A waterproof coating for building exterior wall renovation and its preparation method

Abstract

This invention relates to the field of building waterproof coating technology, specifically to a waterproof coating for building exterior wall renovation and its preparation method. By weight, the raw materials consist of 20-60 parts acrylic emulsion, 5-30 parts polyurethane emulsion, 0.1-4.0 parts nano-silica, 0.1-2.0 parts nano-zinc oxide, 10-40 parts talc, 5-30 parts calcium carbonate, 0.1-2.0 parts composite coupling agent, 0.2-3.0 parts maleic anhydride-grafted polyethylene wax, 0.5-4.5 parts film-forming aid, 0.05-1.2 parts defoamer, 0.1-1.5 parts thickener, 0.05-0.8 parts mildew inhibitor, and 2-20 parts deionized water. The waterproof coating for building exterior wall renovation and its preparation method provided by this invention effectively solve many defects in existing waterproof coatings, possessing significant technical advantages and practical value.

Description

Technical Field

[0001] This invention relates to the field of building waterproof coating technology, specifically to a waterproof coating for building exterior wall renovation and its preparation method. Background Technology

[0002] After long-term use, building exterior walls are susceptible to cracking, bulging, and water seepage due to natural factors such as temperature and humidity changes and wind and rain erosion. Exterior wall renovation has become an important part of building maintenance, and waterproof coatings are the core materials in renovation projects. Their performance directly determines the waterproof protection effect and service life of the exterior walls.

[0003] Currently, most mainstream waterproof coatings for building exterior walls use a single emulsion as the base material, making it difficult to simultaneously achieve adhesion, elasticity, and weather resistance. They exhibit poor compatibility with older exterior wall substrates, such as minor cracks and uneven interfaces, leading to coating peeling and cracking. In the filler modification stage, existing technologies often use a single coupling agent to treat the filler. Nanofillers are prone to agglomeration and poor compatibility with the base material, resulting in insufficient coating density and failing to meet practical application requirements for impermeability and antibacterial properties.

[0004] Meanwhile, traditional preparation processes often employ uniform temperature and stirring parameters without gradient control based on raw material characteristics, resulting in uneven dispersion of components, poor coating film quality, and significant shortcomings in high and low temperature resistance and workability. Furthermore, some waterproof coatings suffer from high VOC content and rapid performance degradation after weathering, lacking sufficient environmental friendliness and long-term stability, and their overall performance cannot meet the diverse and demanding application scenarios of old building exterior wall renovation. Summary of the Invention

[0005] The primary objective of this invention is to provide a waterproof coating for building exterior wall renovation and its preparation method.

[0006] A further objective of this invention is to provide a waterproof coating for exterior wall renovation, comprising, by weight, 20-60 parts acrylic emulsion, 5-30 parts polyurethane emulsion, 0.1-4.0 parts nano silica, 0.1-2.0 parts nano zinc oxide, 10-40 parts talc, 5-30 parts calcium carbonate, 0.1-2.0 parts composite coupling agent, 0.2-3.0 parts maleic anhydride-grafted polyethylene wax, 0.5-4.5 parts film-forming aid, 0.05-1.2 parts defoamer, 0.1-1.5 parts thickener, 0.05-0.8 parts mildew inhibitor, and 2-20 parts deionized water.

[0007] Preferably, the composite coupling agent is composed of a silane coupling agent and a titanate coupling agent, wherein the silane coupling agent is 0.07-1.5 parts by mass and the titanate coupling agent is 0.03-0.5 parts by mass.

[0008] Preferably, the mass ratio of nano-silica to nano-zinc oxide in the raw material is (0.1-4.0):(0.1-2.0).

[0009] Preferably, by weight, the raw materials consist of 32 parts acrylic emulsion, 18 parts polyurethane emulsion, 2.2 parts nano silica, 0.7 parts nano zinc oxide, 25 parts talc, 18 parts calcium carbonate, 1.0 part composite coupling agent, 1.2 parts maleic anhydride grafted polyethylene wax, 2.2 parts film-forming aid, 0.35 parts defoamer, 0.6 parts thickener, 0.25 parts mildew inhibitor, and 12 parts deionized water. The composite coupling agent is a compound of 0.7 parts silane coupling agent and 0.3 parts titanate coupling agent.

