Long-acting anti-aging protective coating for masonry base material as well as preparation method and application of long-acting anti-aging protective coating

Abstract

The invention discloses a masonry base material long-acting anti-aging protective coating as well as a preparation method and application thereof, and belongs to the technical field of building material protection. The protective coating is composed of a bottom layer and a surface layer, the bottom layer takes modified silica sol and water-soluble epoxy resin as main film forming substances, and is matched with nano aluminum oxide, a silane coupling agent and the like; the surface layer takes fluorocarbon resin as a main film forming substance, and is compounded with nano titanium dioxide, nano zinc oxide, polytetrafluoroethylene micro powder and the like. The preparation method comprises the steps of bottom layer preparation, surface layer preparation and coating, and uniform dispersion and sufficient curing of all components are achieved through specific process parameter control. The composite coating structure is adopted, the adhesive force between the bottom layer and a masonry base material is high, and harmful substances can be effectively prevented from invading; the surface layer is excellent in ultraviolet resistance, weather resistance, hydrophobicity and antifouling property. Tests show that the outdoor effective anti-aging period of the protective coating can reach 8-10 years, the service life of the stone is remarkably prolonged, the maintenance cost is reduced, and the protective coating is suitable for various masonry base materials.

Description

Technical Field

[0001] This invention relates to the field of building material protection technology, specifically to a long-lasting anti-aging protective coating for masonry substrates, its preparation method, and its application. Background Technology

[0002] Masonry materials (including concrete blocks, sintered bricks, and ancient building bricks) are widely used in building exteriors, municipal bridges, and stone carvings due to their stable mechanical properties (compressive strength 20-150MPa), easy availability, and unique cultural attributes.

[0003] Masonry substrates account for over 40% of applications in outdoor and exposed environments. However, their porous structure (porosity 10%-35%) and hydrophilic mineral components (such as montmorillonite and calcite) make them highly susceptible to aging and deterioration caused by natural environmental factors, such as UV aging, thermo-oxidative aging, wet aging, and chemical aging. These aging problems not only shorten the service life of masonry substrates but also lead to a surge in building maintenance costs (annual maintenance costs account for 5%-8% of the total building cost) and pose a serious threat to the integrity of masonry cultural relics (the surface damage rate of masonry cultural relics due to aging reaches 5%-8% annually, and the surface peeling rate of some sandstone grottoes has reached 0.1-0.5 mm / year).

[0004] To address the aging problem of masonry substrates, surface protective coatings have become the mainstream technology. However, existing coatings have significant shortcomings in long-term anti-aging performance and overall compatibility, making it difficult to meet industry demands. Traditional anti-aging coating technologies have major limitations. Organic anti-aging coatings, based on acrylates and polyurethanes, although containing UV absorbers (such as UV-531) and antioxidants (such as 1010), suffer from obvious drawbacks such as short anti-aging lifespan, poor compatibility, and unbalanced permeability. Inorganic anti-aging coatings have weak mechanical properties and limited application options.

[0005] Therefore, developing a long-lasting anti-aging protective coating that has strong adhesion to masonry substrates, excellent UV resistance, weather resistance, corrosion resistance, hydrophobicity and stain resistance, and a long service life has become an urgent technical problem to be solved in the field of stone protection. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing anti-aging protective coatings for bricks and stones, such as insufficient adhesion, short anti-aging period, and poor overall performance, and to provide a long-lasting anti-aging protective coating for brick and stone substrates and its preparation method. This protective coating bonds tightly to bricks and stones, effectively resisting erosion from complex outdoor environments, significantly extending the service life and aesthetic lifespan of the stone. Furthermore, the preparation method is process-controllable and easily industrialized, and the resulting coating can be widely used for the protection of outdoor bricks and stones.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A long-lasting anti-aging protective coating for masonry substrates, comprising a base layer and a top layer, wherein the raw material composition of each layer is as follows by weight:

[0009] Base layer: Modified silica sol: 40-60 parts; Nano alumina: 5-10 parts; Silane coupling agent: 3-8 parts; Water-soluble epoxy resin: 10-15 parts; Curing agent: 2-5 parts; Dispersant: 1-3 parts; Deionized water: 15-25 parts.

[0010] Topcoat: Fluorocarbon resin: 30-50 parts; Nano titanium dioxide: 3-8 parts; Nano zinc oxide: 2-5 parts; Polytetrafluoroethylene micro powder: 1-4 parts; Plasticizer: 2-5 parts; Leveling agent: 1-2 parts; Solvent: 20-35 parts.

