A high-strength water-absorbing resin microcapsule and its preparation method and application

Abstract

The present invention provides a high-strength water-absorbing resin microcapsule. The microcapsule core is a high-strength water-absorbing resin, and the capsule wall is coated with chitosan. This prevents the microcapsule from absorbing water during cement hydration, thus maintaining its performance. When cracks or defects appear in the cement material, the high-strength water-absorbing resin is released. Due to its water-absorbing properties, the water-absorbing resin rapidly absorbs water and expands upon contact with water, plugging the cracks and thus achieving a self-healing effect for the cement. The water-absorbing resin material is formed by adding inorganic compounds and simultaneously cross-linking and copolymerizing polyhydroxy polymers, polyacrylamide, and acrylic acid to form an interpenetrating network structure. The inorganic materials are present in the interpenetrating network hydrogel to form a unique organic / inorganic network structure, significantly improving the strength and elasticity of the water-absorbing resin and enhancing its sealing effect.

Description

Technical Field

[0001] The invention belongs to the field of water-absorbing resin materials, and particularly relates to a high-strength water-absorbing resin microcapsule and a preparation method and application thereof. Background Art

[0002] Water-absorbent resin is a functional polymer material capable of absorbing and retaining hundreds or even thousands of times its own weight in water. Its advantages include rapid water absorption, high water absorption capacity, and strong water retention. Water-absorbent resin is widely used in gardening, healthcare, agriculture and forestry, construction materials, aquaculture, cosmetics, desertification control, soil moisture retention, and wetland protection. It can also be used as a leak-proof material in industry.

[0003] Cement-based materials are among the most widely used materials in the world. However, due to their brittle nature, cement inevitably develops tiny cracks and localized damage during use due to the complex external environment. These cracks can cause water seepage, reducing service life, or even endanger the safety of the entire structure. Traditional crack repairs and other external leak-proofing measures alone are not only difficult to pinpoint, but also require long cycles, are expensive, and offer limited effectiveness. Therefore, self-healing cement technology, with its unique advantages, has become a highly promising repair method, particularly for infrastructure requiring high sustainability standards and difficult to implement with traditional repair methods. Self-healing cement-based materials are intelligent materials capable of self-repair. When microcracks develop within the cement-based material, specialized components pre-incorporated into the matrix release repair materials in response to various damaging forces, repairing and preventing further crack expansion. Summary of the Invention

[0004] To address the shortcomings of the existing technology, the present invention provides a high-strength water-absorbing resin microcapsule. The microcapsule core is a high-strength water-absorbing resin, and the capsule wall is a chitosan coating. This prevents the microcapsule from absorbing water during the cement hydration process, thereby maintaining the performance of the cement. When cracks or defects appear in the cement material, the capsule wall is also destroyed by external force, releasing the high-strength water-absorbing resin. Due to the water-absorbing properties of the water-absorbing resin, it rapidly absorbs water and expands when exposed to water, plugging the cracks, thereby achieving the self-healing effect of cement when exposed to water. The water-absorbing resin material is formed by adding inorganic compounds and simultaneously cross-linking and copolymerizing polyhydroxy polymers, polyacrylamide, and acrylic acid to form an interpenetrating network structure. The inorganic compounds are present in the interpenetrating network hydrogel to form a unique organic / inorganic network structure, which significantly improves the strength and elasticity of the water-absorbing resin. At the same time, the loose network structure improves the water absorption capacity of the water-absorbing resin and enhances the plugging effect.

[0005] One of the purposes of the present invention is to provide a high-strength water-absorbing resin microcapsule, comprising a capsule core and a capsule wall wrapping the capsule core, wherein the capsule core is a high-strength water-absorbing resin and the capsule wall is a chitosan coating.

[0006] In the high-strength water-absorbing resin microcapsules, the particle size of the microcapsules is 100 to 1000 microns, preferably 180 to 600 microns; the thickness of the capsule wall is 10 to 100 microns, preferably 20 to 80 microns.

[0007] In the above-mentioned microcapsules, the chitosan coating is prepared from components including an acidic compound, chitosan, and an aldehyde compound; the acidic compound is selected from inorganic acids and / or organic acids, preferably at least one selected from hydrochloric acid, sulfuric acid, nitric acid, and acetic acid, more preferably acetic acid; the aldehyde compound is selected from at least one selected from glyoxal, glutaraldehyde, and terephthalaldehyde, preferably glutaraldehyde;

[0008] The high-strength water-absorbing resin is obtained by reacting components including acrylamide monomers, optional acrylic acid monomers, polyhydroxy polymers, and inorganic compounds; wherein the acrylamide monomers are selected from at least one of acrylamide and N,N-dimethylacrylamide, preferably acrylamide; the acrylic acid monomers are selected from at least one of acrylic acid and methacrylic acid, preferably acrylic acid; the polyhydroxy polymers are selected from at least one of polyethylene glycol and polyvinyl alcohol, preferably polyvinyl alcohol; and the inorganic compound is selected from at least one of bentonite, silicon dioxide, titanium dioxide, montmorillonite, kaolin, and calcium carbonate;

