Cement temperature inhibition and crack self-repairing microcapsule, preparation method and application thereof

Abstract

The present application relates to the technical field of self-repairing microcapsules, and discloses a cement temperature inhibition and crack self-repairing microcapsule, a preparation method and application thereof, which comprises a core material and a shell material covering the core material; the core material is composed of a phase change epoxy compound and a low phase change temperature material at a mass ratio of (7-9):(1-3); the shell material is formed by free radical polymerization of an amino-containing olefin oil-soluble monomer and a flexible oil-soluble diene monomer; a to-be-polymerized system is obtained by mixing the core material with a dispersing agent and a monomer; and an initiator solution is added to obtain the microcapsule through a two-stage polymerization reaction. The microcapsule can effectively inhibit the hydration heat release of cement slurry to maintain the stability of the hydrate formation, and simultaneously realize the efficient self-repairing of micro-cracks in the cement stone, thereby solving the two core technical problems of hydrate decomposition induced by hydration heat in the cementing process of the natural gas hydrate layer and micro-cracks in the service process of the cement stone, ensuring the cementing quality, and realizing the safe and efficient development of resources.

Description

Technical Field

[0001] This invention relates to the field of self-healing microcapsule technology, and more specifically, to a cement temperature inhibition and crack self-healing microcapsule, its preparation method, and its application. Background Technology

[0002] Cementing operations, as a crucial step in hydrate formation exploitation, directly determine wellbore integrity and the long-term sustainability of reservoir development, and are the core technology for achieving large-scale and safe development of this type of resource. Natural gas hydrates can only remain stable under specific low-temperature and high-pressure environments, a characteristic that imposes stringent performance requirements on cementing materials.

[0003] Two major technical challenges exist in cementing natural gas hydrate formations: First, the large amount of heat released during the hydration reaction of the cement slurry leads to increased temperatures around the wellbore, inducing significant hydrate decomposition. The resulting high-pressure gas intrudes into the uncured cement slurry, creating micro-annulus between the cement sheath and the wellbore, resulting in decreased cement bonding quality. Continuous gas surges can also trigger blowouts, and in severe cases, cause localized formation collapse and instability. Second, hydrate formations are often weakly cemented sedimentary formations. Formation stress, alternating temperature stress, and stress generated during production operations continuously impact the cement stone, causing microcracks and pores within the cement sheath, damaging wellbore integrity. This leads to a drop in gas pressure near the interface, further accelerating hydrate decomposition and creating a vicious cycle.

[0004] Therefore, effectively suppressing the heat release from cement slurry hydration to maintain the stability of hydrate formations, while simultaneously achieving efficient self-repair of microcracks in the cement annulus, is a key technical requirement for ensuring the cementing quality of natural gas hydrate formations and realizing the safe and efficient development of resources.

[0005] In existing technologies, some solutions reduce the heat of hydration by using low-heat cement or adding mineral admixtures, but the temperature suppression effect is limited and cannot meet the stringent requirements of hydrate formations. Other technologies use single-phase change microcapsules to suppress temperature rise or use self-healing microcapsules to repair cement cracks, but neither can simultaneously solve the two core problems of hydrate decomposition induced by the heat of hydration and microcracks in the cement annulus. This results in cementing quality that cannot meet the requirements of complex working conditions in hydrate formations, restricting the safety and reliability of cementing operations. Summary of the Invention

[0006] In view of this, the present invention provides a cement temperature suppression and crack self-repair microcapsule, its preparation method and application. The microcapsule can effectively suppress the heat release of cement slurry hydration to maintain the stability of hydrate formation, and at the same time realize the efficient self-repair of cement stone microcracks. It solves the two core technical problems of hydrate decomposition induced by hydration heat during the cementing process of natural gas hydrate formation and microcracks during the service of cement stone, thus ensuring cementing quality and realizing the safe and efficient development of resources.

