Preparation method of internal doping type water repellent for cement-based material and water repellent

Abstract

The invention relates to the field of building waterproof materials, in particular to a preparation method of an internal doping type water repellent for a cement-based material and the water repellent. Comprising the following steps: a) preparing the following raw materials in parts by weight: 30-40 parts of stearic acid, 3-5 parts of a compound emulsifier, 0.3-0.5 part of a defoaming agent, 0.1-0.3 part of a bactericide and 59-70 parts of deionized water; the compound emulsifier comprises a water-soluble emulsifier and an oil-soluble emulsifier; b) heating, stirring and melting stearic acid, adding an oil-soluble emulsifier, and uniformly stirring and mixing to obtain an oil phase; c) heating deionized water to 75-80 DEG C, adding a water-soluble emulsifier, and uniformly stirring and mixing to obtain a water phase; d) slowly adding the water phase into the oil phase, mixing, keeping the rotating speed at 50-200rpm, after the water phase is completely added and uniformly mixed, increasing the rotating speed to 300-800rpm, stirring, and keeping the temperature for 0.5-1.5 hours to obtain an emulsion; and e) dispersing and cooling the emulsion, respectively dropwise adding a defoaming agent and a sterilizing agent, continuously dispersing for 1.5-2.5 hours, and filtering to obtain the water repellent. The stearic acid water repellent provided by the invention has relatively low influence on the mechanical strength of mortar (concrete), and solves the problem of relatively large strength loss caused by air entraining of a traditional stearic acid water repellent in actual engineering application.

Description

Technical Field

[0001] The present application relates to the field of building waterproof materials, and in particular to a preparation method of an internally mixed water repellent agent for cement-based materials and the water repellent agent. Background Art

[0002] Water penetration often leads to erosion inside concrete, so by reducing the permeability of concrete, its corrosion resistance can be improved, thereby achieving the effect of improving the durability of concrete and extending the service life of concrete. Hydrophobic modification is one of the most commonly used methods to reduce the permeability of concrete. At present, the hydrophobic modification of cement concrete mainly includes surface hydrophobic modification and overall hydrophobic modification methods. The surface hydrophobic modification method is to treat the surface of concrete by impregnation or coating. In this method, the hydrophobic modification layer only exists on the surface of concrete. When cracks or wear appear on the concrete surface during long-term use, the exposed new concrete surface is still hydrophilic, resulting in a rapid decrease in the impermeability of concrete. Silicone hydrophobic agents have low surface tension and good oxidation resistance, and are one of the main materials for hydrophobic treatment of building materials. CN101580355B discloses a water-based silicone waterproofing agent with sodium methylsiliconate as the main raw material, which is suitable for waterproofing the permeability of porous structures on the surface of buildings. However, methylsiliconate is too alkaline, and as a cement concrete waterproofing agent it has disadvantages such as rapid setting and poor durability, and is prone to yellowing of the wall after construction. In addition, considering the high cost of silicone water repellents, it is difficult to be widely used in construction projects.

[0003] The overall hydrophobic modification method uses hydrophobic admixtures for fresh concrete during the mixing process. This type of concrete exhibits overall hydrophobicity. The newly exposed concrete surface is still hydrophobic during use. Even if the surface is worn and cracks appear, its impermeability will not be affected. Compared with the surface hydrophobic modification method, the overall hydrophobic modification method has better durability. The overall hydrophobic additives mainly include silane, silicone, hydrophobic powder, waste rubber powder and other materials. Hydrophobic powder is difficult to disperse evenly in water, and the introduction of hydrophobic waste tire rubber powder greatly reduces the strength of concrete.