[0009] In the high-strength water-absorbing resin, based on the total weight of the acrylamide monomer and the acrylic acid monomer as 100 parts by weight, the amount of the acrylamide monomer is 5 to 100 parts, the amount of the acrylic acid monomer is 0 to 95 parts, the amount of the polyhydroxy polymer is 1 to 30 parts, and the amount of the inorganic compound is 1 to 20 parts; preferably, based on the total weight of the acrylamide monomer and the acrylic acid monomer as 100 parts by weight, the amount of the acrylamide monomer is 10 to 90 parts, the amount of the acrylic acid monomer is 10 to 90 parts, the amount of the polyhydroxy polymer is 2 to 20 parts, and the amount of the inorganic compound is 1 to 15 parts.

[0010] A second object of the present invention is to provide a method for preparing the aforementioned high-strength water-absorbent resin microcapsules, comprising spraying a coating solution containing chitosan onto the high-strength water-absorbent resin, followed by drying to obtain the high-strength water-absorbent resin microcapsules. Specifically, the high-strength water-absorbent resin is placed in the drum of a spray coating apparatus. In coating mode, a pump is used to spray the chitosan coating solution through the spray nozzle of the spray drying apparatus onto the rolling high-strength water-absorbent resin particles. After drying, natural cooling, and air-drying, the cement-based self-healing microcapsules are obtained.

[0011] In the above preparation method, the chitosan coating solution includes components including a blended acidic compound, chitosan, an aldehyde compound, and water; the acidic compound is selected from an inorganic acid and / or an organic acid, preferably selected from at least one of hydrochloric acid, sulfuric acid, nitric acid, and acetic acid, more preferably selected from acetic acid; the aldehyde compound is selected from at least one of glyoxal, glutaraldehyde, and terephthalaldehyde, preferably selected from glutaraldehyde; based on 100 parts by weight of the chitosan coating solution, the chitosan coating solution comprises 1 to 5 parts of the acidic compound, 0.5 to 5 parts of chitosan, 0.02 to 2.5 parts of the aldehyde compound, and the remainder is water. The acidic compound in the chitosan coating solution promotes the solubility of chitosan in water, and the aldehyde compound promotes the formation of chitosan polymers, making the chitosan coating formed after spraying more uniform and more stable in structure.

[0012] In the above preparation method, the mass ratio of the high-strength water-absorbing resin to the chitosan coating liquid is 1:0.5 to 1:10, preferably 1:1 to 1:5;

[0013] The spraying conditions are 60-150° C. and 10-60 min; preferably, the spraying conditions are 80-100° C. and 20-30 min.

[0014] In the above preparation method, the chitosan coating solution is prepared by dissolving an acidic compound in water, dissolving chitosan in the acidic aqueous solution, and adding an aldehyde compound to obtain the chitosan coating solution.

[0015] In the above preparation method, the preparation method of the high-strength water-absorbing resin comprises the following steps:

[0016] Step (1) adding a polyhydroxy polymer into water and dissolving the polyhydroxy polymer to obtain a uniform polyhydroxy polymer solution;

[0017] Step (2) adding acrylic acid monomers into an alkaline solution for neutralization to form an acrylic acid monomer solution;

[0018] Step (3) adding acrylamide monomer, N,N-methylenebisacrylamide, inorganic compound, and acrylic acid monomer solution obtained in step (2) to the polyhydroxy polymer solution obtained in step (1), and stirring to obtain a mixed solution;

[0019] Step (4) adding an initiator and a cross-linking agent to the mixed solution obtained in step (3), heating for reaction, and drying to obtain the high-strength water-absorbing resin.

[0020] In the preparation method of the high-strength water-absorbing resin, based on the total weight of the acrylamide monomer and the acrylic acid monomer as 100 parts by weight, the amount of the acrylamide monomer is 5 to 100 parts, the amount of the acrylic acid monomer is 0 to 95 parts, the amount of the polyhydroxy polymer is 1 to 30 parts, the amount of the inorganic compound is 1 to 20 parts, the amount of the N,N-methylenebisacrylamide is 0.1 to 1 part, the amount of the crosslinking agent is 1 to 5 parts, and the amount of the initiator is 0. 1 to 2 parts; preferably, based on 100 parts by weight of the total weight of the acrylamide monomer and the acrylic acid monomer, the amount of the acrylamide monomer is 10 to 90 parts, the amount of the acrylic acid monomer is 10 to 90 parts, the amount of the polyhydroxy polymer is 2 to 20 parts, the amount of the inorganic compound is 1 to 15 parts, the amount of the N,N-methylenebisacrylamide is 0.2 to 0.6 parts, the amount of the crosslinking agent is 2 to 4 parts, and the amount of the initiator is 0.3 to 1 part;

[0021] The acrylamide monomer is selected from at least one of acrylamide and N,N-dimethylacrylamide, preferably acrylamide;

[0022] The acrylic monomer is selected from at least one of acrylic acid and methacrylic acid, preferably acrylic acid;

[0023] The polyhydroxy polymer is selected from at least one of polyethylene glycol and polyvinyl alcohol, preferably polyvinyl alcohol;

[0024] The inorganic compound is selected from at least one of bentonite, silicon dioxide, titanium dioxide, montmorillonite, kaolin and calcium carbonate;

[0025] The cross-linking agent is selected from aldehyde compounds, preferably at least one selected from glutaraldehyde, glyoxal, terephthalaldehyde, and formaldehyde;

[0026] The initiator is selected from at least one of peroxide initiators, azo initiators, and redox initiators, and is preferably selected from potassium persulfate and sodium bisulfite.