[0007] The technical solution of this invention is as follows:

[0008] In a first aspect, the present invention provides a cement temperature inhibition and crack self-healing microcapsule, the microcapsule comprising a core material and a shell material covering the core material;

[0009] The core material is composed of a phase change epoxy compound and a low phase change temperature material in a mass ratio of (7-9):(1-3); the shell material is formed by free radical polymerization of an amino olefin oil-soluble monomer and a flexible oil-soluble diene monomer.

[0010] The low phase transition temperature material includes at least one of n-pentadecane, n-tetradecane, ethylene glycol diacetate, pentaerythritol tetrabutyrate, 1-octanol, 1-nonanol, tetradecanol, hexadecyl alcohol, and chlorinated paraffin-52.

[0011] Furthermore, the phase change epoxy compound includes at least one selected from epoxy glycidyl stearate, epoxy palmitate glycidyl ester, 1,2-epoxy octadecane, 1,2-epoxy eicosane, and 1,2-epoxy hexadecane.

[0012] Furthermore, the mass ratio of the amino-containing oil-soluble monomer to the flexible oil-soluble diene monomer is (4-9):(1-2).

[0013] Furthermore, the amino-containing oil-soluble monomer includes at least one of p-aminostyrene, 4-aminovinylpyridine, 2-amino-5-vinylthiophene, 1-amino-4-vinylimidazolium, and N-(3-aminobenzyl)maleimide.

[0014] Furthermore, the flexible oil-soluble diene monomer includes at least one of 1,3-butadiene, isoprene, 1,9-decadiene, and hexanediol diacrylate.

[0015] Secondly, based on the same inventive concept, the present invention provides a method for preparing the microcapsules according to any one of the first aspects, comprising the following steps:

[0016] S1. By mass, 70-90 parts of phase change epoxy compound and 10-30 parts of low phase change temperature material are stirred and mixed to obtain microcapsule core material;

[0017] S2. Take 15-30 parts of the microcapsule core material and 1-8 parts of water-soluble dispersant and stir to disperse in 400-800 parts of water. Add 20-45 parts of amino-based oil-soluble monomer and 5-10 parts of flexible oil-soluble diene monomer, stir for 15-30 minutes to obtain the polymerization system.

[0018] S3. Dissolve 0.5-3 parts of oil-soluble initiator in 1-5 parts of an amino-olefin-containing oil-soluble monomer to obtain an initiator solution;

[0019] S4. Add the initiator solution dropwise to the polymerization system, raise the temperature to 70-80°C at a rate of 2-3°C / min, react for 2-4 hours, raise the temperature to 85-90°C, react for 20-30 minutes, and obtain the reaction product;

[0020] S5. The reaction product is washed by vacuum filtration and dried at 40-70°C to obtain the microcapsules.

[0021] Further, the water-soluble dispersant in step S2 includes at least one of polyvinyl alcohol 1788, polyethylene glycol with a molecular weight of 4000-10000, hydroxypropyl methylcellulose, and polyvinylpyrrolidone with a molecular weight of 8000-50000.

[0022] Furthermore, the oil-soluble initiator in step S3 includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, azobiscyclohexylformitrile, benzoyl peroxide-N,N-dimethylaniline composite initiator system, and potassium persulfate-dodecyl mercaptan initiator system.

[0023] Further, the mixing conditions in step S1 are specifically: mixing temperature 30-50℃, mixing speed 200-300r / min, and mixing time 20-40min; the dispersion conditions in step S2 are specifically: mixing temperature 40-60℃, mixing speed 600-900r / min, and mixing time 10-30min.

[0024] Thirdly, based on the same inventive concept, this invention provides the application of cement temperature suppression and crack self-repair microcapsules as described in any one of the first aspects or cement temperature suppression and crack self-repair microcapsules prepared by the preparation method described in any one of the second aspects in suppressing the hydration temperature rise of cement cement and self-repairing microcracks in cement sheaths.

[0025] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects:

[0026] 1. This invention, through microcapsule design, organically combines phase change temperature control and self-repair functions, achieving for the first time the integration of dual functions: suppressing temperature rise during cementing of natural gas hydrate layers and repairing microcracks during cement stone service. Compared with existing technologies that use single phase change microcapsules or single self-repair microcapsules, this invention can simultaneously address the two major technical challenges of hydrate decomposition induced by cement hydration exothermics and microcracks in cement stone, fundamentally solving the limitation of single function in traditional solutions.

