A grinding aid for cement processing and its preparation process

Abstract

This invention belongs to the field of cement production and processing technology, specifically relating to a grinding aid for cement processing and its preparation process. The invention utilizes vinyltrimethoxysilane, 2-hydroxyethyl acrylate, N-isopropylacrylamide, acrylic acid, and methyl allyl polyoxyethylene ether in a free radical polymerization reaction under the action of a redox initiator to prepare the grinding aid for cement processing. Through the synergistic effect of multiple functional groups, the adsorption capacity of the grinding aid to cement particles is improved, thereby enhancing the dispersibility of cement and achieving good grinding efficiency. Modified nano-alumina is added to the grinding aid for cement processing, utilizing its nano-sized particles as micro-balls to fill the gaps between cement particles, reducing particle collisions and friction, lowering grinding resistance, and improving grinding efficiency. Furthermore, during the subsequent hydration process of cement, it acts as a potential nucleus, promoting the formation and growth of C-S-H gel, and enhancing the strength of cement products.

Description

Technical Field

[0001] This invention belongs to the field of cement production and processing technology, specifically relating to a grinding aid for cement processing and its preparation process. Background Technology

[0002] Cement is one of the most widely used raw materials in the current construction industry. Its production process is often accompanied by huge energy consumption, especially in the final stage of cement production. In order to enhance its hydration activity, it usually needs to be ground to reduce the particle size of cement and accelerate the hydration rate. However, during the grinding process, cement often agglomerates, resulting in decreased grinding efficiency, increased energy consumption, and low production efficiency. Therefore, cement grinding aids need to be added during the cement grinding process to reduce grinding resistance and reduce particle agglomeration.

[0003] The main components of existing cement grinding aids are amine organic compounds, polyol organic compounds and inorganic salts. This type of liquid grinding aid, which is compounded by a variety of small molecules, has many drawbacks when used. Its grinding ability has an upper limit, and it is easy to cause a wide range of cement particle distribution and coarseness in the product, which leads to a decrease in cement strength and may even affect the cement strength grade.

[0004] Chinese patent application CN106746840A discloses a cement grinding aid comprising 1-3 parts hexadecyl alcohol, 1-3 parts ethylene glycol, 1-3 parts glycerol, 1-3 parts ethyl acetate, 11-15 parts stearic acid, 15-25 parts zeolite powder, 1-4 parts linseed oil, 1-4 parts silica nanoparticles, and 3-5 parts sucrose. This formulation uses readily available, pollution-free raw materials and can increase the content of fine particles in cement, thus improving grinding efficiency. However, alcohols only improve grinding efficiency through lubrication and drag reduction; they do not significantly enhance cement strength, especially early strength. In fact, low-molecular-weight alcohols may inhibit clinker hydration, leading to reduced early strength. Furthermore, excessive use of alcohol molecules may adsorb onto the surface of cement particles, forming a hydrophilic film, increasing the water requirement for cement hydration and indirectly affecting the strength and durability of concrete.

[0005] Chinese patent application CN104045255A discloses a cement grinding aid comprising 5-10 parts triethanolamine, 8-10 parts sodium acetate, 15-40 parts compound alcohol, and 30-60 parts water. This grinding aid uses triethanolamine, sodium acetate, compound alcohol, and molasses as common organic raw materials and can eliminate static electricity. However, triethanolamine and sodium acetate accelerate the hydration reaction of C3A and C3S in cement clinker, shortening the setting time and causing the cement to set too quickly, even resulting in rapid setting, which affects construction pouring and vibration. Furthermore, sodium acetate introduces sodium ions into the cement; when combined with triethanolamine, the soluble alkali content in the cement increases, increasing the risk of alkali-aggregate reaction in concrete and leading to cracking in the later stages of concrete development. Summary of the Invention

[0006] In order to solve the technical problems of poor grinding aid effect and reduced concrete strength in the above-mentioned technologies, the purpose of this invention is to provide a grinding aid for cement processing and its preparation process.

