Silicon resin bare concrete coating and preparation method thereof

Abstract

The invention discloses a silicon resin fair-faced concrete coating and a preparation method thereof, and belongs to the technical field of building coatings, the silicon resin fair-faced concrete coating comprises the following components by weight: 25-35 parts of methyl phenyl silicon resin, 10-20 parts of a reactive silane oligomer, 3-8 parts of hydrophobic modified nano alumina, 0.5-1.5 parts of a wetting dispersant, 0.3-0.8 part of an antifoaming agent, 0.2-0.6 part of a leveling agent, and 40-50 parts of a mixed solvent; wherein the reactive silane oligomer is a condensation reaction product of hydroxyl-terminated polydimethylsiloxane and gamma-aminopropyl triethoxy silane, and the reactive silane oligomer is a polymer obtained by carrying out a condensation reaction on hydroxyl-terminated polydimethylsiloxane and gamma-aminopropyl triethoxy silane; the hydrophobic modified nano aluminum oxide is nano particles of which the surfaces are treated by long-chain alkyl silane; the silicon resin fair-faced concrete coating prepared by the invention has excellent comprehensive properties of high adhesive force, super-hydrophobicity, high air permeability and strong weather resistance, and solves the key problems of contradiction between water resistance and air permeability, easiness in blistering and peeling, insufficient durability and the like in the existing fair-faced concrete protective coating.

Description

Technical Field

[0001] This invention belongs to the field of architectural coatings technology, specifically relating to a silicone resin fair-faced concrete coating and its preparation method. Background Technology

[0002] Fair-faced concrete is widely used in construction due to its unique decorative effect. However, its porous structure and chemical composition make it susceptible to erosion from environmental factors such as water, carbon dioxide, chloride ions, and ultraviolet radiation, leading to problems such as carbonation, steel corrosion, and surface weathering. Applying protective coatings is one of the most direct and effective protective measures. Organosilicon resin coatings are considered an ideal choice for protecting fair-faced concrete due to their excellent weather resistance, resistance to high and low temperatures, breathability, and hydrophobicity.

[0003] However, existing silicone resin protective coatings for concrete still have the following shortcomings: Adhesion limitations: The adhesion of ordinary silicone resin coatings to concrete substrates still mainly relies on physical adsorption and limited van der Waals forces. Under humid environments, temperature stress, or long-term exposure, the coating is prone to problems such as decreased adhesion, blistering, or even peeling. The contradiction between penetration and film formation: In order to obtain good protective performance, the coating needs a certain film formation continuity, which often requires the resin to have a high molecular weight; however, high molecular weight resins are difficult to penetrate into the microporous structure of concrete, resulting in limited anchoring effect between the coating and the substrate, and weak strengthening effect on the substrate itself. Balancing hydrophobicity and breathability: While highly hydrophobic coatings can effectively waterproof, they can sometimes excessively hinder the release of moisture from inside the concrete. Maintaining good water vapor permeability of the coating without significantly reducing its hydrophobicity is a technical challenge. Storage stability and workability of coatings: Nanomaterials are often added to silicone resin coatings to improve performance, but nanoparticles are prone to agglomeration, which affects the storage stability, appearance and uniformity of the final coating.

[0004] Therefore, developing a silicone resin-coated fair-faced concrete coating with strong adhesion, excellent hydrophobicity and moderate air permeability, a certain reinforcing effect on the substrate, and stable storage is of great practical significance. Summary of the Invention

[0005] The purpose of this invention is to provide a silicone resin fair-faced concrete coating and its preparation method. Through unique formulation design and step-by-step preparation process, multiple objectives are achieved, such as strong and tough bonding between the coating and the concrete substrate, superhydrophobic surface, internal water vapor permeability, and long-term system stability, thereby solving the problems in the background art.

