A composite surfactant with high dispersion stability for silica ash slurry and preparation method thereof

Abstract

The present invention discloses a composite surfactant with high dispersion stability for silica fume slurry and a preparation method thereof. The components of the composite surfactant and their weight fractions include: 28-30 parts of acrylic acid, 10-12 parts of a homemade polyether surfactant, 6-8 parts of a homemade hydrophobic alkoxysilane, 0.5-1.0 parts of mercaptoacetic acid, 0.3-0.7 parts of ammonium persulfate, 0.05-0.15 parts of ferrous sulfate, 1-2 parts of NaOH, 8-12 parts of a stabilizer, and 215-275 parts of deionized water. The composite surfactant with high dispersion stability for silica fume slurry provided by the present invention can improve the dispersibility and stability of silica fume.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete admixtures, and particularly relates to a composite surfactant with high dispersion stability for silica ash slurry and a preparation method thereof. Background Art

[0002] With the advancement of construction technology, the requirements for concrete in buildings are constantly increasing, promoting the application of concrete in civil engineering construction. Silica fume, also known as silica fume, is a byproduct of the production of silicon metal or ferrosilicon alloys in electric arc furnaces. Its main component is amorphous silicon dioxide, generally accounting for 85% to 96%. Silica fume particles are very fine, with an average particle size of 0.1 to 1 μm, approximately 1 / 100th the size of ordinary cement particles. These properties make silica fume a highly active pozzolanic mineral admixture, commonly used in ultra-high-performance concrete (UHPC).

[0003] Silica fume has two main effects in concrete. One is the filling effect, which fills the gaps in the cement before hardening and the capillary pores between hydration products after hardening. The other is the pozzolanic effect, in which silica fume reacts with calcium hydroxide, one of the hydration products, to form calcium silicate hydrate (CSH) gel, further densifying the concrete. Finally, silica fume provides nucleation sites for the hydration products, further improving the performance of hydrated cement and concrete. Adding silica fume to cement concrete can improve the concrete's strength, impermeability, frost resistance, and chemical corrosion resistance, and can also inhibit or reduce alkali-aggregate reaction.

[0004] Since silica fume particles are too fine, the density is extremely low, and the particles are in a very loose state, the packaging and transportation of the original silica fume are very difficult. There are also problems such as easy dispersion and agglomeration during use. The current treatment method is to densify the original silica fume, and the density after processing can be increased to 900kg / m 3 However, the application of encrypted silica fume in actual production will also bring some problems:

[0005] (1) The high activity and high surface energy of volcanic ash lead to serious agglomeration of silica fume in UHPC;

[0006] (2) In UHPC with a low water-binder ratio, cement and silica fume particles are more likely to attract each other and close spontaneously, resulting in UHPC with lower fluidity and higher viscosity. This problem brings great difficulties to the mixing, pumping, fiber distribution and molding construction of UHPC.

[0007] (3) Densified silica fume has a higher degree of agglomeration than original silica fume. Such agglomerates are often difficult to be effectively dispersed during the conventional cement concrete preparation process. Silica fume agglomerates that are not fully dispersed often absorb water and admixtures, resulting in increased loss of concrete workability and unstable strength changes.

[0008] As can be seen from the above issues, the uniformity of silica fume dispersion in concrete is the main cause of a series of problems, and extensive research has been conducted to address this issue. CN112209646A discloses a high-performance pre-dispersed silica fume slurry and preparation method. This invention uses a multi-component organic dispersant, an inorganic early-strength dispersant, an interfacial tension regulator, and a bubble suppressant to effectively disperse the densified silica fume. While the dispersion effect is good, it simply combines the multi-component surfactants and does not address the selectivity and related mechanisms between the silica fume and the dispersant.

[0009] Silica fume particles agglomerate and are difficult to disperse in concrete systems, hindering their full hydration potential. Therefore, increasing the dispersibility of dense silica fume becomes crucial, and effective dispersion of silica fume in concrete is a pressing issue. Currently, research on the mechanism of silica fume and dispersants is limited. This invention aims to create a silica fume composite surfactant with excellent dispersibility and stabilization properties by combining different organic functional groups. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to provide a composite surfactant with high dispersion stability for silica fume slurry and a preparation method thereof in response to the deficiencies of the prior art. The composite surfactant provided by the present invention can improve the dispersion performance and stability performance of silica fume.

[0011] To achieve the above-mentioned purpose, the technical solution adopted by the present invention to solve the technical problem is:

[0012] A composite surfactant with high dispersion stability for silica ash slurry, comprising the following components and their weight fractions: 28-30 parts of acrylic acid, 10-12 parts of a homemade polyether surfactant, 6-8 parts of a homemade hydrophobic alkoxysilane, 0.5-1.0 part of mercaptoacetic acid, 0.3-0.7 part of ammonium persulfate, 0.05-0.15 part of ferrous sulfate, 1-2 parts of NaOH, 8-12 parts of a stabilizer, and 215-275 parts of deionized water.

