxime acid monomer, with a yield of 72.7% based on methyl 2-(3-allylureo)benzoate intermediate.

[0096] II. Preparation of Polymers for Water Treatment 0.025 mol of 2-(3-allylureo)benzylhydroxamic acid monomer, 0.3 mol of citralic acid, and 0.175 mol of sodium 2-methyl-2-propen-1-sulfonate were added to 200 mL of deionized water and stirred until fully dissolved. The pH of the system was adjusted to 7.2 with 30 wt.% sodium hydroxide solution to obtain a mixed monomer solution.

[0097] The above mixed monomer solution was transferred to a four-necked flask equipped with a mechanical stirrer, reflux condenser, thermometer, and nitrogen inlet tube. Nitrogen gas was bubbled through the flask at 25°C for 30 minutes to remove dissolved oxygen from the system. Subsequently, under continuous nitrogen protection and stirring, the reaction system was heated to 40°C. After the temperature stabilized, an aqueous solution of ammonium persulfate initiator (0.002 mol of ammonium persulfate dissolved in 10 mL of deionized water) was added dropwise at a uniform rate over 30 minutes. After the addition was completed, the reaction was continued at 40°C for 7 hours to allow 2-(3-allylureo)benzohydroxyoxime acid, citralic acid, and sodium 2-methyl-2-propene-1-sulfonate to undergo a free radical copolymerization reaction. After the reaction was completed, the resulting polymer solution was cooled to 25°C and purified by dialyzing in flowing deionized water for 72 hours using a dialysis bag with a molecular weight cutoff of 3500 Da to remove unreacted monomers, inorganic salts and small molecule impurities. The dialyzed polymer solution was freeze-dried to obtain a sponge-like solid polymer product.

[0098] The weight-average molecular weight of the polymer was determined to be 4.5 × 10⁻⁶ by gel permeation chromatography. 4 Da. Based on the amount of raw materials, the polymer contains 5.0 mol% of 2-(3-allylureo)benzohydroxyoxime structural units.

[0099] III. Application Test Data The performance of the water treatment polymer prepared in this embodiment was evaluated according to the static scale inhibition performance test method, dynamic flow erosion resistance test method, reverse osmosis membrane dynamic scale inhibition performance test method and high temperature and high salt resistance limit test method described in Example 1. The results are shown in Table 5.

[0100] Table 5. Scale inhibition performance test data of the polymer obtained in Example 2

[0101] Table 5 shows the comprehensive scale inhibition performance test data of the polymer prepared in Example 2 (functional monomer content of 5.0 mol%). As can be seen from Table 5, at a dosage of 10 mg / L, the static scale inhibition rates of this polymer for CaCO3 and CaSO4 were 94.6% and 90.3%, respectively, indicating that even with a low functional monomer content, the polymer can effectively inhibit the nucleation and growth of CaCO3 and CaSO4 crystals. In the dynamic flow erosion resistance test, at a dosage of 10 mg / L, 4.0 m / s, and 70°C, the scale inhibition rates for CaCO3 and CaSO4 were 87.2% and 86.1%, respectively, indicating that the introduction of a small amount of ortho-hydroxyoxime acid-urea structural units can improve the interfacial adhesion stability of the polymer under high shear conditions. In the reverse osmosis membrane dynamic scale inhibition test, the scale inhibition rates for CaCO3 and CaSO4 were 89.5% and 87.0%, respectively, indicating that this polymer can slow down the deposition of inorganic salt scale under cross-flow conditions at the membrane surface. In high-temperature and high-salt resistance tests, the scale inhibition rates for CaCO3 and CaSO4 were 86.4% and 76.9%, respectively, indicating that the polymer still possesses a certain degree of long-lasting scale inhibition capability under harsh operating conditions. These results demonstrate that when the content of the 2-(3-allylureo)benzyl hydroxamic acid structural unit is 5.0 mol%, the polymer exhibits good static scale inhibition, dynamic erosion resistance, and film-based scale inhibition performance. The introduction of the ortho-hydroxamic acid-urea structural unit can improve the polymer's interfacial anchoring ability, and appropriately increasing the content of this functional monomer is beneficial to further enhance the polymer's long-lasting scale inhibition performance under dynamic high-shear and high-temperature and high-salt conditions.

