Two-component epoxy-based interface treatment agent for repairing damaged wall and preparation method thereof

Abstract

The present application relates to the technical field of paint, in particular to a two-component epoxy-based interface treatment agent for repairing damaged wall and a preparation method thereof. The two-component epoxy-based interface treatment agent for repairing damaged wall is composed of component A and component B in a weight ratio of 25-35:1. The component A comprises the following raw materials in parts by weight: 20-40 parts of hyperbranched polyurethane modified epoxy resin, 30-50 parts of white sand, 5-10 parts of nano-cellulose modified epoxy resin, 0.2-0.5 parts of wetting agent, 0.1-0.3 parts of silane coupling agent, and 20-30 parts of deionized water. The component B comprises the following raw materials in parts by weight: 85-95 parts of polyamide curing agent and 5-15 parts of deionized water. The two-component epoxy-based interface treatment agent for repairing damaged wall has excellent tensile bonding strength, toughness, and excellent permeability, and has excellent adhesion on the surface of different substrates, and can be used for repairing damaged walls with different textures.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a two-component epoxy-based interface treatment agent for repairing damaged walls and its preparation method. Background Technology

[0002] Currently, my country is experiencing a period of rapid development, and the construction industry has also seen explosive growth, with various types of buildings springing up everywhere. However, some older buildings are frequently experiencing cracks, leaks, and peeling. These issues range from minor aesthetic concerns to serious property damage and even endangering lives. During this period of rapid urbanization, the renovation of old residential areas is underway, creating a significant demand for wall repair and renovation. To ensure that repaired walls look brand new, in addition to improved construction management, the performance and adaptability of repair materials must also be enhanced to accommodate wall repairs in multi-substrate systems. The types of substrates exposed due to wall peeling are diverse, including building concrete, aerated concrete, cement mortar, as well as tiles, building blocks, and color steel plates, etc. Construction materials must comply with the standards of GB / T25181-2019 "Premixed Mortar" or JC / T907-2018 "Concrete Interface Treatment Agent". The former improves the surface adhesion between the mortar layer and concrete, and aerated concrete, while the latter improves the surface adhesion between the mortar layer and wall materials such as building blocks or bricks. In other words, different types of surface treatment agents are used for different wall textures. This can easily lead to errors in agent selection, creating new hidden dangers in the project. Furthermore, since multiple wall textures often coexist in the same area during wall repair and renovation, this is also one of the reasons for wall surface peeling. Therefore, it is essential to provide a treatment agent applicable to the repair of damaged walls of different textures. Summary of the Invention

[0003] The purpose of this invention is to provide a two-component epoxy-based interface treatment agent for repairing damaged walls and its preparation method. It can adhere firmly to the surface of both concrete and ceramic tile substrates and is applicable to the repair of damaged walls of different textures.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] The purpose of this invention is to provide a two-component epoxy interface treatment agent for repairing damaged walls, which is composed of component A and component B in a weight ratio of 25-35:1;

[0006] Component A comprises the following raw materials in parts by weight: 20-40 parts hyperbranched polyurethane modified epoxy resin, 30-50 parts white sand, 5-10 parts nanocellulose modified epoxy resin, 0.2-0.5 parts wetting agent, 0.1-0.3 parts silane coupling agent, and 20-30 parts deionized water.

[0007] Component B comprises the following raw materials in parts by weight: 85-95 parts polyamide curing agent, 5-15 parts deionized water;

[0008] The preparation method of the hyperbranched polyurethane modified epoxy resin is as follows: a polyether polyol and toluene diisocyanate after dehydration are added to a reaction vessel to obtain a polyurethane prepolymer; a hydroxyl-terminated hyperbranched polyester is added to the polyurethane prepolymer to modify it into a hyperbranched polyurethane; and bisphenol A type glycidyl ether epoxy resin is added to it and stirred to obtain a hyperbranched polyurethane modified epoxy resin.

[0009] The preparation method of nanocellulose modified epoxy resin is as follows: first, nanocellulose is surface-treated with a silane coupling agent, and then the treated nanocellulose is added to a long-chain polypropylene glycol diglycidyl ether type epoxy resin to obtain nanocellulose modified epoxy resin.