[0006] The objective of this invention can be achieved through the following technical solutions: A silicone resin-based fair-faced concrete coating comprises the following components in parts by weight: The mixture contains 25-35 parts of methylphenyl silicone resin, 10-20 parts of reactive silane oligomer, 3-8 parts of hydrophobic modified nano-alumina, 0.5-1.5 parts of wetting and dispersing agent, 0.3-0.8 parts of defoamer, 0.2-0.6 parts of leveling agent, and 40-50 parts of mixed solvent. The reactive silane oligomer is a condensation reaction product of hydroxyl-terminated polydimethylsiloxane and γ-aminopropyltriethoxysilane, with a viscosity of 210-480 mPa·s at 25°C; the hydrophobic modified nano-alumina is nanoparticles with an average particle size of 20-50 nm, whose surface has been treated with long-chain alkylsilanes.

[0007] Furthermore, the methylphenyl silicone resin has a phenyl content of 20-30%, a hydroxyl content of 3-6%, and a viscosity of 800-1500 mPa·s at 25°C. As the main film-forming substance, the methylphenyl silicone resin provides the basic framework of the coating, endowing it with good flexibility, weather resistance, and a certain degree of reactivity.

[0008] Furthermore, the reactive silane oligomer is prepared by the following method: Hydroxyl-terminated polydimethylsiloxane and γ-aminopropyltriethoxysilane were mixed at a mass ratio of 1:0.1-0.2 and reacted at 65-75℃ under nitrogen protection for 4-6 hours to obtain an oligomer containing both active siloxane end groups and amino side groups. This oligomer has the following characteristics: relatively low molecular weight and low viscosity, facilitating penetration into the deep capillary pores of concrete; the molecular chain ends retain hydrolyzable siloxane groups, which can undergo condensation reactions with the silanol groups on the concrete surface, achieving chemical anchoring; the side chains contain amino groups, which can form hydrogen bonds or weak chemical crosslinks with the hydroxyl groups in methylphenyl silicone resin or silanol groups generated under the influence of trace amounts of moisture, acting as molecular bridges and greatly enhancing the interfacial bonding between the coating and the concrete matrix.

[0009] Furthermore, the long-chain alkylsilane is dodecyl or hexadecyltrimethoxysilane; the contact angle of the hydrophobic modified nano-alumina is greater than 130°; after the hydrophobic modified nano-alumina is uniformly dispersed in the coating, it can significantly improve the hardness, wear resistance and scratch resistance of the coating; on the other hand, during the coating curing process, the hydrophobic modified nano-alumina tends to accumulate on the coating surface, and in synergy with the low surface energy characteristics of silicone resin, it constructs a superhydrophobic surface with a micro-rough structure, which greatly improves the static water contact angle and the ability to resist liquid water adhesion of the coating; at the same time, the introduction of nanoparticles does not completely block the free volume inside the coating, which is conducive to the diffusion of water vapor molecules and maintains the good air permeability of the coating.

[0010] Furthermore, the mixed solvent is composed of xylene, n-butanol, and propylene glycol methyl ether acetate in a mass ratio of 5:3:2. This mixed solvent system exhibits good solubility for silicone resin and a suitable volatility gradient, which helps to obtain a coating film with good leveling properties and no defects.

[0011] Furthermore, the wetting and dispersing agent is a polyether-modified polydimethylsiloxane; the defoamer is a polyether-modified organosilicon defoamer; and the leveling agent is a polyester-modified organosilicon. The wetting and dispersing agent, defoamer, and leveling agent are all preferably derived from organosilicon additives, exhibiting good compatibility with silicone resin systems and effectively improving the dispersibility of nanoparticles, eliminating bubbles, and enhancing the smoothness of the paint film.

