Acrylic polyurethane / silane composite protective coating, preparation method thereof and application of acrylic polyurethane / silane composite protective coating in concrete surface protection

Abstract

The invention discloses an acrylic polyurethane / silane composite protective coating as well as a preparation method and application thereof in concrete surface protection, and belongs to the technical field of building coatings. The protective coating is used for the surface of concrete and comprises an epoxy putty layer, a modified silane dipping middle layer and a modified acrylic polyurethane surface coating from bottom to top, the modified silane impregnated middle layer is prepared from the following raw material components in parts by mass: 35 to 45 parts of silane impregnant, 0 to 5 parts of nano silicon dioxide, 0 to 5 parts of silica sol, 0 to 5 parts of ethyl silicate and 0 to 5 parts of polyurea; wherein the sum of the dosage of the nano silicon dioxide, the silica sol, the ethyl silicate and the polyurea is greater than 0. The characteristics of materials such as acrylic polyurethane, a silane impregnant and nano silicon dioxide are combined, the synergistic coupling effect of the components is exerted, and the protective facing function integrated concrete surface coating with the characteristics of deterioration repairing and strengthening, good durability, hydrophobic self-cleaning and the like is obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of architectural coatings, and more specifically, relates to an acrylic polyurethane / silane composite protective coating, a preparation method thereof, and an application in the protection of concrete surfaces. Background Art

[0002] Concrete is one of the most widely used building materials. Due to its hydrophilic characteristics and porous structure, water, corrosive media, etc. in the service environment are likely to enter the interior through its surface micropores and microcracks, thus affecting its strength and durability, and it is very likely that its service performance cannot meet the expectations. Preparing a functional coating on the concrete surface can block the adverse effects between the environment and the concrete without affecting the mechanical properties of the concrete, exert specific protective effects, and improve the long-term service performance of the concrete in engineering structures. The unique low surface energy and rough micro-nano structure characteristics of the hydrophobic coating make the surface of the coating present a non-wetting hydrophobic state with droplets, directly preventing water from carrying corrosive ions into the interior of the concrete and preventing the deterioration and damage of the concrete.

[0003] At present, the construction of hydrophobic protective coatings on the concrete surface mainly includes two protection mechanisms: surface penetration strengthening type and surface sealing type. The surface penetration strengthening type is to make the coating penetrate into the inner wall of the concrete pores to form a hydrophobic film, and carry out penetration crystallization with the cement hydration products to fill the micropores and improve the surface density. The advantages are good wear resistance and the ability to still play a hydrophobic role after wear, and the disadvantages are that it cannot completely seal the larger pores on the surface, and it is transparent and colorless and cannot play a decorative effect. The surface sealing type means to form a continuous and dense sealing film on the concrete surface. The advantages are to seal the surface pores and directly cut off the transportation path of external corrosive media into the concrete, and the disadvantages are that once the coating cracks, water and corrosive ions can enter from the cracks, resulting in the failure of the protection, and the currently common single nano-structure is relatively fragile, and the superhydrophobic coating formed is extremely vulnerable to mechanical external force wear, resulting in damage or shedding of the nano-structure, causing the reduction of its superhydrophobic characteristics.

[0004] Chinese Patent Application CN111647290A discloses a preparation method of a superhydrophobic self-cleaning coating. This method coats TiO2 in the form of nanoparticles on the outer surface of SiO2 to form a "micro-nano binary structure", and then cooperates with the modification of a low surface energy substance, polydimethylsiloxane (PDMS), to prepare a green, environmentally friendly and self-cleaning superhydrophobic coating. Among them, when irradiated with ultraviolet light or sunlight for 5 minutes, the coating changes from a superhydrophobic state to a hydrophilic state, and returns to the superhydrophobic state after calcination in a muffle furnace at 300 - 400 °C for 2 hours. However, when the number of repetitions is greater than 3 times, the coating finally becomes hydrophilic and no longer changes, and the coating has poor light aging resistance, and the hydrophobic performance fails in a long-term light environment. In addition, the coating is transparent and colorless, does not change the surface morphology of the concrete, and cannot play a decorative effect.

[0005] Chinese Patent Application CN102658685A discloses a preparation method of a polyurethane / polyurea composite protective layer. In this method, a polyurethane elastic layer is repeatedly brushed or sprayed on the concrete surface until the designed thickness is reached, and then at least one polyurea layer is sprayed on the surface of the last brushed or sprayed polyurethane layer when it is dry, so as to prepare a polyurethane / polyurea composite protective coating with excellent "waterproof, anti-corrosion, and impact resistance" properties. Among them, after the integrated protective coating is damaged by impact or freeze-thaw, local cracking or damage is likely to occur, and water and erosive ions etc. penetrate from the cracks, resulting in the failure of the overall protection.

