Sugar-phosphonic acid covalently bonded super-retarder and preparation method thereof

Abstract

This invention discloses a sugar-phosphonic acid covalently bonded super-retarder and its preparation method, comprising the following steps: Step S1, dissolving a sugar component in water to obtain a sugar solution, and adjusting the pH of the sugar solution to be greater than 7; Step S2, providing a bridging agent, wherein both ends of the bridging agent contain epoxy groups, dissolving the bridging agent in an organic solvent to obtain an organic phase solution, adding the organic phase solution to the sugar solution, wherein the hydroxyl groups of the sugar molecules in the sugar solution undergo a ring-opening reaction with the epoxy groups at one end of the bridging agent to obtain an intermediate solution containing epoxy groups; Step S3, adding aminotrimethylenephosphonic acid to the intermediate solution, wherein the epoxy groups in the intermediate solution undergo a ring-opening reaction with the amino groups in the aminotrimethylenephosphonic acid to obtain the sugar-phosphonic acid covalently bonded super-retarder. The sugar-phosphonic acid covalently bonded super-retarder of this invention has a better ultra-long retardation effect and better late-stage performance.

Description

Technical Field

[0001] This invention relates to the interdisciplinary field of building material admixtures and organic synthetic chemistry, specifically to a sugar-phosphonic acid covalently bonded super retarder and its preparation method. Background Technology

[0002] Super-retarders for concrete are admixtures used to significantly extend the setting time of cement-based materials, and they have important applications in engineering scenarios such as construction during high-temperature seasons, large-volume concrete pouring, and long-distance pumping. Currently, the technical route to achieve the super-long retarding effect mainly relies on the simple physical compounding of sugar substances (such as sucrose and sodium gluconate) and phosphonic acid substances (such as aminotrimethylene phosphonic acid and hydroxyethylidene diphosphonic acid).

[0003] While existing super retarders can extend setting time to some extent, they are essentially multi-component physical mixtures. In these systems, each functional component is independent and easily affected by variations in mixing uniformity, component ratios, and construction environment. This results in insufficient stability and reproducibility of the retarding effect. When the ratio is not properly controlled, the retarding effect may fluctuate significantly, affecting the reliability of engineering applications. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing concrete super-retarders and provide a method that can stably combine sugar-based retarder components and phosphonic acid-based retarder components at the molecular structure level, thereby fundamentally solving the problems of poor stability and ratio sensitivity of physical compound systems.

[0005] To achieve the above objectives, the present invention provides a method for preparing a sugar-phosphonic acid covalently bonded superretarder, comprising the following steps: Step S1: Dissolve the carbohydrate components in water to obtain a carbohydrate solution, and adjust the pH of the carbohydrate solution to be greater than 7; Step S2: A bridging agent is provided, wherein both ends of the bridging agent contain epoxy groups. The bridging agent is dissolved in an organic solvent to obtain an organic phase solution. The organic phase solution is added to the sugar solution. The hydroxyl groups of the sugar molecules in the sugar solution undergo a ring-opening reaction with the epoxy groups at one end of the bridging agent to obtain an intermediate solution containing epoxy groups. Step S3: Add aminotrimethylenephosphonic acid to the intermediate solution, and the remaining epoxy groups in the intermediate solution undergo a ring-opening reaction with the amino group in the aminotrimethylenephosphonic acid to obtain the sugar-phosphonic acid covalently bonded super retarder.

[0006] Preferably, the sugar component is selected from at least one of sucrose, glucose, fructose, maltose, and lactose.

[0007] Preferably, the bridging agent is 1,2,7,8-diepoxyoctane.

[0008] Preferably, the molar ratio of the carbohydrate component to the bridging agent to aminotrimethylenephosphonic acid is 1:(0.8~1.2):(0.8~1.2).

[0009] Preferably, the pH of the sugar solution is 9-11.

[0010] Preferably, the reaction temperature in step S2 is 40℃~65℃, and the reaction time is 3h~6h.

[0011] Preferably, the reaction temperature of S3 is 50℃~70℃, and the reaction time is 4h~9h.

[0012] Preferably, in steps S2 and S3, the infrared spectrum at 910 cm⁻¹ is monitored. -1 The intensity of the characteristic peak of the epoxy group at the reaction site is used to control the reaction process.

[0013] The present invention also provides a sugar-phosphonic acid covalently bonded super-retarder prepared by any one of the preparation methods described above, wherein the sugar-phosphonic acid covalently bonded super-retarder is composed of a sugar component, a bridging agent, and aminotrimethylenephosphonic acid linked by covalent bonds, and both ends of the bridging agent contain epoxy groups.

[0014] Preferably, the bridging agent is 1,2,7,8-diepoxyoctane.

[0015] Compared to the prior art, the beneficial effects of the present invention include at least the following: (1) The present invention proceeds in two steps. In the first step, sucrose reacts with the epoxy group at one end of the bridging agent to undergo a ring-opening reaction. In the second step, aminotrimethylenephosphonic acid reacts with the epoxy group at the other end of the bridging agent to undergo a ring-opening reaction. Unlike the process of directly mixing the three raw materials, the present invention effectively utilizes the characteristic that the nucleophilicity of the lone pair electrons of the central nitrogen atom in aminotrimethylenephosphonic acid is higher than that of the hydroxyl group in sucrose. The stepwise reaction allows sucrose to react preferentially with the bridging agent, and efficiently prepares a sugar-phosphonic acid covalently bonded super retarder, which contains the target molecular structure of "sugar end - bridging segment - phosphonic acid end". The hydroxyl groups at the sugar end first adsorb onto the surface of cement particles, forming a physical barrier layer. This barrier layer serves two purposes: first, it hinders the contact between water molecules and cement minerals, delaying the formation of hydration products and significantly extending the time for the cement paste to change from a fluid state to a solid state; second, it slows down the rapid release of calcium ions from the surface of cement particles into the solution. After the sugar end adsorbs at a local location on the cement particles, the phosphonic acid end is also anchored near the adsorption site of the sugar end. First, multiple phosphonic acid groups can undergo strong complexation with calcium ions in the system, delaying the rapid formation of hydration products and achieving efficient and stable ultra-long retardation; second, the phosphonic acid groups only "intercept" a small amount of calcium ions released in the early stage, while a large number of calcium ions remain. After the ultra-long retardation period ends, these calcium ions can be used for subsequent hydration reactions to continue generating hydration products, thereby maintaining the mechanical properties of cement-based materials. The sugar end and the phosphonic acid end are connected within the same molecule, so that the two effects of "adsorption retardation" and "complexation inhibition" occur simultaneously at the same site, achieving a stronger intramolecular synergistic effect than physical mixing. This achieves ultra-long retardation while maintaining or even improving the mechanical properties of the material.