[0102] Example 3 I. Preparation of 2-(3-allylureo)benzylhydroxamic acid monomer (1) Add 0.10 mol of methyl 2-aminobenzoate and 150 mL of anhydrous acetonitrile to a dry three-necked flask. After stirring and dissolving, cool the reaction system to 5°C under nitrogen protection and stirring. Then, slowly add 0.12 mol of allyl isocyanate dropwise over 40 minutes, controlling the temperature of the reaction system at 8°C during the dropwise addition. After the dropwise addition is complete, raise the temperature of the reaction system to 35°C and continue stirring for 4 hours. After the reaction is completed, concentrate the solution to 60 mL under reduced pressure at 40°C to obtain a concentrated solution. Slowly pour the concentrated solution into 500 mL of deionized water to precipitate the solid product. Collect the solid by filtration and wash it three times with deionized water. The obtained solid is recrystallized from an ethanol-water mixed solvent (ethanol to water volume ratio of 5:1) and dried under vacuum at 40°C for 12 hours to obtain 18.6 g of methyl 2-(3-allylureo)benzoate intermediate, with a yield of 79.5%.

[0103] (2) Add the methyl 2-(3-allylureo)benzoate intermediate obtained in step (1) to a methanol / water mixed solvent (110 mL methanol and 50 mL deionized water), stir to disperse it fully, and obtain an intermediate dispersion; separately add 0.18 mol hydroxylamine hydrochloride to a methanol / water mixed solvent (40 mL methanol and 40 mL deionized water), stir to dissolve, cool the system to 0°C, slowly add 30 wt.% sodium hydroxide solution to adjust the pH to 8.4, and obtain hydroxylamine reaction solution.

[0104] (3) Under stirring conditions, the hydroxylamine reaction solution obtained in step (2) was added dropwise to the intermediate dispersion obtained in step (2) within 40 minutes. During the dropwise addition, the temperature of the reaction system was controlled at 5°C. After the dropwise addition was completed, the temperature of the reaction system was raised to 40°C, and the pH of the system was maintained at 8.0 with 30wt.% sodium hydroxide solution. The reaction was stirred for 2 hours. After the reaction was completed, the reaction solution was cooled to 25°C, and a small amount of insoluble matter was removed by filtration. Then, the pH of the filtrate was adjusted to 4.5 with 1mol / L hydrochloric acid to produce solid product. The product precipitated; the system was cooled to 10°C and allowed to stand for 6 hours. The precipitated solid was collected by filtration. The resulting filter cake was washed three times with 20 mL of deionized water at 4°C each time; then washed twice with 20 mL of ethanol at 4°C each time to remove residual salts, hydroxylamine, and small molecule impurities; finally, the obtained solid was vacuum dried at 50°C for 8 hours to obtain 14.05 g of solid 2-(3-allylureo)benzohydroxyoxime acid monomer, with a yield of 75.2% based on methyl 2-(3-allylureo)benzoate intermediate.

[0105] II. Preparation of Polymers for Water Treatment 0.1 mol of 2-(3-allylureo)benzylhydroxamic acid monomer, 0.24 mol of aconitic acid and 0.16 mol of p-vinylbenzenesulfonic acid were added to 200 mL of deionized water and stirred until fully dissolved. The pH of the system was adjusted to 7.0 with 30 wt.% sodium hydroxide solution to obtain a mixed monomer solution. The above mixed monomer solution was transferred to a four-necked flask equipped with a mechanical stirrer, reflux condenser, thermometer, and nitrogen inlet tube. Nitrogen gas was bubbled through the flask at 25°C for 30 minutes to remove oxygen. Subsequently, under continuous nitrogen protection and stirring, the reaction system was heated to 80°C. After the temperature stabilized, potassium persulfate initiator aqueous solution (0.0015 mol potassium persulfate dissolved in 10 mL deionized water) was added dropwise at a uniform rate over 30 minutes. After the addition was completed, the reaction was continued at 80°C for 4 hours to allow 2-(3-allylureo)benzyl hydroxamic acid, aconitic acid, and p-vinylbenzenesulfonic acid to undergo free radical copolymerization. After the reaction was completed, the resulting polymer solution was cooled to 25°C and purified by dialyzing in flowing deionized water for 72 hours using a dialysis bag with a molecular weight cutoff of 3500 Da. The polymer solution after dialyzing was freeze-dried to obtain a sponge-like solid polymer.

[0106] The weight-average molecular weight, as determined by gel permeation chromatography, is approximately 5.8 × 10⁻⁶. 4 Da. Based on the amount of raw materials, the polymer contains 20.0 mol% of 2-(3-allylureo)benzohydroxyoxime structural units.

