High-adsorbability moisture-absorption-resistant cement grinding aid as well as preparation method and application thereof

Abstract

The invention discloses a high-adsorbability moisture-absorption-resistant cement grinding aid as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing, stirring and heating tris (hydroxymethyl) aminomethane, straight-chain aldehyde and a solvent to 20-40 DEG C; slowly dropwise adding a pH regulator under a stirring condition to enable the pH of the system to be 6-7, and carrying out condensation reaction for 0.5-2 hours; stirring and temperature are maintained, a reducing agent is added for multiple times, a reaction is performed for 8-12 h, and the high-adsorbability moisture-absorption-resistant cement grinding aid is obtained through purification treatment. The high-adsorbability moisture-absorption-resistant cement grinding aid provided by the invention solves the problem that organic molecules with alkyl side chains are difficult to adsorb on the surface of cement powder through design and matching of functional groups and strong adsorption and film forming effects of hydroxyl and amido polar groups, and has an excellent adsorption effect on cement powder particles; the cement grinding aid can stably form a film after being adsorbed on the surfaces of cement powder particles, has a better grinding aiding effect than traditional alkylol amine (such as triethanolamine), and can remarkably improve the moisture absorption resistance of cement at the same time.

Description

Technical Field

[0001] This invention belongs to the field of materials technology, specifically relating to a cement grinding aid, its preparation method, and its application. Background Technology

[0002] Cement, as the most important basic material in the modern construction industry, has a quality stability that is directly related to the safety and durability of construction projects.

[0003] In cement production, grinding is one of the most energy-intensive processes, accounting for approximately 60%-70% of the plant's total electricity consumption. Grinding aids, as highly efficient and energy-saving chemical additives, reduce grinding energy consumption, improve grinding efficiency, and optimize particle size distribution by adsorbing onto the surface of cement particles, and have become an indispensable component of modern cement production.

[0004] Cement is a highly hygroscopic powder material. When exposed to air, it inevitably absorbs moisture, undergoing a "pre-hydration" reaction. This leads to cement clumping, reduced fluidity, and significant difficulties in transportation, storage, and distribution. Furthermore, some of the active components (such as C3A and C3S) in the moisture-absorbing cement undergo pre-hydration, resulting in abnormal setting time and a significant decrease in strength. In severe cases, this may prevent the cement from meeting national standards, creating potential quality hazards in engineering projects. The industry commonly employs passive protective measures such as improved packaging and optimized storage conditions, but these methods are costly and have limited effectiveness, failing to address the root cause of the problem.

[0005] Cement that has undergone high-efficiency grinding has an increased specific surface area and surface energy, leading to a sharp increase in moisture absorption and prehydration tendency. Polyols and polyol amines, as core components of traditional cement grinding aids, have limitations in their performance: Polyol and polyol amine cement grinding aid molecules adsorb onto the surface of cement particles through polar groups, and then connect with other grinding aids through remaining polar groups to form a stable adsorption film. The non-polar group structure plays a crucial role in the thickness of the adsorption film. Polyols and polyol amines have few non-polar groups and simple structures, resulting in limited grinding aid effects. Furthermore, polyol and polyol amine molecules contain multiple hydrophilic groups (-OH, -NH2), making them inherently strong hydrophilic and hygroscopic substances. They absorb moisture from the air, and when adsorbed onto the surface of cement particles, they essentially coat the particle surface with a "hydrophilic film." This film not only fails to block moisture but also accelerates the contact between moisture and the active components of cement, thus drastically intensifying the prehydration reaction.

[0006] Existing technologies often use simple physical mixing of grinding aids and anti-moisture additives to improve the grinding and moisture-absorbing properties of cement. However, the grinding mechanism and hydrophilic nature of traditional components make it difficult to simultaneously achieve moisture-absorbing properties. Attempts to simply mix single polyol amines with hydrophobic agents often result in competitive adsorption on the cement particle surface, leading to a decrease in grinding aid effect and unsatisfactory moisture-absorbing effect. Existing technologies introduce hydrophobic groups into the structures of polyols and polyol amines to improve the moisture-absorbing properties of cement, but due to changes in molecular polarity and steric hindrance, the adsorption capacity is reduced, making it difficult to achieve excellent results.

