Microcapsule sustained-release grinding aid as well as preparation method and application thereof

Abstract

The invention provides a microcapsule slow-release grinding aid as well as a preparation method and application thereof, the preparation method comprises the following steps: S1, preparation of a modified grinding aid: stirring and mixing organic alcohol amine and toluene, slowly dropwise adding concentrated sulfuric acid, reacting to obtain a crude product, washing, and drying in vacuum to obtain the modified grinding aid; s2, uniformly mixing an initiator and the modified grinding aid obtained in the step S1 to obtain core liquid for later use; the preparation method comprises the following steps: uniformly mixing an amide monomer and a crosslinking monomer in advance to obtain a polymerization reaction solution for later use; s3, taking water as a reaction base solution, adding an emulsifier, heating, adding the core solution and the polymerization reaction solution, stirring, carrying out polymerization reaction, cooling to room temperature, filtering to obtain a crude product, washing, and drying to obtain the microcapsule slow-release grinding aid. The microcapsule slow-release grinding aid can meet the requirement of a grinding production process on the grinding aid, can effectively improve the strength of mortar and concrete at each age without large-dosage addition, and has positive significance in promoting the sustainable development of the building industry.

Description

Technical Field

[0001] The invention relates to the technical field of mineral powder and cement grinding aids, and in particular to a microcapsule sustained-release grinding aid and a preparation method and application thereof. Background Art

[0002] In the preparation process of building powder (mineral powder and cement, etc.), grinding is the most critical process. Through grinding, the solid particles in the building powder are ground to a suitable particle size to form a certain particle gradation to increase its hydration area, accelerate the hydration rate, and meet the requirements of cement paste coagulation and hardening. In the early stage of grinding, the solid particles are large and the specific surface energy is small, and the fine grinding effect can be achieved without additives; as the solid particles gradually become finer during the grinding process, the specific surface energy of the particles gradually increases in the middle and late stages, and some particles have high static electricity on the surface, which is easy to form static adsorption and balling phenomenon, and has a tendency to re-agglomerate. Adding a small amount of cement grinding aid before grinding can greatly reduce the static adsorption and balling phenomenon formed during the grinding process under the dual effects of the charge shielding and surface active properties of the early strength agent, and can reduce the re-agglomeration tendency of the ultrafine particles formed during the grinding process, thereby improving the grinding efficiency. Cement grinding aids can also significantly improve cement fluidity, enhance the grinding effect of the mill and the powder selection efficiency of the powder classifier. As a chemical additive, grinding aids can improve the distribution of cement particles and stimulate hydration dynamics, thereby improving the early and later strength of cement.

[0003] At present, conventional grinding aids are organic grinding aids such as triethanolamine and diethanolamine. Under high temperature and mechanical grinding environment, the grinding aid molecules of these substances will slowly decompose, volatilize and become ineffective, resulting in the problem that the grinding aid content does not match the demand in the grinding production process, that is, in the early stage when the grinding aid is not needed, the grinding aid content is the highest, and in the middle and late stages when the grinding aid is needed, the grinding aid content is insufficient, which affects the efficiency and effect of the grinding and weakens the effect of the grinding aid on improving the strength of the powder. In addition, the functional groups of single alcohol amine and alcohol compound grinding aids are relatively single, and the application range of materials is relatively narrow, which limits the grinding effect.

[0004] Chinese patent CN110218017A "A new type of modified cement grinding aid and its preparation method" discloses a cement grinding aid including modified triethanolamine, which has good chemical stability, low addition amount, and improves the early strength and late strength of cement. However, the problem of matching with the demand in the grinding production process is not studied, and its strength enhancement effect on cement at all ages still needs to be further improved.