[0012] This invention also provides a method for preparing a silicone resin-coated fair-faced concrete coating, comprising the following steps: S1. Pre-dispersion of nano-slurry: Mix hydrophobic modified nano-alumina with 1 / 3 of the total amount of mixed solvent and wetting and dispersing agent, and ultrasonically disperse at 500-800W for 20-30min to effectively break the agglomeration of nanoparticles and prevent them from settling in the final coating, so as to obtain a uniform and stable nano-slurry. S2. Main resin mixing: Add methylphenyl silicone resin to the remaining mixed solvent and stir to dissolve to obtain a transparent and homogeneous main resin solution; S3. Stepwise mixing and formulation: Add the reactive silane oligomer to the main resin solution and stir at 300-500 rpm for 20 minutes. Then, slowly add the nano slurry while stirring. After the addition is complete, increase the stirring speed to 800-1000 rpm and continue stirring for 40 minutes to ensure that the nanoparticles are uniformly dispersed in the resin system. Finally, add the defoamer and leveling agent, continue stirring for 20 minutes, filter, and obtain the silicone resin fair-faced concrete coating.

[0013] Furthermore, the temperature for ultrasonic dispersion in step S1 is 20-40℃.

[0014] Furthermore, the stirring temperature in step S3 is controlled at 25-35°C to avoid the solvent evaporating too quickly or triggering undesirable side reactions.

[0015] Furthermore, the coating has a solid content of 35.5-44.8% and a viscosity of 155-240 mPa·s at 25°C.

[0016] Beneficial effects of the present invention This invention addresses the challenge of weak adhesion and poor deep penetration of silicone resin coatings to fair-faced concrete by creatively introducing reactive silane oligomers. These oligomers are not simple mixtures, but rather products obtained through a controlled condensation reaction, possessing both small-molecule permeability and dual reactive ends: the siloxane alkyl group at one end chemically bonds to the concrete substrate, while the amino group at the other end strongly interacts with the methylphenyl silicone resin backbone. This bidirectional anchoring mechanism forms a robust chemical-physical interface between the coating and the substrate, significantly improving adhesion and making the coating less prone to blistering and peeling. The use of hydrophobic modified nano-alumina instead of other nanomaterials in this invention is the result of careful consideration. Its rigid core effectively enhances the coating's hardness and wear resistance, while its surface contains long-chain alkyl groups after silanization treatment, exhibiting excellent compatibility with silicone resin and ensuring nanoscale dispersion. More importantly, during the coating curing process, these low surface energy hydrophobic modified nano-alumina spontaneously migrate and accumulate at the coating-air interface. This behavior, in synergy with the silicone resin itself, is not a simple mixing but rather a dynamic construction of a stable hydrophobic surface with a micro-nano composite rough structure. Simultaneously, due to the interaction between the nanoparticles and the resin interface, the free volume network of polymer segments is not completely blocked, thus achieving hydrophobicity while retaining nanoscale channels for water vapor molecule diffusion, cleverly resolving the traditional contradiction between hydrophobicity and air permeability. The preparation method of this invention is not a simple component mixing. In step S1, the nano-alumina undergoes high-intensity ultrasonic pre-dispersion, which is a prerequisite for ensuring its uniform dispersion at the nanoscale in the resin, preventing agglomeration, and thus enhancing and constructing the surface structure. In step S3, the reactive silane oligomer is first mixed with the main resin solution, followed by high-speed dispersion of the nano-slurry. This sequence facilitates the pre-binding of the oligomer with the resin and ensures that the nanoparticles remain uniformly dispersed in the already thickened system. Stepwise mixing is essential to achieving the ideal synergistic state of the above components and ultimately obtaining a coating with excellent comprehensive performance. The optimized solvent system and additives give the coating suitable viscosity, leveling, and defoaming properties, facilitating storage and application. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1 This embodiment provides a reactive silane oligomer, prepared through the following steps: In a 250 mL four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet, 100 g of hydroxyl-terminated polydimethylsiloxane (viscosity approximately 100 mPa·s, hydroxyl content approximately 4.5%) and 10 g of γ-aminopropyltriethoxysilane were added. Nitrogen gas was introduced to purge the air three times. The mixture was then heated to 65 °C under nitrogen protection, stirred, and maintained at this temperature for 4 hours. After the reaction was complete, a light yellow, transparent, viscous liquid reactive silane oligomer was obtained. The viscosity of the product at 25 °C was measured to be 210 mPa·s.