[0107] III. Application Test Data The performance of the water treatment polymer prepared in this embodiment was evaluated according to the static scale inhibition performance test method, dynamic flow erosion resistance test method, reverse osmosis membrane dynamic scale inhibition performance test method and high temperature and high salt resistance limit performance test method described in Example 1. The results are shown in Table 6.

[0108] Table 6. Scale inhibition performance test data of the polymer obtained in Example 3

[0109] Table 6 shows the comprehensive scale inhibition performance test data of the polymer (functional monomer content 20.0 mol%) prepared in Example 3. In the static scale inhibition test, the scale inhibition rates for CaCO3 and CaSO4 at a dosage of 10 mg / L were 95.6% and 90.7%, respectively, indicating that the polymer can still effectively inhibit crystal nucleation and crystal growth under high functional monomer content conditions. In the dynamic flow erosion resistance test, the scale inhibition rates for CaCO3 and CaSO4 at a dosage of 10 mg / L and a flow rate of 4.0 m / s were 95.0% and 94.1%, respectively. In the reverse osmosis membrane dynamic scale inhibition test, the dynamic scale inhibition rates for CaCO3 and CaSO4 were 94.8% and 91.9%, respectively, which are improved compared to Examples 1 and 2, but the improvement is limited. This indicates that after the functional monomer content is increased to 20.0 mol%, the interfacial anchoring stability of the polymer under high shear and membrane surface conditions is further enhanced, but it has already approached the performance improvement plateau. In the high temperature and high salt resistance test, the scale inhibition rates of CaCO3 and CaSO4 at a dosage of 10 mg / L were 95.8% and 87.3%, respectively, indicating that the polymer still has good and long-lasting scale inhibition ability under harsh conditions.

[0110] The above examples demonstrate that, within the functional monomer content range of 5-20 mol%, the scale inhibition performance of the polymer exhibits significant differences with variations in the functional monomer ratio. When the functional monomer content is 5.0 mol% (Example 2), the polymer already possesses good static scale inhibition capability, but its dynamic anti-scouring, reverse osmosis membrane scale inhibition, and high-temperature and high-salt resistance are relatively limited. When the functional monomer content increases to 10.0 mol% (Example 1), the polymer exhibits a relatively balanced comprehensive performance among static scale inhibition, dynamic anti-scouring, reverse osmosis membrane scale inhibition, and high-temperature and high-salt resistance. When the functional monomer content is further increased to 20.0 mol% (Example 3), the polymer's dynamic persistent scale inhibition, membrane surface stability, and high-temperature and high-salt resistance are enhanced, but its static scale inhibition performance no longer improves. This indicates that while an excessively high proportion of ortho-hydroxyoxime acid-urea dual anchoring units is beneficial for enhancing interfacial interactions, it relatively reduces the contribution of carboxylic acid units and sulfonic acid units to the complexation and dispersion in the aqueous phase. Therefore, by adjusting the proportion of functional units, an optimal match can be achieved between basic scale inhibition and dispersion capabilities and interface anchoring stability under different operating conditions.

[0111] Example 4 I. The preparation of 2-(3-allylureo)benzylhydroxamic acid monomer is the same as in Example 1.

[0112] II. Preparation of Polymers for Water Treatment The 0.05 mol of 2-(3-allylureo)benzylhydroxamic acid monomer, 0.375 mol of citralic acid, and 0.075 mol of 3-allyloxy-2-hydroxy-1-propanesulfonic acid were replaced with 0.05 mol of 2-(3-allylureo)benzylhydroxamic acid monomer, 0.034 mol of citralic acid, 0.334 mol of citralic acid, 0.067 mol of 3-allyloxy-2-hydroxy-1-propanesulfonic acid, and 0.015 mol of (2-acryloylaminoethyl)phosphonic acid, while the other steps were the same as in Example 1.

[0113] Based on the amount of feed, the polymer contains 10.0 mol of 2-(3-allylureo)benzohydroxyoxime structural units.

[0114] III. Application Test Data The performance of the water treatment polymer prepared in this embodiment was evaluated according to the static scale inhibition performance test method (adding the static scale inhibition performance test of Ca3(PO4)2, and the static scale inhibition performance test of Ca3(PO4)2 refers to the static scale inhibition performance test of CaCO3), the dynamic flow erosion resistance test method, the reverse osmosis membrane dynamic scale inhibition performance test method, and the high temperature and high salt limit performance test method described in Example 1. The results are shown in Table 7.