[0016] (2) In this invention, a sugar component (sucrose) and a phosphonic acid component (aminotrimethylenephosphonic acid) are covalently linked through a biepoxide bridging agent (1,2,7,8-diepoxideoctane) to form a super-retarder with a single molecular structure. Unlike the prior art where the two components are simply physically mixed, this invention fixes the ratio of the two functional groups at the molecular structure level, avoiding the fluctuations in retardation effect caused by component separation, asynchronous diffusion, or imbalance in proportion due to simple physical mixing, and significantly improving the stability and reproducibility of the super-retarder effect. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the preparation route of the sugar-phosphonic acid covalently bonded superretarder of the present invention.

[0018] Figure 2 This is a comparison chart of the initial setting time for different experimental schemes.

[0019] Figure 3 This is a comparison chart of the mechanical properties of the examples and the comparative examples. Detailed Implementation

[0020] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] Currently, research on super-retarders for concrete and other cement-based materials mainly focuses on physical blending of carbohydrates and phosphonic acids, phosphonic acid super-retarder composite systems, and the preparation of novel super-retarding components through chemical reactions. However, the overall approach remains dominated by multi-component physical blending systems or other types of chemical reaction systems. This invention breaks through the traditional blending approach by designing a covalent structure at the molecular level. Focusing on the synergistic retarding effect of carbohydrate and phosphonic acid components, the carbohydrate component and aminotrimethylene phosphonic acid are bridged through a double epoxy compound and constructed via a stepwise ring-opening reaction to obtain a sugar-phosphonic acid covalently bonded single-molecule super-retarder. This ensures that the two functional groups coexist stably in the same molecular structure, thereby reducing performance fluctuations caused by component separation and mismatch in traditional blending systems. The sugar-phosphonic acid covalently bonded super-retarder prepared by this invention is more stable, significantly extending the setting time of cement-based materials at lower dosages, improving the stability and controllability of the super-retarding effect, and achieving a long-term retarding effect without a significant decrease in the later mechanical properties of the material.

[0022] This invention preferably uses sucrose as the sugar functional component, aminotrimethylenephosphonic acid as the phosphonic acid functional component, and 1,2,7,8-diepoxyoctane as a molecular bridging agent. A stepwise ring-opening reaction method is employed to prepare a sugar-phosphonic acid covalently bonded superretarder. The design route is as follows: first, the epoxy group at one end of the bridging agent undergoes a ring-opening reaction with the hydroxyl group in the sucrose molecule to form an intermediate with a remaining epoxy group; then, the epoxy group retained on this intermediate undergoes a further ring-opening reaction with the amino group in aminotrimethylenephosphonic acid, thereby stably linking the sucrose component and the aminotrimethylenephosphonic acid component in the same molecular structure to obtain the target product. It should be noted that the sugar components of the present invention are selected from at least one of sucrose, glucose, fructose, maltose, and lactose. These sugar components all contain free hydroxyl groups, are water-soluble, and have sufficient chemical stability in alkaline aqueous solutions with pH 9 to 11. Therefore, at the reaction mechanism level, the above-mentioned sugar components can all undergo ring-opening reactions with bridging agents to generate intermediates containing residual epoxy groups.

[0023] The sucrose molecules used in this invention contain multiple hydroxyl groups, enabling them to adhere to the surface of cement particles through adsorption in cement-based material systems, thus retarding the early hydration process. The aminotrimethylenephosphonic acid molecules contain multiple phosphonic acid groups and amino groups, with the phosphonic acid groups capable of strong complexation with calcium ions in the system, thereby inhibiting the formation and growth of hydration products. By linking these two functional components, sucrose and aminotrimethylenephosphonic acid, within the same molecule, they no longer exist independently but work together in the same molecular structure to enhance the stability and sustainability of the retarding effect in the cement hydration process.

[0024] The bridging agent of this invention is preferably 1,2,7,8-diepoxyoctane (DEO). This substance has epoxy groups at both ends of its molecule, enabling it to undergo ring-opening reactions with hydroxyl and amino groups, respectively. Simultaneously, its intermediate chain segment possesses a certain degree of flexibility, facilitating the effect of the resulting product on the surface of cement particles. Compared to directly physically mixing carbohydrate and phosphonic acid components, this invention achieves covalent bonding between the two through a bridging agent, fixing the ratio between functional groups at the molecular level and reducing the impact of component separation and mismatch.

[0025] This invention employs a step-by-step reaction method primarily because the central nitrogen atom (tertiary amine) in aminotrimethylenephosphonic acid is more reactive to the epoxy group than the hydroxyl group in the sucrose molecule. If all three are mixed simultaneously, the bridging agent may preferentially react with aminotrimethylenephosphonic acid, making it difficult to obtain the desired bridging structure. Therefore, this invention first reacts sucrose with the bridging agent to form a sucrose-bridging agent intermediate, and then adds aminotrimethylenephosphonic acid for the second step of the reaction, thereby ensuring the successful formation of the target structure.

[0026] like Figure 1 As shown, this invention provides a method for preparing a sugar-phosphonic acid covalently bonded superretarder, comprising the following steps: Step S1: Dissolve the sugar components in water to obtain a sugar solution, and add an alkaline regulator to adjust the pH of the sugar solution to be greater than 7.