[0027] 2. By optimizing the ratio of phase change epoxy compounds and low phase change temperature materials in the core material, and by selecting low phase change temperature materials, microcapsules can absorb a large amount of heat through phase change during cement hydration, effectively controlling the temperature rise. Compared with traditional low-heat cement or mineral admixture solutions, this phase change temperature control mechanism has higher heat capacity and more precise temperature control effect.

[0028] 3. The microcapsule shell material adopts a free radical polymerization system containing amino olefin oil-soluble monomers and flexible oil-soluble diene monomers. When microcracks occur in the cement stone, the epoxy compounds released by the microcapsules can chemically bond with the microcapsule shell and the cement matrix to achieve efficient self-repair. Compared with traditional self-repair technology, the epoxy compounds in this invention have better low-temperature fluidity, rapid reaction and bonding performance, and can effectively restore the integrity of the cement stone.

[0029] 4. The flexible oil-soluble diene monomers and hydrophilic amino-containing olefin monomers copolymer structural units in the shell material endow the shell with both rigidity and flexibility and compatibility with microcapsule cement slurry, enabling it to withstand the shear force during cement slurry mixing without breakage. It plays a role in strengthening and toughening the cement stone during its service life. The capsule composition and structural design ensure the performance stability of the microcapsules under complex working conditions. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a comparison chart of the self-healing experimental test and the cement slurry hydration heat test results of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0034] To address the technical problems existing in the prior art, according to one aspect of the embodiments of this disclosure, a cement temperature inhibition and crack self-healing microcapsule is provided, which includes a core material and a shell material covering the core material;

[0035] The core material is composed of phase change epoxy compounds and low phase change temperature materials in a mass ratio of (7-9):(1-3); the shell material is formed by free radical polymerization of amino olefin oil-soluble monomers and flexible oil-soluble diene monomers.

[0036] It is worth noting that, on the one hand, this invention utilizes the endothermic phase change properties of low phase change temperature materials in the core material to efficiently suppress the temperature rise during cement slurry hydration, preventing the decomposition of natural gas hydrates induced by temperature increases, and avoiding safety accidents such as gas-water cross-flow, micro-annulus formation, and well blowouts. On the other hand, by leveraging the self-healing function of the phase change epoxy compound, when microcracks occur in the cement stone, the polymer shell ruptures under crack stress, releasing the core material and undergoing a solidification reaction, achieving rapid repair of microcracks, restoring the integrity of the cement stone and the wellbore sealing, interrupting the vicious cycle of accelerated hydrate decomposition, and ultimately providing reliable technical support for cementing natural gas hydrate layers.

[0037] It should be noted that this invention is based on multifunctional integrated phase change microcapsule technology. Its core principle is to achieve a dual function of temperature suppression and crack self-repair through the collaborative design of materials science and chemical engineering. Utilizing the latent heat of phase change in phase change materials, when cement hydration releases heat, the phase change epoxy compounds in the microcapsule core undergo a solid-liquid phase change with materials at low phase change temperatures, absorbing a large amount of heat and effectively reducing the rate of temperature rise in the cement slurry, preventing hydrate decomposition. Furthermore, when microcracks develop in the cement stone, the crack stress causes the microcapsule shell to rupture, releasing reactive phase change epoxy compounds. After the epoxy groups open in the cement pores, they undergo cross-linking polymerization with the shell's amino groups, forming new chemical bonds that re-bond and repair the cracks, restoring the integrity of the cement stone.

[0038] In some examples, low phase transition temperature materials include at least one of n-pentadecane, n-tetradecane, ethylene glycol diacetate, pentaerythritol tetrabutyrate, 1-octanol, 1-nonanol, tetradecanol, hexadecyl alcohol, and chlorinated paraffin-52.

