Slow-release self-adapting swelling microcapsules, method of preparation and cementitious material

Abstract

The application discloses slow-release self-adapting expansion microcapsules, a preparation method and a cement-based material. The slow-release self-adapting expansion microcapsules are of a core-shell structure, the core-shell structure comprises a plurality of cores composed of 100 parts of an expansion agent, 5-15 parts of a binder and 10-25 parts of an active filler, and a shell formed by 5-20 parts of a coating agent; wherein the shell coats the plurality of cores and forms the core-shell structure; the shell can be dissolved in a liquid environment to release the plurality of cores to absorb the liquid and generate expansion. The microcapsules have a core-shell double-layer structure, comprising an outer high-molecular shell layer and an inner core containing self-adapting expansion material. The outer high-molecular shell layer ensures the slow-release effect of the microcapsules, protects the inner core from the influence of water in the cement paste, and can be pumped to a target layer with the paste; the inner expansion material core ensures that the microcapsules can rapidly absorb water and expand after being released, so as to achieve the purposes of channeling prevention and leakage plugging.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of functional building materials, and particularly relates to a slow-release self-adaptive expansion microcapsule, a preparation method and a cement-based material. BACKGROUND

[0002] When tunnels are constructed in different geological conditions, tunnel accidents such as collapse and water inrush may occur. If water or mud inrush accidents occur in tunnels under water areas such as lakes and rivers, cement slurry is usually used for anti-channeling and plugging construction. However, when the amount of water or mud is large, the plugging cement slurry may be washed away, and a large amount of water may prevent cement hydration from occurring, thereby affecting the setting and hardening of the cement slurry, the leakage cannot be plugged, the plugging effect is poor, and even the plugging operation fails completely. SUMMARY

[0003] Therefore, the present application provides a slow-release self-adaptive expansion microcapsule, a preparation method and a cement-based material. The slow-release self-adaptive expansion microcapsule is prepared by encapsulating a superabsorbent material with a microcapsule, and is pumped into a target area together with a cement-based material to achieve the effect of self-adaptive anti-channeling and plugging.

[0004] The present application is implemented in the following manner. The present application provides a slow-release self-adaptive expansion microcapsule, which has a core-shell structure. The core-shell structure has:

[0005] a plurality of cores composed of 100 parts of an expansion agent, 5-15 parts of a binder and 10-25 parts of an active filler; and

[0006] a shell formed by 5-20 parts of a coating agent.

[0007] The shell coats the plurality of cores and forms the core-shell structure. The shell can be dissolved in a liquid environment to release the plurality of cores to absorb liquid and expand.

[0008] In some embodiments, the mass ratio of the shell to the core is 0.05-0.1:1; or

[0009] The thickness of the shell is 0.1-0.5 mm, and the average particle size of the core is 0.5-2.0 mm.

[0010] In some embodiments, 10-20 cores are coated in each shell. The core and the shell have a gap, so that the porosity of the core-shell structure is greater than 0 and less than or equal to 1%.

[0011] In some embodiments, the liquid environment has any one of acidity, neutrality and alkalinity.

[0012] The dissolution time of the shell in an acidic liquid environment is 2.5-10 min; or

[0013] The dissolution time of the shell in the alkaline liquid environment is 20-120 min; or

[0014] The dissolution time of the shell in the neutral liquid environment is 240-540 min.

[0015] In some embodiments, the swelling agent is selected from at least one of expanded water-absorbing resin, expanded silicate cement, sodium polyacrylate;

[0016] The binder is selected from at least one of polyurethane glue, ethyl cellulose, hydroxypropyl methyl cellulose, sodium silicate; or

[0017] The active filler is selected from at least one of granulated blast furnace slag, metakaolin and fly ash.

[0018] In some embodiments, the coating agent is selected from at least one of ethyl cellulose, microcrystalline cellulose, epoxy resin, paraffin.

