Dispersing agent for preparing nanocrystalline calcium silicate and preparation method of dispersing agent

Abstract

The invention provides a preparation method of a dispersant for preparing nanocrystalline calcium silicate, which comprises the following steps: preparing a polyether macromonomer solution, controlling the temperature at 35-55 DEG C, introducing nitrogen, stirring until the solution is clear, and adding an initiator; dropwise adding the chain transfer agent solution and the small molecule monomer solution into the reaction solution; the molar ratio of the micromolecular monomer to the polyether macromonomer is (2-6.5): 1; the micromolecular monomer is a mixture of methacrylic acid and gamma-methacryloyloxypropyl trimethoxy silane or a mixture of methacrylic acid and methacryloyloxyethyl trimethyl ammonium chloride; and after dropwise adding, preserving heat, airing to room temperature, and adjusting the pH value to 7 to obtain the dispersing agent. According to the method, by-products can be effectively avoided, the polymerization degree and the yield of the dispersing agent are improved, the obtained dispersing agent has the effects of enhancing steric hindrance and electrostatic repulsion and can exert intermolecular Van der Waals force or more stable Si-O-Si chemical bonding force, and the nano-microcrystalline calcium silicate particles prepared from the dispersing agent are uniform in size and are smaller than 100 nm; the structural stability and the dispersion stability are good.

Description

Technical Field

[0001] This invention belongs to the field of dispersant synthesis technology, and in particular relates to a dispersant for preparing nanocrystalline calcium silicate, a method for preparing the dispersant, and its application. Background Technology

[0002] Nanocrystalline calcium silicate early-strength agent is a high-performance concrete admixture, its core component being nanoscale hydrated calcium silicate (CSH). CSH nanoparticles have a large specific surface area, making them prone to agglomeration and re-agglomeration during solution synthesis, resulting in coarse CSH particle size and precipitation. Therefore, dispersants are introduced during the preparation of nanocrystalline calcium silicate early-strength agent to reduce agglomeration and re-agglomeration, thereby improving the stability of the nano-CSH particle suspension.

[0003] Existing dispersants generally achieve stable distribution of nano-CSH particles in the liquid phase through charge adsorption and binding with CSH, thereby solving the aggregation and sedimentation problems of nucleating agents in nano-CSH varieties. However, existing dispersants relying solely on the -COO- charge adsorption mechanism have limited dispersion effects, and the prepared nano-microcrystalline calcium silicate exhibits aggregation and sedimentation problems after about one month of storage. Furthermore, during the preparation process of existing dispersants, the introduction of water inevitably generates the byproduct PEG. The presence of PEG negatively impacts the polymerization reaction and dispersant performance, reducing the degree of polymerization, conversion rate, and significantly decreasing the dispersibility of the prepared dispersant.

[0004] Therefore, developing new dispersants, breaking through the single charge stabilization mechanism, and optimizing the synthesis process to reduce interference from byproducts and improve the degree of polymerization and yield have become key research directions. Summary of the Invention

[0005] In view of this, to solve the above-mentioned technical problems, this invention proposes a dispersant for preparing nanocrystalline calcium silicate, a method for preparing the dispersant, and its application. By introducing small molecule monomers with specific groups and strictly controlling the ratio of small molecule monomers to macromolecule monomers during the synthesis process, while precisely controlling the process conditions, the generation of by-products is effectively avoided, and the degree of polymerization and yield of the dispersant are improved. The prepared dispersant can enhance steric hindrance and electrostatic repulsion, and can also exert intermolecular van der Waals forces or more stable Si-O-Si chemical bonding forces. As a dispersant, the nanocrystalline calcium silicate particles prepared by it are uniform in size and all below 100 nm, with good structural stability and dispersion stability, and the shelf life is extended from a maximum of 1 month to 6 months.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] This invention provides a method for preparing a dispersant for preparing nanocrystalline calcium silicate, characterized by comprising the following steps:

[0008] S1. Prepare a polyether macromonomer solution with a mass concentration of 20wt%-150wt%, control the temperature at 35-55℃, stir with nitrogen gas until the solution is clear, and add the initiator;

[0009] S2. Prepare a chain transfer agent solution by adding the chain transfer agent solution dropwise to the reaction solution obtained in S1;

[0010] S3. Prepare a small molecule monomer solution by adding it dropwise to the reaction solution obtained in S2. The molar ratio of the small molecule monomer to the polyether macromonomer is 2-6.5:1. The small molecule monomer is a mixture of methacrylic acid (MAA) and γ-methacryloyloxypropyltrimethoxysilane (KH570) or a mixture of methacrylic acid and methacryloyloxyethyltrimethylammonium chloride (DMC).

[0011] S4. After the addition is complete, keep the mixture warm to continue the reaction, then cool it to room temperature and adjust the pH value to 7 to obtain the dispersant.

[0012] Furthermore, in S1, the polyether macromonomer is one or more of HPEG, EPEG, TPEG, and APEG; the molecular weight of the polyether macromonomer is 550 to 5000; the solvent in the polyether macromonomer solution is deionized water or a mixture of deionized water and tetrahydrofuran; and the stirring speed is 300 rpm to 400 rpm.

[0013] Furthermore, in S1, the initiator is one or more of ammonium persulfate (APS), sodium bisulfite (NaHSO3), vitamin C (Vc), and H2O2; the molar ratio of the initiator to the polyether macromonomer is 0.015-0.079:1.

[0014] Furthermore, in step S2, the molar concentration of the chain transfer agent in the chain transfer agent solution is 0.04-0.15 mol / L, and the mass fraction of the chain transfer agent in the reaction solution is 0.27%-0.30%.

[0015] Furthermore, in S2, the chain transfer agent is one or more of 3-mercaptopropionic acid (MPC), 2-mercaptoethanol (β-ME), and sodium methylpropenesulfonate (SMAS).

[0016] Furthermore, in S3, the molar concentration of the small molecule monomer in the small molecule monomer solution is 0.6-1.03 mol / L, and the mass fraction of the small molecule monomer in the reaction solution is 2%-16%.

[0017] Furthermore, in step S2, the dropping rate of the chain transfer agent solution is 3.56 ml / h-5.75 ml / h; in step S3, the dropping rate of the small molecule monomer solution is 4.92 ml / h-41.64 ml / h.

[0018] Furthermore, in step S4, after the dripping is completed, the temperature is maintained for 1-2 hours, during which the initiator is added for 30-50 minutes. The amount of initiator added is 5%-10% of the amount of initiator added in step S1.

[0019] A second aspect of the present invention provides a dispersant for preparing nanocrystalline calcium silicate obtained by the preparation method described above.

[0020] Furthermore, the molecular weight of the dispersant for preparing nanocrystalline calcium silicate obtained by the above preparation method is 50,000-100,000.

[0021] The third aspect of this invention provides the application of the dispersant obtained by the preparation method described above in the preparation of nanocrystalline calcium silicate early strength agent.

[0022] Compared with existing technologies, the dispersant and preparation method for preparing nanocrystalline calcium silicate described in this invention have the following advantages:

[0023] (1) The dispersant preparation method of the present invention introduces cationic small molecules or silane small molecules. The presence of cationic small molecules enhances the degree of polymerization between the macromonomer and the small molecules through charge adsorption. Silane small molecules exist with the macromonomer through intermolecular van der Waals forces due to their Si-O-Si structural characteristics. The presence of cationic small molecules or silane small molecules reduces the formation of PEG during the reaction. Therefore, the introduction of cationic small molecules and silane small molecules can improve the degree of polymerization and yield of the prepared dispersant.

[0024] (2) The dispersant described in this invention has a higher degree of polymerization completion, and the resulting dispersant has a larger molecular weight. The effect of steric hindrance and electrostatic repulsion is more obvious. Therefore, when it is used as a dispersant in the preparation of nanocrystalline calcium silicate, the degree of dispersion of the prepared nanocrystalline calcium silicate is higher, the lifespan is longer, and the time for agglomeration is extended from 1 month to 6 months.

