An acrylic polyurethane / silane composite protective coating, its preparation method and application in concrete surface protection

Abstract

The application discloses an acrylic polyurethane / silane composite protective coating and a preparation method and application thereof in concrete surface protection, and belongs to the technical field of building coatings. The protective coating is used on the concrete surface and comprises, from bottom to top, an epoxy putty layer, a modified silane impregnated intermediate layer and a modified acrylic polyurethane top coating layer. The raw material components of the modified silane impregnated intermediate layer include, in terms of mass parts, 35-45 parts of a silane impregnating agent, 0-5 parts of nano-silicon dioxide, 0-5 parts of silica sol, 0-5 parts of ethyl silicate and 0-5 parts of polyurea. The sum of the amounts of the nano-silicon dioxide, the silica sol, the ethyl silicate and the polyurea is greater than 0. The application combines the material properties of the acrylic polyurethane, the silane impregnating agent and the nano-silicon dioxide, and plays the component synergistic coupling effect, so that the protective surface coating with the functions of damage repair and reinforcement, good durability, hydrophobic self-cleaning and the like is obtained.

Description

TECHNICAL FIELD

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

[0002] Concrete is one of the most widely used building materials. Due to its hydrophilic properties and porous structure, water, corrosive media and the like in the service environment can easily enter the interior through the surface micropores and microcracks, thereby affecting the strength and durability of the concrete and possibly failing to achieve the expected service performance. Preparing a functional coating on the surface of the concrete can block the adverse effects between the environment and the concrete without affecting the mechanical properties of the concrete, thereby playing a specific protective effect and improving the long-term service performance of the concrete of the engineering structure. The unique low surface energy and rough micro-nano structure of the hydrophobic coating make the coating surface and the liquid droplets exhibit a non-wetting hydrophobic state, thereby directly preventing water from carrying corrosive ions into the interior of the concrete and preventing the deterioration and damage of the concrete.

[0003] Currently, the construction of a hydrophobic protective coating on the surface of the concrete mainly includes two protective mechanisms, namely, a surface penetration strengthening type and a surface sealing type. The surface penetration strengthening type is to make the coating penetrate into the inner wall of the pores of the concrete to form a hydrophobic film and to perform a penetration crystallization with the cement hydration products to fill the micropores and improve the compactness of the surface layer. The advantage is good wear resistance, and the hydrophobic effect can still be played after wear. The disadvantage is that it cannot completely seal the larger pores on the surface, and it cannot play a finishing effect because it is transparent and colorless. The surface sealing type is to form a continuous and dense sealing film on the surface of the concrete. The advantage is to seal the surface pores and directly cut off the transport path of the external corrosive medium into the concrete. The disadvantage is that once the coating cracks, water and corrosive ions can enter from the cracks to cause the protective effect to fail. In addition, the commonly used single nano structure is relatively fragile, and the super-hydrophobic coating formed by the nano structure is easily damaged or peeled off by mechanical external force, thereby reducing the super-hydrophobic property.

[0004] Chinese patent application CN111647290A discloses a preparation method of a super-hydrophobic self-cleaning coating. The method coats TiO2 in the form of nanoparticles on the outer surface of SiO2 to form a “micro-nano dual structure”, and then modifies it with a low surface energy substance, polydimethylsiloxane (PDMS), to prepare a green and environmentally friendly, self-cleaning super-hydrophobic coating. Under ultraviolet light or sunlight, the coating changes from a super-hydrophobic state to a hydrophilic state after 5 minutes of irradiation, and returns to a super-hydrophobic state after being baked in a muffle furnace at 300-400°C for 2 hours. However, when the number of repetitions is greater than 3, the coating eventually becomes hydrophilic and no longer changes. The light aging resistance of the coating is poor, and the hydrophobic property is lost 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 finishing effect.