[0004] Stearic acid and its metal derivatives (calcium stearate and zinc stearate) are common raw materials of water repellent. Stearic acid is solid at room temperature and insoluble in water. It is difficult to be evenly dispersed in concrete when directly added during the stirring process. At the same time, its derivatives are difficult to be evenly dispersed in water because of their high hydrophobicity. In the process of mixing concrete, it needs to be mixed with cement before use, and the stirring time needs to be extended to achieve the purpose of even dispersion, which greatly reduces the construction efficiency. CN101195526A discloses a preparation method of cement water repellent with stearic acid as the main raw material, wherein calcium hydroxide is added dropwise to react with stearic acid to generate calcium stearate, and after colloid grinding and high-pressure homogenization, a cement water repellent evenly dispersed in concrete is obtained. However, the preparation steps of the water repellent are complicated, and the mechanical strength of the concrete is greatly affected at the same time. This is because stearic acid, as one of the raw materials of air entraining agent, is added to concrete in different dosages as the main component of water repellent, and the air entraining effect is obvious, and the mechanical strength of the concrete is also damaged to a certain extent, and it is even difficult to meet the construction strength requirement. Therefore, there is an urgent need to develop a water repellent so that cement mortar (concrete) has a strong water repellent effect while ensuring mechanical strength. Summary of the invention

[0005] In order to make mortar (concrete) have both water repellency and excellent strength, the present application provides a preparation method of an internally mixed water repellent for cement-based materials and the water repellent.

[0006] On the one hand, the present application provides a method for preparing an internally mixed water repellent for cement-based materials, comprising the following steps: a) preparing raw materials according to a proportion, the raw materials comprising: 30-40 parts of stearic acid, 3-5 parts of a composite emulsifier, 0.3-0.5 parts of a defoamer, 0.1-0.3 parts of a bactericide, and 59-70 parts of deionized water; the composite emulsifier comprises a water-soluble emulsifier and an oil-soluble emulsifier; b) heating and stirring the stearic acid to melt, adding the oil-soluble emulsifier, stirring and mixing to obtain a uniform mixture; c) heating deionized water to 75-80°C, adding a water-soluble emulsifier, and stirring to mix uniformly to obtain an aqueous phase; d) slowly adding the aqueous phase to the oil phase and mixing, maintaining a rotation speed of 50-200 rpm, after the aqueous phase is added and mixed uniformly, increasing the rotation speed to 300-800 rpm for stirring, and keeping warm for 0.5-1.5 hours to obtain an emulsion; e) after the emulsion is dispersed and cooled, a defoamer and a bactericide are added dropwise respectively, and the dispersion is continued for 1.5-2.5 hours, and the hydrophobic agent is obtained by filtering.

[0007] The present application prepares an emulsion suspension water repellent by phase inversion emulsification. The phase inversion emulsification process is used to emulsify stearic acid, and a high-quality emulsion is prepared under a lower shear force, which reduces energy consumption and equipment wear and improves preparation efficiency. The oil-water ratio changes during the phase change process, so that the emulsion particle size can be more uniform, thereby obtaining a stable and delicate emulsion. In addition, during the emulsification process, the transformation of the oil phase and the water phase greatly improves the stability of the emulsion. The emulsion itself has a strong ability to resist stratification and coagulation, and is not prone to oil-water separation; there is no need to add pH regulators such as calcium hydroxide to adjust the pH value of the emulsion, and the emulsion system itself is stable. The use of water-soluble and oil-soluble emulsifiers to composite emulsify stearic acid has a better emulsification effect on stearic acid, and the content of effective ingredients in the emulsion is increased, which further improves the water repellent effect of the water repellent in concrete. The addition of bactericides prevents the growth of microorganisms, prolongs the shelf life of the product, and also helps to maintain the overall stability of the emulsion system and avoid problems such as stratification, coagulation or phase separation of the emulsion. Defoamers can provide a longer-term anti-foaming effect and improve mechanical strength.

[0008] The stearic acid-based water repellent in the present application has a low influence on the mechanical strength of mortar (concrete), thus solving the problem of large strength loss caused by air entrainment of traditional stearic acid-based water repellent in actual engineering applications.

[0009] Preferably, in step d), the water phase is slowly added to the oil phase for mixing, and the rotation speed is maintained at 120 rpm. After the water is added and mixed evenly, the rotation speed is increased to 500 rpm for stirring.

[0010] Preferably, the mass ratio of the water-soluble emulsifier to the oil-soluble emulsifier is 1:1.

