A multi-arm polymer cement grinding aid, its preparation method and application

Abstract

This invention discloses a multi-arm polymer cement grinding aid, its preparation method, and its application. The preparation method involves mixing tetrahydroxyethyl ethylenediamine, an amino mercapto acid compound, and a polymerization inhibitor, stirring, and heating to 100–120°C. A catalyst and a dehydrating agent are added, and the mixture undergoes esterification for 3–8 hours. The resulting product is purified to obtain a primary amine chain transfer agent. Next, amino polyethylene glycol methyl ether, a diunsaturated carboxylic acid or anhydride, the primary amine chain transfer agent, and water are mixed, stirred, and heated to 30–50°C. An initiator is added, and simultaneously, an aqueous solution of unsaturated polyol ether and a reducing agent are added dropwise. The mixture is then kept at 50–60°C for 1–2 hours to obtain the multi-arm polymer cement grinding aid. This invention, considering the characteristics of vertical mill processes and the relationship between cement particle morphology and performance, utilizes the designability of organic molecular structures to synthesize a grinding aid that can stabilize the vertical mill material layer, improve grinding efficiency, increase the sphericity of cement particles ground in the vertical mill, reduce the water requirement for the standard consistency of cement ground in the vertical mill, improve the fluidity of cement slurry ground in the vertical mill, and increase cement strength.

Description

Technical Field

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

[0002] Cement is a crucial raw material supporting social and economic development, but it is also a high-energy-consuming and high-carbon-emission industry. Statistics show that in 2022, my country's cement production reached 2.36 billion tons, accounting for approximately 55% of the world's total; in 2022, my country's CO2 emissions were 11.48 billion tons, with the cement industry accounting for about 14%. The cement grinding process involves converting electrical energy into mechanical energy, and then into the surface energy of the cement powder. Currently, ball mills are mostly used for cement grinding, but ball mills have low energy conversion rates, generally below 15%, with most electrical energy being consumed as ineffective heat.

[0003] With advancements in grinding technology, vertical roller mills have become the preferred grinding process for new and upgraded cement grinding projects both domestically and internationally in recent years, offering advantages such as small footprint, high hourly output, relatively low unit energy consumption, and simple operation and maintenance. Ball mills grind materials into powder through the impact of grinding balls or the mill wall, while vertical roller mills operate on the principle of bed grinding, where coarse particles are compressed and sheared between the grinding rollers and the grinding disc to become fine powder. For a long time, many studies have suggested that this grinding method, compared to ball milling, has the disadvantage of poor cement particle sphericity. This leads to problems such as high standard consistency water requirement and poor cement paste fluidity in cement ground by vertical roller mills, and these inherent defects are difficult to improve through operational adjustments.

[0004] The use of cement grinding aids in ball mills can reduce cement industry waste gas emissions and energy consumption without altering existing production conditions. This is significant for the comprehensive utilization of resources and energy conservation and carbon reduction in the cement industry, and has led to its widespread application. The working principle of cement grinding aids in ball mills is as follows: when incorporated into the cement grinding process, the cement grinding aid adsorbs onto the surface of the cement raw materials, exerting electrostatic repulsion and providing good dispersion, thus effectively improving grinding efficiency. However, vertical mills have higher air velocities, causing fine materials to be blown away and carried away by the classifier. The material flow rate is several times that of ball mills, thus eliminating the need for a dispersing agent. Since vertical mills rely on the extrusion between the grinding rollers and the grinding disc to grind materials into fine powder, a certain material layer thickness needs to be maintained on the grinding disc to ensure sufficient grinding. Traditional cement grinding aids used in ball mills, due to their good dispersibility, are not conducive to the stability of the material layer in vertical mills, resulting in insufficient grinding and making them unsuitable for use. Furthermore, they cannot improve the poor sphericity of cement particles ground in vertical mills. Spraying water onto the grinding disc of a vertical mill can improve the cohesiveness of the material, thus maintaining the stability of the mill's material layer. However, cement has hydration characteristics; the sprayed water is absorbed by the cement, causing a pre-hydration reaction that leads to a decrease in the hardening strength of the cement during use. Furthermore, traditional grinding aids mainly consist of small-molecule alcohols and amines, which remain in the cement after grinding and can promote cement hydration. This not only fails to improve the problems of high water requirements for standard consistency and poor cement paste fluidity in cement ground by vertical mills, but actually exacerbates these problems.

[0005] Organic compounds have significant advantages due to the designability of their molecular structures. Synthesizing cement grinding aids through molecular structure design can fundamentally address issues such as unstable grinding media, poor particle shape after grinding, and inadequate cement workability in vertical mills. This would overcome the bottleneck of traditional cement grinding aids' poor performance in vertical mills, thereby improving grinding efficiency and enhancing the performance of cement ground in vertical mills. However, there are currently few reports on this technology.

[0006] CN116477869A discloses a grinding aid for cement vertical mills and its preparation method. The raw materials for preparing the grinding aid, by mass percentage, are: 2-10% alkali activator, 8-20% polysaccharide, 1-11% acid, 2-19% amine salt, and the balance being water. Its composition remains a complex of small-molecule organic compounds, and its beneficial effect is only to reduce the early evaporation of organic components in the grinding aid; it does not solve the problem of the grinding aid's poor dispersibility hindering material layer stability in vertical mills.

[0007] CN115417616B discloses a grinding aid for cement grinding in vertical mills and its preparation method, belonging to the technical field of cement admixtures. This invention's grinding aid is prepared from alkanolamines, copolymers, polyglycerol, triethylene glycol, and water as raw materials. Among these, methyl allyl alcohol, acrylamide, low molecular weight unsaturated polyether copolymers, triglycerides, diglycerides, and glycerol are all polymers or small molecules with "linear" structural characteristics, lacking "multi-arm" structural characteristics, thus having limited effect on improving the efficiency of cement grinding in vertical mills.

[0008] CN113880490B discloses a grinding aid for cement grinding in a vertical mill and its application. The grinding aid comprises the following raw materials in weight percentages: 5-40% water-soluble polyester; 5-20% inorganic dispersing reinforcing agent; 5-20% polyol or alkanolamine; and 40-70% water. The water-soluble polyester prepared therein is mainly composed of ester groups. Ester groups are difficult to adsorb with cement during the grinding process, thus having a limited effect on improving the stability of the grinding media in the vertical mill.

