A comb copolymer containing phosphonic acid groups and sulfonic acid groups, and a preparation method and application thereof

Abstract

The application provides a comb copolymer containing phosphonic acid groups and sulfonic acid groups and a preparation method and application thereof, and relates to the technical field of admixtures for building materials. The copolymer is a pH adaptive double-side chain comb copolymer obtained through polymerization and amidation reactions in sequence, and the copolymer comprises: a copolymer main chain formed by radical copolymerization of itaconic acid units, 2-acrylamide-2-methylpropanesulfonic acid units, vinylphosphonic acid units and polyethylene glycol monomethyl ether acrylate units; polyethylene glycol monomethyl ether side chains; and amino polycarboxylic acid side chains introduced by modification of itaconic acid units through an amidation reaction. The preparation method comprises: a radical copolymerization reaction, an amidation reaction, a ring-opening condensation reaction and a drying treatment. The application of the copolymer is the application of the copolymer as a gypsum retarder in semi-hydrated gypsum-based materials. The copolymer has the properties of efficient retarding, high strength retention rate, stability in an alkaline environment and insensitivity to dihydrate gypsum in semi-hydrated gypsum-based materials.

Description

Technical Field

[0001] This invention relates to the field of building material admixtures, and in particular to a comb-type copolymer containing phosphonic acid and sulfonic acid groups, its preparation method, and its application. Background Technology

[0002] The hydration of hemihydrate gypsum (CaSO4·0.5H2O) is a typical dissolution-crystallization process, which can be divided into three kinetic stages.

[0003] 1) Dissolution: Hemihydrate gypsum dissolves rapidly upon contact with water; its solubility at 20℃ is approximately 8.5 g / L, releasing Ca into the liquid phase. 2+ and SO4 2- ion.

[0004] 2) Nucleation: Since the solubility of gypsum dihydrate (CaSO4·2H2O) at 20℃ is only about 2.1 g / L, the liquid phase rapidly reaches a supersaturated state for gypsum dihydrate, and gypsum dihydrate crystal nuclei are generated explosively in a very short time. Nucleation is the early hydration rate controlling step.

[0005] 3) Crystal growth and interlocking: Gypsum dihydrate crystals preferentially grow along the c-axis to form needle-like crystals. The crystals interlock and overlap to form a micro-network structure, which is macroscopically manifested as the solidification and hardening of the slurry.

[0006] The essence of gypsum retarder action is to delay or interfere with the nucleation and crystal growth of dihydrate gypsum. Based on the different stages of intervention, the retarding mechanism can be divided into two categories: one is nucleation inhibition-type retarding, which reduces the CaO in the liquid phase. 2+ Concentration delays the time when supersaturation reaches the critical value, thereby slowing down nucleation; another type is crystal growth inhibition type retarding, which adsorbs on the active growth sites on the surface of gypsum dihydrate crystals, blocks ion deposition channels, and slows down the crystal growth rate.

[0007] Currently, gypsum retarders are mainly divided into three categories: organic acid and its salt retarders, modified protein retarders, and alkaline phosphate retarders.

[0008] 1. Organic acids and their salts as retarder, mainly citric acid, tartaric acid, sodium gluconate, etc.

[0009] The main mechanism of action of this type of retarder is the reaction between the carboxyl groups of the molecule and the Ca in the liquid phase. 2+ Formation of chelates reduces free Ca 2+ Concentration delays nucleation; simultaneously, carboxyl groups adsorb onto the surface of gypsum dihydrate crystals, altering crystal morphology. The main drawbacks of this type of retarder are as follows.

[0010] 1) It has a significant impact on strength. While inhibiting crystal growth, organic acid retarders distort the normal needle-like crystals of gypsum dihydrate into short columnar or irregular sheet-like shapes, destroying the interlocking structure between crystals and leading to an increase in the porosity of the hardened body.

[0011] 2) The retarding effect of hemihydrate gypsum is significantly reduced in the presence of alkaline substances. Therefore, silicate cement or lime is often added to gypsum self-leveling mortar and plastering mortar to increase the pH value. In an alkaline environment, Ca... 2+ Concentration due to Ca(OH)2 (KSP=5.5×10) -6 The precipitation significantly decreased, indicating a weakening of the chelation driving force; although the carboxyl group was completely deprotonated to -COO-, Ca... 2+ The decrease in concentration significantly reduces the effective chelation coordination.

[0012] 3) Highly sensitive to dihydrate gypsum. When building gypsum absorbs moisture during storage, it produces a dihydrate gypsum phase (content can reach 1-5%). Construction mixing buckets and tool residues may also introduce dihydrate gypsum. As a pre-existing crystal nucleus, dihydrate gypsum directly skips the nucleation stage, rendering nucleation-inhibiting retarders ineffective.

[0013] 2. Modified protein retarders, mainly consisting of protein hydrolysates and modified protein products.

[0014] The mechanism of action of this type of retarder is the modification of the carboxyl and amino groups on the protein molecular chain or its hydrolysate polypeptide chain, and the interaction of Ca... 2+ Chelation occurs, and modified protein (or polypeptide) macromolecules are adsorbed and coated on the crystal surface, forming a barrier layer. The main drawbacks of this type of retarder are as follows.

[0015] 1) The strength retention rate is moderate but still not ideal. Modified protein retarders have a milder degree of distortion on crystal morphology than organic acids, but it is still not particularly ideal.

[0016] 2) The effectiveness of the modified protein is significantly reduced in an alkaline environment. The protonation ratio of amino groups (-NH2, pKa≈9~10) in the modified protein molecule decreases when the pH is greater than 10, which is conducive to coordination. However, the modified protein macromolecule undergoes conformational changes and partial hydrolysis in an alkaline environment, resulting in damage to its structural integrity.

[0017] 3) Poor batch stability: The raw material sources of some modified protein retarders (animal bone glue, leather waste, etc.) lead to large fluctuations in molecular weight and composition, resulting in significant differences in retardation effect between batches.

[0018] 4) It is prone to rancidity and deterioration under high temperature and humidity, emitting odors and affecting the construction environment.

[0019] 3. Alkaline phosphate retarders, mainly sodium tripolyphosphate and sodium hexametaphosphate.

[0020] The mechanism of action of this type of retarder is the reaction of polyphosphate and Ca. 2+ Formation of a sparingly soluble calcium phosphate coating, reducing the Ca content in the liquid phase. 2+ The concentration is applied to cover the surface of hemihydrate and dihydrate gypsum crystal nuclei. This is the main drawback of this type of retarder.

[0021] 1) The retarding effect is uncontrollable. The retarding curve of phosphate retarder is steep, and flash setting is prone to occur, which causes a sudden and significant reduction in setting time.