[0006] Chinese Patent Application CN111484761A discloses a preparation method of an anti-icing and anti-ultraviolet coating. In this method, hexamethylenetetramine, zinc nitrate, and 1 - 5 μm Al2O3 are added to water and stirred for 24 h, and then fluorosilane and cenospheres are added successively and stirred at 2000 r / min for 24 h to obtain a sprayable hydrophobic, anti-icing, and ultraviolet-absorbing anti-icing and anti-ultraviolet coating. The contact angle of this coating is 153° - 157°, and the absorption wavelength is 340 nm - 351 nm. Among them, the micron structure of the single-layer sprayed superhydrophobic coating is relatively fragile and is easily damaged under the action of external force abrasion and impact. Summary of the Invention

[0007] In view of the defects of the existing concrete protective coatings, such as single function and insufficient durability, the present invention provides an acrylic polyurethane / silane composite protective coating, its preparation method, and its application in the surface protection of concrete. By combining the two protection mechanisms of surface sealing and surface penetration strengthening, the prepared protective finish functional integrated coating has characteristics such as damage repair and strengthening, good durability, hydrophobic self-cleaning, etc. The preparation method has the advantages of simplicity, convenience, and fast film formation, providing support for the good application of protective coatings in the field of building materials.

[0008] The technical solution of the present invention to solve the above technical problems is as follows:

[0009] An acrylic polyurethane / silane composite protective coating for the concrete surface, characterized in that it includes, from bottom to top: an epoxy putty layer, a modified silane impregnated intermediate layer, and a modified acrylic polyurethane topcoat; by mass, the raw material components of the modified silane impregnated intermediate layer include:

[0010] 35 - 45 parts of a silane impregnating agent, 0 - 5 parts of nano-silica, 0 - 5 parts of silica sol, 0 - 5 parts of ethyl silicate, 0 - 5 parts of polyurea; among them, the total amount of nano-silica, silica sol, ethyl silicate, and polyurea is greater than 0.

[0011] Preferably, by mass, the raw material components of the modified acrylic polyurethane topcoat include:

[0012] 32.5 - 42.5 parts of acrylic polyurethane, 0 - 2.5 parts of nano-silica, 0 - 2.5 parts of silica sol, 0 - 5 parts of ethyl silicate, 0 - 5 parts of polyurea, 0 - 5 parts of silane impregnating agent.

[0013] Preferably, the silane impregnating agent is DC-30 silane impregnating agent.

[0014] Preferably, the dosage of the modified silane impregnating intermediate layer and the modified acrylic polyurethane top coat is 0.3 - 0.35 L / m 2 .

[0015] The present invention also provides a preparation method of the above-mentioned acrylic polyurethane / silane composite protective coating, which comprises the following steps:

[0016] S1. Preparation of epoxy putty layer:

[0017] Disperse silica fume and epoxy resin evenly to obtain epoxy putty primer, and apply the epoxy putty primer on the concrete surface to make the surface flat;

[0018] S2. Preparation of modified silane impregnating intermediate layer:

[0019] Mix 35 - 45 parts of silane impregnating agent, 0 - 5 parts of nano-silica, 0 - 5 parts of silica sol, 0 - 5 parts of ethyl silicate, and 0 - 5 parts of polyurea evenly to obtain a modified silane impregnating agent, and coat the modified silane impregnating agent on the epoxy putty layer to form a modified silane impregnating intermediate layer;

[0020] S3. Preparation of modified acrylic polyurethane top coat:

[0021] Mix 32.5 - 42.5 parts of acrylic polyurethane, 0 - 2.5 parts of nano-silica, 0 - 2.5 parts of silica sol, 0 - 5 parts of ethyl silicate, 0 - 5 parts of polyurea, and 0 - 5 parts of silane impregnating agent evenly to obtain a modified acrylic polyurethane coating, and coat the coating on the modified silane impregnating intermediate layer to form a modified acrylic polyurethane top coat.

[0022] Preferably, in step S1, it further includes: curing at normal temperature after application.

[0023] Preferably, in step S2 or S3, the coating method is spraying and / or brushing.

[0024] Preferably, in step S2 or S3, the coating also includes curing at normal temperature after coating.