[0013] The method for preparing the composite surfactant with high dispersion stability for silica ash slurry comprises the following steps:

[0014] (1) Preparation of solution A and solution B: Solution A is prepared from 28-30 parts of acrylic acid, 0.5-1.0 parts of mercaptoacetic acid, and 40-50 parts of deionized water; Solution B is prepared from 0.3-0.7 parts of ammonium persulfate and 30-40 parts of deionized water;

[0015] (2) adding 1-2 parts of NaOH to 15-20 parts of deionized water and stirring uniformly to obtain a NaOH aqueous solution;

[0016] (3) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser, 10-12 parts of a homemade polyether surfactant, 0.05-0.15 parts of ferrous sulfate, 6-8 parts of a homemade hydrophobic alkoxysilane, and 35-45 parts of deionized water were added in sequence, and the temperature was raised to 85-95°C and maintained at a heating rate of 5-7°C / min;

[0017] (4) The prepared solution A and solution B were respectively pumped into the reaction vessel at a constant speed using a peristaltic pump, with the pumping speed of solution A being 0.45 to 0.54 parts / min and the pumping speed of solution B being 0.19 to 0.22 parts / min, and then stirred in a closed state at 85 to 95°C for 4.5 to 5.5 hours;

[0018] (5) After the reaction is completed, the product is neutralized with the NaOH aqueous solution to adjust the pH value to 7±1, and then allowed to stand and cool to 30-40°C and maintain;

[0019] (6) Add 8 to 12 parts of stabilizer and 95 to 120 parts of deionized water, keep stirring at 30 to 40° C. for 0.5 to 1 hour, and then cool to room temperature to obtain the composite surfactant with high dispersion stability for silica ash slurry.

[0020] In the above scheme, the homemade polyether surfactant includes the following raw materials, calculated by mass: 55-75 parts of polyether surfactant, 45-60 parts of phosphoric acid, 0.3-0.7 parts of catalyst A, and 1-3 parts of sodium carbonate reagent.

[0021] In the above scheme, the polyether surfactant is a mixture of allyl alcohol polyoxyethylene ether, methoxy polyethylene glycol and isoprene polyoxyethylene ether; wherein the mass ratio of allyl alcohol polyoxyethylene ether, methoxy polyethylene glycol and isoprene polyoxyethylene ether is (1.8~3.0):(0.7~1.8):1.

[0022] In the above scheme, the catalyst A is a mixture of 4,4'-azobis(4-cyanovaleric acid) and mercaptoacetic acid, and the mass ratio of the two is 1:1.

[0023] In the above scheme, the sodium carbonate reagent is a sodium carbonate solution with a concentration of 1.2%.

[0024] In the above scheme, the preparation steps of the homemade polyether surfactant are as follows:

[0025] (1) Add 55-75 parts of a polyether surfactant to a three-necked flask equipped with a thermometer and a stirrer, heat to 65-70°C at a heating rate of 5-7°C / min, and maintain for 30-45 minutes;

[0026] (2) Add 0.3-0.7 parts of catalyst A, keep the temperature at 65-70°C and continue stirring for 20-30 minutes; then heat to 90-140°C at a heating rate of 5-7°C / min, and use a peristaltic pump to deliver 45-60 parts of phosphoric acid into the three-necked flask at a constant speed of 1.4-1.6 parts / min. After completion, seal the reaction vessel and keep it warm for 3-5 hours;

[0027] (3) After standing for a while until the temperature drops to 35-45°C, 1-3 parts of sodium carbonate reagent are added dropwise to the three-necked flask to control the pH value of the system between 7 and 8, thereby obtaining the self-made polyether surfactant.

[0028] In the above scheme, the self-made hydrophobic alkoxysilane includes the following raw materials: 30-40 parts of alkynylsilane, 30-40 parts of hydrogen bromide, 5-10 parts of tetrahydrofuran, and 0.3-0.8 parts of catalyst B.

[0029] In the above scheme, the alkynylsilane is 3-(triethoxysilylpropyl)propargylcarbamate.

[0030] In the above scheme, the catalyst B is a mixture of Pd-CaCO3 catalyst and lead acetate, wherein the mass ratio of the Pd-CaCO3 catalyst to the lead acetate is 1:0.4.

[0031] In the above scheme, the preparation steps of the homemade hydrophobic alkoxysilane are as follows:

[0032] 30-40 parts of alkynylsilane, 5-10 parts of tetrahydrofuran and 0.3-0.8 parts of catalyst B are added to a reaction vessel in sequence, and then 30-40 parts of hydrogen bromide gas are introduced and the reaction vessel is sealed. Thereafter, the temperature is raised to 150-160° C. at a constant rate of 5-7° C. / min, and the pressure is raised to 5-8 atmospheres at a constant rate of 0.4-0.5 MPa / h. The constant temperature and pressure are maintained for 5-6 hours, and the self-prepared hydrophobic alkoxysilane is obtained after cooling to room temperature.

[0033] In the above scheme, the tetrahydrofuran is used as an inert solvent, and the hydrogen bromide gas is injected into the reaction container through an air pump.

[0034] In the above solution, the stabilizer is a powdered mixture of xanthan gum and carboxymethyl cellulose, wherein the mass ratio of the xanthan gum to the carboxymethyl cellulose is 1:1.

[0035] In the present invention, a self-made polyether surfactant is obtained by a phosphonate organic reaction between different types of ether surfactants and phosphoric acid, wherein allyl alcohol polyoxyethylene ether (APEG) and isoprene polyoxyethylene ether (TPEG) can be better adsorbed on silica fume, thereby enhancing the dispersibility of silica fume in aqueous solution, and methoxy polyethylene glycol (MPEG) can be better adsorbed on cement, thereby increasing the dispersibility of cement. The three surfactants work together to significantly improve the dispersibility of cement and silica fume, reduce the mutual attraction between cement and silica fume, and reduce the occurrence of agglomeration. The phosphonic acid group has a strong competitive adsorption capacity and can be adsorbed on the surface of cement and silica fume. It has excellent dispersing ability for silica fume with negative surface charge in an alkaline environment and exhibits excellent dispersing performance in cement-silica fume slurry. Based on the phosphonate organic reaction, the ether surfactant is combined with the phosphonic acid group, and the two work together to improve the dispersibility of the cement-silica fume slurry.