[0019] In some embodiments, the application further provides a preparation method of the slow-release self-adapting swelling microcapsule, comprising the following steps:

[0020] Dissolve the binder and the active filler in the first solvent according to the corresponding mass fraction, and take the clarified part to obtain a binder solution; mix the binder solution with the swelling agent according to the corresponding mass fraction, and granulate to obtain spherical particles;

[0021] Mix the coating agent with the second solvent to obtain a coating solution, and spray the coating solution on the surface of the spherical particles to obtain the slow-release self-adapting swelling microcapsule with a core-shell structure.

[0022] In some embodiments, the first solvent is selected from at least one of methanol, dimethylbenzene, Tween 80, methyl acetate, anhydrous ethanol; or

[0023] The second solvent is selected from at least one of methanol, dimethylbenzene, Tween 80, methyl acetate, anhydrous ethanol; or

[0024] The spraying adopts a spray drying method, specifically including: the spraying time of 100 g of the microcapsule in the coating solution at a flow rate of 0.5 mL / s is 10-30 s, and the drying time is 3-10 min.

[0025] In some embodiments, the application further provides a cement-based material, which comprises 100 parts of cement, 100-150 parts of water, 50-100 parts of fine sand, 1-5 parts of water reducing agent, 0.2-0.8 parts of thickening water retaining agent, 0.2-1.5 parts of retarder and 10-20 parts of slow-release self-adapting swelling microcapsule.

[0026] In some embodiments, the cement adopts Portland cement; or

[0027] The fine sand adopts quartz sand or tailings mechanism sand; or

[0028] The water reducing agent adopts polycarboxylic acid water reducing agent; or

[0029] The thickening water retaining agent is selected from at least one of hydroxyethyl cellulose, sodium carboxymethyl cellulose, and warm rubber glue; or

[0030] The retarder is selected from at least one of lignin sulfonate, citric acid, tartaric acid, and gluconate.

[0031] The beneficial effects of the present application are that the slow-release self-adaptive expansion microcapsule of the present application is a core-shell structure, the core-shell structure has a plurality of cores composed of 100 parts of an expanding agent, 5-15 parts of a binder, and 10-25 parts of an active filler; and a shell formed by 5-20 parts of a coating agent; wherein the shell coats the plurality of cores and forms the core-shell structure; the shell can be dissolved in a liquid environment to release the plurality of cores to absorb liquid and produce expansion. The microcapsule of the present application has a core-shell double-layer structure, including an outer high-molecular shell layer and an inner core containing a self-adaptive expansion material. The outer high-molecular shell layer ensures the slow-release effect of the microcapsule, while protecting the inner core from the influence of water in the cement slurry, enabling it to be pumped to the target layer with the slurry; the inner expansion material core ensures that it can rapidly absorb water and expand after the capsule is released, achieving the purpose of preventing channeling and plugging.

[0032] The present application provides a preparation method of a slow-release self-adaptive expansion microcapsule, characterized by comprising the following steps: dissolving a corresponding mass fraction of a binder and an active filler in a first solvent to obtain a binder solution by taking the clarified part; mixing the binder solution with a corresponding mass fraction of an expanding agent and granulating to obtain spherical particles; mixing a coating agent with a second solvent to obtain a coating solution, and spraying the coating solution on the surface of the spherical particles to obtain a slow-release self-adaptive expansion microcapsule with a core-shell structure. By using microcapsule packaging high water-absorbing material to prepare a slow-release self-adaptive expanding agent, it can be pumped into the target area at the same time as the cement concrete, and based on the slow-release effect of the microcapsule when it encounters water, the inner core absorbs water and expands in volume to achieve physical plugging. The microcapsule prepared by the method of the present application can completely plug the water and mud leakage points in the target layer after the cement continues to hydrate and harden, achieving the effect of self-adaptive channeling prevention and plugging. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a slow-release self-adaptive expansion microcapsule structure schematic diagram provided by the embodiments of the present application.