[0027] In some embodiments, the pH of the carbohydrate solution is adjusted to 9-11. The purpose of adjusting the pH of the carbohydrate solution in step S1 is to provide the necessary alkaline catalytic environment for step S2. The mechanism is as follows: under alkaline conditions, the hydroxyl groups (R-OH) of the carbohydrate molecules react with the OH groups in the system. - Deprotonation equilibrium occurs, and some hydroxyl groups are converted into alkoxides (RO). - The alkoxide exists; its nucleophilicity is significantly higher than that of the neutral hydroxyl group, enabling it to effectively attack the epoxy three-membered ring of the bridging agent, undergoing a nucleophilic ring-opening reaction to form an ether bond (COC). The alkoxide anion generated during the reaction is protonated by water molecules to regenerate OH groups. -This allows the alkaline catalyst to participate in the reaction in a cyclical manner. Therefore, the amount of alkaline regulator (such as NaOH) used in this invention is a catalytic amount and does not need to reach a stoichiometric ratio. If the pH is too low (close to neutral), the hydroxyl groups of the sugars are difficult to deprotonate, the alkoxide concentration is too low, and the ring-opening reaction rate in step S2 is extremely slow, making it difficult to complete the reaction within a reasonable time. If the pH is too high (greater than 11), the epoxy groups of the bridging agent may react with excess OH groups in the system. - Direct hydrolysis occurs as a side reaction, generating vicinal diols, which reduces the number of epoxy groups retained on the intermediate, affecting the bonding reaction with aminotrimethylenephosphonic acid in step S3. Therefore, this invention preferably uses pH 9-11 to ensure the ring-opening reaction proceeds fully while suppressing the hydrolysis side reaction of epoxy groups.

[0028] Step S2 involves providing a bridging agent containing epoxy groups at both ends. The bridging agent is dissolved in an organic solvent to obtain an organic phase solution. This organic phase solution is then slowly added to the sugar solution under stirring, causing the hydroxyl groups of the sugar molecules in the sugar solution to undergo a ring-opening reaction with the epoxy groups at one end of the bridging agent (reaction formula shown in Formula I). ​​By controlling the reaction temperature, reaction time, and reactant ratio, the sugar molecules are primarily connected to the bridging agent at single points, avoiding cross-linking and gelation caused by the simultaneous reaction of multiple hydroxyl groups. After the reaction in Step S2 is completed, the organic solvent is removed, yielding an intermediate solution containing the remaining epoxy groups.

[0029] During step S2, Fourier transform infrared spectroscopy can be used to monitor the reaction at 910 cm⁻¹. -1 The change in the characteristic peak of the epoxy group was observed. When the peak intensity dropped to 45%–55% of the initial value, the reaction in step S2 was terminated, and the organic solvent was removed to obtain a sucrose-DEO intermediate solution.

[0030] It should be noted that the peak intensity termination threshold of 45%~55% is set precisely to ensure that one of the two epoxy groups on each DEO molecule is "consumed on average," achieving a single-end reaction (single-point access), allowing the intermediate to retain the other epoxy group for bonding with ATMP in step S3. Since DEO is a bifunctional symmetrical molecule, the total amount of epoxy groups before the reaction corresponds to 100% peak intensity. If both ends react completely, the peak intensity drops to 0%. Therefore, 50% peak intensity corresponds to the ideal state of "one end reacting, one end remaining," and the ±5% tolerance range is used to accommodate statistical distribution and measurement errors in actual reactions. This control is the core process parameter for achieving the target molecular structure of "sugar end—bridging segment—phosphonic acid end" in this invention.

[0031] In some embodiments, the bridging agent is 1,2,7,8-diepoxyoctane, with the molecular formula C8H. 14 O2.

[0032] In some embodiments, the organic solvent is acetone.

[0033] In some embodiments, the reaction temperature in step S2 is 40°C to 65°C, and the reaction time is 3h to 6h.

[0034] Sucrose–OH + DEO → Sucrose–O–CH2–CH(OH)–(CH2)4–CH(O)–CH2 Formula I In this context, Sucrose–OH represents the active hydroxyl group in the sucrose molecule, DEO represents 1,2,7,8-diepoxyoctane, and Sucrose–O–CH2–CH(OH)–(CH2)4–CH(O)–CH2 represents the sucrose-DEO intermediate obtained from the reaction. In this intermediate, one end of the epoxy group has undergone ring-opening to form an ether bond, while the other end of the epoxy group is retained for subsequent reaction with aminotrimethylenephosphonic acid.

[0035] Sucrose molecules contain multiple hydroxyl groups. If the amount of bridging agent is too large or the reaction is excessive, the multiple hydroxyl groups in the sucrose molecules may react with different bridging agent molecules, further initiating cross-linking, leading to excessively high product viscosity or even gelation, which is detrimental to its use as an additive in cement-based materials. Therefore, the ratio of bridging agent to sucrose in step S2 should be controlled so that sucrose mainly connects to the bridging agent at single points. In some embodiments, the molar ratio of sugar components: bridging agent: aminotrimethylenephosphonic acid is 1:(0.8~1.2):(0.8~1.2). By controlling the amount of bridging agent, on the one hand, the sucrose and aminotrimethylenephosphonic acid can be effectively linked, and on the other hand, the side reactions and cross-linking phenomena caused by excessive bridging agent are avoided.

[0036] Step S3, aminotrimethylenephosphonic acid (molecular formula C3H) 12 NO9P3 (with the structure N(CH2PO(OH)2)3, where the central nitrogen atom is a tertiary amine) is added to the intermediate solution. Under weakly alkaline conditions (7.5~9.5°C), stirring and heating continue, causing the remaining epoxy groups in the intermediate solution to undergo a ring-opening reaction with the central nitrogen atom of the aminotrimethylenephosphonic acid (reaction formula shown in Formula II). The nitrogen atom transforms from a tertiary amine to a quaternary ammonium, and the epoxy group undergoes ring-opening to generate an adjacent hydroxyl group, forming a stable quaternary ammonium salt-type linkage structure, thus obtaining the sugar-phosphonic acid covalently bonded super-retarder. After the reaction is complete, the sugar-phosphonic acid covalently bonded super-retarder is neutralized and filtered. If necessary, it can be further concentrated or dried to obtain a liquid or solid product.

[0037] Sucrose–O–CH2–CH(OH)–(CH2)4–CH(O)–CH2+N(CH2PO(OH)2)3→Sucrose–O–CH2–CH(OH)–(CH2)4–CH(OH)–CH2–N + (CH2PO(OH)2)3 Formula II In this formula, N(CH2PO(OH)2)3 is the molecular structure of aminotrimethylenephosphonic acid (ATMP), with the central nitrogen atom being a tertiary amine. Under the weakly basic conditions of step S3, the lone pair electrons of this tertiary amine nitrogen act as a nucleophile, attacking the retained epoxy carbon atom on the intermediate, resulting in a nucleophilic ring-opening reaction: the nitrogen atom gains a fourth substituent and is converted into a positively charged quaternary ammonium nitrogen (N). + Simultaneously, hydroxyl groups are formed on adjacent epoxide carbons. The final structure contains –CH(OH)–CH2–N. + (CH₂PO(OH)₂)₃ linker. Under weakly alkaline conditions (pH 7.5–9.5), the P–OH group of the phosphonic acid group partially ionizes to form P–O. - It forms an intramolecular charge balance with the positive charge of quaternary ammonium nitrogen, and the product as a whole exhibits a zwitterion structure.

