Polymer type concrete anti-mud agent, its preparation method and application

Abstract

The application discloses a polymer type concrete anti-mud agent, a preparation method and application thereof. The chemical structure of the polymer type concrete anti-mud agent is that a quaternary ammonium salt group with a positive charge and a flexible polyether long chain are covalently connected on a polyvinyl alcohol structure unit; the polymerization degree of the polyvinyl alcohol is 100-1000; and the flexible polyether long chain segment contains 10-100 ethylene oxide repeating units. Compared with a traditional concrete anti-mud agent, the polymer type concrete anti-mud agent has stronger adsorption capacity on clay, can more effectively reduce the adsorption of polycarboxylate water reducing agent on clay, and can more significantly improve the fluidity of fresh concrete.

Description

Technical Field

[0001] This invention relates to a polymer-based concrete anti-mud agent, its preparation method and application, belonging to the field of concrete admixtures. Background Technology

[0002] With the widespread use of manufactured sand and the decline in the quality of aggregate materials, the clay (montmorillonite, illite, kaolin, etc.) and stone powder contained in these materials have been a persistent problem for the concrete and admixture industries. Clay can adsorb large amounts of polycarboxylate superplasticizers, leading to a decrease in the effective content of polycarboxylate superplasticizers in cement systems and a reduction in the fluidity of fresh concrete. Montmorillonite, in particular, exhibits a strong adsorption capacity for polycarboxylate superplasticizers. The polyether side chains of polycarboxylate superplasticizers can undergo intercalation adsorption on montmorillonite through hydrogen bonding (Cement and Concrete Research, 2012, 42, 847–854; Cement and Concrete Research, 2014, 60, 6–10). The maximum adsorption capacity of polycarboxylate superplasticizers on montmorillonite is 415 mg / g, approximately 100 times that of ordinary Portland cement. To ensure the fluidity of fresh concrete, the dosage of polycarboxylate superplasticizers must be increased, thereby raising the cost of admixtures.

[0003] To address this issue, based on the competitive adsorption mechanism, anti-mud admixtures (adsorption sacrificial agents) have been developed. When used in combination with water-reducing agents, these products can significantly improve concrete fluidity, thereby reducing the adsorption amount of water-reducing agents. Since montmorillonite primarily carries a negative charge, the most frequently reported method is to utilize cationic polymers (CN107936208B, CN112961272A, CN112979206A) or cationic small molecules (CN108997146A; Journal of the Chinese Ceramic Society, 2019, 47, 178–183; Journal of the Chinese Ceramic Society, 2020, 48, 1310–1316) as anti-mud agents. These agents adsorb onto montmorillonite through electrostatic interactions, thereby reducing the adsorption amount of polycarboxylate superplasticizers. Alternatively, flexible long-chain molecules with strong hydrogen bonding (such as polyethylene glycol) can be intercalated and adsorbed onto montmorillonite to reduce the adsorption amount of polycarboxylate superplasticizers; however, this method has been less frequently reported. However, both of the above methods have drawbacks such as high dosage, high cost, and unstable anti-sludge effect. Developing concrete anti-sludge agents that combine electrostatic adsorption and intercalation adsorption through molecular design is expected to provide better anti-sludge performance, but research in this area is currently scarce. Summary of the Invention

[0004] To address the shortcomings of existing anti-mud agents, such as high dosage and unstable anti-mud effect, this invention provides a polymer-based concrete anti-mud agent, its preparation method, and its application. Chemically, it is a polymer containing multiple positively charged quaternary ammonium salt groups and multiple flexible polyether chains. Compared to the single adsorption mechanism of traditional anti-mud agents, this invention combines electrostatic adsorption and intercalation adsorption mechanisms on clays such as montmorillonite. This allows for better competitive adsorption with polycarboxylate superplasticizers at lower dosages, more effectively improving the fluidity of fresh concrete. This reduces the actual dosage of polycarboxylate superplasticizer used, effectively lowering costs and improving economic efficiency.

[0005] This invention provides a polymer-type concrete anti-mud agent, the polymer structure of which is a polyvinyl alcohol structural unit covalently modified and linked with a positively charged quaternary ammonium salt group and a flexible polyether long chain.

[0006] The degree of polymerization of the polyvinyl alcohol is 100 to 1000;

[0007] The structural formula of the flexible polyether long chain is -O(CH2CH2O). n H, where n is an integer from 10 to 100.

[0008] The quaternary ammonium salt groups can electrostatically adsorb onto clay, while the long polyether chains can intercalate and adsorb onto clay. Combining these two adsorption mechanisms effectively improves the adsorption capacity of molecules on clay. Furthermore, by covalently linking multiple adsorption units through a polymer, the adsorption efficiency is significantly enhanced.