[0005] Chinese patent application CN102658685A discloses a preparation method of a polyurethane / polyurea composite protective layer. The method is to brush or spray a polyurethane elastic layer on the surface of the concrete multiple times until the designed thickness is reached, and then spray at least one polyurea layer on the surface of the last brushed or sprayed polyurethane layer when it is dry. A polyurethane / polyurea composite protective coating with excellent "waterproof, corrosion-resistant, and impact-resistant" performance is prepared. However, the integrated protective coating is prone to local cracking or damage after being impacted or freeze-thaw damaged, and water and erosive ions penetrate from the cracks, resulting in overall failure of protection.

[0006] Chinese patent application CN111484761A discloses a preparation method of an anti-icing and anti-ultraviolet coating. The method is to add hexamethylenetetramine, zinc nitrate, and 1-5 micrometer Al2O3 into water and stir for 24 hours, then add fluorosilane and floating beads in turn and stir for 24 hours. A sprayable anti-icing and anti-ultraviolet coating with hydrophobic, anti-icing, and ultraviolet absorption properties is obtained. The contact angle of the coating is 153°-157°, and the absorption wavelength is 340nm-351nm. However, the micrometer structure of the single-layer sprayed super-hydrophobic coating is relatively fragile and is easily damaged under the action of external force abrasion and impact. SUMMARY

[0007] The present application aims to solve the problems of single function and insufficient durability of the prior art concrete protective coating. A kind of acrylic polyurethane / silane composite protective coating, its preparation method and application in concrete surface protection are proposed. The prepared protective finishing function integrated coating has the characteristics of damage repair and reinforcement, good durability, and hydrophobic self-cleaning, and the preparation method has the advantages of simplicity, convenience, and fast film formation, which provides support for the good application of protective coating in the field of building materials.

[0008] The technical solutions of the present application to solve the above technical problems are as follows:

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

[0010] 35-45 parts of silane impregnant, 0-5 parts of nano-silicon dioxide, 0-5 parts of silica sol, 0-5 parts of ethyl silicate, and 0-5 parts of polyurea. The sum of the amounts of nano-silicon dioxide, silica sol, ethyl silicate, and polyurea is greater than 0.

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

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

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

[0014] Preferably, the amount of the modified silane impregnation intermediate layer and the modified acrylic polyurethane topcoat layer is 0.3-0.35L / m 2 .

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

[0016] S1, preparation of the epoxy putty layer:

[0017] The silica ash and the epoxy resin are uniformly dispersed to obtain an epoxy putty primer, and the epoxy putty primer is applied to the surface of the concrete to make the surface flat;

[0018] S2, preparation of the modified silane impregnation intermediate layer:

[0019] The silane impregnant 35-45 parts, nano-silica 0-5 parts, silica sol 0-5 parts, ethyl silicate 0-5 parts, and polyurea 0-5 parts are uniformly mixed to obtain a modified silane impregnant, and the modified silane impregnant is coated on the epoxy putty layer to form a modified silane impregnation intermediate layer;

[0020] S3, preparation of the modified acrylic polyurethane topcoat layer:

[0021] The acrylic polyurethane 32.5-42.5 parts, nano-silica 0-2.5 parts, silica sol 0-2.5 parts, ethyl silicate 0-5 parts, polyurea 0-5 parts, and silane impregnant 0-5 parts are uniformly mixed to obtain a modified acrylic polyurethane coating, and the coating is coated on the modified silane impregnation intermediate layer to form a modified acrylic polyurethane topcoat layer.

[0022] Preferably, in step S1, it further comprises: after application, normal temperature curing and solidification.

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

[0024] Preferably, in step S2 or S3, the coating further comprises normal temperature curing and solidification after coating.

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

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

[0027] The application adopts the way of superimposed composite protection, combines the surface layer penetration strengthening type and the surface layer sealing type two protection mechanisms, penetrates and seals the micro-pore of the concrete surface, forms a closed protective coating on the concrete surface, the double-layer protection improves the durability of the concrete and has the apparent finishing effect. The micron-sized material is mixed in the intermediate layer, and the nano-sized material is mixed in the surface coating, through multiple step spraying, the nano-SiO2 particles are deposited and attached to the surface of the silica fume, forming a multi-layer stacked micro-nano composite rough structure to enhance the hydrophobicity of the coating. Through the design of composite protection, the problem of easy failure of single protection mechanism is solved, and through the setting of multiple rough structures on the surface, the layered roughness is introduced to improve the hydrophobicity and durability of the coating.