[0011] Preferably, the water-soluble emulsifier is selected from one or more of fatty alcohol ether phosphate potassium salt MOA-3PK-70, fatty alcohol ether phosphate potassium salt MOA-3PK-40, Tween 40, and Tween 60.

[0012] Preferably, the oil-soluble emulsifier is selected from one or more of sorbitan monostearate Span 60, sorbitan monooleate Span 80, and sorbitan monopalmitate Span 40.

[0013] More preferably, the water-soluble emulsifier is Tween 60, polyoxyethylene (20) sorbitan monostearate; and the oil-soluble emulsifier is sorbitan monostearate Span 60.

[0014] The inventor screened water-soluble emulsifiers and oil-soluble emulsifiers when seeking to prepare a hydrophobic agent by phase inversion emulsification. Through experiments, it was unexpectedly found that when the water-soluble emulsifier is Tween 60; when the oil-soluble emulsifier is sorbitan monostearate Span 60, the prepared hydrophobic agent can obtain better stability and better strength, and the hydrophobic effect is the best. This may be because, compared with the potassium salt of fatty alcohol ether phosphate (MOA-3PK-40), the selected Tween 60 has a branched water-soluble long chain structure grafted with an aliphatic ring, while the sorbitan monostearate Span 60 has a linear hydrophobic long chain of an aliphatic ring. Both have an aliphatic ring, and the combination of the branched long chain and the linear long chain can form a more complex amphiphilic cross network in the system, thereby achieving a better emulsification effect on stearic acid. The steric hindrance based on the emulsifier structure also further improves the dispersion of stearic acid, and the prepared hydrophobic agent has better hydrophobicity, a more stable emulsion, and a high effective ingredient.

[0015] Preferably, the defoamer is a modified amino silicone oil defoamer, and its preparation steps include: stirring and uniformly mixing amino-terminated polysiloxane and deionized water to obtain a mixed solution; adding a silane coupling agent to the mixed solution to react at 70°C to 100°C for 2 to 4 hours, and then adding polyvinyl alcohol to mix to obtain a modified amino silicone oil defoamer.

[0016] Preferably, the silane coupling agent is selected from one or more of 3-methacryloxypropyltriethoxysilane and methacryloxypropylmethyldiethoxysilane.

[0017] More preferably, the silane coupling agent is 3-methacryloxypropyltriethoxysilane.

[0018] This application is specifically for synthesizing silane-modified amino silicone oil defoamers for stearic acid hydrophobic agents. It performs better under high temperature and acid-base environments, and can provide a long-term anti-foaming effect to stearic acid emulsions. While dispersing stearic acid particles, it can better maintain the stability of the hydrophobic state. The silane group of the defoamer has a certain hydrophobicity. After adding cement mortar (concrete), it reduces the internal voids of the structure, improves the mechanical strength of concrete, and improves the hydrophobicity of the mortar (concrete) to a certain extent. Experiments show that when the silane coupling agent is 3-methacryloxypropyl triethoxysilane, compared with methacryloxypropyl methyl diethoxysilane, the prepared defoamer is used for a hydrophobic agent, and the cement mortar (concrete) has better strength and hydrophobicity. This may be because the defoamer modified by 3-methacryloxypropyl triethoxysilane can better enter the internal pores of the cement mortar (concrete) structure to improve strength and hydrophobicity, and can play an anchoring role to improve the crack resistance of cement mortar (concrete).

[0019] Preferably, the fungicide is selected from one or more of Clariant fungicide Nipacide CI15 HS, SINOC fungicide BIT 10, 050 monosalt fungicide, phenoxyethanol, para-chloro-meta-xylenol, and ethylhexylglycerin.

[0020] The addition of the bactericide in the present application prevents the growth of microorganisms, prolongs the shelf life of the product, and also helps to maintain the overall stability of the emulsion system and avoid problems such as stratification, coagulation or phase separation of the emulsion.

[0021] On the other hand, the present application provides an internally-added water-repellent agent prepared by the above-mentioned preparation method.