[0009] The polymer-type concrete anti-mud agent of the present invention has a structure conforming to the following general formula (I):

[0010]

[0011] Where m is an integer from 100 to 1000, n is an integer from 10 to 100, and R is methyl or ethyl.

[0012] The polymer-type concrete anti-mud agent of the present invention is achieved using a reaction type known in the art. First, epoxy halopropane is reacted with trialkylamine to generate a positively charged compound A. Then, polyvinyl alcohol is used in the presence of a catalyst to cause the epoxy groups in compound A to undergo a ring-opening reaction, resulting in compound B. Next, ethylene oxide is introduced to react with the hydroxyl groups in compound B to undergo a ring-opening polymerization reaction, causing compound B to acquire multiple flexible polyether long chains, thus obtaining the polymer-type concrete anti-mud agent of the present invention.

[0013] The epoxy halopropane conforms to the following general formula (II):

[0014]

[0015] Where X = Cl or Br;

[0016] The trialkylamine conforms to the following general formula (III):

[0017]

[0018] Wherein, R is methyl or ethyl;

[0019] The compound A conforms to the following general formula (IV):

[0020]

[0021] The polyvinyl alcohol conforms to the following general formula (V):

[0022]

[0023] Where m = an integer from 100 to 1000;

[0024] The compound B conforms to the following general formula (VI):

[0025]

[0026] The epoxy halopropane is selected from either epichlorohydrin (X=Cl) or epibromopropane (X=Br);

[0027] The trialkylamine is selected from either trimethylamine or triethylamine;

[0028] The degree of polymerization m of the polyvinyl alcohol is between 100 and 1000;

[0029] The catalyst is selected from any one of sodium hydride, sodium methoxide, and sodium tert-butoxide;

[0030] The molar ratio of the epoxy halopropane to the trialkylamine is 1:(1-1.2);

[0031] The molar ratio of polyvinyl alcohol, compound A, catalyst, and ethylene oxide is 1:(m~1.2m):(0.01m~0.1m):(10m~100m).

[0032] The synthesis route is shown below:

[0033]

[0034] The preparation method of the polymer-based concrete anti-sludge agent of the present invention includes the following steps:

[0035] (1) Preparation of compound A: Epoxy halopropane and trialkylamine were dissolved in tetrahydrofuran and reacted at 60-70°C for 1-3 days. The solvent was removed by distillation to obtain compound A.

[0036] (3) Polymer-type concrete anti-mud agent: Polyvinyl alcohol, compound A and catalyst are placed in a high-pressure reactor and reacted at 120-140°C for 20-40 minutes to obtain compound B; then ethylene oxide is introduced and reacted for 1-3 hours to obtain the polymer-type concrete anti-mud agent of the present invention.

[0037] The polymer-type concrete anti-mud agent of this invention is dissolved in water along with other concrete admixtures to obtain an admixture aqueous solution, which is then added to the concrete and stirred. The recommended dosage is 0.1-1% of the total mass of the adhesive.

[0038] The polymer-type concrete anti-mud agent of the present invention has a stronger adsorption capacity on clay compared with traditional concrete anti-mud agents, and can more effectively reduce the adsorption of polycarboxylate superplasticizer on clay, thereby significantly improving the fluidity of fresh concrete. Detailed Implementation

[0039] All materials used in this invention are commercially available chemical products. All reagents (chemically pure) used in the synthesis of concrete anti-mud agent were purchased from Anaiji Technology Co., Ltd., organic solvents (chemically pure) were purchased from Sinopharm Chemical Reagent Co., Ltd., and polycarboxylate superplasticizer was from Jiangsu Subote New Material Co., Ltd.

[0040] Synthesis Example 1

[0041] The preparation method of the polymer-based concrete anti-sludge agent of the present invention includes the following steps:

[0042] (1) Dissolve 100 mmol of epichlorohydrin and 100 mmol of trimethylamine in 50 mL of tetrahydrofuran, react at 60 °C for 1 day, and remove the solvent by distillation to obtain compound A;

[0043] (2) Place 1 mmol of polyvinyl alcohol (m=100), 110 mmol of compound A and 5 mmol of sodium hydride in a high-pressure reactor and react at 120°C for 20 minutes to obtain compound B; then introduce 1 mol of ethylene oxide and react for 1 hour to obtain the polymer-type concrete anti-mud agent 1 (m=100, X=Cl, R=methyl, n=10) of the present invention.