[0010] As mentioned in the background section, a penetrating and reinforcing agent capable of meeting the needs of various matrix materials is required when repairing and renovating walls. To address this requirement, this application provides a two-component waterborne epoxy interface treatment agent, innovatively incorporating a large proportion of white sand. This provides a rough surface with a larger specific surface area after adhesion, resulting in stronger mechanical adhesion between the rough surface and subsequent construction materials, leading to good bonding. The interface treatment agent of this invention uses a combination of hyperbranched polyurethane-modified epoxy resin and nanocellulose-modified epoxy resin as the bonding resin. Both have undergone modification treatment. The hydroxyl-terminated hyperbranched polyester-modified polyurethane prepolymer has a highly branched structure and a high molecular weight. The abundant terminal hydroxyl functional groups can be well dispersed in the aqueous system, improving the elasticity and toughness of the resin matrix and significantly enhancing its tensile bond strength and 7-day penetration depth under freeze-thaw cycles. The nanocellulose-modified epoxy resin uses long-chain polypropylene glycol diglycidyl ether type epoxy resin, which has good compatibility with bisphenol A type glycidyl ether epoxy resin. When used in combination, it can improve the resin's permeability and toughness to the substrate. In an aqueous system, nanocellulose can form hydrogen bonds with hyperbranched molecular structures, synergistically mitigating the hard precipitation of white sand in the system and enhancing the adhesion strength.

[0011] Furthermore, it also includes 1-3 parts bentonite and 1-2 parts polyurethane thickener.

[0012] Furthermore, the bentonite is CT-06C bentonite; the polyurethane thickener is polyurethane thickener TRM-112. This application selected CT-06C bentonite and polyurethane thickener TRM-112, which have high compatibility with the resin system of this application, can adjust the resin viscosity, improve the dispersibility of white sand in the system, and improve the leveling properties of the system.

[0013] Furthermore, the wetting agent is TEGO270, and the silane coupling agent is MP200. The selected wetting agent TEGO270 exhibits excellent affinity for white sand, effectively wetting it. It also demonstrates good compatibility with the chosen resin, allowing the resin to completely encapsulate the sand. The silane coupling agent MP200 exhibits high compatibility and good adaptability with the resin system, improving the affinity between white sand and the resin system.

[0014] Furthermore, the white sand is 80-100 mesh. Adding white sand allows the interface treatment agent to form a rough contact surface on the substrate, increasing the contact area with subsequent construction and putty or primer, facilitating subsequent construction and enhancing adhesion. This application selects white sand with a relatively fine particle size; the particle size of the white sand should not be too large, otherwise sedimentation may easily occur. The 80-100 mesh white sand selected in this application ensures good dispersion and forms a rough contact surface on the substrate after application.

[0015] Further, component A comprises the following raw materials in parts by weight: 30 parts hyperbranched polyurethane modified epoxy resin, 40 parts 90-mesh white sand, 5 parts nanocellulose modified epoxy resin, 0.4 parts wetting agent TEGO270, 0.25 parts silane coupling agent MP200, 2 parts bentonite CT-06C, 1.5 parts polyurethane thickener TRM-112, and 27 parts deionized water; component B: 90 parts polyamide curing agent and 10 parts deionized water; the weight ratio of component A to component B is 30:1.

[0016] Further, the preparation method of the hyperbranched polyurethane modified epoxy resin is as follows: under a nitrogen atmosphere, toluene diisocyanate is added to a reaction vessel, and the temperature is raised to 80-85°C with stirring. Polyether polyol is then added dropwise, with n(toluene diisocyanate):n(polyether polyol) = 2-2.5:1. After the addition is complete, the mixture is kept at 80-85°C and stirred for 3-4 hours to obtain a polyurethane prepolymer. Hydroxyl-terminated hyperbranched polyester HyPer H103 is added to the above polyurethane prepolymer, and the mixture is stirred and reacted at 70-75°C for another 3-4 hours to obtain hyperbranched polyurethane. Bisphenol A type glycidyl ether epoxy resin E51 is added to the hyperbranched polyurethane at 3-5 times its weight, and the mixture is stirred and mixed at 80-85°C for 40-60 minutes to obtain the hyperbranched polyurethane modified epoxy resin.