[0022] In summary, this application has the following beneficial technical effects: 1. This application uses a phase inversion emulsification process to emulsify stearic acid, and prepares a high-quality emulsion under a lower shear force, which reduces energy consumption and equipment wear and improves preparation efficiency. The oil-water ratio changes during the phase change process, and the emulsion particle size can be more uniform, thereby obtaining a stable and delicate emulsion. During the emulsification process, the transition of the oil phase and the water phase greatly improves the stability of the emulsion. The emulsion itself has a strong ability to resist stratification and coagulation, and is not prone to oil-water separation.

[0023] 2. The application selects a specific composite emulsifier, which has better emulsification effect, increases the content of effective ingredients in the emulsion, and further improves the hydrophobic effect of the water repellent in concrete. Tween 60 has a branched water-soluble long chain structure grafted with aliphatic rings, while Span 60, a linear hydrophobic long chain of sorbitan monostearate, can form a more complex amphiphilic cross network in the system, thereby achieving better emulsification of stearic acid. The steric hindrance based on the emulsifier structure also further improves the dispersion of stearic acid.

[0024] 3. This application is specifically for synthesizing silane-modified amino silicone oil defoamers for stearic acid hydrophobic agents. It performs better under high temperature and acid-base environments, and can provide a long-term anti-foaming effect for stearic acid emulsions. While dispersing stearic acid particles, it can also maintain the stability of the hydrophobic agent state. The silane group of the defoamer has a certain hydrophobicity. After adding cement mortar (concrete), it reduces the internal voids of the structure, improves the mechanical strength of concrete, and improves the hydrophobicity of the mortar (concrete) to a certain extent. At the same time, the selection of 3-methacryloxypropyl triethoxysilane modified defoamers can better enter the internal pores of the cement mortar (concrete) structure to improve strength and hydrophobicity, and can play an anchoring role to improve the crack resistance of cement mortar (concrete).

[0025] 4. The stearic acid-based water repellent of the present application has a low impact on the mechanical strength of mortar (concrete), solving the problem of large strength loss caused by air entrainment of traditional stearic acid-based water repellents in actual engineering applications. DETAILED DESCRIPTION

[0026] The present application is further described in detail below through examples.

[0027] The relative molecular weight of stearic acid is 284.48, the acid value is 205.0-210.0 mg KOH / g, the crystallization point is 54.0-57°C, and the ignition residue (calculated as sulfate) is ≤0.3ω / %; PDMS are all amino-terminated polydimethylsiloxane purchased from Hubei Xinyuhong Biology, with a molecular weight of 1000; polyvinyl alcohol is purchased from Zhongyan (Shandong) New Materials, polyvinyl alcohol 99; the polyether defoamer is XPJ800, and other raw materials in this application are all commercially available. Example

[0028] Example 1 Weigh 60g of stearic acid in a reactor, heat and stir, and after it is completely melted, add 3g of Span 80, stir and mix evenly to obtain the oil phase for use. Heat 120g of deionized water to the emulsification temperature of 78°C, and add 3g of Tween 60, stir and mix evenly to obtain the water phase for use. Slowly add the water phase to the reactor and mix with the oil phase, maintaining the speed of 120rpm. After the water is added and mixed evenly, increase the stirring speed and maintain stirring at 500rpm. After keeping warm and stirring for 1 hour, disperse and cool the emulsion through a high-speed disperser, then add 0.8g of defoaming agent and 0.3g of para-chloro-metaxylenol respectively, continue to disperse for 2 hours and filter to obtain the hydrophobic agent; The preparation steps of the defoamer are as follows: 100g PDMS and 50g deionized water are poured into a reaction kettle and stirred until uniformly mixed. 3-methacryloxypropyl triethoxysilane, a silane coupling agent, is added to the reaction system according to 5% of the mass of PDMS and stirred, and the temperature is adjusted to 100°C. The reaction time is 3 hours, and finally 5g of polyvinyl alcohol is added and stirred until uniform to prepare a defoamer.