[0022] 2) The relationship between dosage and retarding time is nonlinear. Phosphate retarder has almost no retarding effect at low dosages, and the retarding time increases sharply after exceeding the threshold, making it difficult to control precisely in engineering applications.

[0023] 3) It is also sensitive to gypsum dihydrate; phosphates mainly work by lowering the calcium content. 2+ Concentration delays nucleation, and it also fails when encountering pre-existing dihydrate gypsum crystal nuclei.

[0024] In summary, existing gypsum retarder has four major technical defects that have not been solved simultaneously: (1) the contradiction between retarding efficiency and strength retention, with high-efficiency retarding often accompanied by severe strength loss; (2) the retarding efficiency is greatly reduced in alkaline environments, and the setting time is drastically shortened when cement or lime is present; (3) it is sensitive to the content of dihydrate gypsum, and the dihydrate gypsum introduced by moisture absorption during the storage of building gypsum and construction tool residues makes the retarding effect unpredictable; (4) the batch stability and environmental adaptability of retarder products are poor. Therefore, there is an urgent need to provide a gypsum retarder that can simultaneously overcome the defects of existing technologies, such as the contradiction between retarding efficiency and strength retention, the reduction of efficiency in alkaline environments, sensitivity to dihydrate gypsum, and poor batch stability. Summary of the Invention

[0025] To address the shortcomings of existing technologies, such as the contradiction between retarding efficiency and strength retention, performance degradation in alkaline environments, sensitivity to dihydrate gypsum, and poor batch stability, this invention provides a comb-type copolymer containing phosphonic acid and sulfonic acid groups, its preparation method, and its application. When used as a gypsum retarder, this copolymer exhibits excellent properties, including high retarding efficiency, high strength retention, insensitivity to alkaline environments, and insensitivity to dihydrate gypsum.

[0026] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a comb-type copolymer containing phosphonic acid groups and sulfonic acid groups, comprising: the copolymer being a pH-adaptive double-side-chain comb-type copolymer obtained by sequential polymerization and amidation reactions, wherein the molecular structure of the copolymer comprises: The copolymer backbone is formed by free radical copolymerization of itaconic acid (IA) units, 2-acrylamide-2-methylpropanesulfonic acid (AMPS) units, vinylphosphonic acid (VPA) units and polyethylene glycol monomethyl ether acrylate (mPEG-Acrylate) units; The polyethylene glycol monomethyl ether side chain is introduced by the polyethylene glycol monomethyl ether acrylate unit; The aminopolycarboxylic acid side chain is introduced by the itaconic acid unit through an amidation reaction.

[0027] Furthermore, the molecular structure of the copolymer is shown below: Main chain: -[IA]a-[AMPS]b-[VPA]m-[mPEG-Acrylate]x-; Polyethylene glycol monomethyl ether side chain: mPEG segment; Amino polycarboxylic acid side chain: -CO-NH-CH2-CH2-NH-CO-CH2-CH2-COOH; Main chain suspended groups: free -COOH (unmodified IA unit), -SO3H (AMPS unit), -PO3H2 (VPA unit); The comb-shaped copolymer containing phosphonic acid and sulfonic acid groups provided by this invention has a main chain formed by copolymerization of four monomers: itaconic acid, 2-acrylamide-2-methylpropanesulfonic acid, vinylphosphonic acid, and polyethylene glycol monomethyl ether acrylate. It possesses mPEG side chains and amino-polycarboxylic acid side chains introduced through amidation modification. The carboxylic acid, sulfonic acid, and phosphonic acid groups in the copolymer main chain synergistically chelate Ca... 2+ Delaying nucleation, the mPEG side chain provides a spatial shielding function, achieving crystal growth inhibition under low coverage density while maintaining needle-like crystal habit and high strength retention. The aminopolycarboxylic acid side chain provides pH-adaptive chelation function, releasing additional coordination ability through amino deprotonation in alkaline environment to maintain efficient chelation.

[0028] Optionally, the molar ratio of the itaconic acid unit, the 2-acrylamide-2-methylpropanesulfonic acid unit, the vinylphosphonic acid unit, and the polyethylene glycol monomethyl ether acrylate unit is (3~7):(1~4):(0.5~2):(0.8~2.5).

[0029] Furthermore, the molar ratio of the itaconic acid unit, the 2-acrylamide-2-methylpropanesulfonic acid unit, the vinylphosphonic acid unit, and the polyethylene glycol monomethyl ether acrylate unit is 5:2.5:1.2:1.5.

[0030] Optionally, the molar percentage of carboxyl groups participating in the amidation reaction in the itaconic acid unit is 30% to 70%.

[0031] Furthermore, the molar percentage of carboxyl groups participating in the amidation reaction in the itaconic acid unit is 50%.

[0032] Optionally, the number-average molecular weight of the polyethylene glycol monomethyl ether side chain is 800~2000 g / mol.

[0033] Furthermore, the number-average molecular weight of the polyethylene glycol monomethyl ether side chain is 1000 g / mol.

[0034] Furthermore, the length of the polyethylene glycol monomethyl ether side chain is 2~5 nm.

[0035] Optionally, the copolymer has a weight-average molecular weight of 25,000 to 55,000 g / mol.

[0036] In a second aspect, the present invention provides a method for preparing the comb-type copolymer containing phosphonic acid groups and sulfonic acid groups, comprising the following steps: Step 1: Dissolve monomers including itaconic acid (IA), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), vinylphosphonic acid (VPA) and polyethylene glycol monomethyl ether acrylate (mPEG-Acrylate) in deionized water to obtain a monomer solution. Add an initiator and a chain transfer agent to the monomer solution to carry out a free radical copolymerization reaction. After the reaction is completed, cool to room temperature and adjust the pH value to 6-7 to obtain a copolymer intermediate solution. Step 2: Raise the temperature of the copolymer intermediate solution obtained in Step 1 to 80-100°C, add ethylenediamine (EDA) under nitrogen protection, and carry out an amidation reaction for 2-4 hours; then cool to 60-80°C, add succinic anhydride in an equimolar amount of the ethylenediamine, and carry out a ring-opening condensation reaction for 1-3 hours to form an aminopolycarboxylic acid side chain. After the reaction is completed, adjust the pH to 6-7 to obtain the liquid product. Step 3: The liquid product obtained in Step 2 is dried to obtain a powdered product, which is the copolymer.