[0007] CN116986844 discloses a grinding aid for improving the hygroscopicity of cement. Its components, by mass percentage, are as follows: 6%–15% polyol monofatty acid ester compound, 12%–48% polyol amine monofatty acid ester compound, 1%–6% gypsum dehydration inhibitor, 3%–7% grinding film-forming agent, 0.5%–3.0% titanate coupling agent, 0.1%–0.5% defoamer, and the remainder being water. This invention improves the hygroscopicity of cement by modifying the cement surface with polyol monofatty acid ester compounds and polyol amine monofatty acid ester compounds. Specifically, the polyol monofatty acid ester compound and the polyol amine monofatty acid ester compound have a carbon chain length of 8... The esterification products of fatty acids with polyol amines (type 18 and type 18) show a decrease in the proportion of polar groups after esterification of hydroxyl groups in polyols and polyol amines, and the 8% of fatty acids undergoes further esterification. The steric hindrance of the 18-carbon chain reduces the adsorption of molecules on the surface of cement particles, thus limiting its grinding aid and moisture resistance effects. Summary of the Invention

[0008] Based on the characteristics of cement and the molecular structure of organic matter, this invention provides a highly adsorbent and moisture-resistant cement grinding aid. The preparation method is simple and efficient. Through the design and matching of adsorption groups, film-forming groups and hydrophobic groups, the obtained highly adsorbent and moisture-resistant cement grinding aid has excellent grinding aid and moisture-resistant effects on cement.

[0009] A highly adsorbent, moisture-resistant cement grinding aid has the following molecular structure: ; Wherein, R is a C3-C7 straight-chain alkyl group.

[0010] This invention also provides a method for preparing the above-mentioned highly adsorbent, moisture-resistant cement grinding aid, comprising the following steps: Mix and stir tris(hydroxymethyl)aminomethane, linear aldehyde and solvent and heat to 20-40℃; Under stirring conditions, slowly add a pH adjuster to adjust the pH of the system to 6-7, and allow the condensation reaction to proceed for 0.5-2 hours. The reducing agent was added in multiple batches while maintaining stirring and temperature, and the reaction was carried out for 8-12 hours. After purification, a highly adsorbent and moisture-resistant cement grinding aid was obtained.

[0011] In the optimized scheme, the stirring speed is 500-800 rpm; the reducing agent is added in 4-8 batches, with an interval of 15-30 minutes between each batch.

[0012] According to the above scheme, the linear aldehyde is one or any mixture of linear aldehydes with a carbon chain length of 4-8. In the optimized scheme, the linear aldehyde is one or any mixture of n-butyraldehyde, n-pentanaldehyde, n-hexanaldehyde, n-heptanaldehyde, and n-octanaldehyde.

[0013] According to the above scheme, the solvent is one of methanol and ethanol or any mixture thereof.

[0014] According to the above scheme, the pH adjuster is glacial acetic acid.

[0015] According to the above scheme, the reducing agent is one or any mixture of sodium cyanoborohydride and sodium triacetoxyborohydride.

[0016] According to the above scheme, the molar ratio of tris(hydroxymethyl)aminomethane, linear aldehyde, and reducing agent is 1:(1.1-1.5):(1.1-1.5).

[0017] According to the above scheme, the concentration of tris(hydroxymethyl)aminomethane in the reaction system is 0.2-0.5 mol / L.

[0018] The present invention also provides the application of the above-mentioned highly adsorbent and moisture-resistant cement grinding aid as a cement grinding aid, anti-caking agent, and anti-moisture-absorbing agent, including spraying the highly adsorbent and moisture-resistant cement grinding aid onto the cement raw materials entering the mill in the cement grinding process.

[0019] According to the above scheme, the dosage of the highly adsorbent and moisture-resistant cement grinding aid is 0.02-0.05 wt% of the cement raw materials fed into the mill.