[0005] Therefore, it is of great significance to provide a microcapsule sustained-release grinding aid, which can not only improve the strength of cement at all ages, but also better match the demand in the grinding production process and improve the working performance of concrete, as well as its preparation method and application. Summary of the invention

[0006] In view of the fact that the existing cement grinding aids do not match the demand in the grinding production process, and the strength enhancement effect of cement at various ages still needs to be further improved, the present invention provides a microcapsule sustained-release grinding aid and a preparation method and application thereof. The microcapsule sustained-release grinding aid is prepared by using a cross-linked polymer material as an outer shell and cooperating with a specific modified grinding aid. The microcapsule is endowed with good mechanical strength and provides better hydrophobic and insulating effects, matching the demand for grinding aids in the grinding production process, improving the utilization rate of the grinding aid and the efficiency of the grinding aid, and can effectively improve the strength of mortar and concrete at various ages without the need for large-scale addition. The microcapsule sustained-release grinding aid is suitable for large-scale promotion and industrialized production, and has positive significance for promoting the sustainable development of the construction industry.

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

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

[0009] S1. Preparation of modified grinding aid: Mix the organic alcohol amine and toluene, keep the temperature below 50 ° C, slowly add concentrated sulfuric acid, react for 1-2h, then raise the temperature to 110-120 ° C, continue the reaction for 1h to obtain a crude product, wash 2-3 times, 50-70 ° C, 10kPa or less vacuum drying for 3-6h to obtain the modified grinding aid;

[0010] S2. The initiator and the modified grinding aid obtained in S1 are mixed uniformly to obtain a core liquid for use; the amide monomer and the cross-linking monomer are mixed uniformly in advance to obtain a polymerization reaction liquid for use;

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

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

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

[0014] 2) adding the dropwise addition liquid to the reaction base liquid at a uniform speed within 1 hour, and stirring is continued for 1 hour to obtain a cross-linking monomer crude product, washing and filtering the crude product 3 times with a saturated sodium chloride solution, and drying under vacuum at 30-40° C. and below 10 kPa for 5-8 hours to obtain the cross-linking 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; and the washing 2-3 times in S1 is washing 2-3 times with 5% sodium bicarbonate solution and / or saturated sodium chloride solution.

[0017] Furthermore, the initiator described in S2 is one or both of benzoyl peroxide and azobisisobutyronitrile; the amide monomer described 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 described 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, cross-linking 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 microcapsule sustained-release grinding aid.

[0021] A microcapsule sustained-release grinding aid is prepared according to any of the above-mentioned preparation methods.

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

[0023] An application of the above-mentioned microcapsule sustained-release grinding aid in cement concrete.

[0024] Furthermore, when preparing mineral powder and cement, microcapsule sustained-release grinding aid is added in an amount of 0.04-0.08%.

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

[0026] The present invention provides a method for preparing a microcapsule sustained-release grinding aid. Aiming at the insufficient mechanical strength of traditional microcapsules, a cross-linking agent with a rigid benzene ring structure is designed, and a cross-linked polymer material is used as the shell. The microcapsule sustained-release grinding aid is prepared in combination with a specific modified grinding aid, which not only gives the microcapsules good mechanical strength, but also provides good hydrophobic and isolation effects, which helps to stably store the grinding aid and matches the demand for grinding aids in the grinding production process. That is, under the action of grinding, the microcapsule sustained-release grinding aid of the present invention can ensure that it is not released in the early stage, and slowly breaks in the middle and late stages, and can continuously provide grinding aids to the system during the grinding process, effectively avoiding the problem of large consumption of grinding aids in the early stage of grinding and poor grinding aid effect in the later stage, thereby improving the utilization rate of the grinding aid and the efficiency of the grinding aid. At the same time, due to the protective effect of the microcapsules, the retention rate of the modified grinding aid of the present invention in the powder is guaranteed to be high, and the amount of the modified grinding aid remaining in the powder particles is large, and it can be slowly hydrolyzed in an alkaline environment to release SO4 with early strength effect. 2- and organic alcohol amines, through SO4 2- It generates an appropriate amount of calcium aluminate with components such as calcium ions in the system to promote the early hydration of the system; the organic alcohol amine has a complexing effect, can effectively transfer the hydration products, and promote the hydration reaction in the middle and late stages of the system, so that the microcapsule sustained-release grinding aid of the present invention does not need to be added in a large amount, and can also effectively improve the strength of mortar and concrete at all ages. It is suitable for large-scale promotion and industrial production, and has positive significance for promoting the sustainable development of the construction industry. DETAILED DESCRIPTION

[0027] In order to better illustrate the purpose, technical scheme and advantages of the present invention, the present invention is further described by the following examples. Obviously, the following examples are only part of the embodiments of the present invention, rather than all the embodiments; it should be understood that the embodiments of the present invention are only used to illustrate the technical effects of the present invention, rather than to limit the scope of protection of the present invention.