[0011] Further, the modified silica sol comprises:

[0012] The modified silica sol is a methyltrimethoxysilane-modified silica sol with a particle size strictly controlled within the range of 20-50 nm and a solid content of 30-40%. Modification with methyltrimethoxysilane effectively improves the stability of the silica sol in the system, while enhancing its compatibility with water-soluble epoxy resins and other organic components, thereby strengthening the chemical bonding between the substrate and the masonry / stone base and improving adhesion.

[0013] Furthermore, the nano-alumina has a particle size of 10-30 nm, which can be uniformly dispersed in the substrate and fill the coating pores, significantly improving the mechanical strength and wear resistance of the substrate.

[0014] Furthermore, the nano-titanium dioxide is anatase type with a particle size of 5-20 nm. The anatase structure endows it with excellent photocatalytic activity, which can degrade organic pollutants attached to the coating surface and achieve self-cleaning function.

[0015] Furthermore, the nano zinc oxide has a particle size of 10-25 nm, and works synergistically with nano titanium dioxide to broaden the ultraviolet absorption range and significantly improve the UV aging resistance of the surface layer.

[0016] Furthermore, the polytetrafluoroethylene micropowder has a particle size of 1-5 μm, which can form a low surface energy structure on the surface layer, significantly enhancing the hydrophobicity and antifouling properties of the coating.

[0017] Furthermore, the silane coupling agent is selected from γ-aminopropyltriethoxysilane (KH550) or γ-glycidoxypropyltrimethoxysilane (KH560). The amino group of KH550 can react with the epoxy group of water-soluble epoxy resin, while the epoxy group of KH560 can crosslink with the hydroxyl groups on the stone surface and the epoxy resin. Both coupling agents can construct a "chemical bridge" between the stone and the substrate, significantly improving interfacial adhesion.

[0018] Furthermore, the epoxy value of the water-soluble epoxy resin is 0.4-0.6 eq / 100g, which ensures that it forms a dense cross-linked network with the polyamide curing agent; the curing agent is a polyamide curing agent, which has good compatibility with the water-soluble epoxy resin, and the curing process is mild, avoiding internal stress cracking of the coating due to excessively fast curing speed. 5. Additives and Solvents:

[0019] Furthermore, the dispersant is a polycarboxylate dispersant, which has excellent dispersing effect on nano-fillers such as nano-alumina and nano-titanium dioxide, and can effectively prevent the agglomeration of nanoparticles and ensure uniform coating performance.

[0020] Furthermore, the plasticizer is dibutyl phthalate, which can improve the flexibility of fluorocarbon resin, reduce the brittleness of the coating, and enhance its impact resistance and resistance to thermal cycling.

[0021] Furthermore, the leveling agent is polyether-modified polydimethylsiloxane, which can reduce the surface tension of the coating, improve the leveling properties during the coating process, and avoid appearance defects such as pinholes, orange peel, and pores.

[0022] Furthermore, the solvent is a mixture of ethyl acetate and xylene in a weight ratio of 1:1-2. This mixture can adjust the evaporation rate of the solvent, ensuring that the surface layer is uniformly leveled and fully cured after coating, while ensuring good dissolution and dispersion of fluorocarbon resin and various fillers.

[0023] A method for preparing a long-lasting anti-aging protective coating for masonry substrates, comprising three steps: primer preparation, topcoat preparation, and coating application. Specific process parameters and operating procedures are as follows:

[0024] 1. The preparation of the underlying layer includes:

[0025] 1.1 Preparation of Mixture A: Accurately weigh the modified silica sol and deionized water according to the weight proportions, add them to the stirred tank equipped with a stirring device, set the stirring speed to 300-500 r / min, and continue stirring for 10-15 min to fully mix the two and form a uniform mixture A;

[0026] 1.2 Preparation of Mixture B: Add nano-alumina and dispersant sequentially to mixture A, increase the stirring speed to 800-1000 r / min, and stir at high speed for 30-40 min. At the same time, turn on the ultrasonic dispersion device, set the ultrasonic power to 300-500 W, and the dispersion time to 20-30 min. Through the synergistic effect of high-speed stirring and ultrasonic dispersion, the nano-alumina is uniformly dispersed to obtain mixture B.