[0017] Further, the preparation method of the nanocellulose modified epoxy resin is as follows: first, the nanocellulose MFC is surface-treated with silane coupling agent KH550, and the treated nanocellulose is added to long-chain polypropylene glycol diglycidyl ether type epoxy resin DER732. The mixture is stirred at high speed at 70-75℃ for 20-40 min to obtain nanocellulose modified epoxy resin; wherein, the mass ratio of silane coupling agent, nanocellulose, and long-chain polypropylene glycol diglycidyl ether type epoxy resin is 3-6:6-10:100.

[0018] Another object of the present invention is to provide a method for preparing the above-mentioned two-component epoxy interface treatment agent for repairing damaged walls, comprising the following steps:

[0019] Bentonite, polyurethane thickener and wetting agent were added to deionized water and dispersed at high speed to obtain the first mixture;

[0020] Hyperbranched polyurethane modified epoxy resin and nanocellulose modified epoxy resin were added to the first mixture, and the mixture was continued to be mixed at high speed to obtain the second mixture.

[0021] The surface of the white sand was modified with a silane coupling agent. The modified white sand was then added to the second mixture and dispersed and mixed evenly at a low speed.

[0022] Furthermore, the high-speed dispersion is achieved by stirring at 800-1200 r / m for 15-40 min; the low-speed dispersion is achieved by stirring at 50-200 r / min for 15-40 min.

[0023] Compared with the prior art, the beneficial effects of the present invention are: the two-component epoxy interface treatment agent for repairing damaged walls prepared in the embodiments of the present invention has excellent tensile bonding strength and toughness, as well as excellent permeability. It has excellent adhesion to different substrate surfaces, making it suitable for repairing damaged walls of different textures. It facilitates construction management, improves interface effect, and thus ensures repair quality. Detailed Implementation

[0024] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. The described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Unless otherwise specified, all methods described herein are conventional methods, and all raw materials described herein are available from publicly available commercial sources.

[0026] Example 1

[0027] A two-component epoxy-based interface treatment agent for repairing damaged walls, with the formulation being (component A: component B = 30:1).

[0028] Component A (parts by weight): 30 parts hyperbranched polyurethane modified epoxy resin, 40 parts 90-mesh white sand, 5 parts nanocellulose modified epoxy resin, 0.4 parts wetting agent TEGO270, 0.25 parts silane coupling agent MP200, 2 parts bentonite CT-06C, 1.5 parts polyurethane thickener TRM-112, 27 parts deionized water.

[0029] Component B (parts by weight): 90 parts polyamide curing agent, 10 parts deionized water.

[0030] Preparation process of component A: In a dispersion tank, add bentonite, polyurethane thickener, and wetting agent to deionized water according to the formula amount, and disperse at high speed at 800 r / min for 30 min. Then add hyperbranched polyurethane-modified epoxy resin and nano-cellulose-modified epoxy resin, and continue high-speed dispersion at 800 r / min for 15 min. Surface treat white sand with a silane coupling agent, and then add the treated white sand to the above resin solution, and disperse at low speed at 150 r / min for 30 min to obtain the final component. Preparation process of component B: In a dispersion tank, add polyamide curing agent and deionized water according to the formula amount, and disperse at 500 r / min for 15 min to obtain the final component.

[0031] The preparation method of hyperbranched polyurethane modified epoxy resin is as follows: Under a nitrogen atmosphere, toluene diisocyanate (TDI) is added to a reaction vessel, and the mixture is heated to 85°C with stirring. Polyether polyol PPG1000 (n(TDI):n(PPG) = 2:1) is then added dropwise. After the addition is complete, the mixture is kept at 85°C and stirred for 4 hours to obtain a polyurethane prepolymer. 5% by weight of terminal hydroxyl hyperbranched polyester HyPer H103 is added to the polyurethane prepolymer, and the mixture is stirred at 75°C for 4 hours to obtain hyperbranched polyurethane. Finally, 5 times the weight of glycidyl ether type epoxy resin E51 is added to the hyperbranched polyester, and the mixture is stirred and mixed at 80°C for 50 minutes to obtain the hyperbranched polyurethane modified epoxy resin.