[0025] Preferably, in step S2 or S3, the number of coating times is 1 - 3 times; preferably, the time interval between single coatings is 2 - 3 h.

[0026] The present invention also provides an application of the above-mentioned acrylic polyurethane / silane composite protective coating in the protection of concrete surfaces.

[0027] The present invention adopts a superimposed composite protection method, combining two protection mechanisms of surface penetration strengthening type and surface sealing type. It not only penetrates and seals the micro-pores on the concrete surface, but also forms a sealed protective coating on the concrete surface. The double-layer protection improves the durability of the concrete and has an apparent finishing effect. Micron-sized materials are incorporated into the intermediate layer, and nano-sized materials are incorporated into the topcoat. Through multiple-step spraying, nano-SiO2 particles are deposited and adhered to the surface of silica fume, forming a multi-layered micro-nano composite rough structure to enhance the hydrophobic performance of the coating. Through the design of composite protection, the problem of easy failure of a single protection mechanism is solved, and by setting multiple rough structures on the surface and introducing hierarchical roughness, the hydrophobicity and durability of the coating are improved.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] (1) The present invention provides a layer-by-layer assembled acrylic polyurethane / silane composite protective coating. On the surface of the concrete substrate, an epoxy putty primer is used to fill and seal large pore defects; a modified silane impregnated intermediate layer penetrates and strengthens the concrete surface layer, enhances the adhesion, and forms the first layer of micron-sized rough structure; a modified acrylic polyurethane topcoat provides surface sealing protection and forms the second layer of nano-sized rough structure; combining the material properties of acrylic polyurethane, silane impregnating agent, and nano-silica, etc., and exerting the synergistic coupling effect of the components, a protective finishing functional integrated concrete surface coating with characteristics such as damage repair and strengthening, good durability, hydrophobic self-cleaning, etc. is obtained.

[0030] (2) Silica fume is incorporated into the intermediate layer, and nano-SiO2 is incorporated into the topcoat. Through multiple-step spraying, nano-SiO2 particles are deposited and adhered to the surface of silica fume, constructing a multi-layered micro-nano rough structure on the concrete surface, increasing the surface roughness, and incorporating a low surface energy material DC-30 silane impregnating agent into the topcoat to reduce the surface energy. The prepared acrylic polyurethane / silane composite protective coating has good hydrophobicity. The water contact angle on the surface of the intermediate layer can reach 124°, and the water contact angle on the surface of the topcoat can reach 100°.

[0031] (3) By combining the surface sealing effect of the acrylic polyurethane coating and the surface penetration strengthening effect of the silane impregnating agent, it not only directly improves the wear resistance of the surface coating, but also ensures that the new surface that may be exposed on the concrete surface itself still has protection ability, achieving a multi-layer protection effect and improving the overall wear resistance of the coating.

[0032] (4) The coating has excellent self-cleaning property and apparent finishing effect. Description of the Drawings

[0033] Figure 1 Hydrophobicity test results of the surface coating (T) and the intermediate layer (M) for the comparative examples and the examples;

[0034] Among them, T-1 to T-4 represent the surface coatings of Comparative Example 1 to Comparative Example 4, Shi T-1 to Shi T-4 represent the surface coatings of Example 1 to Example 4, Dui M-1 to Dui M-4 represent the intermediate layers of Comparative Example 1 to Comparative Example 4, and Shi M-1 to M-4 represent the intermediate layers of Example 1 to Example 4.

[0035] Figure 2 Relationship between the contact angle and the friction distance after friction of the surface coating (T) and the intermediate layer (M) for the comparative examples and the examples;

[0036] Among them, T-1 to T-4 represent the surface coatings of Comparative Example 1 to Comparative Example 4, Shi T-1 to Shi T-4 represent the surface coatings of Example 1 to Example 4, Dui M-1 to Dui M-4 represent the intermediate layers of Comparative Example 1 to Comparative Example 4, and Shi M-1 to M-4 represent the intermediate layers of Example 1 to Example 4.

[0037] Figure 3 Microscopic morphology of the sample surface, where (a) is the concrete surface without coating, (b) is the surface of the acrylic polyurethane / silane composite protective coating in Comparative Example 1, and (c) is the surface of the modified acrylic polyurethane / silane composite protective coating in Example 1.

[0038] Figure 4 Alkali corrosion resistance test results of the modified acrylic polyurethane / silane composite protective coating in Example 1 for 120 d;

[0039] Among them, (a) is the control group of Example 1 without soaking in alkali and cured naturally for 120 d, and (b) is the control group of Example 1 with soaking in alkali treatment for 120 d.