[0027] 1.3 Preparation of Mixture C: Reduce the stirring speed to 400-600 r / min, add silane coupling agent to mixture B, and stir for 15-20 min to allow the coupling agent to be fully dispersed and initially react with the components in the system; then add water-soluble epoxy resin and continue stirring for 20-30 min to ensure that the epoxy resin is uniformly mixed with other components to obtain mixture C;

[0028] 1.4 Preparation of the base coat: Finally, add polyamide curing agent to the mixture C, adjust the stirring speed to 300-500 r / min, stir for 15-20 min, then stop stirring and let the mixture stand for 10-15 min to remove bubbles from the system, thus obtaining a uniform and stable base coat.

[0029] 2. Preparation of the surface layer, including:

[0030] 2.1 Preparation of Mixture D: Accurately weigh the fluorocarbon resin and ethyl acetate-xylene mixed solvent according to the weight proportions, add them to the stirred tank, set the stirring speed to 400-600 r / min, and stir for 20-30 min to completely dissolve the fluorocarbon resin in the mixed solvent to form a clear and transparent mixture D;

[0031] 2.2 Preparation of Mixture E: Nano-titanium dioxide, nano-zinc oxide, and polytetrafluoroethylene (PTFE) powder were added sequentially to mixture D. The stirring speed was increased to 1000-1200 r / min, and high-speed stirring was carried out for 40-50 min. Simultaneously, the ultrasonic dispersion device was turned on, and the ultrasonic power was set to 400-600 W for a dispersion time of 30-40 min to ensure that all nanofillers and powders were uniformly dispersed in the fluorocarbon resin system without agglomeration, thus obtaining mixture E.

[0032] 2.3 Preparation of topcoat: Reduce the stirring speed to 300-500 r / min, add dibutyl phthalate plasticizer and polyether modified polydimethylsiloxane leveling agent to mixture E, and continue stirring for 20-30 min to fully disperse the additives; after stirring, let stand for 15-20 min to remove bubbles in the system and obtain a uniform topcoat.

[0033] 3. Coating application, including:

[0034] 3.1 Pre-treatment of brick and stone: First, use high-pressure air blowing or brush cleaning to remove dust, slag and other impurities from the surface of the brick and stone. For oil stains on the surface, wipe them off with ethanol or acetone. Then, use 80-120 grit sandpaper to roughen the surface of the stone and increase the surface area. After grinding, rinse the surface of the stone with deionized water until there is no dust residue. Place the stone in an oven at 60-80℃ for 2-3 hours to dry completely remove the moisture inside and on the surface of the stone. After removing it, let it cool naturally to room temperature.

[0035] 3.2 Primer Coating and Curing: Apply the primer coating evenly to the pretreated brick and stone surface by spraying or brushing, controlling the coating thickness to be 30-50μm; after coating, place at room temperature for 1-2 hours to allow the coating to initially level and some moisture to evaporate; then place the stone in an oven at 80-100℃ for 2-3 hours to cure, allowing the water-soluble epoxy resin and hardener to fully react and form a dense primer film;

[0036] 3.3 Topcoat Coating and Curing: After the base layer has fully cured and cooled naturally to room temperature, the topcoat coating is evenly applied to the base layer surface using a spraying method (spraying pressure controlled at 0.3-0.5MPa, spray gun distance 20-30cm from the stone surface), with a coating thickness of 20-40μm. After coating, the surface is allowed to level at room temperature for 1-1.5h to allow the solvent to evaporate slowly and avoid pinholes in the coating. Then, the stone is placed in an oven at 120-150℃ for curing for 1.5-2.5h to allow the fluorocarbon resin to fully crosslink and cure. After naturally cooling to room temperature, a complete long-lasting anti-aging protective coating is formed.

[0037] An application of a long-lasting anti-aging protective coating for masonry substrates is disclosed. This coating can be widely used for the protection of outdoor masonry and stone materials. The protective coating is suitable for various types of outdoor masonry and stone materials, including plaza paving stones, landscape sculptures, curb stones, artificial rock formations, and building facade decorative stones, without being limited by the specifications or shape of the stone.