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

[0008] A process for preparing a grinding aid for cement processing includes the following steps:

[0009] S1: Mix vinyltrimethoxysilane and 2-hydroxyethyl acrylate to obtain mixture I;

[0010] S2: Mix mercaptopropionic acid, vitamin C and deionized water, and stir until vitamin C dissolves to obtain mixture II;

[0011] S3: Add deionized water, methyl allyl polyoxyethylene ether, and N-isopropylacrylamide to the reactor and stir until dissolved. Then add hydrogen peroxide, heat up, and add mixture I, acrylic acid, and mixture II dropwise while stirring. Keep the reaction at the temperature, cool, and obtain a grinding aid for cement processing.

[0012] Through the above technical solution, vinyltrimethoxysilane, 2-hydroxyethyl acrylate, N-isopropylacrylamide, acrylic acid, and methyl allyl polyoxyethylene ether undergo free radical polymerization under the action of a redox initiator to prepare a grinding aid for cement processing. Vinyltrimethoxysilane introduces silicon-oxygen bonds into the molecular side chain of the grinding aid, and after hydrolysis, generates silanol groups, which form covalent bonds (Si-O-Si) with the silicon-oxygen bonds in cement particles, especially slag and clinker, to achieve chemical adsorption of the grinding aid to cement particles. 2-hydroxyethyl acrylate introduces hydroxyl and ester groups into the molecular side chain of the grinding aid. The hydroxyl groups can react with the calcium in cement... 2+Hydrogen bonds are formed, increasing the polarity of the grinding aid molecules. Acrylic acid introduces carboxyl groups into the side chains of the grinding aid molecules, adsorbing positively charged clinker particles through electrostatic attraction. The long side chains of methyl allyl polyoxyethylene ether extend outward, forming a three-dimensional barrier that effectively prevents secondary agglomeration of cement particles and acts as a lubricant. Through the synergistic effect of multiple functional groups, the adsorption capacity of the grinding aid to cement particles is improved, thereby enhancing the dispersibility of cement and achieving good grinding efficiency. N-Isopropylacrylamide undergoes a conceptual change under temperature during the grinding process. At low temperatures (<80℃), the molecular chains unfold, exposing more hydroxyl and carboxyl groups, enhancing adsorption and electrostatic interaction with particles, and effectively dispersing cement particles. At high temperatures (>80℃), the molecular chains contract, avoiding increased energy consumption caused by excessive dispersion of cement particles at high temperatures. In addition, the hydroxyl groups in the 2-hydroxyethyl acrylate molecule and the silanol groups formed by the hydrolysis of the siloxane bonds in the vinyltrimethoxysilane molecule can serve as crystal nuclei for cement petrification, promoting the hydration reaction of tricalcium silicate and tricalcium aluminate, and improving the strength of cement products.

[0013] Furthermore, step S3 of the preparation process of the grinding aid for cement processing also includes adding modified nano-alumina to the reaction vessel, wherein the molar ratio of modified nano-alumina to methyl allyl polyoxyethylene ether is 0.35-0.42:1.

[0014] By using the above technical solution, modified nano-alumina is added to the grinding aid for cement processing. Its nano-sized particles act as micro-balls, filling the gaps between cement particles, reducing collisions and friction between particles, lowering grinding resistance, and improving grinding efficiency. At the same time, the modified nano-alumina can form hydrogen bonds or coordination bonds with the polar groups in the grinding aid molecules, anchoring the grinding aid molecules to the surface of nanoparticles, forming a composite system of nanocarrier-grinding aid, further improving grinding efficiency.

[0015] Furthermore, the modified nano-alumina is prepared by ultrasonically dispersing nano-alumina powder and vinyltriethoxysilane in an ethanol aqueous solution, heating under reflux for 3-4 hours, raising the temperature to 80-90°C, adding itaconic acid and benzoyl peroxide under nitrogen protection, stirring and reacting for 5-7 hours, centrifuging, washing, and vacuum drying to obtain modified nano-alumina.