[0029] Example 2 Weigh 60g of stearic acid into a reactor, heat and stir, and after it is completely melted, add 3g of Span 60, stir and mix evenly to obtain the oil phase for use. Heat 120g of deionized water to the emulsification temperature of 78°C, and add 3g of Tween 60, stir and mix evenly to obtain the water phase for use. Slowly add the water phase to the reactor and mix with the oil phase, maintaining the speed at 120rpm. After the water is added and mixed evenly, increase the stirring speed and maintain stirring at 500rpm. After keeping warm and stirring for 1 hour, disperse and cool the emulsion through a high-speed disperser, then add 0.8g of defoaming agent and 0.3g of para-chloro-metaxylenol respectively, continue to disperse for 2 hours and filter to obtain the hydrophobic agent; The preparation steps of the defoamer are as follows: 100g PDMS and 50g deionized water are poured into a reaction kettle and stirred until uniformly mixed. 3-methacryloxypropyl triethoxysilane, a silane coupling agent, is added to the reaction system according to 5% of the mass of PDMS and stirred, and the temperature is adjusted to 100°C. The reaction time is 3 hours, and finally 5g of polyvinyl alcohol is added and stirred until uniform to prepare a defoamer.

[0030] Example 3 Weigh 60g of stearic acid in a reactor, heat and stir, and after it is completely melted, add 3g of Span 60, stir and mix evenly to obtain the oil phase for use. Heat 120g of deionized water to an emulsification temperature of 78°C, and add 3g of MOA-3PK-40, stir and mix evenly to obtain the water phase for use. Slowly add the water phase to the reactor and mix with the oil phase, keep the speed at 120rpm, and after the water is added and mixed evenly, increase the stirring speed and keep stirring at 500rpm. After keeping warm and stirring for 1 hour, disperse the emulsion through a high-speed disperser, cool it, and then drop 0.8g of defoamer and 0.3g of parachlorometaxylenol respectively. Continue to disperse for 2 hours and filter to obtain a hydrophobic agent.

[0031] The preparation steps of the defoamer are as follows: 100g PDMS and 50g deionized water are poured into a reaction kettle and stirred until uniformly mixed. 3-methacryloxypropyl triethoxysilane, a silane coupling agent, is added to the reaction system according to 5% of the mass of PDMS and stirred, and the temperature is adjusted to 100°C. The reaction time is 3 hours, and finally 5g of polyvinyl alcohol is added and stirred until uniform to prepare a defoamer.

[0032] Example 4 Weigh 60g of stearic acid in a reactor, heat and stir, and after it is completely melted, add 3g of Span 80, stir and mix evenly to obtain the oil phase for use. Heat 120g of deionized water to the emulsification temperature of 78°C, and add 3g of Tween 60, stir and mix evenly to obtain the water phase for use. Slowly add the water phase to the reactor and mix with the oil phase, keep the speed at 120rpm, and after the water is added and mixed evenly, increase the stirring speed and keep stirring at 500rpm. After keeping warm and stirring for 1 hour, disperse and cool the emulsion through a high-speed disperser, add 0.8g of defoamer and 0.3g of parachloro-meta-xylenol respectively, continue to disperse for 2 hours, and then filter to obtain the water repellent.

[0033] The preparation steps of the defoamer are as follows: 100g PDMS and 50g deionized water are poured into a reaction kettle and stirred until uniformly mixed. 5% of the mass of PDMS silane coupling agent methacryloxypropylmethyldiethoxysilane is added to the reaction system and stirred, and the temperature is adjusted to 100°C. The reaction time is 3 hours, and finally 5g of polyvinyl alcohol is added and stirred until uniform to prepare a defoamer.

[0034] Example 5 Weigh 60g of stearic acid in a reactor, stir while heating, and after it is completely melted, add 3g of Span 80, stir and mix evenly to obtain the oil phase for use. Heat 120g of deionized water to an emulsification temperature of 78°C, and add 3g of Tween 60, stir and mix evenly to obtain the water phase for use. Slowly add the water phase to the reactor and mix with the oil phase, keep the speed at 120rpm, and after the water is added and mixed evenly, increase the stirring speed and keep stirring at 500rpm. After keeping warm and stirring for 1 hour, disperse and cool the emulsion through a high-speed disperser, add 0.8g of defoamer and 0.3g of parachlorometa-xylenol respectively, continue to disperse for 2 hours, and filter to obtain a hydrophobic agent. Among them, the defoamer PDMS is not silane-modified.