[0019] Infrared spectroscopy analysis was performed on the sample: the hydroxyl-terminated polydimethylsiloxane of the raw material was analyzed at 3400 cm⁻ 1 The broad and strong OH stretching vibration peak in the vicinity was significantly weakened, indicating that the hydroxyl group participated in the reaction; at 3300 cm⁻ 1 and 1600cm⁻ 1 The presence of distinct shoulder peaks / weak peaks nearby, attributed to NH stretching and bending vibrations respectively, confirms the introduction of amino groups into KH-550, and this is observed at 1100 cm⁻¹. 1 The enhanced and broadened Si-O-Si stretching vibration peaks in the vicinity indicate the formation of new Si-O-Si bonds and the generation of the target oligomer; at 1080 cm⁻ 1 and 960cm⁻ 1 The presence of a weak absorption attributed to Si-O-C2H5 nearby indicates that some ethoxy groups have not yet fully reacted or hydrolyzed.

[0020] Example 2 This embodiment provides a reactive silane oligomer, prepared through the following steps: In a 250 mL four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet, 100 g of hydroxyl-terminated polydimethylsiloxane (viscosity approximately 150 mPa·s, hydroxyl content approximately 5%) and 15 g of γ-aminopropyltriethoxysilane were added. Nitrogen gas was introduced to purge the air three times. The mixture was then heated to 70 °C under nitrogen protection, stirred, and maintained at this temperature for 5 hours. After the reaction was complete, a light yellow, transparent, viscous liquid reactive silane oligomer was obtained. The viscosity of the product at 25 °C was measured to be 320 mPa·s.

[0021] Infrared spectroscopy analysis was performed on the sample: the hydroxyl-terminated polydimethylsiloxane of the raw material was analyzed at 3400 cm⁻ 1 The broad and strong OH stretching vibration peak in the vicinity was significantly weakened, indicating that the hydroxyl group participated in the reaction; at 3300 cm⁻ 1 and 1600cm⁻ 1 The presence of NH characteristic peaks nearby confirms the introduction of amino groups from KH-550; at 1100 cm⁻ 1The strong and broad Si-O-Si absorption peaks nearby indicate the formation of new Si-O-Si bonds and the generation of the target oligomer; at 1080 cm⁻ 1 and 960cm⁻ 1 The presence of a characteristic Si-O-C2H5 peak nearby indicates that some of the ethoxy groups have been reacted or hydrolyzed.

[0022] Example 3 This embodiment provides a reactive silane oligomer, prepared through the following steps: In a 250 mL four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet, 100 g of hydroxyl-terminated polydimethylsiloxane (viscosity approximately 200 mPa·s, hydroxyl content approximately 5.5%) and 20 g of γ-aminopropyltriethoxysilane were added. Nitrogen gas was introduced to purge the air three times. The mixture was then heated to 75 °C under nitrogen protection, stirred, and maintained at this temperature for 6 hours. After the reaction was complete, an amber-colored, transparent, viscous liquid reactive silane oligomer was obtained. The viscosity of the product at 25 °C was measured to be 480 mPa·s.

[0023] Infrared spectroscopy analysis was performed on the sample: the hydroxyl-terminated polydimethylsiloxane of the raw material was analyzed at 3400 cm⁻ 1 The nearby OH stretching vibration peak becomes very weak, indicating that the hydroxyl group reaction is more complete; at 3300 cm⁻ 1 and 1600cm⁻ 1 The higher intensity of the NH characteristic peak in the vicinity indicates a higher content of grafted amino groups in the product; at 1100 cm⁻¹ 1 The nearby Si-O-Si absorption peaks are very strong and broad, indicating the formation of a more developed cross-linked network structure; at 1080 cm⁻¹ 1 and 960cm⁻ 1 The characteristic peak of Si-O-C2H5 in the vicinity is very weak, indicating that most of the ethoxy group has participated in the reaction or hydrolysis and condensation.