[0115] Table 7. Scale inhibition performance test data of the polymer obtained in Example 4

[0116] Table 7 shows the comprehensive scale inhibition performance test data of the polymer prepared in Example 4. While maintaining the content of the 2-(3-allylureo)benzylhydroxyxamic acid functional monomer at 10.0 mol%, this example further introduces a phosphonic acid-containing monomer, d. As shown in Table 7, at a dosage of 10 mg / L, this polymer maintains high static and dynamic scale inhibition rates for both CaCO3 and CaSO4, demonstrating good basic scale inhibition ability. Notably, the polymer achieved a scale inhibition rate of 88.3% in the static scale inhibition test of Ca3(PO4)2, demonstrating the effective inhibition effect of the phosphonic acid structure on calcium phosphate scale. This indicates that the polymer of Example 4 not only maintains stable scale inhibition performance for calcium carbonate and calcium sulfate but also expands its applicability to calcium phosphate scale, making it suitable for long-term operation in high-salinity wastewater and complex operating conditions.

[0117] Comparative Example 1 Without adding 2-(3-allylureo)benzylhydroxamic acid monomer, the other steps were the same as in Example 1, and the test results are shown in Table 8.

[0118] Table 8. Scale inhibition performance test data of the polymer prepared in Comparative Example 1

[0119] In static scale inhibition tests, Comparative Example 1 showed scale inhibition rates of 78.4% and 73.2% for CaCO3 and CaSO4, respectively, indicating that the polymer itself, a copolymer of methyl methacrylate and 3-allyloxy-2-hydroxy-1-propanesulfonic acid, possesses certain basic chelating and dispersing capabilities. However, its performance significantly decreased under dynamic flow and harsh operating conditions: under high shear conditions of 4.0 m / s, the scale inhibition rates for CaCO3 and CaSO4 were 70.1% and 66.7%, respectively, a decrease of approximately 8–9 percentage points compared to static scale inhibition; in reverse osmosis membrane dynamic scale inhibition and high-temperature and high-salt resistance tests, the scale inhibition rates further decreased, to 71.5% / 68.3% (RO scale inhibition) and 68.7% / 63.4% (high-temperature and high-salt resistance), respectively, indicating that the polymer lacks stable interfacial adhesion under high shear, high temperature, and high-salt environments. These results suggest that the introduction of functional monomer a plays a crucial role in improving the polymer's long-term scale inhibition performance under dynamic, high-shear, and high-temperature and high-salt conditions. The ortho-hydroxyoxime-urea group structure in functional monomer a can form multi-point interface anchoring, which is in stark contrast to the basic polymer in Comparative Example 1 that only contains carboxyl and sulfonic acid groups, and significantly improves the adhesion stability of the polymer at the metal or scale interface.

[0120] Comparative Example 2 The 2-(3-allylureo)benzylhydroxamic acid monomer was replaced with 1-allyl-3-phenylurea (CAS: 2835-30-5), and the other steps were the same as in Example 1. The results are shown in Table 9.

[0121] Table 9. Scale inhibition performance test data of the polymer prepared in Comparative Example 2

[0122] Table 9 shows the scale inhibition performance test data of the polymer prepared in Comparative Example 2. The 1-allyl-3-phenylurea monomer used in Comparative Example 2 contains a benzene ring, a urea group, and a polymerizable allyl double bond, but does not contain a hydroxamic acid group. As can be seen from Table 9, the static scale inhibition rate of Comparative Example 2 is lower than that of Example 1, which contains an ortho-hydroxamic acid-urea group structure, and the decrease is more significant under dynamic flow, reverse osmosis membrane dynamic scale inhibition, and high temperature and high salt conditions. This result indicates that it is difficult to form a stable multi-point interfacial structure by introducing an aromatic urea group alone without the coordination or strong polar anchoring effect of the hydroxamic acid group. Therefore, the advantage of functional monomer a in Example 1 does not only come from the benzene ring or urea group, but mainly from the synergistic effect of the hydroxamic acid group and the urea group in the ortho-position structure.

[0123] Comparative Example 3 The 2-(3-allylureo)benzohydroxyxamic acid monomer was replaced with 4-vinylbenzohydroxyxamic acid (CAS: 24363-16-4), and the other steps were the same as in Example 1. The results are shown in Table 10.