[0025] (3) Because the dispersant described in this invention introduces cationic small molecules or silane small molecules, during the preparation process of nanocrystalline calcium silicate, the cationic molecules in the dispersant can form intermolecular van der Waals forces with the Si-O-Si structure in the early strength agent of nanocrystalline calcium silicate, and interact with the carboxyl groups through Ca... 2+The chelation effect, resulting in charge adsorption, combines two forces, enhancing the stabilizing effect of the dispersant on the nanocrystal nucleus structure. Furthermore, the introduction of small silane molecules into the dispersant can improve the charge adsorption mechanism on the CSH surface, which is influenced by Ca²⁺. 2+ The complexation transforms into a more stable Si-O-Si chemical bonding mode, which can significantly increase the stability of CSH crystal nuclei as a dispersant. Therefore, the dispersant of the present invention introduces cationic small molecules or silane small molecules, which can enhance the steric hindrance effect and also increase the intermolecular van der Waals forces or Si-O-Si chemical bonding effect, thereby controlling the nanoparticle size of nanocrystalline calcium silicate to below 100 nm. Attached Figure Description

[0026] Figure 1 The infrared spectra of the dispersants prepared in Examples 1, 2 and Comparative Example 1 are shown; where line a represents Comparative Example 1, line b represents Example 1 and line c represents Example 2.

[0027] Figure 2 The GPC spectra of the dispersants prepared in Examples 1, 2, and 1 are shown below; Figure 2 a is comparative example 1. Figure 2 b is Example 1. Figure 2 c represents Example 2;

[0028] Figure 3 The image shows the nanoscale size distribution of nanocrystalline calcium silicate prepared using the dispersants prepared in Examples 1, 2, and 1, respectively. Line 1 represents the size distribution of nanocrystalline calcium silicate prepared using the dispersant of Comparative Example 1, line 2 represents the size distribution of nanocrystalline calcium silicate prepared using the dispersant of Example 1, and line 3 represents the size distribution of nanocrystalline calcium silicate prepared using the dispersant of Example 2. Detailed Implementation

[0029] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0030] The present invention will now be described in detail with reference to the embodiments and accompanying drawings.

[0031] Example 1

[0032] The dispersant is prepared by the following steps:

[0033] S1. Dissolve 120g HPEG in 100g water, heat to 35℃, purge with nitrogen, stir continuously at 400rpm until the solution is clear, add 0.6g APS, and react at 35℃ for 10min.

[0034] S2. Dissolve 0.3g ascorbic acid and 0.8g 3-mercaptopropionic acid in 10g water to prepare a chain transfer agent solution; add the chain transfer agent solution dropwise to the reaction solution obtained in S1 at a rate of 3.56ml / h.

[0035] S3. Dissolve 10.7g of methacrylic acid and 31g of KH-570 in 30g of water to prepare a small molecule monomer solution; add the small molecule monomer solution dropwise to the reaction solution obtained in S2 at a dropping rate of 4.92ml / h.

[0036] S4. After the addition is completed, keep the solution warm for 1 hour, during which 0.03g of APS is added after 30 minutes of warming. Then, let it cool to room temperature and adjust the pH of the reaction solution to 7 using 0.1M sodium hydroxide solution to obtain the dispersant.

[0037] The calculated dispersant yield was 89%.

[0038] Example 2

[0039] The dispersant is prepared by the following steps:

[0040] S1. Dissolve 120g HPEG in 100g water, heat to 35℃, purge with nitrogen, stir continuously at 400rpm until the solution is clear, add 0.6g APS, and react at 35℃ for 10min.

[0041] S2. Dissolve 0.8g SMAS in 10g water to prepare a chain transfer agent solution; add the chain transfer agent solution dropwise to the reaction solution obtained in S1 at a dropping rate of 5.75ml / h.