[0016] The above technical solution involves reflux reaction of nano-alumina with vinyltriethoxysilane to silanize the nano-alumina, introducing double bond groups onto the surface of the nano-alumina. Then, under the action of an initiator, it undergoes a free radical reaction with itaconic acid, grafting itaconic acid onto the surface of the nano-alumina. This introduces a large number of carboxyl groups onto the surface of the nano-alumina. These carboxyl groups can form coordination bonds or hydrogen bonds with cations on the surface of cement particles, achieving a strong adsorption effect on the cement particles. This avoids the agglomeration of nano-alumina and allows for the full dispersion of cement particles. During the subsequent hydration process of cement, nano-alumina can serve as a potential nucleus for early hydration, promoting the formation and growth of CSH gel and improving early strength. The surface carboxyl groups can react with Ca(OH)2 in the cement hydration products to generate stable calcium salts, reducing the enrichment of Ca(OH)2 at the interface, improving the density and strength of the cement products.

[0017] Furthermore, the molar ratio of the nano-alumina powder, vinyltriethoxysilane, itaconic acid, and benzoyl peroxide is 1:0.15-0.25:0.2-0.4:0.05-0.10.

[0018] Furthermore, the ethanol aqueous solution contains 50%-60% ethanol by mass; the reflux temperature is 60-70°C; and the vacuum drying temperature is 100-120°C.

[0019] Furthermore, the molar ratio of vinyltrimethoxysilane in step S1 to methyl allyl polyoxyethylene ether in step S3 is 0.23-0.35:1; the molar ratio of 2-hydroxyethyl acrylate in step S1 to methyl allyl polyoxyethylene ether in step S3 is 0.33-0.42:1.

[0020] Furthermore, in step S3, the molar ratio of N-isopropylacrylamide to methyl allyl polyoxyethylene ether is 0.14-0.20:1; and the molar ratio of acrylic acid to methyl allyl polyoxyethylene ether is 3.5-5.0:1.

[0021] The above technical solution controls the number of polar groups such as siloxy groups, hydroxyl groups, ester groups, long-chain polyethers, and carboxyl groups in the molecular structure of cement grinding aids by adjusting the molar ratio of vinyltrimethoxysilane, 2-hydroxyethyl acrylate, N-isopropylacrylamide, acrylic acid, and methyl allyl polyoxyethylene ether. This, in turn, regulates the dispersion and lubrication properties of the cement grinding aid molecules on cement particles, thus affecting the grinding aid effect.

[0022] Furthermore, the molar ratio of hydrogen peroxide to methyl allyl polyoxyethylene ether in step S3 is 0.07-0.11:1.

[0023] Furthermore, in step S2, the molar ratio of mercaptopropionic acid to methyl allyl polyoxyethylene ether is 0.15-0.23:1; and the molar ratio of VC to methyl allyl polyoxyethylene ether is 0.07-0.11:1.

[0024] The above technical solution controls the molecular chain length of the grinding aid for cement processing by controlling the molar ratio of mercaptopropionic acid to methyl allyl polyoxyethylene ether. During the reaction, mercaptopropionic acid can terminate the molecular chain and generate new free radicals. These newly generated free radicals can initiate monomer polymerization. Therefore, when the amount of mercaptopropionic acid is low, the molecular chain of the resulting grinding aid molecule is long, and the molecular chain entanglement leads to excessive coating of cement particles, increasing the water demand of cement and reducing the grinding aid effect. Conversely, when the amount of mercaptopropionic acid is high, the molecular chain of the resulting grinding aid molecule is short, and the grinding aid molecule cannot completely cover the surface of cement particles. This leads to increased secondary agglomeration of cement particles during grinding, resulting in a sharp drop in the grinding aid effect.