[0037] In this invention, step two involves amidation modification of the itaconic acid unit in the copolymer intermediate, causing a suspended carboxyl group of the itaconic acid unit to undergo an amidation reaction with ethylenediamine to form a -CO-NH-CH2-CH2-NH2 suspended structure. Subsequently, the free amino group at the end of the suspended structure undergoes a ring-opening condensation reaction with succinic anhydride to form an aminopolycarboxylic acid side chain of -CO-NH-CH2-CH2-NH-CO-CH2-CH2-COOH. The side chain has a length of 0.5~1.0 nm and has a coordination geometry similar to iminodiacetic acid (IDA).

[0038] In the copolymer, the itaconic acid unit, without amidation modification, retains the suspended carboxyl group as free -COOH, which deprotonates to -COO- at pH greater than 4, providing conventional Ca2+. 2+ Chelating ability; the amino polycarboxylic acid side chains formed by amidation modification maintain their chelating ability against Ca in the pH range of 6–13. 2+ Its strong coordination ability means that the lone pair electrons of its amino nitrogen can be fully used for coordination at pH greater than 10, unaffected by deprotonation, thus achieving pH-adaptive chelation.

[0039] Further, in step one, the molar ratio of itaconic acid, 2-acrylamide-2-methylpropanesulfonic acid, vinylphosphonic acid and polyethylene glycol monomethyl ether acrylate is (3~7):(1~4):(0.5~2):(0.8~2.5).

[0040] Optionally, in step one, the amount of the initiator added is 0.5% to 3% of the monomer mass, and the amount of the chain transfer agent is 0.1% to 1% of the monomer mass.

[0041] Further, in step one, the amount of the initiator added is 1.5% of the monomer mass, and the amount of the chain transfer agent is 0.5% of the monomer mass.

[0042] Furthermore, the initiator is ammonium persulfate (APS); the chain transfer agent is mercaptoacetic acid.

[0043] Optionally, in step one, the reaction temperature of the free radical copolymerization reaction is 60~90℃, and the reaction time is 2~6 hours.

[0044] Furthermore, in step one, the reaction temperature of the free radical copolymerization reaction is 75°C, and the reaction time is 4 hours.

[0045] Furthermore, in step one, the mass fraction of the monomer in the monomer solution is 10% to 30%.

[0046] Furthermore, in step one, the monomer solution contains 20% monomer by mass.

[0047] Furthermore, in step one, NaOH is used to adjust the pH value.

[0048] Optionally, in step two, the amount of ethylenediamine added is 30-70% of the molar amount of itaconic acid in step one.

[0049] Furthermore, in step two, the amount of ethylenediamine added is 50% of the molar amount of itaconic acid in step one.

[0050] Furthermore, in step two, the amidation reaction is carried out at a temperature of 90°C for 3 hours.

[0051] Furthermore, in step two, the ring-opening condensation reaction is carried out at a temperature of 70°C for 2 hours.

[0052] Furthermore, in step two, NaOH is used to adjust the pH value.

[0053] Furthermore, in step three, the drying process is either spray drying or vacuum drying.

[0054] Furthermore, in step three, the drying method is spray drying, with an inlet air temperature of 180°C and an outlet air temperature of 80°C.

[0055] Thirdly, the present invention provides the application of the comb-type copolymer containing phosphonic acid groups and sulfonic acid groups as a gypsum retarder in hemihydrate gypsum-based materials.

[0056] Furthermore, the hemihydrate gypsum-based materials include gypsum self-leveling mortar, gypsum putty, jointing gypsum, and gypsum plastering mortar, which are mainly made of α-hemihydrate gypsum or β-hemihydrate gypsum.

[0057] Furthermore, the amount of the gypsum retarder in the hemihydrate gypsum-based material is 0.01% to 0.15% of the gypsum mass.

[0058] Furthermore, the amount of the gypsum retarder in the hemihydrate gypsum-based material is 0.03% to 0.10% of the gypsum mass.

[0059] Furthermore, the amount of the gypsum retarder in the gypsum self-leveling mortar is 0.05% to 0.10% of the gypsum mass.

[0060] Furthermore, the amount of the gypsum retarder in the gypsum plaster mortar is 0.03% to 0.08% of the gypsum mass.

[0061] Furthermore, the hemihydrate gypsum-based material includes hemihydrate gypsum and silicate cement, wherein the amount of silicate cement is 0-10% of the hemihydrate gypsum.

[0062] Furthermore, the hemihydrate gypsum-based material includes hemihydrate gypsum and lime, wherein the amount of lime is 0-5% of the hemihydrate gypsum.

[0063] The beneficial effects of this invention are as follows: 1. The comb-shaped copolymer containing phosphonic acid and sulfonic acid groups provided by the present invention can achieve efficient crystal growth inhibition under low coverage density through the spatial shielding effect of polyethylene glycol monomethyl ether side chains, so that the dihydrate gypsum crystals maintain needle-like growth habit and the 24h compressive strength retention rate is ≥82%, which is far superior to the 55~65% of citric acid retarder and the 75~82% of modified protein retarder.

[0064] 2. The comb-type copolymer containing phosphonic acid and sulfonic acid groups provided by this invention maintains efficient chelation in an alkaline environment with a pH of 11-12 through pH-adaptive coordination of the amino polycarboxylic acid side chains. When containing 5% silicate cement, the setting time attenuation rate is ≤15%, which is far superior to the 40-60% of citric acid and the 3-50% of modified protein, and also superior to the 25-30% attenuation rate of polymer-based retarder HyCon R7200F series products.

[0065] 3. The comb-type copolymer containing phosphonic acid and sulfonic acid groups provided by the present invention has a synergistic inhibition mechanism on the nucleation and growth of gypsum dihydrate and mPEG spatial shielding to resist heterogeneous nucleation interference. When it contains 3% gypsum dihydrate, the retarding efficiency decay rate is ≤10%, which is far superior to 30~50% of citric acid and 20~30% of modified protein.

[0066] 4. The comb-shaped copolymer containing phosphonic acid and sulfonic acid groups provided by the present invention is prepared by controlled free radical copolymerization and quantitative amidation modification. The molecular structure and composition can be precisely controlled, and there is no batch fluctuation problem as with modified protein retarder.

[0067] 5. The comb-type copolymer containing phosphonic acid and sulfonic acid groups provided by this invention, as a retarder, outperforms the Retardan-200P and HyCon R7200F series in terms of comprehensive scores in four dimensions: retarding efficiency, strength retention, alkaline stability, and insensitivity to dihydrate gypsum, achieving a technological breakthrough in the field of gypsum retarder. Detailed Implementation

[0068] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0069] For the terms defined below, unless a different definition is given elsewhere in the claims or this specification, these definitions shall apply. All numerical values, whether explicitly indicated or not, are defined herein as being modified by the term "about." The term "about" generally refers to a range of numerical values ​​that a person skilled in the art would consider equivalent to the stated values ​​to produce substantially the same properties, functions, results, etc. A range of numerical values ​​indicated by a low value and a high value is defined as including all numerical values ​​included within that range and all subranges included within that range.