[0009] CN105152568B provides a liquid cement grinding aid for vertical mills, comprising: 20%–30% phthalic acid amine salt, 10%–15% styrene-maleic anhydride copolymer, 10%–15% trimeric glycerol, 10%–15% glucose, 10%–15% cane molasses, 1% sodium hydroxide, and the balance being water. Its main components are primarily small-molecule organic compounds and linear polymers, offering limited improvement in the stability of the vertical mill grinding layer. Furthermore, the benzene-containing organic compounds are detrimental to human health during use. Summary of the Invention

[0010] The purpose of this invention is to provide a multi-arm polymer cement grinding aid, its preparation method, and its application. Targeting the characteristics of vertical mill processes and combining the relationship between cement particle morphology and performance, and utilizing the designability of organic molecular structures, this invention synthesizes a grinding aid that can stabilize the vertical mill material layer, improve grinding efficiency, increase the sphericity of cement particles ground in the vertical mill, reduce the water requirement for standard consistency of cement ground in the vertical mill, improve the fluidity of cement slurry ground in the vertical mill, and increase cement strength.

[0011] To achieve the above objectives, the following technical solution is adopted:

[0012] A multi-arm polymer cement grinding aid, wherein the multi-arm polymer has the following molecular structure:

[0013]

[0014] Wherein, R is either methyl or ethyl; when X is hydrogen, Y is hydroxyethyl; when X is hydroxyl, Y is hydrogen; when X is hydroxyethyl, Y is hydroxyethyl; degree of polymerization p is an integer from 67 to 135; degree of polymerization m is an integer from 30 to 78; degree of polymerization n is an integer from 10 to 13.

[0015] According to the above scheme, the weight-average molecular weight of the multi-arm polymer is 293,000 to 742,000 g / mol.

[0016] The preparation method of the above-mentioned multi-arm polymer cement grinding aid includes the following steps:

[0017] (1) Preparation of primary amine chain transfer agents:

[0018] Tetrahydroxyethyl ethylenediamine, amino mercapto acid compound, and polymerization inhibitor are mixed and stirred and heated to 100-120°C. A catalyst and dehydrating agent are added for esterification reaction for 3-8 hours. During the reaction, the water generated is separated by vacuum. After the reaction, the primary amine chain transfer agent is obtained by purification.

[0019] (2) Preparation of multi-arm polymer cement grinding aid:

[0020] Amino polyethylene glycol methyl ether, diunsaturated carboxylic acid or anhydride, a primary amine chain transfer agent, and water are mixed and stirred, and the temperature is raised to 30–50°C. An initiator is then added. The reaction temperature is maintained at 30–60°C, while an aqueous solution of unsaturated polyol ether and a reducing agent are added dropwise over a period of 4–6 hours. The mixture is then kept at 50–60°C for 1–2 hours, and water is added to obtain a 40–70 wt% multi-arm polymer cement grinding aid.

[0021] According to the above scheme, the molar ratio of tetrahydroxyethyl ethylenediamine and amino mercaptoic acid compound in step (1) is 1:(4-6); the amount of polymerization inhibitor is 0.2-1% of the total mass of tetrahydroxyethyl ethylenediamine and amino mercaptoic acid compound; the amount of catalyst is 3-6% of the total mass of tetrahydroxyethyl ethylenediamine and amino mercaptoic acid compound; and the amount of dehydrating agent is 15-25% of the total mass of tetrahydroxyethyl ethylenediamine and amino mercaptoic acid compound.

[0022] According to the above scheme, the amino mercapto acid compound in step (1) is one of 2-amino-3-mercaptopropionic acid and 2-amino-4-mercaptobutyric acid; the polymerization inhibitor is one of hydroquinone, p-hydroxyanisole, 2-tert-butylhydroquinone, and 2,6-dinitro-p-cresol or any mixture thereof; the catalyst is one of concentrated sulfuric acid, p-toluenesulfonic acid, and concentrated phosphoric acid or any mixture thereof; and the dehydrating agent is one of benzene and toluene or any mixture thereof.

[0023] According to the above scheme, the molar ratio of the primary amine chain transfer agent, amino polyethylene glycol methyl ether, diunsaturated carboxylic acid or acid anhydride, unsaturated polyol ether, initiator and reducing agent in step (2) is 1:(84~108):(84~108):(240~624):(47~140):(3~10), wherein the molar ratio of amino polyethylene glycol methyl ether to diunsaturated carboxylic acid or acid anhydride is 1:1.

[0024] According to the above scheme, the structural formula of the amino polyethylene glycol methyl ether is as follows: The degree of polymerization p is an integer from 67 to 135; the diunsaturated carboxylic acid or anhydride is one or any mixture of maleic acid, fumaric acid, and maleic anhydride; the unsaturated polyol ether is one of glycerol allyl ether, (allyloxy)propanediol, and pentaerythritol allyl ether; the initiator is one or any mixture of hydrogen peroxide, ammonium persulfate, sodium persulfate, and potassium persulfate; the reducing agent is one or any mixture of sodium bisulfite, sodium formaldehyde sulfoxylate, sodium ascorbate, and isoascorbic acid.

[0025] The above-mentioned multi-arm polymer cement grinding aid is applied in the final grinding process of cement vertical mill.

[0026] According to the above scheme, the dosage of the multi-arm polymer cement grinding aid is 0.08 to 0.20 wt% of the total mass of all cement raw materials.

[0027] According to the above scheme, the multi-arm polymer cement grinding aid is added uniformly to the cement raw material entering the mill or uniformly to the grinding disc of the vertical mill.