[0027] In the above-mentioned method for preparing high-strength water-absorbing resin, the concentration of the polyhydroxy polymer solution obtained in step (1) is 0.1 to 10%, preferably 1 to 5%;

[0028] In the step (2), the concentration of the alkaline solution is 1-20%, preferably 5-10%; the alkaline solution is selected from at least one of sodium hydroxide solution, sodium carbonate solution, and sodium bicarbonate solution, preferably sodium hydroxide solution; the degree of neutralization is 30-80%, preferably 40-60%;

[0029] In step (4), before adding the initiator and the cross-linking agent, an inert gas is first introduced to replace the air in the reaction system, and the initiator and the cross-linking agent are added under the inert gas atmosphere;

[0030] The reaction temperature in step (4) is 30-60°C. After the viscosity of the reaction system increases, stirring is stopped and the reaction is continued for 2-6 hours. The product obtained after the reaction is cut, dried, and then crushed to obtain a granular high-strength water-absorbing resin. The drying temperature is 80-100°C. The particle size of the obtained high-strength water-absorbing resin is 100-1000 microns, preferably 180-600 microns. Microcapsules prepared from water-absorbing resin of appropriate particle size are added to cement without affecting the strength of the cement. When cracks or defects appear in the cement, the microcapsules rupture, releasing the water-absorbing resin, which expands in water to achieve a repair effect.

[0031] The third object of the present invention is to provide a self-repairing cement-based material, comprising the above-mentioned high-strength water-absorbing resin microcapsules or the high-strength water-absorbing resin microcapsules obtained by the above-mentioned preparation method, wherein the amount of the high-strength water-absorbing resin microcapsules is 0.5-5% of the mass of the cement, preferably 1-3%.

[0032] A fourth object of the present invention is to provide a method for preparing the aforementioned self-healing cement-based material, comprising adding the aforementioned high-strength water-absorbing resin microcapsules to cement slurry, mixing, and then curing at 70-80°C to obtain the aforementioned self-healing cement-based material. The aforementioned curing process can be performed using conventional curing methods in the art, such as vibrating on a cement mortar compaction table, curing in a standard curing room at 70-80°C for one day, removing the mold, and continuing curing in a water bath at 70-80°C to obtain the self-healing cement-based material.

[0033] The present invention, when preparing a high-strength water-absorbent resin, adds an inorganic compound and simultaneously uses a polyhydroxy polymer, an acrylamide monomer, and an acrylic acid monomer to form an interpenetrating network structure by cross-linking and copolymerizing. The inorganic compound is present in the interpenetrating network hydrogel to form a unique organic / inorganic network structure, which can greatly improve the strength and elasticity of the water-absorbent resin. After absorbing water, the water-absorbent resin forms a gel with a certain elasticity, which can be used to repair pores of various shapes. In addition, the present invention uses chitosan coating as the capsule wall of the microcapsule, which can promote the compatibility of the high-strength water-absorbent resin with the cement material after encapsulation, and on the other hand, it can effectively inhibit the high-strength water-absorbent resin from absorbing water during the cement hydration process, which reduces the performance of the cement. When the cement-based material containing the high-strength water-absorbent resin microcapsule of the present invention encounters defects such as cracks, the capsule wall of the high-strength water-absorbent resin microcapsule is also destroyed under the action of external force, so that the high-strength water-absorbent resin in the microcapsule meets water and absorbs the infiltrated water and expands, thereby repairing and preventing the cracks from further expanding, and better achieving the self-repairing effect of cement when it encounters water. DETAILED DESCRIPTION

[0034] The present invention will be described in detail below with reference to specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art to the present invention based on the contents of the present invention still fall within the scope of protection of the present invention.

[0035] The test instruments and test conditions used in the examples are as follows:

[0036] Water absorption test method:

[0037] Moisten the tea bag with water first and weigh its mass. Put 0.1g of resin into the tea bag and then immerse it in water. Take it out after a certain period of time and drain it with a filter. Use a balance to weigh the total mass of the tea bag and resin, and calculate the water absorption rate using formula (1-1).

[0038]

[0039] Wherein, Q is the water absorption rate of the resin; W t is the total weight of the tea bag and resin after absorbing water; W0 is the mass of the tea bag; W1 is the mass of the resin.

[0040] The fluidity of cement mortar is determined according to GB / T 2419-2005 "Method for determination of fluidity of cement mortar". Cement slurry is prepared according to GB / T19139-2003 and the compressive strength of cement slurry is tested.

