Hydrogel particles, methods of making and using the same

Abstract

The application discloses a kind of hydrogel particles and its preparation method and application.The hydrogel particles of the present application have core-shell structure, the inner core is micron inorganic particle, and the shell is hydrogel.The preparation method of the hydrogel particles of the present application includes the following steps: micron inorganic particle dispersion liquid, hydrogel precursor aqueous solution and initiator aqueous solution are mixed, then crosslinking reaction is carried out, then drying and pulverization are carried out, and the hydrogel particles are obtained.The hydrogel particles of the present application have good compatibility, good distribution uniformity, do not affect cement hydration and other advantages when used in cement-based materials, which can significantly improve the toughness and crack resistance of cement-based materials, thereby improving the durability of cement-based materials, prolonging its service life, and suitable for large-scale popularization and application.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, in particular to a hydrogel particle and a preparation method and application thereof. BACKGROUND

[0002] Cement-based materials will produce self-shrinkage during use, which will easily lead to cracking. The root cause of this phenomenon is that the internal relative humidity of the cement-based material will gradually decrease during the hydration process, and shrinkage stress will be generated under the action of capillary effect. The brittleness of the cement-based material is significant, and it is extremely easy to crack under tensile stress.

[0003] At present, the toughness of cement-based materials is mainly improved by directly adding organic polymers to the cement-based materials, so as to reduce the cracking caused by self-shrinkage. However, in order to effectively toughen the cement-based materials, the dosage of the organic polymer must reach the percolation threshold to ensure that the toughening phase has a large enough distribution density. The density and mechanical properties of the organic polymer are greatly different from those of the cement-based material. Under a large dosage, the organic polymer is easy to aggregate to form aggregates, which is difficult to disperse uniformly in the cement-based material matrix. Not only can it not effectively improve the brittleness of the cement-based material, but also the organic polymer aggregates will become initial defects of the microstructure, which will further lead to the decrease of the strength of the cement-based material and easily expand into macro cracks under external force.

[0004] In addition, by mixing the organic monomer with the freshly mixed cement-based material, the polymerization process of the organic monomer is synchronized with the hydration process of the cement-based material, so as to form an interpenetrating double network microstructure, so that the polymer formed by polymerization is uniformly distributed in the hardened cement-based material, which can also reduce the cracking of the cement-based material caused by self-shrinkage. However, the in-situ polymerization process of the organic monomer will inhibit the hydration of the cement-based material, and the large amount of introduction of the organic monomer will also cause the significant reduction of the compressive strength of the cement-based material.

[0005] As can be seen from the above, the existing toughening methods of cement-based materials all have obvious defects and cannot completely meet the requirements of actual application.

[0006] Therefore, it is of great significance to develop a toughening modified material with excellent performance suitable for cement-based materials. SUMMARY

[0007] The purpose of the present application is to provide a hydrogel particle and a preparation method and application thereof.

[0008] The technical scheme adopted by the present application is as follows:

[0009] A hydrogel particle having a core-shell structure, the inner core is a micron-sized inorganic particle, and the outer shell is a hydrogel.

[0010] Preferably, the micrometer-sized inorganic particles are at least one of micrometer-sized basalt particles, micrometer-sized carbon black particles, micrometer-sized zeolite particles, micrometer-sized limestone particles.

[0011] Preferably, the micrometer-sized inorganic particles have an average particle size of 3 μm to 20 μm.

[0012] Preferably, the hydrogel is at least one of polyacrylamide hydrogel, sodium polyacrylate hydrogel, polyethylene glycol hydrogel.

[0013] Preferably, the hydrogel particles have a particle size of 20 μm to 60 μm.

[0014] Preferably, the hydrogel particles have a dandelion ball-like structure, and are specifically composed of micrometer-sized inorganic particles and a plurality of hydrogel polymer chains attached to the surface of the micrometer-sized inorganic particles by charge adsorption.