[0028] The hydroxyl group in the tetrahydroxyethylethylenediamine structure undergoes a complete esterification reaction with the carboxyl group in the structure of an excess aminothioic acid compound to prepare a primary amine-containing chain transfer agent. The primary amine-containing chain transfer agent has a nitrogen atom at its structural center and contains a primary amine, giving it good water solubility and better compatibility with the system in aqueous free radical polymerization, promoting efficient polymerization. The primary amine can undergo amidation with the carboxylic acid group, promoting grafting reactions; the terminal thiol group plays a chain transfer role in free radical polymerization. During free radical polymerization, the free radicals formed from unsaturated double bonds undergo chain transfer reactions with the thiol group grafting, promoting the formation of multi-arm polymerization products. Diunsaturated carboxylic acids or anhydrides react with unsaturated polyol ethers in the presence of an initiator and a reducing agent to form copolymers. The resulting free radicals undergo chain transfer reactions with the thiol group grafting in the primary amine-containing chain transfer agent structure, forming a multi-arm long-chain structure. Simultaneously, the carboxyl group in the diunsaturated carboxylic acid or anhydride structure can undergo amidation reactions with the primary amine in the amino-polyethylene glycol methyl ether structure or the primary amine in the primary amine chain transfer agent structure, allowing for further grafting of multi-arm long-chain structures. This synthetic route is reliable and yields a high target product.

[0029] The multi-arm polymer cement grinding aid prepared in this invention contains multiple hydroxyl groups, multiple carboxyl groups, sulfur atoms, nitrogen atoms, and polyethers, all of which are hydrophilic groups. Simultaneously, the polymer molecular weight is controlled to be between 293,000 and 742,000 g / mol to ensure good water solubility and better dispersion on cement raw materials or the vertical mill grinding disc. During the vertical mill grinding process, the hydroxyl, carboxyl, sulfur, nitrogen, and polyether groups in the multi-arm polymer cement grinding aid can adsorb and complex with iron, aluminum, calcium, magnesium, and silicon atoms formed by bond breaking during grinding of cement raw materials. The multi-arm structure can adsorb a large number of iron, aluminum, calcium, magnesium, and silicon atoms to form an adsorption network structure. The interweaving of multiple multi-arm polymers further agglomerates the cement raw materials, thereby improving the cohesiveness of the material on the vertical mill grinding disc, effectively stabilizing the material layer, ensuring thorough grinding of the material on the grinding disc, and improving the grinding efficiency of the vertical mill. The material is repeatedly ground under the strong agglomeration effect of the multi-arm polymer cement grinding aid. In addition to the action of the vertical mill roller, the materials also rub against each other, thereby improving the sphericity of cement particles ground by the vertical mill, reducing the water requirement for standard consistency of cement ground by the vertical mill, and improving the fluidity of cement slurry ground by the vertical mill.

[0030] After grinding, the ester and amide groups in the multi-arm polymer cement grinding aid structure remaining in the cement powder will further decompose under the alkaline environment generated by the hydration reaction during cement use. The ester groups preferentially decompose in an alkaline environment, releasing a copolymer of tetrahydroxyethyl ethylenediamine and amino polyethylene glycol methyl ether, diunsaturated carboxylic acids or anhydrides, and unsaturated polyol ethers. Tetrahydroxyethyl ethylenediamine, due to its hydroxyl and amino groups, can effectively complex iron, aluminum, calcium, and magnesium ions generated during cement hydration, promoting the cement hydration reaction and thus effectively improving cement strength. The copolymer of amino polyethylene glycol methyl ether, diunsaturated carboxylic acid or anhydride, and unsaturated polyol ether has carboxyl and hydroxyl groups at one end that can adsorb onto the surface of cement hydration products and exert an electrostatic repulsion effect, while the long amino polyethylene glycol methyl ether side chain at the other end exerts a steric hindrance effect, effectively dispersing cement hydration products. The amide group has a slower hydrolysis rate and can be further hydrolyzed after the ester group hydrolysis to release carboxyl and hydroxyl polymers with dispersing effects, thus maintaining the dispersion effect on cement hydration products. This reduces the water requirement for the standard consistency of cement ground by vertical mill and improves the fluidity of cement slurry ground by vertical mill.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] 1. The multi-arm polymer cement grinding aid provided by the present invention can improve the cohesiveness of materials on the grinding disc of a vertical mill, effectively stabilize the material layer, and enable the materials to be fully ground on the grinding disc, thereby improving the grinding efficiency of the vertical mill.

[0033] 2. The multi-arm polymer cement grinding aid provided by the present invention can provide a strong agglomeration effect to make cement raw materials repeatedly grind, thereby causing mutual friction between materials, thereby improving the sphericity of cement particles ground by vertical mill, reducing the water requirement for standard consistency of cement ground by vertical mill, and improving the fluidity of cement slurry ground by vertical mill.

[0034] 3. The multi-arm polymer cement grinding aid provided by the present invention will further decompose and continuously release substances that have a dispersing effect on hydration products in the alkaline environment generated by the cement hydration reaction, thereby reducing the water requirement for the standard consistency of cement ground by the vertical mill and improving the fluidity of the cement slurry ground by the vertical mill.

[0035] 4. The multi-arm polymer cement grinding aid provided by this invention will further decompose and release tetrahydroxyethyl ethylenediamine in the alkaline environment generated by the cement hydration reaction, thereby promoting cement hydration and increasing cement strength.

[0036] 5. The method for preparing multi-arm polymer cement grinding aid provided by the present invention is reliable, safe, and has good controllability, and can be industrialized. Detailed Implementation

[0037] 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.

[0038] A specific embodiment provides a method for preparing a multi-arm polymer cement grinding aid:

[0039] (1) Preparation of primary amine chain transfer agent: Tetrahydroxyethyl ethylenediamine, amino mercapto acid compound and polymerization inhibitor are added to the reaction vessel in sequence. Under nitrogen protection, the temperature is raised to 60-80℃ and stirred for 15-30 minutes. The temperature is then raised to 100-120℃, and a catalyst and dehydrating agent are added. The reaction is carried out for 3-8 hours. During the reaction, the water generated by the reaction is separated by vacuum. After the hydroxyl groups in tetrahydroxyethyl ethylenediamine are completely esterified, the dehydrating agent is removed by vacuum and the temperature is lowered to room temperature to obtain the primary amine chain transfer agent.