[0040] Figure 5 Self-cleaning performance display diagram of the modified acrylic polyurethane / silane composite protective coating in Example 1;

[0041] Among them, (a) is the surface of the contaminated coating without water flow applied, (b) is the surface of the contaminated coating with water flow continuously applied for 5 s, (c) is the surface of the contaminated coating with water flow continuously applied for 10 s, and (d) is the surface of the contaminated coating with water flow continuously applied for 15 s.

[0042] Figure 6 Finishing function effect display diagram of the modified acrylic polyurethane / silane composite protective coating in Example 1.

[0043] Among them, (a) is the surface morphology of the blank control concrete without coating, (b) is the surface morphology of the modified acrylic polyurethane / silane composite protective coating of Comparative Example 2 without an epoxy putty layer, and (c) is the surface morphology of the modified acrylic polyurethane / silane composite protective coating of Example 1. Detailed implementation mode

[0044] In the following description, many specific details are set forth in order to provide a thorough understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific implementations disclosed below.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. It should be noted that the reagents and the like used in this embodiment are all ordinary commercially available products.

[0046] Example 1

[0047] An acrylic polyurethane / silane composite protective coating, and its preparation method is as follows:

[0048] (1) Add 50 g of silica fume to 50 g of epoxy resin in small portions, and use a constant-speed mixer to adjust the rotation speed to 500 r / min and stir until the silica fume is evenly dispersed to obtain an epoxy putty primer;

[0049] (2) Disperse 5 g of nano-silica in 45 g of silane impregnating agent, and then homogenize and disperse it at room temperature for 1 hour to obtain a modified silane impregnating agent;

[0050] (3) Disperse 2.5 g of nano-silica and 5 g of silane impregnating agent in 42.5 g of acrylic polyurethane coating, and then homogenize and disperse it at room temperature for 1 hour to obtain a modified acrylic polyurethane coating;

[0051] (4) Apply the epoxy putty primer prepared in step (1) to the surface of the concrete substrate by a scraping process to fill and seal the larger pore defects on the concrete surface and make its surface basically flat;

[0052] (5) First, evenly spray the modified silane impregnating agent prepared in step (2) on the epoxy putty layer, and then evenly spray the modified acrylic polyurethane coating prepared in step (3) on the silane impregnating intermediate layer; for the parts that are not evenly sprayed, use a fine brush to apply supplementary coating, and air dry naturally at room temperature (23 ± 2 °C) for 24 hours to form an acrylic polyurethane / silane composite protective coating.

[0053] Example 2

[0054] A modified acrylic polyurethane / silane composite protective coating, and its preparation method is as follows:

[0055] (1) Add 50 g of silica fume to 50 g of epoxy resin in small portions multiple times, and use a constant-speed mixer to adjust the rotation speed to 500 r / min and stir until the silica fume is evenly dispersed to obtain an epoxy putty primer;

[0056] (2) Disperse 5 g of silica sol in 45 g of silane impregnating agent, and then carry out homogeneous dispersion for 1 hour at room temperature to obtain a modified silane impregnating agent;

[0057] (3) Disperse 2.5 g of silica sol and 5 g of silane impregnating agent in 42.5 g of acrylic polyurethane coating, and then carry out homogeneous dispersion for 1 hour at room temperature to obtain a modified acrylic polyurethane coating;

[0058] (4) Apply the epoxy putty primer prepared in step (1) to the surface of the concrete substrate by a scraping process to fill and seal the large pore defects on the concrete surface and make its surface basically flat;

[0059] (5) First, evenly spray the modified silane impregnating agent prepared in step (2) on the epoxy putty layer, and then evenly spray the modified acrylic polyurethane coating prepared in step (3) on the silane impregnating intermediate layer. The parts that are not evenly sprayed are supplemented by brushing with a fine brush, and air-dry naturally at room temperature (23±2°C) for 24 hours to form an acrylic polyurethane / silane composite protective coating.