[0034] Figure 2 is a slow-release self-adaptive expansion microcapsule water absorption and expansion schematic diagram provided by the embodiments of the present application. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application. In the present application, the orientation words such as “upper” and “lower” are the directions of the drawing surface in the drawings. In addition, in the description of the present application, the term “comprising” means “including but not limited to”. The various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is only for the convenience and brevity, and should not be understood as a hard limitation on the scope of the present application; therefore, it should be considered that the described range has been specifically disclosed all possible sub-ranges and single values in the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers in the range, such as 1, 2, 3, 4, 5 and 6, regardless of the range. In addition, whenever a numerical range is indicated in the present application, it refers to any cited number (fraction or integer) in the indicated range.

[0036] The present application provides a slow-release self-adapting swelling microcapsule, the slow-release self-adapting swelling microcapsule is a core-shell structure, the core-shell structure has: a plurality of cores composed of 100 parts of an expanding agent, 5-15 parts of a binder and 10-25 parts of an active filler; and a shell formed by 5-20 parts of a coating agent;

[0037] The shell coats the plurality of cores and forms the core-shell structure; the shell can be dissolved in a liquid environment to release the plurality of cores to absorb the liquid and produce swelling.

[0038] Further, referring to Figure 1 , the gray part in the figure is the shell structure, and the black particles inside are the core structure.

[0039] It can be understood that the core-shell structure can achieve the slow release of the active ingredient. Through the dissolution of the shell, the core releases its internal core to absorb the liquid, and the core part contains the swelling agent, which will absorb the liquid and swell when the microcapsule comes into contact with the liquid. This self-adaptive swelling property can be used to control the size, shape and spreading of the microcapsule to adapt to different application requirements. The role of the shell is to protect the core part from the external environment, such as humidity, light, oxygen, etc., which helps to enhance the stability of the core and ensure the maintenance and long-term preservation of the active ingredient. By combining different materials of the shell layer, a multi-layer coating structure can be achieved, further improving the stability and slow release effect of the microcapsule. The interaction between different materials can change the physicochemical properties of the microcapsule, such as controlling the delayed dissolution characteristics of the shell, the adsorption capacity of the core part, etc.

[0040] In some embodiments, the mass ratio of the shell to the core is 0.05-0.1:1. For example, the mass ratio of the shell to the core can be any one of 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1 or a range between any two of them. By adjusting the ratio of the core and the shell, material selection and structure design, the responsiveness and release characteristics of the microcapsule in different environments can be controlled.

[0041] In some embodiments, the thickness of the shell is 0.1-0.5mm. For example, the thickness of the shell can be any one of 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm or a range between any two of them. When the thickness of the shell meets the above range, it can ensure that the shell achieves the effect of slow dissolution in the liquid environment, avoiding the premature exposure of the inner core due to the too small thickness of the shell layer, or the inner core cannot be released to absorb the liquid due to the too large thickness of the shell layer.

[0042] In some embodiments, the average particle size of the core is 0.5-2.0mm. For example, the average particle size of the core can be any one of 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, 2.0mm or a range between any two of them. When the average particle size of the core meets the above range, the size of the microcapsule can be controlled within a reasonable range, and the core with the average particle size can effectively absorb the liquid to swell.

[0043] In some embodiments, each shell encapsulates 10-20 cores, it is understood that there is a gap between the core and the shell, so that the porosity of the core-shell structure is greater than 0 and less than or equal to 1%. The particles of the expanding agent in the core are agglomerated by the binder, the shell layer of the microcapsule gradually dissolves and thins in the liquid environment, and gradually breaks under the action of water pressure, releasing the inner core. When the porosity is not more than 1%, it can be ensured that the microcapsule encapsulates enough inner cores to improve the expansion effect of the microcapsule.

[0044] In some embodiments, the liquid environment has any one of acidic, neutral, and alkaline. The pH range of the acidic environment is 4-5, the pH range of the alkaline environment is 10-11, and the pH range of the neutral environment is 7-8. The preferred environment range is alkaline condition, because when the microcapsule is used as a plugging material, the environment of the external cement slurry is alkaline.

[0045] In some embodiments, the dissolution time of the shell in the acidic liquid environment is 2.5-10 min. It can be any one of 2.5 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, or a range between any two values.

[0046] In some embodiments, the dissolution time of the shell in the alkaline liquid environment is 20-120 min. It can be any one of 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, or a range between any two values.