[0015] A method for preparing the hydrogel particles as described above comprises the following steps: mixing a micrometer-sized inorganic particle dispersion, a hydrogel precursor aqueous solution and an initiator aqueous solution, then performing a cross-linking reaction, and then performing drying and pulverization, to obtain the hydrogel particles.

[0016] Preferably, the micrometer-sized inorganic particle dispersion, the hydrogel precursor aqueous solution and the initiator aqueous solution are used in a ratio of 1:0.25-4:0.0025-0.04.

[0017] Further preferably, the micrometer-sized inorganic particle dispersion, the hydrogel precursor aqueous solution and the initiator aqueous solution are used in a ratio of 1:0.9-1.1:0.009-0.011.

[0018] Preferably, a dispersant is added to the micrometer-sized inorganic particle dispersion.

[0019] Preferably, the dispersant is at least one of cellulose ether, sodium carbonate and sodium hexametaphosphate.

[0020] Preferably, the dispersant is added in an amount of 0.3% to 3% by weight of the micrometer-sized inorganic particles.

[0021] Preferably, the concentration of the micrometer-sized inorganic particle dispersion is 15 g / L to 20 g / L.

[0022] Preferably, the concentration of the hydrogel precursor aqueous solution is 1.5 mol / L to 2.5 mol / L.

[0023] Preferably, the initiator in the initiator aqueous solution is at least one of potassium persulfate, ammonium persulfate, ferrous sulfate and sodium bisulfite.

[0024] Preferably, the concentration of the initiator aqueous solution is 0.005-0.01 mol / L.

[0025] Preferably, the cross-linking reaction is carried out at a temperature of 40-80°C for 0.5-4 hours.

[0026] Preferably, the drying method is one of air drying, vacuum drying, and freeze drying.

[0027] A cement-based material comprising the hydrogel particles described above.

[0028] Preferably, the amount of the hydrogel particles is 0.3-3% by weight of the cement in the cement-based material.

[0029] The working principle of the hydrogel particles of the present application is as follows: the hydrogel particles of the present application have a dandelion fluff ball-like structure and a floating feature, which are composed of micron-sized inorganic particles and a number of hydrogel polymer chains attached to the surface of the micron-sized inorganic particles by charge adsorption. The specific surface area of the micron-sized inorganic particles is much smaller than that of nanoparticles, and the bonding strength of the micron-sized inorganic particles with the hydrogel polymer chains is relatively weak. Under the action of a large number of cations in the pore solution of the cement-based material, the hydrogel polymer chains are prone to ion shielding effect, which promotes the shedding of part of the hydrogel polymer chains, similar to the shedding process of dandelion seeds. During the mixing process of the cement-based material, the shedded hydrogel polymer chains are dispersed again, the overall distribution uniformity of the hydrogel polymer chains is improved, and finally the toughness and crack resistance of the cement-based material can be significantly improved.

[0030] The hydrogel particles of the present application have the advantages of good compatibility, good distribution uniformity, and no influence on cement hydration when used in cement-based materials, and can significantly improve the toughness and crack resistance of the cement-based material, thereby improving the durability of the cement-based material, prolonging its service life, and being suitable for large-scale popularization and application.

[0031] Specifically:

[0032] 1) The micron-sized inorganic particles are introduced into the hydrogel particles of the present application, which improves the compatibility of the hydrogel particles with the cement-based material and reduces the risk of polymer agglomeration;

[0033] 2) The micron-sized inorganic particles are introduced into the hydrogel particles of the present application, and their relatively weak physical cross-linking ability ensures the detachment and redistribution of the hydrogel polymer chains under the action of counterion shielding, thereby improving the distribution uniformity of the polymers;

[0034] 3) The polymerization and cross-linking process of the hydrogel in the hydrogel particles of the present application has been completed before the introduction of the cement-based material, which does not affect the hydration of the cement and reduces the influence on the strength of the cement-based material.