[0028] The raw materials in the examples can all be obtained commercially; unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0029] The cross-linking monomers described in the following examples are all prepared by the following preparation method:

[0030] 1) Add 69g of 1,4-benzenedimethanol to 650g of dichloromethane, dissolve evenly at 5°C, and add 121g of triethylamine to prepare a reaction base liquid for standby use; add 90.5g of acryloyl chloride to 138g of dichloromethane to prepare a drop solution for standby use;

[0031] 2) using a dropping funnel, uniformly dropping the droplet into the reaction base liquid within 1 hour, and stirring for 1 hour to obtain a cross-linking monomer crude product; using 300 g of a saturated sodium chloride solution to wash and filter the crude product 3 times, and drying it in a vacuum oven at 32° C. and below 3 kPa for 6 hours to obtain the cross-linking monomer RCM.

[0032] Example 1

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

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

[0035] S2 0.1g benzoyl peroxide and 15g triethanolamine sulfate were mixed to obtain a core liquid for use; 10gN, N- di-n-butyl acrylamide and 3g RCM were mixed in advance to obtain a polymerization reaction solution for use;

[0036] S3. Use 200g of water as the reaction base liquid, add 0.2g of sodium dodecyl sulfate, raise the temperature to 80°C, add the core liquid and the polymerization reaction liquid, maintain stirring at a rate of 1000rpm, perform the polymerization reaction for 8h, cool to room temperature, filter with medium-speed filter paper to obtain a crude product, wash it 3 times with 100g of water, and dry it in a 50°C 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 comprises the following steps:

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

[0040] S2 0.2g of azobisisobutyronitrile and 20g of triisopropanolamine sulfate were mixed to obtain a core liquid for use; 20g of N-phenylmethyl acrylamide and 1g of RCM were mixed in advance to obtain a polymerization reaction solution for use;

[0041] S3. Use 250g of water as the reaction base liquid, add 0.4g of sodium dodecyl sulfate, raise the temperature to 70°C, add the core liquid and the polymerization reaction liquid, maintain stirring at a rate of 1600rpm, perform the polymerization reaction for 6h, cool to room temperature, filter with medium-speed filter paper to obtain a crude product, wash 5 times with 100g of water, and dry in a 60°C 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 comprises 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 and mixed, the temperature was maintained at 30°C, 300g of concentrated sulfuric acid was slowly added dropwise, and the reaction was completed for 1.5h, and then the temperature was raised to 110°C, and the reaction was continued for 1h, and the water in the system was removed to improve the reaction yield to obtain a crude modified grinding aid. The crude product was washed twice with 50g of 5% sodium bicarbonate solution, and then washed once with a saturated 150g sodium chloride solution, and vacuum dried in a vacuum oven at 60°C and 9kPa or less for 4h to obtain the modified grinding aid;

[0045] S2 0.3g of benzoyl peroxide and 15g of diethanol monoisopropanolamine sulfate were mixed to obtain a core liquid for use; 10g of N- tert-butyl acrylamide and 3g of RCM were mixed in advance to obtain a polymerization reaction solution for use;

[0046] S3. Use 200g of water as the reaction base liquid, add 0.4g of sodium dodecyl sulfate, raise the temperature to 80°C, add the core liquid and the polymerization reaction liquid, maintain stirring at a rate of 1000rpm, perform the polymerization reaction for 8h, cool to room temperature, filter with medium-speed filter paper to obtain a crude product, wash it 3 times with 100g of water, and dry it in a 50°C 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 comprises the following steps:

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

[0050] S2 0.5g of azobisisobutyronitrile and 10g of triisopropanolamine sulfate were mixed to obtain a core liquid for use; 20g of N- tert-butyl methacrylamide and 2g of RCM were mixed in advance to obtain a polymerization reaction solution for use;

[0051] S3. Use 250g of water as the reaction base liquid, add 0.4g of sodium dodecyl sulfate, raise the temperature to 70°C, add the core liquid and the polymerization reaction liquid, maintain stirring at a rate of 1600rpm, perform the polymerization reaction for 6h, cool to room temperature, filter with medium-speed filter paper to obtain a crude product, wash 5 times with 100g of water, and dry in a 50°C 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 comprises the following steps:

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

[0055] S2 0.3g of benzoyl peroxide and 20g of triisopropanolamine sulfate were mixed to obtain a core liquid for use; 20g of N- tert-butyl methacrylamide and 2g of RCM were mixed in advance to obtain a polymerization reaction solution for use;

[0056] S3. Use 250g of water as the reaction base liquid, add 1.2g of sodium dodecyl sulfate, raise the temperature to 70°C, add the core liquid and the polymerization reaction liquid, maintain stirring at a rate of 1600rpm, perform the polymerization reaction for 6h, cool to room temperature, filter with medium-speed filter paper to obtain a crude product, wash it 5 times with 100g of water, and dry it in a 60°C 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 comprises the following steps:

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

[0060] S2 0.1g of azobisisobutyronitrile and 20g of triisopropanolamine sulfate were mixed to obtain a core liquid for use; 20g of N- tert-butyl methacrylamide and 2g of RCM were mixed in advance to obtain a polymerization reaction solution for use;

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

[0062] Comparative Example 1

[0063] Commercially available triisopropanolamine cement grinding aid was used.

[0064] Comparative Example 2

[0065] Commercially available triethanolamine sulfate cement grinding aid was used.

[0066] Comparative Example 3

[0067] Commercially available diethanol monoisopropanolamine sulfate cement grinding aid was used.

[0068] Comparative Example 4

[0069] Commercially available triisopropanolamine sulfate cement grinding aid was used.

[0070] Comparative Example 5

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

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

[0073] S2 0.1g of azobisisobutyronitrile and 20g of triisopropanolamine sulfate were mixed to obtain a core liquid for use; 20g of N- tert-butyl methacrylamide and 2g of ethylene glycol dimethacrylate were mixed in advance to obtain a polymerization reaction solution for use;

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

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

[0076] The above embodiments and comparative examples were subjected to performance tests, and the experimental test methods were as follows:

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

[0078] Cement ratio (mass fraction, %): 78% cement clinker, 4% gypsum, 9% mineral powder and 9% fly ash. A Φ500×500 ball mill was used, the amount of grinding aid was 0.06%, and the grinding time was 30 minutes.

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

[0080] The result is as follows:

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

[0082]

[0083]

[0084] It can be seen from Table 1 that at the same dosage, the specific surface area of ​​cement in the blank group without adding grinding aid is 351.6m 2 / kg, the specific surface areas of cements in Examples 1-6 are all higher than 390m 2 / kg, an increase of 43m compared with the blank group 2 / kg or more, indicating that the microcapsule sustained-release grinding aid of the present invention is helpful to increase the specific surface area of ​​cement and improve the efficiency of grinding. In addition, among the key strength indicators of cement, the 3d and 28d flexural strengths of the blank group were 5.2MPa and 8.4MPa, respectively, and the 3d and 28d compressive strengths were 23.5MPa and 44.3MPa, respectively. The 3d and 28d flexural strengths of Examples 1-6 were higher than 6.5MPa and 9.5MPa, respectively, and the 3d and 28d compressive strengths were higher than 27MPa and 50MPa, respectively, indicating that the microcapsule sustained-release grinding aid of the present invention can significantly improve the strength of cement at all ages.