[0060] Example 3

[0061] An acrylic polyurethane / silane composite protective coating, and its preparation method is as follows:

[0062] (1) Add 50 g of silica fume to 50 g of epoxy resin in small portions multiple times, and use a constant-speed mixer to adjust the rotation speed to 500 r / min and stir until the silica fume is evenly dispersed to obtain an epoxy putty primer;

[0063] (2) Disperse 5 g of nano-silica, 5 g of tetraethyl orthosilicate, and 5 g of polyurea in 35 g of silane impregnating agent, and then carry out homogeneous dispersion for 1 hour at room temperature to obtain a modified silane impregnating agent;

[0064] (3) Disperse 2.5 g of nano-silica, 5 g of silane impregnating agent, 5 g of tetraethyl orthosilicate, and 5 g of polyurea in 32.5 g of acrylic polyurethane coating, and then carry out homogeneous dispersion for 1 hour at room temperature to obtain a modified acrylic polyurethane coating;

[0065] (4) Apply the epoxy putty primer prepared in step (1) to the surface of the concrete substrate by scraping to fill and seal the large pore defects on the concrete surface, making its surface basically flat;

[0066] (5) Spray the modified silane impregnating agent prepared in step (2) evenly on the epoxy putty layer, and then spray the modified acrylic polyurethane coating prepared in step (3) evenly on the silane impregnating intermediate layer. For the parts that are not sprayed evenly, use a fine brush to apply supplementary coating. Air dry naturally at room temperature (23 ± 2 °C) for 24 hours to form an acrylic polyurethane / silane composite protective coating.

[0067] Example 4

[0068] The present invention provides an acrylic polyurethane / silane composite protective coating, comprising:

[0069] (1) Add 50 g of silica fume to 50 g of epoxy resin in small amounts and multiple times, and use a constant-speed mixer to adjust the rotation speed to 500 r / min and stir until the silica fume is evenly dispersed to obtain an epoxy putty primer;

[0070] (2) Disperse 5 g of silica sol, 5 g of ethyl silicate, and 5 g of polyurea in 35 g of silane impregnating agent, and then carry out homogeneous dispersion for 1 hour under normal temperature conditions to obtain a modified silane impregnating agent;

[0071] (3) Disperse 2.5 g of silica sol, 5 g of silane impregnating agent, 5 g of ethyl silicate, and 5 g of polyurea in 32.5 g of acrylic polyurethane coating, and then carry out homogeneous dispersion for 1 hour under normal temperature conditions to obtain a modified acrylic polyurethane coating;

[0072] (4) Apply the epoxy putty primer prepared in step (1) to the surface of the concrete substrate by scraping to fill and seal the large pore defects on the concrete surface, making its surface basically flat;

[0073] (5) Spray the modified silane impregnating agent prepared in step (2) evenly on the epoxy putty layer, and then spray the modified acrylic polyurethane coating prepared in step (3) evenly on the silane impregnating intermediate layer. For the parts that are not sprayed evenly, use a fine brush to apply supplementary coating. Air dry naturally at room temperature (23 ± 2 °C) for 24 hours to form an acrylic polyurethane / silane composite protective coating.

[0074] Control 1 Blank control

[0075] (1) Add 50 g of silica fume to 50 g of epoxy resin in small amounts and multiple times, and use a constant-speed mixer to adjust the rotation speed to 500 r / min and stir until the silica fume is evenly dispersed to obtain an epoxy putty primer;

[0076] (2) Apply the epoxy putty primer prepared in step (1) to the surface of the concrete substrate by means of scraping coating to fill and seal the larger pore defects on the concrete surface, making its surface basically flat;

[0077] (3) First, evenly spray the silane impregnating agent on the epoxy putty layer, and then evenly spray the acrylic polyurethane coating on the silane impregnating intermediate layer. For the parts that are not evenly sprayed, use a fine brush to make up the coating. Air dry naturally for 24 hours at room temperature (23 ± 2 °C) to form an acrylic polyurethane / silane composite protective coating.

[0078] Comparative Example 2

[0079] An acrylic polyurethane / silane composite protective coating, and its preparation method is as follows:

[0080] (1) Disperse 5 g of nano-silica in 45 g of silane impregnating agent, and then homogenize and disperse it at room temperature for 1 hour to obtain a modified silane impregnating agent;

[0081] (2) Disperse 2.5 g of nano-silica and 5 g of silane impregnating agent in 42.5 g of acrylic polyurethane coating, and then homogenize and disperse it at room temperature for 1 hour to obtain a modified acrylic polyurethane coating;

[0082] (3) First, evenly spray the modified silane impregnating agent prepared in step (1) on the concrete surface, and then evenly spray the modified acrylic polyurethane coating prepared in step (2) on the silane impregnating layer. For the parts that are not evenly sprayed, use a fine brush to make up the coating. Air dry naturally for 24 hours at room temperature (23 ± 2 °C) to form an acrylic polyurethane / silane composite protective coating.

[0083] The difference from Example 1 is that the epoxy putty layer is not coated.