[0038] If expanded, the main structure of the sugar-phosphonic acid covalently bonded superretarder can be written as Formula III: [Sugar skeleton]–O–CH2–CH(OH)–(CH2)4–CH(OH)–CH2–N + (CH2–PO(OH)2)3 Formula III Wherein, [sucrose backbone] represents the polyhydroxy structural unit of sucrose, N + It is a quaternary ammonium nitrogen formed by the nucleophilic ring-opening reaction of ATMP tertiary amine nitrogen, and reacts with the adjacent phosphonate (P–O) group. - This forms an intramolecular zwitterionic structure. Therefore, the product obtained in this invention is not a simple mixture of sucrose, aminotrimethylene phosphonic acid, and a bridging agent, but rather a covalently bonded product formed by the connection of carbohydrate functional units and phosphonic acid functional units via a bridging agent.

[0039] During step S3 of the reaction, infrared spectroscopy was continued to monitor the 910 cm⁻¹ region. -1 The characteristic peak of the epoxy group is observed. Once this peak disappears, it indicates that the epoxy groups retained on the intermediate have reacted essentially completely, at which point the reaction in step S3 ends. The system is then neutralized to neutral or near-neutral, filtered, and the sugar-phosphonic acid covalently bonded superretarder of this invention is obtained.

[0040] In some embodiments, the reaction temperature of step S3 is 50°C to 70°C, and the reaction time is 4h to 9h.

[0041] The sugar-phosphonic acid covalently bonded super retarder prepared by the above method can be added to cement paste, mortar, concrete, and other cement-based materials at a certain dosage to prolong their setting time. Preferably, the dosage of the sugar-phosphonic acid covalently bonded super retarder, based on solid content, is 0.1% to 0.2% of the cement mass. Within this dosage range, a significant retarding effect can be obtained while maintaining good later-stage mechanical properties.

[0042] The cement used in this invention is P·O 42.5 ordinary Portland cement with a specific surface area of ​​350–380 m². 2 / kg, the standard consistency water requirement is 27.5%. The water-cement ratio of the cement paste is 0.43. The setting time is determined according to GB / T 1346-2011, and the mechanical properties of the mortar are determined according to GB / T 17671-2021. The cement-sand ratio is 1:3, and the water-cement ratio is 0.50. All admixtures mentioned below are calculated based on solid content and expressed as a percentage of cement mass. Unless otherwise specified, all test results are the average of three parallel tests.

[0043] Example 1 In this embodiment, the preparation was carried out in a molar ratio of sucrose: 1,2,7,8-diepoxyoctane (DEO): aminotrimethylenephosphonic acid (ATMP) = 1:0.8:0.9. Based on 100.0 g of sucrose, 100.0 g (0.292 mol) of sucrose, 33.2 g (0.234 mol) of DEO, 78.8 g (0.263 mol) of ATMP, and 0.58 g of NaOH were weighed and prepared with 200 mL of acetone. First, 33.2 g of DEO was dissolved in 200 mL of acetone to obtain a transparent organic phase; then, 100.0 g of sucrose was dissolved in 280 mL of deionized water, and 0.58 g of NaOH was added to adjust the pH of the system to 10.5. Under mechanical stirring at 300 rpm, the DEO acetone solution was slowly added dropwise to the alkaline sucrose solution. After the addition was complete, the temperature was raised to 55°C and maintained for 4 h. Samples were taken at regular intervals during the reaction, and the 910 cm⁻¹ diameter was monitored by FTIR. -1 The characteristic peak of the epoxy group was observed, and the first step of the reaction was stopped when this peak decreased to about 50% of the initial peak intensity. Acetone was then removed by vacuum distillation at 40°C and -0.08 MPa to obtain an aqueous solution of the sucrose-DEO intermediate. 78.8 g of ATMP was dissolved in 100 mL of water and added to the above intermediate. The pH was adjusted to 8.5 with dilute HCl, and the reaction was continued at 60°C for 6 h until a concentration of 910 cm⁻¹ was reached. -1 The peak completely disappeared. After the reaction was complete, the solution was neutralized to pH 7.0, filtered, and an aqueous solution of SA-DEO-1 with a solid content of 28.2% was obtained. The solution was a pale yellow viscous liquid.

[0044] The SA-DEO-1 prepared in Example 1 was added to cement paste at a solid content of 0.15%, and the setting time was determined according to GB / T 1346-2011. A blank control group was set up as a reference control group consisting of pure cement paste / mortar without any retarders or admixtures—prepared solely from P·O 42.5 ordinary Portland cement and water according to standard methods. The results are shown in Table 1. The initial setting time reached 148.0 h, the final setting time was 171.5 h, and the difference between the initial and final setting times was 23.5 h. Compared with the blank control group (initial setting time of 4.3 h and final setting time of 5.1 h), the setting time was significantly prolonged. The mechanical properties of the mortar were determined according to GB / T 17671-2021. At 3 days, the specimens had not yet fully set; therefore, the 3-day compressive and flexural strengths were recorded as incompletely formed strength. At 7 days, the compressive strength was 21.5 MPa and the flexural strength was 4.8 MPa. At 28 days, the compressive strength increased to 57.2 MPa and the flexural strength increased to 8.5 MPa. Compared with the control group (28-day compressive strength 54.4 MPa and flexural strength 8.1 MPa), the compressive strength retention rate reached 105.1%, and the flexural strength retention rate reached 104.9%. This indicates that the product obtained in Example 1 can achieve ultra-long retarded setting at a dosage of 0.15%, while the later mechanical properties did not decrease but rather slightly improved.