[0041] Particle size test method: Particle size was measured using a scanning electron microscope.

[0042] The raw materials and sources used in the examples are as follows:

[0043] The raw materials in the examples are all commercially available commodities.

[0044] Example 1 Preparation of high-strength water-absorbent resin microcapsules

[0045] 15 parts of polyvinyl alcohol were dissolved in 300 parts of distilled water in a reactor. 90 parts of acrylamide, acrylic acid (10 parts of acrylic acid was added to a 10% sodium hydroxide solution to obtain a 50% neutralized acrylic acid solution), 0.4 parts of N,N-methylenebisacrylamide, and 100 parts of a 10% bentonite dispersion were then added and stirred uniformly. After nitrogen was passed through for 30 minutes to deoxygenate, 0.8 parts of potassium persulfate, 0.2 parts of sodium bisulfite, and 3 parts of glutaraldehyde were added in a nitrogen atmosphere. The temperature was adjusted to 60° C., and stirring was stopped after the viscosity increased. The polymerization reaction was continued for 5 hours. After the reaction, the resulting reactants were cut, granulated, dried at 100° C., and then crushed and sieved to obtain a granular high-strength water-absorbent resin (denoted as 1#). The particle size of the obtained high-strength water-absorbent resin was 180 to 600 μm.

[0046] Add 10 parts of acetic acid and 390 parts of water into a beaker, stir evenly, then add 4 parts of chitosan, and after complete dissolution, add 0.4 parts of glutaraldehyde to prepare a chitosan coating solution.

[0047] 100 parts of water-absorbent resin microparticles were placed in the drum of a spray coating machine. In coating mode, a pump was used to spray 400 parts of chitosan coating solution through the machine's spray nozzle onto the rolling water-absorbent resin microparticles. The particles were tumble-dried at 100°C under ventilation for 20 minutes, then naturally cooled and air-dried to produce high-strength water-absorbent resin microcapsules (designated #2). The resulting cement-based self-healing microcapsules had a particle size of 200 to 680 microns and a capsule wall thickness of 20 to 80 microns.

[0048] Example 2 Preparation of high-strength water-absorbent resin microcapsules

[0049] 10 parts of polyvinyl alcohol were dissolved in 300 parts of distilled water in a reactor. 50 parts of acrylamide, acrylic acid (50 parts of acrylic acid was added to a 10% sodium hydroxide solution to obtain a 50% neutralized acrylic acid solution), 0.4 parts of N,N-methylenebisacrylamide, and 100 parts of a 10% silica dispersion were then added and stirred uniformly. After nitrogen was passed through for 30 minutes to remove oxygen, 0.8 parts of potassium persulfate, 0.2 parts of sodium bisulfite, and 3 parts of glutaraldehyde were added under a nitrogen atmosphere. The temperature was adjusted to 60° C., and stirring was stopped after the viscosity increased. The polymerization reaction was continued for 5 hours. After the reaction, the resulting reactant was cut, granulated, dried at 100° C., and then crushed and sieved to obtain a granular water-absorbent resin (denoted as 3#). The particle size of the obtained high-strength water-absorbent resin was 180 to 600 μm.

[0050] Add 10 parts of acetic acid and 390 parts of water into a beaker, stir evenly, then add 4 parts of chitosan, and after complete dissolution, add 0.4 parts of glutaraldehyde to prepare a chitosan coating solution.

[0051] 100 parts of water-absorbing resin microparticles were placed in the drum of a spray coating machine. In coating mode, a pump was used to spray 400 parts of chitosan coating solution through the machine's spray nozzle onto the rolling water-absorbing resin microparticles. The particles were tumble-dried at 100°C under ventilation for 20 minutes, then naturally cooled and air-dried to obtain microcapsules (designated 4#). The resulting cement-based self-healing microcapsules had a particle size of 200 to 680 microns and a capsule wall thickness of 20 to 80 microns.

[0052] Example 3 Preparation of high-strength water-absorbent resin capsules

[0053] 15 parts of polyvinyl alcohol were dissolved in 300 parts of distilled water in a reactor. 90 parts of acrylamide, acrylic acid (10 parts of acrylic acid was added to a 10% sodium hydroxide solution to obtain a 50% neutralized acrylic acid solution), 0.4 parts of N,N-methylenebisacrylamide, and 100 parts of a 10% calcium carbonate dispersion were then added and stirred uniformly. After nitrogen was passed through for 30 minutes to remove oxygen, 0.8 parts of potassium persulfate, 0.2 parts of sodium bisulfite, and 3 parts of glutaraldehyde were added in a nitrogen atmosphere. The temperature was adjusted to 60° C., and stirring was stopped after the viscosity increased. The polymerization reaction was continued for 5 hours. After the reaction, the resulting reactants were cut, granulated, dried at 100° C., and then crushed and sieved to obtain a granular water-absorbent resin (denoted as 5#). The particle size of the obtained high-strength water-absorbent resin was 180 to 600 μm.