[0084] Comparative Example 3

[0085] (1) Add 50 g of silica fume to 50 g of epoxy resin in small amounts and adjust the rotation speed of the constant-speed mixer to 500 r / min and stir until the silica fume is evenly dispersed to obtain an epoxy putty primer;

[0086] (2) Disperse 5 g of nano-silica in 45 g of silane impregnating agent, and then homogenize and disperse it at room temperature for 1 hour to obtain a modified silane impregnating agent;

[0087] (3) Apply the epoxy putty primer prepared in step (1) to the surface of the concrete substrate by means of scraping coating to fill and seal the larger pore defects on the concrete surface, making its surface basically flat;

[0088] (4) First, evenly spray the modified silane impregnating agent prepared in step (2) on the epoxy putty layer, and then evenly spray the acrylic polyurethane coating on the modified silane impregnating intermediate layer. For the parts that are not evenly sprayed, use a fine brush to touch up. Air dry naturally at room temperature (23 ± 2°C) for 24 hours to form an acrylic polyurethane / silane composite protective coating.

[0089] The difference from Example 1 is that the acrylic polyurethane coating is not modified.

[0090] Comparative Example 4

[0091] (1) Add 50 g of silica fume to 50 g of epoxy resin in small portions, and use a constant-speed mixer to adjust the rotation speed to 500 r / min and stir until the silica fume is evenly dispersed to obtain an epoxy putty primer.

[0092] (2) Disperse 2.5 g of nano-silica and 5 g of silane impregnating agent in 42.5 g of acrylic polyurethane coating, and then homogenize and disperse it at room temperature for 1 hour to obtain a modified acrylic polyurethane coating.

[0093] (3) Apply the epoxy putty primer prepared in step (1) to the surface of the concrete substrate by scraping process to fill and seal the large pore defects on the concrete surface and make its surface basically flat.

[0094] (4) First, evenly spray the silane impregnating agent on the epoxy putty layer, and then evenly spray the modified acrylic polyurethane coating prepared in step (2) on the silane impregnating intermediate layer. For the parts that are not evenly sprayed, use a fine brush to touch up. Air dry naturally at room temperature (23 ± 2°C) for 24 hours to form an acrylic polyurethane / silane composite protective coating.

[0095] The difference from Example 1 is that the silane impregnating agent is not modified.

[0096] To verify the hydrophobic, durable, self-cleaning and other properties of the multifunctional coating on the concrete surface of the present invention, the following performance tests were carried out.

[0097] 1) Hydrophobicity test

[0098] Measure the static contact angle (CA) with a static contact angle tester, and take the average value after multiple measurements to reflect the surface hydrophobicity of the coating. The larger the contact angle value, the better the surface hydrophobicity of the coating. If the contact angle is less than 90°, it is a hydrophilic surface, and if the contact angle is greater than 90°, it is a hydrophobic surface. The test results are as Figure 1As shown in the figure. When only the silane-impregnated intermediate layer was modified (Comparative Example 3), although the roughness of the surface layer increased, its surface energy could not be reduced, and the hydrophobicity of the overall coating decreased slightly instead. When only the acrylic polyurethane surface coating was modified (Comparative Example 4), the hydrophobicity improved significantly compared to the blank control group, but the hydrophobicity of the single-layer rough structure was slightly less than that of the composite protective coating. The contact angles of the examples with modified silane-impregnated intermediate layers were all greater than 100°; the average contact angle of the examples with modified acrylic polyurethane surface coatings increased by about 13 - 23°, and the average contact angle was 95.5°. Both the intermediate layer and the surface coating were hydrophobic surfaces, meeting the hydrophobic requirements.