[0038] The beneficial effects of this invention are:

[0039] 1. Synergistic Effect of Composite Structure: This invention adopts a composite structure of bottom and top layers. The bottom layer, through the synergistic effect of modified silica sol, water-soluble epoxy resin, and silane coupling agent, forms a strong chemical bond with the brick and stone material, achieving an adhesion level of Grade 1 (tested according to GB / T 9286-1998). Simultaneously, it forms a dense barrier, effectively preventing harmful substances such as moisture, acid rain, and salt spray from penetrating the stone. The top layer uses fluorocarbon resin as a matrix, compounded with nano-titanium dioxide, nano-zinc oxide, and polytetrafluoroethylene micropowder. It exhibits excellent resistance to ultraviolet aging (gloss loss rate less than 10% after 1000h QUV aging test), weather resistance, hydrophobicity (contact angle greater than 110°), and stain resistance, achieving a synergistic effect of "strong adhesion of the bottom layer and strong protection of the top layer."

[0040] 2. Enhanced Nanofiller Performance: Through the combined action of polycarboxylate dispersant and ultrasonic-assisted dispersion, nanofillers such as nano-alumina and nano-titanium dioxide are uniformly dispersed in the coating, fully leveraging the nano-effect. Specifically, nano-alumina increases the compressive strength of the underlying layer by 25%-35%, while nano-titanium dioxide and nano-zinc oxide synergistically achieve a UV shielding rate of over 95% on the surface layer. Polytetrafluoroethylene (PTFE) micropowder significantly reduces the surface energy of the coating, endowing it with excellent self-cleaning properties and reducing contaminant adhesion by over 80%.

[0041] 3. Controllable process and long-lasting durability: The preparation method of this invention has clear and controllable process parameters for each step, making it suitable for industrial mass production; the coating is fully cured after application and has a tight bond with the stone. As verified by simulated outdoor exposure tests, its effective anti-aging period can reach 8-10 years, which is much longer than the 3-5 year period of existing protective coatings. This can significantly reduce the maintenance frequency and cost of outdoor brick and stone materials and extend the service life and aesthetic period of the stone.

[0042] 4. Wide range of applications: The protective coating of this invention is suitable for various outdoor brick and stone materials, including plaza paving stones, landscape sculptures, curb stones, artificial rock stones, and building facade decorative stones, etc. It is not limited by the specifications and shape of the stone and has good practicality and promotional value.

[0043] Specific Implementation Cases

[0044] To objectively and quantitatively evaluate the overall performance of the protective coating prepared by this invention, the following standardized tests were performed on all examples and comparative coating samples. The specific test methods are as follows:

[0045] 1. Adhesion test

[0046] Test standard: GB / T 9286-1998 "Cross-cut test for paint and varnish films"

[0047] Test Method: Using a crisscross cutter with a blade spacing of 1mm, cut six evenly spaced parallel cuts into the coating surface, extending to the substrate. Then rotate the cutter 90° and cut the same number of cuts, creating 25 squares of 1mm x 1mm size. Use a soft brush to gently sweep along the diagonal of the grid five times to remove debris. Apply a special pressure-sensitive adhesive tape (25mm wide, adhesion ≥10 N / 25mm) tightly to the grid area, ensuring no air bubbles, and then rapidly peel off the tape at a 60° angle within 1-2 seconds. Repeat the test three times at different locations on the same sample.

[0048] Results evaluation: Evaluation was conducted based on the proportion of coating peeling area in the grid area, according to the grading chart in the standard appendix. Grade 0 is the best (completely smooth cut edges, no peeling of any grid), and Grade 5 is the worst (peeling area greater than 65%).

[0049] 2. UV aging resistance test

[0050] Test standard: GB / T 1865-2009 "Artificial weathering and artificial radiation exposure of paints and varnishes"

[0051] Test equipment and conditions: A QUV / spray ultraviolet aging test chamber was used. The test cycle was as follows: 8 hours of irradiation with a UVA-340 lamp at 60±3℃; followed by 4 hours of condensation at 50±3℃. The total test duration was 1000 hours.

[0052] Testing and Calculation: The gloss of the coating surface was measured using a 60° gloss meter before and after testing. Five points were evenly selected on each sample surface for measurement, and the arithmetic mean was taken. The gloss loss rate was calculated using the following formula:

[0053] Gloss loss rate (%) = (G0 - G1) / G0 × 100%

[0054] Wherein, G0 is the average gloss value before aging, and G1 is the average gloss value after aging.