[0042] S3. Dissolve 19g of methacrylic acid and 2.6g of DMC in 30g of water to prepare a small molecule monomer solution; add the small molecule monomer solution dropwise to the reaction solution obtained in S2 at a rate of 10ml / h.

[0043] S4. After the addition is completed, keep the solution warm for 1 hour, during which 0.06 g of APS is added after 30 minutes of warming. Then, let it cool to room temperature and adjust the pH of the reaction solution to 7 using 0.1 M sodium hydroxide solution to obtain the dispersant.

[0044] The calculated dispersant yield was 92%.

[0045] Comparative Example 1

[0046] The dispersant is prepared by the following steps:

[0047] S1. Dissolve 120g HPEG in 100g water, heat to 35℃, purge with nitrogen, stir continuously at 400rpm until the solution is clear, add 0.6g APS, and react at 35℃ for 10min.

[0048] S2. Dissolve 0.3g ascorbic acid and 0.8g 3-mercaptopropionic acid in 10g water to prepare a chain transfer agent solution; add the chain transfer agent solution dropwise to the reaction solution obtained in S1 at a rate of 3.56ml / h.

[0049] S3. Dissolve 18g of acrylic acid in 30g of water to prepare a small molecule monomer solution; add the small molecule monomer solution dropwise to the reaction solution obtained in S2 at a dropping rate of 4.92ml / h.

[0050] S4. After the addition is completed, keep the solution warm for 1 hour, during which 0.04 g of APS is added after 30 minutes of warming. Then, let it cool to room temperature and adjust the pH of the reaction solution to 7 using 0.1 M sodium hydroxide solution to obtain the dispersant.

[0051] The calculated dispersant yield was 75%.

[0052] Performance testing:

[0053] 1. For example Figure 1 The infrared spectra of the dispersants prepared in Examples 1 and 2 and Comparative Example 1 are shown in the figure, where a is Comparative Example 1, b is Example 1, and c is Example 2.

[0054] Depend on Figure 1 As can be seen from line a, the dispersant prepared solely using AA as a small molecule monomer has a concentration at 3446 cm⁻¹. -1 The stretching vibration peak of the hydroxyl group (-OH) appears on both sides, at 1728 cm⁻¹. -1 There are stretching vibration peaks of carboxyl groups (C=O) on both sides, at 1110 cm⁻¹. -1 The peaks on the left and right represent the stretching vibrations of the ether bond (COC). The peak is located at 1344 cm⁻¹. -1 CN stretching vibration peaks appeared nearby; by Figure 1 As shown by line b, the dispersant prepared by introducing KH-570 as a small molecule monomer, in addition to having the absorption peak in line a, also exhibits an absorption peak at 920 cm⁻¹. -1 and 680cm -1 It is the vibrational peak of the Si-O bond, 2889 cm⁻¹ -1 The presence of C—H stretching vibrations indicates the introduction of the kh-570 silane structure; Figure 1 As can be seen from line c, the dispersant prepared by introducing the cationic monomer DMC as a small molecule monomer, in addition to having the absorption peak in line a, also exhibits absorption peaks in the 1250–1300 cm⁻¹ range. -1 The peak is the stretching vibration peak of the sulfonic acid group, 1110 cm⁻¹. -1 The left and right peaks represent the stretching vibrations of the ether bond (COC), at 1344 cm⁻¹. -1 The presence of a CN stretching vibration peak nearby indicates the presence of cationic groups in the synthesized dispersant.

[0055] 2. For example Figure 2 The GPC spectra of the dispersants prepared in Examples 1 and 2 and Comparative Example 1 are shown in the figure. Figure 2 a is comparative example 1. Figure 2 b is Example 1. Figure 2 c represents Example 2;

[0056] Depend on Figure 2 As can be seen from a, the dispersant prepared solely using AA as a small molecule monomer has an optimal residence time of 9-10 min and a weight-average molecular weight of 24919. The significant residence time at 12-13 min indicates a relatively high amount of residual small molecules in the sample. Figure 2 As shown in b, the dispersant prepared by introducing KH-570 as a small molecule monomer has an optimal residence time of 7-8 minutes, a weight-average molecular weight of 71,900, and almost no residue of small molecules; Figure 2 c indicates that the dispersant prepared by introducing the cationic monomer DMC as a small molecule monomer has an optimal residence time of 7.5-8.5 min and a weight-average molecular weight of 61803, with a small amount of small molecule residue around 12 min.