[0024] Example 4 This embodiment provides a hydrophobic modified nano-alumina, prepared by the following method: 100g of γ-alumina powder with an average particle size of 20nm was dispersed in 500mL of anhydrous ethanol and pre-dispersed by ultrasonication at 500W for 30min. Then, 18g of dodecyltrimethoxysilane and 1.8g of glacial acetic acid were added, and the mixture was refluxed and stirred at 78℃ for 5h. After the reaction, the solid was separated by centrifugation, washed three times with ethanol, and then dried in a vacuum drying oven at 80℃ for 10h to obtain a white powdery hydrophobic modified nano-alumina. The contact angle of the compressed tablet was measured to be 132° using a water contact angle tester.

[0025] Example 5 This embodiment provides a hydrophobic modified nano-alumina, prepared by the following method: 100g of γ-alumina powder with an average particle size of 30nm was dispersed in 500mL of anhydrous ethanol and pre-dispersed by ultrasonication at 500W for 40min. Then, 20g of hexadecyltrimethoxysilane and 2g of glacial acetic acid were added, and the mixture was refluxed and stirred at 80℃ for 6h. After the reaction was completed, the solid was separated by centrifugation, washed three times with ethanol, and then dried in a vacuum drying oven at 80℃ for 11h to obtain a white powdery hydrophobic modified nano-alumina. The contact angle of the compressed tablet was measured to be 138° using a water contact angle meter.

[0026] Example 6 This embodiment provides a hydrophobic modified nano-alumina, prepared by the following method: 100g of γ-alumina powder with an average particle size of 50nm was dispersed in 500mL of anhydrous ethanol and ultrasonically pre-dispersed at 500W for 30min. Then, 22g of hexadecyltrimethoxysilane and 2.1g of glacial acetic acid were added, and the mixture was refluxed and stirred at 85℃ for 7h. After the reaction, the solid was separated by centrifugation, washed three times with ethanol, and then dried in a vacuum drying oven at 80℃ for 12h to obtain a white powdery hydrophobic modified nano-alumina. The contact angle of the compressed tablet was measured to be 142° using a water contact angle tester.

[0027] Example 7 This embodiment provides a silicone resin-based fair-faced concrete coating, comprising the following components in parts by weight: Methylphenyl silicone resin: 20% phenyl, 3% hydroxyl, viscosity 800 mPa·s, 25 parts 20 parts of the reactive silane oligomer prepared in Example 1 Three parts of hydrophobic modified nano-alumina prepared in Example 4 Wetting and dispersing agent: Polyether-modified polydimethylsiloxane, BYK-307, 0.5 parts Defoamer: Polyether-modified silicone defoamer, TEGO Foamex 810, 0.3 parts Leveling agent: Polyester-modified organosiloxane, BYK-333, 0.2 parts Mixed solvent: xylene: n-butanol: PMA = 5:3:2 50 parts; This type of silicone resin-based fair-faced concrete coating is prepared by the following method: S1. Mix the hydrophobic modified nano alumina with 1 / 3 of the total amount of mixed solvent and wetting and dispersing agent, and ultrasonically disperse at 20℃ and 500W for 30 min to obtain a uniform and stable nano slurry. S2. Add methylphenyl silicone resin to the remaining mixed solvent and stir at 500 rpm to dissolve, obtaining a transparent and homogeneous main resin solution. S3. Add the reactive silane oligomer to the main resin solution and stir at 300 rpm for 20 min at 25°C. Then, slowly add the nano-slurry while stirring. After the addition is complete, increase the stirring speed to 800 rpm and continue stirring for 40 min. Finally, add the defoamer and leveling agent, and continue stirring for 20 min. Filter to obtain the silicone resin fair-faced concrete coating. Its solid content is tested to be 35.5%, and its viscosity at 25°C is 155 mPa·s.

