A microencapsulated sustained-release grinding aid, its preparation method and application

Abstract

This invention provides a microencapsulated sustained-release grinding aid, its preparation method, and its application. The preparation method includes the following steps: S1. Preparing the modified grinding aid: Organic alcohol amine and toluene are stirred and mixed, concentrated sulfuric acid is slowly added dropwise, and the reaction yields a crude product. The product is washed and vacuum dried to obtain the modified grinding aid; S2. An initiator and the modified grinding aid obtained in S1 are mixed evenly to obtain a core liquid, which is set aside; amide monomers and crosslinking monomers are mixed evenly in advance to obtain a polymerization reaction solution, which is set aside; S3. Water is used as the reaction base liquid, an emulsifier is added, the temperature is raised, the core liquid and polymerization reaction solution are added, the mixture is stirred, the polymerization reaction is carried out, the mixture is cooled to room temperature, filtered, and a crude product is obtained. The crude product is washed and dried to obtain the microencapsulated sustained-release grinding aid. This microencapsulated sustained-release grinding aid can meet the grinding aid requirements of the grinding production process, without requiring large dosages, and can effectively improve the strength of mortar and concrete at various ages, which is of positive significance for promoting the sustainable development of the construction industry.

Description

Technical Field

[0001] This invention relates to the field of mineral powder and cement grinding aids, and in particular to a microencapsulated sustained-release grinding aid, its preparation method, and its application. Background Technology

[0002] In the preparation of building powders (mineral powder and cement, etc.), grinding is the most critical process. Grinding breaks down the solid particles in the building powder to a suitable particle size, forming a specific particle size distribution to increase the hydration surface area, accelerate the hydration rate, and meet the requirements for cement paste setting and hardening. In the early stages of grinding, the solid particles are relatively large with low specific surface energy, and fine grinding can be achieved without additives. However, as the solid particles gradually become finer during grinding, their specific surface energy gradually increases in the middle and later stages. Some particles have high electrostatic charge, making them prone to electrostatic adsorption and balling, and exhibiting a tendency to re-agglomerate. Adding a small amount of cement grinding aid before grinding, under the dual effects of charge shielding and surface activity of the early-strength agent, can significantly reduce the electrostatic adsorption and balling phenomenon formed during grinding and reduce the re-agglomeration tendency of ultrafine particles, thereby improving grinding efficiency. Cement grinding aids can also significantly improve cement fluidity, enhance the grinding effect of mills and the classification efficiency of air classifiers. As a chemical additive, grinding aids can improve cement particle distribution and stimulate hydration dynamics, thereby improving the early and later strength of cement.

[0003] Currently, conventional grinding aids are organic compounds such as triethanolamine and diethanolamine. Under high temperatures and mechanical grinding conditions, these substances gradually decompose, volatilize, and become ineffective. This leads to a mismatch between the amount of grinding aid and its content and the required amount in the grinding process. Specifically, the grinding aid content is highest in the early stages when it is not needed, but insufficient in the later stages when it is required. This affects grinding efficiency and effectiveness, and weakens the grinding aid's effect on improving powder strength. Furthermore, single-amine and alcohol-based grinding aids have relatively limited functional groups and a narrow range of applicability to materials, thus limiting their grinding effect.

[0004] Chinese patent CN110218017A, "A Novel Modified Cement Grinding Aid and Its Preparation Method", discloses a cement grinding aid including modified triethanolamine. It has good chemical stability, low dosage, and improves the early and later strength of cement. However, the issue of matching the dosage with the demand in the grinding production process has not been studied, and its strength enhancement effect on cement at different ages still needs to be further improved.