[0028] Compared with the prior art, the application has the following beneficial effects:

[0029] (1) The application provides a layer-by-layer assembled acrylic polyurethane / silane composite protective coating, which fills and seals larger pore defects on the surface of a concrete base by using an epoxy putty primer layer, penetrates and strengthens the surface layer of the concrete by using a modified silane impregnated intermediate layer, forms a first micron-sized rough structure, and forms a second nano-sized rough structure by using a modified acrylic polyurethane surface coating for surface sealing protection. The properties of acrylic polyurethane, silane impregnant, and nano-silicon dioxide are combined to achieve component synergistic coupling effect, and a protective and finishing integrated concrete surface coating with damage repair and strengthening, good durability, hydrophobic self-cleaning, and other properties is obtained.

[0030] (2) The silica fume is mixed in the intermediate layer, and the nano-SiO2 is mixed in the surface coating. Through multiple step spraying, the nano-SiO2 particles are deposited and attached to the surface of the silica fume, a multi-layer stacked micro-nano rough structure is constructed on the surface of the concrete, the roughness of the surface is increased, and the low surface energy material DC-30 silane impregnant is mixed in the surface coating to reduce the surface energy. The prepared acrylic polyurethane / silane composite protective coating has good hydrophobicity. The water contact angle of the surface of the intermediate layer can reach 124°, and the water contact angle of the surface of the surface coating can reach 100°.

[0031] (3) The surface sealing effect of the acrylic polyurethane coating and the surface layer penetration strengthening effect of the silane impregnant are combined, which directly improves the wear resistance of the surface coating and ensures that the new surface exposed on the concrete surface still has protection ability, realizes the multi-layer protection effect, and improves the overall wear resistance of the coating.

[0032] (4) The coating has excellent self-cleaning property and apparent finishing effect. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 Test results of hydrophobicity of the top coat (T) and the intermediate layer (M) of the comparative examples and the examples;

[0034] wherein Comp T-1 to Comp T-4 represent the top coat of Comparative Example 1 to Comparative Example 4, Real T-1 to Real T-4 represent the top coat of Example 1 to Example 4, Comp M-1 to Comp M-4 represent the intermediate layer of Comparative Example 1 to Comparative Example 4, and Real M-1 to Real M-4 represent the intermediate layer of Example 1 to Example 4.

[0035] Figure 2 Relationship between the contact angle after rubbing and the rubbing distance of the top coat (T) and the intermediate layer (M) of the comparative examples and the examples;

[0036] wherein Comp T-1 to Comp T-4 represent the top coat of Comparative Example 1 to Comparative Example 4, Real T-1 to Real T-4 represent the top coat of Example 1 to Example 4, Comp M-1 to Comp M-4 represent the intermediate layer of Comparative Example 1 to Comparative Example 4, and Real M-1 to Real M-4 represent the intermediate layer of Example 1 to Example 4.

[0037] Figure 3 Surface micro-morphology of the samples, wherein (a) is the surface of the concrete 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 Test results of the alkali corrosion resistance of the modified acrylic polyurethane / silane composite protective coating 120d in Example 1;

[0039] wherein (a) is the control group of Example 1 without alkali foaming and natural curing for 120d, and (b) is the control group of Example 1 with alkali foaming for 120d.

[0040] Figure 5 Display diagram of the self-cleaning performance of the modified acrylic polyurethane / silane composite protective coating in Example 1.

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

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

[0043] Wherein, (a) is the surface morphology of the blank control concrete surface without coating, (b) is the surface morphology of the modified acrylic polyurethane / silane composite protective coating comparative example 2 without the epoxy putty layer, and (c) is the surface morphology of the modified acrylic polyurethane / silane composite protective coating example 1. DETAILED DESCRIPTION

[0044] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced without the specific details, other than those described herein, which are well known in the art. Those skilled in the art, having the benefit of the teachings of the present application, as set forth in the specification, can effect numerous modifications thereto and changes therein without departing from the scope of the present application.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the present application. It is to be understood that the singular forms "a", "an", and "the" include plural references unless the context clearly dictates otherwise.