[0040] (2) Preparation of multi-arm polymer cement grinding aid: Amino polyethylene glycol methyl ether, diunsaturated carboxylic acid or anhydride, primary amine chain transfer agent and water are added to the reactor. While stirring, the temperature is raised to 30-50°C. After 15-30 minutes, an initiator is added to the reactor. Water is added to adjust the system concentration to 60-80%. The reaction temperature is maintained at 30-60°C. At the same time, dropwise addition of dropwise material A, composed of unsaturated polyol ether aqueous solution and dropwise material B, composed of reducing agent aqueous solution, is started. The dropwise addition time is 4-6 hours. Then, the temperature is kept at 50-60°C for 1-2 hours. Water is added to obtain a multi-arm polymer cement grinding aid with a concentration of 40-70 wt%.

[0041] The specific implementation details the sources of the test materials, which, unless otherwise specified, can be obtained commercially.

[0042] The specific implementation method provides that the tetrahydroxyethyl ethylenediamine is obtained through commercial sales, and the manufacturer is Henan Tianfu Chemical Co., Ltd.

[0043] Specifically, the amino mercapto acid compound is one of 2-amino-3-mercaptopropionic acid and 2-amino-4-mercaptobutyric acid, and the molar ratio of tetrahydroxyethylethylenediamine to the amino mercapto acid compound is 1:(4-6). 2-amino-3-mercaptopropionic acid and 2-amino-4-mercaptobutyric acid are commercially available.

[0044] Specifically, the polymerization inhibitor is one of hydroquinone, p-hydroxyanisole, 2-tert-butylhydroquinone, and 2,6-dinitro-p-cresol, and the amount used is 0.2% to 1% of the total mass of tetrahydroxyethyl ethylenediamine and amino mercaptoic acid compounds.

[0045] Specifically, the catalyst is one of concentrated sulfuric acid, p-toluenesulfonic acid, and concentrated phosphoric acid, and the amount used is 3 to 6% of the total mass of tetrahydroxyethylethylenediamine and amino mercaptoic acid compounds.

[0046] Specifically, the dehydrating agent is one of benzene or toluene, and the amount used is 15-25% of the total mass of the polyol amine, diunsaturated acid or acid anhydride.

[0047] Specifically, the molar ratio of the primary amine chain transfer agent, amino polyethylene glycol methyl ether, diunsaturated carboxylic acid or anhydride, unsaturated polyol ether, initiator, and reducing agent is 1:(84-108):(84-108):(240-624):(47-140):(3-10), wherein the molar ratio of amino polyethylene glycol methyl ether to diunsaturated carboxylic acid or anhydride is 1:1.

[0048] Specifically, the structural formula of the amino-polyethylene glycol methyl ether is as follows: The degree of polymerization (p) is an integer ranging from 67 to 135, and is commercially available from Nanjing Juke Biotechnology Co., Ltd.

[0049] Specifically, the diunsaturated carboxylic acid or anhydride is one of maleic acid, fumaric acid, and maleic anhydride.

[0050] Specifically, the unsaturated polyol ether is one of glycerol allyl ether, (allyloxy)propanediol, and pentaerythritol allyl ether.

[0051] Specifically, the initiator is one of hydrogen peroxide, ammonium persulfate, sodium persulfate, and potassium persulfate.

[0052] Specifically, the reducing agent is one of sodium bisulfite, sodium formaldehyde sulfoxylate, sodium ascorbate, and isoascorbic acid.

[0053] The specific implementation also provides the application of multi-arm polymer cement grinding aid in the final grinding process of cement vertical mill.

[0054] As a preferred embodiment, the dosage of the multi-arm polymer cement grinding aid is 0.10 wt% of the total mass of all cement raw materials.

[0055] As a preferred embodiment, the multi-arm polymer cement grinding aid is added uniformly to the cement raw material entering the mill or uniformly to the grinding disc of the vertical mill.

[0056] Example 1

[0057] (1) Preparation of primary amine chain transfer agent: 1.0 mol tetrahydroxyethyl ethylenediamine, 4.0 mol 2-amino-3-mercaptopropionic acid and 1.44 g hydroquinone were added to the reaction vessel in sequence. Under nitrogen protection, the temperature was raised to 60°C and stirred for 15 minutes. The temperature was then raised to 100°C and 21.61 g concentrated sulfuric acid and 108.04 g benzene were added. The reaction was carried out for 3.0 h. During the reaction, the water generated by the reaction was separated by vacuum. After the hydroxyl groups in tetrahydroxyethyl ethylenediamine were completely esterified, the water-carrying agent was removed by vacuum and the temperature was lowered to room temperature to obtain the primary amine chain transfer agent.

[0058] (2) Preparation of multi-arm polymer cement grinding aid: 0.084 mol of amino polyethylene glycol methyl ether with a degree of polymerization of 67, 0.084 mol of maleic acid, 0.001 mol of primary amine chain transfer agent and water were added to the reactor. The mixture was stirred and heated to 30°C. After 15 minutes, 0.047 mol of hydrogen peroxide was added to the reactor. Water was added to adjust the system concentration to 60%. The reaction temperature was maintained at 30°C. At the same time, dropwise addition of feed A consisting of 0.240 mol of glycerol allyl ether aqueous solution and dropwise addition of feed B consisting of 0.003 mol of sodium bisulfite aqueous solution was started. The dropwise addition time was 4.0 h. Then, the mixture was kept at 50°C for 1 h. Water was added to obtain a 40 wt% concentration multi-arm polymer cement grinding aid.

[0059] Example 2

[0060] (1) Preparation of primary amine chain transfer agent: 1.0 mol tetrahydroxyethyl ethylenediamine, 6.0 mol 2-amino-4-mercaptobutyric acid and 10.46 g p-hydroxyanisole were added to the reaction vessel in sequence. Under nitrogen protection, the temperature was raised to 80°C and stirred for 30 minutes. The temperature was then raised to 120°C and 62.78 g p-toluenesulfonic acid and 261.60 g toluene were added. The reaction was carried out for 8.0 h. During the reaction, the water generated by the reaction was separated by vacuum. After the hydroxyl groups in tetrahydroxyethyl ethylenediamine were completely esterified, the water-carrying agent was removed by vacuum and the temperature was lowered to room temperature to obtain the primary amine chain transfer agent.