[0005] Therefore, it is of great significance to provide a microencapsulated slow-release grinding aid that can improve the strength of cement at all ages, better match the demand in the grinding production process, and enhance the workability of concrete, as well as its preparation method and application. Summary of the Invention

[0006] Given that existing cement grinding aids do not meet the demands of the grinding process and that their strength-enhancing effects on cement at various ages still need further improvement, this invention provides a microcapsule-type slow-release grinding aid, its preparation method, and its application. Using a cross-linked polymer material as the outer shell, and in combination with a specific modified grinding aid, the microcapsule-type slow-release grinding aid is prepared. This imparts good mechanical strength to the microcapsules while providing good hydrophobic and barrier properties, matching the grinding aid requirements of the grinding process. It improves the utilization rate and grinding efficiency of the grinding aid, effectively enhancing the strength of mortar and concrete at various ages without requiring large-scale addition. This makes it suitable for large-scale promotion and industrial production, and has positive significance for promoting the sustainable development of the construction industry.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a microcapsule sustained-release grinding aid includes the following steps:

[0009] S1. Preparation of modified grinding aid: Mix organic alcohol amine and toluene, keep the temperature below 50℃, slowly add concentrated sulfuric acid, react for 1-2 hours, then raise the temperature to 110-120℃ and continue the reaction for 1 hour to obtain crude product, wash 2-3 times, and vacuum dry at 50-70℃ and below 10kPa for 3-6 hours to obtain the modified grinding aid.

[0010] S2. Mix the initiator and the modified grinding aid obtained in S1 evenly to obtain the core liquid, and set aside for use; mix the amide monomer and crosslinking monomer evenly in advance to obtain the polymerization reaction liquid, and set aside for use;

[0011] S3. Using water as the reaction base liquid, add emulsifier, heat to 70-80℃, add core liquid and polymerization reaction liquid, stir at a rate of 1000-1600 rpm, polymerize for 6-10 hours, cool to room temperature, filter to obtain crude product, wash 3-5 times, dry at 50-60℃ for 12-24 hours to obtain the microcapsule sustained-release grinding aid.

[0012] Furthermore, the crosslinking monomer described in S2 is prepared by the following method:

[0013] 1) Add 65-75 parts by weight of 1,4-benzyldiethanol to 600-700 parts by weight of dichloromethane, dissolve evenly at 5°C, and add 110-130 parts by weight of triethylamine to prepare a reaction base solution for later use; add 90-100 parts by weight of acryloyl chloride to 100-200 parts by weight of dichloromethane to prepare a dropping solution for later use;

[0014] 2) The additive solution is added to the reaction base liquid at a uniform rate within 1 hour, and stirring is maintained for 1 hour to obtain the crude crosslinking monomer product. The crude product is washed and filtered three times with saturated sodium chloride solution, and then vacuum dried at 30-40℃ and below 10kPa for 5-8 hours to obtain the crosslinking monomer.

[0015] Furthermore, the organic alcohol amine described in S1 is one or more of triethanolamine, triisopropanolamine, and diethanol monoisopropanolamine.

[0016] Furthermore, the mass ratio of the organic alcohol amine, toluene, and concentrated sulfuric acid in S1 is (149-191):(50-150):300; the washing 2-3 times in S1 refers to washing 2-3 times with a 5% sodium bicarbonate solution and / or a saturated sodium chloride solution.

[0017] Furthermore, the initiator in S2 is one or both of benzoyl peroxide and azobisisobutyronitrile; the amide monomer in S2 is one or more of N,N-di-n-butylacrylamide, N-phenylmethylacrylamide, N-tert-butylacrylamide, and N-tert-butylmethylacrylamide.

[0018] Furthermore, the emulsifier in S3 is one or more of sodium dodecyl sulfonate, sodium dodecyl sulfate, and sodium dodecylbenzene sulfonate.

[0019] Furthermore, the mass ratio of the modified grinding aid, amide monomer, crosslinking monomer, initiator, emulsifier, and water is (10-20):(15-20):(1.5-2.0):(0.05-0.5):(0.2-1.2):(200-250).

[0020] Another object of the present invention is to provide a microencapsulated sustained-release grinding aid.

[0021] A microcapsule sustained-release grinding aid is prepared according to any one of the preceding methods.

[0022] Another object of the present invention is to provide an application of a microencapsulated sustained-release grinding aid.

[0023] Application of the above-mentioned microencapsulated sustained-release grinding aid in cement concrete.

[0024] Furthermore, microencapsulated slow-release grinding aids are added during the preparation of mineral powder and cement, with a dosage of 0.04-0.08%.