[0085] Comparative Examples 1-4 use commercially available cement grinding aids, which have a relatively general effect on improving the specific surface area, flexural strength and compressive strength of cement. The specific surface area of ​​cement is not higher than 375m2 / kg, the 3d and 28d flexural strengths are not higher than 6MPa and 9MPa, and the 3d and 28d compressive strengths are not higher than 26MPa and 48MPa; while Comparative Example 5 uses ethylene glycol dimethacrylate to replace the cross-linking monomer, and the obtained cement grinding aid is triisopropanolamine sulfate encapsulated in non-rigid microcapsules, corresponding to a specific surface area of ​​cement of 373.6m2 / kg. 2 / kg, the corresponding 3d / 28d flexural strength of cement is 5.5 / 8.6MPa, and the corresponding 3d / 28d compressive strength of cement is 26.1 / 47.5MPa. Although the 3d compressive strength is slightly higher than that of other comparative examples, the comprehensive data is far from comparable with the embodiments. It shows that the rigid microcapsule structure of the microcapsule sustained-release grinding aid of the present application can ensure that it is not released in the early stage, slowly breaks in the middle and late stages, and gradually releases the grinding aid, which can ensure the continuous release of the components that promote the hydration reaction, help to increase the specific surface area of ​​cement, improve the efficiency of grinding, and increase the strength of cement at all ages.

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

[0087]

[0088]

[0089] It can be seen from Table 2 that at the same dosage, the specific surface area of ​​the blank group ore powder without adding grinding aid is 401.9m 2 / kg, the specific surface areas of cements in Examples 1-6 are all higher than 440m 2 / kg, an increase of 41m compared with the blank group 2 / kg or more, indicating that the microcapsule sustained-release grinding aid of the present invention is helpful to increase the specific surface area of ​​the mineral powder and improve the efficiency of grinding. In addition, among the strength and activity indicators of the mineral powder, the 7d compressive strength and activity index of the blank group were 32.1MPa and 75.1%, and the 28d compressive strength and activity index were 46.5MPa and 96.2%, respectively. The 7d compressive strength and activity index of Examples 1-6 were higher than 36MPa and 85%, and the 28d compressive strength and activity index were higher than 56MPa and 115%, respectively, indicating that the microcapsule sustained-release grinding aid of the present invention can significantly improve the strength and activity of mineral powder at all ages.

[0090] In contrast, the commercially available cement grinding aids used in Examples 1-4 had a relatively general effect on the improvement of the specific surface area, compressive strength and activity index of the mineral powder, and the specific surface area of ​​the mineral powder was no more than 425 m 2 / kg, 7d compressive strength and activity index are not higher than 35MPa and 81%, 28d compressive strength and activity index are not higher than 50MPa and 105%; while in comparative example 5, ethylene glycol dimethacrylate is used to replace the crosslinking monomer, and the obtained cement grinding aid is triisopropanolamine sulfate encapsulated in non-rigid microcapsules, and the corresponding specific surface area is 423.5m 2 / kg, the corresponding 7d / 28d compressive strength is 34.8 / 49.8MPa, and the corresponding 7d / 28d activity index is 81.3 / 103.1%, which is far from comparable with the embodiments. It shows that the rigid microcapsule structure of the microcapsule sustained-release grinding aid of the present application can ensure that it is not released in the early stage, slowly breaks in the middle and late stages, and gradually releases the grinding aid, which can ensure the continuous release of the components that promote the hydration reaction, help to increase the specific surface area of ​​the mineral powder, improve the efficiency of grinding, and increase the strength and activity of the mineral powder at each age.