[0061] (2) Preparation of multi-arm polymer cement grinding aid: 0.108 mol of amino polyethylene glycol methyl ether with a degree of polymerization of 135, 0.108 mol of fumaric acid, 0.001 mol of primary amine chain transfer agent and water were added to the reactor. The mixture was stirred and heated to 50°C. After 30 minutes, 0.140 mol of ammonium persulfate was added to the reactor. Water was added to adjust the system concentration to 80%. The reaction temperature was maintained at 60°C. At the same time, dropwise addition of dropwise additive A consisting of 0.624 mol of (allyloxy) propylene glycol aqueous solution and dropwise additive B consisting of 0.010 mol of sodium formaldehyde sulfoxylate aqueous solution was started. The dropwise addition time was 6.0 h. Then, the mixture was kept at 60°C for 2 h. Water was added to obtain a 70 wt% multi-arm polymer cement grinding aid.

[0062] Example 3

[0063] (1) Preparation of primary amine chain transfer agent: 1.0 mol tetrahydroxyethyl ethylenediamine, 4.3 mol 2-amino-3-mercaptopropionic acid and 2.27 g 2-tert-butylhydroquinone were added to the reaction vessel in sequence. Under nitrogen protection, the temperature was raised to 72°C and stirred for 16 minutes. The temperature was then raised to 115°C and 23.45 g concentrated phosphoric acid and 128.62 g benzene were added. The reaction was carried out for 3.5 h. During the reaction, the water generated by the reaction was separated by vacuum. After the hydroxyl groups in tetrahydroxyethyl ethylenediamine were completely esterified, the dehydrating agent was removed by vacuum and the temperature was lowered to room temperature to obtain the primary amine chain transfer agent.

[0064] (2) Preparation of multi-arm polymer cement grinding aid: 0.092 mol of amino polyethylene glycol methyl ether with a degree of polymerization of 89, 0.092 mol of maleic acid, 0.001 mol of primary amine chain transfer agent and water were added to the reactor. The mixture was stirred and heated to 32°C. After 16 minutes, 0.065 mol of sodium persulfate was added to the reactor. Water was added to adjust the system concentration to 66%. The reaction temperature was maintained at 35°C. At the same time, dropwise addition of feed A consisting of 0.336 mol of pentaerythritol allyl ether aqueous solution and feed B consisting of 0.004 mol of sodium ascorbate aqueous solution was started. The dropwise addition time was 4.5 h. Then, the mixture was kept at 51°C for 1.5 h. Water was added to obtain a multi-arm polymer cement grinding aid with a concentration of 56 wt%.

[0065] Example 4

[0066] (1) Preparation of primary amine chain transfer agent: 1.0 mol tetrahydroxyethyl ethylenediamine, 4.8 mol 2-amino-4-mercaptobutyric acid and 4.42 g 2,6-dinitro-p-cresol were added to the reaction vessel in sequence. Under nitrogen protection, the temperature was raised to 69°C and stirred for 23 minutes. The temperature was then raised to 120°C and 30.95 g concentrated sulfuric acid and 159.18 g benzene were added. The reaction was carried out for 4.7 h. During the reaction, the water generated by the reaction was separated by vacuum. After the hydroxyl groups in tetrahydroxyethyl ethylenediamine were completely esterified, the dehydrating agent was removed by vacuum and the temperature was lowered to room temperature to obtain the primary amine chain transfer agent.

[0067] (2) Preparation of multi-arm polymer cement grinding aid: 0.100 mol of amino polyethylene glycol methyl ether with a degree of polymerization of 72, 0.001 mol of fumaric acid, 0.001 mol of primary amine chain transfer agent and water were added to the reactor. The mixture was stirred and heated to 47°C. After 19 minutes, 0.073 mol of potassium persulfate was added to the reactor. Water was added to adjust the system concentration to 73%. The reaction temperature was maintained at 50°C. At the same time, dropwise addition of dropwise A consisting of 0.504 mol of (allyloxy) propylene glycol aqueous solution and dropwise addition of dropwise B consisting of 0.007 mol of isoascorbic acid aqueous solution was started. The dropwise addition time was 5.5 h. Then the mixture was kept at 53°C for 1.3 h. Water was added to obtain a multi-arm polymer cement grinding aid with a concentration of 62 wt%.

[0068] Example 5

[0069] (1) Preparation of primary amine chain transfer agent: 1.0 mol tetrahydroxyethyl ethylenediamine, 5.1 mol 2-amino-3-mercaptopropionic acid and 5.97 g hydroquinone were added to the reaction vessel in sequence. Under nitrogen protection, the temperature was raised to 65°C and stirred for 28 minutes. The temperature was then raised to 100°C and 40.96 g concentrated phosphoric acid and 196.28 g benzene were added. The reaction was carried out for 6.3 h. During the reaction, the water generated by the reaction was separated by vacuum. After the hydroxyl groups in tetrahydroxyethyl ethylenediamine were completely esterified, the dehydrating agent was removed by vacuum and the temperature was lowered to room temperature to obtain the primary amine chain transfer agent.

[0070] (2) Preparation of multi-arm polymer cement grinding aid: 0.084 mol of amino polyethylene glycol methyl ether with a degree of polymerization of 116, 0.084 mol of maleic acid, 0.001 mol of primary amine chain transfer agent and water were added to the reactor. The mixture was stirred and heated to 36°C. After 23 minutes, 0.068 mol of ammonium persulfate was added to the reactor. Water was added to adjust the system concentration to 79%. The reaction temperature was maintained at 42°C. At the same time, dropwise addition of dropwise additive A consisting of 0.576 mol of (allyloxy) propylene glycol aqueous solution and dropwise additive B consisting of 0.008 mol of sodium formaldehyde sulfoxylate aqueous solution was started. The dropwise addition time was 5.6 h. Then, the mixture was kept at 57°C for 1.8 h. Water was added to obtain a multi-arm polymer cement grinding aid with a concentration of 68 wt%.

[0071] Example 6

[0072] (1) Preparation of primary amine chain transfer agent: 1.0 mol tetrahydroxyethyl ethylenediamine, 5.6 mol 2-amino-4-mercaptobutyric acid and 3.97 g 2-tert-butylhydroquinone were added to the reaction vessel in sequence. Under nitrogen protection, the temperature was raised to 73°C and stirred for 29 minutes. The temperature was then raised to 106°C and 51.60 g p-toluenesulfonic acid and 148.86 g benzene were added. The reaction was carried out for 7.8 h. During the reaction, the water generated by the reaction was separated by vacuum. After the hydroxyl groups in tetrahydroxyethyl ethylenediamine were completely esterified, the dehydrating agent was removed by vacuum and the temperature was lowered to room temperature to obtain the primary amine chain transfer agent.