[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0026] This invention provides a method for preparing a microcapsule-based sustained-release grinding aid. Addressing the insufficient mechanical strength of traditional microcapsules, a rigid benzene ring crosslinking agent is designed, using a crosslinked polymer material as the shell. This method, combined with a specific modified grinding aid, prepares the microcapsule-based sustained-release grinding aid. This imparts good mechanical strength to the microcapsules while providing excellent hydrophobicity and barrier properties, facilitating stable storage of the grinding aid and meeting the demands of grinding processes. Specifically, under grinding conditions, the microcapsule-based sustained-release grinding aid of this invention ensures no release in the early stages and slow rupture in the middle and later stages, continuously providing grinding aid to the system during grinding. This effectively avoids the problem of high grinding aid consumption in the early stages and poor grinding effect in the later stages, improving the utilization rate and efficiency of the grinding aid. Simultaneously, due to the protective effect of the microcapsules, the modified grinding aid of this invention has a high retention rate in the powder, resulting in a large amount of modified grinding aid remaining in the powder particles. This allows for slow hydrolysis and release of SO4 with an early-strength effect under alkaline conditions. 2- and organic alcohol amines, via SO4 2- It reacts with calcium ions and other components in the system to form an appropriate amount of ettringite, promoting early hydration of the system; the organic alcohol amine has a complexing effect, which can effectively transfer hydration products and promote the hydration reaction in the middle and later stages of the system. This allows the microcapsule slow-release grinding aid of the present invention to effectively improve the strength of mortar and concrete at all ages without the need for large-scale addition, making it suitable for large-scale promotion and industrial production, and has a positive significance for promoting the sustainable development of the construction industry. Detailed Implementation

[0027] To better illustrate the objectives, technical solutions, and advantages of this invention, the following embodiments are provided. Obviously, the following embodiments are only a part of the embodiments of this invention, and not all of them; it should be understood that the embodiments of this invention are only used to illustrate the technical effects of this invention, and not to limit the scope of protection of this invention.

[0028] All raw materials used in the examples are commercially available; unless otherwise specified, the reagents, methods and equipment used in this invention are conventional reagents, methods and equipment in this technical field.

[0029] The crosslinking monomers described in the following examples were all prepared using the following methods:

[0030] 1) Add 69g of 1,4-benzyl diethanol to 650g of dichloromethane and dissolve it evenly at 5℃. Then add 121g of triethylamine to prepare the reaction base solution for later use. Add 90.5g of acryloyl chloride to 138g of dichloromethane to prepare the dropping solution for later use.

[0031] 2) Using a dropping funnel, the liquid is added to the reaction base liquid at a uniform rate over 1 hour, and stirring is maintained for 1 hour to obtain the crude crosslinking monomer product; the crude product is washed and filtered three times with 300g of saturated sodium chloride solution, and dried in a vacuum oven at 32℃ and below 3kPa for 6 hours to obtain the crosslinking monomer RCM.

[0032] Example 1

[0033] A method for preparing a microcapsule sustained-release grinding aid includes the following steps:

[0034] S1. Preparation of modified grinding aid: 149g of triethanolamine and 100g of toluene were added to a three-necked flask and stirred. The temperature was maintained at 40℃, and 300g of concentrated sulfuric acid was slowly added dropwise. After the addition was completed, the reaction was carried out for 1.5h. Then the temperature was raised to 115℃ and the reaction was continued for 1h. The water in the system was removed to improve the reaction yield and obtain the crude product of modified grinding aid. The crude product was washed twice with 50g of 5% sodium bicarbonate solution, and then washed once with saturated 150g of sodium chloride solution. It was then vacuum dried in a vacuum oven at 60℃ and below 8kPa for 4h to obtain the modified grinding aid.

[0035] S2. Mix 0.1g benzoyl peroxide and 15g triethanolamine sulfate evenly to obtain the core solution, and set aside for use; mix 10g N,N-di-n-butylacrylamide and 3g RCM evenly in advance to obtain the polymerization reaction solution, and set aside for use;

[0036] S3. Use 200g of water as the reaction base liquid, add 0.2g of sodium dodecyl sulfonate, heat to 80℃, add core liquid and polymerization reaction liquid, stir at a rate of 1000rpm, polymerize for 8h, cool to room temperature, filter with medium-speed filter paper to obtain crude product, wash 3 times with 100g of water, and dry in a 50℃ forced-air drying oven for 12h to obtain the microcapsule sustained-release grinding aid.