[0010] A method for preparing a waterproof coating for building exterior wall renovation includes the following steps: (1) Pretreatment of filler: Mix nano silica, nano zinc oxide, talc powder and calcium carbonate, add composite coupling agent for dry modification, stir at high speed for 10-30 minutes, stirring speed 1000-1800 rpm, and dry at 105-120 degrees Celsius for 1.5-3 hours to obtain modified composite filler; (2) Modification of base material: Add acrylic emulsion and polyurethane emulsion to the reactor, heat to 55-70 degrees Celsius, stir at 700-1200 rpm, add maleic anhydride grafted polyethylene wax and stir for 25-45 minutes to obtain composite modified emulsion. (3) Mixing and dispersing: Add the modified composite filler to the composite modified emulsion and stir at a speed of 900-1500 rpm for 35-60 minutes; (4) Additives: Cool the system to 30-45 degrees Celsius, add film-forming aid, defoamer, thickener and mildew inhibitor in sequence, stir at 400-700 rpm for 15-30 minutes to obtain preliminary waterproof coating; (5) Curing and filtration: Let the preliminary waterproof coating stand for 1.5-4 hours to cure, filter to remove impurities, and obtain the finished waterproof coating.

[0011] Preferably, the dry modification in step (1) is a mechanical stirring modification under solvent-free conditions, and the stirring process is continuous and uniform stirring.

[0012] Preferably, the sequential addition in step (4) means adding one additive at a time and stirring until the system is homogeneous, that is, adding one additive and stirring until homogeneous before adding the next additive.

[0013] Preferably, the stirring in the reactor in step (2) is continuous and uniform, and the reactor is in an atmospheric pressure environment during the stirring process.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. The waterproof coating for building exterior wall renovation and its preparation method provided by the present invention effectively solve many defects of existing waterproof coatings and have significant technical advantages and practical value.

[0015] 2. This invention uses acrylic emulsion and polyurethane emulsion composite as base material, combined with maleic anhydride grafted polyethylene wax for cross-linking modification, to achieve a synergistic improvement in adhesion, weather resistance and elasticity, which can adapt to the slight deformation of old exterior wall base, and reduce coating peeling and cracking problems from the root.

[0016] 3. This invention uses a composite coupling agent to dry modify nanofillers and conventional fillers, effectively solving the problem of nanoparticle agglomeration, significantly improving the compatibility between fillers and base materials, enhancing the density of the coating, and significantly improving the anti-permeability and antibacterial properties of the coating.

[0017] 4. The preparation process of this invention adopts gradient temperature control and staged stirring. The parameters are optimized according to the reaction characteristics of the raw materials in each process to ensure that the components are evenly dispersed, further improve the coating film quality, and make the weather resistance and high and low temperature resistance of the coating more stable.

[0018] 5. This invention also reasonably expands the protection range of raw material ratios, and the upper and lower limits of the ratios can meet the basic requirements of exterior wall renovation. At the same time, it designs a comprehensive optimal ratio scheme that takes into account performance, cost and workability.

[0019] 6. The VOC content of the coating of this invention complies with environmental protection standards, and it has excellent application smoothness and film smoothness. All core performance characteristics are superior to existing mainstream products. The synergy of base material composite, filler modification and process optimization allows the coating to fully adapt to the renovation needs of various old building exterior walls, and has high practical application and promotion value. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1:

[0022] Raw material proportions (by weight): 35 parts acrylic emulsion, 15 parts polyurethane emulsion, 1.5 parts nano silica, 0.5 parts nano zinc oxide, 20 parts talc, 15 parts calcium carbonate, 0.8 parts composite coupling agent, 0.5 parts silane coupling agent, 0.3 parts titanate coupling agent, 1.0 part maleic anhydride grafted polyethylene wax, 2.0 parts film-forming aid, 0.3 parts defoamer, 0.5 parts thickener, 0.2 parts mildew inhibitor, and 10 parts deionized water.

[0023] Preparation method: Step 1: Filler pretreatment. Nano silica, nano zinc oxide, talc powder and calcium carbonate are mixed, a composite coupling agent is added, and the mixture is dry modified. The mixture is stirred at high speed for 15 minutes at a stirring speed of 1200 rpm and dried at 110 degrees Celsius for 2 hours to obtain the modified composite filler for later use. The second step is base material modification. Acrylic emulsion and polyurethane emulsion are added to the reactor, heated to 60 degrees Celsius, stirred at 800 rpm, maleic anhydride-grafted polyethylene wax is added, and stirred for 30 minutes to obtain a composite modified emulsion. The third step is mixing and dispersing. The modified composite filler is added to the composite modified emulsion, and the stirring speed is 1000 rpm for 40 minutes. The fourth step involves adding additives. The temperature is lowered to 40 degrees Celsius, and film-forming aids, defoamers, thickeners, and mildew inhibitors are added in sequence. The stirring speed is 500 revolutions per minute, and the mixture is stirred for 20 minutes to obtain a preliminary waterproof coating. The fifth step is to let it mature for 2 hours, then filter to remove impurities and obtain the finished product.

