A phosphate ester functional monomer, its preparation method and application

Abstract

This invention relates to the field of cement-based building material admixtures, and in particular to a phosphate ester functional monomer, its preparation method, and its application. By introducing a silicon-based network structure on the basis of phosphate groups, the range of tail groups of the functional monomer is further expanded, and the steric hindrance effect is improved, making it difficult for it to enter the soil interlayer. On the other hand, the tail siloxane groups can be hydrolyzed in water to form silanols, whose hydrolysis rate and activity are stronger than those of phosphate ester groups, and can increase the adsorption charge density of water-reducing agents, further improving the adsorption capacity of water-reducing agent molecules for cement particles, thereby improving the dispersibility of cement.

Description

Technical Field

[0001] This invention relates to the field of cement-based building material admixtures, and in particular to a phosphate ester functional monomer, its preparation method, and its application. Background Technology

[0002] Polycarboxylate superplasticizers are widely used in various construction projects due to their advantages such as high water reduction rate, low shrinkage rate, environmental friendliness, and strong structural design flexibility. In recent years, with large-scale infrastructure construction and increased environmental protection efforts, natural sand and gravel resources for concrete are becoming increasingly scarce, leading to a surge in the market of inferior sand and gravel containing clay. However, the use of polycarboxylate superplasticizers in the presence of clay can cause excessive adsorption of their active ingredients, resulting in a significant decrease in the workability, water reduction rate, slump retention, and later shrinkage performance of fresh concrete. Existing technologies commonly address the impact of clay on superplasticizers by introducing sacrificial agents and reducing the adsorption of superplasticizer molecules by clay. However, the effect of compounded sacrificial agents is limited. Introducing anti-clay functional monomers, which have a better controllable range for reducing the adsorption of superplasticizer molecules by clay, is widely used in polycarboxylate superplasticizers.

[0003] Generally, the effect of water-reducing agent molecules and free water on ready-mixed concrete is weakened because they are adsorbed on the surface or between layers of clay. Introducing functional groups with better clay tolerance or stronger cement adsorption into their molecular structure can effectively improve the clay adsorption resistance of water-reducing agent molecules, such as phosphate groups and sulfonic acid groups. Common phosphate groups, when introduced into polycarboxylate water-reducing agent molecules, provide greater steric hindrance and preferentially adsorb onto the surface of cement particles compared to carboxyl groups, reducing the clay's sensitivity to the water-reducing agent. However, most phosphate groups have relatively few adsorption sites on cement particles. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a phosphate ester functional monomer. By introducing a silicon-based network structure on the basis of phosphate groups, the range of tail groups of the functional monomer is further expanded, and the steric hindrance effect is improved, making it difficult for it to enter the soil interlayer. On the other hand, the tail siloxane groups can be hydrolyzed in water to form silanols, which have a higher hydrolysis rate and activity than phosphate ester groups. They can also increase the adsorption charge density of water-reducing agents, further improving the adsorption capacity of water-reducing agent molecules for cement particles, thereby improving the dispersibility of cement.

[0005] Specifically, the preparation method of the phosphate ester functional monomer of the present invention includes the following steps:

[0006] 1) Weigh each raw material according to its weight.

[0007] 2) Add the polyol and polymerization inhibitor to the reactor, stir, and heat.

[0008] 3) Add unsaturated acid and catalyst A to the reactor, stir, heat, maintain the temperature, and introduce nitrogen gas into the reactor to remove moisture generated during the reaction.

[0009] 4) Add phosphoric acid to the reactor, continue the reaction, cool, and obtain an unsaturated phosphate intermediate.

[0010] 5) Prepare an aqueous solution of silicate ester with a mass concentration of 85-95%, add acidic catalyst B for hydrolysis and condensation, heat and purge with nitrogen to remove water, add unsaturated phosphate intermediate, heat and stir to react, cool, and the product is obtained.