[0028] Example 8 This embodiment provides a silicone resin-based fair-faced concrete coating, comprising the following components in parts by weight: Methylphenyl silicone resin: 25% phenyl, 4% hydroxyl, viscosity 1200 mPa·s, 30 parts 15 parts of the reactive silane oligomer prepared in Example 2 Five parts of hydrophobic modified nano-alumina prepared in Example 5 Wetting and dispersing agent: Polyether-modified polydimethylsiloxane, BYK-307, 1 part Defoamer: Polyether-modified silicone defoamer, TEGO Foamex 810, 0.5 parts Leveling agent: Polyester-modified organosiloxane, BYK-333, 0.4 parts Mixed solvent: xylene: n-butanol: PMA = 5:3:2 45 parts; This type of silicone resin-based fair-faced concrete coating is prepared by the following method: S1. The hydrophobic modified nano-alumina was mixed with 1 / 3 of the total amount of mixed solvent and wetting and dispersing agent, and ultrasonically dispersed at 30℃ and 650W for 25 min to obtain a uniform and stable nano slurry. S2. Add methylphenyl silicone resin to the remaining mixed solvent and stir at 500 rpm to dissolve and obtain a transparent and homogeneous main resin solution.

[0029] S3. Add the reactive silane oligomer to the main resin solution and stir at 400 rpm for 20 min at 30°C. Then, slowly add the nano-slurry while stirring. After the addition is complete, increase the stirring speed to 900 rpm and continue stirring for 40 min to ensure that the nanoparticles are uniformly dispersed in the resin system. Finally, add the defoamer and leveling agent, and continue stirring for 20 min. Filter to obtain the silicone resin fair-faced concrete coating. Its solid content is tested to be 38.2%, and its viscosity at 25°C is 180 mPa·s.

[0030] Example 9 This embodiment provides a silicone resin-based fair-faced concrete coating, comprising the following components in parts by weight: Methylphenyl silicone resin: 30% phenyl, 6% hydroxyl, viscosity 1500 mPa·s, 35 parts 10 parts of the reactive silane oligomer prepared in Example 3 Eight parts of hydrophobic modified nano-alumina prepared in Example 6 Wetting and dispersing agent: Polyether-modified polydimethylsiloxane, BYK-307, 1.5 parts Defoamer: Polyether-modified silicone defoamer, TEGO Foamex 810, 0.8 parts Leveling agent: Polyester-modified organosiloxane, BYK-333, 0.6 parts Mixed solvent: xylene: n-butanol: PMA = 5:3:2 40 parts; This type of silicone resin-based fair-faced concrete coating is prepared by the following method: S1. Mix the hydrophobic modified nano alumina with 1 / 3 of the total amount of mixed solvent and wetting and dispersing agent, and ultrasonically disperse at 40℃ and 800W for 20min to obtain a uniform and stable nano slurry. S2. Add methylphenyl silicone resin to the remaining mixed solvent and stir at 500 rpm to dissolve and obtain a transparent and homogeneous main resin solution.

[0031] S3. Add the reactive silane oligomer to the main resin solution and stir at 500 rpm for 20 minutes at 35°C. Then, slowly add the nano-slurry while stirring. After the addition is complete, increase the stirring speed to 1000 rpm and continue stirring for 40 minutes. Finally, add the defoamer and leveling agent, and continue stirring for 20 minutes. Filter to obtain the silicone resin fair-faced concrete coating. Its solid content is tested to be 44.8%, and its viscosity at 25°C is 240 mPa·s.

[0032] Comparative Example 1 The difference between this comparative example and Example 8 is that the reactive silane oligomer obtained in Example 2 is replaced with an equal amount of methylphenyl silicone resin, while the other raw materials and steps are the same.

[0033] Comparative Example 2 The difference between this comparative example and Example 8 is that the hydrophobic modified nano-alumina obtained in Example 5 was replaced in equal amounts with untreated nano-alumina of the same specifications (contact angle of about 20°), while the other raw materials and steps were the same.

[0034] Comparative Example 3 This comparative example is a commercially available water-based silicone-acrylic (organosilicon-acrylic) concrete protective transparent topcoat.