[0070] Unless otherwise specified, the experimental methods used in the following examples and / or comparative examples are conventional methods; the materials and reagents used can be purchased commercially unless otherwise specified.

[0071] The mass percentages of each component mentioned in the embodiments and / or comparative examples of this invention refer not only to the mass ratio between the components, but also to the specific content of each component. Therefore, any scaling up or down of the content ratios between the components mentioned in the embodiments of this invention is within the scope disclosed in the specification of the embodiments of this invention. The mass units mentioned in the specification can be known mathematical mass units such as mg, g, and kg.

[0072] The comb-type copolymer containing phosphonic acid and sulfonic acid groups provided by this invention, when used as a gypsum retarder, has comprehensive properties such as high efficiency in retarding, high strength retention, stability in alkaline environment and insensitivity to dihydrate gypsum in hemihydrate gypsum-based materials. The retarding mechanism is based on a deep understanding of the three-stage hydration model of hemihydrate gypsum, and targeted intervention is carried out at each stage through different functional units in the molecular structure. 1. Nucleation inhibition: Multi-group synergistic Ca 2+ Chelation

[0073] The early rate-controlling step in the hydration of hemihydrate gypsum is the nucleation stage. The retarder chelates the Ca in the liquid phase. 2+ This reduces the effective supersaturation and delays the time to reach the critical supersaturation, thereby slowing down nucleation. The copolymer backbone of this invention contains three types of chelating groups: carboxylic acid group (-COO-), phosphonic acid group (-PO3-), and others. 2- The aminopolycarboxylic acid side chain (-NH-CO-CH2-CH2-COO-) synergistically chelates Ca with different coordination strengths and pH adaptability. 2+ .

[0074] Under neutral pH conditions (pure gypsum system, pH≈7~8), the carboxylic acid group is completely deprotonated (-COO-, pKa≈3.5~4.5), and the phosphonic acid group undergoes secondary deprotonation (-PO3H- / -PO3). 2- (pKa1≈2~3, pKa2≈7~8), the carboxyl group of the amino polycarboxylic acid side chain is deprotonated, and the amino group participates in coordination as a free -NH2 group. All three groups simultaneously chelate Ca. 2+ The overall chelation efficiency is high. The coordination geometry of a single aminopolycarboxylic acid side chain is IDA-like (nitrogen + two carboxyl oxygen groups form a three-coordinate chelate ring), which, with Ca... 2+ The chelation stability constant is logK≈2.6(IDA-Ca). 2+ In addition, the contributions of the main chain carboxyl and phosphonic acid groups, the copolymer molecule contributes to the Ca... 2+ Its total chelating capacity far exceeds that of citric acid (logK≈3.5) and simple phosphates.

[0075] In an alkaline pH environment (containing cement / lime, pH≈11~12), at pH>12: (a) although the simple carboxylic acid group is completely deprotonated, Ca 2+The concentration of Ca(OH)2 decreased significantly due to precipitation. 2+ (a) The effective concentration decreased from about 30 mmol / L to about 0.5~2 mmol / L, and the coordination driving force of carboxylic acid group chelation weakened; (b) the phosphonate group under alkaline conditions underwent secondary complete deprotonation to -PO3. 2- Increased chelation strength (phosphonic acid group - Ca 2+ logK≈5~6), but also affected by Ca 2+ Low concentration limitations; (c) The key advantage of the aminopolycarboxylic acid side chain is that the lone pair electrons of the amino nitrogen are almost completely free at pH > pKa (approximately 9-10), unaffected by protonation, and the nitrogen and oxygen coordination forms a mixed coordination (N,O-type chelation), which is beneficial in Ca... 2+ It maintains effective coordination even at low concentrations. The apparent chelation stability constant of the aminopolycarboxylic acid side chain in an alkaline environment is about 80-90% of that in a neutral environment, while that of the simple carboxylic acid group is only about 40-50%. Therefore, the retarder of this invention maintains a total chelation efficiency of 85-90% in an alkaline environment through the pH-adaptive coordination of the aminopolycarboxylic acid side chain, thus achieving retarding stability in an alkaline environment. 2. Crystal growth inhibition: Synergistic effect of selective adsorption on crystal planes and spatial shielding

[0076] Gypsum dihydrate crystals belong to the monoclinic crystal system (space group I2 / a), with unit cell parameters a≈5.79 Å, b≈15.21 Å, c≈6.24 Å, β≈116.3°. The crystals have a layered structure: Ca 2+ With SO4 2- Alternating layers form strongly bonded layers, with water molecule layers sandwiched between these layers to form weakly bonded layers. The (010) plane is a natural cleavage plane, splitting along the direction of the water molecule layers. This plane has Ca... 2+ Low exposed density and negative surface charge; while the (111) equal growth surface Ca along the c-axis direction 2+ High exposure density and positive surface charge make it an active growth surface for crystals.

[0077] The crystal growth inhibition mechanism of the retarder of this invention is based on a synergistic model of spatial shielding and targeted adsorption.

[0078] (1) Targeted adsorption, phosphonic acid groups (-PO3) on the copolymer backbone 2- ) for (111) etc. Ca 2+ Growth surfaces with high exposure density exhibit selective adsorption affinity, preferentially occupying active growth sites on these surfaces and blocking Ca2+ adsorption. 2+ and SO4 2- Deposition channels. Phosphonic acid groups and Ca 2+The coordination binding energy is about 20~30 kJ / mol, which is higher than that of the carboxylic acid group, which has a binding energy of about 10~15 kJ / mol, thus ensuring its dominant position in competitive adsorption.

[0079] (2) Spatial shielding: The copolymer molecules adsorbed on the crystal surface have mPEG side chains (2-5 nm in length) extending towards the solution, forming a spatial shielding layer. This shielding layer not only prevents other molecules from approaching the crystal surface, but more importantly, the spatial extension of the mPEG side chains increases the effective coverage area of ​​a single copolymer molecule from approximately 0.5 nm without side chains. 2 Increased to approximately 5~10nm 2 This means that a relatively small number of adsorbed molecules can cover a large area of ​​the crystal surface. This implies that, while achieving the same retarding effect, the retarder of this invention covers only about 1 / 10 to 1 / 20 of the crystal surface density of a retarder without side chains, leaving ample space for crystal growth. This allows the gypsum dihydrate crystals to maintain their needle-like growth habit rather than deforming into short columnar or plate-like shapes. This is the microscopic mechanism by which this invention achieves highly efficient retarding and high strength retention: efficient crystal growth inhibition under low coverage density. 3. Gypsum dihydrate is insensitive: spatial shielding resists heterogeneous nucleation interference.