[0032] The preparation method of nanocellulose modified epoxy resin is as follows: nanocellulose MFC is blended and modified with silane coupling agent KH550, and the modified nanocellulose is added to long-chain polypropylene glycol diglycidyl ether type epoxy resin DER732. The mixture is stirred at high speed at 75℃ for 30 min to obtain nanocellulose modified epoxy resin; wherein, the weight ratio of silane coupling agent, nanocellulose and long-chain polypropylene glycol diglycidyl ether type epoxy resin is 2.2:4.3:50.

[0033] Example 2

[0034] A two-component epoxy-based interface treatment agent for repairing damaged walls, with a formulation (component A:component B = 30:1).

[0035] Component A (parts by weight): 25 parts hyperbranched polyurethane modified epoxy resin, 38 parts 90-mesh white sand, 8 parts nanocellulose modified epoxy resin, 0.4 parts wetting agent TEGO270, 0.25 parts silane coupling agent MP200, 2 parts bentonite CT-06C, 1.5 parts polyurethane thickener TRM-112, 27 parts deionized water.

[0036] Component B (parts by weight): 90 parts polyamide curing agent, 10 parts deionized water.

[0037] The preparation methods for components A and B are the same as in Example 1, and the preparation methods for hyperbranched polyurethane modified epoxy resin and nanocellulose modified epoxy resin are the same as in Example 1.

[0038] Example 3

[0039] A two-component epoxy-based interface treatment agent for repairing damaged walls, with a formulation (component A:component B = 30:1).

[0040] Component A (parts by weight): 25 parts hyperbranched polyurethane modified epoxy resin, 32 parts 90-mesh white sand, 10 parts nanocellulose modified epoxy resin, 0.4 parts wetting agent TEGO270, 0.25 parts silane coupling agent MP200, 1 part bentonite CT-06C, 2 parts polyurethane thickener TRM-112, 27 parts deionized water.

[0041] Component B (parts by weight): 90 parts polyamide curing agent, 10 parts deionized water.

[0042] The preparation methods for components A and B are the same as in Example 1, and the preparation methods for hyperbranched polyurethane modified epoxy resin and nanocellulose modified epoxy resin are the same as in Example 1.

[0043] Example 4

[0044] A two-component epoxy-based interface treatment agent for repairing damaged walls, with a formulation (component A:component B = 30:1).

[0045] Component A (parts by weight): 28 parts hyperbranched polyurethane modified epoxy resin, 35 parts 90-mesh white sand, 10 parts nanocellulose modified epoxy resin, 0.4 parts wetting agent TEGO270, 0.25 parts silane coupling agent MP200, 1 part bentonite CT-06C, 2 parts polyurethane thickener TRM-112, 27 parts deionized water.

[0046] Component B (parts by weight): 90 parts polyamide curing agent, 10 parts deionized water.

[0047] The preparation methods for components A and B are the same as in Example 1, and the preparation methods for hyperbranched polyurethane modified epoxy resin and nanocellulose modified epoxy resin are the same as in Example 1.

[0048] Comparative Example 1

[0049] The formula and preparation method are the same as in Example 1, except that 60-mesh white sand is used.

[0050] Comparative Example 2

[0051] The formulation and preparation method in Example 1 are the same, except that nano-cellulose-modified epoxy resin was not added to the raw materials for component A.

[0052] Comparative Example 3

[0053] The formulation and preparation method in Example 1 are the same, except that the raw material for component A is prepared by using unmodified long-chain polypropylene glycol diglycidyl ether epoxy resin DER732 instead of nanocellulose modified epoxy resin.

[0054] Comparative Example 4

[0055] A two-component epoxy-based interface treatment agent for repairing damaged walls, with a formulation (component A:component B = 30:1).

[0056] Component A (parts by weight): 25 parts hyperbranched polyurethane modified epoxy resin, 38 parts 90-mesh white sand, 15 parts nanocellulose modified epoxy resin, 0.4 parts wetting agent TEGO270, 0.25 parts silane coupling agent MP200, 2 parts bentonite CT-06C, 1.5 parts polyurethane thickener TRM-112, 27 parts deionized water.

[0057] Component B (parts by weight): 90 parts polyamide curing agent, 10 parts deionized water.