[0037] Example 2

[0038] A method for preparing a microcapsule sustained-release grinding aid includes the following steps:

[0039] S1. Preparation of modified grinding aid: 191g of triisopropanolamine and 100g of toluene were added to a three-necked flask and stirred. The temperature was maintained at 45℃, and 300g of concentrated sulfuric acid was slowly added dropwise. After the addition was completed, the reaction was carried out for 1.5h. Then the temperature was raised to 120℃ and the reaction was continued for 1h to remove water from the system and improve the reaction yield. The crude product of modified grinding aid was obtained. The crude product was washed twice with 50g of 5% sodium bicarbonate solution, and then washed once with saturated 150g of sodium chloride solution. It was then vacuum dried in a vacuum oven at 60℃ and below 7kPa for 4h to obtain the modified grinding aid.

[0040] S2. Mix 0.2g of azobisisobutyronitrile and 20g of triisopropanolamine sulfate evenly to obtain the core liquid, and set aside for use; mix 20g of N-phenylmethylacrylamide and 1g of RCM evenly in advance to obtain the polymerization reaction solution, and set aside for use;

[0041] S3. Use 250g of water as the reaction base liquid, add 0.4g of sodium dodecyl sulfonate, heat to 70℃, add core liquid and polymerization reaction liquid, stir at a rate of 1600rpm, polymerize for 6h, cool to room temperature, filter with medium-speed filter paper to obtain crude product, wash with 100g of water 5 times, dry in a 60℃ forced-air drying oven for 18h to obtain the microcapsule sustained-release grinding aid.

[0042] Example 3

[0043] A method for preparing a microcapsule sustained-release grinding aid includes the following steps:

[0044] S1. Preparation of modified grinding aid: 163g of diethanol monoisopropanolamine and 100g of toluene were added to a three-necked flask and stirred. The temperature was maintained at 30℃, and 300g of concentrated sulfuric acid was slowly added dropwise. After the addition was completed, the reaction was carried out for 1.5h. Then the temperature was raised to 110℃ and the reaction was continued for 1h to remove water from the system and improve the reaction yield. The crude product of modified grinding aid was obtained. The crude product was washed twice with 50g of 5% sodium bicarbonate solution, and then washed once with saturated 150g of sodium chloride solution. It was then vacuum dried in a vacuum oven at 60℃ and below 9kPa for 4h to obtain the modified grinding aid.

[0045] S2. Mix 0.3g benzoyl peroxide and 15g diethanol monoisopropanolamine sulfate evenly to obtain the core liquid, and set aside for use; mix 10g N-tert-butylacrylamide and 3g RCM evenly in advance to obtain the polymerization reaction solution, and set aside for use;

[0046] S3. Use 200g of water as the reaction base liquid, add 0.4g of sodium dodecyl sulfonate, heat to 80℃, add core liquid and polymerization reaction liquid, stir at a rate of 1000rpm, polymerize for 8h, cool to room temperature, filter with medium-speed filter paper to obtain crude product, wash 3 times with 100g of water, and dry in a 50℃ forced-air drying oven for 12h to obtain the microcapsule sustained-release grinding aid.

[0047] Example 4

[0048] A method for preparing a microcapsule sustained-release grinding aid includes the following steps:

[0049] S1. Preparation of modified grinding aid: 191g of triisopropanolamine and 100g of toluene were added to a three-necked flask and stirred. The temperature was maintained at 30℃, and 300g of concentrated sulfuric acid was slowly added dropwise. After the addition was completed, the reaction was carried out for 1.5h. Then the temperature was raised to 115℃ and the reaction was continued for 1h to remove water from the system and improve the reaction yield. The crude product of modified grinding aid was obtained. The crude product was washed twice with 50g of 5% sodium bicarbonate solution, and then washed once with saturated 150g of sodium chloride solution. It was then vacuum dried in a vacuum oven at 60℃ and below 10kPa for 4h to obtain the modified grinding aid.