[0035] The coatings from Examples 7-9 and Comparative Examples 1-3 were applied to the surface of a standard cement mortar slab (150mm×70mm×20mm) in two coats, with a 6-hour interval between coats. The total dry film thickness was controlled at 50±5μm. After curing at 25℃ and 50±5%RH for 7 days, performance tests were conducted. Coating storage stability: Seal the coating and place it in a 50℃ constant temperature oven. After 30 days, observe whether there is sedimentation, clumping, gelation or other phenomena. Water contact angle: Using an optical contact angle meter, 5 μL of deionized water was dropped at 5 different locations randomly selected on the coating surface, the static contact angle was measured, and the average value was taken; Adhesion: In accordance with GB / T 5210-2006 standard, a portable adhesion tester was used with a loading rate of 1.0 MPa / s to record the failure strength and observe the failure mode; Water vapor transmission rate: Tested according to the desiccant method of GB / T 17146-2015 standard, under the conditions of 23℃ and relative humidity gradient of 50% / 0%; Water absorption rate: The coated test panel was completely immersed in deionized water for 24 hours. After being taken out, the surface moisture was quickly absorbed with filter paper, and the weight was weighed to calculate the percentage increase in mass. Water resistance: According to GB / T 1733-1993 standard, the test panel was immersed in deionized water at 25℃ for 300 hours, and the coating was observed to see if it blistered, turned white, wrinkled or peeled off. Alkali resistance: In accordance with GB / T 9265-2009 standard, the test plate was immersed in a saturated Ca(OH)2 solution at 25℃ for 168 hours, and the coating changes were observed. Pencil hardness: Tested according to GB / T 6739-2022 standard; Artificial climate aging: Following GB / T 1865-2009 standard, a xenon lamp aging test chamber was used with an irradiance of 0.51 W / m². 2 The blackboard temperature was 65℃, the relative humidity was 50%, and the continuous light exposure was not sprayed. After 500 hours of testing, the color difference was measured using a colorimeter.

[0036] The results are shown in Table 1: Table 1 As shown in Table 1, the coatings prepared in Examples 7-9 exhibit good storage stability, indicating that the pre-dispersion and stepwise mixing of the nano-slurry effectively prevent nanoparticle aggregation and sedimentation. Comparative Example 2, due to the use of unmodified nano-alumina, suffers from poor compatibility between the particles and the resin, leading to severe stratification, thus demonstrating the necessity of surface hydrophobic modification. The adhesion of Examples 7-9 is significantly higher than all comparative examples, indicating high bonding strength between the coating and the substrate. Comparative Example 1 has the lowest adhesion, strongly demonstrating the key role of reactive silane oligomers: their small molecular structure penetrates into the substrate capillaries, the terminal siloxane groups react and anchor with the substrate, and the side-chain amino groups interact with the main resin, forming a robust resin-oligomer-matrix interpenetrating network. The water contact angle of Examples 7-9 all exceeds 148°, mainly due to the inherent low surface energy of methylphenyl silicone resin and the micro-rough structure constructed on the coating surface by the hydrophobic modified nano-alumina. Comparative Example 2... The antenna angle of only 98° demonstrates the decisive role of hydrophobic modification on the surface of nanomaterials. Examples 7-9 maintain high hydrophobicity while exhibiting higher water vapor permeability and extremely low water absorption. This is due to the resin molecular structure (phenyl groups hinder close packing and create free volume) and uniformly dispersed nanoparticles (forming tortuous but unobstructed hydrophobic microporous channels), allowing water vapor to pass through while blocking liquid water. Examples 7-9 performed excellently in water and alkali resistance tests, while the comparative examples showed varying degrees of damage. Comparative example 2 was severely damaged in an alkaline environment, indicating that unmodified hydrophilic nanoparticles introduce weaknesses in water vapor permeability and accelerate coating failure. Examples 7-9 showed minimal color difference after artificial aging, demonstrating excellent resistance to ultraviolet aging. This is attributed to the absorption of ultraviolet light by phenyl groups and the inherent stability of silicon-oxygen bonds. The addition of hydrophobic modified nano-alumina significantly improved the coating hardness and enhanced its wear resistance and scratch resistance.

