Anti-sagging waterproof coating and preparation method thereof

Abstract

The application discloses an anti-sagging waterproof coating and a preparation method thereof, and belongs to the technical field of waterproof coatings. The anti-sagging waterproof coating comprises the following raw materials in parts by mass: 30-50 parts of silane modified polyether, 5-10 parts of a thixotropic agent, 15-25 parts of a filler, 1-5 parts of a coupling agent and 0.5-2 parts of a water removing agent. The silane modified polyether has a mercaptoimidazole introduced into a polyether chain side chain. The thixotropic agent is fumed silica with a surface grafted phosphoryl siloxane. The silane modified polyether containing an imidazole ring is used as a core component of the waterproof coating. Compared with a traditional silane modified polyether, the imidazole ring introduced into the silane modified polyether can promote the hydrolysis and polycondensation of terminal siloxane, accelerate the curing of the coating, and the fumed silica with the surface grafted phosphoryl siloxane is used as the thixotropic agent. Strong ionic coordination bonds and hydrogen bond forces are formed between the phosphoryl groups on the surface of the fumed silica and the imidazole groups in the silane modified polyether, so that the anti-sagging performance of the waterproof coating is improved.

Description

A sagging-resistant waterproof coating and its preparation method Technical Field

[0001] This invention belongs to the field of waterproof coating technology, specifically relating to an anti-sagging waterproof coating and its preparation method. Background Technology

[0002] Waterproof coatings are an important component of functional building materials. During construction, waterproof coatings primarily form a waterproof layer on the surface of a building to achieve waterproofing and leak-proofing. Therefore, the performance and selection of waterproof coatings directly affect the building's performance and lifespan.

[0003] Currently, the main waterproof coatings on the market are polyurethane waterproof coatings, acrylic waterproof coatings, and JS waterproof coatings. However, with the improvement of living standards, people have increasingly higher requirements for the waterproof performance and environmental friendliness of coatings.

[0004] Silane-modified polymers are a new type of high-molecular material, generally classified into two main categories: silane-modified polyethers and silane-modified polyurethanes. Silane-modified polyethers are a class of alkoxysilane-terminated polyether resins. Silane-modified polyether waterproof coatings, prepared primarily from silane-modified polyether resins, meet green and low-carbon requirements. During the reaction process, they only absorb water from the air, undergoing hydrolysis and condensation of siloxanes. No CO2 is produced during film formation. The curing mechanism of silane-modified polyether waterproof coatings is moisture curing, possessing both waterproof and adhesive properties, and exhibiting excellent durability.

[0005] However, in the field of coatings, sagging can occur during large-area construction, resulting in drip marks on the coating surface. This not only affects the appearance but also easily damages the coating's function. Therefore, while ensuring that the waterproof effect of the silane-modified polyether waterproof coating itself is not affected, improving its anti-sagging performance can significantly enhance the overall effect of the coating. Summary of the Invention

[0006] This invention provides an anti-sagging waterproof coating and its preparation method, which can solve the problem of sagging of waterproof coatings affecting the coating effect in the prior art.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] An anti-sagging and waterproof coating, comprising the following raw materials by weight:

[0009] 30-50 parts of silane-modified polyether, 5-10 parts of thixotropic agent, 15-25 parts of filler, 1-5 parts of coupling agent, and 0.5-2 parts of dehydrating agent;

[0010] The silane-modified polyether incorporates mercaptoimidazole into the side chain of the polyether chain;

[0011] The thixotropic agent is a phosphoroyl siloxane grafted onto the surface of fumed silica.

[0012] The silane-modified polyether of the present invention contains an imidazole ring in its molecular chain, which can promote the hydrolysis and condensation of silane, accelerate the curing rate of waterproof coating, and at the same time form coordination or hydrogen bonding with the filler surface to enhance cohesion, improve the uniformity of waterproof coating components, and avoid coating sagging after construction.

[0013] Fumed silica exhibits thixotropic properties, remaining fluid during application but becoming gel-like afterward, thus reducing the fluidity of the coating. Grafting phosphoryl siloxanes onto the surface of fumed silica allows for stronger interactions between the phosphoryl groups and the imidazole groups and polyether segments in the silane-modified polyether, forming a more robust three-dimensional network. The long organic chains of the phosphoryl siloxanes improve the dispersibility of inorganic fumed silica in organic systems, making the coating stable like a gel when stationary but flowing easily during shearing during application.