[0025] Furthermore, the temperature for heating in step S3 is 80-90℃, and the holding time for the reaction is 2-3 hours.

[0026] The present invention also provides a grinding aid for cement processing prepared using the above-described process for preparing grinding aids for cement processing.

[0027] Through the above technical solution, the various functional groups of the cement grinding aid produced have a synergistic effect, and its effect is far greater than that of a single functional group. Therefore, the present invention can reduce energy consumption in the cement grinding process, enhance cement strength, and has a good grinding effect.

[0028] Compared with the prior art, the grinding aid for cement processing and its preparation process provided by the present invention have the following technical advantages:

[0029] (1) The present invention uses vinyltrimethoxysilane, 2-hydroxyethyl acrylate, N-isopropylacrylamide, acrylic acid and methyl allyl polyoxyethylene ether to carry out free radical polymerization reaction under the action of redox initiator to prepare a grinding aid for cement processing. Through the synergistic effect of multifunctional groups, the adsorption capacity of the grinding aid to cement particles is improved, thereby improving the dispersibility of cement and achieving good grinding efficiency.

[0030] (2) In this invention, modified nano-alumina is added to the grinding aid for cement processing. Its nano-sized particles are used as micro-balls to fill the gaps between cement particles, reduce the collision and friction between particles, reduce grinding resistance, and improve grinding efficiency.

[0031] (3) In this invention, itaconic acid is grafted onto the surface of nano-alumina through a silane coupling agent as a bridge, and carboxyl groups are introduced to form coordination bonds or hydrogen bonds with the cations on the surface of cement particles, thereby achieving a strong adsorption effect on cement particles. While playing a synergistic role with grinding aids, it can also serve as a potential crystal nucleus for cement hydration, thereby improving the strength of cement products. Attached Figure Description

[0032] Figure 1 The infrared spectrum of the grinding aid without modified alumina particles in Example 4 is shown. Detailed Implementation

[0033] The following description, in conjunction with specific embodiments, provides further details, but the present invention is not limited to these embodiments. Those skilled in the art can make various modifications based on the fundamental principles of the present invention, but all modifications that do not depart from the fundamental principles of the present invention are within its scope.

[0034] Unless otherwise specified, all raw materials mentioned in this embodiment are commercially available.

[0035] Preparation Example 1

[0036] The modified nano-alumina was prepared as follows: 1 mol of nano-alumina powder and 0.15 mol of vinyltriethoxysilane were added to 50 mL of 50% (w / w) ethanol aqueous solution, ultrasonically dispersed at 40 kHz for 2 h, then heated to reflux at 60 °C for 4 h, the temperature was raised to 80 °C, and 0.4 mol of itaconic acid and 0.05 mol of benzoyl peroxide were added under nitrogen protection. The mixture was stirred at 180 rpm for 7 h, centrifuged, washed twice with ethanol, and vacuum dried at 100 °C for 4 h to obtain the modified nano-alumina.

[0037] Preparation Example 2

[0038] The modified nano-alumina was prepared as follows: 1 mol of nano-alumina powder and 0.25 mol of vinyltriethoxysilane were added to 50 mL of 60% ethanol aqueous solution. The mixture was ultrasonically dispersed at 50 kHz for 1 h, then heated under reflux at 70 °C for 3 h. The temperature was then raised to 90 °C, and 0.2 mol of itaconic acid and 0.10 mol of benzoyl peroxide were added under nitrogen protection. The mixture was stirred at 200 rpm for 5 h, centrifuged, washed three times with ethanol, and vacuum dried at 120 °C for 2 h to obtain the modified nano-alumina.