[0035] 4) The hydrogel particles of the present application significantly reduce the autogenous shrinkage of cement-based materials, prolong the initial cracking time, improve the crack resistance of cement-based materials, and reduce the environmental load of cement-based materials during the life cycle, while ensuring the strength of cement-based materials. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 A schematic diagram of the microstructure of the hydrogel particles of the present application. DETAILED DESCRIPTION

[0037] The present application will be further explained and described with reference to specific examples.

[0038] Example 1:

[0039] A hydrogel particle is prepared as follows:

[0040] 1) Lime stone particles with an average particle size of 16 μm and sodium hexametaphosphate are stirred and dispersed in water, the addition amount of sodium hexametaphosphate is 1.2% of the weight of the lime stone particles, to obtain a micron-sized lime stone particle suspension with a concentration of 15 g / L (the sedimentation rate after standing for 6 h is 3.5%);

[0041] 2) 50 mL of the micron-sized lime stone particle suspension, 50 mL of an acrylamide aqueous solution with a concentration of 2 mol / L, and 0.5 mL of an ammonium persulfate aqueous solution with a concentration of 0.01 mol / L are mixed and stirred uniformly, then after stopping stirring, the reaction is carried out at a temperature of 55℃ for 2 h, followed by freeze-drying to constant weight, and then the obtained solid product is ground to a particle size of 25 μm, to obtain the hydrogel particles (a schematic diagram of the microstructure is shown in Figure 1 ).

[0042] Performance test:

[0043] Cement mortar is prepared according to the water-binder ratio (mass ratio) 0.5:1 and the binder-sand ratio (mass ratio of cement to standard sand) 3:1, then the hydrogel particles of the present example are added to the cement mortar at an addition ratio of 0.8% (based on the mass of cement) and stirred uniformly (cement mortar without the addition of hydrogel particles is used as a reference), and it is found that after the addition of the hydrogel particles, the flexural strength of the cement mortar is increased by 23%, the initial cracking time is prolonged by 72%, and the cracking area is reduced by 75%.

[0044] Note:

[0045] The stirring, molding, demolding, curing, and flexural strength test of the cement mortar are carried out in accordance with "GB / T 17671-2021 Cement Mortar Strength Test Method".

[0046] The initial cracking time is tested by the elliptical ring constraint cracking method. The specific process is as follows: in an elliptical mold with a length of 335 mm, an inner diameter of 185 mm, and a height of 35 mm, a stainless steel ellipse with a length of 300 mm, an inner diameter of 150 mm, and a height of 35 mm is fixed at the center, the uniformly stirred cement mortar is poured into the gap between the mold and the stainless steel ellipse, the surface is scraped flat, and then the mold is removed according to the "GB / T 17671-2021 Cement Mortar Strength Test Method", and then the test piece is placed in an environment with a temperature of 20℃±1℃ and a relative humidity of 60%±2%, and the time of the first crack (recorded as the initial cracking time) is observed.

[0047] The cracking area is tested by the flat plate constraint cracking method. The specific process is as follows: 9 Φ40mm*30mm cylinders are uniformly arranged in a 400mm(long)*400mm(wide)*30mm(high) stainless steel mold, the mold is uniformly filled with cement mortar, the surface is scraped flat, and then the test piece is placed in an environment with a temperature of 20℃±1℃ and a relative humidity of 60%±2% for 10 days, the surface cracking picture is obtained, and the crack area ratio (recorded as the cracking area) is calculated by image processing.

[0048] Example 2:

[0049] A hydrogel particle is prepared by the following method:

[0050] 1) Basalt particles with an average particle size of 7μm and sodium carbonate are stirred and dispersed in water, the addition amount of sodium carbonate is 2.2% of the weight of basalt particles, and a micron-sized basalt particle suspension with a concentration of 20g / L is obtained (the sedimentation rate after standing for 6h is 2.7%);

[0051] 2) 100mL of micron-sized basalt particle suspension, 100mL of 2mol / L ethylene glycol aqueous solution, and 1mL of 0.005mol / L potassium persulfate aqueous solution are mixed and stirred uniformly, then the stirring is stopped, and the reaction is carried out at a temperature of 65℃ for 3h, then vacuum drying is carried out to constant weight, and then the obtained solid product is pulverized to a particle size of 22μm, that is, a hydrogel particle (the microstructure schematic diagram is shown in Figure 1 ).