[0014] Furthermore, the silane-modified polyether is prepared as follows:

[0015] Step 1: Cesium neopentanoate, allyl glycidyl ether and 2,5-furandiethanol are added to a high-pressure reactor under vacuum. After purging with nitrogen atmosphere, the mixture is stirred continuously at 100-120℃ for 18-26 hours to polymerize. After the reaction is completed, the prepolymer product is obtained.

[0016] Step 2: Add the prepolymerized product and 2-mercaptoimidazole to ethanol, irradiate with white LED light in air at room temperature for 6-12 hours, and then distill under reduced pressure to obtain the polymerized product with mercaptoimidazole introduced in the side chain.

[0017] Step 3: Under a nitrogen atmosphere, the polymerization product from step 2 and isocyanate-based silane are mixed to form a mixture. Dibutyltin dilaurate is added and stirred. The mixture is heated to 60-80℃ and reacted for 4-8 hours to obtain silane-modified polyether.

[0018] Under the action of a cesium catalyst, allyl glycidyl ether (containing olefins and epoxy groups) undergoes ring-opening polymerization with a small amount of 2,5-furandiethanol (as an initiator) to obtain a polyether with pendant groups and olefin side chains. Simultaneously, 2,5-furandiethanol is used to connect the polyether chain, introducing a furan ring. The olefin in the side chain undergoes an addition reaction with the thiol group on the 2-mercaptoimidazole, introducing the imidazole ring into the polymer side chain. Simultaneously, the hydroxyl groups at both ends of the polymerization product react with isocyanate-based silanes under the action of chelated tin to form urethane bonds, introducing hydrolyzable silanoxy groups. Upon contact with moisture in the air after application, the silanoxy groups undergo hydrolysis and condensation to form a Si-O-Si three-dimensional network structure, causing the coating to change from a liquid to a solid state, achieving moisture curing.

[0019] Furthermore, the molar ratio of cesium neopentanoate to allyl glycidyl ether is 1.0-1.2:1.

[0020] Furthermore, the molar ratio of the allyl glycidyl ether to 2,5-furandiethanol is 100-500:1.

[0021] Furthermore, the molar ratio of 2-mercaptoimidazole to allyl glycidyl ether is 0.5-0.8:1.

[0022] Further, the isocyanate-based silane is at least one selected from propyltriethoxysilane, 3-isocyanate-based propyltrimethoxysilane, and 3-propylisocyanate-based methyldiethoxysilane.

[0023] Furthermore, the isocyanate-based silane is 12-24% of the mass of allyl glycidyl ether.

[0024] Furthermore, the dibutyltin dilaurate accounts for 0.1-0.4% of the mass of the mixture.

[0025] Furthermore, the thixotropic agent is prepared as follows:

[0026] Isopropanol and water are mixed to form a mixed solvent. Acetic acid is added to adjust the pH to 4-5. Diethoxyphosphorylethyltriethoxysilane is added dropwise and stirred until hydrolysis is complete to obtain a hydrolysate. Fumed silica is added to water and ultrasonically dispersed to form a dispersion. The hydrolysate is added to the dispersion and mixed. The mixture is heated to 70-90℃ and stirred for 3-4 hours. After drying, modified fumed silica is obtained, which yields a thixotropic agent.

[0027] The phosphorus-containing silane coupling agent diethoxyphosphorylethyltriethoxysilane is hydrolyzed under acidic conditions to generate silanol, which is then mixed with an aqueous dispersion of fumed silica. The surface of the fumed silica is rich in silanols, which undergo a condensation reaction with the silanol from the hydrolyzed silane, thereby chemically grafting long organic chains containing phosphoryl groups onto the silica surface.

[0028] Furthermore, the volume ratio of isopropanol to water in the mixed solvent is 4-5:1.

[0029] Furthermore, the diethoxyphosphorylethyltriethoxysilane is 6-12% of the mass of the mixed solvent.

[0030] Furthermore, the concentration of fumed silica in the dispersion is 5-10%.