[0124] Table 10. Scale inhibition performance test data of the polymer prepared in Comparative Example 3

[0125] Table 10 shows the scale inhibition performance test data of the polymer prepared in Comparative Example 3. The 4-vinylbenzyl hydroxamic acid monomer used in Comparative Example 3 contains hydroxamic acid groups and polymerizable vinyl structures, but does not contain urea groups. As can be seen from Table 10, the scale inhibition rate of Comparative Example 3 in dynamic flow erosion resistance, reverse osmosis membrane dynamic scale inhibition, and high temperature and high salt resistance tests is significantly lower than that of Example 1, especially under dynamic flow conditions of 4.0 m / s and 70℃, the scale inhibition rates for CaCO3 and CaSO4 are only 71.3% and 68.1%, respectively. The above results indicate that introducing only hydroxamic acid groups but lacking the multiple hydrogen bonding effects provided by urea groups makes it difficult to form a stable multi-point interfacial layer on scale crystals, metal, or membrane surfaces. Therefore, its dynamic erosion resistance and long-term scale inhibition performance under harsh conditions are significantly insufficient.

[0126] Comparative Example 4 The 0.05 mol of 2-(3-allylureo)benzylhydroxamic acid monomer was replaced with 0.05 mol of 1-allyl-3-phenylurea (CAS: 2835-30-5) and 0.05 mol of 4-vinylbenzylhydroxamic acid (CAS: 24363-16-4), and the amount of methylconazole was adjusted to 0.333 mol, and the amount of 3-allyloxy-2-hydroxy-1-propanesulfonic acid was adjusted to 0.067 mol. The other steps were the same as in Example 1. The results are shown in Table 11.

[0127] Table 11 Scale inhibition performance test data of the polymer prepared in Comparative Example 3

[0128] Table 11 shows the scale inhibition performance test data of the polymer prepared in Comparative Example 4. Comparative Example 4 simultaneously introduced 1-allyl-3-phenylurea and 4-vinylbenzylhydroxamic acid, so that the polymer chain contained both urea groups and hydroxamic acid groups. However, the two types of groups originated from different polymerizable monomers and were randomly distributed in the polymer chain, failing to form the pre-organized double-anchored structure in Example 1 where the hydroxamic acid group and the urea group were fixed at the adjacent position of the same aromatic ring.

[0129] As shown in Table 11, in the tests of dynamic flow erosion resistance, reverse osmosis membrane dynamic scale inhibition, and high temperature and high salt resistance, the scale inhibition rate of Comparative Example 4 was significantly lower than that of Example 1. Under dynamic flow conditions of 4.0 m / s and 70℃, the scale inhibition rates of Comparative Example 4 for CaCO3 and CaSO4 were 78.7% and 75.2%, respectively, which were lower than those of Example 1 (93.8% and 93.4%). Under high temperature and high salt resistance conditions, the scale inhibition rates for CaCO3 and CaSO4 were 77.4% and 70.6%, respectively, which were also significantly lower than those of Example 1.

[0130] The above results indicate that even when hydroxamic acid and urea groups are introduced simultaneously into the polymer chain, if they belong to different monomers and are randomly distributed, it is still difficult to maintain a fixed spatial distance and relative orientation, and a stable intramolecular double-anchoring interface effect cannot be formed. In contrast, the 2-(3-allylureo)benzyl hydroxamic acid monomer in Example 1 fixes the hydroxamic acid and urea groups in the same aromatic ring ortho position, forming an ortho-hydroxamic acid-urea double-anchoring structure with spatial pre-organization characteristics, thereby significantly improving the interfacial adhesion stability and long-lasting scale inhibition performance of the polymer under dynamic high shear, reverse osmosis membrane crossflow, and high temperature and high salt conditions.

Claims

1. A polymer for water treatment, characterized in that... It is obtained by free radical copolymerization of mixed monomers, wherein the mixed monomers include monomer a, monomer b, and monomer c. Monomer a is a 2-(3-allylureo)benzylhydroxamic acid monomer, and the structural formula of monomer a is as follows: ； Monomer b is at least one of citralic acid, aconitic acid, or citric acid; Monomer c is at least one of 3-allyloxy-2-hydroxy-1-propanesulfonic acid, sodium 2-methyl-2-propene-1-sulfonate, or p-vinylbenzenesulfonic acid.

2. The polymer for water treatment according to claim 1, characterized in that... The mixed monomers also include monomer d, which is at least one of allylphosphonic acid, vinylphosphonic acid, dimethyl vinylphosphonate, isopropenylphosphonic acid, or (2-acryloylaminoethyl)phosphonic acid.