[0011] Preferably, the weight of each raw material in step 1) is: 5-100 parts of polyol, 0.1-1.5 parts of polymerization inhibitor, 5-15 parts of unsaturated acid, 0.1-2 parts of catalyst A, 6-12 parts of phosphoric acid, 20-80 parts of silicate ester, and 0.1-2 parts of acidic catalyst B.

[0012] Preferably, step 2) involves heating to 55-65°C.

[0013] Preferably, in step 3), the temperature is heated to 120-140℃ and kept warm for 5-8 hours.

[0014] Preferably, step 4) continues the reaction for 2-5 hours.

[0015] Preferably, in step 5), hydrolysis is carried out at 50-80℃ for 0.5-2 hours, followed by heating to 100℃ and introducing nitrogen gas to remove water, and then heating to 120-150℃ for 3-6 hours.

[0016] Preferably, the polyol is at least one of polyethylene glycol, ethylene glycol, and glycerol.

[0017] Preferably, the polymerization inhibitor is at least one of phenothiazine, hydroquinone, p-hydroxyanisole, 2-tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, and 2,4-dinitro-p-cresol.

[0018] Preferably, the unsaturated acid is at least one selected from acrylic acid, methacrylic acid, and itaconic acid.

[0019] Preferably, catalyst A is at least one of p-toluenesulfonic acid, methanesulfonic acid, 4-dimethylaminopyridine, and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide.

[0020] Preferably, the silicate ester is at least one of tetraethyl orthosilicate, tetrabutyl orthosilicate, tetra(2-methoxy-1-methylethyl) silicate, and isopropyl orthosilicate.

[0021] Preferably, catalyst B is at least one of dibutyltin dilaurate, dimethyl di(methylacyl)ethyltin, and diisopropyl di(methylacyl)ethyltin.

[0022] This invention relates to phosphate ester functional monomers prepared in two main steps, primarily comprising phosphate groups and long silicon-based side chains. Taking polyethylene glycol as the polyol and tetraethyl orthosilicate as the silicate ester as an example, the preparation steps first involve reacting polyethylene glycol with acrylic acid to form an unsaturated ester, followed by phosphorylation to form an unsaturated phosphate ester intermediate. Then, tetraethyl orthosilicate is partially hydrolyzed and polycondensed, reacting with the unsaturated phosphate ester intermediate to expand the tail structure of the phosphorylated ester monomer. This tail structure possesses a certain network SiO-Si structure and can be hydrolyzed under alkaline or acidic conditions to form highly reactive silanols. When applied to water-reducing agents, this increases their adsorption charge density. Furthermore, the wide tail structure makes it difficult for these monomers to penetrate the interlayer of soil, allowing them to adsorb more readily onto the surface of soil or cement particles, thus improving the anti-mud properties of the water-reducing agent. A detailed reaction diagram is shown below:

[0023] Grafted phosphate groups:

[0024] ①

[0025] Grafted silicon groups

[0026] ②

[0027] Where R is C2H5, R1 is C2H5O, and n is an integer from 3 to 50.

[0028] This invention also relates to phosphate ester functional monomers, specifically, those prepared by the above-described preparation method.

[0029] This invention also relates to the application of the above-mentioned phosphate ester functional monomers in the synthesis of polycarboxylate superplasticizers.

[0030] In existing technologies, phosphate groups have relatively few adsorption sites for cement particles. This invention introduces and expands siloxane groups with more adsorption sites on the basis of phosphate groups, which greatly improves the soil adsorption performance of polycarboxylate superplasticizer. Detailed Implementation

[0031] To demonstrate the technical effectiveness of this invention, functional monomers were prepared, and polycarboxylate superplasticizers were synthesized using them. In a mortar flowability test, montmorillonite with a sand ratio of 1.5% was added. The mortar mix ratio was: 623g of reference cement, 1350g of standard sand, 20.25g of montmorillonite, 240g of water, and 3g of superplasticizer.