[0035] Example 6 Weigh 60g of stearic acid in a reactor, stir while heating, and after it is completely melted, add 3g of Span 80, stir and mix evenly to obtain the oil phase for use. Heat 120g of deionized water to an emulsification temperature of 78°C, add 3g of Tween 60, stir and mix evenly to obtain the water phase for use. Slowly add the water phase to the reactor and mix with the oil phase, keep the speed at 120rpm, and after the water is added and mixed evenly, increase the stirring speed and keep stirring at 500rpm. After keeping warm and stirring for 1 hour, disperse and cool the emulsion through a high-speed disperser, add 0.8g of defoamer and 0.3g of parachlorometa-xylenol respectively, continue to disperse for 2 hours, and then filter to obtain a hydrophobic agent. Among them, the defoamer is a polyether defoamer.

[0036] Comparative Example 1 Weigh 60g of stearic acid in a reactor, heat and stir, and after it is completely melted, add 3g of Span 80, stir and mix evenly to obtain the oil phase for use. Heat 120g of deionized water to the emulsification temperature of 78°C, and add 3g of Tween 60, stir and mix evenly to obtain the water phase for use. Slowly add the water phase to the reactor and mix with the oil phase, keep the speed at 120rpm, and after the water is added and mixed evenly, increase the stirring speed and keep stirring at 500rpm. After keeping warm and stirring for 1 hour, disperse the emulsion through a high-speed disperser, cool it, and then drop 0.3g of para-chloro-meta-xylenol, continue to disperse for 2 hours, and then filter to obtain the water repellent.

[0037] Comparative Example 2 60g of stearic acid, 120g of deionized water, 3g of Span 80 and 3g of Tween 60 were placed in a reactor, heated to 78°C, and stirred at 500rpm. After stirring for 1 hour, the emulsion was dispersed and cooled by a high-speed disperser, and 0.8g of defoamer and 0.3g of parachloro-meta-xylenol were added dropwise, and the dispersion was continued for 2 hours, and then filtered to obtain a hydrophobic agent; The preparation steps of the defoamer are as follows: 100g PDMS and 50g deionized water are poured into a reaction kettle and stirred until uniformly mixed. 3-methacryloxypropyl triethoxysilane, a silane coupling agent, is added to the reaction system according to 5% of the mass of PDMS and stirred, and the temperature is adjusted to 100°C. The reaction time is 3 hours, and finally 5g of polyvinyl alcohol is added and stirred until uniform to prepare a defoamer.

[0038] Performance testing: The performance test results of the embodiments and comparative examples are shown in Table 1, wherein the viscosity, 28d compressive strength ratio, water permeability pressure ratio, and water absorption ratio are tested according to the test method in JC 474-2008 (Mortar and Concrete Waterproofing Agent), and the water repellent dosage is 1% of the cement mass.

[0039] Table 1 Performance test table Note: The specification requirements for first-class products in JC 474-2008 (Mortar and Concrete Waterproofing Agent) are water permeability pressure ratio ≥ 300%, 28d compressive strength ratio ≥ 90%, and water absorption ratio (48h) ≤ 65%.

[0040] From the data in Table 1, it can be found that after the present application is added to the mortar, the water absorption ratio and water permeability pressure ratio reflect the excellent water repellency of the mortar (concrete). At the same time, the data reflect that the strength loss of the mortar (concrete) after adding the water repellent is small, meeting the standard requirements of JC 474-2008 (Mortar, Concrete Waterproofing Agent) for first-class products. Through Example 1, Example 6 and Comparative Example 1, the silane-modified polysiloxane defoamer has better comprehensive performance than the polyether defoamer and the stearic acid water repellent after adding the mortar. The addition of the silane defoamer also improves the water repellency of the mortar to a certain extent, while the stearic acid water repellent in Comparative Example 1 without the defoamer has a paste-like appearance, and the performance of the mortar (concrete) cannot meet the requirements of the standard qualified products. From Example 1 and Examples 4-5, it can be seen that the present application improves the water repellency and strength by modifying the polysiloxane defoamer with 3-methacryloxypropyl triethoxysilane. It can be seen from Example 1 and Comparative Example 2 that the present application emulsifies stearic acid through a phase inversion emulsification process, the emulsion has good stability, has a strong ability to resist stratification and coagulation, is not prone to oil-water separation, and has improved hydrophobicity. After being added to mortar (concrete) as a cement mortar hydrophobic agent, it does not have a significant impact on the mechanical strength of the mortar (concrete), while achieving a better hydrophobic effect.