[0039] Preparation Example 3

[0040] The modified nano-alumina was prepared as follows: 1 mol of nano-alumina powder and 0.19 mol of vinyltriethoxysilane were added to 50 mL of 55% (w / w) ethanol aqueous solution, ultrasonically dispersed at 45 kHz for 1.5 h, then heated under reflux at 68 °C for 3.5 h, the temperature was raised to 85 °C, and 0.32 mol of itaconic acid and 0.08 mol of benzoyl peroxide were added under nitrogen protection. The mixture was stirred at 190 rpm for 6 h, centrifuged, washed three times with ethanol, and vacuum dried at 110 °C for 3 h to obtain the modified nano-alumina.

[0041] Example 1

[0042] A process for preparing a grinding aid for cement processing includes the following steps:

[0043] S1: Mix 0.23 mol vinyltrimethoxysilane and 0.33 mol 2-hydroxyethyl acrylate to obtain mixture I;

[0044] S2: Mix 0.15 mol mercaptopropionic acid, 0.07 mol vitamin C and 100 mL deionized water, and stir until vitamin C dissolves to obtain mixture II;

[0045] S3: Add 2L of deionized water, 1mol of methyl allyl polyoxyethylene ether, and 0.14mol of N-isopropylacrylamide to the reactor and stir until dissolved. Then add 0.07mol of hydrogen peroxide and heat to 80℃. While stirring, add mixture I, 3.5mol of acrylic acid, and mixture II dropwise. Keep the reaction at this temperature for 2 hours, cool, add 0.35mol of modified nano-alumina, and stir until homogeneous to obtain a grinding aid for cement processing.

[0046] The modified nano-alumina used in this embodiment was prepared in Preparation Example 1.

[0047] Example 2

[0048] A process for preparing a grinding aid for cement processing includes the following steps:

[0049] S1: Mix 0.35 mol vinyltrimethoxysilane and 0.42 mol 2-hydroxyethyl acrylate to obtain mixture I;

[0050] S2: Mix 0.23 mol mercaptopropionic acid, 0.11 mol vitamin C and 100 mL deionized water, and stir until vitamin C dissolves to obtain mixture II;

[0051] S3: Add 2L of deionized water, 1mol of methyl allyl polyoxyethylene ether, and 0.20mol of N-isopropylacrylamide to the reactor and stir until dissolved. Then add 0.11mol of hydrogen peroxide and heat to 90℃. While stirring, add mixture I, 5.0mol of acrylic acid, and mixture II dropwise. Keep the reaction at this temperature for 3 hours, cool, add 0.42mol of modified nano alumina, and stir until homogeneous to obtain a grinding aid for cement processing.

[0052] The modified nano-alumina used in this embodiment was prepared in Preparation Example 2.

[0053] Example 3

[0054] A process for preparing a grinding aid for cement processing includes the following steps:

[0055] S1: Mix 0.31 mol vinyltrimethoxysilane and 0.39 mol 2-hydroxyethyl acrylate to obtain mixture I;

[0056] S2: Mix 0.20 mol mercaptopropionic acid, 0.09 mol vitamin C and 100 mL deionized water, and stir until vitamin C dissolves to obtain mixture II;

[0057] S3: Add 2L of deionized water, 1mol of methyl allyl polyoxyethylene ether, and 0.18mol of N-isopropylacrylamide to the reactor and stir until dissolved. Then add 0.08mol of hydrogen peroxide and heat to 85℃. While stirring, add mixture I, 4.6mol of acrylic acid, and mixture II dropwise. Keep the reaction at this temperature for 2.5h, cool, add 0.39mol of modified nano alumina, and stir until homogeneous to obtain a grinding aid for cement processing.

[0058] The modified nano-alumina used in this embodiment was prepared in Preparation Example 3.