[0055] 3. Hydrophobicity test

[0056] Test standard: GB / T 30693-2014 "Measurement of Contact Angle of Plastics"

[0057] Test Method: The seated drop method was used with a commercial contact angle measuring instrument. Under standard laboratory conditions (temperature 23±2℃, relative humidity 50±10%), a 5.0±0.5 μL droplet of ultrapure water was automatically dropped onto the coating surface using a micro-syringe. After the droplet stabilized for 5 seconds, the image was analyzed using the Young-Laplace fitting method in the instrument software to read the left and right contact angles and calculate their average value. Measurements were taken at least five randomly selected locations on each sample surface, and the final result was the arithmetic mean of all measurement points.

[0058] 4. Freeze-thaw resistance test

[0059] Testing Standard: GB / T 50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete"

[0060] Test method: A standard stone specimen (100mm×100mm×100mm) coated with a protective coating was placed in an environmental chamber and subjected to 50 freeze-thaw cycles. The conditions for a single cycle were: freezing in air at -20±2℃ for 4 hours, followed by thawing in a water bath at 20±2℃ for 4 hours.

[0061] Testing and evaluation:

[0062] Visual inspection: After 50 cycles, visually inspect the coating surface with a 10x magnifying glass to check for cracks, blistering, powdering, or peeling.

[0063] Compressive strength retention rate: The compressive strength of blank stone specimens without freeze-thaw cycles and coated specimens that have undergone freeze-thaw cycles were tested separately. The formula for calculating the compressive strength retention rate is:

[0064] Compressive strength retention rate (%) = Fc / F0 × 100%

[0065] Where Fc is the compressive strength of the protected test block after freeze-thaw, and F0 is the compressive strength of the blank test block.

[0066] 5. Stain resistance test

[0067] Testing standards: The testing shall be conducted in accordance with the relevant principles in GB / T 1766-2008 "Rating Methods for Aging of Paint and Varnish Coatings".

[0068] Pollutant preparation: Mix 0.1g of carbon black powder with a particle size of 20nm with 1mL of deionized water and stir with a glass rod to prepare a uniform carbon black sludge solution.

[0069] Test method: Carbon black stains were evenly coated onto the surface of the coating using a soft brush, forming a stain layer approximately 0.1 mm thick. The sample was then left to stand horizontally for 24 hours in a standard environment with a temperature of 23±2℃ and a relative humidity of 50±10%. Subsequently, the sample was fixed on a support at a 45° angle to the horizontal plane and rinsed with flowing deionized water at a flow rate of 300±10 mL / min from a height of 10 cm above for 30 seconds.

[0070] Results Assessment: The rinsed sample was compared with a standard soiled sample image, and the anti-fouling level was assessed based on the area and visibility of residual stains on the surface. Level 1 indicates that there is virtually no stain residue and the surface is clean; Level 5 indicates that there is severe stain residue.

[0071] Example 1

[0072] Coating material composition (by weight):

[0073] Bottom layer: 50 parts of methyltrimethoxysilane modified silica sol (particle size 30nm, solid content 35%), 8 parts of nano alumina (particle size 20nm), 5 parts of KH550 silane coupling agent, 12 parts of water-soluble epoxy resin (epoxy value 0.5eq / 100g), 3 parts of polyamide curing agent, 2 parts of polycarboxylate dispersant, and 20 parts of deionized water;

[0074] Topcoat: 40 parts fluorocarbon resin, 5 parts anatase nano titanium dioxide (10nm particle size), 3 parts nano zinc oxide (15nm particle size), 2 parts polytetrafluoroethylene micro powder (3μm particle size), 3 parts dibutyl phthalate, 1.5 parts polyether modified polydimethylsiloxane, and 28 parts ethyl acetate-xylene mixed solvent (1:1.5).

[0075] Preparation and coating process:

[0076] Base coat preparation: Prepared according to the process of "mixture A → mixture B (stirring at 800r / min for 35min + sonication at 300W for 25min) → mixture C → base coat";

[0077] Topcoat preparation: Prepared according to the process of "mixture D → mixture E (stirring at 1000r / min for 45min + sonication at 400W for 35min) → topcoat coating";

[0078] Coating: After stone pretreatment, spray the base coat (40μm thick, cure at 90℃ for 2.5h), and then spray the top coat (30μm thick, cure at 130℃ for 2h).

[0079] The performance test results are shown in the table below:

[0080] .