[0036] In the present invention, a homemade hydrophobic alkoxysilane is obtained by the addition reaction of 3-(triethoxysilylpropyl) propargyl carbamate and hydrogen bromide, wherein the hydrophobic alkoxysilane group carried by the alkynylsilane can reduce the surface tension of silica fume, reduce the contact angle between water molecules and the surface of silica fume particles, and make it easy for water molecules to penetrate into the interior of silica fume agglomerates; bromide ions have a high affinity for water and can form a water protective film after being effectively adsorbed on the surface of silica fume, thereby reducing the mutual attraction between silica fume itself or cement, reducing its surface energy and thus reducing the occurrence of agglomeration; adding a mixture of Pd-CaCO3 catalyst and lead acetate as the addition reaction catalyst can ensure that the reaction addition is only to olefins, and no further addition is made subsequently.

[0037] Compared with the existing technology, the beneficial effects of the present invention are:

[0038] (1) The present invention provides a composite surfactant with high dispersion stability for silica fume slurry. The composite surfactant can greatly improve the dispersion and stability of silica fume through the synergistic effect of multiple organic groups, alkaline environment and stabilizer components. When applied to concrete, it can significantly improve the problems of unstable strength changes and working performance changes of concrete, further improving its application in concrete. It is environmentally friendly, energy-saving, green and low-carbon, and has broad application prospects.

[0039] (2) The present invention provides a method for preparing a composite surfactant with high dispersion stability for silica fume slurry. The first step of the method is to generate a product by free radical polymerization of acrylic acid, a homemade polyether surfactant and a homemade hydrophobic alkoxysilane. The product has a comb-like shape. The composite surfactant has a polyether group, a phosphonic acid group, a hydrophobic alkoxysilane group and a bromide ion, which can greatly improve the dispersion performance of silica fume in an aqueous solution system.

[0040] (3) The polyether group in the composite surfactant with high dispersion stability for silica ash slurry provided by the present invention cooperates with the alkaline environment. When silica ash is added to cement slurry, the steric hindrance can be increased, the attraction between silica ash can be reduced, and the stability of the system can be achieved. The stabilizer (xanthan gum and carboxymethyl cellulose) has a stronger adsorption capacity for silica ash, so that the dispersed silica particles have a stable viscosity and provide better rheological stability. The stabilizer is combined with the free radical polymerization reaction product to provide excellent stability performance for the cement-silica ash slurry system. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Schematic diagram of the organic reaction of polyether phosphonate esterification in an embodiment of the present invention;

[0042] Figure 2 Schematic diagram of the alkynyl-hydrogen bromide addition reaction in an embodiment of the present invention;

[0043] Figure 3 Schematic diagram of free radical polymerization reaction in an embodiment of the present invention. DETAILED DESCRIPTION

[0044] The technical solution of the present invention will be fully and clearly described below in conjunction with specific embodiments, but the described embodiments are only some embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0045] Example 1

[0046] (1) A composite surfactant with high dispersion stability for silica ash slurry, wherein the components of the composite surfactant and their weight percentages include: 28 parts of acrylic acid, 10 parts of a homemade polyether surfactant, 6 parts of a homemade hydrophobic alkoxysilane, 0.7 parts of mercaptoacetic acid, 0.4 parts of ammonium persulfate, 0.06 parts of ferrous sulfate, 1.2 parts of NaOH, 9 parts of a stabilizer, and 230 parts of deionized water; wherein the stabilizer is a powdered mixture of xanthan gum and carboxymethyl cellulose, and the mass ratio of xanthan gum to the carboxymethyl cellulose is 1:1.

[0047] (2) The self-made polyether surfactant, each component in parts by weight, includes the following ingredients: 57 parts of polyether surfactant, 50 parts of phosphoric acid, 0.4 parts of catalyst A, and 1.6 parts of sodium carbonate reagent; the polyether surfactant is a mixture of APEG, MPEG and TPEG, and the mass ratio of APEG:MPEG:TPEG is 1.8:0.8:1; the catalyst A is a mixture of 4,4'-azobis(4-cyanovaleric acid) (ACVA) and thioglycolic acid (TA), and the mass ratio of the two is 1:1; the sodium carbonate reagent is a sodium carbonate solution with a concentration of 1.2%.

[0048] The preparation method of a homemade polyether surfactant is as follows: add a polyether surfactant to a three-necked flask equipped with a thermometer and a stirrer, heat the temperature to 65°C at a heating rate of 5-7°C / min, and maintain for 30 minutes; add catalyst A, keep the temperature at 65°C and continue stirring for 20 minutes, then continue to heat at a heating rate of 5-7°C / min, and when the temperature reaches 120°C, use a peristaltic pump to deliver phosphoric acid into the three-necked flask at a constant speed, the pumping speed is 1.4-1.6 parts / min, and after the addition is completed, seal the reaction vessel and keep the temperature for 3.5 hours; then start to cool, and when the temperature drops to 35°C, drip a sodium carbonate solution into the three-necked flask to control the pH value of the system at 7, thereby obtaining a homemade polyether surfactant.

[0049] (3) The self-made hydrophobic alkoxysilane comprises the following components in parts by weight: 32 parts of alkynylsilane, 30 parts of hydrogen bromide, 7 parts of tetrahydrofuran, and 0.3 parts of catalyst B; wherein catalyst B is a mixture of Pd-CaCO3 catalyst and lead acetate, and the mass ratio of Pd-CaCO3 catalyst to lead acetate is 1:0.4.