[0020] This invention utilizes a nucleophilic addition-elimination reaction between the primary amino group (-NH2) of tris(hydroxymethyl)aminomethane and the aldehyde group (-CHO) of a straight-chain aldehyde with a carbon chain length of 4-8 to generate an imine. A reducing agent is then used to selectively reduce the imine intermediate to a stable secondary amine, thereby achieving the alkylation of tris(hydroxymethyl)aminomethane. The amino group of tris(hydroxymethyl)aminomethane is highly basic, and its reactivity is even higher once a secondary amine is formed. Other reactions are difficult to control at the single-alkylation stage; reductive amination can effectively achieve single-alkylation. The reaction temperature is selected between 20°C and 40°C. Within this range, the temperature provides sufficient molecular kinetic energy, allowing the condensation and reduction steps to proceed at a reasonable rate. For the reducing agent, this temperature range ensures sufficient reducing activity while maintaining good chemoselectivity. By employing a batch-by-batch, slow addition of the reducing agent, the reduction reaction proceeds smoothly, heat is released gradually, and system temperature runaway is avoided. This also prevents excessively high local concentrations of the reducing agent, which could lead to direct reactions with the aldehyde and subsequent side reactions. Furthermore, it avoids the slow gas production that occurs when the reducing agent reacts with acid; a rapid, single addition would cause a massive, instantaneous gas outburst, resulting in material spillage. The preparation method provided by this invention offers relatively mild conditions, simple operation, and produces only water as a byproduct. Post-processing is easy, the reaction is highly efficient, and it ensures the effective formation of the target compound.

[0021] The highly adsorbent and moisture-resistant cement grinding aid prepared by this invention has a molecular structure with a trihydroxy (-OH) structure at one end, a secondary amine (-NH-) structure in the middle, and an alkyl chain structure at the other end.

[0022] The highly adsorbent and moisture-resistant cement grinding aid prepared in this invention forms a "claw-shaped" structure with trihydroxyl groups, exhibiting strong adsorption of Ca, Al, Si, Fe, and other elements generated during cement grinding. This multi-point anchoring effect enhances adsorption strength and stability; the total adsorption energy is the sum of the energies of the three hydrogen bonds, far exceeding the adsorption energy of a single hydroxyl group, making it more difficult for molecules to desorb from the surface. It also enhances steric hindrance and dispersion; when two cement particles approach each other due to van der Waals forces, their outer protective layer first undergoes physical contact, and the resulting steric hindrance strongly repels further approach of the powder particles, effectively preventing cement powder particle agglomeration. Furthermore, it facilitates film formation; on the surface of cement particles, molecules are interconnected through hydrogen bonds, forming a continuous network structure. This network is denser and stronger than isolated molecular adsorption layers.

[0023] The nitrogen atom on the secondary amine structure of the highly adsorbent, moisture-resistant cement grinding aid molecule prepared in this invention possesses a lone pair of electrons. Through electrostatic and coordination chemistry, it transforms the initial physical adsorption layer into a stable and dense "chemisorption film." The electrostatic and coordination effects of the amine groups make the molecules arrange themselves more orderly and compactly on the cement surface. Multiple molecules can also interact with each other through the amine groups and hydroxyl groups or other molecules to form a cross-linked, continuous network structure.

[0024] Compared to traditional alkanolamines (such as triethanolamine), the highly adsorbent and moisture-resistant cement grinding aid prepared in this invention has a more concentrated hydroxyl structure and stronger adsorption capacity, and it "independently" releases the N atom from the center, effectively avoiding the shielding of the N atom by the hydroxyl group when the N atom is located in the center.