[0080] The pre-existing dihydrate gypsum phase in building gypsum acts as a heterogeneous nucleation seed, directly bypassing the nucleation stage and rendering retarders that rely solely on nucleation inhibition (such as citric acid and phosphates) ineffective. The mechanism by which the retarder of this invention is insensitive to dihydrate gypsum lies in: (1) The retarder does not rely on a single nucleation inhibition mechanism. Even if the nucleation stage is skipped by heterogeneous seeds, the copolymer molecules can still inhibit the growth rate of existing crystal nuclei through the adsorption mechanism on the crystal surface. This is the core advantage of crystal growth inhibition type retarder.

[0081] (2) The spatial shielding effect of the mPEG side chains further plays a role. After the pre-existing dihydrate gypsum crystal nuclei are covered by copolymer molecules, the spatial extension layer of the mPEG side chains blocks the formation of new Ca2+ crystals. 2+ and SO4 2- The diffusion channels to the surface of the crystal nucleus not only inhibit the growth of the crystal nucleus itself, but also prevent secondary nucleation from occurring near the crystal nucleus.

[0082] (3) The amino polycarboxylic acid side chain also participates in Ca2+ near the surface of the pre-existing crystal nucleus. 2+ Chelation forms a near-surface chelation field, maintaining a locally low Ca2+ level within a range of approximately 0.5–1.0 nm on the crystal nucleus surface (the extension length of the aminopolycarboxylic acid side chain). 2+ Concentration further inhibits crystal growth. 4. pH-adaptive chelation: the coordination chemistry basis in alkaline environments

[0083] The core of this invention's retarder's high efficiency in alkaline environments lies in the pH-adaptive coordination ability of its amino polycarboxylic acid side chains. Its coordination chemistry basis is as follows: (1) Coordination geometry of the aminopolycarboxylic acid side chain. In the side chain structure -CO-NH-CH2-CH2-NH-CO-CH2-CH2-COOH, the terminal -NH and the two -COO- (the two carboxyl groups of the succinic acid moiety) form an IDA-like three-coordination chelate ring (five-membered ring: Ca-NCCO and Ca-OCCO), which interacts with Ca... 2+ A mixed N,O coordination is formed. IDA-Ca 2+ The stability constant logK≈2.6 (25℃, I=0.1), although lower than that of EDTA-Ca 2+ (logK=10.65), but multiple aminopolycarboxylic acid side chains in the copolymer molecule synergistically chelate (each copolymer segment contains an average of 2 to 3 side chains), resulting in a significant overall chelation effect.

[0084] (2) pH-adaptive mechanism. The pKa of amino nitrogen is approximately 9-10 (similar to the pKa of amino NTA, which is approximately 9.7). At pH > pKa, the amino group is deprotonated, and the lone pair electrons of nitrogen are fully available for coordination. The key difference is that the carboxylic acid group is completely deprotonated at pH > 5, and its coordination ability does not change with pH in the range of 5-12; while the amino group exists in the form of -NH3+ (protonated, unable to coordinate) at pH < 9, and in the form of -NH2 (free, able to coordinate) at pH > 10. Therefore, in an alkaline environment with pH > 12, the coordination ability of the amino polycarboxylic acid side chain does not decrease but increases. The amino group changes from the protonated state to the free state, releasing additional coordination ability and compensating for the loss of Ca2+. 2+ The decrease in concentration leads to the loss of chelation driving force.

[0085] (3) Comparative analysis. In an alkaline environment with pH≈12, the simple carboxylic acid group (-COO- of citric acid) affects Ca... 2+ The apparent chelation efficiency is approximately 40-50% at neutral pH (due to Ca). 2+ (Concentration significantly reduced); while the apparent chelation efficiency of the amino polycarboxylic acid side chain of the present invention is approximately 85-90% at neutral pH, and the alkaline activation of the amino coordination ability compensates for the Ca... 2+ The concentration is reduced. Therefore, when the cement content is 5%, the setting time of the retarder of the present invention is reduced by only about 10% to 15%, while that of citric acid is reduced by 40% to 60%, and that of modified protein retarder is reduced by 30% to 50%.

[0086] The present invention will now be described in further detail through specific embodiments and comparative examples.

[0087] It should be noted that the polyethylene glycol monomethyl ether acrylate (mPEG-Acrylate) used in the following examples and comparative examples of the present invention was prepared by esterification reaction of commercial polyethylene glycol monomethyl ether (mPEG, structure CH3O-(CH2CH2O)n-OH) and acrylic acid. Typical preparation conditions were a molar ratio of mPEG to acrylic acid of 1:1.4, using p-toluenesulfonic acid as a catalyst and 4-methoxyphenol as a polymerization inhibitor, reacting for 8 hours under toluene reflux azeotropic conditions with water, and obtaining the product after washing with water, extraction, drying, and vacuum distillation, with an esterification rate ≥96%.

[0088] Therefore, the molecular weight of mPEG-Acrylate is calculated as Mn(mPEG-Acrylate) = Mn(mPEG) + 54 (the net increment of the hydroxyl group -OH replaced by the acryloxy group -O-CO-CH=CH2). For example, the molecular weight of mPEG-Acrylate prepared using mPEG with Mn=800 is Mn=854; the molecular weight of mPEG-Acrylate prepared using mPEG with Mn=1000 is Mn=1054; the molecular weight of mPEG-Acrylate prepared using mPEG with Mn=1500 is Mn=1554; and the molecular weight of mPEG-Acrylate prepared using mPEG with Mn=2000 is Mn=2054. Example 1

[0089] Example 1 provides a comb-type copolymer containing phosphonic acid groups and sulfonic acid groups, the molecular structure of which includes: The copolymer backbone is formed by free radical copolymerization of itaconic acid units, 2-acrylamide-2-methylpropanesulfonic acid units, vinylphosphonic acid units and polyethylene glycol monomethyl ether acrylate units. The polyethylene glycol monomethyl ether side chain is introduced by the polyethylene glycol monomethyl ether acrylate unit; The aminopolycarboxylic acid side chain is introduced by the amidation reaction of itaconic acid unit.

[0090] The copolymer has a molar ratio of itaconic acid units, 2-acrylamide-2-methylpropanesulfonic acid units, vinylphosphonic acid units, and polyethylene glycol monomethyl ether acrylate units in its main chain of 5:2.5:1.2:1.5, and the molar percentage of carboxyl groups participating in the amidation reaction in the itaconic acid units is 50%. The copolymer is prepared using the following method: Step 1: Free radical copolymerization.