[0031] Furthermore, the hydrolysate and dispersion are mixed at a ratio of 8-14% of the mass of diethoxyphosphorylethyltriethoxysilane to the mass of fumed silica.

[0032] Furthermore, the filler is nano-calcium carbonate with a particle size of 40-60 nm.

[0033] Further, the coupling agent is at least one of γ-(2,3-epoxypropoxy)propyltrimethoxysilane and γ-(2,3-epoxypropoxy)propyltriethoxysilane.

[0034] Furthermore, the dehydrating agent is vinyltrimethoxysilane.

[0035] This invention also provides a method for preparing an anti-sagging and waterproof coating, which includes the following steps:

[0036] Step 1: Add silane-modified polyether, thixotropic agent and filler into a stirred reactor in proportion and stir to mix. Heat to 105-110℃ and dehydrate under vacuum for 2-3 hours.

[0037] Step 2: After dehydration, cool to room temperature under vacuum, add dehydrating agent and coupling agent, mix evenly to obtain anti-sagging waterproof coating.

[0038] The beneficial effects of this invention are:

[0039] (1) This invention uses silane-modified polyether containing imidazole rings as the core component of waterproof coating. Compared with traditional silane-modified polyether, the imidazole rings introduced can promote the hydrolysis and condensation of the terminal siloxanes, accelerate the curing of the coating, and after rapid cross-linking and curing, the coating loses its fluidity and remains stable under gravity. At the same time, the imidazole rings can form coordination or hydrogen bonding with the filler surface, enhance cohesion, improve the uniformity of the waterproof coating components, enhance the adhesion between the coating and the substrate, and prevent the coating from sagging after construction.

[0040] (2) Introducing fumed silica, a physical thixotropic agent, into the waterproof coating allows fumed silica to easily form a uniform three-dimensional network structure in the system. This three-dimensional network structure is destroyed under mechanical shear force, resulting in a decrease in viscosity and restoring good fluidity to the coating. When the shear force is removed, the three-dimensional structure recovers on its own, and the viscosity increases. Grafting phosphoryl siloxane onto the surface of fumed silica allows the modified silica to form strong ionic coordination bonds and hydrogen bonds with the imidazole groups in the silane-modified polyether through the phosphoryl groups on its surface. In a static state, these forces "lock" the resin, fillers, etc., in place, forming a robust, gel-like physical three-dimensional network that imparts extremely high viscosity to the coating and prevents sagging. Once subjected to construction shear force (such as brushing or rolling), these forces are instantly destroyed, the network disintegrates, the viscosity drops sharply, and good leveling properties are exhibited. After construction stops, the bonds recover rapidly, the network is rebuilt, and sagging is resisted again.

[0041] (4) Phosphoryl siloxane is grafted onto the surface of fumed silica. The long organic chain of phosphoryl siloxane improves the dispersibility of inorganic fumed silica in the organic system, making the coating components more uniform and preventing uneven thickness distribution during coating application, thus avoiding sagging caused by local accumulation.

[0042] (5) In the silane-modified polyether of the present invention, 2,5-furandiethanol is used in the polymerization reaction to introduce furan rings. The reactive furan rings endow the coating with potential self-healing ability and dynamic reversible cross-linking network, thereby improving the toughness, durability and comprehensive mechanical properties of the coating film. Detailed Implementation

[0043] 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.

[0044] Example 1

[0045] Preparation of silane-modified polyethers:

[0046] Step 1: Evacuate the high-pressure reactor and add cesium neopentanoate, allyl glycidyl ether, and 2,5-furandiethanol into the reactor through the feed port. The molar ratio of the raw materials is cesium neopentanoate: allyl glycidyl ether: 2,5-furandiethanol = 1.1:1:0.003. After purging the reactor with nitrogen atmosphere, continue stirring and polymerization at 110°C for 24 hours. After the reaction is completed, the prepolymerized product is obtained.

[0047] Step 2: Add the prepolymerized product to ethanol at a concentration of 10 g / L, then add 2-mercaptoimidazole. The molar ratio of 2-mercaptoimidazole to allyl glycidyl ether in Step 1 is 0.6:1. Irradiate with 10W white LED light for 10 h at room temperature in air atmosphere. After the reaction is completed, distill under reduced pressure to obtain the polymerized product with mercaptoimidazole introduced in the side chain.