[0024] This embodiment is based on a formulation that uses a composite emulsion to initially address the problem of generally poor adhesion of single emulsion base materials in existing technologies, and improves compatibility by modifying fillers with composite coupling agents.

[0025] Example 2:

[0026] Raw material proportions (by weight): 30 parts acrylic emulsion, 20 parts polyurethane emulsion, 1.5 parts nano silica, 0.5 parts nano zinc oxide, 20 parts talc, 15 parts calcium carbonate, 0.8 parts composite coupling agent, 0.5 parts silane coupling agent, 0.3 parts titanate coupling agent, 1.0 part maleic anhydride grafted polyethylene wax, 2.0 parts film-forming aid, 0.3 parts defoamer, 0.5 parts thickener, 0.2 parts mildew inhibitor, and 10 parts deionized water.

[0027] Preparation method: The first step is filler pretreatment, which is completely consistent with Example 1; the second step is base material modification, in which acrylic emulsion and polyurethane emulsion are added to the reaction vessel, heated to 60 degrees Celsius, stirred at 800 rpm, maleic anhydride grafted polyethylene wax is added, and stirred for 30 minutes to obtain composite modified emulsion. Steps three through five are completely identical to those in Example 1.

[0028] This embodiment is based on Embodiment 1, but adjusts the amount of acrylic emulsion and polyurethane emulsion, increases the proportion of polyurethane emulsion, and retains the adhesion advantage of Embodiment 1, adapting to the needs of minor cracking and deformation of old exterior wall substrates.

[0029] Example 3:

[0030] Raw material proportions (by weight): 30 parts acrylic emulsion, 20 parts polyurethane emulsion, 2.5 parts nano silica, 0.8 parts nano zinc oxide, 20 parts talc, 15 parts calcium carbonate, 0.8 parts composite coupling agent, 0.5 parts silane coupling agent, 0.3 parts titanate coupling agent, 1.0 part maleic anhydride grafted polyethylene wax, 2.0 parts film-forming aid, 0.3 parts defoamer, 0.5 parts thickener, 0.2 parts mildew inhibitor, and 10 parts deionized water.

[0031] Preparation method: Step 1: Filler pretreatment. Nano silica, nano zinc oxide, talc powder, and calcium carbonate are mixed, a composite coupling agent is added, and the mixture is dry-modified. The mixture is stirred at high speed for 20 minutes at a stirring speed of 1200 rpm and then dried at 110 degrees Celsius for 2 hours to obtain the modified composite filler for later use. Steps two through five are completely identical to those in Example 2.

[0032] Based on Example 2, this embodiment increases the amount of nano-silica and nano-zinc oxide, and extends the pretreatment stirring time of the filler. It utilizes the filling and reinforcing effect of nanomaterials to improve the density of the coating and adapt it to the humid environment of the exterior wall.

[0033] Example 4:

[0034] Raw material proportions (by weight): 30 parts acrylic emulsion, 20 parts polyurethane emulsion, 2.5 parts nano silica, 0.8 parts nano zinc oxide, 20 parts talc, 15 parts calcium carbonate, 1.2 parts composite coupling agent, 0.9 parts silane coupling agent, 0.3 parts titanate coupling agent, 1.0 part maleic anhydride grafted polyethylene wax, 2.0 parts film-forming aid, 0.3 parts defoamer, 0.5 parts thickener, 0.2 parts mildew inhibitor, and 10 parts deionized water.

[0035] Preparation method: Step 1: Filler pretreatment. Nano silica, nano zinc oxide, talc powder, and calcium carbonate are mixed, a composite coupling agent is added, and the mixture is dry-modified. The mixture is stirred at high speed for 20 minutes at a stirring speed of 1200 rpm and then dried at 115 degrees Celsius for 2 hours to obtain the modified composite filler for later use. Steps two through five are completely identical to those in Example 3.

[0036] Based on Example 3, this embodiment adjusts the total amount of composite coupling agent and the ratio of silane coupling agent to titanate coupling agent, increases the amount of silane coupling agent, and increases the pretreatment drying temperature of filler to enhance the molecular bridging effect of coupling agent and improve the adhesion between coating and old cement substrate.