[0045] Table 1 Performance Comparison of Examples and Comparative Examples Characterization results of product SA-DEO-1: FTIR characterization of product SA-DEO-1 showed: 910 cm⁻¹ -1 The characteristic peaks of the epoxy groups at both ends have completely disappeared, indicating that both epoxy groups at the ends of the DEO have participated in the reaction; 1125 cm⁻¹ -1 A new COC ether bond absorption peak appears at 1215 cm⁻¹, which is attributed to the ether bond formed after the ring-opening of sucrose hydroxyl groups; -1 The P=O stretching vibration peak is retained and attributed to the ATMP phosphonic acid group; 1030 cm⁻¹ -1 The change in absorption peak intensity is attributed to the addition of ATMP and the formation of quaternary ammonium groups (P–O). - The changes in the P-O stretching vibration caused by the alteration of the chemical environment of / P–OH.

[0046] 31P NMR (D₂O, 85% H₃PO₄ external standard): δ = 10.3 ppm, showing a chemical shift of approximately 0.5 ppm compared to free ATMP (δ = 10.8 ppm). This shift indicates that the central nitrogen atom of ATMP has undergone a bonding reaction with the epoxy group of the bridging agent, transforming from a tertiary amine to a quaternary ammonium; the change in the chemical environment of the nitrogen atom leads to the formation of the ortho-methylene-phosphonic acid group. 31 The chemical shift of P changes accordingly, corresponding to the –CH2–N in the target product. + The formation of the (CH2–PO(OH)2)3 quaternary ammonium salt type linkage structure is consistent.

[0047] GPC (deionized water as mobile phase, polyethylene glycol as standard): number average molecular weight Mn = 892 Da, weight average molecular weight Mw = 1198 Da, polydispersity index PDI = 1.34, which is basically consistent with the expected monomolecular bridged product (sucrose 342 Da + DEO 142 Da + ATMP 299 Da + two ring-opening hydrates = approximately 795 Da theoretical value). The deviation is due to a small amount of dimer and solvation effect.

[0048] Example 2 In this embodiment, the preparation was carried out in a molar ratio of sucrose: 1,2,7,8-diepoxyoctane (DEO): aminotrimethylenephosphonic acid (ATMP) = 1:1:1. Based on 100.0 g of sucrose, 100.0 g (0.292 mol) of sucrose, 41.5 g (0.292 mol) of DEO, 87.4 g (0.292 mol) of ATMP, and 0.70 g of NaOH were weighed and mixed with 250 mL of acetone. The specific operating steps were the same as in Example 1, except that the raw material ratio and the reaction time in the second step were adjusted. The first step was carried out at 55°C for 4 h, and the second step was carried out at 60°C for 7 h. After the reaction, an aqueous solution of SA-DEO-2 was obtained with a solid content of 30.5% and a pH of approximately 7.0.

[0049] The SA-DEO-2 obtained in Example 2 was added to cement paste at a solid content of 0.17%. The initial setting time was measured to be 158.0 h, the final setting time was 184.5 h, and the difference between initial and final setting time was 26.5 h, according to GB / T 1346-2011. This result is not only higher than the 148.0 h of Example 1, but also higher than the 138.5 h of Comparative Example 2 described later, indicating that the covalently bonded product described in Example 2 has the best retarding effect. According to GB / T 17671-2021, the specimens were not fully set at 3 days; at 7 days, the compressive strength was 23.0 MPa and the flexural strength was 4.5 MPa; at 28 days, the compressive strength reached 60.1 MPa and the flexural strength reached 8.8 MPa. Compared with the control group, the 28-day compressive strength retention rate was 110.5%, and the 28-day flexural strength retention rate was 108.6%. Compared with the optimal physical compound control example 2, the 28-day compressive strength increased from 58.9 MPa to 60.1 MPa. Therefore, Example 2 achieved the longest retarding time while also obtaining the highest late-stage mechanical properties among all examples of this invention.

[0050] Characterization results of product SA-DEO-2: FTIR characterization of product SA-DEO-2: 910 cm⁻¹ -1 The characteristic peaks of the epoxy groups completely disappeared; 1125 cm⁻¹ -1 The COC ether bond peak intensity is slightly stronger than that of SA-DEO-1, consistent with the slightly higher ether bond density caused by n(DEO) / n(sucrose) = 1 (higher than 0.8 in Example 1); 1215 cm⁻¹ -1 The P=O peak is clearly visible; 1030 cm⁻¹ -1 The P–O stretching vibration peak of the phosphonic acid group (reflecting the change in the chemical environment of the phosphonic acid group after ATMP incorporation) is also clearly visible.

[0051] 31P NMR: δ = 10.2 ppm, with the most significant chemical shift change (vs ATMP δ = 10.8 ppm), indicating that at the optimal molar ratio of 1:1:1, the central nitrogen atom of ATMP has the highest degree of ring-opening reaction with DEO, resulting in the largest proportion of quaternary ammonium salt linkages in the product, which corroborates the result that the retarding effect is optimal at this ratio.

[0052] GPC: Mn = 1023 Da, Mw = 1480 Da, PDI = 1.45, with a molecular weight slightly higher than SA-DEO-1, and n(DEO) = 1 (higher than n(DEO) = 0.8 in Example 1), resulting in a more complete consistency in the degree of bridging.

[0053] Example 3 In this embodiment, the preparation was carried out in a molar ratio of sucrose: 1,2,7,8-diepoxyoctane (DEO): aminotrimethylenephosphonic acid (ATMP) = 1:1.2:1. Based on 100.0 g of sucrose, 100.0 g (0.292 mol) of sucrose, 49.7 g (0.350 mol) of DEO, 87.4 g (0.292 mol) of ATMP, and 0.82 g of NaOH were weighed and mixed with 300 mL of acetone. The first step of the reaction was carried out at 60°C for 5 h, the second step at 65°C for 6 h, and the remaining steps were the same as in Example 1. After the reaction, an aqueous solution of SA-DEO-3 was obtained with a solid content of 31.0%. Due to the relatively high amount of DEO, the molecular weight of the main peak of the obtained product was slightly higher than that in Example 2.

[0054] The SA-DEO-3 obtained in Example 3 was added to cement paste at a solid content of 0.12%. The initial setting time was measured to be 126.0 h, the final setting time was 147.5 h, and the difference between initial and final setting time was 21.5 h, according to GB / T 1346-2011. Although the dosage in this group was only 0.12%, lower than 0.15% in Example 1 and 0.17% in Example 2, the initial setting time still exceeded 120 h, indicating that the product of this invention has a high retarding efficiency per unit dosage. According to GB / T 17671-2021, the specimens were not fully set at 3 days; at 7 days, the compressive strength was 24.8 MPa and the flexural strength was 4.9 MPa; at 28 days, the compressive strength was 59.5 MPa and the flexural strength was 8.7 MPa. Compared with the control group, the 28-day compressive strength retention rate was 109.4%, and the flexural strength retention rate was 107.4%. This demonstrates that the product of this invention can still achieve both ultra-long retardation and later-stage strength development even at lower dosages.