[0052] Performance test (test method same as example 1):

[0053] Cement mortar was prepared according to water-binder ratio (mass ratio) 0.4:1 and binder-sand ratio (mass ratio of cement to standard sand) 3:1, and then the hydrogel particles of the present example were added into the cement mortar at an addition ratio of 1.5% (based on the mass of cement) and stirred uniformly (cement mortar without the addition of hydrogel particles was used as a reference). It was found that, after the addition of the hydrogel particles, the flexural strength of the cement mortar was increased by 26%, the initial cracking time was prolonged by 84%, and the cracking area was decreased by 78%.

[0054] Example 3

[0055] A hydrogel particle was prepared by the following method:

[0056] 1) Limestone particles with an average particle size of 10 μm and sodium hexametaphosphate were stirred and dispersed in water. The amount of sodium hexametaphosphate added was 1.2% of the weight of the limestone particles, and a micron-sized limestone particle suspension with a concentration of 15 g / L was obtained (the sedimentation rate after standing for 6 h was 3.8%);

[0057] 2) 120 mL of the micron-sized limestone particle suspension, 120 mL of a sodium acrylate aqueous solution with a concentration of 2 mol / L, and 1.2 mL of an ammonium persulfate aqueous solution with a concentration of 0.01 mol / L were mixed and stirred uniformly, and then the stirring was stopped and the mixture was allowed to react at a temperature of 60°C for 2 h. The solid product obtained was freeze-dried to constant weight, and then ground to a particle size of 30 μm to obtain the hydrogel particles (a schematic diagram of the microstructure is shown in Figure 1

[0058] Performance test (test method same as Example 1):

[0059] Cement mortar was prepared according to water-binder ratio (mass ratio) 0.4:1 and binder-sand ratio (mass ratio of cement to standard sand) 3:1, and then the hydrogel particles of the present example were added into the cement mortar at an addition ratio of 2.0% (based on the mass of cement) and stirred uniformly (cement mortar without the addition of hydrogel particles was used as a reference). It was found that, after the addition of the hydrogel particles, the flexural strength of the cement mortar was increased by 25%, the initial cracking time was prolonged by 81%, and the cracking area was decreased by 77%.

[0060] Example 4

[0061] A hydrogel particle was prepared by the following method:

[0062] 1) Basalt particles with an average particle size of 8 μm and sodium carbonate were stirred and dispersed in water. The amount of sodium carbonate added was 2.2% of the weight of the basalt particles, and a micron-sized basalt particle suspension with a concentration of 20 g / L was obtained (the sedimentation rate after standing for 6 h was 4.0%);

[0063] ​2) 150 mL of micron-sized basalt particle suspension, 150 mL of 2 mol / L sodium acrylate aqueous solution and 1.5 mL of 0.005 mol / L potassium persulfate aqueous solution were mixed and stirred uniformly, then after stopping stirring, the reaction was carried out at 50°C for 4 h, vacuum drying was carried out until constant weight, and then the obtained solid product was ground to a particle size of 27 μm, thus obtaining the hydrogel particles (the schematic diagram of the microstructure is shown in Figure 1

[0064] Performance test (the test method is the same as that in Example 1):

[0065] Cement mortar was prepared according to a water-binder ratio (mass ratio) of 0.5:1 and a binder-sand ratio (mass ratio of cement to standard sand) of 3:1, then the hydrogel particles of the present example were added into the cement mortar at an addition ratio of 1.8% (based on the mass of cement) and stirred uniformly (cement mortar without the addition of hydrogel particles was used as a reference), and it was found that after the addition of the hydrogel particles, the flexural strength of the cement mortar was increased by 21%, the initial cracking time was prolonged by 68%, and the cracking area was decreased by 71%.