[0081] Example 2

[0082] Coating material composition (by weight):

[0083] Bottom layer: 45 parts of methyltrimethoxysilane modified silica sol (particle size 20nm, solid content 30%), 6 parts of nano alumina (particle size 15nm), 4 parts of KH560 silane coupling agent, 11 parts of water-soluble epoxy resin (epoxy value 0.45eq / 100g), 2.5 parts of polyamide curing agent, 1.5 parts of polycarboxylate dispersant, and 18 parts of deionized water;

[0084] Topcoat: 35 parts fluorocarbon resin, 4 parts anatase nano titanium dioxide (particle size 15nm), 3 parts nano zinc oxide (particle size 20nm), 2 parts polytetrafluoroethylene micro powder (particle size 2μm), 2.5 parts dibutyl phthalate, 1.2 parts polyether modified polydimethylsiloxane, and 25 parts ethyl acetate-xylene mixed solvent (1:1.2).

[0085] Preparation and coating process:

[0086] Bottom layer preparation: Mixture B was stirred at 700 r / min for 35 min and then sonicated at 400 W for 20 min;

[0087] Surface layer preparation: Mixture E was stirred at 1100 r / min for 40 min and then sonicated at 500 W for 30 min;

[0088] Coating: Brush on the base coat (35μm thick, cure at 85℃ for 2.5h), then spray on the top coat (25μm thick, cure at 125℃ for 2h).

[0089] The performance test results are shown in the table below:

[0090] .

[0091] Example 3

[0092] Coating material composition (by weight):

[0093] Bottom layer: 55 parts of methyltrimethoxysilane modified silica sol (particle size 40nm, solid content 38%), 9 parts of nano alumina (particle size 25nm), 6 parts of KH550 silane coupling agent, 13 parts of water-soluble epoxy resin (epoxy value 0.55eq / 100g), 4 parts of polyamide curing agent, 2.5 parts of polycarboxylate dispersant, and 22 parts of deionized water;

[0094] Topcoat: 45 parts fluorocarbon resin, 6 parts anatase nano titanium dioxide (8nm particle size), 4 parts nano zinc oxide (12nm particle size), 3 parts polytetrafluoroethylene micro powder (4μm particle size), 4 parts dibutyl phthalate, 1.8 parts polyether modified polydimethylsiloxane, and 32 parts ethyl acetate-xylene mixed solvent (1:1.8).

[0095] Preparation and coating process:

[0096] Bottom layer preparation: Mixture B was stirred at 900 r / min for 38 min and then sonicated at 450 W for 28 min;

[0097] Topcoat preparation: Mixture E was stirred at 1200 r / min for 48 min and then sonicated at 550 W for 38 min; Coating: The base layer (thickness 45 μm, cured at 95℃ for 3 h) was sprayed, and the topcoat (thickness 35 μm, cured at 140℃ for 2.5 h) was sprayed.

[0098] The performance test results are shown in the table below:

[0099] .

[0100] Example 4: Verifying the anti-aging cycle of the present invention

[0101] The aging of outdoor masonry substrates mainly stems from ultraviolet radiation, temperature and humidity cycles (freeze-thaw), and moisture / contaminant intrusion. Examples 1-3, through targeted testing, quantitatively demonstrate the coating's resistance to these factors, providing crucial support for an 8-10 year cycle.

[0102] 1. UV resistance aging test (corresponding to outdoor light aging)

[0103] Test standards and conditions: Refer to GB / T 1865-2009, use QUV ultraviolet light aging test chamber, use UVA-340 lamp tube (simulating outdoor near ultraviolet light) to carry out "60℃ irradiation for 8h + 50℃ condensation for 4h" cycle, for a total duration of 1000h (1000h is commonly used in the industry to simulate 3-5 years of outdoor light aging).

[0104] Example data:

[0105] Example 1: After 1000 hours, the gloss loss rate was only 8.5%;

[0106] Example 2: Loss rate 9.2%;

[0107] Example 3: Loss rate as low as 7.8%.

[0108] Related logic: Ultraviolet radiation is the primary cause of aging in outdoor coatings (leading to resin degradation, coating chalking and fading). The extremely low gloss loss rate in the example proves that the coating (top layer fluorocarbon resin + nano titanium dioxide / zinc oxide synergy) can resist ultraviolet erosion for a long time, and its performance in the 1000h test is far better than the industry average (usually a loss rate of ≤15% is considered qualified). It can be inferred that its actual resistance to light aging can cover 8-10 years.

[0109] 2. Freeze-thaw resistance test (corresponding to outdoor temperature and humidity cycle aging)

[0110] Test standards and conditions: Refer to GB / T 50082-2009, and subject the coated stone test blocks to 50 freeze-thaw cycles (-20℃ freezing for 4 hours + 20℃ water bath thawing for 4 hours, simulating freeze-thaw damage caused by outdoor winter and summer temperature differences and alternating rain and snow).