[0059] Example 4

[0060] A process for preparing a grinding aid for cement processing includes the following steps:

[0061] S1: Mix 0.29 mol vinyltrimethoxysilane and 0.40 mol 2-hydroxyethyl acrylate to obtain mixture I;

[0062] S2: Mix 0.21 mol mercaptopropionic acid, 0.09 mol vitamin C and 100 mL deionized water, and stir until vitamin C dissolves to obtain mixture II;

[0063] S3: Add 2L of deionized water, 1mol of methyl allyl polyoxyethylene ether, and 0.16mol of N-isopropylacrylamide to the reactor and stir until dissolved. Then add 0.08mol of hydrogen peroxide and heat to 85℃. While stirring, add mixture I, 4.8mol of acrylic acid, and mixture II dropwise. Keep the reaction at this temperature for 2.5h, cool, add 0.39mol of modified nano alumina, and stir until homogeneous to obtain a grinding aid for cement processing.

[0064] The modified nano-alumina used in this embodiment was prepared in Preparation Example 3.

[0065] Example 5

[0066] The preparation process of the cement processing grinding aid described in this embodiment is similar to that in Example 4. The difference between this embodiment and Example 4 is that the preparation method of the modified nano alumina used in this embodiment is as follows: 1 mol of nano alumina powder and 0.22 mol of vinyltriethoxysilane are added to 50 mL of 55% ethanol aqueous solution. The mixture is ultrasonically dispersed at 45 kHz for 1.5 h, then heated under reflux at 68 °C for 3.5 h. The temperature is then raised to 85 °C, and 0.35 mol of itaconic acid and 0.08 mol of benzoyl peroxide are added under nitrogen protection. The mixture is stirred at 190 rpm for 6 h, centrifuged, washed three times with ethanol, and vacuum dried at 110 °C for 3 h to obtain the modified nano alumina.

[0067] Example 6

[0068] The preparation process of the grinding aid for cement processing described in this embodiment is similar to that in Example 4. The difference between this embodiment and Example 4 is that the amount of modified nano-alumina used in this embodiment is 0.40 mol.

[0069] Comparative Example 1

[0070] The preparation process of the grinding aid for cement processing described in this comparative example is similar to that in Example 4. The difference between this comparative example and Example 4 is that an equal amount of methyl allyl polyoxyethylene ether is used instead of 2-hydroxyethyl acrylate in this comparative example.

[0071] Comparative Example 2

[0072] The preparation process of the grinding aid for cement processing described in this comparative example is similar to that in Example 4. The difference between this comparative example and Example 4 is that an equal amount of methyl allyl polyoxyethylene ether is used instead of vinyltrimethoxysilane in this comparative example.

[0073] Comparative Example 3

[0074] The preparation process of the grinding aid for cement processing described in this comparative example is similar to that in Example 4. The difference between this comparative example and Example 4 is that modified nano-alumina was not added in this local example.

[0075] Comparative Example 4

[0076] The preparation process of the grinding aid for cement processing described in this comparative example is similar to that in Example 4. The difference between this comparative example and Example 4 is that the nano-alumina was not modified in this local example.

[0077] Comparative Example 5

[0078] The preparation process of the grinding aid for cement processing described in this comparative example is similar to that in Example 4. The difference between this comparative example and Example 4 is as follows: the molar ratio of vinyltrimethoxysilane in step S1 to methyl allyl polyoxyethylene ether in step S3 is 0.02:1; the molar ratio of 2-hydroxyethyl acrylate in step S1 to methyl allyl polyoxyethylene ether in step S3 is 0.11:1; the molar ratio of N-isopropylacrylamide to methyl allyl polyoxyethylene ether in step S3 is 0.35:1; and the molar ratio of acrylic acid to methyl allyl polyoxyethylene ether is 1:1.

[0079] Test case

[0080] Small-scale grinding experiment: Before the experiment, the material to be ground was washed and ground for 10 minutes. Then, 5 kg of clinker, limestone, slag, and gypsum were weighed according to the proportion, and a grinding aid was added. The mass of the grinding aid was 0.1% of the mass of the material to be ground (in the blank control group, an equal amount of deionized water was used instead of the grinding aid). The mixture was poured into a small mill and ground for 30 minutes to obtain cement. After the cement in the pot was allowed to settle for 2 minutes, it was sieved (using a 20-mesh square hole sieve), collected, labeled, weighed, and set aside. The chemical composition of cement clinker is shown in Table 1, and the cement proportions for the small-scale grinding experiment are shown in Table 2.