[0047] In some embodiments, the dissolution time of the shell in the neutral liquid environment is 240-540 min. It can be any one of 240 min, 250 min, 280 min, 300 min, 350 min, 400 min, 450 min, 500 min, 510 min, 520 min, 530 min, 540 min, or a range between any two values.

[0048] In some embodiments, the swelling agent is selected from at least one of a swelling water-absorbing resin, a swelling portland cement, and a sodium polyacrylate. The swelling water-absorbing resin includes at least one of a low-crosslinking sodium polyacrylate, a starch-acrylic acid salt polymer, an acrylamide-acrylic acid-sodium p-styrene sulfonate terpolymer, and a starch-acrylonitrile graft copolymer. The water-absorbing swelling resin is a three-dimensional spatial network polymer, is a high-molecular dielectric, has ionizable ion pairs embedded on the high-molecular network chain, forms an ion network when encountering water, and further absorbs water and swells. The swelling portland cement is selected from a portland cement to which a calcium sulfoaluminate or a lime-based swelling agent is added. The calcium sulfoaluminate generates ettringite crystals during the hydration process of the cement, produces volume expansion, and interweaves with fibrous C-S-H gel microcrystals to form a network structure, thereby improving the density and waterproofness of the cement stone. The CaO in the lime-based swelling agent is hydrated into gelatinous Ca(OH)2 during the initial hydration of the cement, produces volume expansion, and is transformed into larger heterometric and hexagonal plate-shaped crystals, which again produces volume expansion. The water-absorbing principle of the sodium polyacrylate is that when the sodium polyacrylate contacts water, the carboxyl groups (-COOH) in the molecular structure of the sodium polyacrylate can form hydrogen bonds with water molecules, and at the same time, there is an electrostatic repulsion between the molecules of the sodium polyacrylate, which causes the molecular chain to expand and form pores. These pores allow water molecules to penetrate into the interior of the sodium polyacrylate, thereby causing it to absorb water and swell. In addition, the molecular structure of the sodium polyacrylate also contains a large number of carboxyl groups (-COONa + ), which dissociate in water to form negatively charged polyacrylate ions and positively charged sodium ions. Due to the electrostatic repulsion between these ions, the molecular chain of the sodium polyacrylate further stretches to form a network structure, thereby increasing its water absorption capacity. In addition, the water absorption of the sodium polyacrylate is also affected by its crosslinking degree. In the case of low crosslinking degree, water molecules easily penetrate into the polymer, causing the resin to swell, further hydrophilic and gel, and become a high water-absorbing state. The crosslinking degree of the sodium polyacrylate is related to the viscosity, too low viscosity will cause the material strength to be too low and dissolve in water, too high viscosity will cause the material swelling degree to decrease, both of which will reduce the water absorption capacity of the material. The viscosity of the sodium polyacrylate is in the range of 2000-2500 mPa.s.

[0049] It can be understood that the above materials can all be used as the main material for the core to swell, and the above materials can all be obtained through commercial channels.

[0050] In some embodiments, the binder is selected from at least one of a polyurethane glue, ethyl cellulose, hydroxypropyl methyl cellulose, and sodium silicate. The binder is used to aggregate the swelling agent into a group to form a granular core. In addition, the binder can also absorb a certain amount of liquid in a liquid environment, thereby increasing the viscosity and adhesion of the binder.

[0051] In some embodiments, the active filler is selected from at least one of granulated blast furnace slag, metakaolin and fly ash. After the core absorbs the liquid and expands, the active filler can also improve the rheological property of the cement paste, increase the early strength of the system, improve the pore structure of the cement hardened body, and thus improve the durability and prolong the service life of the plugging material after construction. The active filler plays a filling and lubricating role in the system, the surface of the spherical particles is smooth, which can reduce the internal friction of the system and reduce the water demand. In an alkaline environment, the micro aggregate reaction occurs to improve the strength.