[0039] In some examples, the phase change epoxy compound includes at least one of glycidyl stearate, glycidyl palmitate, 1,2-epoxyoctadecane, 1,2-epoxyeicosane, and 1,2-epoxyhexadecane.

[0040] In some examples, the mass ratio of amino-containing oil-soluble monomers to flexible oil-soluble diene monomers is (4-9):(1-2).

[0041] In some examples, the amino-olefin oil-soluble monomers include at least one of p-aminostyrene, 4-aminovinylpyridine, 2-amino-5-vinylthiophene, 1-amino-4-vinylimidazolium, and N-(3-aminobenzyl)maleimide.

[0042] In some examples, the flexible oil-soluble diene monomers include at least one of 1,3-butadiene, isoprene, 1,9-decadiene, and hexanediol diacrylate.

[0043] According to another aspect of the embodiments of this application, a method for preparing cement temperature inhibition and crack self-healing microcapsules is also provided, comprising the following steps:

[0044] S1. By mass, 70-90 parts of phase change epoxy compound and 10-30 parts of low phase change temperature material are stirred and mixed to obtain microcapsule core material;

[0045] S2. Take 15-30 parts of microcapsule core material and 1-8 parts of water-soluble dispersant and stir to disperse in 400-800 parts of water. Add 20-45 parts of amino olefin oil-soluble monomer and 5-10 parts of flexible oil-soluble diene monomer, stir for 15-30 minutes to obtain the polymerization system.

[0046] S3. Dissolve 0.5-3 parts of oil-soluble initiator in 1-5 parts of oil-soluble monomer containing aminoolefins to obtain an initiator solution;

[0047] S4. Add the initiator solution dropwise to the polymerization system, raise the temperature to 70-80℃ at a rate of 2-3℃ / min, react for 2-4h, raise the temperature to 85-90℃, react for 20-30min, and obtain the reaction product;

[0048] S5. The reaction product was washed by vacuum filtration and dried at 40-70℃ to obtain microcapsules.

[0049] In some examples, the water-soluble dispersant in step S2 includes at least one of polyvinyl alcohol 1788, polyethylene glycol with a molecular weight of 4,000-10,000, hydroxypropyl methylcellulose, and polyvinylpyrrolidone with a molecular weight of 8,000-50,000.

[0050] In some examples, the oil-soluble initiator in step S3 includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, azobiscyclohexylformitrile, benzoyl peroxide-N,N-dimethylaniline complex initiator system, and potassium persulfate-dodecyl mercaptan initiator system.

[0051] In some examples, the mixing conditions in step S1 are specifically: mixing temperature 30-50℃, mixing speed 200-300r / min, and mixing time 20-40min; the dispersion conditions in step S2 are specifically: mixing temperature 40-60℃, mixing speed 600-900r / min, and mixing time 10-30min.

[0052] It should be noted that the microcapsules prepared by the above method integrate temperature suppression and crack self-healing functions into a single microcapsule system through innovative composite functional design, effectively solving the core technical challenges in cementing natural gas hydrate layers. This technology employs a composite core material design of phase change epoxy compounds and low phase change temperature materials. The latent heat absorption characteristics of the phase change materials effectively suppress the temperature rise during cement hydration, while the epoxy compounds act as repair agents to achieve self-healing of microcracks in the cement stone. The shell structure, formed by the free radical polymerization of amino-containing olefin monomers and flexible diene monomers, ensures the mechanical strength of the capsule and improves its compatibility with the cement matrix. Furthermore, the cross-linking of the epoxy compounds during the self-healing process enhances the self-healing efficiency and maintains the strength of the cement stone after self-healing. Compared to existing single-function low-heat cement or single-phase change microcapsules, this technology, through the synergistic effect of temperature suppression and self-healing, avoids the vicious cycle of hydrate decomposition and wellbore integrity damage, significantly improving the safety and reliability of cementing quality. Its preparation process adopts in-situ polymerization, with clear steps and parameters, and has good industrialization prospects. It is not only suitable for natural gas hydrate extraction, but can also be applied to other concrete structure engineering fields that require temperature control and self-healing, such as deep well cementing and geothermal well cementing.