[0099] 2) Abrasion resistance test

[0100] The abrasion resistance test was carried out according to the standard ASTM C779 / C779M-12 "Standard Test Method for Abrasion Resistance of Horizontal Concrete Surfaces". During the test, the sample was horizontally rubbed on the surface of sandpaper (1500 mesh) with a load, and the load weight and self-weight of the specimen generated a pressure of about 1000 Pa at the bottom. During the movement on the sandpaper surface, the specimen was pulled along one direction with a traction rope to ensure that only one horizontal pulling force acted on the sample. Each 150 cm movement was a friction cycle, and there were a total of ten cycles. After each friction cycle, the CA was measured and the average value was taken. The test results are as Figure 2 shown. Through the ten-cycle sandpaper wear test, when only the silane-impregnated intermediate layer was modified (Comparative Example 3), the hydrophobicity of both the intermediate layer and the surface layer was relatively poor, and with the increase of the friction distance, the contact angle of the coating gradually decreased. When only the acrylic polyurethane surface coating was modified (Comparative Example 4), the abrasion resistance of the coating improved compared to the blank control group, but compared with the composite protective coating, its contact angle decayed faster and the abrasion resistance effect was poor. The contact angles of the surface coating group all showed a downward trend with friction, but the contact angles of the examples were all higher than those of Comparative Example 1 without modification. The abrasion resistance of the surface coating of Example 3 with the simultaneous addition of nano-silica, silane impregnating agent and ethyl silicate was relatively the best and the working performance was the most stable. In the bottom coating group, due to the penetration of silane into the concrete surface layer to play a penetration crystallization role, a hydrophobic film was formed in the concrete pores, and the newly exposed surface after friction still had hydrophobicity, and the overall contact angle could be maintained at a high level. The contact angles of the intermediate layers of the examples were all higher than 95°, always meeting the hydrophobic requirements. Constructing two-layer hydrophobic coatings inside and outside is beneficial to ensuring the durability of the coating. Even if the surface coating is severely worn and the concrete base is exposed, the penetration crystallization effect has occurred within a certain depth of the surface concrete, ensuring that the coating can effectively play a hydrophobic role and preventing water and erosive ions from entering the concrete interior and causing adverse effects.

[0101] 3) Surface microtopography

[0102] The surface microstructure, element composition and content of the samples were observed and analyzed by scanning electron microscopy and energy dispersive spectrometry (SEM-EDS). Figure 3 As shown. There are a large number of hydrophilic particle structures on the surface of the concrete without coating, and the main elements are C, O, Ca, Si, etc., so the droplets diffuse and soak as soon as they fall on the concrete surface. The surface of the comparative example 1 test block coated with acrylic polyurethane / silane composite protective coating is flat, and the main elements are C, O, Ti, Al, etc., forming a complete film with good coverage on the concrete surface. The surface of the modified acrylic polyurethane / silane composite protective coating Example 3 with the addition of nano-silica, silane impregnating agent, ethyl silicate and polyurea is rough, and the main elements are C, O, Ti, Si, Al, etc., forming a relatively continuous polymer film structure. The polymer film wraps the nano-particle material to form a multi-layer micro-nano composite rough structure on the surface of the substrate, so that the coating surface can store more air, reduce the solid-liquid contact area between the coating surface and the water droplets, so as to enhance the hydrophobic performance of the coating. The silicon content increased significantly, indicating that the modification successfully introduced silane and nano-silica on the coating surface, verifying the improvement of the hydrophobic performance of the coating.

[0103] 4) Corrosion resistance test

[0104] According to JTJ275-2000 "Technical Specifications for Anti-corrosion of Concrete Structures in Seaport Engineering", the coating concrete should not blister or fall off after being immersed in a saturated Ca(OH)2 solution for 30 days. Figure 4 As shown. During the caustic soda ash process, the modified acrylic polyurethane / silane composite protective coating embodiment can maintain a relatively stable structure, and there is no internal gas accumulation due to the erosion of the alkali solution, which leads to bubbling and other undesirable phenomena on the coating surface. After cleaning the surface, the coating is still relatively firmly attached to the substrate, without the phenomenon of whole piece peeling or large-scale peeling. Only in some edges or local positions, there may be a very small amount of coating shedding due to mechanical friction and other factors during the cleaning process, but these shedding areas are very small and scattered, and will not have a serious impact on the overall integrity and protective performance of the coating. From an overall analysis, the performance of Example 1 of the modified acrylic polyurethane / silane composite protective coating with the addition of nano-silica and silane impregnating agent during the caustic soda ash process and after cleaning proves that it has good alkali resistance and stability.

[0105] 5) Self-cleaning performance test

[0106] Nano-silica powder was selected as a representative pollution source, and water was continuously applied to the coating surface with a dropper to observe the residual dust on the coating surface. The surface of the uncoated concrete is hydrophilic. Once a drop of water falls on the surface of the specimen, it spreads and infiltrates. The nano-silica powder infiltrates and agglomerates to form white stains. On the surface of the modified silane impregnated intermediate layer, the water drop does not infiltrate and the water flow can take away most of the powder, but there is still a small amount of powder residue adhering to the surface and cannot be completely removed. The test process on the surface of the modified acrylic polyurethane / silane composite protective coating Example 1 is as follows. Figure 5 As shown, a large amount of powder is taken away where the water flows. After continuous flushing for a period of time, the powder on the coating surface can be fully removed and no obvious residue is observed, indicating that the coating has good self-cleaning performance.