[0052] In some embodiments, the plurality of cores of the present application is composed of 100 parts of the expanding agent, 5-15 parts of the binder and 10-25 parts of the active filler. When the expanding agent is a resin, it is better matched with the binder, has good expansion efficiency, high water absorption multiple and rate, and higher compatibility with the system.

[0053] In some embodiments, the water-absorbing and expanding resin can further cooperate with the binder to improve the expansion effect. Because there are micro pores or capillaries in the internal structure of the resin, these structures can adsorb the binder. After the binder contacts water, it can fill the pores or capillaries, the pressure in the pores or capillaries is reduced, causing water to penetrate into these spaces until the wetting point, improving the adsorption effect. Adsorption is also an important process of water absorption, similar to the capillary adsorption principle of materials such as cotton, paper and sponge. The water absorption process of the superabsorbent resin can be divided into several stages. First, water is absorbed through capillary adsorption and dispersion, then water molecules interact with the hydrophilic groups of the resin through hydrogen bonds, the hydrophilic groups dissociate, and the electrostatic repulsion between ions causes the network of the resin to expand. As the amount of water absorption increases, the difference in osmotic pressure between the inside and outside of the network tends to zero; while the network expands, its elastic shrinkage force also increases, gradually offsetting the electrostatic repulsion of the anions, and finally reaching water absorption equilibrium.

[0054] In some embodiments, the coating agent is selected from at least one of ethyl cellulose, microcrystalline cellulose, epoxy resin and paraffin. It can be understood that the coating agent needs to have the performance of being slowly dissolved, and by selecting different coating agents of different materials in different environments, the resistance to different environments can be targeted to improve or reduce the release time.

[0055] In some embodiments, a preparation method of a slow-release self-adapting expansion microcapsule is provided, comprising the following steps:

[0056] The binder and the active filler corresponding to the mass fraction are dissolved in the first solvent, and the clarified part is taken to obtain a binder solution; the binder solution is mixed with the expanding agent corresponding to the mass fraction, and granulated to obtain spherical particles;

[0057] Mixing the coating agent with the second solvent to obtain a coating solution, and spraying the coating solution on the surface of the spherical particles to obtain the core-shell structure slow-release self-adapting expansion microcapsule.

[0058] It can be understood that, referring to Figure 1 , the object of the spraying of the coating solution is the core formed by the plurality of spherical particles.

[0059] In some embodiments, the first solvent is selected from at least one of methanol, dimethylbenzene, Tween 80, methyl acetate, and anhydrous ethanol.

[0060] In some embodiments, the second solvent is selected from at least one of methanol, dimethylbenzene, Tween 80, methyl acetate, and anhydrous ethanol.

[0061] In some embodiments, the spraying adopts a spray drying method, specifically including: the spraying time of 10-30 s of each 100 g of the microcapsule in the coating solution at a flow rate of 0.5 mL / s, and the drying time of 3-10 min. According to actual requirements, different granulation schemes can be adopted. For deep repair, the multi-spraying mode can be adopted to increase the thickness of the shell layer, so as to increase the release time of the core.

[0062] In some embodiments, a specific preparation process is provided. The binder is mixed with the first solvent according to the corresponding parts and the active filler, the clear part in the solution is taken out as the adhesive solution, the swelling agent is adhered into a spherical body by using a disc granulator, the residual solvent is volatilized by using hot air, and then the spherical particles are obtained, and the appropriate particle size is screened as the core. Then, the coating agent is mixed with the second solvent to obtain a coating solution, the disc granulator is used for granulation, the coating agent is coated on the surface of the core particle by spraying at the rotating disc, and the appropriate particle size is screened as the microcapsule. According to different use scenarios, the concentration and coating time of the coating agent can be adjusted, or the core can be coated multiple times, the thickness and strength of the shell layer are adjusted, so as to adapt to the use requirements of different scenarios.

[0063] In some embodiments, a cement-based material is also provided, including 100 parts of cement, 100-150 parts of water, 50-100 parts of fine sand, 1-5 parts of water reducing agent, 0.2-0.8 parts of thickening water retaining agent, 0.2-1.5 parts of retarder, and 10-20 parts of slow-release self-adapting expansion microcapsule. The slow-release self-adapting expansion microcapsule adopts the slow-release self-adapting expansion microcapsule of the embodiment. Alternatively, the slow-release self-adapting expansion microcapsule is prepared by the method of the embodiment.