[0053] According to another aspect of the embodiments of this application, the application of microcapsules as described in any of the first aspects or microcapsules prepared by any of the preparation methods described in any of the second aspects in suppressing the temperature rise of cement hydration and self-repairing microcracks in cement sheaths is also provided.

[0054] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed according to national standards. If no corresponding national standard exists, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0055] Example 1

[0056] This embodiment 1 provides a cement temperature inhibition and crack self-healing microcapsule and its preparation method. The preparation method includes the following steps:

[0057] S1. Mix 70g of glycidyl epoxystearate and 30g of tetradecyl alcohol at 30°C and 300r / min for 30min to obtain microcapsule core material;

[0058] S2. Disperse 20g of microcapsule core material and 5g of polyvinyl alcohol 1788 in 500mL of water, add 30g of p-aminostyrene and 6g of 1,3-butadiene, and stir and mix at 30℃ and 800r / min for 20min to obtain the polymerization system;

[0059] S3. Dissolve 1g of azobisisobutyronitrile in 3g of aminostyrene to obtain an initiator solution;

[0060] S4. Add the initiator solution dropwise to the polymerization system, raise the temperature to 70°C at a rate of 2°C / min, react for 3 hours, raise the temperature to 85°C, react for 20 minutes, and obtain the reaction product;

[0061] S5. The reaction product was washed by vacuum filtration and dried at 60°C to obtain microcapsules.

[0062] Example 2

[0063] This embodiment 2 provides a cement temperature inhibition and crack self-healing microcapsule and its preparation method. The preparation method includes the following steps:

[0064] S1. Mix 80g of glycidyl palmitate and 20g of ethylene glycol diacetate at 30°C and 300r / min for 30min to obtain microcapsule core material;

[0065] S2. Disperse 20g of microcapsule core material and 6g of hydroxypropyl methylcellulose in 600mL of water, add 35g of 4-aminovinylpyridine and 7g of isoprene, and stir and mix at 700r / min for 20min at 25℃ to obtain the polymerization system;

[0066] S3. Dissolve 0.5g of benzoyl peroxide and 0.5g of N,N-dimethylaniline initiator system in 3g of 4-aminovinylpyridine to obtain initiator solution;

[0067] S4. Add the initiator solution dropwise to the polymerization system, raise the temperature to 70°C at a rate of 2°C / min, react for 3 hours, raise the temperature to 85°C, react for 20 minutes, and obtain the reaction product;

[0068] S5. The reaction product was washed by vacuum filtration and dried at 60°C to obtain microcapsules.

[0069] Example 3

[0070] This embodiment 3 provides a cement temperature inhibition and crack self-healing microcapsule and its preparation method. The preparation method includes the following steps:

[0071] S1. Mix 85g of 1,2-epoxyoctadecane and 15g of n-pentadecane at 30°C and 300r / min for 30min to obtain microcapsule core material;

[0072] S2. Take 20g of microcapsule core material and 5g of polyethylene glycol with a molecular weight of 4000 and disperse them in 800mL of water. Add 30g of 1-amino-4-vinylimidazolium and 6g of hexanediol diacrylate. Stir and mix at 30℃ and 800r / min for 20min to obtain the polymerization system.

[0073] S3. Dissolve 1g of azobisisobutyronitrile in 2g of 1-amino-4-vinylimidazolium to obtain an initiator solution;

[0074] S4. Add the initiator solution dropwise to the polymerization system, raise the temperature to 70°C at a rate of 2°C / min, react for 3 hours, raise the temperature to 85°C, react for 20 minutes, and obtain the reaction product;

[0075] S5. The reaction product was washed by vacuum filtration and dried at 60°C to obtain microcapsules.