[0058] The preparation methods for components A and B are the same as in Example 1, and the preparation methods for hyperbranched polyurethane modified epoxy resin and nanocellulose modified epoxy resin are the same as in Example 1.

[0059] Comparative Example 5

[0060] The formulation and preparation method in Example 1 are the same, except that the raw material for component A is prepared by using untreated polyurethane-modified epoxy resin instead of hyperbranched polyurethane-modified epoxy resin.

[0061] The preparation method of the polyurethane-modified epoxy resin is as follows: under a nitrogen atmosphere, toluene diisocyanate (TDI) is added to a reaction vessel, and the temperature is raised to 85°C with stirring. Polyether polyol PPG1000 (n(TDI):n(PPG) = 2:1) is added dropwise. After the addition is complete, the mixture is kept at 85°C and stirred for 4 hours to obtain a polyurethane prepolymer. Finally, glycidyl ether epoxy resin E51 with a weight of 5 times that of the polyurethane prepolymer is added, and the mixture is stirred and mixed at 80°C for 50 minutes to obtain a hyperbranched polyurethane-modified epoxy resin.

[0062] Performance testing

[0063] The epoxy-based interface treatment agents obtained in the examples and comparative examples were subjected to performance tests. The tensile bond strength was tested according to JC / T907-2018, the penetration depth according to DBJ01-54-2001, the elongation at break according to GB / T 2567-2021, the surface drying time according to GB / T1728-2020, and the viscosity was tested using a rotational viscometer. The performance test results are shown in Tables 1 and 2 below.

[0064] Table 1: Performance test results of the epoxy-based interface treatment agents in the examples

[0065]

[0066] Table 2: Performance test results of comparative epoxy-based interface treatment agents

[0067]

[0068]

[0069] In conjunction with Example 1 and Comparative Example 1, if the particle size of the white sand added to the resin is too large, the white sand will settle too quickly in the resin, making it difficult to coat evenly during the coating process, and the various properties of the interface treatment agent will decrease.

[0070] Combining Examples 1 and Comparative Examples 2-3, the combination of hyperbranched polyurethane-modified epoxy resin and nanocellulose-modified epoxy resin can improve the bonding strength and toughness of the interface treatment agent and enhance its adhesion to aluminum plates. Modifying long-chain polypropylene glycol diglycidyl ether type epoxy resin with nanocellulose can enhance the dispersion uniformity of white sand in the resin, improve the bonding strength and toughness of the resin, especially the tensile bonding strength after freeze-thaw cycles.

[0071] Combining Example 1 and Comparative Example 4, further increasing the addition ratio of nanocellulose-modified epoxy resin resulted in a longer resin drying time and affected the 7-day penetration depth.

[0072] Combined with Example 1 and Comparative Example 5, it can be seen that in the interface treatment agent system of this application, the use of HyPerH103 modified polyurethane to modify E51 can not only improve the toughness of the interface treatment agent, but also significantly improve its tensile bond strength and 7d penetration depth under freeze-thaw cycles.

[0073] In summary, the test results in the table above show that the two-component epoxy interface treatment agent for repairing damaged walls prepared in the embodiments of the present invention has excellent tensile bond strength and toughness, as well as excellent permeability and excellent adhesion to different substrate surfaces.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and not to limit them; although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of this application or equivalent substitutions can be made to some technical features, all of which should be covered within the scope of the technical solutions claimed in this application.

Claims

1. A two-component epoxy-based interface treatment agent for repairing damaged walls, characterized in that, It consists of component A and component B in a weight ratio of 25-35:1; Component A comprises the following raw materials in parts by weight: 20-40 parts hyperbranched polyurethane-modified epoxy resin, 30-50 parts white sand, 5-10 parts nanocellulose-modified epoxy resin, 0.2-0.5 parts wetting agent, 0.1-0.3 parts silane coupling agent, and 20-30 parts deionized water; the white sand is 80-100 mesh; Component A also includes 1-3 parts bentonite and 1-2 parts polyurethane thickener; Component B comprises the following raw materials in parts by weight: 85-95 parts polyamide curing agent, 5-15 parts deionized water; The preparation method of the hyperbranched polyurethane modified epoxy resin is as follows: a polyurethane prepolymer is obtained by adding dehydrated polyether polyol and toluene diisocyanate to a reaction vessel, a hyperbranched polyester with terminal hydroxyl groups is added to the polyurethane prepolymer to modify it into hyperbranched polyurethane, and bisphenol A type glycidyl ether epoxy resin is added to it and stirred to obtain hyperbranched polyurethane modified epoxy resin. The preparation method of nanocellulose modified epoxy resin is as follows: first, nanocellulose is surface-treated with a silane coupling agent, and then the treated nanocellulose is added to a long-chain polypropylene glycol diglycidyl ether type epoxy resin to obtain nanocellulose modified epoxy resin.