[0050] The preparation method of the homemade hydrophobic alkoxysilane is as follows: alkynylsilane, tetrahydrofuran and catalyst B are added to the reaction vessel in sequence, and then hydrogen bromide gas is introduced and the container is sealed. Heating and pressurizing are started, the temperature is raised to 150°C, the heating rate is 5-7°C / min, and the pressure is raised to 5 atmospheres at a constant rate of 0.4-0.5 MPa / h. The temperature and pressure are maintained for 5 hours, and the homemade hydrophobic alkoxysilane group is obtained after cooling to room temperature.

[0051] (4) The preparation method of the composite surfactant with high dispersion stability for silica ash slurry is as follows:

[0052] Prepare solution A and solution B: Solution A is prepared from 28 parts of acrylic acid (AA), 0.7 parts of thioglycolic acid (TGA) and 40 parts of deionized water; Solution B is prepared from 0.4 parts of ammonium persulfate (APS) and 30 parts of deionized water;

[0053] Add 1.2 parts of weighed NaOH to 20 parts of deionized water and stir evenly to obtain a NaOH aqueous solution;

[0054] In a four-necked flask equipped with a thermometer, a stirrer, and a condenser, 10 parts of a homemade polyether surfactant, 0.06 parts of ferrous sulfate, 6 parts of a homemade hydrophobic alkoxysilane, and 45 parts of deionized water were added in sequence, and the temperature was raised to 90°C and maintained at a heating rate of 5-7°C / min.

[0055] The prepared solution A and solution B were respectively pumped into the reaction vessel at a constant speed using a peristaltic pump. The pumping speed of solution A was 0.45-0.54 parts / min, and the pumping speed of solution B was 0.19-0.22 parts / min. Then, the mixture was kept in a closed state and stirred at 90°C for 4.5 hours.

[0056] After the reaction was completed, the product was neutralized with NaOH aqueous solution, the pH value was adjusted to 8, and the product was allowed to cool to 30°C.

[0057] Finally, add 9 parts of weighed stabilizer and 95 parts of deionized water, maintain stirring at 30° C. for 1 hour, and cool to room temperature to obtain a composite surfactant with high dispersion stability.

[0058] Example 2

[0059] (1) A composite surfactant with high dispersion stability for silica ash slurry, wherein the components of the composite surfactant and their weight percentages include: 30 parts of acrylic acid, 10 parts of a homemade polyether surfactant, 7 parts of a homemade hydrophobic alkoxysilane, 0.9 parts of mercaptoacetic acid, 0.5 parts of ammonium persulfate, 0.08 parts of ferrous sulfate, 1.5 parts of NaOH, 10 parts of a stabilizer, and 243 parts of deionized water; wherein the stabilizer is a powdered mixture of xanthan gum and carboxymethyl cellulose, and the mass ratio of xanthan gum to the carboxymethyl cellulose is 1:1.

[0060] (2) The self-made polyether surfactant, each component in parts by weight, includes the following ingredients: 60 parts of polyether surfactant, 54 parts of phosphoric acid, 0.3 parts of catalyst A, and 2.1 parts of sodium carbonate reagent; the polyether surfactant is a mixture of APEG, MPEG and TPEG, and the mass ratio of APEG:MPEG:TPEG is 2.1:1.0:1; the catalyst A is a mixture of 4,4'-azobis(4-cyanovaleric acid) (ACVA) and thioglycolic acid (TA), and the mass ratio of the two is 1:1; the sodium carbonate reagent is a sodium carbonate solution with a concentration of 1.2%.

[0061] The preparation method of the self-made polyether surfactant in this example is the same as that in Example 1.

[0062] (3) The self-made hydrophobic alkoxysilane includes the following components in parts by weight: 35 parts of alkynylsilane, 32 parts of hydrogen bromide, 6 parts of tetrahydrofuran, and 0.5 parts of catalyst B; wherein catalyst B is a mixture of Pd-CaCO3 catalyst and lead acetate, and the mass ratio of Pd-CaCO3 catalyst to lead acetate is 1:0.4.

[0063] The preparation method of hydrophobic alkoxysilane in this embodiment is consistent with that in Example 1.

[0064] (4) The preparation method of the composite surfactant with high dispersion stability for silica ash slurry is as follows:

[0065] Prepare solution A and solution B: Solution A is prepared from 30 parts of acrylic acid (AA), 0.9 parts of thioglycolic acid (TGA) and 45 parts of deionized water; Solution B is prepared from 0.5 parts of ammonium persulfate (APS) and 33 parts of deionized water;

[0066] Add 1.5 parts of weighed NaOH to 16 parts of deionized water and stir well to obtain a NaOH aqueous solution;

[0067] In a four-necked flask equipped with a thermometer, a stirrer, and a condenser, 10 parts of a homemade polyether surfactant, 0.08 parts of ferrous sulfate, 7 parts of a homemade hydrophobic alkoxysilane, and 35 parts of deionized water were added in sequence, and the temperature was raised to 90°C and maintained at a heating rate of 5-7°C / min.

[0068] The prepared solution A and solution B were respectively pumped into the reaction vessel at a constant speed using a peristaltic pump. The pumping speed of solution A was 0.45-0.54 parts / min, and the pumping speed of solution B was 0.19-0.22 parts / min. Then, the mixture was kept in a closed state and stirred at 90°C for 4.5 hours.