[0076] Comparative Example 1

[0077] Comparative Example 1 provides an amino-containing polymer microsphere and its preparation method, which is basically the same as Example 1, except that the microcapsule core material in step S1 of Example 1 is not added, in order to verify the effect of the absence of core material on cement hydration and crack self-repair. The specific preparation method is as follows:

[0078] S1. Take 30g of p-aminostyrene and 6g of 1,3-butadiene, add 5g of polyvinyl alcohol 1788 and disperse in 500mL of water, stir and mix at 30℃ and 800r / min for 20min to obtain the polymerization system;

[0079] S2. Dissolve 1g of azobisisobutyronitrile in 3g of p-aminostyrene to obtain an initiator solution;

[0080] S3. Add the initiator solution dropwise to the polymerization system, raise the temperature to 70°C at a rate of 2°C / min, react for 3 hours, raise the temperature to 85°C, react for 20 minutes, and obtain the reaction product;

[0081] S4. The reaction product was washed by vacuum filtration and dried at 60°C to obtain amino-containing polymer microspheres.

[0082] Comparative Example 2

[0083] Comparative Example 2 provides a microcapsule and its preparation method, which are basically the same as those in Example 1, except that the epoxy-based phase change material in the microcapsule core material of Example 1 in step S1 is removed, in order to verify the effect of the absence of epoxy-based phase change material on cement hydration and crack self-repair. The specific preparation method is as follows:

[0084] S1. Take 20g of tetradecyl alcohol as the microcapsule core material and disperse it with 5g of polyvinyl alcohol 1788 in 500mL of water, add 30g of p-aminostyrene and 6g of 1,3-butadiene, and stir and mix at 30℃ and 800r / min for 20min to obtain the polymerization system;

[0085] S2. Dissolve 1g of azobisisobutyronitrile in 3g of p-aminostyrene to obtain an initiator solution;

[0086] S3. Add the initiator solution dropwise to the polymerization system, raise the temperature to 70°C at a rate of 2°C / min, react for 3 hours, raise the temperature to 85°C, react for 20 minutes, and obtain the reaction product;

[0087] S4. The reaction product was washed by vacuum filtration and dried at 60°C to obtain microcapsules.

[0088] To better understand this invention, cement self-healing and temperature suppression application experiments were conducted on the embodiments and comparative examples to test the maximum temperature (T) reached by the system during cement hydration. max The compressive strength of the cement paste system before and after self-healing was measured. The preparation, curing, and mechanical property testing of the cement paste system were carried out in accordance with GB / T19139-2012 standard.

[0089] The products obtained in the examples and comparative examples were configured into a cement slurry system. The cement slurry system was configured as follows: by weight, 60 parts of Grade G cement, 3 parts of 2-acrylamide-2-methylpropanesulfonic acid (AMPS, 60%)-acrylamide (30%)-acrylic acid (10%) copolymer-type filtration loss reducer, 2 parts of sulfonated acetone-formaldehyde condensate-type dispersant, and 26.4 parts of tap water were added to the above components. 5 parts of the products obtained in the examples and comparative examples were added to each component, and the mixture was mechanically stirred to obtain the cement slurry system. The cement slurry system was poured into a mold and placed in water. After curing at 25°C in a bath for 7 days, the cement paste was demolded to obtain cement stone corresponding to the products obtained in the examples and comparative examples. The cement slurry system with the product of Example 1 and the cement stone to be tested was marked as S-1, the cement slurry system with the product of Example 2 and the cement stone to be tested was marked as S-2, the cement slurry system with the product of Example 3 and the cement stone to be tested was marked as S-3, the cement slurry system with the product of Comparative Example 1 and the cement stone to be tested was marked as D-1, and the cement slurry system with the product of Comparative Example 2 and the cement stone to be tested was marked as D-2.

[0090] In addition to the cement stone to be tested mentioned above, other cement slurry systems and cement stones to be tested were prepared, labeled as D-3, S-4 and S-5 respectively. The configuration of D-3 was basically the same as that of S-1, except that the product (microcapsules) obtained in Example 1 was not added. The configuration of S-4 was basically the same as that of S-1, except that the amount of the product obtained in Example 1 added was 10 parts. The configuration of S-5 was basically the same as that of S-1, except that the amount of the product obtained in Example 1 added was 15 parts.