[0025] The highly adsorbent and moisture-resistant cement grinding aid prepared in this invention features an alkyl chain structure with a chain length of 4-8, which effectively enhances its grinding aid and moisture-resistant properties. The hydroxyl and amino polar groups strongly adsorb onto cement powder particles and form a film, while the alkyl chain structure at the other end effectively increases the thickness of the adsorption film. The steric hindrance of the alkyl chain structure isolates and disperses cement powder particles, effectively preventing secondary agglomeration. The alkyl chain structure effectively reduces the surface energy of the cement powder, thereby improving the grinding aid effect. The 4-8 chain length alkyl chain structure is hydrophobic, minimizing its affinity for water molecules and preventing direct contact between water vapor molecules and the surface of cement particles. This significantly slows down the moisture absorption process. Through systematic experiments, the inventors discovered that when the alkyl side chain length is less than 4, the molecule's hydrophobicity is insufficient, and the moisture-resistant effect is significantly weakened. When the chain length exceeds 8, its moisture-proof performance also decreases significantly. Longer alkyl chains lead to significant steric hindrance, reducing the amount of moisture-proof agent adsorbed on the surface of cement particles, thus weakening its covering ability and hydrophobic effect.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The highly adsorbent and moisture-resistant cement grinding aid provided by this invention has excellent adsorption effect on cement powder particles; 2. The highly adsorbent and moisture-resistant cement grinding aid provided by this invention can stably form a film after being adsorbed onto the surface of cement powder particles; 3. The highly adsorbent and moisture-resistant cement grinding aid provided by the present invention solves the problem that organic molecules with alkyl side chains are difficult to adsorb onto the surface of cement powder through functional group design and matching, and strong adsorption and film-forming effects of hydroxyl and amine polar groups. 4. The highly adsorbent and moisture-resistant cement grinding aid provided by this invention has a better grinding aid effect than traditional alkanolamines (such as triethanolamine) through strong adsorption and increased adsorption film thickness. 5. The highly adsorbent and moisture-resistant cement grinding aid provided by this invention can significantly improve the moisture resistance of cement through its alkyl side chain; 6. The method for preparing highly adsorbent and moisture-resistant cement grinding aid provided by the present invention avoids excessive alkylation of amine groups through the reduction amine method, can efficiently generate the target product, the preparation method is simple and the raw materials are easy to obtain, and it has industrialization prospects. Detailed Implementation

[0027] The following embodiments further illustrate the technical solutions of the present invention, but are not intended to limit the scope of protection of the present invention. The following specific embodiments are only some preferred embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, modifications, substitutions, and improvements made by those skilled in the art without creative effort are all within the scope of protection of the present invention.

[0028] A specific embodiment provides a highly adsorbent, moisture-resistant cement grinding aid, the synthesis route of which is shown below:

[0029] ;

[0030] The specific implementation provides a method for preparing a highly adsorbent, moisture-resistant cement grinding aid, including the following steps: Add tris(hydroxymethyl)aminomethane, a linear aldehyde, and a solvent to a reaction vessel, and continuously stir at a rate of 500-800 rpm. Adjust the system temperature to 20-40℃, and slowly add a pH adjuster to bring the system pH to 6-7. Allow the condensation reaction to proceed for 0.5-2 hours. Maintaining the stirring rate and temperature, add the reducing agent in 4-8 portions, each 15-30 minutes apart, and allow the reaction to proceed for 8-12 hours. After the reaction is complete, purify the mixture to obtain a highly adsorbent, moisture-resistant cement grinding aid. The molar ratio of tris(hydroxymethyl)aminomethane, the linear aldehyde, and the reducing agent is 1:(1.1-1.5):(1.1-1.5). The concentration of tris(hydroxymethyl)aminomethane in the reaction system is 0.2-0.5 mol / L.

[0031] Specifically, the linear aldehyde is one or any mixture of linear aldehydes with a carbon chain length of 4-8; preferably, the linear aldehyde is one or any mixture of n-butyraldehyde, n-pentanaldehyde, n-hexanaldehyde, n-heptanaldehyde, and n-octanaldehyde. The solvent used is one or any mixture of methanol and ethanol. The pH adjuster used is glacial acetic acid. The reducing agent used is one or any mixture of sodium cyanoborohydride and sodium triacetoxyborohydride.

[0032] The tris(hydroxymethyl)aminomethane used in this embodiment is manufactured by Hubei Yuanda Fuchi Pharmaceutical Chemical Co., Ltd. The reducing agent sodium cyanoborohydride is manufactured by Wuhan Kamik Technology Co., Ltd. The reducing agent sodium triacetoxyborohydride is manufactured by Hubei Zhengxingyuan Fine Chemical Co., Ltd. Unless otherwise specified, all other raw materials were obtained commercially.