[0069] After the reaction was completed, the product was neutralized with NaOH aqueous solution, the pH value was adjusted to 8, and the product was allowed to cool to 30°C.

[0070] Finally, add 10 parts of weighed stabilizer and 114 parts of deionized water, maintain stirring at 30° C. for 1 hour, and cool to room temperature to obtain a composite surfactant with high dispersion stability.

[0071] Example 3

[0072] (1) A composite surfactant with high dispersion stability for silica ash slurry, wherein the components of the composite surfactant and their weight fractions include: 29 parts of acrylic acid, 10 parts of a homemade polyether surfactant, 8 parts of a homemade hydrophobic alkoxysilane, 0.8 parts of mercaptoacetic acid, 0.6 parts of ammonium persulfate, 0.10 parts of ferrous sulfate, 1.6 parts of NaOH, 12 parts of a stabilizer, and 260 parts of deionized water; wherein the stabilizer is a powdered mixture of xanthan gum and carboxymethyl cellulose, and the mass ratio of xanthan gum to the carboxymethyl cellulose is 1:1.

[0073] (2) The self-made polyether surfactant, each component in parts by weight, includes the following ingredients: 55 parts of polyether surfactant, 50 parts of phosphoric acid, 0.6 parts of catalyst A, and 1.8 parts of sodium carbonate reagent; the polyether surfactant is a mixture of APEG, MPEG and TPEG, and the mass ratio of APEG:MPEG:TPEG is 2.5:1.5:1; the catalyst A is a mixture of 4,4'-azobis(4-cyanovaleric acid) (ACVA) and thioglycolic acid (TA), and the mass ratio of the two is 1:1; the sodium carbonate reagent is a sodium carbonate solution with a concentration of 1.2%.

[0074] The preparation method of a homemade polyether surfactant is as follows: add a polyether surfactant to a three-necked flask with a thermometer and a stirrer, heat the temperature to 70°C, and maintain it for 40 minutes; add catalyst A, keep the temperature at 70°C and continue stirring for 30 minutes, then raise the temperature to 140°C at a heating rate of 5-7°C / min, use a peristaltic pump to deliver phosphoric acid into the reaction container at a constant speed, the pumping speed is 1.4-1.6 parts / min, after the addition is completed, close the reaction container and keep it warm for 4.5 hours; then start cooling, and when the temperature drops to 40°C, add sodium carbonate solution dropwise into the three-necked flask to control the pH value of the system at 7, thereby obtaining a homemade polyether surfactant.

[0075] (3) The self-made hydrophobic alkoxysilane includes the following components in parts by weight: 40 parts of alkynylsilane, 40 parts of hydrogen bromide, 9 parts of tetrahydrofuran, and 0.6 parts of catalyst B; wherein catalyst B is a mixture of Pd-CaCO3 catalyst and lead acetate, and the mass ratio of Pd-CaCO3 catalyst to lead acetate is 1:0.4.

[0076] The preparation method of the homemade hydrophobic alkoxysilane is as follows: alkynylsilane, tetrahydrofuran and catalyst B are added to the reaction vessel in sequence, followed by the introduction of hydrogen bromide gas and the sealing of the container, and heating and pressurization are started. The temperature is raised to 160°C at a heating rate of 5-7°C / min, and the pressure is raised to 7 atmospheres at a constant rate of 0.4-0.5 MPa / h. The temperature and pressure are maintained for 6 hours, and the homemade hydrophobic alkoxysilane group is obtained after cooling to room temperature.

[0077] (4) The preparation method of the composite surfactant with high dispersion stability for silica ash slurry is as follows:

[0078] Prepare solution A and solution B: Solution A is prepared from 29 parts of acrylic acid (AA), 0.8 parts of thioglycolic acid (TGA) and 50 parts of deionized water; Solution B is prepared from 0.6 parts of ammonium persulfate (APS) and 35 parts of deionized water;

[0079] Add 1.6 parts of weighed NaOH to 18 parts of deionized water and stir well to obtain a NaOH aqueous solution;

[0080] In a four-necked flask equipped with a thermometer and a stirrer, 10 parts of a homemade polyether surfactant, 0.10 parts of ferrous sulfate, 8 parts of a homemade hydrophobic alkoxysilane group, and 40 parts of deionized water were added in sequence, and the temperature was raised to 95°C and maintained at a heating rate of 5-7°C / min.

[0081] Prepared solution A and solution B were respectively pumped into the reaction vessel at a constant speed using a peristaltic pump. The pumping speed of solution A was 0.45-0.54 parts / min, and the pumping speed of solution B was 0.19-0.22 parts / min. Then, the mixture was kept in a closed state and stirred at 95°C for 5 hours.

[0082] After the reaction was completed, the product was neutralized with NaOH aqueous solution, adjusted to pH 8, and cooled to 40 °C;

[0083] Finally, add 12 parts of weighed stabilizer and 117 parts of deionized water, maintain stirring at 40° C. for 1 hour, and cool to room temperature to obtain a composite surfactant with high dispersion stability.

[0084] Example 4

[0085] (1) A composite surfactant with high dispersion stability for silica ash slurry, wherein the components of the composite surfactant and their weight percentages include: 30 parts of acrylic acid, 12 parts of a homemade polyether surfactant, 8 parts of a homemade hydrophobic alkoxysilane, 1.0 parts of mercaptoacetic acid, 0.6 parts of ammonium persulfate, 0.15 parts of ferrous sulfate, 1.8 parts of NaOH, 12 parts of a stabilizer, and 275 parts of deionized water; wherein the stabilizer is a powdered mixture of xanthan gum and carboxymethyl cellulose, and the mass ratio of xanthan gum to the carboxymethyl cellulose is 1:1.