[0054] Add 10 parts of acetic acid and 390 parts of water into a beaker, stir evenly, then add 6 parts of chitosan, and after it is completely dissolved, add 0.6 parts of glutaraldehyde to prepare a chitosan coating solution.

[0055] 100 parts of water-absorbing resin microparticles were placed in the drum of a spray coating machine. In coating mode, a pump was used to spray 400 parts of chitosan coating solution through the machine's spray nozzle onto the rolling water-absorbing resin microparticles. The particles were tumble-dried at 100°C under ventilation for 20 minutes, then naturally cooled and air-dried to obtain microcapsules (designated #6). The resulting cement-based self-healing microcapsules had a particle size of 200 to 680 microns and a capsule wall thickness of 20 to 80 microns.

[0056] Example 4 Preparation of high-strength water-absorbent resin capsules

[0057] 15 parts of polyvinyl alcohol were dissolved in 400 parts of distilled water in a reactor. 10 parts of acrylamide, acrylic acid (90 parts of acrylic acid were added to a 10% sodium hydroxide solution to obtain a 50% neutralized acrylic acid solution), 0.4 parts of N,N-methylenebisacrylamide, and 100 parts of a 10% montmorillonite dispersion were then added and stirred uniformly. After nitrogen was passed through the reactor for 30 minutes to remove oxygen, 0.8 parts of potassium persulfate, 0.2 parts of sodium bisulfite, and 3 parts of glutaraldehyde were added under a nitrogen atmosphere. The temperature was adjusted to 60° C., and stirring was stopped after the viscosity increased. The polymerization reaction was continued for 5 hours. After the reaction, the resulting reactants were cut and granulated, dried at 100° C., and then crushed and sieved to obtain a granular water-absorbent resin (denoted as 7#). The particle size of the obtained high-strength water-absorbent resin was 180 to 600 μm.

[0058] Add 10 parts of acetic acid and 390 parts of water into a beaker, stir evenly, then add 4 parts of chitosan, and after complete dissolution, add 0.4 parts of glutaraldehyde to prepare a chitosan coating solution.

[0059] 100 parts of water-absorbing resin microparticles were placed in the drum of a spray coating machine. In coating mode, a pump was used to spray 400 parts of chitosan coating solution through the machine's spray nozzle onto the rolling water-absorbing resin microparticles. The particles were tumble-dried at 100°C under ventilation for 20 minutes, then naturally cooled and air-dried to obtain microcapsules (designated #8). The resulting cement-based self-healing microcapsules had a particle size of 200 to 680 microns and a capsule wall thickness of 20 to 80 microns.

[0060] Comparative Example 1 Preparation of water-absorbent resin capsules

[0061] 400 parts of distilled water, 90 parts of acrylamide, acrylic acid (10 parts of acrylic acid was added to a 10% sodium hydroxide solution to obtain a 50% neutralized acrylic acid solution), and 0.4 parts of N,N-methylenebisacrylamide were added to a reactor and stirred uniformly. After nitrogen was passed through for 30 minutes to remove oxygen, 0.8 parts of potassium persulfate and 0.2 parts of sodium bisulfite were added in a nitrogen atmosphere. The temperature was adjusted to 60°C. Stirring was stopped after the viscosity increased, and the polymerization reaction was continued for 5 hours. After the reaction, the resulting reactant was cut and granulated, dried at 100°C, and then crushed and sieved to obtain a granular high-strength water-absorbent resin (denoted as 9#). The particle size of the obtained water-absorbent resin was 180 to 600 microns.

[0062] Add 10 parts of acetic acid and 390 parts of water into a beaker, stir evenly, then add 4 parts of chitosan, and after complete dissolution, add 0.4 parts of glutaraldehyde to prepare a chitosan coating solution.

[0063] 100 parts of water-absorbent resin microparticles were placed in the drum of a spray coating machine. In coating mode, a pump was used to spray 400 parts of chitosan coating solution through the machine's spray nozzle onto the rolling water-absorbent resin microparticles. The particles were tumble-dried at 100°C under ventilation for 20 minutes, then naturally cooled and air-dried to produce high-strength water-absorbent resin microcapsules (designated #10). The resulting cement-based self-healing microcapsules had a particle size of 200 to 680 microns and a capsule wall thickness of 20 to 80 microns.

[0064] The water absorption data of samples 1 to 10# obtained in Examples 1 to 4 and Comparative Example 1 are shown in Table 1.