3. The polymer for water treatment according to claim 1, characterized in that... The content of monomer a in the mixed monomers is 5-20 mol%, the molar ratio of monomer b to monomer a is 2-12:1, and the molar ratio of monomer c to monomer a is 1-7:

1.

4. The polymer for water treatment according to claim 1, characterized in that... The weight-average molecular weight of polymers used in water treatment is 20,000-100,000 Da.

5. The polymer for water treatment according to claim 1, characterized in that... The free radical copolymerization reaction is a free radical polymerization reaction carried out in water or a mixture of water and a water-miscible organic solvent using an initiator. The water-miscible organic solvent is one or more of methanol, ethanol, isopropanol, acetone, tetrahydrofuran, N,N-dimethylformamide, or dimethyl sulfoxide. The polymerization temperature is 40-80℃, the polymerization time is 4-8 hours, and the initiator is at least one of ammonium persulfate, potassium persulfate, hydrogen peroxide, a persulfate / bisulfite redox initiation system, or a hydrogen peroxide / ascorbic acid redox initiation system.

6. The polymer for water treatment according to claim 1, characterized in that... The method for preparing 2-(3-allylureo)benzylhydroxamic acid monomer includes the following steps: (1) Methyl 2-aminobenzoate was dissolved or dispersed in an anhydrous organic solvent. Under nitrogen protection and stirring, allyl isocyanate was added dropwise. After the addition was complete, the reaction was stirred. After the reaction was completed, the solution was concentrated under reduced pressure to obtain a concentrated solution. The concentrated solution was treated to obtain a crude product. The crude product was purified and dried to obtain methyl 2-(3-allylureo)benzoate intermediate. (2) Add the methyl 2-(3-allylureo)benzoate intermediate obtained in step (1) to the first solvent and stir to dissolve or disperse to obtain an intermediate solution or intermediate dispersion; add hydroxylamine hydrochloride to the second solvent and stir to dissolve, cool down, add alkaline reagent to adjust pH to obtain hydroxylamine reaction solution; (3) Add the hydroxylamine reaction solution to the intermediate solution or intermediate dispersion, stir the reaction, cool the resulting reaction solution to room temperature, filter, adjust the pH of the filtrate, let it stand, filter, wash the resulting filter cake, and vacuum dry to obtain 2-(3-allylureo)benzylhydroxyoxime monomer.

7. The polymer for water treatment according to claim 6, characterized in that... In step (1), the molar ratio of methyl 2-aminobenzoate and allyl isocyanate is 1:1.1-1.

2. The anhydrous organic solvent is one or more of tetrahydrofuran, acetonitrile, dichloromethane, N,N-dimethylformamide or dimethyl sulfoxide. The dropping temperature is 0-10℃, the stirring reaction temperature is 25-35℃, and the stirring reaction time is 4-8 hours. The concentrated solution treatment step is to pour the concentrated solution into deionized water to precipitate the solid, filter and collect the precipitated solid to obtain the crude product, or to extract the concentrated solution with ethyl acetate, collect the organic phase and wash it successively with deionized water and saturated sodium chloride solution, and obtain the crude product after drying, filtration and vacuum concentration. The purification is one or both of recrystallization or washing.

8. The polymer for water treatment according to claim 6, characterized in that... In step (2), the first solvent is one or more of methanol, water, ethanol or N,N-dimethylformamide, the second solvent is one or more of methanol, water or ethanol, the temperature is lowered to 0-10℃, the molar ratio of methyl 2-(3-allylureo)benzoate intermediate to hydroxylamine hydrochloride is 1:2.0-4.0, the alkaline reagent is one or more of sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, potassium carbonate solution, sodium methoxide or sodium ethoxide, and the pH is adjusted to 8.3-8.

5.

9. The polymer for water treatment according to claim 6, characterized in that... In step (3), the temperature is 0-10℃, the stirring temperature is 25-40℃, the pH of the stirring reaction is 8.0-8.5, the stirring reaction time is 2-8 hours, the pH is adjusted to 3.5-4.5, the standing temperature is 0-10℃, the standing time is 1-6 hours, the vacuum drying temperature is 35-50℃, and the vacuum drying time is 8-16 hours.

10. The application of a water treatment polymer according to any one of claims 1-9 in scale inhibition, characterized in that... A scale inhibitor is prepared using a polymer for water treatment as the active ingredient. The scale inhibitor is used to inhibit the deposition of inorganic salt scale in industrial circulating cooling water systems, reverse osmosis membrane systems, high-salt wastewater treatment systems, boiler feedwater systems, or oilfield water injection systems.

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