[0048] Step 3: Under a nitrogen atmosphere, the polymerization product from Step 2 and 3-isocyanate-propyltrimethoxysilane are mixed to form a mixture, where the isocyanate-propyltrimethoxysilane is 18% of the mass of allyl glycidyl ether in Step 1. Then, dibutyltin dilaurate is added and stirred, where the dibutyltin dilaurate is 0.3% of the mass of the mixture. The mixture is heated to 70°C and reacted for 6 hours to obtain silane-modified polyether.

[0049] Preparation of thixotropic agents:

[0050] Isopropanol and water were mixed in a volume ratio of 5:1 to form a mixed solvent. Acetic acid was added to adjust the pH to 4.5. Diethoxyphosphorylethyltriethoxysilane was added dropwise, with the amount of diethoxyphosphorylethyltriethoxysilane being 10% of the mass of the mixed solvent. The mixture was stirred until clear and completely hydrolyzed to obtain a hydrolysate. Fumed silica was added to water and ultrasonically dispersed to form a dispersion with a concentration of 6%. The hydrolysate was added to the dispersion and mixed, with the mixing ratio being 12% of the mass of diethoxyphosphorylethyltriethoxysilane to the mass of fumed silica. The mixture was heated to 80°C and stirred for 3.5 h. After drying at 100°C for 6 h, modified fumed silica was obtained, yielding a thixotropic agent.

[0051] Preparation of waterproof coating:

[0052] Step 1: Prepare the raw materials according to the following proportions by weight: 40 parts silane-modified polyether, 8 parts thixotropic agent, 20 parts nano-calcium carbonate (particle size 40-60nm), 3 parts γ-(2,3-epoxypropoxy)propyltriethoxysilane, and 1 part vinyltrimethoxysilane. Add the silane-modified polyether, thixotropic agent, and nano-calcium carbonate to a stirred reactor in the specified proportions and mix. Heat to 110℃ and dehydrate under vacuum for 2 hours.

[0053] Step 2: After dehydration, cool to room temperature under vacuum, add γ-(2,3-epoxypropoxy)propyltriethoxysilane and vinyltrimethoxysilane and mix evenly to obtain an anti-sagging and waterproof coating.

[0054] Example 2

[0055] The only difference from Example 1 is that the molar ratio of 2-mercaptoimidazole to allyl glycidyl ether in step 1 is adjusted to 0.5:1 when preparing the silane-modified polyether. Other steps and conditions are the same as in Example 1.

[0056] Example 3

[0057] The only difference from Example 1 is that the molar ratio of 2-mercaptoimidazole to allyl glycidyl ether in step 1 is adjusted to 0.8:1 when preparing the silane-modified polyether. Other steps and conditions are the same as in Example 1.

[0058] Example 4

[0059] The only difference from Example 1 is that the molar ratio of the raw materials in preparing the silane-modified polyether is adjusted to cesium neopentanoate: allyl glycidyl ether: 2,5-furandiethanol = 1.0:1:0.01. Other steps and conditions are the same as in Example 1.

[0060] Example 5

[0061] The only difference from Example 1 is that the molar ratio of the raw materials in the preparation of the silane-modified polyether is adjusted to cesium neopentanoate: allyl glycidyl ether: 2,5-furandiethanol = 1.2:1:0.002. Other steps and conditions are the same as in Example 1.

[0062] Example 6

[0063] The only difference from Example 1 is that the mass of diethoxyphosphorylethyltriethoxysilane used in the preparation of the thixotropic agent is 8% of the mass of fumed silica. All other steps and conditions are the same as in Example 1.

[0064] Example 7

[0065] The only difference from Example 1 is that the mass of diethoxyphosphorylethyltriethoxysilane in the preparation of the thixotropic agent is 14% of the mass of fumed silica. Other steps and conditions are the same as in Example 1.

[0066] Examples 8-9

[0067] The only difference from Example 1 is the proportion of raw materials used in preparing the waterproof coating. All other steps and conditions are the same as in Example 1. Specific proportions are shown in Table 1.