[0037] Example 5:

[0038] Raw material proportions (by weight): 30 parts acrylic emulsion, 20 parts polyurethane emulsion, 2.5 parts nano silica, 0.8 parts nano zinc oxide, 20 parts talc, 15 parts calcium carbonate, 1.2 parts composite coupling agent, 0.9 parts silane coupling agent, 0.3 parts titanate coupling agent, 1.0 part maleic anhydride grafted polyethylene wax, 2.0 parts film-forming aid, 0.3 parts defoamer, 0.5 parts thickener, 0.2 parts mildew inhibitor, and 10 parts deionized water.

[0039] Preparation method: Step 1: Filler pretreatment. Nano silica, nano zinc oxide, talc powder, and calcium carbonate are mixed, a composite coupling agent is added, and the mixture is dry-modified. The mixture is stirred at high speed for 25 minutes at a stirring speed of 1500 rpm and dried at 115 degrees Celsius for 2 hours to obtain the modified composite filler for later use. The second step involves modifying the base material. Acrylic emulsion and polyurethane emulsion are added to a reaction vessel, heated to 65 degrees Celsius, and stirred at 1000 rpm. Maleic anhydride-grafted polyethylene wax is added and stirred for 40 minutes to obtain a composite modified emulsion. The third step is mixing and dispersing. The modified composite filler is added to the composite modified emulsion, and the stirring speed is 1200 rpm for 50 minutes. The fourth step involves adding additives. The temperature is lowered to 35 degrees Celsius, and film-forming aids, defoamers, thickeners, and mildew inhibitors are added in sequence. The stirring speed is 600 revolutions per minute, and the mixture is stirred for 25 minutes to obtain a preliminary waterproof coating. The fifth step is to let it mature for 3 hours, then filter to remove impurities and obtain the finished product.

[0040] Based on Example 4, this embodiment optimizes the stirring speed, temperature, and time of the preparation process to further improve the density, weather resistance, and mechanical properties of the coating.

[0041] Example 6:

[0042] Raw material proportions (by weight): 20 parts acrylic emulsion, 30 parts polyurethane emulsion, 4.0 parts nano silica, 2.0 parts nano zinc oxide, 40 parts talc, 30 parts calcium carbonate, 2.0 parts composite coupling agent, 1.5 parts silane coupling agent, 0.5 parts titanate coupling agent, 3.0 parts maleic anhydride grafted polyethylene wax, 4.5 parts film-forming aid, 1.2 parts defoamer, 1.5 parts thickener, 0.8 parts mildew inhibitor, and 20 parts deionized water.

[0043] Preparation method: Step 1: Filler pretreatment. Nano silica, nano zinc oxide, talc powder, and calcium carbonate are mixed, a composite coupling agent is added, and the mixture is dry-modified. The mixture is stirred at high speed for 30 minutes at a stirring speed of 1800 rpm and dried at 120 degrees Celsius for 3 hours to obtain the modified composite filler for later use. The second step involves modifying the base material. Acrylic emulsion and polyurethane emulsion are added to a reaction vessel, heated to 70 degrees Celsius, and stirred at 1200 rpm. Maleic anhydride-grafted polyethylene wax is added and stirred for 45 minutes to obtain a composite modified emulsion. The third step is mixing and dispersing. The modified composite filler is added to the composite modified emulsion, and the stirring speed is 1500 rpm for 60 minutes. The fourth step involves adding additives. The temperature is lowered to 45 degrees Celsius, and film-forming aids, defoamers, thickeners, and mildew inhibitors are added in sequence. The stirring speed is 700 revolutions per minute, and the mixture is stirred for 30 minutes to obtain a preliminary waterproof coating. The fifth step is maturation. Let it stand for 4 hours to mature, then filter to remove impurities and obtain the finished product.

[0044] Based on Example 5, the amount of each raw material was adjusted to the upper limit of the protection range. By optimizing the process parameters to match the upper limit ratio, the performance was tested and found to still meet the needs of old exterior wall renovation.

[0045] Example 7:

[0046] Raw material proportions (by weight): 60 parts acrylic emulsion, 5 parts polyurethane emulsion, 0.1 parts nano silica, 0.1 parts nano zinc oxide, 10 parts talc, 5 parts calcium carbonate, 0.1 parts composite coupling agent, 0.07 parts silane coupling agent, 0.03 parts titanate coupling agent, 0.2 parts maleic anhydride grafted polyethylene wax, 0.5 parts film-forming aid, 0.05 parts defoamer, 0.1 parts thickener, 0.05 parts mildew inhibitor, and 2 parts deionized water.