[0091] Weigh out 5.00 g (0.0384 mol) of itaconic acid IA, 3.98 g (0.0192 mol) of 2-acrylamide-2-methylpropanesulfonic acid AMPS, 1.00 g (0.0092 mol) of vinylphosphonic acid VPA, and 12.12 g (0.0115 mol) of polyethylene glycol monomethyl ether acrylate mPEG-Acrylate (prepared from mPEG with Mn=1000), and dissolve them in 88 mL of deionized water to obtain a monomer solution with a monomer mass fraction of approximately 20.1%. Add 0.33 g (1.5% of the total monomer mass) of ammonium persulfate and 0.11 g (0.5% of the total monomer mass) of mercaptoacetic acid to the obtained monomer solution. Stir the reaction at 75 °C for 4 hours, cool to room temperature, and adjust the pH to 6.5 with 2 mol / L NaOH solution to obtain a pale yellow transparent copolymer intermediate solution.

[0092] Step 2: Amide reaction and ring-opening condensation.

[0093] The copolymer intermediate solution was heated to 90°C, and 1.16 g of ethylenediamine (0.0192 mol, corresponding to 50% of the molar number of IA units, i.e., 50% of the carboxyl groups participating in the amidation reaction in the itaconic acid unit) was added under nitrogen protection, and the mixture was stirred for 3 hours. The temperature was then lowered to 70°C, and 1.92 g of succinic anhydride (0.0192 mol, equimolar with EDA) was added, and the mixture was stirred for 2 hours. After the reaction was complete, the pH was adjusted to 6.5 with 2 mol / L NaOH solution to obtain the liquid product.

[0094] Step 3: Drying process.

[0095] The liquid product was spray-dried at an inlet air temperature of 180°C and an outlet air temperature of 80°C to obtain a white powder product, labeled as P-1.

[0096] According to GPC measurements, the weight-average molecular weight (Mw) of P-1 is approximately 35,000 g / mol (polyethylene glycol standard), and the molecular weight distribution index (PDI) is approximately 2.1. Example 2

[0097] Example 2 provides a comb copolymer containing phosphonic acid and sulfonic acid groups. The difference between Example 2 and Example 1 is that the amounts of the four monomer reaction raw materials in step one are different. Specifically, itaconic acid IA 5.00g (0.0384mol), 2-acrylamide-2-methylpropanesulfonic acid AMPS 10.61g (0.0512mol), vinylphosphonic acid VPA 0.69g (0.0064mol), and polyethylene glycol monomethyl ether acrylate mPEG-Acrylate (prepared from mPEG with Mn=1000) 10.75g (0.0102mol) in a molar ratio of 3:4:0.5:0.8. The amounts of the remaining raw materials and the preparation method are the same as in Example 1. The resulting sample is P-2 with a weight-average molecular weight Mw of approximately 27000g / mol. Example 3

[0098] Example 3 provides a comb copolymer containing phosphonic acid and sulfonic acid groups. The difference between Example 3 and Example 1 is that the amounts of the four monomer reaction raw materials in step one are different. Specifically, itaconic acid IA 5.00g (0.0384mol), 2-acrylamide-2-methylpropanesulfonic acid AMPS 1.14g (0.0055mol), vinylphosphonic acid VPA 1.19g (0.0110mol), and polyethylene glycol monomethyl ether acrylate mPEG-Acrylate (prepared from mPEG with Mn=1000) 14.44g (0.0137mol) in a molar ratio of 7:1:2:2.5. The amounts of the remaining raw materials and the preparation method are the same as in Example 1. The resulting sample is P-3, with a weight-average molecular weight Mw of approximately 34000g / mol. Example 4

[0099] Example 4 provides a comb-type copolymer containing phosphonic acid and sulfonic acid groups. The difference between Example 4 and Example 1 is that in step 2, the amount of ethylenediamine added is 0.69g (0.0115mol, corresponding to 30% of the molar number of IA units, i.e., the molar percentage of carboxyl groups participating in the amidation reaction in the itaconic acid unit is 30%), and 1.15g (0.0115mol, equimolar with EDA) of succinic anhydride is added. The amount of other raw materials and the preparation method are the same as in Example 1. The resulting sample is P-4, with a weight-average molecular weight Mw of approximately 35000g / mol. Example 5

[0100] Example 5 provides a comb-type copolymer containing phosphonic acid and sulfonic acid groups. The difference between Example 5 and Example 1 is that in step 2, the amount of ethylenediamine added is 1.61g (0.0269mol, corresponding to 70% of the molar number of IA units, i.e., the molar percentage of carboxyl groups participating in the amidation reaction in the itaconic acid unit is 70%), and 2.69g (0.0269mol, equimolar with EDA) of succinic anhydride is added. The amount of other raw materials and the preparation method are the same as in Example 1. The resulting sample is P-5, with a weight-average molecular weight Mw of approximately 35000g / mol. Example 6

[0101] Example 6 provides a comb-type copolymer containing phosphonic acid and sulfonic acid groups. The difference between Example 6 and Example 1 lies in the source and amount of polyethylene glycol monomethyl ether acrylate (mPEG-Acrylate) in step one. Specifically, the mPEG-Acrylate is prepared from mPEG with Mn=800, and its added mass is 9.82 g (0.0115 mol). The total monomer mass is 19.80 g, dissolved in 59 ml of deionized water, with a monomer mass fraction of approximately 25% in the monomer solution. The initiator is ammonium persulfate (0.30 g), and the chain transfer agent is mercaptopropionic acid (0.10 g). The amounts of other raw materials and the preparation method are the same as in Example 1. The resulting sample is P-6, with a weight-average molecular weight (Mw) of approximately 25000 g / mol. Example 7

[0102] Example 7 provides a comb-type copolymer containing phosphonic acid and sulfonic acid groups. The difference between Example 7 and Example 1 lies in the source and amount of polyethylene glycol monomethyl ether acrylate (mPEG-Acrylate) in step one. Specifically, the mPEG-Acrylate is prepared from mPEG with Mn=1500, and its added mass is 17.87 g (0.0115 mol). The total monomer mass is 27.85 g, dissolved in 111 ml of deionized water. The monomer mass fraction in the monomer solution is approximately 20.1%. The initiator is ammonium persulfate (0.42 g), and the chain transfer agent is mercaptopropionic acid (0.14 g). The amounts of other raw materials and the preparation method are the same as in Example 1. The resulting sample is P-7, with a weight-average molecular weight (Mw) of approximately 35000 g / mol. Example 8

[0103] Example 8 provides a comb-type copolymer containing phosphonic acid and sulfonic acid groups. The difference between Example 8 and Example 1 lies in the source and amount of polyethylene glycol monomethyl ether acrylate (mPEG-Acrylate) in step one. Specifically, the mPEG-Acrylate is prepared from Mn2000 mPEG, with an added mass of 23.62 g (0.0115 mol). The total monomer mass is 33.60 g, dissolved in 134 ml of deionized water, with a monomer mass fraction of approximately 20.1% in the monomer solution. The initiator is ammonium persulfate (0.50 g), and the chain transfer agent is mercaptopropionic acid (0.17 g). The amounts of other raw materials and the preparation method are the same as in Example 1. The resulting sample is P-8, with a weight-average molecular weight (Mw) of approximately 50,000 g / mol.