[0064] In some embodiments, the cement is portland cement, national standard P.O42.5 or 52.5.

[0065] In some embodiments, the fine sand is quartz sand or tailings mechanism sand, which is passed through a 1.18 mm square hole sieve, and the fineness modulus is controlled between 1.21 and 1.36.

[0066] In some embodiments, the water reducing agent is a polycarboxylic acid water reducing agent, and the water reducing rate is between 25% and 35%.

[0067] In some embodiments, the thickening water retaining agent is at least one of hydroxyethyl cellulose, sodium carboxymethyl cellulose, and xanthan gum.

[0068] In some embodiments, the retarder is at least one of lignin sulfonate, citric acid, tartaric acid, and gluconate.

[0069] It can be understood that the silicate cement provides an alkaline environment for the system, hardens after the microcapsule is blocked, provides strength, the addition of fine sand can control the crack of the system after hardening, reduce the brittleness of the hardened body, at the same time increase the strength, the polycarboxylic acid water reducing agent can greatly reduce the water demand of the system, increase the early strength, the thickening water retaining agent can independently adjust the consistency and water loss of the system, and the retarder can control the setting time of the system according to the actual situation, so as to achieve the purpose of remote delivery.

[0070] Before construction, the incorporation of the microcapsule does not significantly change the rheological property and water demand of the cement slurry, and the cement slurry can be delivered by remote construction methods such as pumping, after reaching the working position, the microcapsule gradually breaks, absorbs a large amount of water solution nearby, provides sufficient water for the setting of the cement slurry, and the released microcapsule is in colloidal state, which does not significantly reduce the alkalinity of the system, so as to ensure that the strength of the system does not decrease significantly.

[0071] Examples 1-6

[0072] Examples 1-6 provide different components of the slow-release self-adaptive expansion microcapsule, and the specific amount of parts is shown in Table 1.

[0073] The preparation method of the slow-release self-adaptive expansion microcapsule in Examples 1-6 is the same, which is specifically as follows: the binder and active filler corresponding to the mass fraction are dissolved in anhydrous ethanol, and the clarified part is taken to obtain a binder solution; the binder solution is mixed with the corresponding mass fraction of the expanding agent to obtain spherical particles; the coating agent is mixed with anhydrous ethanol to obtain a coating solution, and the coating solution is sprayed on the surface of the spherical particles to obtain the core-shell structure of the slow-release self-adaptive expansion microcapsule. The spraying adopts the method of spray drying, which specifically includes: the spraying time of 100 g of microcapsule in the coating solution at a flow rate of 0.5 mL / s is 20 s, and the drying time is 5 min.

[0074] Table 1

[0075]

[0076]

[0077] Example 7

[0078] Select 42.5 Portland cement 100 parts, modulus 1.25 quartz sand 60 parts, polycarboxylic acid water reducer 2 parts, hydroxyethyl cellulose 0.4 parts, lignosulfonate 0.5 parts, water 150 parts, the slow-release self-adapting expansion microcapsule of example 1 15 parts, mix, get cement-based material.

[0079] In this example, the setting time of cement is 3.5h, the slow-release time of self-adapting expansion microcapsule is 3h, see Figure 2 , the water absorption of expansion agent is 300-500 times of its weight, the expansion rate is 350-450 times of the volume in dry state, using beaker method to determine. The rheological property of cement paste is 25cm, the 24h strength is 14Mpa.

[0080] Example 8

[0081] Select 42.5 Portland cement 100 parts, modulus 1.30 quartz sand 65 parts, polycarboxylic acid water reducer 1 part, sodium hydroxymethyl cellulose 0.3 parts, citric acid 0.5 parts, water 120 parts, the slow-release self-adapting expansion microcapsule of example 2 10 parts, mix, get cement-based material.