[0033] Example 1 A condensation reaction mixture containing 500 mL of 0.20 mol / L tris(hydroxymethyl)aminomethane-methanol solution and 0.11 mol n-octaldehyde was added to a reactor. The mixture was stirred continuously at 800 rpm, and the system temperature was adjusted to 20°C. Glacial acetic acid was slowly added dropwise to adjust the pH to 6, and the reaction was allowed to proceed for 0.5 h. While maintaining the stirring rate and temperature, 0.15 mol sodium cyanoborohydride was added in eight portions, each 15 minutes apart, and the reaction was allowed to continue for 8 h. After the reaction was completed, the mixture was purified to obtain a highly adsorbent, moisture-resistant cement grinding aid.

[0034] Example 2 A condensation reaction mixture containing 200 mL of 0.50 mol / L tris(hydroxymethyl)aminomethane-ethanol solution and 0.15 mol of n-butyraldehyde was added to a reactor. The mixture was stirred continuously at 500 rpm, and the system temperature was adjusted to 40°C. Glacial acetic acid was slowly added dropwise to adjust the pH to 7, and the reaction was allowed to proceed for 2 hours. While maintaining the stirring rate and temperature, 0.11 mol of sodium triacetoxyborohydride was added in four portions, 30 minutes apart, and the reaction was allowed to continue for 12 hours. After the reaction was completed, the mixture was purified to obtain a highly adsorbent, moisture-resistant cement grinding aid.

[0035] Example 3 A condensation reaction mixture containing 200 mL of 0.50 mol / L tris(hydroxymethyl)aminomethane-methanol solution and 0.15 mol of n-octaldehyde was added to a reactor. The mixture was stirred continuously at 569 rpm, and the system temperature was adjusted to 40°C. Glacial acetic acid was slowly added dropwise to adjust the pH to 7, and the reaction was allowed to proceed for 1 hour. While maintaining the stirring rate and temperature, 0.11 mol of sodium cyanoborohydride was added in four portions, 30 minutes apart, and the reaction was allowed to continue for 12 hours. After the reaction was completed, the mixture was purified to obtain a highly adsorbent, moisture-resistant cement grinding aid.

[0036] Example 4 A condensation reaction mixture containing 500 mL of 0.20 mol / L tris(hydroxymethyl)aminomethane-ethanol solution and 0.15 mol of n-butyraldehyde was added to a reactor. The mixture was stirred continuously at 658 rpm, and the system temperature was adjusted to 20°C. Glacial acetic acid was slowly added dropwise to adjust the pH to 6, and the reaction proceeded for 1.3 h. While maintaining the stirring rate and temperature, 0.15 mol of sodium cyanoborohydride was added in eight portions, each 15 minutes apart, and the reaction continued for 8 h. After the reaction was completed, the mixture was purified to obtain a highly adsorbent, moisture-resistant cement grinding aid.

[0037] Example 5 A mixture containing 250 mL of 0.40 mol / L tris(hydroxymethyl)aminomethane-ethanol solution and 0.13 mol of n-pentanal was added to a reaction vessel. The mixture was stirred continuously at 712 rpm, and the system temperature was adjusted to 21°C. Glacial acetic acid was slowly added dropwise to adjust the pH to 6.2, and the condensation reaction was carried out for 1.5 h. While maintaining the stirring rate and temperature, 0.13 mol of sodium triacetoxyborohydride was added in six portions, 21 minutes apart, and the reaction was allowed to proceed for 9 h. After the reaction was completed, the mixture was purified to obtain a highly adsorbent, moisture-resistant cement grinding aid.

[0038] Example 6 A condensation reaction mixture containing 200 mL of 0.50 mol / L tris(hydroxymethyl)aminomethane-methanol solution and 0.12 mol of n-hexanal was added to a reactor. The mixture was stirred continuously at 603 rpm, and the system temperature was adjusted to 35°C. Glacial acetic acid was slowly added dropwise to adjust the pH to 6.3, and the reaction proceeded for 0.8 h. While maintaining the stirring rate and temperature, 0.12 mol of sodium triacetoxyborohydride was added in five portions, 17 minutes apart, and the reaction was allowed to proceed for 10 h. After the reaction was completed, the mixture was purified to obtain a highly adsorbent, moisture-resistant cement grinding aid.