[0047] Preparation method: Step 1: Filler pretreatment. Nano silica, nano zinc oxide, talc powder, and calcium carbonate are mixed, a composite coupling agent is added, and the mixture is dry-modified. The mixture is stirred at high speed for 10 minutes at a speed of 1000 rpm and dried at 105 degrees Celsius for 1.5 hours to obtain the modified composite filler for later use. The second step is base material modification. Acrylic emulsion and polyurethane emulsion are added to the reactor, heated to 55 degrees Celsius, stirred at 700 rpm, maleic anhydride-grafted polyethylene wax is added, and stirred for 25 minutes to obtain a composite modified emulsion. The third step is mixing and dispersing. The modified composite filler is added to the composite modified emulsion, and the stirring speed is 900 rpm for 35 minutes. The fourth step involves adding additives. The temperature is lowered to 30 degrees Celsius, and film-forming aids, defoamers, thickeners, and mildew inhibitors are added in sequence. The stirring speed is 400 revolutions per minute, and the mixture is stirred for 15 minutes to obtain a preliminary waterproof coating. The fifth step is maturation. Let it stand for 1.5 hours to mature, then filter to remove impurities and obtain the finished product.

[0048] Based on Example 5, the amount of each raw material was adjusted to the lower limit of the protection range. By optimizing the process parameters to match the lower limit ratio, the performance was tested and found to still meet the basic requirements for the renovation of old exterior walls.

[0049] Example 8:

[0050] Raw material proportions (by weight): 32 parts acrylic emulsion, 18 parts polyurethane emulsion, 2.2 parts nano silica, 0.7 parts nano zinc oxide, 25 parts talc, 18 parts calcium carbonate, 1.0 part composite coupling agent, 0.7 parts silane coupling agent, 0.3 parts titanate coupling agent, 1.2 parts maleic anhydride grafted polyethylene wax, 2.2 parts film-forming aid, 0.35 parts defoamer, 0.6 parts thickener, 0.25 parts mildew inhibitor, and 12 parts deionized water.

[0051] Preparation method: Step 1: Filler pretreatment. Nano silica, nano zinc oxide, talc powder, and calcium carbonate are mixed, a composite coupling agent is added, and the mixture is dry modified. The mixture is stirred at high speed for 22 minutes at a stirring speed of 1400 rpm and then dried at 112 degrees Celsius for 2.2 hours to obtain the modified composite filler for later use. The second step involves modifying the base material. Acrylic emulsion and polyurethane emulsion are added to a reactor, heated to 62 degrees Celsius, and stirred at 900 rpm. Maleic anhydride-grafted polyethylene wax is added and stirred for 35 minutes to obtain a composite modified emulsion. The third step is mixing and dispersing. The modified composite filler is added to the composite modified emulsion, and the stirring speed is 1100 rpm for 45 minutes. The fourth step involves adding additives. The temperature is lowered to 38 degrees Celsius, and film-forming aids, defoamers, thickeners, and mildew inhibitors are added in sequence. The stirring speed is 550 revolutions per minute, and the mixture is stirred for 22 minutes to obtain a preliminary waterproof coating. The fifth step is maturation. Let it stand for 2.5 hours to mature, then filter to remove impurities and obtain the finished product.

[0052] Based on Examples 1 to 7, the proportions of each raw material and process parameters are comprehensively optimized to balance performance, cost and workability, resulting in optimal overall performance and suitability for the renovation needs of most old building exteriors.

[0053] Comparative Example 1: Raw material proportions (by weight): 50 parts acrylic emulsion, 2.2 parts nano silica, 0.7 parts nano zinc oxide, 25 parts talc, 18 parts calcium carbonate, 1.0 part composite coupling agent, 0.7 parts silane coupling agent, 0.3 parts titanate coupling agent, 1.2 parts maleic anhydride grafted polyethylene wax, 2.2 parts film-forming aid, 0.35 parts defoamer, 0.6 parts thickener, 0.25 parts mildew inhibitor, and 12 parts deionized water.

[0054] Preparation method: completely consistent with Example 8.

[0055] Comparative Example 2: Raw material proportions (by weight): 32 parts acrylic emulsion, 18 parts polyurethane emulsion, 2.2 parts nano silica, 0.7 parts nano zinc oxide, 25 parts talc, 18 parts calcium carbonate, 1.0 part silane coupling agent, 1.2 parts maleic anhydride grafted polyethylene wax, 2.2 parts film-forming aid, 0.35 parts defoamer, 0.6 parts thickener, 0.25 parts mildew inhibitor, and 12 parts deionized water.