[0082] In this example, the setting time of cement is 3.5h, the slow-release time of self-adapting expansion microcapsule is 4h, the water absorption of expansion agent is 250-400 times of its weight, the expansion rate is 300-400 times of the volume in dry state, using beaker method to determine. The rheological property of cement paste is 23cm, the 24h strength is 13Mpa.

[0083] Example 9

[0084] Select 52.5 Portland cement 100 parts, modulus 1.25 quartz sand 80 parts, polycarboxylic acid water reducer 5 parts, xanthan gum 0.4 parts, tartaric acid 1.5 parts, water 100 parts, the slow-release self-adapting expansion microcapsule of example 3 20 parts, mix, get cement-based material.

[0085] In this example, the setting time of cement is 3.5h, the slow-release time of self-adapting expansion microcapsule is 3.5h, the water absorption of expansion agent is 200-300 times of its weight, the expansion rate is 150-200 times of the volume in dry state, using beaker method to determine. The rheological property of cement paste is 23cm, the 24h strength is 18Mpa.

[0086] Comparative Example 1

[0087] Provide a kind of cement-based material, specific composition is same with example 7, different in that no slow-release self-adapting expansion microcapsule is added.

[0088] In the comparative example, the setting time of the cement is 3.6 h, the rheological property of the cement paste is 27 cm, the 24 h strength is 12 MPa, the water absorption and the expansion rate of the system are extremely low. Without the microcapsule system, the water absorption and expansion cannot be achieved, and the reliability is significantly reduced when applied to the anti-channeling and plugging work, and even no strength can be generated.

[0089] Comparative Example 2

[0090] A cement-based material is provided, and the specific composition is the same as that of Example 8, except that no water reducing agent is added.

[0091] In the comparative example, the setting time of the cement is 3 h, the release time of the self-adaptive expansion agent is 4 h, the water absorption of the expansion agent is 250-400 times of the self-weight, and the expansion rate is 300-400 times of the volume in the dry state. The rheological property of the cement paste is 15 cm, and the 24 h strength is 11.5 MPa. The water reducing agent can prolong the setting time of the system, and without the water reducing agent, the rheological property of the cement paste is reduced, the water demand is increased, the water content is increased, which leads to the difficulty in pumping and even plugging the pump pipe. The reason is that the polycarboxylic acid water reducing agent forms an adsorption layer on the surface of the cement particles, effectively preventing the mutual adsorption and coagulation between the particles, reducing the friction between the cement particles, thereby reducing the cohesiveness of the concrete, reducing the water content under the same cement dosage, and achieving the effect of water reduction. In this way, the strength and durability of the concrete can be improved.

[0092] Comparative Example 3

[0093] A cement-based material is provided, and the specific composition is the same as that of Example 9, except that the core material of the microcapsule is a mixture of a multi-component copolymer resin and sodium polyacrylate.

[0094] In the comparative example, the setting time of the cement is 3.5 h, the release time of the self-adaptive expansion agent is 2.5 h, the water absorption of the expansion agent is 180-260 times of the self-weight, and the expansion rate is 130-180 times of the volume in the dry state. The rheological property of the cement paste is 22 cm, and the 24 h strength is 17 MPa.

[0095] The mixture of the multi-component copolymer resin and the sodium polyacrylate cannot significantly improve the water absorption, expansion rate and working performance of the system, and the control of the release time is more difficult. Using the same coating process, it is difficult to achieve good coating rate for both core materials, which reduces the release efficiency of the core material, and increases the workload and cost.

[0096] In summary, the microcapsule has a double-layer structure of core-shell, including a high polymer shell layer of the outer layer and an inner core containing self-adapting swelling material. The outer high polymer shell layer ensures the slow release of the microcapsule, and protects the inner core from the influence of water in the cement slurry, and can be pumped to the target layer with the slurry; the inner swelling material core ensures that the microcapsule can rapidly absorb water and swell after being released, and can achieve the purpose of anti-channeling and leak sealing.

[0097] In the above embodiments, the description of each embodiment has its own focus, and the parts not described in detail in a certain embodiment can be referred to the relevant description of other embodiments.