[0044] Synthesis Example 2

[0045] The preparation method of the polymer-based concrete anti-sludge agent of the present invention includes the following steps:

[0046] (1) Dissolve 100 mmol of epichlorohydrin and 110 mmol of trimethylamine in 50 mL of tetrahydrofuran, react at 65 °C for 2 days, remove the solvent by distillation, and obtain compound A;

[0047] (2) 1 mmol of polyvinyl alcohol (m=500), 550 mmol of compound A and 25 mmol of sodium methoxide were placed in a high-pressure reactor and reacted at 130°C for 30 minutes to obtain compound B; then 25 mol of ethylene oxide was introduced and reacted for 2 hours to obtain the polymer-type concrete anti-mud agent 2 (m=500, X=Cl, R=methyl, n=50) of the present invention.

[0048] Synthesis Example 3

[0049] The preparation method of the polymer-based concrete anti-sludge agent of the present invention includes the following steps:

[0050] (1) Dissolve 100 mmol of epoxypropane and 120 mmol of triethylamine in 50 mL of tetrahydrofuran, react at 70 °C for 3 days, remove the solvent by distillation, and obtain compound A;

[0051] (2) 1 mmol of polyvinyl alcohol (m = 1000), 1.1 mol of compound A and 50 mmol of sodium tert-butoxide were placed in a high-pressure reactor and reacted at 140°C for 40 minutes to obtain compound B; then 100 mol of ethylene oxide was introduced and reacted for 3 hours to obtain the polymer-type concrete anti-mud agent 3 (m = 1000, X = Br, R = ethyl, n = 100) of the present invention.

[0052] Synthetic Comparative Example 1

[0053] Compound B from Synthesis Example 3 was used as a comparative concrete anti-mud agent 1 (carrying multiple positive charges but without flexible polyether long chains).

[0054] Synthetic Comparative Example 2

[0055] 1 mmol of polyvinyl alcohol (m = 1000) and 50 mmol of sodium tert-butoxide were placed in a high-pressure reactor, and 100 mol of ethylene oxide was introduced at 140°C. The reaction was carried out for 3 hours to obtain the comparative concrete anti-mud agent 2 (with multiple flexible polyether long chains, but without positive charge).

[0056] Application Example 1

[0057] The flowability test of the concrete anti-mud agent was conducted using the following mixture: 300g of Onoda 52.5RPII cement, 1g of montmorillonite, and 90g of water; the water-reducing agent was a 20% solids polycarboxylate water-reducing agent, with a dosage of 1.8g; all concrete anti-mud agents were prepared using the same dosage, consisting of a 1% aqueous solution with 1g added (equivalent to 0.33 parts per ten thousand of the cement mass). The mixture was slowly stirred for 2 minutes, then quickly stirred for 2 minutes before the flowability of the neat paste was tested.

[0058] Mortar flowability test for concrete anti-mud agent: 900g Onoda 52.5RPII cement, 1350g standard sand, 3g montmorillonite, 360g water; water-reducing agent is 20% solids polycarboxylate water-reducing agent, dosage is 3g; all concrete anti-mud agents are prepared with the same dosage, 3g of a 1% aqueous solution (equivalent to 0.33 parts per ten thousand of cement mass). The above mixture is slowly stirred for 3 minutes before the mortar flowability is tested.

[0059] The slump / spread of concrete was tested in accordance with the relevant provisions of the national standard GB / T 8076-2008 "Concrete Admixtures". The water-reducing agent used in this invention is a polycarboxylate water-reducing agent with a solid content of 20%, with a dosage of 52.5g, which is equivalent to 0.2% of the binder weight. The cement used is Onoda 52.5RPII cement; the sand is medium sand with a fineness modulus of Mx = 2.6; and the aggregate is continuously graded crushed stone with a particle size of 5-25mm. The concrete mix proportions are: cement 4.2kg, fly ash 1.05kg, sand 10.98kg, large aggregate 11.55kg, small aggregate 4.95kg, montmorillonite 17.5g, and water 2.26kg. All concrete anti-mud agents were used at the same dosage, prepared as a 1% aqueous solution, with 17.5g added (equivalent to 0.33 parts per ten thousand of the binder weight).

[0060] The concrete anti-mud agents tested were the five concrete anti-mud agent samples prepared in Synthetic Examples 1-3 and Synthetic Comparative Examples 1-2. The experimental results are shown in Table 1.