[0056] Preparation method: Step 1: Filler pretreatment. Nano silica, nano zinc oxide, talc powder, and calcium carbonate are mixed, and silane coupling agent is added. Dry modification is carried out by stirring at high speed for 22 minutes at a stirring speed of 1400 rpm and drying at 112 degrees Celsius for 2.2 hours to obtain modified composite filler for later use. Steps two through five are completely identical to those in Example 8.

[0057] Comparative Example 3: Raw material proportions by weight: completely consistent with Example 8.

[0058] Preparation method: All steps were carried out at a uniform stirring speed of 800 rpm and a uniform temperature of 50 degrees Celsius. No segmented temperature control or gradient stirring was performed. The remaining steps were completely consistent with those in Example 8.

[0059] Comparative Example 4: Raw material proportions (by weight): 32 parts acrylic emulsion, 18 parts polyurethane emulsion, 2.2 parts nano silica, 0.7 parts nano zinc oxide, 25 parts talc, 18 parts calcium carbonate, 1.2 parts maleic anhydride grafted polyethylene wax, 2.2 parts film-forming aid, 0.35 parts defoamer, 0.6 parts thickener, 0.25 parts mildew inhibitor, and 12 parts deionized water.

[0060] Preparation method: The first step of filler pretreatment is omitted, and the unmodified filler is directly added to the base material. The remaining steps are completely consistent with those in Example 8.

[0061] Comparative Example 5: Raw material proportions (by weight): 32 parts acrylic emulsion, 18 parts polyurethane emulsion, 2.2 parts nano silica, 0.7 parts nano zinc oxide, 25 parts talc, 18 parts calcium carbonate, 1.0 part composite coupling agent, 0.7 parts silane coupling agent, 0.3 parts titanate coupling agent, 2.2 parts film-forming aid, 0.35 parts defoamer, 0.6 parts thickener, 0.25 parts mildew inhibitor, and 12 parts deionized water.

[0062] Preparation method: In the second step of base material modification, only acrylic emulsion and polyurethane emulsion are mixed, and maleic anhydride grafted polyethylene wax is not added. The remaining steps are completely consistent with those in Example 8.

[0063] Comparative Example 6: Raw material proportions (by weight): 32 parts acrylic emulsion, 18 parts polyurethane emulsion, 2.9 parts nano silica, 25 parts talc, 18 parts calcium carbonate, 1.0 part composite coupling agent, 0.7 parts silane coupling agent, 0.3 parts titanate coupling agent, 1.2 parts maleic anhydride grafted polyethylene wax, 2.2 parts film-forming aid, 0.35 parts defoamer, 0.6 parts thickener, 0.25 parts mildew inhibitor, and 12 parts deionized water.

[0064] Preparation method: completely consistent with Example 8.

[0065] Comparative Example 7: Raw material proportions (by weight): 50 parts acrylic emulsion, 2.2 parts nano silica, 0.7 parts nano zinc oxide, 25 parts talc, 18 parts calcium carbonate, 1.0 part silane coupling agent, 1.2 parts maleic anhydride grafted polyethylene wax, 2.2 parts film-forming aid, 0.35 parts defoamer, 0.6 parts thickener, 0.25 parts mildew inhibitor, and 12 parts deionized water.

[0066] Preparation method: Step 1: Filler pretreatment. Nano silica, nano zinc oxide, talc powder, and calcium carbonate are mixed, and silane coupling agent is added. Dry modification is carried out by stirring at high speed for 22 minutes at a stirring speed of 1400 rpm and drying at 112 degrees Celsius for 2.2 hours to obtain modified composite filler for later use. Steps two through five are completely identical to those in Example 8.

[0067] Comparative Example 8: Raw material proportions by weight: completely consistent with Example 8.

[0068] Preparation method: All steps were carried out at a uniform stirring speed of 800 rpm and a uniform temperature of 50 degrees Celsius. No segmented temperature control or gradient stirring was performed. The remaining steps were completely consistent with those in Example 8.

[0069] Blank control group Commercially available ordinary building exterior wall waterproof coatings were selected. The raw materials are single acrylic emulsion, conventional fillers and additives. The preparation process is conventional stirring, without composite modification and gradient process optimization. It represents the mainstream level of the existing technology and is used to compare the overall performance differences between the present invention and the existing technology.