[0068] Table 1

[0069]

[0070] Comparative Example 1

[0071] The only difference from Example 1 is that 2-mercaptoimidazole is not added during the preparation of the silane-modified polyether.

[0072] Preparation of silane-modified polyethers:

[0073] Step 1: Evacuate the high-pressure reactor and add cesium neopentanoate, allyl glycidyl ether, and 2,5-furandiethanol into the reactor through the feed port. The molar ratio of the raw materials is cesium neopentanoate: allyl glycidyl ether: 2,5-furandiethanol = 1.1:1:0.003. After purging the reactor with nitrogen atmosphere, continue stirring and polymerization at 110°C for 24 hours. After the reaction is completed, the prepolymerized product is obtained.

[0074] Step 2: Under a nitrogen atmosphere, the prepolymer product and 3-isocyanate-propyltrimethoxysilane are mixed to form a mixture, where the isocyanate-propyltrimethoxysilane is 18% of the mass of allyl glycidyl ether in Step 1. Then, dibutyltin dilaurate is added and stirred, where the dibutyltin dilaurate is 0.3% of the mass of the mixture. The mixture is heated to 70°C and reacted for 6 hours to obtain silane-modified polyether.

[0075] Preparation of thixotropic agents:

[0076] Isopropanol and water were mixed in a volume ratio of 5:1 to form a mixed solvent. Acetic acid was added to adjust the pH to 4.5. Diethoxyphosphorylethyltriethoxysilane was added dropwise, with the amount of diethoxyphosphorylethyltriethoxysilane being 10% of the mass of the mixed solvent. The mixture was stirred until clear and completely hydrolyzed to obtain a hydrolysate. Fumed silica was added to water and ultrasonically dispersed to form a dispersion with a concentration of 6%. The hydrolysate was added to the dispersion and mixed, with the mixing ratio being 12% of the mass of diethoxyphosphorylethyltriethoxysilane to the mass of fumed silica. The mixture was heated to 80°C and stirred for 3.5 h. After drying at 100°C for 6 h, modified fumed silica was obtained, yielding a thixotropic agent.

[0077] Preparation of waterproof coating:

[0078] Step 1: Prepare the raw materials according to the following proportions by weight: 40 parts silane-modified polyether, 8 parts thixotropic agent, 20 parts nano-calcium carbonate (particle size 40-60nm), 3 parts γ-(2,3-epoxypropoxy)propyltriethoxysilane, and 1 part vinyltrimethoxysilane. Add the silane-modified polyether, thixotropic agent, and nano-calcium carbonate to a stirred reactor in the specified proportions and mix. Heat to 110℃ and dehydrate under vacuum for 2 hours.

[0079] Step 2: After dehydration, cool to room temperature under vacuum, add γ-(2,3-epoxypropoxy)propyltriethoxysilane and vinyltrimethoxysilane and mix evenly to obtain an anti-sagging and waterproof coating.

[0080] Comparative Example 2

[0081] The only difference from Example 1 is that 1,4-terephthalic acid is used instead of 2,5-furandiethanol when preparing the silane-modified polyether.

[0082] Preparation of silane-modified polyethers:

[0083] Step 1: Evacuate the high-pressure reactor and add cesium neopentanoate, allyl glycidyl ether, and 1,4-terephthalic acid into the reactor through the feed port. The molar ratio of the raw materials is cesium neopentanoate: allyl glycidyl ether: 1,4-terephthalic acid = 1.1:1:0.003. After purging the reactor with nitrogen atmosphere, continue stirring and polymerizing at 110°C for 24 hours. After the reaction is completed, the prepolymerized product is obtained.

[0084] Step 2: Add the prepolymerized product to ethanol at a concentration of 10 g / L, then add 2-mercaptoimidazole. The molar ratio of 2-mercaptoimidazole to allyl glycidyl ether in Step 1 is 0.6:1. Irradiate with 10W white LED light for 10 h at room temperature in air atmosphere. After the reaction is completed, distill under reduced pressure to obtain the polymerized product with mercaptoimidazole introduced in the side chain.