[0066] Example 5:

[0067] A hydrogel particle was prepared by the following method:

[0068] 1) Limestone particles with an average particle size of 16 μm and cellulose ether were stirred and dispersed in water, the addition amount of cellulose ether was 1.5% of the weight of limestone particles, thus obtaining a micron-sized limestone particle suspension with a concentration of 15 g / L (the sedimentation rate after standing for 6 h was 2.3%);

[0069] 2) 200 mL of micron-sized limestone particle suspension, 200 mL of 2 mol / L acrylamide aqueous solution and 2 mL of 0.01 mol / L ammonium persulfate aqueous solution were mixed and stirred uniformly, then after stopping stirring, the reaction was carried out at 70°C for 1.5 h, vacuum drying was carried out until constant weight, and then the obtained solid product was ground to a particle size of 32 μm, thus obtaining the hydrogel particles (the schematic diagram of the microstructure is shown in Figure 1

[0070] Performance test (the test method is the same as that in Example 1):

[0071] ​​The cement mortar is prepared according to a water-binder ratio (mass ratio) of 0.35:1 and a binder-sand ratio (mass ratio of cement to standard sand) of 3:1, the hydrogel particles of the present example are then added into the cement mortar at an addition ratio of 2.2% (based on the mass of cement) and stirred uniformly (a cement mortar without the addition of hydrogel particles is used as a reference), and it is found that the flexural strength of the cement mortar after the addition of the hydrogel particles is increased by 31%, the initial cracking time is prolonged by 86%, and the cracking area is decreased by 81%.

[0072] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above examples, and any changes, modifications, substitutions, combinations, simplifications, etc. made without departing from the spirit and principles of the present application shall be equivalent replacement manners and shall be included in the protection scope of the present application.

Claims

1. A hydrogel particle, characterized in that, The product has a core-shell structure, with a core of micron-sized inorganic particles and a shell of hydrogel. The micron-sized inorganic particles are at least one of micron-sized basalt particles, micron-sized carbon black particles, micron-sized zeolite particles, and micron-sized limestone particles. The hydrogel is at least one of polyacrylamide hydrogel, sodium polyacrylate hydrogel, and polyethylene glycol hydrogel. The hydrogel particles have a structure and dispersion characteristics similar to dandelion fluff balls, consisting of micron-sized inorganic particles and several hydrogel polymer chains attached to the surface of the micron-sized inorganic particles through charge adsorption. The hydrogel particles are prepared by a method including the following steps: mixing a micron-sized inorganic particle dispersion, an aqueous solution of a hydrogel precursor, and an aqueous solution of an initiator, then performing a crosslinking reaction, followed by drying and grinding to obtain the hydrogel particles.

2. The hydrogel particles according to claim 1, characterized in that: The average particle size of the micron-sized inorganic particles is 3 μm to 20 μm.

3. The hydrogel particles according to claim 1, characterized in that: The hydrogel particles have a particle size of 20 μm to 60 μm.

4. The hydrogel particles according to claim 1, characterized in that: The dispersion of the micron-sized inorganic particles contains a dispersant; the dispersant is at least one of cellulose ether, sodium carbonate, and sodium hexametaphosphate; the amount of the dispersant added is 0.3% to 3% of the weight of the micron-sized inorganic particles.

5. The hydrogel particles according to claim 1 or 4, characterized in that: The initiator in the aqueous initiator solution is at least one of potassium persulfate, ammonium persulfate, ferrous sulfate, and sodium bisulfite.

6. The hydrogel particles according to claim 1 or 4, characterized in that: The crosslinking reaction is carried out at a temperature of 40℃ to 80℃ for a reaction time of 0.5h to 4h.

7. A cement-based material, characterized in that, It comprises the hydrogel particles described in any one of claims 1 to 6.

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