[0037] In summary, reactive silane oligomers solve the fundamental problem of insufficient adhesion between traditional silicone resin coatings and concrete, achieving strong and tough chemical anchoring. Hydrophobic modified nano-alumina synergizes with the resin to construct a stable superhydrophobic surface and enhances the mechanical properties of the coating. The optimized stepwise preparation process ensures uniform dispersion of each component and system stability. These three factors work synergistically to give the coating of this invention excellent comprehensive properties, including high adhesion, superhydrophobicity, high breathability, and strong weather resistance, solving key problems in existing technologies such as the contradiction between waterproofing and breathability, easy blistering and peeling, and insufficient durability.

[0038] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0039] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A silicone resin-coated fair-faced concrete coating, characterized in that, Includes the following components by weight: The mixture contains 25-35 parts of methylphenyl silicone resin, 10-20 parts of reactive silane oligomer, 3-8 parts of hydrophobic modified nano-alumina, 0.5-1.5 parts of wetting and dispersing agent, 0.3-0.8 parts of defoamer, 0.2-0.6 parts of leveling agent, and 40-50 parts of mixed solvent. The reactive silane oligomer is a condensation reaction product of hydroxyl-terminated polydimethylsiloxane and γ-aminopropyltriethoxysilane, with a viscosity of 210-480 mPa·s at 25°C; the hydrophobic modified nano-alumina is nanoparticles with an average particle size of 20-50 nm, whose surface has been treated with long-chain alkylsilanes.

2. The silicone resin fair-faced concrete coating according to claim 1, characterized in that, The methylphenyl silicone resin has a phenyl content of 20-30%, a hydroxyl content of 3-6%, and a viscosity of 800-1500 mPa·s at 25°C.

3. The silicone resin fair-faced concrete coating according to claim 1, characterized in that, The reactive silane oligomers are prepared by the following method: Hydroxyl-terminated polydimethylsiloxane and γ-aminopropyltriethoxysilane were mixed at a mass ratio of 1:0.1-0.2 and reacted at 65-75℃ under nitrogen protection for 4-6 hours to obtain reactive silane oligomers.

4. The silicone resin fair-faced concrete coating according to claim 1, characterized in that, The long-chain alkylsilane is dodecyl or hexadecyltrimethoxysilane; the contact angle of the hydrophobic modified nano-alumina is greater than 130°.

5. The silicone resin fair-faced concrete coating according to claim 1, characterized in that, The mixed solvent is composed of xylene, n-butanol and propylene glycol methyl ether acetate in a mass ratio of 5:3:

2.

6. The silicone resin fair-faced concrete coating according to claim 1, characterized in that, The wetting and dispersing agent is polyether-modified polydimethylsiloxane; the defoamer is polyether-modified organosilicon defoamer; and the leveling agent is polyester-modified organosilicon.

7. The method for preparing a silicone resin-coated fair-faced concrete coating according to claim 1, characterized in that, Includes the following steps: S1. Mix the hydrophobic modified nano-alumina with 1 / 3 of the total amount of mixed solvent and wetting and dispersing agent, and then ultrasonically disperse it evenly to obtain a nano slurry; S2. Add methylphenyl silicone resin to the remaining mixed solvent and stir to dissolve, to obtain the main resin solution; S3. Add the reactive silane oligomer to the main resin solution and stir at low speed until uniform. Then slowly add the nano slurry. After the addition is complete, increase the stirring speed to high speed and stir until uniform. Finally, add the defoamer and leveling agent, continue stirring until uniform, and filter to obtain the silicone resin fair-faced concrete coating.

8. The method for preparing a silicone resin-coated fair-faced concrete coating according to claim 7, characterized in that, The temperature for ultrasonic dispersion is 20-40℃.

9. The method for preparing a silicone resin-coated fair-faced concrete coating according to claim 7, characterized in that, The low-speed stirring is 300-500 rpm; the high-speed stirring is 800-1000 rpm; and the stirring temperature is 25-35℃.

10. The method for preparing a silicone resin-coated fair-faced concrete coating according to claim 7, characterized in that, The coating has a solid content of 35.5-44.8% and a viscosity of 155-240 mPa·s at 25°C.

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