[0085] Step 3: Under a nitrogen atmosphere, the polymerization product from Step 2 and 3-isocyanate-propyltrimethoxysilane are mixed to form a mixture, where the isocyanate-propyltrimethoxysilane is 18% of the mass of allyl glycidyl ether in Step 1. Then, dibutyltin dilaurate is added and stirred, where the dibutyltin dilaurate is 0.3% of the mass of the mixture. The mixture is heated to 70°C and reacted for 6 hours to obtain silane-modified polyether.

[0086] Preparation of thixotropic agents:

[0087] Isopropanol and water were mixed in a volume ratio of 5:1 to form a mixed solvent. Acetic acid was added to adjust the pH to 4.5. Diethoxyphosphorylethyltriethoxysilane was added dropwise, with the amount of diethoxyphosphorylethyltriethoxysilane being 10% of the mass of the mixed solvent. The mixture was stirred until clear and completely hydrolyzed to obtain a hydrolysate. Fumed silica was added to water and ultrasonically dispersed to form a dispersion with a concentration of 6%. The hydrolysate was added to the dispersion and mixed, with the mixing ratio being 12% of the mass of diethoxyphosphorylethyltriethoxysilane to the mass of fumed silica. The mixture was heated to 80°C and stirred for 3.5 h. After drying at 100°C for 6 h, modified fumed silica was obtained, yielding a thixotropic agent.

[0088] Preparation of waterproof coating:

[0089] Step 1: Prepare the raw materials according to the following proportions by weight: 40 parts silane-modified polyether, 8 parts thixotropic agent, 20 parts nano-calcium carbonate (particle size 40-60nm), 3 parts γ-(2,3-epoxypropoxy)propyltriethoxysilane, and 1 part vinyltrimethoxysilane. Add the silane-modified polyether, thixotropic agent, and nano-calcium carbonate to a stirred reactor in the specified proportions and mix. Heat to 110℃ and dehydrate under vacuum for 2 hours.

[0090] Step 2: After dehydration, cool to room temperature under vacuum, add γ-(2,3-epoxypropoxy)propyltriethoxysilane and vinyltrimethoxysilane and mix evenly to obtain an anti-sagging and waterproof coating.

[0091] Comparative Example 3

[0092] The only difference from Example 1 is that propylene oxide is used instead of allyl glycidyl ether. Preparation of silane-modified polyether:

[0093] Step 1: Evacuate the high-pressure reactor and add cesium neopentanoate, propylene oxide, and 2,5-furandimethyl alcohol through the feed port. The molar ratio of the raw materials is cesium neopentanoate:propylene oxide:2,5-furandimethyl alcohol = 1.1:1:0.003. After replacing the atmosphere with nitrogen, continue stirring the polymerization reaction at 110°C for 24 hours. After the reaction is completed, the prepolymerized product is obtained.

[0094] Step 2: Under a nitrogen atmosphere, the prepolymer product and 3-isocyanate-propyltrimethoxysilane are mixed to form a mixture, where the isocyanate-propyltrimethoxysilane is 18% of the mass of propylene oxide in Step 1. Then, dibutyltin dilaurate is added and stirred, where the dibutyltin dilaurate is 0.3% of the mass of the mixture. The mixture is heated to 70°C and reacted for 6 hours to obtain silane-modified polyether.

[0095] Preparation of thixotropic agents:

[0096] Isopropanol and water were mixed in a volume ratio of 5:1 to form a mixed solvent. Acetic acid was added to adjust the pH to 4.5. Diethoxyphosphorylethyltriethoxysilane was added dropwise, with the amount of diethoxyphosphorylethyltriethoxysilane being 10% of the mass of the mixed solvent. The mixture was stirred until clear and completely hydrolyzed to obtain a hydrolysate. Fumed silica was added to water and ultrasonically dispersed to form a dispersion with a concentration of 6%. The hydrolysate was added to the dispersion and mixed, with the mixing ratio being 12% of the mass of diethoxyphosphorylethyltriethoxysilane to the mass of fumed silica. The mixture was heated to 80°C and stirred for 3.5 h. After drying at 100°C for 6 h, modified fumed silica was obtained, yielding a thixotropic agent.

