Low-temperature-resistant waterproof coating for outer wall of house building and preparation process thereof

Abstract

The application relates to the technical field of paint, and particularly discloses a low-temperature-resistant waterproof paint for a house building outer wall and a preparation process thereof, which is prepared from the following raw materials in parts by mass: modified silicon-acrylic emulsion 200-250 parts, polyurethane-acrylate core-shell emulsion 75-125 parts, polyether polyol modified nano filler 40-60 parts, rubber nano powder 15-25 parts, liquid polyisoprene 10-20 parts, auxiliary agent 22-34 parts and composite solvent 60-100 parts. The low-temperature-resistant waterproof paint prepared by the application can significantly improve the elongation at break and low-temperature bending resistance of the coating film under the premise of maintaining good tensile strength and adhesion.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of coatings, in particular to a low-temperature-resistant waterproof coating for the outer wall of a house building and a preparation process thereof. BACKGROUND

[0002] Waterproofing of the outer wall is a key link to ensure the durability and safety of the building structure, especially in the northern region, the climate conditions pose a very severe challenge to the waterproofing system. The long winter is accompanied by continuous low temperature, frequent freeze-thaw cycle and extreme weather such as strong wind and snow, which requires the waterproof coating to have weather resistance, flexibility and freeze-thaw stability far beyond that in the southern region. Traditional outer wall waterproof coatings, such as asphalt-based and ordinary acrylic products, have a glass transition temperature (Tg) of the polymer chain segment usually higher than 0℃, which shows rigidity at room temperature, but once the environmental temperature drops below its Tg, the molecular chain segment movement is frozen, and the material will change from high elasticity to glass state, thus losing flexibility. This change directly shows that the coating film becomes hard and brittle at low temperature, and when it encounters slight thermal expansion and contraction or frost heaving stress of the substrate, it is easy to cause brittle cracking, peeling off and other problems. Once the waterproof layer fails, water will enter the wall, which not only causes the inner wall to be damp and the finish to be moldy, but more seriously, when water penetrates into the concrete, it will cause corrosion and frost heaving damage to the internal steel bars, thus endangering the safety and service life of the building from the structural level.

[0003] The patent application file with the publication number CN119570324A discloses a nano high and low temperature resistant acid and alkali resistant anticorrosive waterproof coating, which comprises the following raw materials in parts by mass: pure acrylic emulsion 30-40 parts, modified nano silicon dioxide 10-20 parts, nano titanium dioxide 2-4 parts, nano zinc oxide 3-6 parts, additives 2-4.4 parts, and water 5-9 parts. The modified nano silicon dioxide is nano silicon dioxide modified by a modifier, and the modifier comprises a dibasic ester and / or a dibasic alcohol.

[0004] In this scheme, although the nano silicon dioxide is modified by the dibasic ester and / or the dibasic alcohol, the material compatibility is improved to some extent, but the total amount of the inorganic phase in the formula is relatively high, which will increase the brittleness of the coating film and reduce the elongation at break. Especially in the low temperature environment in the north, such brittleness trend will be further intensified, which will affect the mechanical properties and long-term durability of the coating film. In addition, the system only uses pure acrylic emulsion as the film-forming material, which is still insufficient in maintaining the frost resistance and flexibility, and it is difficult to fully meet the use requirements under the condition of extreme temperature alternation. SUMMARY

[0005] In order to overcome the problems of high inorganic nano-material dosage, single film-forming material, large coating film brittleness, low temperature toughness and the like in the prior art, and further improve the mechanical properties and low temperature resistance of the waterproof coating, the application provides a low-temperature-resistant waterproof coating for a housing building outer wall and a preparation process thereof.

[0006] In a first aspect, the application provides a low-temperature-resistant waterproof coating for a housing building outer wall, which adopts the following technical scheme:

[0007] A low-temperature-resistant waterproof coating for a housing building outer wall is prepared from the following raw materials by mass fraction:

[0008] The modified silicone-acrylate emulsion 200-250 parts, the polyurethane-acrylate core-shell emulsion 75-125 parts, the polyether polyol modified nano filler 40-60 parts, the rubber nano powder 15-25 parts, the liquid polyisoprene 10-20 parts, the auxiliary agent 22-34 parts and the composite solvent 60-100 parts;

[0009] The modified silicone-acrylate emulsion is specifically prepared by pre-polymerization of a double-bond-containing polyhydroxy compound and a double-bond-containing silane coupling agent, and then copolymerization with monomer A and vinyl fluorosilicone oil.