[0091] The self-healing test and the hydration heat test of the cement paste system obtained above were conducted. The self-healing test procedure was as follows: the cement paste to be tested was used as a sample and crack pre-formed on a universal testing machine. An external force was applied at a loading rate of 1 kN / min. When the applied pressure was 60% of the ultimate compressive strength of the sample, the pressure was maintained for 3 minutes and then the pressure was unloaded. The sample was sealed and fixed and placed in a 25℃ environment for self-healing for 3 days. The compressive strength was then tested. The self-healing efficiency was calculated according to the following formula:

[0092] η = (P r / P0) × 100%

[0093] In the formula, η is the compressive strength recovery rate of the self-healing specimen, which is dimensionless; P r P0 represents the compressive strength of the cement stone after repair, in MPa; P0 represents the initial compressive strength of the cement stone before crack pre-forming, in MPa.

[0094] The steps for testing the heat of hydration of cement paste are as follows: Use an isothermal calorimeter to monitor the cement hydration process and obtain the highest temperature (T) reached by the system during the hydration process. max After placing an appropriate amount of cement slurry system in the test tray, place it in an insulated channel and test continuously for 72 hours at 25°C.

[0095] The test results are shown in the table below:

[0096]

[0097] Please refer to Figure 1 ,Depend on Figure 1 As shown in the table above, the microcapsules prepared in Examples 1 (S-1), 2 (S-2), and 3 (S-3) have a significant temperature inhibition effect during cement hydration and a self-repair function for cement stone microcracks.

[0098] When the microcapsule dosage was 5%, the self-healing efficiency of the cement stone prepared in Examples 1 (S-1), 2 (S-2), and 3 (S-3) was all above 85%. As the dosage of the microcapsules obtained in Example 1 increased in the cement stone, the self-healing efficiency gradually increased. In cement stones S-4 and S-5, the microcapsule dosages were 10% and 15%, respectively, with self-healing efficiencies reaching 90.2% and 95.1%. Simultaneously, the maximum temperature decreased significantly during cement hydration. When the dosage of the microcapsules prepared in Example 1 in the cement slurry system was 5% (S-1), 10% (S-4), and 15% (S-5), the test results compared with the blank cement slurry system (D-3) showed a significant decrease in temperature. max The temperatures decreased by 11.2 ℃, 22.1 ℃, and 28.2 ℃, respectively.

[0099] The coreless solid polymer microspheres prepared in Comparative Example 1 did not significantly inhibit the heat of cement hydration, but they could improve the compressive strength of cement stone. The compressive strength of D-1 was 1.4 MPa higher than that of S-1, and also higher than that of S-2 and S-3. This is mainly attributed to the reinforcing and toughening effect of the rigid-flexible shell segments in this invention.

[0100] Due to the lack of self-healing core material, D-1 showed significantly lower strength than the tested cement stone S-(1-5) after the self-healing test, but its self-healing efficiency was higher than D-2 and D-3. D-3, lacking microcapsules, achieved a self-healing efficiency of 24.4%. This is because, during the self-healing test, under the influence of temperature and external forces, microcracks underwent a small amount of self-healing based on secondary hydration and cement interlocking principles.

[0101] The microcapsules in D-2 are low-temperature phase change materials. After rupture, the microcapsules flow into the matrix, preventing secondary hydration of the cement. However, the amino groups on the microcapsule surface can form hydrogen bonds with hydroxyl and carboxyl groups in the cement paste, resulting in a weak self-healing effect. Compared to D-2 and D-3, D-1 does not prevent secondary hydration of the cement, and the hydrogen bonding between the amino groups on the microcapsule surface and the cement is stronger, thus exhibiting a relatively better self-healing effect. The abundant amino groups on the shell surface of this invention can not only react with the epoxy groups of the core material to form a cross-linked structure, but also form hydrogen bonds with the cement, effectively improving the self-healing efficiency of the cement.