[0097] Preparation of waterproof coating:

[0098] Step 1: Prepare the raw materials according to the following proportions by weight: 40 parts silane-modified polyether, 8 parts thixotropic agent, 20 parts nano-calcium carbonate (particle size 40-60nm), 3 parts γ-(2,3-epoxypropoxy)propyltriethoxysilane, and 1 part vinyltrimethoxysilane. Add the silane-modified polyether, thixotropic agent, and nano-calcium carbonate to a stirred reactor in the specified proportions and mix. Heat to 110℃ and dehydrate under vacuum for 2 hours.

[0099] Step 2: After dehydration, cool to room temperature under vacuum, add γ-(2,3-epoxypropoxy)propyltriethoxysilane and vinyltrimethoxysilane and mix evenly to obtain an anti-sagging and waterproof coating.

[0100] Comparative Example 4

[0101] The only difference from Example 1 is that fumed silica is used directly as the thixotropic agent.

[0102] Preparation of silane-modified polyethers:

[0103] Step 1: Evacuate the high-pressure reactor and add cesium neopentanoate, allyl glycidyl ether, and 2,5-furandiethanol into the reactor through the feed port. The molar ratio of the raw materials is cesium neopentanoate: allyl glycidyl ether: 2,5-furandiethanol = 1.1:1:0.003. After purging the reactor with nitrogen atmosphere, continue stirring and polymerization at 110°C for 24 hours. After the reaction is completed, the prepolymerized product is obtained.

[0104] Step 2: Add the prepolymerized product to ethanol at a concentration of 10 g / L, then add 2-mercaptoimidazole. The molar ratio of 2-mercaptoimidazole to allyl glycidyl ether in Step 1 is 0.6:1. Irradiate with 10W white LED light for 10 h at room temperature in air atmosphere. After the reaction is completed, distill under reduced pressure to obtain the polymerized product with mercaptoimidazole introduced in the side chain.

[0105] Step 3: Under a nitrogen atmosphere, the polymerization product from Step 2 and 3-isocyanate-propyltrimethoxysilane are mixed to form a mixture, where the isocyanate-propyltrimethoxysilane is 18% of the mass of allyl glycidyl ether in Step 1. Then, dibutyltin dilaurate is added and stirred, where the dibutyltin dilaurate is 0.3% of the mass of the mixture. The mixture is heated to 70°C and reacted for 6 hours to obtain silane-modified polyether.

[0106] Preparation of waterproof coating:

[0107] Step 1: Prepare the raw materials according to the following proportions by weight: 40 parts silane-modified polyether, 8 parts fumed silica, 20 parts nano-calcium carbonate (particle size 40-60nm), 3 parts γ-(2,3-epoxypropoxy)propyltriethoxysilane, and 1 part vinyltrimethoxysilane. Add the silane-modified polyether, fumed silica, and nano-calcium carbonate to a stirred reactor in the specified proportions and mix. Heat to 110℃ and dehydrate under vacuum for 2 hours.

[0108] Step 2: After dehydration, cool to room temperature under vacuum, add γ-(2,3-epoxypropoxy)propyltriethoxysilane and vinyltrimethoxysilane and mix evenly to obtain an anti-sagging and waterproof coating.

[0109] The performance of the waterproof coatings prepared in Examples 1-9 and Comparative Examples 1-4 was tested, and the results are shown in Table 2.

[0110] The reference standard for anti-sagging properties is "T / CECS 10302-2023 Anti-sagging Polyurethane Waterproof Coating", with a wet film thickness of 2.5mm and a test for sagging length.

[0111] Table 2

[0112]

[0113] As shown in Table 2, the content of imidazole groups in the silane-modified polyether affects the crosslinking and curing rate of the coating. Rapid crosslinking and curing can prevent coating sagging. Among Examples 1-3, Example 1 has the best anti-sagging performance. Examples 4 and 5 adjust the proportion of 2,5-furandiethanol in the polymerization reaction based on Example 1. 2,5-furandiethanol can promote the ring-opening polymerization reaction and affect the molecular weight of the polymer. In Example 4, the amount of allyl glycidyl ether monomer is relatively small, which limits the molecular weight of the polymer. In Example 5, the amount of 2,5-furandiethanol is too small, which also limits the ring-opening polymerization. The waterproof coating of Example 1 has better performance than that of Examples 4 and 5. The waterproof coatings prepared in the examples of this invention have excellent anti-sagging performance and can ensure a good appearance of the coating after scraping.