[0057] The larger the molecular weight of the obtained dispersant, the more and longer the branched chains, and the more obvious the advantage of steric hindrance, the more obvious the dispersion effect on nanoparticles. Therefore, the dispersants prepared in Examples 1 and 2 will have better dispersion effect and longer storage time when applied to the early strength agent of nanocrystalline calcium silicate.

[0058] Application examples

[0059] The dispersants prepared in Examples 1 and 2 and Comparative Example 1 were respectively applied to the preparation of nanocrystalline calcium silicate early strength agents. The preparation process is as follows:

[0060] (1) Dissolve 4.5g of dispersant (the dispersant prepared in Example 1, Example 2 or Comparative Example 1) in 65ml of water, add 20wt% sodium hydroxide solution, adjust the pH to 10, heat to 50℃, purge with nitrogen, and stir continuously at 400rpm.

[0061] (2) Dissolve 4g Ca(NO3)2·4H2O in 6ml of 30% ethanol aqueous solution, and dissolve 3.6g Na2SiO3·5H2O in 21ml of 30% ethanol aqueous solution. Heat and stir until fully dissolved into a transparent liquid. Add calcium nitrate solution and sodium silicate solution dropwise at rates of 0.5ml / min and 1.16ml / min respectively, and monitor the pH value at any time. When the pH is lower than 11.5, add 20wt% sodium hydroxide solution; when the pH is higher than 12.5, add 0.25M nitric acid.

[0062] (3) After the calcium nitrate solution and sodium silicate solution are added dropwise, the reaction temperature is raised to 60℃ and reacted for 3 hours. Then the temperature is gradually reduced to 50℃ and reacted for 5 hours. Then the temperature is gradually reduced to room temperature. During the process, the pH value is monitored at any time. According to the pH change, 20wt% sodium hydroxide solution or 0.25M nitric acid is added dropwise until the pH stabilizes at 12.0 to obtain nanocrystalline calcium silicate emulsion.

[0063] The nanoscale size of three types of nanocrystalline calcium silicate prepared using the dispersants of Examples 1 and 2 and Comparative Example 1 was detected, such as... Figure 3 As shown in the figure, 1 represents the size distribution of the nanocrystalline calcium silicate prepared using the dispersant of Comparative Example 1, 2 represents the size distribution of the nanocrystalline calcium silicate prepared using the dispersant of Example 1, and 3 represents the size distribution of the nanocrystalline calcium silicate prepared using the dispersant of Example 2.

[0064] Depend on Figure 3 It can be seen that the nanocrystalline calcium silicate prepared with the dispersant of Comparative Example 1 has a crystal nucleus size of 125nm-893nm and a D50 of 573nm; the nanocrystalline calcium silicate prepared with the dispersant of Example 1 has a crystal nucleus size of 50nm-64nm and a D50 of 86nm; and the nanocrystalline calcium silicate prepared with the dispersant of Example 2 has a crystal nucleus size of 58nm-220nm and a D50 of 98nm.

[0065] Agglomeration experiments were conducted on three types of nanocrystalline calcium silicate prepared using the dispersants of Examples 1 and 2 and Comparative Example 1. After standing and storage, the nanocrystalline calcium silicate prepared using the dispersant of Comparative Example 1 showed obvious agglomeration after one month of storage, while the nanocrystalline calcium silicate prepared using the dispersants of Examples 1 and 2 showed slight agglomeration after 6 months of storage.