[0102] Although the core material and shell structure of the microcapsules used in S-1, S-2, and S-3 are different, their impact on the inhibition of cement hydration heat and the self-healing efficiency of cement stone is not significantly different. This is mainly because the inhibition of hydration heat primarily originates from the phase change of the core material, while the self-healing effect of cement stone is provided by the cross-linking reaction between the epoxy groups of the core material and the amino groups of the shell. The core material structure, component ratio, and shell structure provided by this invention, when working synergistically, can simultaneously achieve the inhibition of cement slurry hydration heat and the self-healing of cement stone.

[0103] Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible subranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed subranges 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 within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.

[0104] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A cement temperature-inhibiting and crack-self-healing microcapsule, characterized in that, The microcapsule includes a core material and a shell material covering the core material; The core material is composed of a phase change epoxy compound and a low phase change temperature material in a mass ratio of (7-9):(1-3); the shell material is formed by free radical polymerization of an amino olefin oil-soluble monomer and a flexible oil-soluble diene monomer. The low phase transition temperature material includes at least one of n-pentadecane, n-tetradecane, ethylene glycol diacetate, pentaerythritol tetrabutyrate, 1-octanol, 1-nonanol, tetradecanol, hexadecyl alcohol, and chlorinated paraffin-52; The phase change epoxy compound includes at least one selected from epoxy stearate glycidyl ester, epoxy palmitate glycidyl ester, 1,2-epoxy octadecane, 1,2-epoxy eicosane and 1,2-epoxy hexadecane. The amino-containing oil-soluble monomers include at least one of p-aminostyrene, 4-aminovinylpyridine, 2-amino-5-vinylthiophene, 1-amino-4-vinylimidazolium, and N-(3-aminobenzyl)maleimide; The flexible oil-soluble diene monomer includes at least one of 1,3-butadiene, isoprene, 1,9-decadiene, and hexanediol diacrylate.

2. The microcapsule according to claim 1, characterized in that, The mass ratio of the amino-containing oil-soluble monomer to the flexible oil-soluble diene monomer is (4-9):(1-2).

3. A method for preparing cement temperature-inhibiting and crack-self-healing microcapsules according to any one of claims 1-2, characterized in that, Includes the following steps: S1. By mass, 70-90 parts of phase change epoxy compound and 10-30 parts of low phase change temperature material are stirred and mixed to obtain microcapsule core material; S2. Take 15-30 parts of the microcapsule core material and 1-8 parts of water-soluble dispersant and stir to disperse in 400-800 parts of water. Add 20-45 parts of amino-based oil-soluble monomer and 5-10 parts of flexible oil-soluble diene monomer, stir for 15-30 minutes to obtain the polymerization system. S3. Dissolve 0.5-3 parts of oil-soluble initiator in 1-5 parts of an amino-olefin-containing oil-soluble monomer to obtain an initiator solution; S4. Add the initiator solution dropwise to the polymerization system, raise the temperature to 70-80°C at a rate of 2-3°C / min, react for 2-4 hours, raise the temperature to 85-90°C, react for 20-30 minutes, and obtain the reaction product; S5. The reaction product is washed by vacuum filtration and dried at 40-70°C to obtain the microcapsules.

4. The method according to claim 3, characterized in that, The water-soluble dispersant in step S2 includes at least one of polyvinyl alcohol 1788, polyethylene glycol with a molecular weight of 4,000-10,000, hydroxypropyl methylcellulose, and polyvinylpyrrolidone with a molecular weight of 8,000-50,000.

5. The method according to claim 3, characterized in that, The oil-soluble initiator in step S3 includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, azobiscyclohexylformitrile, benzoyl peroxide-N,N-dimethylaniline composite initiator system, and potassium persulfate-dodecyl mercaptan initiator system.

6. The method according to claim 3, characterized in that, The specific conditions for stirring and mixing in step S1 are: stirring temperature 30-50℃, stirring speed 200-300r / min, and stirring time 20-40min; the specific conditions for stirring and dispersing in step S2 are: stirring temperature 40-60℃, stirring speed 600-900r / min, and stirring time 10-30min.

7. The application of a cement temperature suppression and crack self-healing microcapsule as described in any one of claims 1-2 in suppressing the temperature rise during cement hydration and self-healing microcracks in cement sheaths.

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