[0046] Example 1

[0047] A kind of acrylic polyurethane / silane composite protective coating, its preparation method is:

[0048] (1) a small amount of silica fume is added to 50g of epoxy resin for several times, the stirring speed of constant speed stirrer is adjusted to 500r / min, and stirring is carried out until the silica fume is uniformly dispersed, to obtain an epoxy putty primer;

[0049] (2) 5g of nano-silicon dioxide is dispersed in 45g of silane impregnant, and then homogenously dispersed for 1 hour at room temperature to obtain a modified silane impregnant;

[0050] (3) 2.5g of nano-silicon dioxide and 5g of silane impregnant are dispersed in 42.5g of acrylic polyurethane coating, and then homogenously dispersed for 1 hour at room temperature to obtain a modified acrylic polyurethane coating;

[0051] (4) the epoxy putty primer prepared in step (1) is coated on the surface of the concrete substrate by scraping process to fill and close the larger pore defects on the surface of the concrete, so that the surface is basically flat;

[0052] (5) the modified silane impregnant prepared in step (2) is uniformly sprayed on the epoxy putty layer, and the modified acrylic polyurethane coating prepared in step (3) is uniformly sprayed on the silane impregnant intermediate layer; the non-uniformly sprayed parts are supplemented by brushing with a fine brush, and then naturally air-dried for 24 hours at room temperature (23±2℃) to form an acrylic polyurethane / silane composite protective coating.

[0053] Example 2

[0054] A modified acrylic polyurethane / silane composite protective coating, the preparation method thereof is:

[0055] (1) A small amount of silica fume is added to 50 g of epoxy resin for multiple times, and a constant speed mixer is used to adjust the speed to 500 r / min to stir until the silica fume is uniformly dispersed, to obtain an epoxy putty primer;

[0056] (2) 5 g of silica sol is dispersed in 45 g of silane impregnant, and then homogeneously dispersed at room temperature for 1 hour to obtain a modified silane impregnant;

[0057] (3) 2.5 g of silica sol and 5 g of silane impregnant are dispersed in 42.5 g of acrylic polyurethane coating, and then homogeneously dispersed at room temperature for 1 hour to obtain a modified acrylic polyurethane coating;

[0058] (4) The epoxy putty primer prepared in step (1) is coated on the surface of the concrete substrate by scraping process to fill and close the larger pore defects on the surface of the concrete, so that the surface is basically flat;

[0059] (5) The modified silane impregnant prepared in step (2) is uniformly sprayed on the epoxy putty layer, and the modified acrylic polyurethane coating prepared in step (3) is uniformly sprayed on the silane impregnant intermediate layer, and the non-uniformly sprayed part is supplemented by brushing with a fine brush, and then naturally air-dried at room temperature (23±2℃) for 24 hours to form an acrylic polyurethane / silane composite protective coating.

[0060] Example 3

[0061] An acrylic polyurethane / silane composite protective coating, the preparation method thereof is:

[0062] (1) A small amount of silica fume is added to 50 g of epoxy resin for multiple times, and a constant speed mixer is used to adjust the speed to 500 r / min to stir until the silica fume is uniformly dispersed, to obtain an epoxy putty primer;

[0063] (2) 5 g of nano-silica, 5 g of ethyl silicate, and 5 g of polyurea are dispersed in 35 g of silane impregnant, and then homogeneously dispersed at room temperature for 1 hour to obtain a modified silane impregnant;

[0064] (3) 2.5 g of nano-silica, 5 g of silane impregnant, 5 g of ethyl silicate, and 5 g of polyurea are dispersed in 32.5 g of acrylic polyurethane coating, and then homogeneously dispersed at room temperature for 1 hour to obtain a modified acrylic polyurethane coating;

[0065] (4) The epoxy putty primer prepared in step (1) is applied to the surface of the concrete substrate by a scraping process to fill and close the larger air hole defects on the surface of the concrete, so that the surface is basically flat;

[0066] (5) The modified silane impregnant prepared in step (2) is uniformly sprayed on the epoxy putty layer, and the modified acrylic polyurethane coating prepared in step (3) is uniformly sprayed on the silane impregnation intermediate layer. The non-uniformly sprayed parts are supplemented by fine brush coating. After being naturally air-dried at room temperature (23±2℃) for 24 hours, an acrylic polyurethane / silane composite protective coating is formed.