[0010] The polyurethane-acrylate core-shell emulsion is specifically prepared by pre-polymerization of a polyether polyol, an isocyanate and a carboxyl-containing hydrophilic monomer, and then copolymerization with monomer B.

[0011] In this scheme, the modified silicone-acrylate emulsion and the polyurethane-acrylate core-shell emulsion are used together to form a strong and tough-elastic composite matrix, the polyether polyol modified nano filler realizes the rigid-flexible synergistic reinforcing effect through a flexible interface, and at the same time, the rubber nano powder and the liquid polyisoprene cooperatively construct a multi-scale stress dissipation network to ensure excellent elasticity and durability of the coating in a low temperature environment.

[0012] Preferably, the solid content of the modified silicone-acrylate emulsion is 50%-55%.

[0013] Preferably, the solid content of the polyurethane-acrylate core-shell emulsion is 50%-55%.

[0014] Preferably, the composite solvent comprises water and an organic solvent.

[0015] Preferably, the mass ratio of the water and the organic solvent is 1: (1-1.5).

[0016] Preferably, the organic solvent comprises propylene glycol methyl ether and isopropyl alcohol.

[0017] Preferably, the preparation method of the modified silicone-acrylate emulsion comprises the following steps:

[0018] After the composite solvent and the emulsifier are mixed evenly under inert atmosphere, the double-bond-containing polyhydroxyl compound and the double-bond-containing silane coupling agent are mixed evenly, the temperature is raised to 70-90℃, part of the initiator is added, the reaction is carried out for 60-90 min, then the monomer A, the vinyl fluorosilicone oil and the remaining initiator are added, the temperature is kept for 4-5 h, vacuum distillation is carried out, and after cooling and adjustment of the solid content, the modified silicone-acrylic emulsion is obtained.

[0019] In the present scheme, in the prepolymerization stage, the double-bond-containing polyhydroxyl compound and the double-bond-containing silane coupling agent are copolymerized by free radicals to form a prepolymer having polymerizable double bonds, hydroxyl groups and hydrolyzable alkoxy groups, which lays a foundation for subsequent copolymerization and interfacial bonding; in the copolymerization stage, the prepolymer is further copolymerized with the acrylic ester monomer and the vinyl fluorosilicone oil, and finally a composite emulsion having a unique microstructure is obtained - among which, the organosiloxane chain segment enhances the molecular chain flexibility, the groups of the vinyl fluorosilicone oil impart the coating film with persistent hydrophobicity through surface migration effect, and the abundant hydroxyl groups provide a large number of hydrogen bonding sites for the system. This enables the emulsion to form strong interactions with the active groups in the core-shell emulsion and to produce interfacial bonding with modified nano fillers and other components in the subsequent coating film formation process, and to jointly build a stable three-dimensional network structure, thereby significantly improving the low-temperature toughness, adhesion and durability of the coating film.

[0020] Preferably, the mass ratio of the double-bond-containing polyhydroxyl compound, the double-bond-containing silane coupling agent, the monomer A and the vinyl fluorosilicone oil is (32-48):(12-40):(300-340):(20-32).

[0021] Preferably, the double-bond-containing polyhydroxyl compound is any one of trimethylolpropane diallyl ether and pentaerythritol triallyl ether.

[0022] Preferably, the double-bond-containing silane coupling agent is any one of vinyltrimethoxysilane and vinyltriethoxysilane.

[0023] Preferably, the monomer A includes butyl acrylate, monobutyl maleate and dodecafluoroheptyl methacrylate.

[0024] Preferably, the mass ratio of the butyl acrylate, the monobutyl maleate and the dodecafluoroheptyl methacrylate is (240-260):(20-30):(40-50).

[0025] Preferably, the initiator is ammonium persulfate or potassium persulfate.

[0026] Preferably, the amount of the initiator is 0.8%-1.2% of the total mass of the double-bond-containing polyhydroxyl compound, the double-bond-containing silane coupling agent, the monomer A and the vinyl fluorosilicone oil.