[0061] Table 1 Comparison of the performance of different concrete anti-mud agents

[0062]

[0063]

[0064] It can be seen that, compared with the blank sample without concrete anti-mud agent, all samples with concrete anti-mud agents 1-3 prepared in this invention showed a significant increase in the fluidity of the cement paste, the fluidity of the mortar, and the slump / spread of the fresh concrete. This indicates that the concrete anti-mud agent of this invention can effectively adsorb on the surface of montmorillonite, thereby reducing the adsorption of polycarboxylate superplasticizer on montmorillonite and increasing the fluidity of the cement paste. Compared with comparative concrete anti-mud agent 1 (which only undergoes electrostatic adsorption with montmorillonite) and comparative concrete anti-mud agent 2 (which only undergoes intercalation adsorption with montmorillonite), the concrete anti-mud agents 1-3 prepared in this invention can further improve the fluidity of the cement paste, indicating that this invention has the synergistic effect of both electrostatic adsorption and intercalation adsorption mechanisms, which is more effective than the traditional single adsorption mechanism and the anti-mud effect is more obvious.

Claims

1. A polymer-based concrete anti-sludge agent, characterized in that: Its chemical structure consists of a positively charged quaternary ammonium salt group and a flexible polyether long chain covalently modified and linked to a polyvinyl alcohol structural unit; The degree of polymerization of the polyvinyl alcohol is 100~1000; The structural formula of the flexible polyether long chain is -O(CH2CH2O). n H, where n = an integer from 10 to 100; The polymer-based concrete anti-mud agent has a structure conforming to the following general formula (Ⅰ): （Ⅰ） Where m = an integer from 100 to 1000, n = an integer from 10 to 100, and R is methyl or ethyl.

2. The method for preparing a polymer-based concrete anti-mud agent according to claim 1, characterized in that, First, epoxide halopropane is reacted with trialkylamine to generate a positively charged compound A; then, polyvinyl alcohol is used in the presence of a catalyst to cause the epoxy groups in compound A to undergo a ring-opening reaction, yielding compound B; then, ethylene oxide is introduced to react with the hydroxyl groups in compound B to undergo a ring-opening polymerization reaction, causing compound B to acquire multiple flexible polyether long chains, thus obtaining the polymer-type concrete anti-mud agent.

3. The method for preparing a polymer-based concrete anti-sludge agent according to claim 2, characterized in that, The epoxy halopropane conforms to the following general formula (II): （Ⅱ） Where X = Cl or Br; The trialkylamine conforms to the following general formula (III): Wherein, R is methyl or ethyl; The compound A conforms to the following general formula (Ⅳ): （Ⅳ）； The polyvinyl alcohol conforms to the following general formula (V): （Ⅴ） Where m = an integer from 100 to 1000; The compound B conforms to the following general formula (VI): （Ⅵ）。 4. The preparation method of a polymer-based concrete anti-sludge agent according to claim 3, characterized in that, The epoxy halopropane is selected from either epichlorohydrin or epibromopropane.

5. The method for preparing a polymer-based concrete anti-sludge agent according to claim 3, characterized in that, The trialkylamine is selected from either trimethylamine or triethylamine.

6. The method for preparing a polymer-based concrete anti-sludge agent according to claim 3, characterized in that, The catalyst is selected from any one of sodium hydride, sodium methoxide, and sodium tert-butoxide.

7. The method for preparing a polymer-based concrete anti-sludge agent according to claim 3, characterized in that, The molar ratio of the epoxy halopropane to the trialkylamine is 1:(1~1.2). The molar ratio of polyvinyl alcohol, compound A, catalyst, and ethylene oxide is 1:(m~1.2m):(0.01m~0.1m):(10m~100m).

8. A method for preparing a polymer-based concrete anti-sludge agent according to any one of claims 2 to 7, characterized in that, Specifically, the following steps are included: (1) Preparation of compound A: Epoxy halopropane and trialkylamine were dissolved in tetrahydrofuran and reacted at 60-70 °C for 1-3 days. The solvent was removed by distillation to obtain compound A. (2) Polymer-type concrete anti-mud agent: Polyvinyl alcohol, compound A and catalyst are placed in a high-pressure reactor and reacted at 120~140 ℃ for 20~40 minutes to obtain compound B; then ethylene oxide is introduced and reacted for 1~3 hours to obtain the polymer-type concrete anti-mud agent.

9. The application method of the polymer-based concrete anti-mud agent according to claim 1, characterized in that, When using the polymer-type concrete anti-mud agent, it is dissolved in water along with other concrete admixtures and mixed evenly to obtain an admixture aqueous solution, which is then added to the concrete and stirred. The dosage is 0.1 to 1 / 10,000 of the total mass of the adhesive material.

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