[0055] Characterization results of product SA-DEO-3: FTIR characterization of product SA-DEO-3: 910 cm⁻¹ -1 The characteristic peaks of the epoxy groups completely disappeared; due to n(DEO) / n(sucrose) = 1.2, the amount of DEO used was relatively high, 1125 cm⁻¹ -1 The COC peak intensity was the highest among the three batches of products; in addition, the 1030 cm⁻¹ peak intensity was the highest. -1 The P–O vibration absorption peak of the phosphonic acid group indicates that the phosphonic acid group is in a new chemical environment adjacent to the quaternary ammonium salt, confirming the incorporation of ATMP.

[0056] 31P NMR: δ = 10.4 ppm, the degree of chemical shift change is between SA-DEO-1 and SA-DEO-2, which is consistent with the situation where n(ATMP) = 1.0 (same as Example 2) but with slightly more bridging agent, some DEO may form single-end bridging (i.e. the hanging end is not completely quaternized with ATMP). GPC: Mn = 1148 Da, Mw = 1690 Da, PDI = 1.47, which is the highest molecular weight among the three batches of products, consistent with the possibility that some sucrose molecules have double-point bridging (two hydroxyl groups each attached to a DEO chain) when n(DEO) = 1.2.

[0057] Example 4 In this embodiment, the SA-DEO-2 aqueous solution prepared in Example 2 is used as a precursor solution for further post-processing to prepare a solid product. Specifically, the neutralized and filtered SA-DEO-2 aqueous solution is fed into a spray drying device, with the inlet air temperature controlled at 170°C and the outlet air temperature at 85°C. The resulting powder is collected to obtain a pale yellow solid SA-DEO product. This embodiment illustrates that the sugar-phosphonic acid covalently bonded super-retarder obtained by this invention can be used not only in liquid form but also in solid form, facilitating storage, transportation, and on-site measurement.

[0058] Example 5 The SA-DEO-2 aqueous solution prepared in Example 2 was added to the cement system at a solid content of 0.17%, and polycarboxylate F-type water-reducing agent was compounded at the same time to verify the compatibility between the product of the present invention and the water-reducing agent.

[0059] Comparative Example 1 Sucrose and ATMP were physically mixed at a mass ratio of 2:1 without bridging reactions, thus avoiding the formation of covalently bonded products. The sucrose content was 0.10%, the ATMP content was 0.05%, and the total content was 0.15%.

[0060] As shown in Table 2, Comparative Example 1 (i.e. Figure 2The physical compound system obtained by physical compound D1 was added to cement paste at a total dosage of 0.15%. According to GB / T 1346-2011, the initial setting time was 117.5 h, the final setting time was 132.5 h, and the difference between initial and final setting time was 15.0 h. According to GB / T 17671-2021, the specimen had not reached final setting at 3 days; at 7 days, the compressive strength was 20.0 MPa and the flexural strength was 4.6 MPa; at 28 days, the compressive strength was 54.3 MPa and the flexural strength was 8.0 MPa. Compared with Example 1, under the same total admixture of 0.15%, the initial setting time of the product of the present invention increased from 117.5 h to 148.0 h, an extension of 30.5 h; the final setting time increased from 132.5 h to 171.5 h, an extension of 39.0 h; and the 28-day compressive strength increased from 54.3 MPa to 57.2 MPa, an increase of 2.9 MPa. This indicates that after fixing the two functional units through covalent bonding, the retarding effect and later strength of the present invention are superior to those of simple physical compounding.

[0061] Table 2 Performance comparison between Example 1 and Comparative Example 1 Comparative Example 2 Sucrose and ATMP were physically mixed at a mass ratio of 4.7:1 without bridging reactions, thus avoiding the formation of covalently bonded products. The sucrose content was 0.14%, the ATMP content was 0.03%, and the total content was 0.17%. This formulation represents the optimal comparative ratio among existing physically compounded systems (i.e.,...). Figure 2 The physical compound D2 in it).

[0062] The physical compound system obtained in Comparative Example 2 was added to cement paste at a total dosage of 0.17%. According to GB / T 1346-2011, the initial setting time was 138.5 h, the final setting time was 162.5 h, and the difference between initial and final setting time was 24.0 h. According to GB / T 17671-2021, the specimens were not fully set at 3 days; at 7 days, the compressive strength was 24.2 MPa and the flexural strength was 4.4 MPa; at 28 days, the compressive strength was 58.9 MPa and the flexural strength was 8.6 MPa. Compared with Example 2, under the same total admixture of 0.17%, the initial setting time of the product of the present invention increased from 138.5 h to 158.0 h, an increase of 19.5 h; the final setting time increased from 162.5 h to 184.5 h, an increase of 22.0 h; the 28-day compressive strength increased from 58.9 MPa to 60.1 MPa, an increase of 1.2 MPa; and the 28-day flexural strength increased from 8.6 MPa to 8.8 MPa, an increase of 0.2 MPa. This comparative result shows that even compared with the existing optimal physical compound system, the covalently bonded product of the present invention still has a longer retarding time and better later-stage performance.

[0063] Summary of experimental results: (1) Retarding effect: In Example 1 of the present invention, the SA-DEO-1 at a dosage of 0.15% had an initial setting time of 148.0 h and a final setting time of 171.5 h; while in Comparative Example 1, at the same total dosage, the initial setting time was 117.5 h and the final setting time was 132.5 h. Compared with Comparative Example 1, the initial setting time of Example 1 was extended by 30.5 h and the final setting time was extended by 39.0 h. This indicates that, under the same dosage conditions, the retarding effect of the product of the present invention is superior to that of the physical compound system of sucrose and ATMP.