[0111] Example data:

[0112] Examples 1 and 2: After 50 cycles, the coating showed no cracks or peeling, and the stone's compressive strength retention rate reached 90%-92%.

[0113] Example 3: Due to the more complete filling of the bottom layer of nano-alumina, the compressive strength retention rate is higher.

[0114] Related logic: Outdoor brick and stone substrates often suffer from the expansion of internal pore water due to freeze-thaw cycles, which can damage the bond between the coating and the substrate. In the example, the coating is undamaged and has a high strength retention rate, proving that it is tightly bonded to the stone and has strong resistance to temperature changes. It can withstand long-term freeze-thaw cycles and avoid loss of protective function due to structural damage.

[0115] 3. Adhesion + Hydrophobicity + Stain Resistance Tests (corresponding to outdoor moisture / pollutant intrusion and aging)

[0116] Adhesion test (GB / T 9286-1998): Examples 1 and 2 achieved adhesion level 1 (peeling area at the cut edge ≤ 5%), and Example 3 achieved level 0 (no peeling), ensuring that the coating does not peel off for a long time;

[0117] Hydrophobicity test (GB / T 30693-2014): Example 1: Water contact angle 115°; Example 2: Up to 112° (high hydrophobicity state), which can reduce the penetration of rainwater and dew into the interior of the stone;

[0118] Stain resistance test (refer to GB / T 1766-2008): Examples 1 and 2 both reached Level 1 (no stains left), avoiding dust and pollutants from adhering and accelerating coating aging.

[0119] Related logic: Moisture and contaminant intrusion are major contributors to the aging of masonry substrates (such as acid rain corrosion and mold growth). In this example, the coating's high adhesion, high hydrophobicity, and strong anti-fouling properties block the intrusion path at the source, further extending the protection period.

[0120] 4. The premise of an "8-10 year anti-aging cycle" is that the coating structure is uniform and fully cured. Examples 1-3 ensure that the coating has a stable and long-lasting foundation by precisely controlling process parameters.

[0121] Nanofiller dispersion process: The bottom layer of nano-alumina is stirred at 800-1000 r / min + ultrasonically at 300-500 W (e.g., in Example 1, it is stirred at 800 r / min for 35 min + ultrasonically at 300 W for 25 min), and the top layer of nanofiller is stirred at 1000-1200 r / min + ultrasonically at 400-600 W (e.g., in Example 2, it is stirred at 1100 r / min for 40 min + ultrasonically at 500 W for 30 min). This process avoids nanoparticle agglomeration, ensures uniform filling of coating pores, and improves structural density.

[0122] Curing process: The bottom layer is cured at 80-100℃ for 2-3 hours (e.g., 90℃ for 2.5 hours in Example 1), and the top layer is cured at 120-150℃ for 1.5-2.5 hours (e.g., 130℃ for 2 hours in Example 1) to ensure that the resin is fully cross-linked and forms a stable three-dimensional network structure, thus avoiding easy degradation of the coating due to insufficient curing;

[0123] Coating thickness control: bottom layer 30-50μm (40μm in Example 1), top layer 20-40μm (30μm in Example 1), which ensures that the protective layer thickness is sufficient to resist erosion, while avoiding excessive thickness that may cause internal stress cracking.

[0124] 5. Conclusion: The data from the examples and the process together support an 8-10 year cycle.

[0125] Examples 1-3 demonstrate that the coating maintains excellent performance under key outdoor aging factors such as ultraviolet radiation, freeze-thaw cycles, and moisture / contaminants through standardized testing. Simultaneously, a structurally stable coating is prepared using precise process parameters. The combination of these two factors provides a dual guarantee of "performance compliance + structural reliability," ultimately leading to the conclusion that "the effective anti-aging period can reach 8-10 years," a period far superior to the existing 3-5 year level of protective coatings. This is the core beneficial effect of this invention.

Claims

1. A long-lasting anti-aging protective coating for masonry substrates, characterized in that, The protective coating consists of a base layer and a top layer. By weight, the base layer comprises: 40-60 parts modified silica sol, 5-10 parts nano alumina, 3-8 parts silane coupling agent, 10-15 parts water-soluble epoxy resin, 2-5 parts curing agent, 1-3 parts dispersant, and 15-25 parts deionized water. The top layer comprises: 30-50 parts fluorocarbon resin, 3-8 parts nano titanium dioxide, 2-5 parts nano zinc oxide, 1-4 parts polytetrafluoroethylene micro powder, 2-5 parts plasticizer, 1-2 parts leveling agent, and 20-35 parts solvent.