[0114] 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.

[0115] 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 sagging and waterproof coating, characterized in that, The product comprises, by weight parts, the following raw materials: 30-50 parts of silane-modified polyether, 5-10 parts of thixotropic agent, 15-25 parts of filler, 1-5 parts of coupling agent, and 0.5-2 parts of dehydrating agent; wherein mercaptoimidazole is introduced into the side chain of the polyether chain of the silane-modified polyether. The thixotropic agent is a phosphoryl siloxane grafted onto the surface of fumed silica; the silane-modified polyether is prepared by the following method: Step 1, Cesium neopentanoate, allyl glycidyl ether and 2,5-furandiethanol are added to a high-pressure reactor under vacuum, and after replacing the nitrogen atmosphere, the mixture is continuously stirred and polymerized at 100-120℃ for 18-26h. After the reaction, a prepolymer product is obtained; Step 2, The prepolymer product and 2-mercaptoimidazole are added to ethanol, and irradiated with white LED light at room temperature air atmosphere for 6-12h. After the reaction, the polymer product with mercaptoimidazole side chain is obtained by vacuum distillation; Step 3, The polymer product of Step 2 and isocyanate-based silane are mixed under nitrogen atmosphere to form a mixture, and dibutyltin dilaurate is added and stirred. The mixture is heated to 60-80℃ and reacted continuously for 4-8h to obtain the silane-modified polyether.

2. The anti-sagging and waterproof coating according to claim 1, characterized in that, The molar ratio of cesium neopentanoate to allyl glycidyl ether is 1.0-1.2:

1.

3. The anti-sagging and waterproof coating according to claim 1, characterized in that, The molar ratio of allyl glycidyl ether to 2,5-furandiethanol is 100-500:1; the molar ratio of 2-mercaptoimidazole to allyl glycidyl ether is 0.5-0.8:

1.

4. The anti-sagging and waterproof coating according to claim 1, characterized in that, The isocyanate-based silane is at least one selected from propyltriethoxysilane, 3-isocyanate-based propyltrimethoxysilane, and 3-isocyanate-based methyldiethoxysilane; the isocyanate-based silane is 12-24% of the mass of allyl glycidyl ether.

5. The anti-sagging and waterproof coating according to claim 1, characterized in that, The thixotropic agent is prepared by the following method: isopropanol and water are mixed to form a mixed solvent, acetic acid is added to adjust the pH to 4-5, diethoxyphosphorylethyltriethoxysilane is added dropwise, and the mixture is stirred until hydrolysis is complete to obtain a hydrolysate. Fumed silica is added to water and ultrasonically dispersed to form a dispersion. The hydrolysate is added to the dispersion and mixed. The mixture is heated to 70-90℃ and stirred for 3-4 hours. After drying, modified fumed silica is obtained, and the thixotropic agent is obtained.

6. The anti-sagging and waterproof coating according to claim 5, characterized in that, The diethoxyphosphorylethyltriethoxysilane is 6-12% of the mass of the mixed solvent; the concentration of fumed silica in the dispersion is 5-10%; the hydrolysate and the dispersion are mixed at a mass of diethoxyphosphorylethyltriethoxysilane of 8-14% of the mass of fumed silica.

7. The anti-sagging and waterproof coating according to claim 1, characterized in that, The filler is nano-calcium carbonate with a particle size of 40-60 nm.

8. The anti-sagging and waterproof coating according to claim 1, characterized in that, The coupling agent is at least one of γ-(2,3-epoxypropoxy)propyltrimethoxysilane and γ-(2,3-epoxypropoxy)propyltriethoxysilane; the dehydrating agent is vinyltrimethoxysilane.

9. A method for preparing an anti-sagging and waterproof coating, characterized in that, The preparation of the anti-sagging and waterproof coating as described in any one of claims 1-8 includes the following steps: Step 1, adding silane-modified polyether, thixotropic agent and filler into a stirred reactor in proportion and stirring to mix, heating to 105-110℃ and dehydrating under vacuum for 2-3 hours; Step 2, after dehydration, cooling to room temperature under vacuum, adding dehydrating agent and coupling agent and mixing evenly to obtain the anti-sagging and waterproof coating.

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