[0050] S2. Mix 0.5g of azobisisobutyronitrile and 10g of triisopropanolamine sulfate evenly to obtain the core liquid, and set aside for use; mix 20g of N-tert-butylmethacrylamide and 2g of RCM evenly in advance to obtain the polymerization reaction solution, and set aside for use;

[0051] S3. Use 250g of water as the reaction base liquid, add 0.4g of sodium dodecyl sulfonate, heat to 70℃, add core liquid and polymerization reaction liquid, stir at a rate of 1600rpm, polymerize for 6h, cool to room temperature, filter with medium-speed filter paper to obtain crude product, wash with 100g of water 5 times, dry in a 50℃ forced-air drying oven for 24h to obtain the microcapsule sustained-release grinding aid.

[0052] Example 5

[0053] A method for preparing a microcapsule sustained-release grinding aid includes the following steps:

[0054] S1. Preparation of modified grinding aid: 191g of triisopropanolamine and 100g of toluene were added to a three-necked flask and stirred. The temperature was maintained at 30℃, and 300g of concentrated sulfuric acid was slowly added dropwise. After the addition was completed, the reaction was carried out for 1.5h. Then the temperature was raised to 115℃ and the reaction was continued for 1h to remove water from the system and improve the reaction yield. The crude product of modified grinding aid was obtained. The crude product was washed twice with 50g of 5% sodium bicarbonate solution, and then washed once with saturated 150g of sodium chloride solution. It was then vacuum dried in a vacuum oven at 60℃ and below 10kPa for 4h to obtain the modified grinding aid.

[0055] S2. Mix 0.3g benzoyl peroxide and 20g triisopropanolamine sulfate evenly to obtain the core solution, and set aside for use; mix 20g N-tert-butylmethacrylamide and 2g RCM evenly in advance to obtain the polymerization reaction solution, and set aside for use;

[0056] S3. Use 250g of water as the reaction base liquid, add 1.2g of sodium dodecyl sulfonate, heat to 70℃, add core liquid and polymerization reaction liquid, stir at a rate of 1600rpm, polymerize for 6h, cool to room temperature, filter with medium-speed filter paper to obtain crude product, wash with 100g of water 5 times, dry in a 60℃ forced-air drying oven for 18h to obtain the microcapsule sustained-release grinding aid.

[0057] Example 6

[0058] A method for preparing a microcapsule sustained-release grinding aid includes the following steps:

[0059] S1. Preparation of modified grinding aid: 191g of triisopropanolamine and 100g of toluene were added to a three-necked flask and stirred. The temperature was maintained at 30℃, and 300g of concentrated sulfuric acid was slowly added dropwise. After the addition was completed, the reaction was carried out for 1.5h. Then the temperature was raised to 115℃ and the reaction was continued for 1h to remove water from the system and improve the reaction yield. The crude product of modified grinding aid was obtained. The crude product was washed twice with 50g of 5% sodium bicarbonate solution, and then washed once with saturated 150g of sodium chloride solution. It was then vacuum dried in a vacuum oven at 60℃ and below 10kPa for 4h to obtain the modified grinding aid.

[0060] S2. Mix 0.1g of azobisisobutyronitrile and 20g of triisopropanolamine sulfate evenly to obtain the core liquid, and set aside for use; mix 20g of N-tert-butylmethacrylamide and 2g of RCM evenly in advance to obtain the polymerization reaction solution, and set aside for use;

[0061] S3. Use 250g of water as the reaction base liquid, add 0.4g of sodium dodecyl sulfonate, heat to 70℃, add core liquid and polymerization reaction liquid, stir at a rate of 1600rpm, polymerize for 6h, cool to room temperature, filter with medium-speed filter paper to obtain crude product, wash with 100g of water 5 times, dry in a 60℃ forced-air drying oven for 18h to obtain the microcapsule sustained-release grinding aid.

[0062] Comparative Example 1

[0063] Use commercially available triisopropanolamine cement grinding aid.

[0064] Comparative Example 2

[0065] Use commercially available triethanolamine sulfate cement grinding aid.

[0066] Comparative Example 3

[0067] Use commercially available diethanol monoisopropanolamine sulfate cement grinding aid.

[0068] Comparative Example 4

[0069] Use commercially available triisopropanolamine sulfate cement grinding aid.