2. The long-lasting anti-aging protective coating for masonry substrates according to claim 1, characterized in that, The modified silica sol is methyltrimethoxysilane with a particle size of 20-50 nm and a solid content of 30-40%.

3. The long-lasting anti-aging protective coating for masonry substrates according to claim 1, characterized in that, The nano-alumina has a particle size of 10-30 nm; the nano-titanium dioxide is anatase type with a particle size of 5-20 nm; the nano-zinc oxide has a particle size of 10-25 nm; and the polytetrafluoroethylene micro powder has a particle size of 1-5 μm.

4. The long-lasting anti-aging protective coating for masonry substrates according to claim 1, characterized in that, The silane coupling agent is γ-aminopropyltriethoxysilane or γ-glycidoxypropyltrimethoxysilane.

5. The long-lasting anti-aging protective coating for masonry substrates according to claim 1, characterized in that, The epoxy value of the water-soluble epoxy resin is 0.4-0.6 eq / 100g.

6. The long-lasting anti-aging protective coating for masonry substrates according to claim 1, characterized in that, The curing agent is polyamide; the dispersant is a polycarboxylate dispersant; the plasticizer is dibutyl phthalate; and the leveling agent is polyether-modified polydimethylsiloxane.

7. The long-lasting anti-aging protective coating for masonry substrates according to claim 1, characterized in that, The solvent is a mixture of ethyl acetate and xylene, with a weight ratio of 1:1-2.

8. A method for preparing a long-lasting anti-aging protective coating for masonry substrates as described in any one of claims 1-7, characterized in that, Includes the following steps: S1, the preparation of the underlying layer, includes: S1.1 Weigh the modified silica sol and deionized water according to the weight proportions, add them to the stirring tank, and stir at 300-500 r / min for 10-15 min to obtain mixture A; S1.2, add nano-alumina and dispersant to mixture A, stir at high speed of 800-1000 r / min for 30-40 min, and simultaneously disperse with ultrasonic waves at 300-500 W for 20-30 min to obtain mixture B; S1.3, reduce to 400-600 r / min, add silane coupling agent and stir for 15-20 min, then add water-soluble epoxy resin and stir for 20-30 min to obtain mixture C; S1.4, add curing agent to mixture C, stir at 300-500 r / min for 15-20 min, let stand to degas for 10-15 min, and obtain the base coat; S2, preparation of the surface layer, including: S2.1 Weigh the fluorocarbon resin and solvent according to the weight proportions, add them to the mixing tank, and stir at 400-600 r / min for 20-30 min to obtain the mixture D; S2.2, Add nano-titanium dioxide, nano-zinc oxide, and polytetrafluoroethylene micro powder to mixture D, stir at high speed of 1000-1200 r / min for 40-50 min, and simultaneously disperse by ultrasonication at 400-600 W for 30-40 min to obtain mixture E; S2.3, reduce to 300-500r / min, add plasticizer and leveling agent and stir for 20-30min, let stand to degas for 15-20min to obtain the topcoat; S3, Coating application, including: S3.1, Masonry pretreatment: Remove surface impurities, sand with sandpaper, rinse with deionized water, dry at 60-80℃ for 2-3 hours, and cool to room temperature; S3.2, Apply the base coat: Apply the base coat to the stone surface with a thickness of 30-50μm, let it stand at room temperature for 1-2 hours, and cure at 80-100℃ for 2-3 hours; S3.3, Topcoat: After the base layer cools, apply the topcoat coating to the surface of the base layer with a thickness of 20-40μm. Level at room temperature for 1-1.5h, cure at 120-150℃ for 1.5-2.5h, and allow to cool naturally to obtain the final product.

9. The preparation method according to claim 8, characterized in that, In step S3, the bottom layer is coated by spraying or brushing, and the top layer is coated by spraying.

10. The application of a long-lasting anti-aging protective coating for masonry substrates as described in any one of claims 1-7 in the protection of masonry substrates, wherein the coated masonry substrates include outdoor masonry materials, which include any one of plaza paving stones, landscape sculptures, curb stones, artificial rock formations, and building facade decorative stones.