[0039] Example 7 A condensation reaction mixture containing 500 mL of 0.20 mol / L tris(hydroxymethyl)aminomethane-methanol solution and 0.14 mol of n-heptanal was added to a reactor. The mixture was stirred continuously at 549 rpm, and the system temperature was adjusted to 39 °C. Glacial acetic acid was slowly added dropwise to adjust the pH to 6.1, and the reaction proceeded for 0.5 h. While maintaining the stirring rate and temperature, 0.14 mol of sodium triacetoxyborohydride was added in seven portions, 28 minutes apart, and the reaction was allowed to proceed for 11 h. After the reaction was completed, the mixture was purified to obtain a highly adsorbent, moisture-resistant cement grinding aid.

[0040] Example 8 A condensation reaction mixture containing 250 mL of 0.40 mol / L tris(hydroxymethyl)aminomethane-ethanol solution and 0.11 mol of n-octaldehyde was added to a reactor. The mixture was stirred continuously at 619 rpm, and the system temperature was adjusted to 24 °C. Glacial acetic acid was slowly added dropwise to adjust the pH to 6.5, and the reaction was allowed to proceed for 2.0 h. While maintaining the stirring rate and temperature, 0.13 mol of sodium cyanoborohydride was added in four portions, 26 minutes apart, and the reaction was allowed to continue for 12 h. After the reaction was completed, the mixture was purified to obtain a highly adsorbent, moisture-resistant cement grinding aid.

[0041] Example 9 A solution containing 400 mL of 0.25 mol / L tris(hydroxymethyl)aminomethane-ethanol and 0.15 mol of n-butyraldehyde was added to a reaction vessel. The mixture was stirred continuously at 512 rpm, and the system temperature was adjusted to 28°C. Glacial acetic acid was slowly added dropwise to adjust the pH to 6.8, and the condensation reaction was carried out for 0.7 h. While maintaining the stirring rate and temperature, 0.11 mol of sodium cyanoborohydride was added in eight portions, each 24 minutes apart, and the reaction was allowed to proceed for 10 h. After the reaction was completed, the mixture was purified to obtain a highly adsorbent, moisture-resistant cement grinding aid.

[0042] Example 10 A condensation reaction mixture containing 400 mL of 0.25 mol / L tris(hydroxymethyl)aminomethane-methanol solution and 0.13 mol of n-pentanal was added to a reactor. The mixture was stirred continuously at 785 rpm, and the system temperature was adjusted to 30°C. Glacial acetic acid was slowly added dropwise to adjust the pH to 6.3, and the reaction proceeded for 1.8 h. While maintaining the stirring rate and temperature, 0.15 mol of sodium triacetoxyborohydride was added in six portions, spaced 23 minutes apart, and the reaction continued for 9 h. After the reaction was completed, the mixture was purified to obtain a highly adsorbent, moisture-resistant cement grinding aid.

[0043] Comparative Example 1 Repeat Example 1, but replace n-octanal with lauraldehyde, keeping other conditions unchanged, to obtain Comparative Sample 1.

[0044] Comparative Example 2 Repeat Example 2, but replace n-butyraldehyde with n-propionaldehyde, keeping other conditions unchanged, to obtain Comparative Sample 2.

[0045] Comparative Example 3 Commercially available triethanolamine.

[0046] Comparative Example 4 1.0 mol triethanolamine, 1.0 mol octanoic acid, and 0.5868 g hydroquinone were added sequentially to a reaction vessel. Under nitrogen protection, the mixture was heated to 43°C and stirred for 15 minutes. The temperature was then raised to 110°C, and 2.9340 g concentrated sulfuric acid and 23.4719 g benzene were added. The reaction was carried out for 2.0 h. During the reaction, the water generated was separated by vacuum. After no more water was separated, the water-carrying agent and unreacted fatty acids were removed by vacuum. The mixture was then cooled to room temperature to obtain triethanolamine monooctanoic acid ester.

[0047] Five kg of various dried cement raw materials were added to a test mill according to the PO 42.5 cement mix ratio: clinker 78%, slag 8%, fly ash 5%, coal slag 5%, and desulfurized gypsum 4%. Before grinding, the sample was added to the cement raw materials at a dosage of 0.03 wt%. The grinding time was fixed at 23 min to obtain the PO 42.5 cement sample. For the blank group without the above samples, the highly adsorbent and moisture-resistant cement grinding aid group prepared in Examples 1 to 10 was added, and the sample groups of Comparative Examples 1, 2, 3, and 4 were added for performance testing and evaluation.