[0073] (2) Preparation of multi-arm polymer cement grinding aid: 0.108 mol of amino polyethylene glycol methyl ether with a degree of polymerization of 123, 0.108 mol of fumaric acid, 0.001 mol of primary amine chain transfer agent and water were added to the reactor. The mixture was stirred and heated to 49°C. After 20 minutes, 0.098 mol of potassium persulfate was added to the reactor. Water was added to adjust the system concentration to 61%. The reaction temperature was maintained at 53°C. At the same time, dropwise addition of dropwise additive A consisting of 0.440 mol of glycerol allyl ether aqueous solution and dropwise additive B consisting of 0.006 mol of sodium formaldehyde sulfoxylate aqueous solution was started. The dropwise addition time was 5.8 h. Then, the mixture was kept at 58°C for 1.5 h. Water was added to obtain a 50 wt% concentration multi-arm polymer cement grinding aid.

[0074] Example 7

[0075] (1) Preparation of primary amine chain transfer agent: 1.0 mol tetrahydroxyethyl ethylenediamine, 5.9 mol 2-amino-3-mercaptopropionic acid and 5.70 g 2,6-dinitro-p-cresol were added to the reaction vessel in sequence. Under nitrogen protection, the temperature was raised to 61°C and stirred for 16 minutes. The temperature was then raised to 101°C and 56.06 g concentrated sulfuric acid and 190.04 g benzene were added. The reaction was carried out for 8.0 h. During the reaction, the water generated by the reaction was separated by vacuum. After the hydroxyl groups in tetrahydroxyethyl ethylenediamine were completely esterified, the water-carrying agent was removed by vacuum and the temperature was lowered to room temperature to obtain the primary amine chain transfer agent.

[0076] (2) Preparation of multi-arm polymer cement grinding aid: 0.092 mol of amino polyethylene glycol methyl ether with a degree of polymerization of 101, 0.092 mol of maleic anhydride, 0.001 mol of primary amine chain transfer agent and water were added to the reactor. The mixture was stirred and heated to 48°C. After 24 minutes, 0.135 mol of sodium persulfate was added to the reactor. Water was added to adjust the system concentration to 75%. The reaction temperature was maintained at 52°C. At the same time, dropwise addition of dropwise A consisting of 0.312 mol of pentaerythritol allyl ether aqueous solution and dropwise addition of dropwise B consisting of 0.005 mol of sodium ascorbate aqueous solution was started. The dropwise addition time was 4.7 h. Then, the mixture was kept at 60°C for 1.1 h. Water was added to obtain a multi-arm polymer cement grinding aid with a concentration of 63 wt%.

[0077] Example 8

[0078] (1) Preparation of primary amine chain transfer agent: 1.0 mol tetrahydroxyethyl ethylenediamine, 4.5 mol 2-amino-4-mercaptobutyric acid and 8.44 g hydroquinone were added to the reaction vessel in sequence. Under nitrogen protection, the temperature was raised to 79°C and stirred for 30 minutes. The temperature was then raised to 119°C and 50.63 g concentrated sulfuric acid and 210.96 g toluene were added. The reaction was carried out for 5.3 h. During the reaction, the water generated by the reaction was separated by vacuum. After the hydroxyl groups in tetrahydroxyethyl ethylenediamine were completely esterified, the dehydrating agent was removed by vacuum and the temperature was lowered to room temperature to obtain the primary amine chain transfer agent.

[0079] (2) Preparation of multi-arm polymer cement grinding aid: 0.100 mol of amino polyethylene glycol methyl ether with a degree of polymerization of 95, 0.100 mol of maleic anhydride, 0.001 mol of primary amine chain transfer agent and water were added to the reactor. The mixture was stirred and heated to 40°C. After 26 minutes, 0.115 mol of hydrogen peroxide was added to the reactor. Water was added to adjust the system concentration to 70%. The reaction temperature was maintained at 46°C. At the same time, dropwise addition of dropwise A consisting of 0.480 mol of pentaerythritol allyl ether aqueous solution and dropwise addition of dropwise B consisting of 0.003 mol of sodium bisulfite aqueous solution was started. The dropwise addition time was 4.1 h. Then, the mixture was kept at 56°C for 1.9 h. Water was added to obtain a multi-arm polymer cement grinding aid with a concentration of 61 wt%.

[0080] Example 9

[0081] (1) Preparation of primary amine chain transfer agent: 1.0 mol tetrahydroxyethyl ethylenediamine, 5.5 mol 2-amino-3-mercaptopropionic acid and 8.12 g p-hydroxyanisole were added to the reaction vessel in sequence. Under nitrogen protection, the temperature was raised to 62°C and stirred for 24 minutes. The temperature was then raised to 113°C and 40.58 g p-toluenesulfonic acid and 144.29 g toluene were added. The reaction was carried out for 6.4 h. During the reaction, the water generated by the reaction was separated by vacuum. After the hydroxyl groups in tetrahydroxyethyl ethylenediamine were completely esterified, the dehydrating agent was removed by vacuum and the temperature was lowered to room temperature to obtain the primary amine chain transfer agent.

[0082] (2) Preparation of multi-arm polymer cement grinding aid: 0.108 mol of amino polyethylene glycol methyl ether with a degree of polymerization of 108, 0.108 mol of maleic anhydride, 0.001 mol of primary amine chain transfer agent and water were added to the reactor. The mixture was stirred and heated to 45°C. After 27 minutes, 0.123 mol of hydrogen peroxide was added to the reactor. Water was added to adjust the system concentration to 65%. The reaction temperature was maintained at 58°C. At the same time, dropwise addition of dropwise additive A consisting of 0.384 mol of (allyloxy) propylene glycol aqueous solution and dropwise additive B consisting of 0.009 mol of isoascorbic acid aqueous solution was started. The dropwise addition time was 5.3 h. Then, the mixture was kept at 53°C for 1.3 h. Water was added to obtain a 50 wt% concentration multi-arm polymer cement grinding aid.