[0041] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for preparing an internally mixed water repellent for cement-based materials, characterized in that: The method comprises the following steps: a) preparing raw materials according to a proportion, wherein the raw materials comprise: 30-40 parts of stearic acid, 3-5 parts of a composite emulsifier, 0.3-0.5 parts of a defoamer, 0.1-0.3 parts of a bactericide, and 59-70 parts of deionized water; the composite emulsifier comprises a water-soluble emulsifier and an oil-soluble emulsifier; b) heating and stirring the stearic acid to melt it, and then adding the oil-soluble emulsifier to stir and mix uniformly to obtain an oil phase; c) heating the deionized water to 75-80°C, adding the water-soluble emulsifier, and stirring and mixing uniformly to obtain a water phase; d) slowly adding the water phase to the oil phase and mixing, maintaining a rotation speed of 50-200 rpm, and after the water phase is added and mixed uniformly, accelerating the rotation speed to 300-800 rpm for stirring, and keeping the temperature for 0.5-1.5 hours to obtain an emulsion; e) after the emulsion is dispersed and cooled, the defoamer and the bactericide are respectively added dropwise, and the dispersion is continued for 1.5-2.5 hours, and the water-repellent is obtained by filtering.

2. The method for preparing the internally mixed water repellent agent for cement-based materials according to claim 1, characterized in that: The mass ratio of the water-soluble emulsifier to the oil-soluble emulsifier is 1:

1.

3. The method for preparing the internally mixed water repellent agent for cement-based materials according to claim 1, characterized in that: The water-soluble emulsifier is selected from one or more of fatty alcohol ether phosphate potassium salt MOA-3PK-70, fatty alcohol ether phosphate potassium salt MOA-3PK-40, Tween 40, and Tween 60.

4. The method for preparing the internally mixed water repellent agent for cement-based materials according to claim 3, characterized in that: The oil-soluble emulsifier is selected from one or more of sorbitan monostearate Span 60, sorbitan monooleate Span 80, and sorbitan monopalmitate Span 40.

5. The method for preparing the internally mixed water repellent agent for cement-based materials according to claim 4, characterized in that: The water-soluble emulsifier is Tween 60; the oil-soluble emulsifier is Span 60, a monostearate of sorbitan.

6. The method for preparing the internally mixed water repellent agent for cement-based materials according to claim 1, characterized in that: The defoamer is a modified amino silicone oil defoamer, and its preparation steps include: stirring amino-terminated polysiloxane and deionized water to uniformly mix to obtain a mixed solution; adding a silane coupling agent to the mixed solution to react at 70°C to 100°C for 2 to 4 hours, and then adding polyvinyl alcohol to mix to obtain the modified amino silicone oil defoamer.

7. The method for preparing the internally mixed water repellent agent for cement-based materials according to claim 6, characterized in that: The silane coupling agent is selected from one or more of 3-methacryloxypropyltriethoxysilane and methacryloxypropylmethyldiethoxysilane.

8. The method for preparing the internally mixed water repellent agent for cement-based materials according to claim 7, characterized in that: The silane coupling agent is 3-methacryloxypropyltriethoxysilane.

9. The method for preparing the internally mixed water repellent agent for cement-based materials according to claim 1, characterized in that: The bactericide is selected from one or more of Clariant bactericide Nipacide CI15 HS, Sinnoco bactericide BIT 10, 050 monosalt bactericide, phenoxyethanol, para-chloro-meta-xylenol, and ethylhexylglycerin.

10. An internally mixed water repellent, characterized in that: Prepared by the preparation method described in any one of claims 1 to 9.

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