[0048] 1. Adsorption test Accurately weigh 1.0000 g of cement powder sample and place it in a centrifuge tube. Add 20 mL of anhydrous ethanol and extract in a constant-temperature shaker for 10-20 minutes. Place the extracted centrifuge tube in a high-speed centrifuge and centrifuge at a speed of 10,000 rpm or higher for 10-15 minutes to ensure complete precipitation of cement particles. Discard the supernatant after centrifugation, retaining the cement solid precipitate. Place the washed cement solid precipitate in a 40°C oven to dry completely, removing any residual ethanol. Accurately weigh 0.1000 g of the dried cement solid powder and place it in the sample boat of the TOC analyzer. Use the solid sample module of the TOC analyzer to determine the total organic carbon content in the solid sample. Based on the instrument results and sample weight, directly calculate the sample mass adsorbed on the cement, and then calculate the adsorption rate by combining the adsorption amount with the amount added.

[0049] Table 1 Adsorption rate results

[0050] As shown in Table 1, the prepared highly adsorbent and moisture-resistant cement grinding aid has good adsorption properties for cement powder particles, which is better than that of comparative example 3 (triethanolamine). Comparative example 1 showed a significant decrease in adsorption properties when the alkyl chain length was increased, and its adsorption properties were significantly better than those of comparative example 4 (triethanolamine monooctanoate).

[0051] 2. Evaluation of grinding aid effect Take out the cement sample from the mill and test the fineness of the cement exiting the mill according to GB / T 1345-2005 "Test Method for Fineness of Cement - Sieve Analysis Method". Test the specific surface area of ​​the cement exiting the mill according to GB / T 8074-2008 "Determination Method for Specific Surface Area of ​​Cement - Blaine Method".

[0052] Table 2 Evaluation Results of Grinding Aid Effect

[0053] Table 2 shows that adding a highly adsorbent, moisture-resistant cement grinding aid during cement grinding significantly increased the specific surface area of ​​the cement and significantly reduced the residue on the 80μm and 45μm sieves. This indicates that the highly adsorbent, moisture-resistant cement grinding aid, due to its excellent adsorption properties, stable film formation, and thicker film thickness, has a superior grinding effect on cement. Comparative Examples 1 and 2 show that increasing or decreasing the alkyl chain length reduces the grinding effect. Comparative Examples 3 and 4 show that the highly adsorbent, moisture-resistant cement grinding aid has a better grinding effect than triethanolamine and triethanolamine monooctanoate.

[0054] 3. Evaluation of moisture absorption resistance 1.5 kg of the prepared PO 42.5 cement was spread evenly in a sample pan and placed in a constant temperature and humidity chamber at 20℃ and 90%RH. The time was recorded simultaneously. The sample was weighed after 3 days, 7 days, and 28 days, and the water absorption rate was calculated based on the change in cement mass. After 28 days, the sample was sieved using a 0.8 mm square-hole sieve, and the agglomeration rate was calculated based on the residue on the sieve.

[0055] Table 3 Evaluation results of moisture-absorbing effect

[0056] Table 3 shows that the blank group of cement absorbs moisture in humid environments, leading to an increase in water absorption and ultimately severe cement clumping. Adding the highly adsorbent anti-moisture cement grinding aids prepared in Examples 1 to 10 significantly reduced the water absorption rate of the cement at 7 days and 28 days, and significantly reduced the clumping rate at 28 days, indicating that its side chains can effectively isolate moisture in the air from contacting the cement, providing excellent anti-moisture absorption. Comparative Example 1 shows that increasing the alkyl chain length reduces the anti-moisture absorption effect due to decreased adsorption. Comparative Example 2 shows that decreasing the alkyl chain length reduces the anti-moisture absorption effect due to the shorter alkyl chain. Comparative Example 3 shows that the hydroxyl and amino groups in the triethanolamine structure increase the absorption of moisture from the air by the cement, resulting in more severe moisture absorption. Comparative Example 4 shows that triethanolamine monooctanoate has a low adsorption rate and an unstable structure that is easily hydrolyzed, making its anti-moisture absorption performance inferior to that of the highly adsorbent anti-moisture cement grinding aids.