[0086] (2) The self-made polyether surfactant, each component in parts by weight, includes the following ingredients: 75 parts of polyether surfactant, 60 parts of phosphoric acid, 0.7 parts of catalyst A, and 2.5 parts of sodium carbonate reagent; the polyether surfactant is a mixture of APEG, MPEG and TPEG, and the mass ratio of APEG:MPEG:TPEG is 3.0:1.8:1; the catalyst A is a mixture of 4,4'-azobis(4-cyanovaleric acid) (ACVA) and thioglycolic acid (TA), and the mass ratio of the two is 1:1; the sodium carbonate reagent is a sodium carbonate solution with a concentration of 1.2%.

[0087] The preparation method of the self-made polyether surfactant in this example is the same as that in Example 3.

[0088] (3) The self-made hydrophobic alkoxysilane includes the following components in parts by weight: 40 parts of alkynylsilane, 38 parts of hydrogen bromide, 9 parts of tetrahydrofuran, and 0.8 parts of catalyst B; wherein catalyst B is a mixture of Pd-CaCO3 catalyst and lead acetate, and the mass ratio of Pd-CaCO3 catalyst to lead acetate is 1:0.4.

[0089] The preparation method of the homemade hydrophobic alkoxysilane in this example is the same as that in Example 3.

[0090] (4) The preparation method of the composite surfactant with high dispersion stability for silica ash slurry is as follows:

[0091] Prepare solution A and solution B: Solution A is prepared from 30 parts of acrylic acid (AA), 1.0 part of thioglycolic acid (TGA) and 50 parts of deionized water; Solution B is prepared from 0.6 parts of ammonium persulfate (APS) and 40 parts of deionized water;

[0092] Add 1.8 parts of weighed NaOH to 20 parts of deionized water and stir evenly to obtain a NaOH aqueous solution;

[0093] In a four-necked flask equipped with a thermometer, a stirrer, and a condenser, 12 parts of a homemade polyether surfactant, 0.15 parts of ferrous sulfate, 8 parts of a homemade hydrophobic alkoxysilane, and 45 parts of deionized water were added in sequence, and the temperature was raised to 95°C and maintained at a heating rate of 5-7°C / min.

[0094] Prepared solution A and solution B were respectively pumped into the reaction vessel at a constant speed using a peristaltic pump. The pumping speed of solution A was 0.45-0.54 parts / min, and the pumping speed of solution B was 0.19-0.22 parts / min. Then, the mixture was kept in a closed state and stirred at 95°C for 5 hours.

[0095] After the reaction was completed, the product was neutralized with NaOH aqueous solution, the pH value was adjusted to 8, and the product was allowed to cool to 40°C.

[0096] Finally, add 12 parts of weighed stabilizer and 120 parts of deionized water, maintain stirring at 40° C. for 1 hour, and cool to room temperature to obtain a composite surfactant with high dispersion stability.

[0097] Comparative Example 1

[0098] The dispersant selected in Comparative Example 1 is a common commercially available dispersant DP5040.

[0099] Comparative Example 2

[0100] Comparative Example 2 is basically the same as Example 3, except that the raw materials of the homemade polyether surfactant in Comparative Example 2 do not contain phosphoric acid.

[0101] Comparative Example 3

[0102] Comparative Example 3 is substantially the same as Example 3, except that the homemade polyether surfactant in Comparative Example 3 is a mixture of APEG and TPEG, and the mass ratio of APEG:TPEG is 2.5:1.

[0103] Comparative Example 4

[0104] Comparative Example 4 is substantially the same as Example 3, except that no self-prepared hydrophobic alkoxysilane is added in Comparative Example 4.

[0105] Comparative Example 5

[0106] Comparative Example 5 is substantially the same as Example 3, except that no stabilizer is added in Comparative Example 5.

[0107] Application Examples

[0108] The composite surfactant samples with high dispersion stability for silica fume slurry prepared in Examples 1 to 4 and the modified surfactant samples in Comparative Examples 1 to 5 were used for densified silica fume dispersion and neat slurry testing, respectively. The densified silica fume selected was from Lingshou County, Hebei Province. The cement in the cementitious material was Esheng PO42.5R cement. Standard sand was used in the mortar test. The water reducer used was a polycarboxylic acid high-efficiency water reducer with a water reduction rate of 25%.

[0109] Add 420 parts of deionized water to the reaction container, add 0 part or 0.03 part of modified surfactant (the blank control group does not contain dispersant, that is, 0 part of dispersant is added, referred to as No. 0), stir at 500 r / min for 5 minutes, then stop, add 280 g of densified silica fume, continue stirring, adjust the speed to 1500 r / min, continue stirring for 2 hours, and stop to obtain a silica fume slurry dispersion.

[0110] The particle size distribution of the obtained silica fume slurry dispersion was tested using a Bettersize 2600E laser particle size analyzer. The activity index of the dispersed silica fume slurry was tested in accordance with GB / T 27690-2023 "Silica fume for mortar and concrete". The stability of the silica fume dispersion was observed for 7 days and 30 days. The test results are shown in Table 1.