[0083] Example 10

[0084] (1) Preparation of primary amine chain transfer agent: 1.0 mol tetrahydroxyethyl ethylenediamine, 4.2 mol 2-amino-4-mercaptobutyric acid and 6.43 g hydroquinone were added to the reaction vessel in sequence. Under nitrogen protection, the temperature was raised to 75°C and stirred for 17 minutes. The temperature was then raised to 107°C and 40.17 g concentrated phosphoric acid and 192.80 g benzene were added. The reaction was carried out for 3.9 h. During the reaction, the water generated by the reaction was separated by vacuum. After the hydroxyl groups in tetrahydroxyethyl ethylenediamine were completely esterified, the dehydrating agent was removed by vacuum and the temperature was lowered to room temperature to obtain the primary amine chain transfer agent.

[0085] (2) Preparation of multi-arm polymer cement grinding aid: 0.084 mol of amino polyethylene glycol methyl ether with a degree of polymerization of 69, 0.084 mol of fumaric acid, 0.001 mol of primary amine chain transfer agent and water were added to the reactor. The mixture was stirred and heated to 38°C. After 29 minutes, 0.109 mol of ammonium persulfate was added to the reactor. Water was added to adjust the system concentration to 63%. The reaction temperature was maintained at 45°C. At the same time, dropwise addition of dropwise A consisting of 0.472 mol of glycerol allyl ether aqueous solution and dropwise B consisting of 0.005 mol of sodium ascorbate aqueous solution was started. The dropwise addition time was 5.0 h. Then, the mixture was kept at 59°C for 1.6 h. Water was added to obtain a multi-arm polymer cement grinding aid with a concentration of 52 wt%.

[0086] The performance of the multi-arm polymer cement grinding aids prepared in Examples 1 to 10 above was tested and evaluated.

[0087] 1. Water solubility test and molecular weight test

[0088] A total volume of 100 mL of sample and distilled water was mixed in a 1:2 ratio and placed in a colorimetric tube. The tube was sealed tightly and shaken well. The tube was then placed in a 20°C constant temperature apparatus. The time was recorded. After 30 minutes, the colorimetric tube was removed and placed together with another colorimetric tube containing 100 mL of distilled water against a black background. A spectrophotometer was used to observe the water solubility test results axially. The water solubility of the multi-arm polymer cement grinding aids prepared in Examples 1 to 10 was tested. The molecular weight of the synthesized samples was determined using a Waters 1515 gel permeation chromatograph (Waters Corporation, USA). The mobile phase was 0.1 mol / L NaNO₂ solution, the flow rate was 1.0 mL / min, and the stationary phase was a gel-like porous filler. The molecular weight of the multi-arm polymer cement grinding aids prepared in Examples 1 to 10 was tested. The water solubility and molecular weight test results are shown in Table 1 below.

[0089] Table 1

[0090]

[0091]

[0092] As can be seen from Table 1, the multi-arm polymer cement grinding aid was clear after being mixed with water, indicating that the multi-arm polymer cement grinding aid has good water solubility, and also indicating that the prepared primary amine chain transfer agent has good water solubility. The prepared multi-arm polymer cement grinding aid is within the designed molecular weight range, indicating that the polymerization reaction proceeded efficiently according to the preparation method and the target product was effectively generated.

[0093] 2. Performance Evaluation

[0094] The grinding performance of the grinding aid was evaluated in the vertical mill grinding stage of the cement production process at Huaxin Cement Chongqing Fuling Co., Ltd. The mill was designed to have a capacity of 170 t / h, model HXLM4300.0, with a grinding disc diameter of 4300 cm and four grinding rollers. The cement mix ratio was: clinker 80%, slag 10%, limestone 5%, and gypsum 5%. The mill feed rate, bed thickness, reducer vibration, specific surface area of ​​the cement exiting the mill, and fineness of the residue on a 45 μm sieve were tested in a blank group without grinding aid, a control group with 1 t / h of water spray, a group with 0.10 wt% commercially available cement grinding aid, a group with 0.10 wt% commercially available polycarboxylate polymer, and a group with 0.10 wt% of the multi-arm polymer cement grinding aid prepared in Examples 1 to 10. The results are shown in Table 2. The mill feed rate, bed thickness, and reducer vibration were obtained through data acquisition from the mill's operating system. The specific surface area of ​​the cement exiting the mill was tested according to GB / T 8074-2008 "Determination of Specific Surface Area of ​​Cement - Blaine Method"; the fineness of the cement residue on a 45μm sieve was tested according to GB / T1345-2005 "Test Method for Fineness of Cement - Sieve Analysis Method". Commercially available cement grinding aids are commonly used in cement ball mills, with polyol amines, polyols, and inorganic salts as their main components. Commercially available polycarboxylate polymers are polymers with a comb-like structure obtained through polymerization of acrylic acid and methyl allyl alcohol polyoxyethylene ether as the main raw materials.

[0095] Table 2

[0096]

[0097]

[0098] As shown in Table 2, compared with the blank group, the water-sprayed control group, the group with commercially available cement grinding aid, and the group with commercially available polycarboxylate polymer, the multi-arm polymer cement grinding aid prepared in this invention significantly increased the feed rate of the vertical mill, improved the grinding efficiency of the vertical mill, and increased the cement output of the vertical mill; the material layer thickness of the vertical mill was significantly increased, the vibration of the reducer was significantly reduced, and the operating stability of the vertical mill was improved; the specific surface area of ​​the cement exiting the mill was significantly increased, and the fineness of the residue on the 45μm sieve was significantly reduced, indicating that the cement was ground more finely. The above data demonstrate that the multi-arm polymer cement grinding aid prepared in this invention has a significant grinding aid effect on the vertical mill.