[0027] Preferably, the preparation method of the polyurethane-acrylate core-shell emulsion comprises the following steps:

[0028] Under an inert atmosphere, polyether polyol, isocyanate, carboxyl-containing hydrophilic monomer, catalyst and acetone are added to the reactor, heated to 60-80℃, reacted for 2-4h, cooled, adjusted to pH 7.5-8.0, added to water containing emulsifier, mixed uniformly, heated to 70-90℃, monomer B and initiator are added, incubated for 2.5-3.5h, distilled under reduced pressure, cooled, and then adjusted to the solid content to obtain the polyurethane-acrylate core-shell emulsion.

[0029] Preferably, the mass ratio of the polyether polyol, isocyanate, carboxyl-containing hydrophilic monomer and monomer B is (50-60):(25-35):(3-4):(40-60).

[0030] Preferably, the carboxyl-containing hydrophilic monomer is dimethylol propionic acid.

[0031] Preferably, the monomer B includes butyl acrylate, methyl methacrylate and maleic acid monobutyl ester.

[0032] Preferably, the mass ratio of the butyl acrylate, methyl methacrylate and maleic acid monobutyl ester is (25-30):(10-20):(5-10).

[0033] Preferably, the initiator is ammonium persulfate or potassium persulfate.

[0034] Preferably, the amount of the initiator is 0.8%-1.2% of the mass of monomer B.

[0035] In this scheme, under an inert atmosphere, first, polyurethane prepolymer is formed by taking polyether polyol and isocyanate as core raw materials, and a high-elasticity core layer is constructed to lay the foundation for low-temperature resistance and crack resistance; then, monomer B and initiator are added for copolymerization to form an acrylate shell layer on the surface of the polyurethane prepolymer particles. Among them, methyl methacrylate as a rigid monomer gives the shell layer hardness and strength, butyl acrylate as a flexible monomer guarantees the toughness of the shell layer, and the carboxyl provided by maleic acid monobutyl ester not only stabilizes the latex particles, but also can be used as a reaction site for subsequent bonding with carbodiimide, thereby strengthening the core-shell interface and participating in the construction of the overall crosslinking network of the coating film, and achieving the dual performance of low-temperature resistance and high strength.

[0036] Preferably, the preparation method of the polyether polyol modified nano filler comprises the following steps:

[0037] Under an inert atmosphere, the acidified nano filler is uniformly dispersed in an organic solvent, a catalyst is added and mixed uniformly, then polyether polyol is added and mixed uniformly, heated to 80-100℃, reacted for 4-6h, cooled, solid-liquid separated, washed, and dried to obtain the polyether polyol modified nano filler.

[0038] Preferably, the acidified nano-filler is specifically acidified by dilute nitric acid.

[0039] Further preferably, the preparation method of the acidified nano-filler comprises the following steps:

[0040] The nano-filler is immersed in dilute nitric acid with a mass fraction of 10% to 12% at 55 to 60℃ for 2 to 3 hours, solid-liquid separation, washing, and drying to obtain the acidified nano-filler.

[0041] Preferably, the mass fraction of the dilute nitric acid is 10% to 12%.

[0042] Preferably, in the acidified nano-filler, the nano-filler comprises nano-silica and nano-attapulgite.

[0043] In this scheme, the nano-silica and nano-attapulgite are simultaneously modified by polyether polyol. The long molecular chain not only enhances the binding force with the polymer matrix through physical entanglement, but also constructs a flexible buffer layer between the inorganic nanoparticles and the organic matrix. Among them, the spherical nano-silica mainly provides rigidity and reinforcement, while the fibrous nano-attapulgite can interweave with each other in the coating, producing synergistic toughening and thixotropic effect. This composite nano-filler system not only realizes nano-enhancement, but also significantly improves the elongation at break, impact resistance and sag resistance of the coating film at low temperature.

[0044] Preferably, the mass ratio of the nano-silica to the nano-attapulgite is (1 to 3):1.

[0045] Preferably, the amount of the polyether polyol is 20% to 40% of the mass of the nano-filler.