[0064] In Example 2 of the present invention, the SA-DEO-2 with an admixture content of 0.17% exhibited an initial setting time of 158.0 h and a final setting time of 184.5 h. These results are higher than those of Comparative Example 2 (138.5 h and 162.5 h) and Example 1 (148.0 h and 171.5 h), indicating that the product of the present invention exhibits the best retarding effect when the molar ratio of sucrose, DEO, and ATMP is 1:1:1. Under the same total admixture content of 0.17%, Example 2 showed an initial setting time extended by 19.5 h and a final setting time extended by 22.0 h compared to Comparative Example 2.

[0065] In Example 3 of the present invention, the SA-DEO-3, when the dosage was reduced to 0.12%, still achieved an initial setting time of 126.0 h and a final setting time of 147.5 h. Although the dosage in this group was lower than that in Examples 1 and 2, it still maintained an initial setting time of over 120 h, indicating that the product of the present invention still has good retarding ability at lower dosages.

[0066] (2) Mechanical properties: In Example 1, the 28-day compressive strength was 57.2 MPa, which was 2.8 MPa higher than the 54.4 MPa of the control group; the 28-day flexural strength was 8.5 MPa, which was 0.4 MPa higher than the 8.1 MPa of the control group.

[0067] In Example 2, the 28-day compressive strength was 60.1 MPa, which was 5.7 MPa higher than the control group and 1.2 MPa higher than Comparative Example 2; the 28-day flexural strength was 8.8 MPa, which was 0.7 MPa higher than the control group and 0.2 MPa higher than Comparative Example 2.

[0068] In Example 3, the 28-day compressive strength was 59.5 MPa, which was 5.1 MPa higher than that of the control group; the 28-day flexural strength was 8.7 MPa, which was 0.6 MPa higher than that of the control group.

[0069] In Example 5, the mortar strength was tested according to GB / T 17671-2021. The specimens were not fully set at 3 days; at 7 days, the compressive strength was 22.1 MPa and the flexural strength was 4.5 MPa; at 28 days, the compressive strength was 57.8 MPa and the flexural strength was 8.5 MPa. Compared with the control group, the 28-day compressive strength retention rate was 106.3%, and the flexural strength retention rate was 104.9%. According to GB / T 1346-2011, the initial setting time of the SA-DEO-2 and polycarboxylate F-type water-reducing agent compound system was 144.5 h, the final setting time was 168.0 h, and the difference between initial and final setting time was 23.5 h. Compared with Example 2 (initial setting time 158.0 h) without water-reducing agent, the initial setting time was shortened by about 13.5 h after adding water-reducing agent. This is related to the competitive effect of the carboxylic acid groups of polycarboxylate water-reducing agent on the adsorption sites on the surface of cement particles. However, the initial setting time still exceeded 140 h, which meets the requirements for ultra-retarded setting, indicating that the product of the present invention has good compatibility with polycarboxylate water-reducing agent.

[0070] As can be seen from the comparative examples, the advantages of this invention are twofold: first, under the same dosage conditions, the setting time is longer; second, while the setting time is extended, the 28-day compressive and flexural strengths are not lower than those of the physically compounded system. Taking Example 2 and Comparative Example 2 as examples, both have a total dosage of 0.17%, but the initial setting time of Example 2 increased from 138.5 h to 158.0 h, the final setting time increased from 162.5 h to 184.5 h, and the 28-day compressive strength increased from 58.9 MPa to 60.1 MPa. Therefore, it is evident that after fixing two functional components in the same molecule through covalent bonding, the retarding effect and later-stage performance of this invention are superior to existing physically compounded methods.

[0071] It is evident that the product of this invention achieves an ultra-long retarding effect while maintaining good mechanical properties in the later stages. The sugar-phosphonic acid covalently bonded ultra-retarder prepared by this invention exhibits good ultra-long retarding effects within a dosage range of 0.12% to 0.17%. Among them, the preferred formulation at a dosage of 0.17% achieves an initial setting time of 158.0 h, a final setting time of 184.5 h, and a 28-day compressive strength of 60.1 MPa, indicating that this invention can effectively balance ultra-long retarding and good mechanical properties in the later stages.

[0072] The experimental results are analyzed as follows: (I) The influence of covalent bond structure on the retarding mechanism Multiple hydroxyl groups in sucrose molecules (especially those at C-2, C-3, and C-4 positions) can be adsorbed onto the surface of cement particles through hydrogen bonding and electrostatic interactions, forming a physical barrier layer in the early hydration stage and delaying Ca2+ hydration. 2+ The release into solution and the hydration process of C3S and C3A. The three phosphonic acid groups in the ATMP molecule can react with free Ca in solution. 2+ The strong chelation coordination of calcium sites on the surface of cement particles inhibits the nucleation and crystal growth of hydration products (especially CSH gel and ettringite). In traditional physical compound systems, sucrose and ATMP exist as independent molecules, and their competitive adsorption and diffusion behaviors on the surface of cement particles are not completely synchronized, limiting the synergistic effect. This invention, however, uses a DEO bridging agent to fix the sucrose and ATMP ends in the same molecule, allowing the two functional groups to work synergistically within the same molecule's radius of influence: after the sucrose end is adsorbed and positioned first, the phosphonic acid groups at the ATMP end can chelate with surrounding calcium ions under locally high concentration conditions, thus producing a site-level synergistic retarding effect that is stronger than intermolecular synergy. This is the fundamental reason why SA-DEO has a significantly longer retarding time than physical compound systems at the same total dosage.

[0073] (II) Effect of molar ratio on product structure and properties The comparison of Examples 1-3 shows that the optimal molar ratio of sucrose:DEO:ATMP = 1:1:1 (Example 2) is the optimal ratio of the present invention. When n(DEO) / n(sucrose) = 0.8 (Example 1), the bridging agent is relatively insufficient, and some sucrose molecules fail to attach to DEO, existing as free sucrose. This results in a lower proportion of the target covalently bonded product, and the retarding effect (initial setting time 148.0 h) is slightly lower than that of Example 2 (158.0 h). When n(DEO) / n(sucrose) = 1.2 (Example 3), DEO is in excess. Some sucrose molecules may form a double-point bridging structure by attaching one DEO chain to each of the two hydroxyl groups, resulting in a higher molecular weight (Mn = 1148 Da) and a more compact molecular configuration, which to some extent affects the spatial extensibility of the ATMP terminal phosphonic acid group. However, since the dosage is reduced to 0.12%, the initial setting time still reaches 126.0 h, indicating that the retarding efficiency per unit dosage is still better than that of the physical compound system (Comparative Example 1 has an initial setting time of only 117.5 h at a dosage of 0.15%). In summary, the 1:1:1 ratio results in the highest purity of the monomolecular bridging product (the lowest GPC PDI is 1.45) and the best retarding effect, making it the preferred formulation of this invention.