[0099] The effects of grinding aids on cement performance were evaluated by testing the particle morphology, standard consistency water consumption, paste fluidity and 1-hour loss, and 3-day and 28-day compressive strength of cement produced by the blank group without grinding aid, the control group with 1 t / h of water spraying, the group with 0.10 wt% commercial cement grinding aid, the group with 0.10 wt% commercial polycarboxylate polymer, and the group with 0.10 wt% multi-arm polymer cement grinding aid prepared in Examples 1 to 10. The results are shown in Table 3. Among them, the morphology of cement particles was observed using a JSM-35C SEM, and the particle sphericity coefficient was statistically calculated using computer-equipped software; the standard consistency water requirement test was conducted in accordance with GB / T 1346-2011 "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement"; the fluidity and 1-hour loss of cement paste were tested in accordance with GB / T 8077-2012 "Test Methods for Homogeneity of Concrete Admixtures", and the dosage of polycarboxylate superplasticizer was fixed at 0.12% of the cement content; the 3-day and 28-day compressive strength tests were conducted in accordance with GB / T 17671-1999 "Test Methods for Strength of Cement Mortar (ISO Method)".

[0100] Table 3

[0101]

[0102] Table 2 shows that, compared with the blank group, the water-sprayed control group, the group with commercially available cement grinding aid, and the group with commercially available polycarboxylate polymer, the multi-arm polymer cement grinding aid prepared in this invention significantly improved the roundness coefficient of the cement produced by the vertical mill, improved the particle morphology of the cement, making it more rounded, which is more conducive to reducing the standard consistency water consumption and improving the workability and strength of the cement; it significantly reduced the standard consistency water consumption and increased the fluidity of the cement paste and the 1-hour paste fluidity, indicating a significant improvement in the workability of the cement; it significantly improved the 3-day and 28-day compressive strength of the cement, indicating a good reinforcing effect. The above data demonstrate that the multi-arm polymer cement grinding aid prepared in this invention can significantly improve the particle morphology of cement ground in a vertical mill, and enhance the workability and strength of the cement.

Claims

1. A multi-arm polymer cement grinding aid, characterized in that... The multi-arm polymer has the following molecular structure: Wherein, R is either methylene or ethylene; X is hydroxyl, Y is hydrogen; or X is hydroxymethyl, Y is hydroxymethyl; degree of polymerization p is an integer from 67 to 135; degree of polymerization m is an integer from 30 to 78; degree of polymerization n is an integer from 10 to 13; The preparation method of the multi-arm polymer cement grinding aid includes the following steps: (1) Preparation of primary amine chain transfer agent: Tetrahydroxyethyl ethylenediamine, amino mercapto acid compound and polymerization inhibitor are mixed and stirred and heated to 100~120℃. A catalyst and dehydrating agent are added for esterification reaction for 3~8h. During the reaction, the water generated by the reaction is separated by vacuum method. After the reaction, the primary amine chain transfer agent is obtained by purification treatment. (2) Preparation of multi-arm polymer cement grinding aid: Mix amino polyethylene glycol methyl ether, diunsaturated carboxylic acid or anhydride, primary amine chain transfer agent, and water, stir and heat to 30~50℃, add initiator; maintain reaction temperature at 30~60℃, and simultaneously add unsaturated polyol ether aqueous solution and reducing agent aqueous solution dropwise for 4~6h; keep warm at 50~60℃ for 1~2h, add water to obtain 40~70wt% multi-arm polymer cement grinding aid.

2. The multi-arm polymer cement grinding aid as described in claim 1, characterized in that... The weight-average molecular weight of the multi-arm polymer is 293,000 to 742,000 g / mol.

3. The multi-arm polymer cement grinding aid as described in claim 1, characterized in that... In step (1), the molar ratio of tetrahydroxyethyl ethylenediamine and amino mercaptoic acid compound is 1:(4~6); the amount of polymerization inhibitor is 0.2~1% of the total mass of tetrahydroxyethyl ethylenediamine and amino mercaptoic acid compound; the amount of catalyst is 3~6% of the total mass of tetrahydroxyethyl ethylenediamine and amino mercaptoic acid compound; and the amount of dehydrating agent is 15~25% of the total mass of tetrahydroxyethyl ethylenediamine and amino mercaptoic acid compound.

4. The multi-arm polymer cement grinding aid as described in claim 1, characterized in that... The amino mercapto acid compound mentioned in step (1) is one of 2-amino-3-mercaptopropionic acid and 2-amino-4-mercaptobutyric acid; the polymerization inhibitor is one of hydroquinone, p-hydroxyanisole, 2-tert-butylhydroquinone, and 2,6-dinitro-p-cresol or any mixture thereof; the catalyst is one of concentrated sulfuric acid, p-toluenesulfonic acid, and concentrated phosphoric acid or any mixture thereof; and the dehydrating agent is one of benzene and toluene or any mixture thereof.

5. The multi-arm polymer cement grinding aid as described in claim 1, characterized in that... The molar ratio of the primary amine chain transfer agent, amino polyethylene glycol methyl ether, diunsaturated carboxylic acid or anhydride, unsaturated polyol ether, initiator and reducing agent in step (2) is 1:(84~108):(84~108):(240~624):(47~140):(3~10), wherein the molar ratio of amino polyethylene glycol methyl ether to diunsaturated carboxylic acid or anhydride is 1:

1.

6. The multi-arm polymer cement grinding aid as described in claim 1, characterized in that... The structural formula of the amino-polyethylene glycol methyl ether is: The degree of polymerization p is an integer from 67 to 135; the diunsaturated carboxylic acid or anhydride is one or any mixture of maleic acid, fumaric acid, and maleic anhydride; the unsaturated polyol ether is one of glycerol allyl ether and pentaerythritol allyl ether; the initiator is one or any mixture of hydrogen peroxide, ammonium persulfate, sodium persulfate, and potassium persulfate; the reducing agent is one or any mixture of sodium bisulfite, sodium formaldehyde sulfoxylate, sodium ascorbate, and isoascorbic acid.

7. The application of the multi-arm polymer cement grinding aid according to claim 1 in the final grinding process of a cement vertical mill.

8. The application of the multi-arm polymer cement grinding aid as described in claim 7 in the final grinding process of a cement vertical mill, characterized in that... The dosage of the multi-arm polymer cement grinding aid is 0.08~0.20 wt% of the total mass of all cement raw materials.

9. The application of the multi-arm polymer cement grinding aid as described in claim 7 in the final grinding process of a cement vertical mill, characterized in that... The multi-arm polymer cement grinding aid is added uniformly to the cement raw material entering the mill or uniformly to the grinding disc of the vertical mill.

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