[0067] Example 4

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

[0069] (1) A small amount of silica fume is added to 50g of epoxy resin for multiple times, and a constant speed mixer is used to adjust the speed to 500r / min to stir until the silica fume is uniformly dispersed, to prepare an epoxy putty primer;

[0070] (2) 5g of silica sol, 5g of ethyl silicate and 5g of polyurea are dispersed in 35g of silane impregnant, and then homogeneously dispersed at room temperature for 1 hour to obtain a modified silane impregnant;

[0071] (3) 2.5g of silica sol, 5g of silane impregnant, 5g of ethyl silicate and 5g of polyurea are dispersed in 32.5g of acrylic polyurethane coating, and then homogeneously dispersed at room temperature for 1 hour to obtain a modified acrylic polyurethane coating;

[0072] (4) The epoxy putty primer prepared in step (1) is applied to the surface of the concrete substrate by a scraping process to fill and close the larger air hole defects on the surface of the concrete, so that the surface is basically flat;

[0073] (5) The modified silane impregnant prepared in step (2) is uniformly sprayed on the epoxy putty layer, and the modified acrylic polyurethane coating prepared in step (3) is uniformly sprayed on the silane impregnation intermediate layer. The non-uniformly sprayed parts are supplemented by fine brush coating. After being naturally air-dried at room temperature (23±2℃) for 24 hours, an acrylic polyurethane / silane composite protective coating is formed.

[0074] Comparative Example 1

[0075] (1) A small amount of silica fume is added to 50g of epoxy resin for multiple times, and a constant speed mixer is used to adjust the speed to 500r / min to stir until the silica fume is uniformly dispersed, to prepare an epoxy putty primer;

[0076] (2) The epoxy putty primer prepared in step (1) is applied to the surface of the concrete substrate by a scraping process to fill and close the larger air hole defects on the surface of the concrete, so that the surface is substantially flat;

[0077] (3) The silane impregnant is uniformly sprayed on the epoxy putty layer, and the acrylic polyurethane coating is uniformly sprayed on the silane impregnant intermediate layer. The parts not uniformly sprayed are supplemented by brushing with a fine brush. After being naturally air-dried at room temperature (23±2℃) for 24 hours, an acrylic polyurethane / silane composite protective coating is formed.

[0078] Comparative Example 2

[0079] An acrylic polyurethane / silane composite protective coating is prepared by the following method:

[0080] (1) 5g of nanometer silicon dioxide is dispersed in 45g of silane impregnant, and then homogeneously dispersed at room temperature for 1 hour to obtain modified silane impregnant;

[0081] (2) 2.5g of nanometer silicon dioxide and 5g of silane impregnant are dispersed in 42.5g of acrylic polyurethane coating, and then homogeneously dispersed at room temperature for 1 hour to obtain modified acrylic polyurethane coating;

[0082] (3) The modified silane impregnant prepared in step (1) is uniformly sprayed on the surface of the concrete, and the modified acrylic polyurethane coating prepared in step (2) is uniformly sprayed on the silane impregnant layer. The parts not uniformly sprayed are supplemented by brushing with a fine brush. After being naturally air-dried at room temperature (23±2℃) for 24 hours, an acrylic polyurethane / silane composite protective coating is formed.

[0083] The difference from Example 1 is that no epoxy putty layer is coated.