[0065] Table 1. Water absorption ratio of samples 1# to 10#

[0066] sample Tap water 50,000 ppm NaCl aqueous solution 1% NaOH aqueous solution 1# 22.5 10.2 40.5 2# 3.0 2.0 5.0 3# 20.8 8.9 30.2 4# 4.5 2.0 3.0 5# 23.4 10.5 42.6 6# 2.5 1.5 2.0 7# 25.6 11.6 46.5 8# 1.5 2.0 3.5 9# 91.5 18.6 54.5 10# 2.5 2.0 3.0

[0067] As can be seen from the data in Table 1, the high-strength water-absorbing resins (1#, 3#, 5#, 7#) obtained in Examples 1 to 4 have strong water absorption capacity in tap water, an aqueous solution with a salinity of 50,000, and an alkaline aqueous solution, while the obtained cement-based material self-repairing microcapsules (2#, 4#, 6#, 8#) have very low water absorption rates in tap water, an aqueous solution with a salinity of 50,000, and an alkaline aqueous solution. This indicates that the cement-based material self-repairing capsules of the present invention use chitosan coating liquid as the capsule wall to effectively inhibit the water absorption of the capsule core water-absorbing resin, ensuring that the microcapsules do not absorb water during the cement hydration process and do not affect the performance of the cement. Although the water-absorbent resin of Comparative Example 1 has a higher water absorption rate than the water-absorbent resins of Examples 1 to 4, the excessively high water absorption rate not only fails to seal the gaps but also makes the gaps larger. The high-strength water-absorbent resins of Examples 1 to 4 have a relatively lower water absorption rate than that of Comparative Example 1 because the polyhydroxy polymer, acrylamide monomer, acrylic acid monomer, and inorganic compound are cross-linked and copolymerized to form an interpenetrating network structure. However, the inorganic compound exists in the interpenetrating network hydrogel to form a unique organic / inorganic network structure, which can greatly improve the strength and elasticity of the water-absorbent resin.

[0068] Examples 5-10 Preparation of self-repairing cement-based materials

[0069] The water-absorbing resin microcapsules obtained in Examples 1 to 4 above are used in cement-based materials. The method is as follows: water and cement are mixed in a slurry mixer at a mass ratio of 44:100 and stirred at 360 rpm for 1 minute, then stirred at 1000 rpm for 5 minutes. During the rapid stirring process, the water-absorbing resin microcapsules are added in an amount of 1 to 3% of the mass of the cement. The cement slurry containing the water-absorbing resin microcapsules is then introduced into a mold, vibrated on a cement mortar vibrating table, and placed in a standard curing room at 80°C for curing for 1 day. The mold is then removed and the material is cured in a water bath at 80°C to obtain a self-repairing cement-based material.

[0070] Comparative Example 2

[0071] The water-absorbing resin microcapsules prepared in Comparative Example 1 were added, and other conditions were the same as those in Example 5.

[0072] Comparative Example 3

[0073] Except that the high-strength water-absorbing resin microcapsules of the present invention are not added, other conditions are the same as those in Example 5.

[0074] Table 2. Cement formulations for Examples 5 to 10 and Comparative Examples 2 to 3

[0075]

[0076] The performance tests of the above self-repairing cement-based materials are as follows:

[0077] Table 3. Fluidity and compressive performance tests of self-repairing cement-based materials of Examples 5 to 10 and Comparative Examples 2 to 3

[0078]

[0079] As can be seen from the results in Table 3, the microencapsulation of the high-strength water-absorbing resin particles in Examples 5 to 10 of the present invention can prevent them from contacting the cement slurry, ensuring that they do not absorb water during the cement hydration process, have little effect on the flow properties of the cement, and have a slight effect on the compressive strength of the cement.

[0080] The self-repairing performance of the self-repairing cement-based materials obtained in Examples 5 to 10 for cracks was tested as follows:

[0081] Crack creation: Specimens of the self-healing cementitious material were placed in a press and pressurized at a rate of 0.2 MPa / s. Pressurization was stopped when the maximum pressure was reached and cracks appeared. Permeability was measured using a core flooding flow device (test conditions: flooding pressure: 0.5 MPa, confining pressure: 2.5 MPa) at 0, 3, 14, and 28 days of curing. The permeability test results are listed in Table 4.

[0082] Table 4. Cement-based material self-healing performance test

[0083]

[0084]

[0085] The experimental results shown in Table 4 show that the repair ability of cement paste with water-absorbing resin microcapsules is significantly better than that of cement paste without water-absorbing resin microcapsules. The cement pastes with water-absorbing resin microcapsules added in Examples 5-10 were able to rapidly absorb water and expand after microcracks were generated, significantly reducing the permeability within 3 days. After 14 days, the permeability of the cement paste with microcracks was reduced to less than 10 mD. After the 28-day curing period, the permeability of the cement pastes with water-absorbing resin microcapsules was less than 1 mD, far lower than the permeability of the control sample without water-absorbing resin microcapsules. This demonstrates that the cement paste with water-absorbing resin microcapsules can self-repair microcracks in the cement paste, ensuring the integrity of the cement paste. Furthermore, the self-repair performance is superior to that of the water-absorbing resin capsules in Comparative Example 2, indicating that the water-absorbing resin of the present invention can maintain its sealing effect more persistently in the environment and achieve a better self-repair effect.