[0081] Table 1

[0082]

[0083] Table 2

[0084]

[0085] Specific surface area test: conducted in accordance with GB / T8074-2008;

[0086] Fineness test: The amount of cement residue on a 45μm sieve was tested according to GB / T 1345-2005;

[0087] Strength test: The flexural and compressive strength of cement are tested in accordance with GB / T 17671-2021.

[0088] Infrared Spectroscopy Analysis: The grinding aid without modified alumina particles in Example 4 was subjected to infrared spectroscopy analysis. Specifically, the test sample was hot-pressed into a thin film using a tablet press, with a thickness not exceeding 1 mm. The sample was then tested using a Fourier transform infrared spectrometer with a scanning wavenumber of 500-4000 cm⁻¹. -1 2cm resolution -1 .

[0089] The test results are shown in Table 3 and Figure 1 .

[0090] Table 3 Performance Test Results

[0091]

[0092] As shown in Table 1, compared with the blank control group, the grinding aid for cement processing provided by this invention, at a dosage of 0.1%, significantly increased the specific surface area, compressive strength, and flexural strength, and significantly reduced the residue on the 45μm sieve. This indicates that the grinding aid for cement processing provided by this invention has a good grinding aid effect. Among them, the grinding aid for cement processing prepared in Example 4 has the best grinding aid effect, with a cement specific surface area reaching 4503 m². 2 / kg, the residue on the 45μm sieve is reduced to 10.25%, the 1-day compressive strength is 25.35MPa, the 7-day compressive strength is 38.96MPa, the 28-day compressive strength is 50.21MPa, the 1-day flexural strength is 4.89MPa, the 7-day flexural strength is 7.86MPa, and the 28-day flexural strength is 9.03MPa, which is the preferred embodiment of the present invention.

[0093] Compared with Example 4, Comparative Examples 1 and 2 changed the polymer monomers of the grinding aid, and Comparative Example 5 changed the amount of grinding aid monomers. However, the grinding aid effect of the obtained grinding aid was worse. This shows that the polymer monomers and their amounts of the grinding aid in this invention have been optimized. Changing the monomer components or the amount of monomers will affect the grinding aid effect. Comparative Example 3 did not add modified nano-alumina, but the grinding aid effect of the grinding aid was worse, and the compressive strength and flexural strength of the cement decreased. This shows that modified nano-alumina can have a synergistic effect with the grinding aid molecules and can act as a potential nucleus for cement hydration, promoting the improvement of cement product strength. Comparative Example 4 did not modify the nano-alumina, but the grinding aid effect of the grinding aid was worse, and the compressive strength and flexural strength of the cement decreased. This is due to the agglomeration of nano-alumina.

[0094] Depend on Figure 1 It can be seen that at 3442cm -1 The characteristic peaks of 2-hydroxyethyl acrylate and the hydroxyl groups in acrylic acid appeared at 3245 cm⁻¹. -1 The characteristic peak of NH in N-isopropylacrylamide appeared at 2712 cm⁻¹.-1 The characteristic peak of the carboxyl group in acrylic acid appeared at 1727 cm⁻¹. -1 The characteristic peak of the ester group in 2-hydroxyethyl acrylate appeared at 1468 cm⁻¹. -1 The characteristic peak of -CH2- in the polyoxyethylene side chain of methyl allyl polyoxyethylene ether appeared at 1382 cm⁻¹. -1 The characteristic peak of -CH(CH3)2 in N-isopropylacrylamide appeared at 1205 cm⁻¹. -1 The characteristic peak of Si-OC in vinyltrimethoxysilane appeared at 1110 cm⁻¹. -1 The characteristic peak of COC in methyl allyl polyoxyethylene ether appeared at 844 cm⁻¹. -1 The presence of characteristic C-Si peaks in vinyltrimethoxysilane indicates that vinyltrimethoxysilane, 2-hydroxyethyl acrylate, N-isopropylacrylamide, acrylic acid, and methyl allyl polyoxyethylene ether all participated in the free radical polymerization reaction in this invention.