[0111] Table 1 Silica ash slurry dispersion test results

[0112] category D50 / μm D90 / μm 7d stability 30d stability Activity index / % No. 0 382.356 829.461 Obvious stratification Obvious stratification 107 Example 1 0.435 21.615 No obvious stratification No obvious stratification 122 Example 2 0.360 19.367 No obvious stratification No obvious stratification 126 Example 3 0.218 16.730 No obvious stratification No obvious stratification 137 Example 4 0.264 17.262 No obvious stratification No obvious stratification 133 Comparative Example 1 108.568 563.156 Slight delamination Obvious stratification 110 Comparative Example 2 35.274 178.623 No obvious stratification No obvious stratification 121 Comparative Example 3 0.306 18.274 No obvious stratification No obvious stratification 115 Comparative Example 4 51.457 224.138 No obvious stratification Obvious stratification 116 Comparative Example 5 84.4572 365.780 Obvious stratification Obvious stratification 112

[0113] From the analysis of the silica ash slurry dispersion test results in Table 1, we can see that:

[0114] (1) According to the test results of the statistical characteristic values ​​of the silica ash mortar dispersion in Table 1, the silica ash mortars of Examples 1-4 are significantly better than the blank control group, with no obvious stratification phenomenon within 30 days, and maintain good stability; this shows that the synergistic effect between the polyether group, the phosphonic acid group, the hydrophobic alkoxysilane group and the bromide ion improves the efficiency of silica ash dispersion and reduces the dispersed particle size of silica ash. On the other hand, the synergistic stabilizer increases the stabilizing effect of the silica ash mortar system, so that it can maintain no obvious stratification for 30 days; at the same time, as the dispersion performance of the silica ash mortar improves, the activity index of the silica ash mortar also increases.

[0115] (2) Comparing Example 3 with Comparative Examples 2-5, it can be seen from Table 1 that when there is no phosphate group in the modified surfactant (Comparative Example 2), the particle size of the silica ash mortar particles is larger, the dispersibility of the overall silica ash mortar is reduced, but the stability is better. This is because the phosphonic acid group has excellent dispersibility for negatively charged silica ash in an alkaline environment. The dispersibility is reduced after the modified surfactant is lacking. When there is no MPEG in the modified surfactant (Comparative Example 3), the particle size dispersibility and stability of the silica ash mortar mortar particles are better, but the activity index is low, only 115%. This is because compared with APEG and TPEG, which can be better adsorbed on silica ash, MPEG can be better adsorbed on cement, increasing the dispersibility of cement, thereby improving the hydration reaction and increasing the strength of the mortar. The activity index of the silica ash mortar mortar is reduced after the modified surfactant is lacking. When there is no self-made hydrophobic alkoxysilane in the modified surfactant (Comparative Example 4), the particle size of the silica ash mortar particles is larger, the dispersibility is reduced, and the stability is also worse. The slurry is not stratified at 7 days, but it is obviously stratified at 30 days. The dispersibility and stability of the silica ash mortar are both reduced. Because the hydrophobic alkoxysilane groups and bromide ions can significantly improve the dispersibility of silica ash mortar and improve the efficiency of hydration reaction through their own effects, the stability remains unchanged in a short period of time after their absence, but the stability of the silica ash mortar deteriorates with time; when there is no stabilizer in the modified surfactant (Comparative Example 5), the silica ash mortar is obviously stratified, and the silica ash that has been dispersed settles and aggregates together due to insufficient stability, which on the one hand causes the silica ash mortar to be stratified, and on the other hand reduces its dispersibility; xanthan gum and carboxymethyl cellulose have stronger adsorption capacity for silica ash, which makes the dispersed silica particles have a stable viscosity, and cooperates with other components to provide better rheological stability. After their absence, the stability of the silica ash mortar is significantly reduced, and the slurry is obviously stratified after 7 days.

[0116] (3) From Table 1, it can be seen that the particle size of the silica ash mortar dispersion of Example 3 is the smallest, the particle size distribution is more uniform, and the activity index is the highest compared to the blank control group without dispersant, Examples 1, 2, 4, and Comparative Examples 1-5. The silica ash mortar prepared using the composite surfactant provided by the present invention exhibits high dispersibility, high stability, and high activity, indicating that it can be widely used in concrete production processes with great economic benefits. On the other hand, it also responds to the concept of green and low-carbon development.

[0117] In summary, the composite surfactant with high dispersion stability for silica ash slurry prepared in this embodiment can efficiently disperse silica ash agglomerates, improve the activity of silica ash pozzolana while maintaining the stability of silica ash slurry, and on the other hand enhance the hydration reaction between silica ash and cement slurry, thereby reducing costs and increasing efficiency. The composite surfactant with high dispersion stability for silica ash slurry of the present invention can significantly improve the dispersibility of silica ash in cement slurry, reduce its dispersed particle size and agglomeration performance, promote the hydration activity of silica ash, and has a stabilizing effect on the already dispersed silica ash.

[0118] The composite surfactant with high dispersion stability for silica fume slurry prepared by the present invention can promote the dispersion and stability of densified silica fume, play a positive role in the recycling and reuse of industrial waste, and has a significant effect on energy conservation, emission reduction and green sustainable development in the construction industry.

[0119] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art who, within the technical scope disclosed by the present invention, makes equivalent substitutions or changes based on the technical solutions and improved concepts of the present invention shall be covered by the scope of protection of the present invention.