[0066] comprehensive Figure 2 and Figure 3 The results show that the introduction of small molecule monomers KH-570 and cationic monomers DMC can increase the degree of polymerization of the dispersant, thereby increasing the molecular weight of the dispersant. This enhances steric hindrance and electrostatic repulsion, while also increasing intermolecular van der Waals forces and chemical bond forces. As a result, the dispersibility of nanocrystalline calcium silicate is more uniform and effective, further extending the storage time of the nanocrystalline calcium silicate emulsion. It also reduces agglomeration and is beneficial for controlling the nanoparticle size.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A production method for producing a dispersant for nanocrystalline calcium silicate, characterized by, It comprises the following steps: S1, preparing a polyether macromonomer solution with a mass concentration of 20wt%-150wt%, controlling the temperature at 35-55℃, stirring under nitrogen until the solution is clear, and adding an initiator; S2, preparing a chain transfer agent solution, and adding the chain transfer agent solution into the reaction solution obtained in S1; S3, preparing a small molecule monomer solution, and adding the small molecule monomer solution into the reaction solution obtained in S2; the molar ratio of the small molecule monomer to the polyether macromonomer is 2-6.5:1; the small molecule monomer is a mixture of methacrylic acid and γ-methacryloxypropyltrimethoxysilane or a mixture of methacrylic acid and methacryloxyethyltrimethylammonium chloride; S4, after the addition is completed, continuing the reaction by keeping warm, and then allowing to stand to room temperature, adjusting the pH value to 7, to obtain the dispersant.

2. The preparation method for preparing a dispersant of nanometer microcrystalline calcium silicate according to claim 1, characterized in that: In S1, the polyether macromonomer is one or more of HPEG, EPEG, TPEG, and APEG; the molecular weight of the polyether macromonomer is 550-5000; the solvent in the polyether macromonomer solution is deionized water or a mixture of deionized water and tetrahydrofuran; and the stirring speed is 300rpm-400rpm.

3. The preparation method for preparing a dispersant of nanometer microcrystalline calcium silicate according to claim 1, characterized in that: In S1, the initiator is one or more of ammonium persulfate, sodium bisulfite, vitamin C, and H2O2; and the molar ratio of the initiator to the polyether macromonomer is 0.015-0.079:

1.

4. The preparation method for preparing a dispersant of nanometer microcrystalline calcium silicate according to claim 1, characterized in that: In S2, the molar concentration of the chain transfer agent in the chain transfer agent solution is 0.04-0.15mol / L, and the mass fraction of the chain transfer agent in the reaction solution is 0.27%-0.30%.

5. The preparation method for preparing a dispersant of nanometer microcrystalline calcium silicate according to claim 1, characterized in that: In S2, the chain transfer agent is one or more of 3-mercaptopropionic acid, 2-mercaptoethanol, and sodium methacrylsulfonate.

6. The preparation method for preparing a dispersant of nanometer microcrystalline calcium silicate according to claim 1, characterized in that: In S3, the molar concentration of the small molecule monomer in the small molecule monomer solution is 0.6-1.03mol / L, and the mass fraction of the small molecule monomer in the reaction solution is 2%-16%.

7. The preparation method for preparing a dispersant of nanometer microcrystalline calcium silicate according to claim 1, characterized in that: In S2, the dropping speed of the chain transfer agent solution is 3.56ml / h-5.75ml / h; and in S3, the dropping speed of the small molecule monomer solution is 4.92ml / h-41.64ml / h.

8. The preparation method for preparing a dispersant of nanometer microcrystalline calcium silicate according to claim 1, characterized in that: In S4, after the addition is completed, keeping warm for 1-2h, wherein the initiator is supplemented during the period of 30min-50min, and the amount of the supplemented initiator is 5%-10% of the amount of the initiator added in S1.

9. A dispersant for preparing nanocrystalline calcium silicate, which is obtained by the preparation method according to any one of claims 1 to 8.

10. Use of a dispersant obtained by the production process according to any one of claims 1 to 8, characterized in that: Use in preparing a nanocrystalline calcium silicate early strength agent.

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