[0104] Table 1. Raw material selection and weight-average molecular weight of the products obtained in Examples 1-8 Comparative Example 1

[0105] This comparative example provides a comb-type copolymer containing phosphonic acid and sulfonic acid groups. The difference between this and Example 1 is that step two is missing. That is, the copolymer intermediate is not modified by amidation reaction and is directly subjected to the drying treatment in step three. The resulting sample is Q-1.

[0106] In the following application examples, the setting time was determined according to GB / T17669.4-1999, and the 24h compressive strength was determined according to GB / T17669.3-1999. Application Example 1

[0107] The samples obtained in Examples 1-8 and Comparative Example 1 (P-1~8 / Q-1), and citric acid were used as retarders to test the retarding performance of β-hemihydrate gypsum with a dihydrate gypsum phase content of less than 0.5%. The water-to-gypsum ratio was 0.60, the retarder dosage was 0.05% of the gypsum mass, and the test temperature was 20℃. The test results are shown in Table 2.

[0108] Table 2 Test results of Application Example 1

[0109] A comparison of P-1, P-4, P-5, and Q-1 shows that amidation significantly improves the retarding effect and strength retention. The best overall performance is achieved with an fA of 50%, with an initial setting time of 78 min, meeting the 60-120 min range required for self-leveling applications, and a 24-hour strength retention of 91.7%. With fA=70%, the retarding time is further extended, but the strength retention decreases slightly. This is because the excessive amino-polycarboxylic acid side chains increase the chelation strength, leading to more significant inhibition of crystal growth. The unmodified copolymer intermediate (fA=0%) has an initial setting time of 45 min, exhibiting some retarding effect, but its strength retention is only 84.3%.

[0110] The comparison of P-1, P-2, and P-3 shows that P-2 (high AMPS, low VPA) has a shorter retardation time, and although the sulfonic acid groups are alkali-resistant, their chelation strength is limited; P-3 (high IA, high VPA, low AMPS) has a longer retardation time but a lower strength retention rate (too many chelating groups lead to excessive inhibition of crystal growth); P-1 (5:2.5:1.2:1.5) is the optimal balance.

[0111] A comparison of P-1, P-6, P-7, and P-8 shows that mPEG Mn = 1000 g / mol (side chain length approximately 2.5 nm) is the optimal value. Too short a side chain (800 g / mol, approximately 2 nm) results in insufficient steric shielding, leading to a higher crystal surface coverage density and decreased strength retention. Too long a side chain (2000 g / mol, approximately 5 nm) results in an excessively strong shielding effect, reducing the contact efficiency between the chelating groups and the crystal surface, thus decreasing both retarding efficiency and strength retention. Mn = 1000~1500 g / mol is the optimal range.

[0112] The comparison between P-1 and citric acid shows that although citric acid has a longer retardation time, its strength retention rate is only 59.3%. P-1 has a moderate retardation time and a strength retention rate of 91.7%. This demonstrates the advantage of efficient inhibition with low coverage density. P-1's mPEG side chains allow it to achieve effective retardation by covering the crystal surface with a lower density, while the crystal still has sufficient growth space to maintain its needle-like morphology. Application Example 2

[0113] Sample P-1 obtained in Example 1 was used as a retarder, and its retarding performance was tested in β-hemihydrate gypsum with a dihydrate gypsum phase content of less than 0.5% at different dosages. The water-to-gypsum ratio was 0.60, and the test temperature was 20℃. The test results are shown in Table 3.

[0114] Table 3 Test results of Application Example 2

[0115] As shown in Table 3, within the dosage range of 0.03% to 0.10%, the initial setting time is 42 to 165 minutes, and the final setting time is 72 to 285 minutes, which can meet the needs of different construction scenarios. The optimal working range is 0.05% to 0.08%, with a strength retention rate of 88.9% to 91.7%. Application Example 3

[0116] β-hemihydrate gypsum with a dihydrate gypsum phase content of less than 0.5% was mixed with 5% P·O 42.5 silicate cement and 3% lime by mass. The setting time changes of three types of retarders—P-1, citric acid, and modified protein—were tested. The water-to-gypsum ratio was 0.60, the retarder dosage was 0.05% of the gypsum mass, and the test temperature was 20℃. The test results are shown in Table 4.

[0117] Table 4 Test results of Application Example 3

[0118] As shown in Table 4, sample P-1 exhibited an initial setting time reduction of only 12.8% with 5% cement and 13.5% with 3% lime, significantly better than citric acid and modified proteins. This verifies the pH-adaptive coordination mechanism of the amino polycarboxylic acid side chain, where deprotonation of the amino group in an alkaline environment releases additional coordination capacity, compensating for the reduced Ca2+ content. 2+ The effect of reduced concentration. Application Example 4

[0119] 3% and 5% of analytically pure dihydrate gypsum (DH phase) were artificially added to β-hemihydrate gypsum with a dihydrate gypsum phase content of less than 0.5%, and the setting time changes of different retarders were tested. The water-to-gypsum ratio was 0.60, the retarder dosage was 0.05% of the gypsum mass, and the test temperature was 20℃. The test results are shown in Table 5.

[0120] Table 5 Test results of Application Example 4

[0121] As shown in Table 5, sample P-1 is highly insensitive to the content of gypsum dihydrate. When containing 3% gypsum dihydrate, the initial setting rate only decreased by 7.7%, which is far superior to 50% citric acid and 23.1% modified protein, and 15.4% decrease when containing 5% gypsum dihydrate. This verifies the effectiveness of the crystal growth inhibition + mPEG spatial shielding mechanism against heterogeneous nucleation interference. Application Example 5

[0122] P-1 was compared with the modified protein-based retarder Retardan-200P and the polymer-based retarder HyCon R 7200F under the same conditions. The recommended optimal dosages were used for each (P-1: 0.05%; Retardan-200P: 0.08%; HyCon R 7200F: 0.06%), with a water-to-solid ratio of 0.60. The test results are shown in Table 6.