Claims

1. A composite surfactant with high dispersion stability for silica ash slurry, characterized in that: The components of the composite surfactant and their weight fractions include: 28-30 parts of acrylic acid, 10-12 parts of a homemade polyether surfactant, 6-8 parts of a homemade hydrophobic alkoxysilane, 0.5-1.0 parts of mercaptoacetic acid, 0.3-0.7 parts of ammonium persulfate, 0.05-0.15 parts of ferrous sulfate, 1-2 parts of NaOH, 8-12 parts of a stabilizer, and 215-275 parts of deionized water; The self-made polyether surfactant comprises the following raw materials, calculated by weight: 55-75 parts of polyether surfactant, 45-60 parts of phosphoric acid, 0.3-0.7 parts of catalyst A, and 1-3 parts of sodium carbonate reagent; The self-made hydrophobic alkoxysilane comprises the following raw materials by mass: 30-40 parts of alkynylsilane, 30-40 parts of hydrogen bromide, 5-10 parts of tetrahydrofuran, and 0.3-0.8 parts of catalyst B; The alkynylsilane is propargyl 3-(triethoxysilylpropyl)carbamate.

2. The method for preparing a composite surfactant with high dispersion stability for silica ash slurry according to claim 1, characterized in that: The steps include: (1) Preparation of solution A and solution B: Solution A is prepared from 28-30 parts of acrylic acid, 0.5-1.0 parts of mercaptoacetic acid and 40-50 parts of deionized water; Solution B is prepared from 0.3-0.7 parts of ammonium persulfate and 30-40 parts of deionized water; (2) Add 1-2 parts of NaOH to 15-20 parts of deionized water and stir evenly to obtain a NaOH aqueous solution; (3) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser, 10-12 parts of a homemade polyether surfactant, 0.05-0.15 parts of ferrous sulfate, 6-8 parts of a homemade hydrophobic alkoxysilane, and 35-45 parts of deionized water were added in sequence, and the temperature was raised to 85-95°C and maintained at a heating rate of 5-7°C / min; (4) The prepared solution A and solution B were respectively pumped into the reaction vessel at a constant speed using a peristaltic pump. The pumping speed of solution A was 0.45-0.54 parts / min, and the pumping speed of solution B was 0.19-0.22 parts / min. The mixture was then kept in a closed state and stirred at 85-95°C for 4.5-5.5 hours. (5) After the reaction is completed, the product is neutralized with the NaOH aqueous solution, the pH value is adjusted to 7±1, and then allowed to stand and cool to 30~40°C and maintained; (6) Add 8-12 parts of stabilizer and 95-120 parts of deionized water, keep stirring at 30-40°C for 0.5-1 hour, and then cool to room temperature to obtain the composite surfactant with high dispersion stability for silica ash slurry.

3. The composite surfactant with high dispersion stability for silica ash slurry according to claim 1, characterized in that: The polyether surfactant is a mixture of allyl alcohol polyoxyethylene ether, methoxy polyethylene glycol and isoprene polyoxyethylene ether; wherein the mass ratio of allyl alcohol polyoxyethylene ether, methoxy polyethylene glycol and isoprene polyoxyethylene ether is (1.8-3.0): (0.7-1.8):

1.

4. The composite surfactant with high dispersion stability for silica ash slurry according to claim 1, characterized in that: The catalyst A is a mixture of 4,4'-azobis(4-cyanovaleric acid) and mercaptoacetic acid, with a mass ratio of 1:1; the sodium carbonate reagent is a sodium carbonate solution with a concentration of 1.2%.

5. The composite surfactant with high dispersion stability for silica ash slurry according to claim 1, characterized in that: The preparation steps of the homemade polyether surfactant are as follows: (1) Add 55-75 parts of a polyether surfactant to a three-necked flask equipped with a thermometer and a stirrer, heat to 65-70°C at a heating rate of 5-7°C / min, and maintain for 30-45 minutes; (2) Add 0.3-0.7 parts of catalyst A, keep the temperature at 65-70°C and continue stirring for 20-30 minutes; then heat to 90-140°C at a heating rate of 5-7°C / min, and use a peristaltic pump to deliver 45-60 parts of phosphoric acid into the three-necked flask at a constant speed of 1.4-1.6 parts / min. After completion, seal the three-necked flask and keep it warm for 3-5 hours; (3) Then, when the temperature is allowed to drop to 35-45°C, 1-3 parts of sodium carbonate reagent are added dropwise to the three-necked flask to control the pH value of the system between 7 and 8, thereby obtaining the self-made polyether surfactant.

6. The composite surfactant with high dispersion stability for silica ash slurry according to claim 1, characterized in that: The catalyst B is a mixture of Pd-CaCO3 catalyst and lead acetate, wherein the mass ratio of the Pd-CaCO3 catalyst to the lead acetate is 1:0.

4.

7. The composite surfactant with high dispersion stability for silica ash slurry according to claim 6, characterized in that: The preparation steps of the homemade hydrophobic alkoxysilane are as follows: 30-40 parts of alkynylsilane, 5-10 parts of tetrahydrofuran and 0.3-0.8 parts of catalyst B are added to a reaction vessel in sequence, and then 30-40 parts of hydrogen bromide gas are introduced and the reaction vessel is sealed. Thereafter, the temperature is raised to 150-160° C. at a constant rate of 5-7° C. / min, and the pressure is raised to 5-8 atmospheres at a constant rate of 0.4-0.5 MPa / h. The constant temperature and pressure are maintained for 5-6 hours, and the mixture is cooled to room temperature to obtain the self-prepared hydrophobic alkoxysilane.

8. The composite surfactant with high dispersion stability for silica ash slurry according to claim 1, characterized in that: The stabilizer is a powdered mixture of xanthan gum and carboxymethyl cellulose, wherein the mass ratio of the xanthan gum to the carboxymethyl cellulose is 1:1.

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