[0032] The synthesis process of polycarboxylate superplasticizer is as follows: 350g of isopentenyl alcohol polyoxyethylene ether, 1g of acrylic acid, and 2.5g of sodium hypophosphite are weighed and added to a 500ml four-necked flask, followed by 305g of deionized water. The mixture is mechanically stirred until fully dissolved and used as the bottom of the reactor. 35g of acrylic acid and 15g of functional monomer are weighed and mixed evenly with 32g of deionized water to prepare solution A. 0.15g of reducing agent ferrous sulfate and 0.3g of vitamin C are weighed and mixed with 35g of deionized water to prepare solution B. 3.25g of initiator hydrogen peroxide is weighed and added to the bottom of the reactor. The initial dropping temperature at the bottom of the reactor is controlled between 15-20℃. After stirring for 10 minutes, solutions A and B are simultaneously added to the bottom of the reactor using a dropping device. Solution A is added for 110 minutes, and solution B is added for 120 minutes. After the addition is complete, the mixture is kept at this temperature for 60 minutes. Finally, a certain amount of deionized water is added to adjust the product concentration to 40%, and the mixture is stirred evenly to obtain the final product.

[0033] Example 1

[0034] The preparation method of the functional monomer includes the following steps:

[0035] 1) Weigh each raw material according to its weight.

[0036] 2) Add 20 parts of 200 molecular weight polyethylene glycol and 0.15 parts of hydroquinone to the reactor, stir, and heat to 60°C.

[0037] 3) Add 8 parts acrylic acid and 0.6 parts p-toluenesulfonic acid to the reactor, stir, heat to 135℃, maintain the temperature for 7.5 hours, and purge the reactor with nitrogen gas to remove moisture generated during the reaction.

[0038] 4) Add 9 parts of phosphoric acid to the reactor, continue the reaction for 2 hours, cool, and obtain an unsaturated phosphate intermediate.

[0039] 5) Prepare an aqueous solution of 21 parts tetraethyl orthosilicate with a mass concentration of 85, add 0.1 parts dibutyltin dilaurate and hydrolyze and polycondense at 60°C for 0.5 h, raise the temperature to 100°C and purge with nitrogen to remove water, add unsaturated phosphate intermediate, heat to 120°C and stir to react for 4 h, cool to obtain the final product.

[0040] Tests showed that the initial flowability of the mortar was 290 mm, the flowability after 1 hour was 255 mm, and the flowability after 2 hours was 205 mm.

[0041] Example 2

[0042] The preparation method of the functional monomer includes the following steps:

[0043] 1) Weigh each raw material according to its weight.

[0044] 2) Add 7 parts ethylene glycol and 0.1 parts hydroquinone to the reaction vessel, stir, and heat to 60°C.

[0045] 3) Add 8 parts methacrylic acid and 0.5 parts methanesulfonic acid to the reactor, stir, heat to 130℃, keep at this temperature for 6 hours, and purge the reactor with nitrogen to remove moisture generated during the reaction.

[0046] 4) Add 8 parts of phosphoric acid to the reactor, continue the reaction for 4 hours, cool, and obtain an unsaturated phosphate intermediate.

[0047] 5) Prepare an aqueous solution of 32 parts of butyl orthosilicate with a mass concentration of 90%, add 0.15 parts of dibutyltin dilaurate, and hydrolyze and polycondense at 65°C for 1 hour. Heat to 100°C and purge with nitrogen to remove water. Add unsaturated phosphate intermediate, heat to 130°C and stir to react for 4 hours. Cool to obtain the final product.

[0048] Tests showed that the initial flowability of the mortar was 305 mm, the flowability after 1 hour was 250 mm, and the flowability after 2 hours was 210 mm.

[0049] Comparative Example 1

[0050] The functional monomer is a phosphate monomer, and the preparation method includes the following steps:

[0051] 1) Weigh each raw material according to its weight.

[0052] 2) Add 20 parts of 200 molecular weight polyethylene glycol and 0.15 parts of hydroquinone to the reactor, stir, and heat to 60°C.

[0053] 3) Add 8 parts acrylic acid and 0.6 parts p-toluenesulfonic acid to the reactor, stir, heat to 135℃, maintain the temperature for 7.5 hours, and purge the reactor with nitrogen gas to remove moisture generated during the reaction.