[0046] Preferably, the polyether polyol is any one of polytetrahydrofuran diol and polyoxypropylene diol.

[0047] Further preferably, the polyether polyol is polytetrahydrofuran diol.

[0048] Preferably, the particle size distribution of the nano-silica is 10 to 50 nm.

[0049] Preferably, the fiber diameter of the nano-attapulgite is 20 to 50 nm, and the fiber length is 0.5 to 5 μm.

[0050] Preferably, the amount of the catalyst is 0.4% to 0.5% of the mass of the polyether polyol.

[0051] Preferably, the catalyst is dibutyltin dilaurate.

[0052] Preferably, the auxiliary agent comprises dispersants, antifoaming agents, thickening agents, film forming agents, preservatives and ultraviolet absorbers.

[0053] Preferably, the film forming agent is dodecanol ester.

[0054] Preferably, the rubber nano powder is nitrile rubber nano powder or chlorobutyl rubber nano powder.

[0055] Preferably, the particle size distribution of the rubber nano powder is 50-200 nm.

[0056] In this scheme, the nitrile rubber nano powder or chlorobutyl rubber nano powder and the elastic core of the polyurethane-acrylate core-shell emulsion and the flexible segment of the liquid polyisoprene are synergistic, forming a multi-scale stress buffer system in the coating film, which can effectively terminate and disperse microcracks, further improving the anti-fatigue and impact resistance of the coating film under dynamic load.

[0057] Preferably, the low-temperature-resistant waterproof coating for building exterior walls further comprises 1-2 parts by mass of carbodiimide.

[0058] In this scheme, by adding a specific water-based carbodiimide, the carbodiimide functional group can be mildly bonded with the residual carboxyl groups in the polymer system, significantly enhancing the interfacial bonding force between the phases, improving the compactness and cohesion of the coating film, thereby more effectively dispersing and absorbing stress, and synergistically improving the water resistance, mechanical strength and durability of the coating film.

[0059] Preferably, the low-temperature-resistant waterproof coating for building exterior walls further comprises 3-5 parts by mass of microsilica or / and calcined kaolin.

[0060] Further preferably, the microsilica or / and calcined kaolin is pretreated before use by the following steps:

[0061] S11: Add an ethanol aqueous solution of silane coupling agent into the reactor, adjust the pH to 4.5-5.0, heat to 50-55℃, hydrolyze for 60-70 min, and obtain a pretreated liquid;

[0062] S12: Mix the pretreated liquid with microsilica or / and calcined kaolin at a solid-liquid mass ratio of (1.2-1.5):1, dry and disperse, and obtain the product.

[0063] Preferably, the particle size D50 of the microsilica is 0.1-5 μm.

[0064] Preferably, the particle size D50 of the calcined kaolin is 1-10 μm.

[0065] In the scheme, the spherical particles of micro-silicon powder achieve relatively dense physical filling, laying the foundation for high strength and shielding property of the coating film; the sheet structure of calcined kaolin is arranged in a direction to form a labyrinth barrier effect. The key is that the surface modification layer forms a firm transition interface between the rigid filler and the flexible polymer matrix, which not only improves the dispersibility, but also effectively transmits and disperses the external stress in the reinforcing skeleton, thereby synchronously achieving the comprehensive improvement of the strength, toughness, deformation resistance and durability of the coating film.

[0066] In a second aspect, the application further provides a preparation process of a low-temperature-resistant waterproof coating for a building exterior wall, comprising the following steps:

[0067] S1: uniformly mixing a composite solvent, a first part of an auxiliary agent and a polyether polyol modified nano filler to obtain a uniform slurry;

[0068] S2: uniformly mixing rubber nano powder and liquid polyisoprene to obtain an elastomer blend;

[0069] S3: uniformly mixing a modified silicone-acrylate emulsion and a polyurethane-acrylate core-shell emulsion, then uniformly mixing the uniform slurry, the elastomer blend and a second part of the auxiliary agent, adjusting the solid content, and then adding the remaining auxiliary agent and adjusting the pH to 7.5-8.5 to obtain the low-temperature-resistant waterproof coating.