[0070] Performance testing and results analysis: Test sample: The waterproof coatings prepared in Examples 1 to 8 and Comparative Examples 1 to 8 were used, and commercially available ordinary building exterior wall waterproof coatings were selected as blank control groups, for a total of 17 groups of samples. Three parallel samples were prepared for each group of samples, and the test results were averaged to ensure the accuracy and reliability of the test data. Those skilled in the art can repeat this test process according to the raw material ratios, preparation methods, and test standards described in this specification to achieve the same or similar test results. There are no issues of insufficient disclosure or impossibility of implementation.

[0071] Test standards and items: The testing standards refer to GB / T16777-2008 "Test Methods for Waterproof Coatings for Buildings" and GB45671—2025 "Safety Technical Specifications for Waterproof Coatings for Buildings". Considering the actual needs of building exterior wall renovation, the following core performance indicators were selected for testing: The adhesion cross-cut test measures the adhesion level between the coating and the cement substrate, with level 1 being the best and level 5 being the worst. Hydrostatic pressure test for impermeability: The time it takes for the coating to remain leak-free under a water pressure of 0.3 MPa. The elongation at break tensile test measures the elongation at break of the coating after film formation, reflecting the coating's elasticity and crack resistance. Weather resistance artificial accelerated aging test, UV aging for 2000 hours, test the appearance changes and elongation at break retention rate of the coating after aging; High and low temperature resistance: Observe the coating's appearance and film-forming properties after 24 hours of storage at -20 degrees Celsius and 24 hours of storage at 80 degrees Celsius; Antibacterial properties: Test the coating's inhibition rate against Escherichia coli. VOC content was tested according to GB45671—2025; workability was tested for the smoothness of the coating application and the smoothness of the film formation.

[0072] The test results are shown in Table 1 below: Table 1:

[0073] Results analysis: (1) Based on the above performance test results, it can be seen that the waterproof coatings for building exterior wall renovation prepared in Examples 1 to 8 of this invention have better performance than comparative examples 1 to 8 and the blank control group, fully demonstrating the technical advantages of the synergistic innovation of the base material composite modification, filler composite modification, and preparation process gradient optimization of this invention. The performance of Examples 1 to 8 shows a clear progressive trend. Example 1, as the basic formula, has achieved a significant improvement in adhesion, solving the problem of insufficient adhesion of single emulsion base materials in the prior art. After adjusting the emulsion ratio in Example 2, the elongation at break is significantly improved and the elasticity is greatly enhanced, which is suitable for the small deformation requirements of old exterior wall bases. After increasing the amount of nano filler in Example 3, the impermeability and antibacterial rate are significantly improved, and the coating density is enhanced. After optimizing the ratio of composite coupling agent in Example 4, the adhesion is maintained at the optimal level, further improving the bonding ability between the coating and the base. After optimizing the preparation process parameters in Example 5, the components are more evenly dispersed, and the weather resistance is maintained. The retention rate is improved, and the overall performance stability is significantly enhanced. Examples 6 and 7 represent the upper and lower limits of the raw material ratio protection range, respectively. Their various properties can still meet the basic requirements for the renovation of old exterior walls, proving the rationality and feasibility of expanding the raw material ratio range of this invention, and significantly improving the adaptability and practicality of this invention. Example 8, as the optimal ratio scheme, achieves the optimal level of various properties, with the best adhesion level, the highest impermeability and elongation at break, excellent weather resistance retention rate, stable high and low temperature resistance, good antibacterial effect, VOC content that meets environmental protection standards, and excellent workability, which can fully adapt to the renovation needs of various old building exterior walls.

[0074] (2) Comparative Examples 1 to 8 lack the core inventive features of the present invention or adopt a single improvement or combination of existing technologies, and their performance has obvious shortcomings. Comparative Example 1 uses a single acrylic emulsion as the base material, and the elongation at break is significantly reduced, and the high and low temperature resistance is worse, proving that the composite emulsion synergistic modification of the present invention can effectively balance weather resistance and elasticity; Comparative Example 2 uses a single silane coupling agent to modify the filler, and the adhesion and impermeability are reduced, and the film has a grainy feel, proving that the composite coupling agent modification can effectively solve the problem of nanoparticle agglomeration and improve the compatibility between the filler and the base material; Comparative Example 3 uses a conventional preparation process without gradient temperature control and graded stirring, resulting in uneven film formation and reduced overall performance stability, proving that the gradient preparation process can achieve uniform dispersion of each component and enhance coating performance; Comparative Example 4 does not modify the filler, and the adhesion and impermeability are poor. The significant deficiencies and noticeable particulate texture of the film further demonstrate the necessity of modifying the composite coupling agent. Comparative Example 5, which did not undergo crosslinking modification of the base material, showed a decrease in weather resistance retention and stain resistance, proving that crosslinking modification of the base material can improve emulsion stability and the overall mechanical properties of the coating. Comparative Example 6, which used a single nanofiller, showed a significant decrease in antibacterial rate, proving that the composite use of nanofillers can achieve a synergistic improvement in antibacterial and anti-aging functions. Comparative Examples 7 and 8, as simple combinations of existing single improvement schemes, showed significantly lower core performance than Example 8, proving that the synergy of the three aspects of this invention is not a simple superposition of existing technologies, but rather achieves synergistic performance enhancement, possessing outstanding substantive characteristics.