[0098] The product and the preparation method provided by the embodiments of the present application are described in detail above, and the principles and implementation manners of the present application are described by applying specific examples; the above embodiment descriptions are only used to help understand the method and the core idea of the present application; meanwhile, for those skilled in the art, the specific implementation manners and application ranges will be changed according to the idea of the present application; in summary, the content of the present application should not be understood as a limitation.

Claims

1. A slow release self-adapting expanding microcapsule, characterized in that, The slow-release self-adapting expansion microcapsule is a core-shell structure, the core-shell structure has: a plurality of cores composed of 100 parts of an expansion agent, 5-15 parts of a binder, and 10-25 parts of an active filler; and a shell formed by 5-20 parts of a coating agent; wherein the shell coats the plurality of cores and forms the core-shell structure; the shell can be dissolved in a liquid environment to release the plurality of cores to absorb liquid and generate expansion; the binder is selected from ethyl cellulose; the coating agent is selected from at least one of ethyl cellulose, microcrystalline cellulose, epoxy resin, and paraffin; The preparation method of the slow-release self-adapting expansion microcapsule comprises the following steps: dissolve the corresponding mass parts of the binder and the active filler in a first solvent, take the clear part to obtain a binder solution; mix the binder solution with the corresponding mass parts of the expansion agent, granulate to obtain spherical particles; mix the coating agent with a second solvent to obtain a coating solution, spray the coating solution on the surface of the spherical particles to obtain the slow-release self-adapting expansion microcapsule with a core-shell structure; the first solvent is selected from at least one of methanol, dimethylbenzene, Tween 80, methyl acetate, and anhydrous ethanol; the second solvent is selected from at least one of methanol, dimethylbenzene, Tween 80, methyl acetate, and anhydrous ethanol.

2. The slow-release self-adapting expanding microcapsule according to claim 1, wherein, the mass ratio of the shell to the core is 0.05-0.1:1; or the thickness of the shell is 0.1-0.5 mm, and the average particle size of the core is 0.5-2.0 mm.

3. The slow-release self-adapting expanding microcapsule according to claim 1, wherein, 10-20 cores are coated in each shell; the core and the shell have a gap, so that the porosity of the core-shell structure is greater than 0 and less than or equal to 1%.

4. The slow-release self-adapting swelling microcapsule according to claim 1, wherein, The liquid environment has any one of acidity, neutrality, and alkalinity; wherein the dissolution time of the shell in the acidic liquid environment is 2.5-10 min; or the dissolution time of the shell in the alkaline liquid environment is 20-120 min; or the dissolution time of the shell in the neutral liquid environment is 240-540 min.

5. The slow-release self-adapting expanding microcapsule of claim 1, wherein, The expansion agent is selected from at least one of expanded water-absorbing resin, expanded silicate cement, and sodium polyacrylate.

6. The slow-release self-adapting swelling microcapsule according to claim 1, wherein, The spraying adopts a spray drying method, specifically including: the spraying time of 100 g of the microcapsule in the coating solution at a flow rate of 0.5 mL / s is 10-30 s, and the drying time is 3-10 min.

7. A cement-based material, comprising 100 parts of cement, 100-150 parts of water, 50-100 parts of fine sand, 1-5 parts of water reducing agent, 0.2-0.8 parts of thickening water retaining agent, 0.2-1.5 parts of retarder, and 10-20 parts of slow-release self-adapting expansion microcapsule; wherein, The slow-release self-adapting expansion microcapsule adopts the slow-release self-adapting expansion microcapsule of any one of claims 1-6.

8. A cementitious material according to claim 7, characterised in that, The cement adopts Portland cement; or The fine sand adopts quartz sand or tailings mechanism sand; or The water reducing agent adopts polycarboxylic acid water reducing agent; or The thickening water retaining agent is selected from at least one of hydroxyethyl cellulose, sodium carboxymethyl cellulose, and xanthan gum; or The retarder is selected from at least one of lignin sulfonate, citric acid, tartaric acid, and gluconate.

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