[0084] Comparative Example 3

[0085] (1) 50g of silica is added to 50g of epoxy resin in small amounts and multiple times. A constant speed mixer is used to adjust the speed to 500r / min to stir until the silica is uniformly dispersed, to obtain an epoxy putty primer;

[0086] (2) 5g of nanometer silicon dioxide is dispersed in 45g of silane impregnant, and then homogeneously dispersed at room temperature for 1 hour to obtain modified silane impregnant;

[0087] (3) The epoxy putty primer prepared in step (1) is applied to the surface of the concrete substrate by a scraping process to fill and close the larger air hole defects on the surface of the concrete, so that the surface is substantially flat;

[0088] (4) First, the modified silane impregnant prepared in step (2) is uniformly sprayed on the epoxy putty layer, and then the acrylic polyurethane coating is uniformly sprayed on the modified silane impregnated intermediate layer. The part not uniformly sprayed is supplemented by using a fine brush to brush the coating. After being naturally air-dried at room temperature (23±2℃) for 24 hours, an acrylic polyurethane / silane composite protective coating is formed.

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

[0090] Comparative Example 4

[0091] (1) A small amount of silica fume is added to 50g of epoxy resin for multiple times, and the stirring speed of a constant speed stirrer is adjusted to 500r / min until the silica fume is uniformly dispersed, to prepare an epoxy putty primer;

[0092] (2) 2.5g of nano-silicon dioxide and 5g of silane impregnant are dispersed in 42.5g of acrylic polyurethane coating, and then homogenously dispersed at room temperature for 1 hour to obtain a modified acrylic polyurethane coating;

[0093] (3) The epoxy putty primer prepared in step (1) is coated on the surface of the concrete substrate by using a scraping process to fill and close the larger pore defects on the surface of the concrete, so that the surface is basically flat;

[0094] (4) First, the silane impregnant is uniformly sprayed on the epoxy putty layer, and then the modified acrylic polyurethane coating prepared in step (2) is uniformly sprayed on the silane impregnated intermediate layer. The part not uniformly sprayed is supplemented by using a fine brush to brush the coating. After being naturally air-dried at room temperature (23±2℃) for 24 hours, an acrylic polyurethane / silane composite protective coating is formed.

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

[0096] In order to verify the hydrophobic, durable, self-cleaning performance and other effects of the multifunctional coating on the surface of the concrete of the present application, the following performance tests are carried out.

[0097] 1) Hydrophobicity test

[0098] The static contact angle (CA) is measured by a static contact angle tester, and the average value is taken 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 follows: Figure 1The roughness of the surface layer was improved, but the surface energy was not reduced, and the overall coating hydrophobicity was slightly decreased. When only the acrylic polyurethane topcoat layer was modified (Comparative Example 4), the hydrophobicity was greatly improved compared to the blank control group, but the single-layer rough structure resulted in a slightly lower hydrophobicity than the composite protective coating. The contact angles of the modified silane impregnated interlayer examples were all greater than 100°; the average contact angle of the modified acrylic polyurethane topcoat layer examples increased by about 13-23°, with an average contact angle of 95.5°. Both the interlayer and the topcoat layer were hydrophobic surfaces, meeting the hydrophobicity requirements.