[0123] Table 6 Test results of Application Example 5

[0124] Note: In Application Examples 3 and 4, a uniform dosage of 0.05% was used for variable control and comparison; in Application Example 5, each retarder was used with its own recommended optimal dosage, so the decay rate data differed from Application Examples 3 and 4, but the trend was completely consistent.

[0125] As can be seen from the results in Table 6, P-1 is superior to international benchmark products in four dimensions: retarding efficiency, strength retention rate, alkaline stability, and insensitivity to dihydrate gypsum. Application Example 6: Application of Gypsum Self-Leveling Mortar

[0126] Gypsum self-leveling mortar formula: 60% β-hemihydrate gypsum, 35% quartz sand, 5% silicate cement, 0.08% P-1 retarder (by weight of gypsum), 0.5% redispersible latex powder, 0.1% water-reducing agent, and 0.05% defoamer. Water-to-gypsum ratio: 0.5. Test temperature: 20℃.

[0127] Table 7 Test results of Application Example 6

[0128] As shown in Table 7, P-1 in gypsum self-leveling mortar containing 5% cement achieved an initial setting time of 65 minutes, meeting construction requirements, and a 30-minute fluidity retention rate of 93%, significantly better than citric acid (76%) and Retardan-200P (85%). It also exhibited the highest strength at both 24 hours and 28 days. Citric acid, however, showed a severe reduction in retarding effectiveness in cement-containing systems, with an initial setting time of only 25 minutes, which no longer met construction requirements. Notably, even with the citric acid dosage increased to 0.08% (higher than its conventional dosage of 0.02%~0.05% in pure gypsum systems), it still almost completely lost its retarding effect in systems containing 5% cement, further validating the inherent defect of organic acid retarders exhibiting severe performance degradation in alkaline environments. Application Example 7: Application of Plaster Plaster Mortar

[0129] Plaster plaster mortar formula: 85% β-hemihydrate gypsum, 3% lime, 12% lightweight aggregate, 0.06% P-1 retarder (by weight of gypsum), 0.2% cellulose ether, and 0.03% defoamer. Water-to-gypsum ratio: 0.55. Test temperature: 20℃.

[0130] Table 8 Test results of Application Example 7

[0131] As can be seen from the results in Table 8, in gypsum plastering mortar containing 3% lime, P-1 has an initial setting time of 75 min, which meets the construction requirements of 60~90 min for manual plastering. Its 24h compressive strength is 6.8 MPa, which is far superior to citric acid 3.5 MPa and Retardan-200P 5.5 MPa. Its bond strength is 0.45 MPa, which meets the requirement of GB / T 28627-2023 that the bond strength is not less than 0.3 MPa.

[0132] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A comb-type copolymer containing phosphonic acid groups and sulfonic acid groups, characterized in that, include: The copolymer is a pH-adaptive double-sided comb copolymer obtained by sequential polymerization and amidation reactions, and the molecular structure of the copolymer includes: The copolymer backbone is formed by free radical copolymerization of itaconic acid units, 2-acrylamide-2-methylpropanesulfonic acid units, vinylphosphonic acid units and polyethylene glycol monomethyl ether acrylate units. The polyethylene glycol monomethyl ether side chain is introduced by the polyethylene glycol monomethyl ether acrylate unit; The aminopolycarboxylic acid side chain is introduced by the itaconic acid unit through an amidation reaction.

2. The comb-type copolymer containing phosphonic acid groups and sulfonic acid groups according to claim 1, characterized in that, The molar ratio of the itaconic acid unit, the 2-acrylamide-2-methylpropanesulfonic acid unit, the vinylphosphonic acid unit, and the polyethylene glycol monomethyl ether acrylate unit is (3~7):(1~4):(0.5~2):(0.8~2.5).

3. The comb-type copolymer containing phosphonic acid groups and sulfonic acid groups according to claim 1, characterized in that, The molar percentage of carboxyl groups participating in the amidation reaction in the itaconic acid unit is 30% to 70%.

4. The comb-type copolymer containing phosphonic acid groups and sulfonic acid groups according to claim 1, characterized in that, The number-average molecular weight of the polyethylene glycol monomethyl ether side chain is 800~2000 g / mol.

5. The comb-type copolymer containing phosphonic acid groups and sulfonic acid groups according to claim 1, characterized in that, The copolymer has a weight-average molecular weight of 25,000 to 55,000 g / mol.

6. The method for preparing the comb-type copolymer containing phosphonic acid groups and sulfonic acid groups according to any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Dissolve monomers including itaconic acid, 2-acrylamide-2-methylpropanesulfonic acid, vinylphosphonic acid and polyethylene glycol monomethyl ether acrylate in deionized water to obtain a monomer solution. Add an initiator and a chain transfer agent to the monomer solution to carry out a free radical copolymerization reaction. After the reaction is complete, cool to room temperature and adjust the pH value to 6-7 to obtain a copolymer intermediate solution. Step 2: Raise the temperature of the copolymer intermediate solution obtained in Step 1 to 80-100°C, add ethylenediamine under nitrogen protection, and carry out an amidation reaction for 2-4 hours; then cool to 60-80°C, add succinic anhydride in an equimolar amount of the ethylenediamine, and carry out a ring-opening condensation reaction for 1-3 hours to form an aminopolycarboxylic acid side chain; after the reaction is completed, adjust the pH to 6-7 to obtain the liquid product. Step 3: The liquid product obtained in Step 2 is dried to obtain a powdered product, which is the copolymer.

7. The method for preparing the comb-type copolymer containing phosphonic acid groups and sulfonic acid groups according to claim 6, characterized in that, In step one, the amount of the initiator added is 0.5% to 3% of the monomer mass, and the amount of the chain transfer agent is 0.1% to 1% of the monomer mass.

8. The method for preparing the comb-type copolymer containing phosphonic acid groups and sulfonic acid groups according to claim 6, characterized in that, In step one, the reaction temperature of the free radical copolymerization reaction is 60~90℃, and the reaction time is 2~6 hours.

9. The method for preparing the comb-type copolymer containing phosphonic acid groups and sulfonic acid groups according to claim 6, characterized in that, In step two, the amount of ethylenediamine added is 30-70% of the molar amount of itaconic acid in step one.

10. The use of the comb-type copolymer containing phosphonic acid groups and sulfonic acid groups as described in any one of claims 1-5 as a gypsum retarder in hemihydrate gypsum-based materials.

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