[0070] Comparative Example 5

[0071] A method for preparing a cement grinding aid includes the following steps:

[0072] S1. Preparation of modified grinding aid: 191g of triisopropanolamine and 100g of toluene were added to a three-necked flask and stirred. The temperature was maintained at 30℃, and 300g of concentrated sulfuric acid was slowly added dropwise. After the addition was completed, the reaction was carried out for 1.5h. Then the temperature was raised to 115℃ and the reaction was continued for 1h to remove water from the system and improve the reaction yield. The crude product of modified grinding aid was obtained. The crude product was washed twice with 50g of 5% sodium bicarbonate solution, and then washed once with saturated 150g of sodium chloride solution. It was then vacuum dried in a vacuum oven at 60℃ and below 10kPa for 4h to obtain the modified grinding aid.

[0073] S2. Mix 0.1g of azobisisobutyronitrile and 20g of triisopropanolamine sulfate evenly to obtain the core liquid, and set aside for use; mix 20g of N-tert-butylmethacrylamide and 2g of ethylene glycol dimethacrylate evenly in advance to obtain the polymerization reaction solution, and set aside for use;

[0074] S3. Use 250g of water as the reaction base liquid, add 0.4g of sodium dodecyl sulfonate, heat to 70℃, add core liquid and polymerization reaction liquid, stir at a rate of 1600rpm, polymerize for 6h, cool to room temperature, filter with medium-speed filter paper to obtain crude product, wash with 100g of water 5 times, dry in a 60℃ forced-air drying oven for 18h to obtain the microcapsule sustained-release grinding aid.

[0075] Compared with Example 6, the main difference in this comparative example is that S2 uses ethylene glycol dimethacrylate instead of the crosslinking monomer.

[0076] Performance tests were conducted on the above embodiments and comparative examples. The experimental test methods are as follows:

[0077] The above embodiments and comparative examples were tested for cement standard consistency water content, specific surface area, cement mortar strength, and concrete. Detailed methods were referred to GB / T 26748-2011 "Cement Grinding Aids", GB / T 8074-2008 "Determination of Specific Surface Area of ​​Cement - Blaine Method", GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)" and GB / T 18046-2017 "Granulated Blast Furnace Slag Powder for Cement, Mortar and Concrete".

[0078] Cement mix proportion (mass fraction, %): 78% cement clinker, 4% gypsum, 9% mineral powder and 9% fly ash. A Φ500×500 ball mill was used, with a grinding aid dosage of 0.06% and a grinding time of 30 min.

[0079] The mineral powder ratio (mass ratio) is m(water slag):m(grinding aid) = 10000:6.

[0080] The results are shown below:

[0081] Table 1. Specific surface area and strength of cement prepared in the examples and comparative examples.

[0082]

[0083]

[0084] As shown in Table 1, under the same admixture dosage, the specific surface area of ​​cement in the blank group without added grinding aid was 351.6 m². 2 / kg, the specific surface area of ​​the cement in Examples 1-6 is all higher than 390m². 2 / kg, an increase of 43m compared to the control group 2 The presence of a concentration of over / kg indicates that the microencapsulated slow-release grinding aid of the present invention helps to increase the specific surface area of ​​cement and improve grinding efficiency. Furthermore, among the key strength indicators of cement, the 3-day and 28-day flexural strengths of the blank group were 5.2 MPa and 8.4 MPa, respectively, and the 3-day and 28-day compressive strengths were 23.5 MPa and 44.3 MPa, respectively. The 3-day and 28-day flexural strengths of Examples 1-6 were higher than 6.5 MPa and 9.5 MPa, respectively, and the 3-day and 28-day compressive strengths were higher than 27 MPa and 50 MPa, respectively, indicating that the microencapsulated slow-release grinding aid of the present invention can significantly improve the strength of cement at all ages.