[0099] 2) Abrasion Resistance Test

[0100] The abrasion resistance test was based on the standard ASTM C779 / C779M-12 "Standard Test Method for Abrasion Resistance of Horizontal Concrete Pavements". During the test, the sample was horizontally rubbed on the surface of sandpaper (1500 mesh) under a load, and the load and self-weight at the bottom generated a pressure of about 1000 Pa. During the movement on the sandpaper surface, the sample was pulled in one direction by a pulling rope to ensure that only a horizontal pulling force acted on the sample. Each movement of 150 cm was one rubbing cycle, and there were a total of ten cycles. After each rubbing cycle, the CA was measured and the average value was taken. The test results are shown in Table 3. Figure 2 After ten cycles of sandpaper abrasion test, when only the silane impregnated interlayer was modified (Comparative Example 3), the hydrophobicity of the interlayer and the topcoat layer was relatively poor, and the coating contact angle gradually decreased with the increase of the friction distance. When only the acrylic polyurethane topcoat layer was modified (Comparative Example 4), the coating abrasion resistance was improved compared to the blank control group, but compared to the composite protective coating, its contact angle decayed faster and the abrasion resistance was poorer. The contact angles of the topcoat layer 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 topcoat layer of Example 3, which added nano-silicon dioxide, silane impregnant and ethyl silicate, was relatively the best, and the working performance was the most stable. The bottom coat group penetrated into the concrete surface layer due to the penetration of silane, formed a hydrophobic film in the pores of the concrete, and the newly exposed surface after friction still had hydrophobicity, and the overall coating could maintain a high contact angle. The contact angles of the interlayer in the examples were all higher than 95°, always meeting the hydrophobicity requirements. The construction of the inner and outer two-layer hydrophobic coating was beneficial to ensuring the durability of the coating. Even if the topcoat layer was severely abraded and exposed the concrete substrate, the penetration and crystallization effect had already occurred within a certain depth of the surface layer of the concrete, ensuring that the coating could effectively play a hydrophobic role and avoid the entry of water and corrosive ions into the concrete interior to cause adverse effects.

[0101] 3) Surface Micro-Morphology

[0102] The surface micro-morphology and element composition and content of the sample were observed and analyzed by scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS), and the surface micro-morphology of the sample is shown in Figure 3 The uncoated concrete surface has a large number of hydrophilic particle structures, and the main element composition is C, O, Ca, Si, etc., so the liquid droplets fall on the concrete surface and spread and soak immediately. The surface of the comparative example 1 sample coated with the acrylic polyurethane / silane composite protective coating is smooth, and the main element composition is 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 of example 3 is rough, and the main element composition is C, O, Ti, Si, Al, etc., forming a relatively continuous polymer film structure. The polymer film wraps the nanoparticle 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 and reduce the solid-liquid contact area between the coating surface and the water droplets, thereby enhancing the hydrophobicity of the coating. The content of silicon element increases significantly, indicating that the silane and nano-silicon dioxide are successfully introduced on the surface of the coating, and the improvement of the hydrophobicity of the coating is verified.

[0103] 4) Corrosion resistance test

[0104] According to the Technical Code for Corrosion Protection of Concrete Structures in Marine Port Engineering (JTJ 275-2000), the coating concrete should not have bubbling or peeling phenomena after being immersed in saturated Ca(OH)2 solution for 30 days. The test results are shown in Figure 4 During the alkali immersion process, the modified acrylic polyurethane / silane composite protective coating of example 1 can maintain a relatively stable structure, and no internal gas accumulation occurs due to the erosion of the alkali solution, resulting in bubbling and other adverse phenomena on the surface of the coating. After cleaning the surface, the coating is still firmly attached to the substrate, and there is no phenomenon of whole peeling or large-area peeling, but there may be a small amount of coating peeling at some edges or local positions due to mechanical friction during the cleaning process. However, these peeling areas are very small and scattered, and will not have a serious impact on the overall integrity and protective performance of the coating. From the overall analysis, the modified acrylic polyurethane / silane composite protective coating of example 1 with nano-silicon dioxide and silane impregnant has good alkali resistance and stability during the alkali immersion process and after cleaning.

[0105] 5) Self-cleaning performance test

[0106] Selecting nano-silica powder as a representative source of pollution, water flow is continuously applied to the surface of the coating by using a dropper, and the residual condition of the dust on the surface of the coating is observed. The surface of the concrete without coating is hydrophilic, and the water droplet spreads and penetrates into the surface of the test piece as soon as it falls on the surface, and the nano-silica powder is infiltrated and aggregated to form a white stain. On the surface of the modified silane impregnated intermediate layer, the water droplet does not infiltrate, and the water flow can take away most of the powder, but a small amount of powder still remains adhered to the surface and cannot be completely removed. During the test process on the surface of the modified acrylic polyurethane / silane composite protective coating embodiment 1, as shown in the figure, a large amount of powder is taken away by the water flow, and after a period of continuous water flushing, the powder on the surface of the coating can be fully removed, and no obvious residues are observed, indicating that the coating has good self-cleaning performance. Figure 5 As shown in the figure, a large amount of powder is taken away by the water flow, and after a period of continuous water flushing, the powder on the surface of the coating can be fully removed, and no obvious residues are observed, indicating that the coating has good self-cleaning performance.