[0075] (3) The blank control group used commercially available ordinary building exterior wall waterproof coatings. All performances were at the worst level, with low adhesion, insufficient impermeability and elasticity, poor weather resistance and antibacterial effect, and high VOC content. This further proves that the present invention has achieved significant improvements in comprehensive performance, environmental protection and adaptability compared with the mainstream products of the prior art.

[0076] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A waterproof coating for building exterior wall renovation, characterized in that, By weight, the raw materials consist of 20-60 parts acrylic emulsion, 5-30 parts polyurethane emulsion, 0.1-4.0 parts nano silica, 0.1-2.0 parts nano zinc oxide, 10-40 parts talc, 5-30 parts calcium carbonate, 0.1-2.0 parts composite coupling agent, 0.2-3.0 parts maleic anhydride grafted polyethylene wax, 0.5-4.5 parts film-forming aid, 0.05-1.2 parts defoamer, 0.1-1.5 parts thickener, 0.05-0.8 parts mildew inhibitor, and 2-20 parts deionized water.

2. The waterproof coating for building exterior wall renovation according to claim 1, characterized in that, The composite coupling agent is composed of a silane coupling agent and a titanate coupling agent, wherein the silane coupling agent comprises 0.07-1.5 parts by mass and the titanate coupling agent comprises 0.03-0.5 parts by mass.

3. The waterproof coating for building exterior wall renovation according to claim 1, characterized in that, The mass ratio of nano-silica to nano-zinc oxide in the raw material is (0.1-4.0):(0.1-2.0).

4. The waterproof coating for building exterior wall renovation according to claim 1, characterized in that, By weight, the raw materials consist of 32 parts acrylic emulsion, 18 parts polyurethane emulsion, 2.2 parts nano silica, 0.7 parts nano zinc oxide, 25 parts talc, 18 parts calcium carbonate, 1.0 part composite coupling agent, 1.2 parts maleic anhydride grafted polyethylene wax, 2.2 parts film-forming aid, 0.35 parts defoamer, 0.6 parts thickener, 0.25 parts mildew inhibitor, and 12 parts deionized water. The composite coupling agent is a compound of 0.7 parts silane coupling agent and 0.3 parts titanate coupling agent.

5. A method for preparing a waterproof coating for building exterior wall renovation as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) Pretreatment of filler: Mix nano silica, nano zinc oxide, talc powder and calcium carbonate, add composite coupling agent for dry modification, stir at high speed for 10-30 minutes, stirring speed 1000-1800 rpm, and dry at 105-120 degrees Celsius for 1.5-3 hours to obtain modified composite filler; (2) Modification of base material: Add acrylic emulsion and polyurethane emulsion to the reactor, heat to 55-70 degrees Celsius, stir at 700-1200 rpm, add maleic anhydride grafted polyethylene wax and stir for 25-45 minutes to obtain composite modified emulsion. (3) Mixing and dispersing: Add the modified composite filler to the composite modified emulsion and stir at a speed of 900-1500 rpm for 35-60 minutes; (4) Additives: Cool the system to 30-45 degrees Celsius, add film-forming aid, defoamer, thickener and mildew inhibitor in sequence, stir at 400-700 rpm for 15-30 minutes to obtain preliminary waterproof coating; (5) Curing and filtration: Let the preliminary waterproof coating stand for 1.5-4 hours to cure, filter to remove impurities, and obtain the finished waterproof coating.

6. The preparation method according to claim 5, characterized in that, The dry modification described in step (1) is a mechanical stirring modification under solvent-free conditions, and the stirring process is continuous and uniform stirring.

7. The preparation method according to claim 5, characterized in that, The step (4) of adding the additives sequentially means adding them one by one and stirring until the system is homogeneous. That is, after adding one additive and stirring until homogeneous, the next additive is added.

8. The preparation method according to claim 5, characterized in that, In step (2), the stirring inside the reactor is continuous and uniform, and the reactor is kept under normal pressure during the stirring process.

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