[0085] Comparative Examples 1-4, using commercially available cement grinding aids, showed only moderate improvements in cement specific surface area, flexural strength, and compressive strength. The cement specific surface area did not exceed 375 m² / kg, the 3-day and 28-day flexural strengths did not exceed 6 MPa and 9 MPa, and the 3-day and 28-day compressive strengths did not exceed 26 MPa and 48 MPa, respectively. Comparative Example 5, using ethylene glycol dimethacrylate instead of the crosslinking monomer, yielded a cement grinding aid consisting of non-rigid microcapsules encapsulated triisopropanolamine sulfate, corresponding to a cement specific surface area of ​​373.6 m² / kg. 2 / kg corresponds to a 3d / 28d flexural strength of 5.5 / 8.6 MPa and a 3d / 28d compressive strength of 26.1 / 47.5 MPa for cement. Although the 3d compressive strength is slightly higher than other comparative examples, the overall data is far inferior to those of the various embodiments. This indicates that the rigid microcapsule structure of the microcapsule-type slow-release grinding aid in this application ensures that it does not release in the early stage, but slowly breaks down in the middle and later stages to gradually release the grinding aid. This ensures the continuous release of components that promote hydration reaction, which helps to increase the specific surface area of ​​cement, improve grinding efficiency, and increase the strength of cement at all ages.

[0086] Table 2 Specific surface area, strength and activity of slag powder

[0087]

[0088]

[0089] Table 2 shows that, under the same dosage, the specific surface area of ​​the blank group of mineral powder without added grinding aid is 401.9 m². 2 / kg, the specific surface area of ​​the cement in Examples 1-6 is all higher than 440m². 2 / kg, an increase of 41m compared to the control group 2 The presence of values ​​above / kg indicates that the microencapsulated sustained-release grinding aid of the present invention helps to increase the specific surface area of ​​mineral powder and improve grinding efficiency. Furthermore, in terms of the strength and activity indices of the mineral powder, the 7-day compressive strength and activity index of the blank group were 32.1 MPa and 75.1%, respectively, and the 28-day compressive strength and activity index were 46.5 MPa and 96.2%, respectively. The 7-day compressive strength and activity index of Examples 1-6 were higher than 36 MPa and 85%, respectively, and the 28-day compressive strength and activity index were higher than 56 MPa and 115%, respectively. This demonstrates that the microencapsulated sustained-release grinding aid of the present invention can significantly improve the strength and activity of mineral powder at various ages.

[0090] Comparative Examples 1-4, which used commercially available cement grinding aids, showed only moderate effects on improving the specific surface area, compressive strength, and activity index of the mineral powder, with the specific surface area of ​​the mineral powder not exceeding 425 m². 2 / kg, the 7-day compressive strength and activity index are no higher than 35 MPa and 81%, respectively; the 28-day compressive strength and activity index are no higher than 50 MPa and 105%, respectively. In contrast, Comparative Example 5 used ethylene glycol dimethacrylate to replace the crosslinking monomer, resulting in a cement grinding aid that was a non-rigid microcapsule-encapsulated triisopropanolamine sulfate with a corresponding specific surface area of ​​423.5 m². 2 / kg, corresponding to a 7d / 28d compressive strength of 34.8 / 49.8 MPa, and a 7d / 28d activity index of 81.3 / 103.1%, which is far inferior to that of the various embodiments. This indicates that the rigid microcapsule structure of the microcapsule-type sustained-release grinding aid of this application can ensure that it does not release in the early stage, but slowly breaks down in the middle and later stages to gradually release the grinding aid. This ensures the continuous release of components that promote hydration reaction, which helps to increase the specific surface area of ​​mineral powder, improve grinding efficiency, and increase the strength and activity of mineral powder at all ages.