[0057] 4. Cement performance testing The strength properties of the prepared PO 42.5 cement after milling and the cement after being placed in a constant temperature and humidity chamber at 20℃ and 90%RH for 28 days were tested. The cement strength test was performed in accordance with GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)".

[0058] Table 4 Strength Performance Test

[0059] Table 4 shows that the cement strength decreased significantly after moisture absorption. Adding the highly adsorbent, moisture-resistant cement grinding aids prepared in Examples 1 to 10 promoted cement hydration through complexation, effectively increasing cement strength. Simultaneously, its significant moisture-proof effect provided good retention of cement strength in humid environments. Comparative Example 1 shows that increasing the alkyl chain length reduced the strength of the cement exiting the mill, and the weakened moisture-resistant effect also decreased the retention of cement strength in humid environments. Comparative Example 2 shows that decreasing the alkyl chain length reduced the strength of the cement exiting the mill, and the poor moisture-resistant effect resulted in poor retention of cement strength in humid environments. Comparative Example 3 shows that triethanolamine promotes cement strength but has no moisture-resistant effect, thus having no effect on maintaining cement strength in humid environments. Comparative Example 4 shows that triethanolamine monooleate reduced the strength of the cement exiting the mill due to its lower air-entraining effect, and its unstable structure and easy hydrolysis weakened its moisture-resistant effect, thus reducing its effect on maintaining cement strength in humid environments.

Claims

1. A high adsorptive moisture resistant cement grinding aid characterized in that Has the following molecular structure: ； Wherein, R is C3-C7 straight chain alkyl.

2. The process for the preparation of the high adsorptive moisture resistant cement grinding aid as claimed in claim 1, wherein the said process is characterized by It comprises the following steps: Mixing trimethylol aminomethane, straight chain aldehyde and solvent, stirring and heating to 20-40℃; Slowly drop the pH regulator under stirring condition to make the system pH 6-7, condensation reaction 0.5-2h; Maintain stirring and temperature, add reducing agent in several times, reaction 8-12h, purification treatment to obtain high adsorption moisture resistant cement grinding aid.

3. The process for the preparation of high adsorptive moisture resistant cement grinding aid as claimed in claim 2, wherein the said process is characterized by The straight chain aldehyde is one or any mixture of straight chain aldehyde with carbon chain length of 4-8.

4. The process for the preparation of high adsorptive moisture resistant cement grinding aid as claimed in claim 3, wherein the said process is characterized by The straight chain aldehyde is one or any mixture of n-butyl aldehyde, n-pentyl aldehyde, n-hexyl aldehyde, n-heptyl aldehyde, n-octyl aldehyde.

5. The process for the preparation of high adsorptive moisture resistant cement grinding aid as claimed in claim 2, wherein the said process is characterized by The solvent is one or any mixture of methanol, ethanol.

6. The process for the preparation of high sorptive moisture resistant cement grinding aid as claimed in claim 2, wherein the said process is characterized by The pH regulator is glacial acetic acid.

7. The process for the preparation of high adsorptive moisture resistant cement grinding aid as claimed in claim 2, wherein the said process is characterized by The reducing agent is one or any mixture of sodium cyanoborohydride, sodium triacetoxyborohydride.

8. The process for the preparation of high adsorptive moisture resistant cement grinding aid as claimed in claim 2, wherein the said process is characterized by The molar ratio of trimethylol aminomethane, straight chain aldehyde, reducing agent is 1:(1.1-1.5):(1.1-1.5); The concentration of trimethylol aminomethane in the reaction system is 0.2-0.5mol / L.

9. Use of the highly adsorptive moisture resistant cement grinding aid of claim 1 as a cement grinding aid, anticaking agent, moisture resistant agent, characterized in that It comprises spraying the high adsorption moisture resistant cement grinding aid on the cement raw material into the mill in the cement grinding process.

10. Use of the highly adsorptive moisture resistant cement grinding aid as claimed in claim 9 as a cement grinding aid, anticaking agent, moisture resistant agent, characterized in that The mixing amount of the high adsorption moisture resistant cement grinding aid is 0.02-0.05wt% of the cement raw material into the mill.

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