[0074] (III) Mechanism for maintaining mechanical properties in the later stages In all embodiments of this invention, while achieving ultra-long retarded setting, the 28-day compressive strength not only did not decrease but actually increased by 2.8–5.7 MPa compared to the control group (an increase of 5%–10%). This result can be explained in two ways: First, the ultra-long retarded setting significantly reduces the cement hydration rate, prolonging the initial hydration exothermic period, which is conducive to the slow growth of hydration products under more uniform conditions, forming a denser microstructure and reducing the generation of early cracks and pores; Second, the phosphonic acid groups at the ATMP end chelate a large amount of Ca during the ultra-retarded setting stage. 2+ Furthermore, the calcium is released gradually. During the later stages of hydration (7–28 days), as the system pH decreases, some chelated calcium is deposited as hydration products, compensating for the early strength delay caused by retarded setting, ultimately resulting in a denser microstructure at 28 days. In addition, the adsorption between the sucrose end and cement particles gradually disappears after hydration, without forming a permanently weakened interface, thus not adversely affecting later strength. The synergistic effect of these mechanisms is the reason why the product of this invention can maintain or even improve its mechanical properties at 28 days under ultra-retarded setting conditions.

[0075] (iv) Comprehensive comparison with existing optimal physical composite systems Using Comparative Example 2 (sucrose:ATMP = 4.7:1, total dosage 0.17%) as the existing optimal physical compound benchmark, a comprehensive comparison was made with Example 2 of the present invention (SA-DEO-2, 0.17%): In terms of retarding effect, the initial setting time of Example 2 (158.0 h) was extended by 19.5 h (+14.1%) compared with Comparative Example 2 (138.5 h), and the final setting time was extended by 22.0 h (+13.5%); in terms of mechanical properties, the 28-day compressive strength increased from 58.9 MPa to 60.1 MPa (+2.0%), and the 28-day flexural strength increased from 8.6 MPa to 8.8 MPa (+2.3%); in terms of stability, the covalently bonded product can maintain a stable retarding effect under different ingredient precision and construction conditions because the functional groups are locked in the same molecule in a fixed proportion, while the physical compound system is more sensitive to the error of the component ratio (setting time fluctuation of more than ±15%). In summary, the covalent bonded design of this invention has significant advantages over physical compounding, and is particularly suitable for engineering applications such as large-volume concrete, ultra-long-distance pumping, and construction in high-temperature environments where precise setting time is required.

[0076] In summary, the preparation method of the sugar-phosphonic acid covalently bonded super-retarder of the present invention includes the following steps: Step S1, dissolving the sugar component in water to obtain a sugar solution, and adjusting the pH of the sugar solution to be greater than 7; Step S2, providing a bridging agent, wherein both ends of the bridging agent contain epoxy groups, dissolving the bridging agent in an organic solvent to obtain an organic phase solution, adding the organic phase solution to the sugar solution, wherein the hydroxyl groups of the sugar molecules in the sugar solution undergo a ring-opening reaction with the epoxy groups at one end of the bridging agent to obtain an intermediate solution containing epoxy groups; Step S3, adding aminotrimethylene phosphonic acid to the intermediate solution, wherein the epoxy groups in the intermediate solution undergo a ring-opening reaction with the amino groups in the aminotrimethylene phosphonic acid to obtain the sugar-phosphonic acid covalently bonded super-retarder. Under low dosage conditions, the setting time of cement-based materials can be significantly extended, improving the stability and controllability of the super-retarding effect, and while providing long-term retardation, the later mechanical properties of the material do not decrease significantly.

[0077] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for preparing a sugar-phosphonic acid covalently bonded superretarder, characterized in that, Includes the following steps: Step S1: Dissolve the carbohydrate components in water to obtain a carbohydrate solution, and adjust the pH of the carbohydrate solution to be greater than 7; Step S2: A bridging agent is provided, wherein both ends of the bridging agent contain epoxy groups. The bridging agent is dissolved in an organic solvent to obtain an organic phase solution. The organic phase solution is added to the sugar solution. The hydroxyl groups of the sugar molecules in the sugar solution undergo a ring-opening reaction with the epoxy groups at one end of the bridging agent to obtain an intermediate solution containing epoxy groups. Step S3: Add aminotrimethylenephosphonic acid to the intermediate solution, where the epoxy groups in the intermediate solution undergo a ring-opening reaction with the amino groups in the aminotrimethylenephosphonic acid to obtain the sugar-phosphonic acid covalently bonded super retarder.

2. The preparation method according to claim 1, characterized in that, The sugar component is selected from at least one of sucrose, glucose, fructose, maltose, and lactose.

3. The preparation method according to claim 1, characterized in that, The bridging agent is 1,2,7,8-diepoxyoctane.

4. The preparation method according to claim 1, characterized in that, The molar ratio of the carbohydrate component to the bridging agent to aminotrimethylenephosphonic acid is 1:(0.8~1.2):(0.8~1.2).

5. The preparation method according to claim 1, characterized in that, The pH of the sugar solution is 9-11.

6. The preparation method according to claim 1, characterized in that, The reaction temperature in step S2 is 40℃~65℃, and the reaction time is 3h~6h.

7. The preparation method according to claim 1, characterized in that, The reaction temperature of S3 is 50℃~70℃, and the reaction time is 4h~9h.

8. The preparation method according to claim 1, characterized in that, In steps S2 and S3, the 910 cm⁻¹ infrared spectrum is monitored. -1 The intensity of the characteristic peak of the epoxy group at the reaction site is used to control the reaction process.

9. A sugar-phosphonic acid covalently bonded superretarder prepared by the preparation method according to any one of claims 1 to 8, characterized in that, The sugar-phosphonic acid covalently bonded super retarder is composed of a sugar component, a bridging agent, and aminotrimethylenephosphonic acid linked by covalent bonds, wherein both ends of the bridging agent contain epoxy groups.

10. The sugar-phosphonic acid covalently bonded superretarder as described in claim 9, characterized in that, The bridging agent is 1,2,7,8-diepoxyoctane.

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