[0091] In summary, this invention prepares a microcapsule-based sustained-release grinding aid by using a cross-linked polymer material as the outer shell and combining it with a specific modified grinding aid. This endows the microcapsules with good mechanical strength and excellent hydrophobic and barrier properties, which helps to stably preserve the grinding aid. It matches the grinding aid requirements of the grinding production process, continuously providing grinding aid to the system during grinding, effectively avoiding the problems of high grinding aid consumption in the early stages and poor grinding effect in the later stages, thus improving the utilization rate and efficiency of the grinding aid. Simultaneously, it ensures a high retention rate of the modified grinding aid in the powder, enabling it to slowly hydrolyze and release SO4 with early-strength effects under alkaline conditions. 2- and organic alcohol amines, via SO4 2- It reacts with calcium ions and other components in the system to form an appropriate amount of ettringite, promoting early hydration of the system; organic alcohol amines have a complexing effect, which can effectively transfer hydration products, promote the hydration reaction in the middle and later stages of the system, effectively improve the strength of mortar and concrete at all ages, and are suitable for large-scale promotion and industrial production, which is of positive significance for promoting the sustainable development of the construction industry.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A process for the preparation of microencapsulated sustained release grinding aid characterized in that, Comprising the following steps: S1. Preparation of modified grinding aid: stirring and mixing organic alcohol amine and toluene, keeping the temperature less than 50℃, slowly adding concentrated sulfuric acid, reacting for 1-2 h, then warming to 110-120℃, continuing to react for 1 h, obtaining the crude product, washing 2-3 times, drying at 50-70℃ under vacuum below 10 kPa for 3-6 h, obtaining the modified grinding aid; S2. Mixing initiator and the modified grinding aid obtained in S1 uniformly to obtain core liquid, ready for use; mixing amide monomer and crosslinking monomer in advance to obtain polymerization reaction liquid, ready for use; S3. Adding water as reaction bottom liquid, adding emulsifier, warming to 70-80℃, adding core liquid and polymerization reaction liquid, keeping the stirring rate at 1000-1600 rpm, polymerization reaction for 6-10 h, cooling to room temperature, filtering to obtain crude product, washing 3-5 times, drying at 50-60℃ for 12-24 h, obtaining the microcapsule slow-release grinding aid; The crosslinking monomer in S2 is prepared by the following method: 1) Adding 65-75 parts by mass of 1,4-benzene dimethanol into 600-700 parts by mass of dichloromethane, dissolving uniformly at 5℃, and adding 110-130 parts by mass of triethylamine to prepare reaction bottom liquid, ready for use; adding 90-100 parts by mass of acryloyl chloride into 100-200 parts by mass of dichloromethane to prepare dropwise liquid, ready for use; 2) Dropping the dropwise liquid into the reaction bottom liquid at a uniform speed within 1 h, keeping stirring for 1 h to obtain the crosslinking monomer crude product, washing and filtering the crude product 3 times with saturated sodium chloride solution, drying at 30-40℃ under vacuum below 10 kPa for 5-8 h, obtaining the crosslinking monomer.

2. A process for the preparation of the microencapsulated, slow release grinding aid according to claim 1, characterized in that, The organic alcohol amine in S1 is one or more of triethanolamine, triisopropanolamine and diethanol monoisopropanolamine.

3. A process for the preparation of the microencapsulated sustained release grinding aid according to claim 1, characterized in that, The mass ratio of the organic alcohol amine, toluene and concentrated sulfuric acid in S1 is (149-191):(50-150):300; the washing 2-3 times in S1 is washing 2-3 times with 5% sodium bicarbonate solution and / or saturated sodium chloride solution.

4. A process for the preparation of the microencapsulated sustained release grinding aid according to claim 1, characterized in that, The initiator in S2 is one or both of peroxobenzoyl and azobis isobutyronitrile; the amide monomer in S2 is one or more of N,N-di-n-butyl acrylamide, N-phenyl methyl acrylamide, N-tert-butyl acrylamide and N-tert-butyl methyl acrylamide.

5. A process for the preparation of the microencapsulated sustained release grinding aid according to claim 1, characterized in that, The emulsifier in S3 is one or more of sodium dodecyl sulfonate, sodium dodecyl sulfate and sodium dodecyl benzene sulfonate.

6. A process for the preparation of the microencapsulated sustained release grinding aid according to claim 1, characterized in that, The mass ratio of the modified grinding aid, amide monomer, crosslinking monomer, initiator, emulsifier and water is (10-20):(15-20):(1.5-2.0):(0.05-0.5):(0.2-1.2):(200-250).

7. A microencapsulated, slow-release grinding aid characterized in that, Prepared according to the preparation method in any one of claims 1-6.

8. Application of the microcapsule slow-release grinding aid in claim 7 in cement concrete.

9. Use of the microencapsulated release-type grinding aid according to claim 8 in cement concrete, characterized in that, The microcapsule slow-release grinding aid is added in the preparation of mineral powder and cement, and the dosage is 0.04-0.08%.

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