[0107] 6) Finishing function test

[0108] The brushability, leveling property, re-coatability, film-forming property and the like of the coating of the acrylic polyurethane / silane composite protective coating embodiment are tested. From Figure 6 It can be observed that there are many pore defects on the surface of the blank control concrete without coating, and if the epoxy putty layer is not provided, the modified silane impregnated intermediate layer and the modified acrylic polyurethane top coating cannot effectively close the larger pores on the surface, resulting in uneven coating surface, and the protective function cannot be guaranteed, and the finish is not beautiful. After providing the epoxy putty primer layer, the modified silane impregnated intermediate layer and the modified acrylic polyurethane top coating, the surface of the coating is smooth and flat, and the protective function 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 and wrinkle, has good leveling property, is uniform and flat, has no coating marks, has good re-coatability, is still dense and uniform after multi-layer superposition, does not separate, forms a film quickly, is surface dry within 2h at room temperature (23±2℃), and is real dry within 24h. After the coating is dried, a flat and beautiful finishing layer can be formed, and the coating has good finishing function.

[0109] The above only describes the preferred embodiments of the present application, and is not intended to limit the present application, and any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An acrylic polyurethane / silane hybrid protective coating for concrete surfaces, characterized in that, From bottom to top, it comprises: an epoxy putty layer, a modified silane impregnation intermediate layer and a modified acrylic polyurethane topcoat layer; the epoxy putty layer is obtained by uniformly dispersing silica fume and epoxy resin to obtain an epoxy putty primer, and then applying the epoxy putty primer on the surface of concrete; The raw material components of the modified silane impregnation intermediate layer include, by mass fraction: 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, and 0-5 parts of polyurea; wherein the sum of the amounts of nano-silica and silica sol is greater than 0; The raw material components of the modified acrylic polyurethane topcoat layer include: 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 a silane impregnating agent; wherein the sum of the amounts of nano-silica and silica sol is greater than 0, and the amount of the silane impregnating agent is greater than 0.

2. The acrylic polyurethane / silane hybrid protective coating of claim 1, wherein, The silane impregnating agent is a DC-30 silane impregnating agent.

3. The acrylic polyurethane / silane hybrid protective coating according to claim 1, wherein, The modified silane impregnated interlayer and the modified acrylic polyurethane topcoat are used in an amount of 0.3-0.35 L / m 2 .

4. Process for the preparation of acrylic polyurethane / silane hybrid protective coatings according to any one of claims 1 to 3, characterized in that, The steps include: S1. Preparation of the epoxy putty layer: Silica fume and epoxy resin are uniformly dispersed to obtain an epoxy putty primer, and the epoxy putty primer is applied on the surface of concrete to make the surface flat; S2. Preparation of the modified silane impregnation intermediate layer: 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, and 0-5 parts of polyurea are uniformly mixed to obtain a modified silane impregnating agent, and the modified silane impregnating agent is coated on the epoxy putty layer to form a modified silane impregnation intermediate layer; S3. Preparation of the modified acrylic polyurethane topcoat layer: 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 a silane impregnating agent are uniformly mixed to obtain a modified acrylic polyurethane coating, and the coating is coated on the modified silane impregnation intermediate layer to form a modified acrylic polyurethane topcoat layer.

5. The preparation method according to claim 4, characterized in that, In step S1, it further includes: after application, normal temperature curing and solidification are performed.

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

7. The preparation method according to claim 4, characterized in that, In steps S2 or S3, the coating further includes normal temperature curing and solidification after coating.

8. The preparation method according to claim 4, characterized in that, In steps S2 or S3, the coating is performed 1-3 times.

9. The production method according to claim 8, characterized by, The time interval for single coating is 2-3 h.

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

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