[0095] The above embodiments are merely illustrative of the present invention and are not intended to limit the invention. Those skilled in the art should not modify the above embodiments without departing from the spirit and scope of the present invention. All equivalent modifications or alterations made by those skilled in the art without departing from the technical concept of the present invention are still within the protection scope of the present invention.

Claims

1. A preparation process for a grinding aid for cement processing, characterized in that, Includes the following steps: S1: Mix vinyltrimethoxysilane and 2-hydroxyethyl acrylate to obtain mixture I; S2: Mix mercaptopropionic acid, vitamin C and deionized water, and stir until vitamin C dissolves to obtain mixture II; S3: Add deionized water, methyl allyl polyoxyethylene ether, and N-isopropylacrylamide to the reactor and stir until dissolved. Then add hydrogen peroxide, heat up, and add mixture I, acrylic acid, and mixture II dropwise while stirring. Keep the reaction at the temperature, cool, and obtain a grinding aid for cement processing. Step S3 also includes adding modified nano-alumina to the reactor, wherein the molar ratio of modified nano-alumina to methyl allyl polyoxyethylene ether is 0.35-0.42:1; The molar ratio of mercaptopropionic acid to methyl allyl polyoxyethylene ether is 0.15-0.23:1; the molar ratio of VC to methyl allyl polyoxyethylene ether is 0.07-0.11:

1. The modified nano-alumina is prepared by ultrasonically dispersing nano-alumina powder and vinyltriethoxysilane in an ethanol aqueous solution, heating under reflux for 3-4 hours, raising the temperature to 80-90℃, adding itaconic acid and benzoyl peroxide under nitrogen protection, stirring and reacting for 5-7 hours, centrifuging, washing, and vacuum drying to obtain modified nano-alumina.

2. The preparation process of the grinding aid for cement processing according to claim 1, characterized in that, The molar ratio of the nano-alumina powder, vinyltriethoxysilane, itaconic acid, and benzoyl peroxide is 1:0.15-0.25:0.2-0.4:0.05-0.10; the mass percentage of ethanol in the aqueous ethanol solution is 50%-60%; the reflux temperature is 60-70℃; and the vacuum drying temperature is 100-120℃.

3. The preparation process of the grinding aid for cement processing according to claim 1, characterized in that, The molar ratio of vinyltrimethoxysilane in step S1 to methyl allyl polyoxyethylene ether in step S3 is 0.23-0.35:1; the molar ratio of 2-hydroxyethyl acrylate in step S1 to methyl allyl polyoxyethylene ether in step S3 is 0.33-0.42:

1.

4. The preparation process of the grinding aid for cement processing according to claim 1, characterized in that, In step S3, the molar ratio of N-isopropylacrylamide to methyl allyl polyoxyethylene ether is 0.14-0.20:1; the molar ratio of acrylic acid to methyl allyl polyoxyethylene ether is 3.5-5.0:

1.

5. The preparation process of the grinding aid for cement processing according to claim 1, characterized in that, The molar ratio of hydrogen peroxide to methyl allyl polyoxyethylene ether in step S3 is 0.07-0.11:

1.

6. The preparation process of the grinding aid for cement processing according to claim 1, characterized in that, The temperature for heating in step S3 is 80-90℃, and the holding time for the reaction is 2-3 hours.

7. A grinding aid for cement processing prepared according to any one of claims 1-6.

Images