[0054] 4) Add 9 parts of phosphoric acid to the reactor, continue the reaction for 2 hours, cool, and the product is obtained.

[0055] Tests showed that the initial flowability of the mortar was 285 mm, the flowability after 1 hour was 195 mm, and the flowability after 2 hours was 150 mm.

[0056] Comparative Example 2

[0057] The functional monomer consists of 10g of comparative 1 phosphate monomer + 5g of vinyltriacetoxysilane.

[0058] Tests showed that the initial flowability of the mortar was 290 mm, the flowability after 1 hour was 215 mm, and there was no flowability after 2 hours.

[0059] Comparative Example 3

[0060] The functional monomer consists of 10g of 2-acrylamido-2-methylpropanesulfonic acid and 5g of sodium methylallyl sulfonate.

[0061] Tests showed that the mortar had an initial flowability of 280 mm, a flowability of 150 mm after 1 hour, and no flowability after 2 hours.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a phosphate ester functional monomer, characterized in that, Includes the following steps: 1) Weigh each ingredient according to its weight. 2) Add the polyol and polymerization inhibitor to the reactor, stir, and heat. 3) Add unsaturated acid and catalyst A to the reactor, stir, heat, maintain the temperature, and purge the reactor with nitrogen gas to remove moisture generated during the reaction. 4) Add phosphoric acid to the reactor, continue the reaction, cool, and obtain an unsaturated phosphate intermediate. 5) Prepare an aqueous solution of silicate ester with a mass concentration of 85-95%, add acidic catalyst B for hydrolysis and condensation, heat and purge with nitrogen to remove water, add unsaturated phosphate intermediate, heat and stir the reaction, cool to obtain the final product; Step 1) The weight of each raw material is as follows: 5-100 parts of polyol, 0.1-1.5 parts of polymerization inhibitor, 5-15 parts of unsaturated acid, 0.1-2 parts of catalyst A, 6-12 parts of phosphoric acid, 20-80 parts of silicate ester, and 0.1-2 parts of acidic catalyst B.

2. The method for preparing the phosphate ester functional monomer according to claim 1, characterized in that, Step 2) Heat to 55-65℃.

3. The method for preparing the phosphate ester functional monomer according to claim 1, characterized in that, Step 3) Heat to 120-140℃ and keep warm for 5-8 hours.

4. The method for preparing the phosphate ester functional monomer according to claim 1, characterized in that, Step 4) Continue the reaction for 2-5 hours.

5. The method for preparing the phosphate ester functional monomer according to claim 1, characterized in that, Step 5) Hydrolyze and condense at 50-80℃ for 0.5-2h, raise the temperature to 100℃ and introduce nitrogen to remove water, then heat to 120-150℃ and react for 3-6h.

6. The method for preparing the phosphate ester functional monomer according to claim 1, characterized in that, The polyol is at least one of polyethylene glycol, ethylene glycol, and glycerol; the polymerization inhibitor is at least one of phenothiazine, hydroquinone, p-hydroxyanisole, 2-tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, and 2,4-dinitro-p-cresol; the unsaturated acid is at least one of acrylic acid, methacrylic acid, and itaconic acid; and the catalyst A is at least one of p-toluenesulfonic acid, methanesulfonic acid, 4-dimethylaminopyridine, and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide.

7. The method for preparing the phosphate ester functional monomer according to claim 1, characterized in that, The silicate ester is at least one of tetraethyl orthosilicate, tetrabutyl orthosilicate, tetra(2-methoxy-1-methylethyl) silicate, and isopropyl orthosilicate, and the catalyst B is at least one of dibutyltin dilaurate, dimethyl di(methylacyl)ethyltin, and diisopropyl di(methylacyl)ethyltin.

8. A phosphate ester functional monomer, characterized in that, It is prepared by the preparation method described in any one of claims 1-7.

9. The application of the phosphate ester functional monomers of claim 8 in the synthesis of polycarboxylate superplasticizers.

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