[0107] 6) Finishing function test

[0108] The paintability, leveling, recoatability, and film-forming properties of the acrylic polyurethane / silane composite protective coating were tested. Figure 6 It can be observed that there are many pore defects on the surface of the blank control concrete without coating. If the epoxy putty layer is not set, only the modified silane impregnation intermediate layer and the modified acrylic polyurethane topcoat cannot effectively close the large pores on the surface, resulting in an uneven coating surface, the protective function cannot be guaranteed, and the finish is not beautiful. After setting the epoxy putty primer, modified silane impregnation intermediate layer and modified acrylic polyurethane topcoat at the same time, the coating surface is smooth and flat, and the protective effect and finishing effect of the coating are good. The test results show that the coating has moderate consistency, is easy to apply, does not sag or wrinkle; has good leveling, is uniform and flat, and has no coating marks; has good recoatability, and multiple layers are still dense and uniform without stratification; has fast film formation, and is surface dry within 2 hours at room temperature (23±2℃) and is actually dry within 24 hours. After the coating dries, it can form a smooth and beautiful finishing layer with good finishing function.

[0109] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An acrylic polyurethane / silane composite protective coating for use on the surface of concrete, characterized in that, From bottom to top, it includes: Epoxy putty layer, modified silane impregnated intermediate layer and modified acrylic polyurethane topcoat; By mass, the raw material components of the modified silane impregnated intermediate layer include: 35 - 45 parts of silane impregnating agent, 0 - 5 parts of nano-silica, 0 - 5 parts of silica sol, 0 - 5 parts of ethyl silicate, 0 - 5 parts of polyurea; among them, the sum of the dosages of nano-silica, silica sol, ethyl silicate, and polyurea is greater than 0; The raw material components of the modified acrylic polyurethane topcoat include: 32.5 - 42.5 parts of acrylic polyurethane, 0 - 2.5 parts of nano-silica, silica sol, 0 - 2.5 parts of silica fume, 0 - 5 parts of ethyl silicate, 0 - 5 parts of polyurea, 0 - 5 parts of silane impregnating agent.

2. The acrylic polyurethane / silane composite protective coating according to claim 1, characterized in that, The silane impregnating agent is DC - 30 silane impregnating agent.

3. The acrylic polyurethane / silane composite protective coating according to claim 1, wherein The dosage of the modified silane impregnated intermediate layer and the modified acrylic polyurethane top coating is 0.3 - 0.35 L / m 2 .

4. The preparation method of the acrylic polyurethane / silane composite protective coating according to any one of claims 1 to 3, characterized in that, It includes the following steps: S1. Preparation of epoxy putty layer: Uniformly disperse silica fume and epoxy resin to obtain epoxy putty primer, and apply the epoxy putty primer on the concrete surface to make the surface flat; S2. Preparation of modified silane impregnated intermediate layer: Mix 35 - 45 parts of silane impregnating agent, 0 - 5 parts of nano-silica, 0 - 5 parts of silica sol, 0 - 5 parts of ethyl silicate, and 0 - 5 parts of polyurea evenly to obtain a modified silane impregnating agent, and apply the modified silane impregnating agent on the epoxy putty layer to form a modified silane impregnated intermediate layer; S3. Preparation of modified acrylic polyurethane topcoat: Mix 32.5 - 42.5 parts of acrylic polyurethane, 0 - 2.5 parts of nano-silica, 0 - 2.5 parts of silica sol, 0 - 5 parts of ethyl silicate, 0 - 5 parts of polyurea, and 0 - 5 parts of silane impregnating agent evenly to obtain a modified acrylic polyurethane coating, and apply the coating on the modified silane impregnated intermediate layer to form a modified acrylic polyurethane topcoat.

5. The preparation method according to claim 4, characterized in that, In step S1, it also includes: Carry out curing by normal temperature maintenance after application.

6. The preparation method according to claim 4, characterized in that, In step S2 or S3, the coating method is spraying and / or brushing.

7. The preparation method according to claim 4, wherein In step S2 or S3, in step S2 or S3, the coating also includes curing by normal temperature maintenance after coating.

8. The preparation method according to claim 4, characterized in that, In step S2 or S3, the number of coating times is 1 - 3 times; preferably, the time interval between single coatings is 2 - 3h.

9. Application of the acrylic polyurethane / silane composite protective coating according to any one of claims 1 - 3 in the surface protection of concrete.

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