[0091] In summary, the present invention uses a cross-linked polymer material as the shell and prepares a microcapsule sustained-release grinding aid in combination with a specific modified grinding aid, which gives the microcapsule good mechanical strength and good hydrophobic and insulating effects, helps to stably preserve the grinding aid, matches the demand for grinding aids in the powder grinding production process, and can continuously provide grinding aids to the system during the grinding process, effectively avoiding the problem of large grinding aid consumption in the early stage of grinding and poor grinding aid effect in the later stage, thereby improving the utilization rate of the grinding aid and the efficiency of the grinding aid. At the same time, it ensures that the modified grinding aid of the present invention has a high retention rate in the powder, and can slowly hydrolyze in an alkaline environment to release SO4 with an early strength effect. 2- and organic alcohol amines, through SO4 2- It generates an appropriate amount of calcium aluminate with the calcium ions and other components in the system to promote the early hydration of the system; organic alcohol amines have a complexing effect, can effectively transfer hydration products, promote the hydration reaction in the middle and late stages of the system, and effectively improve the strength of mortar and concrete at all ages. It is suitable for large-scale promotion and industrial production, and has 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 solution of the present invention, rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing a microcapsule sustained-release grinding aid, characterized in that: The following steps are involved: S1. Preparation of modified grinding aid: Mix the organic alcohol amine and toluene, keep the temperature below 50 ° C, slowly add concentrated sulfuric acid, react for 1-2h, then raise the temperature to 110-120 ° C, continue the reaction for 1h to obtain a crude product, wash 2-3 times, 50-70 ° C, 10kPa or less vacuum drying for 3-6h to obtain the modified grinding aid; S2. The initiator and the modified grinding aid obtained in S1 are mixed uniformly to obtain a core liquid for use; the amide monomer and the cross-linking monomer are mixed uniformly in advance to obtain a polymerization reaction liquid for use; S3. Use water as the reaction base liquid, add emulsifier, heat to 70-80°C, add core liquid and polymerization reaction liquid, maintain stirring at a rate of 1000-1600rpm, perform polymerization reaction for 6-10h, cool to room temperature, filter to obtain a crude product, wash 3-5 times, and dry at 50-60°C for 12-24h to obtain the microcapsule sustained-release grinding aid.

2. A method for preparing the microcapsule sustained-release grinding aid according to claim 1, characterized in that: The cross-linking monomer S2 is prepared by the following method: 1) Add 65-75 parts by mass of 1,4-benzenedimethanol to 600-700 parts by mass of dichloromethane, dissolve evenly at 5° C., and add 110-130 parts by mass of triethylamine to prepare a reaction base liquid for standby use; add 90-100 parts by mass of acryloyl chloride to 100-200 parts by mass of dichloromethane to prepare a drop solution for standby use; 2) adding the dropwise addition liquid to the reaction base liquid at a uniform speed within 1 hour, and stirring is continued for 1 hour to obtain a cross-linking monomer crude product, washing and filtering the crude product 3 times with a saturated sodium chloride solution, and drying under vacuum at 30-40° C. and below 10 kPa for 5-8 hours to obtain the cross-linking monomer.

3. A method for preparing the microcapsule sustained-release grinding aid according to claim 1, characterized in that: The organic alcohol amine described in S1 is one or more of triethanolamine, triisopropanolamine and diethanol monoisopropanolamine.

4. A method for preparing the microcapsule 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.

5. A method for preparing the microcapsule sustained-release grinding aid according to claim 1, characterized in that: The initiator described in S2 is one or two of benzoyl peroxide and azobisisobutyronitrile; the amide monomer described in S2 is one or more of N,N-di-n-butylacrylamide, N-phenylmethylacrylamide, N-tert-butylacrylamide, and N-tert-butylmethylacrylamide.

6. A method for preparing the microcapsule sustained-release grinding aid according to claim 1, characterized in that: S3 The emulsifier is one or more of sodium dodecyl sulfonate, sodium dodecyl sulfate, and sodium dodecylbenzene sulfonate.

7. A method for preparing the microcapsule sustained-release grinding aid according to claim 1, characterized in that: The mass ratio of the modified grinding aid, amide monomer, cross-linking monomer, initiator, emulsifier and water is (10-20):(15-20):(1.5-2.0):(0.05-0.5):(0.2-1.2):(200-250).

8. A microcapsule sustained-release grinding aid, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 7.

9. Use of the microcapsule sustained-release grinding aid according to claim 8 in cement concrete.

10. Use of the microcapsule sustained-release grinding aid according to claim 9 in cement concrete, characterized in that: When preparing mineral powder and cement, add microcapsule sustained-release grinding aid in an amount of 0.04-0.08%.

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