Claims

1. A high-strength water-absorbing resin microcapsule comprising a capsule core and a capsule wall surrounding the capsule core, wherein the capsule core is a high-strength water-absorbing resin and the capsule wall is a chitosan coating, wherein a coating solution comprising chitosan is sprayed onto the high-strength water-absorbing resin; the chitosan coating is prepared from components comprising an acidic compound, chitosan, and an aldehyde compound; the high-strength water-absorbing resin is prepared by reacting components comprising an acrylamide monomer, an acrylic acid monomer, a polyhydroxy polymer, N,N-methylenebisacrylamide, and an inorganic compound, with an initiator and a crosslinking agent, wherein the inorganic compound is selected from at least one of bentonite, silicon dioxide, titanium dioxide, montmorillonite, kaolin, and calcium carbonate, and the crosslinking agent is selected from an aldehyde compound; based on 100 parts by weight of the total weight of the acrylamide monomer and the acrylic acid monomer, the amount of the N,N-methylenebisacrylamide is 0.1 to 1 part, and the amount of the crosslinking agent is 1 to 5 parts; The preparation method of the high-strength water-absorbing resin comprises the following steps: Step (1) adding a polyhydroxy polymer to water and dissolving it to obtain a polyhydroxy polymer solution; Step (2) adding an acrylic acid monomer to an alkaline solution for neutralization to form an acrylic acid monomer solution; Step (3) adding acrylamide monomers, N,N-methylenebisacrylamide, inorganic compounds, and the acrylic acid monomer solution obtained in step (2) to the polyhydroxy polymer solution obtained in step (1), stirring uniformly to obtain a mixed solution; Step (4) adding an initiator and a cross-linking agent to the mixed solution obtained in step (3), heating for reaction, and drying to obtain the high-strength water-absorbing resin.

2. The microcapsule according to claim 1, characterized in that The particle size of the microcapsules is 100 to 1000 microns; and / or, The thickness of the capsule wall is 10 to 100 microns.

3. The microcapsule according to claim 2, characterized in that The particle size of the microcapsules is 180 to 600 microns; and / or, The thickness of the capsule wall is 20 to 80 microns.

4. The microcapsule according to claim 1, characterized in that The acrylamide monomer is selected from at least one of acrylamide and N,N-dimethylacrylamide; and / or, The acrylic monomer is selected from at least one of acrylic acid and methacrylic acid; and / or, The polyhydroxy polymer is selected from at least one of polyethylene glycol and polyvinyl alcohol; and / or, The acidic compound is selected from inorganic acids and / or organic acids; and / or, The aldehyde compound of the chitosan coating is selected from at least one of glyoxal, glutaraldehyde and terephthalaldehyde.

5. The microcapsule according to claim 4, characterized in that The acrylamide monomer is selected from acrylamide; and / or, The acrylic monomer is selected from acrylic acid; and / or, The polyhydroxy polymer is selected from polyvinyl alcohol; and / or The acidic compound is selected from at least one of hydrochloric acid, sulfuric acid, nitric acid and acetic acid; and / or, The aldehyde compound of the chitosan coating is selected from glutaraldehyde.

6. The microcapsule according to claim 5, characterized in that The acidic compound is selected from acetic acid.

7. The microcapsule according to claim 1, characterized in that In the high-strength water-absorbing resin, based on the total weight of the acrylamide monomer and the acrylic acid monomer as 100 parts by weight, the amount of the acrylamide monomer is 5 to 100 parts, the amount of the acrylic acid monomer is 0 to 95 parts but not 0, the amount of the polyhydroxy polymer is 1 to 30 parts, and the amount of the inorganic compound is 1 to 20 parts.

8. The microcapsule according to claim 7, characterized in that In the high-strength water-absorbing resin, based on 100 parts by weight of the total weight of the acrylamide monomer and the acrylic acid monomer, the amount of the acrylamide monomer is 10 to 90 parts, the amount of the acrylic acid monomer is 10 to 90 parts, the amount of the polyhydroxy polymer is 2 to 20 parts, and the amount of the inorganic compound is 1 to 15 parts.

9. The method for preparing high-strength water-absorbing resin microcapsules according to claim 1, comprising spraying a coating solution containing chitosan onto the high-strength water-absorbing resin, and drying the resulting high-strength water-absorbing resin microcapsules.

10. The preparation method according to claim 9, characterized in that The chitosan coating solution comprises components including a blended acidic compound, chitosan, an aldehyde compound, and water; and / or, The mass ratio of the high-strength water-absorbing resin to the chitosan coating liquid is 1:0.5 to 1:10; and / or, The spraying conditions are 60-150° C. and 10-60 min.

11. The preparation method according to claim 10, characterized in that: The mass ratio of the high-strength water-absorbing resin to the chitosan coating liquid is 1:1 to 1:5; and / or, The spraying conditions are 80-100° C. and 20-30 min.

12. The preparation method according to claim 10, characterized in that Based on 100 parts by weight of the chitosan coating solution, the chitosan coating solution comprises 1 to 5 parts of an acidic compound, 0.5 to 5 parts of chitosan, 0.02 to 2.5 parts of an aldehyde compound, and the remainder being water; and / or, The acidic compound is selected from inorganic acids and / or organic acids; and / or, The aldehyde compound in the chitosan coating solution is selected from at least one of glyoxal, glutaraldehyde and terephthalaldehyde.