2. The two-component epoxy-based interface treatment agent for repairing damaged walls according to claim 1, characterized in that, The bentonite is CT-06C bentonite; the polyurethane thickener is polyurethane thickener TRM-112.

3. The two-component epoxy-based interface treatment agent for repairing damaged walls according to claim 1, characterized in that, The wetting agent is TEGO270, and the silane coupling agent is MP200.

4. The two-component epoxy-based interface treatment agent for repairing damaged walls according to claim 1, characterized in that, Component A comprises the following raw materials in parts by weight: 30 parts hyperbranched polyurethane modified epoxy resin, 5 parts nanocellulose modified epoxy resin, 40 parts 90-mesh white sand, 0.4 parts wetting agent TEGO270, 0.25 parts silane coupling agent MP200, 2 parts bentonite CT-06C, 1.5 parts polyurethane thickener TRM-112 and 27 parts deionized water; Component B comprises the following raw materials in parts by weight: 90 parts polyamide curing agent, 10 parts deionized water; Component A and component B are mixed in a weight ratio of 30:

1.

5. The two-component epoxy-based interface treatment agent for repairing damaged walls according to any one of claims 1-4, characterized in that, The preparation method of the hyperbranched polyurethane modified epoxy resin is as follows: under a nitrogen atmosphere, toluene diisocyanate is added to a reaction vessel, and the temperature is raised to 80-85°C with stirring. Polyether polyol is then added dropwise, with n(toluene diisocyanate):n(polyether polyol) = 2-2.5:

1. After the addition is complete, the mixture is kept at 80-85°C and stirred for 3-4 hours to obtain a polyurethane prepolymer. Hydroxyl-terminated hyperbranched polyester HyPer H103 is added to the above polyurethane prepolymer, and the mixture is stirred and reacted at 70-75°C for another 3-4 hours to obtain hyperbranched polyurethane. Bisphenol A type glycidyl ether epoxy resin E51 is added to the hyperbranched polyurethane at 3-5 times its weight, and the mixture is stirred and mixed at 80-85°C for 40-60 minutes to obtain the hyperbranched polyurethane modified epoxy resin.

6. The two-component epoxy-based interface treatment agent for repairing damaged walls according to any one of claims 1-4, characterized in that, The preparation method of the nanocellulose modified epoxy resin is as follows: first, nanocellulose MFC is surface-treated with silane coupling agent KH550, and the treated nanocellulose is added to long-chain polypropylene glycol diglycidyl ether type epoxy resin DER732. The mixture is stirred at high speed at 70-75℃ for 20-40 min to obtain nanocellulose modified epoxy resin; wherein, the mass ratio of silane coupling agent, nanocellulose, and long-chain polypropylene glycol diglycidyl ether type epoxy resin is 3-6:6-10:

100.

7. The method for preparing the two-component epoxy-based interface treatment agent for repairing damaged walls according to any one of claims 1-6, characterized in that, Includes the following steps: Bentonite, polyurethane thickener and wetting agent were added to deionized water and dispersed at high speed to obtain the first mixture; Hyperbranched polyurethane modified epoxy resin and nanocellulose modified epoxy resin were added to the first mixture, and the mixture was continued to be mixed at high speed to obtain the second mixture. The surface of the white sand was modified with a silane coupling agent. The modified white sand was then added to the second mixture and dispersed and mixed evenly at a low speed.

8. The preparation method of the two-component epoxy-based interface treatment agent for repairing damaged walls according to claim 7, characterized in that, The high-speed dispersion is achieved by stirring at 800-1200 r / min for 15-40 min; the low-speed dispersion is achieved by stirring at 50-200 r / min for 15-40 min.

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