13. The preparation method according to claim 12, characterized in that The acidic compound is selected from at least one of hydrochloric acid, sulfuric acid, nitric acid and acetic acid; and / or, The aldehyde compound in the chitosan coating solution is selected from glutaraldehyde.

14. The preparation method according to claim 13, characterized in that The acidic compound is selected from acetic acid.

15. The preparation method according to claim 9, characterized in that The preparation method of the high-strength water-absorbing resin comprises the following steps: Step (1) adding a polyhydroxy polymer into water and dissolving the polyhydroxy polymer to obtain a polyhydroxy polymer solution; Step (2) adding acrylic acid monomers into an alkaline solution for neutralization to form an acrylic acid monomer solution; Step (3) adding acrylamide monomer, N,N-methylenebisacrylamide, inorganic compound, and acrylic acid monomer solution obtained in step (2) to the polyhydroxy polymer solution obtained in step (1), and stirring to obtain a mixed solution; Step (4) adding an initiator and a cross-linking agent to the mixed solution obtained in step (3), heating for reaction, and drying to obtain the high-strength water-absorbing resin.

16. The preparation method according to claim 15, characterized in that Based on 100 parts by weight of the total weight of the acrylamide monomer and the acrylic acid monomer, the amount of the acrylamide monomer is 5 to 100 parts, the amount of the acrylic acid monomer is 0 to 95 parts but not 0, the amount of the polyhydroxy polymer is 1 to 30 parts, the amount of the inorganic compound is 1 to 20 parts, the amount of the N,N-methylenebisacrylamide is 0.1 to 1 part, the amount of the cross-linking agent is 1 to 5 parts, and the amount of the initiator is 0.1 to 2 parts; and / or, The acrylamide monomer is selected from at least one of acrylamide and N,N-dimethylacrylamide; and / or, The acrylic monomer is selected from at least one of acrylic acid and methacrylic acid; and / or, The polyhydroxy polymer is selected from at least one of polyethylene glycol and polyvinyl alcohol; and / or, The inorganic compound is selected from at least one of bentonite, silicon dioxide, titanium dioxide, montmorillonite, kaolin and calcium carbonate; and / or, The cross-linking agent is selected from aldehyde compounds; and / or, The initiator is selected from at least one of a peroxide initiator, an azo initiator, and a redox initiator.

17. The preparation method according to claim 16, characterized in that Based on 100 parts by weight of the total weight of the acrylamide monomer and the acrylic acid monomer, the amount of the acrylamide monomer is 10-90 parts, the amount of the acrylic acid monomer is 10-90 parts, the amount of the polyhydroxy polymer is 2-20 parts, the amount of the inorganic compound is 1-15 parts, the amount of the N,N-methylenebisacrylamide is 0.2-0.6 parts, the amount of the cross-linking agent is 2-4 parts, and the amount of the initiator is 0.3-1 parts; and / or, The acrylamide monomer is selected from acrylamide; and / or, The acrylic monomer is selected from acrylic acid; and / or, The polyhydroxy polymer is selected from polyvinyl alcohol; and / or The cross-linking agent is selected from at least one of glutaraldehyde, glyoxal, terephthalaldehyde and formaldehyde; and / or, The initiator is selected from potassium persulfate and sodium bisulfite.

18. The preparation method according to claim 15, characterized in that The concentration of the polyhydroxy polymer solution obtained in step (1) is 0.1-10%; and / or, The concentration of the alkaline solution in step (2) is 1-20%; and / or, The alkaline solution in step (2) is selected from at least one of sodium hydroxide solution, sodium carbonate solution, and sodium bicarbonate solution; and / or, The degree of neutralization in step (2) is 30-80%; and / or, In said step (4), before adding the initiator and the cross-linking agent, an inert gas is first introduced; and / or, The heating reaction temperature in step (4) is 30-60°C and the reaction time is 2-6 hours; and / or, The drying temperature in step (4) is 80-100°C.

19. The preparation method according to claim 18, characterized in that The concentration of the polyhydroxy polymer solution obtained in step (1) is 1-5%; and / or, The concentration of the alkaline solution in step (2) is 5-10%; and / or, The alkaline solution in step (2) is a sodium hydroxide solution; and / or, The degree of neutralization in step (2) is 40-60%.

20. A self-repairing cement-based material, comprising the high-strength water-absorbing resin microcapsules according to any one of claims 1 to 8 or the high-strength water-absorbing resin microcapsules obtained by the preparation method according to any one of claims 9 to 19 and cement, wherein the amount of the high-strength water-absorbing resin microcapsules is 0.5-5% of the mass of the cement.

21. The self-repairing cement-based material according to claim 20, characterized in that: The dosage of the high-strength water-absorbing resin microcapsules is 1-3% of the mass of the cement.

22. The method for preparing the self-repairing cement-based material according to claim 20, comprising adding the high-strength water-absorbing resin microcapsules to cement slurry, mixing, and then curing at 70-80°C to obtain the self-repairing cement-based material.

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