[0070] In the scheme, the preparation process ensures the uniform dispersion and stable existence of each functional component in the system by preparing the uniform slurry and the elastomer blend first and then mixing them with the composite emulsion in steps, thereby avoiding problems such as agglomeration and poor compatibility that may be caused by direct mixing of multiple components, and thus ensuring the uniformity of the microstructure of the final coating film and the reliability of the performance.

[0071] Preferably, after adjusting the pH in step S3, a step of adding carbodiimide is further included.

[0072] Preferably, after adding the polyether polyol modified nano filler in step S1, a step of adding micro-silicon powder or / and calcined kaolin is further included.

[0073] In summary, the application has the following beneficial effects:

[0074] The application uses a modified silicone-acrylate emulsion and a polyurethane-acrylate core-shell emulsion as a film-forming matrix to provide a continuous phase with rigidity and flexibility, and the toughening and reinforcing network constructed by the rubber nano powder, the liquid polyisoprene and the nano filler modified by the flexible interface of the polyether polyol are interpenetrated, which can effectively disperse stress under external force or low temperature, and impart the coating film with high elongation at break and low-temperature flexibility. DETAILED DESCRIPTION

[0075] The application will be further described in detail below with reference to the examples.

[0076] In the following preparation examples and examples, the specifications of raw materials are as follows:

[0077] The particle size distribution of the nano-silicon dioxide is 10-50 nm; the fiber diameter of the nano-attapulgite is 20-50 nm, and the fiber length is 0.5-5 μm; the particle size distribution of the nitrile rubber nano-powder is 50-200 nm; the particle size distribution of the chloroprene rubber nano-powder is 50-200 nm; the particle size D50 of the micro-silicon powder is 0.1-5 μm; and the particle size D50 of the calcined kaolin is 1-10 μm.

[0078] The number average molecular weight of the polytetrahydrofuran diol is 2000 g / mol; the number average molecular weight of the polyoxypropylene diol is 1000 g / mol; and the number average molecular weight of the liquid polyisoprene is 25000-50000 g / mol.

[0079] The raw materials of the examples and comparative examples of the application are all ordinary commercially available products except for special instructions.

[0080] Preparation examples 1-3 of modified silicone-acrylate emulsion

[0081] Preparation example 1

[0082] The preparation method of the modified silicone-acrylate emulsion of the present preparation example comprises the following steps:

[0083] Under a nitrogen atmosphere, 100 g of deionized water, 50 g of isopropyl alcohol, 50 g of propylene glycol methyl ether, 2 g of emulsifier DNS-86 and 2 g of emulsifier CO-897 were added into a reaction kettle, stirred and mixed uniformly at a rotation speed of 300 r / min, 32 g of trimethylolpropane diallyl ether and 12 g of vinyl trimethoxysilane were added, stirred and mixed for 20 min, heated to 70℃, and an ammonium persulfate solution (1.6 g of ammonium persulfate was previously dissolved in 10 g of deionized water) was added, stirred at a rotation speed of 200 r / min for 90 min, and the following two materials were synchronously and uniformly added through two constant-pressure dropping funnels:

[0084] Pre-emulsion: 240 g of butyl acrylate, 20 g of maleic acid monobutyl ester, 40 g of methacrylic acid dodecafluoroheptyl ester and 20 g of vinyl fluorosilicone oil were added into a stirrer and stirred and mixed uniformly;

[0085] Ammonium persulfate solution: 2.8 g of ammonium persulfate was previously dissolved in 20 g of deionized water;

[0086] The dropping time is about 3 h, and the temperature is controlled at 70 ℃ during the dropping. After the dropping is completed, the temperature is increased to 80 ℃, and the system is kept at 80 ℃ for 2 h. Then, the system is cooled to 55 ℃, and vacuum distillation is performed under a vacuum degree of -0.08 MPa until no distillate is discharged. The system is cooled to 40 ℃, filtered, and adjusted to a solid content of 55% by using deionized water to obtain the modified silicone-acrylate emulsion.

[0087] Preparation Example 2

[0088] The preparation method of the modified silicone-acrylate emulsion of the present preparation example comprises the following steps:

[0089] Under a nitrogen atmosphere, 100 g of deionized water, 50 g of isopropyl alcohol, 100 g of propylene glycol methyl ether, 1 g of emulsifier DNS-86, and 2 g of emulsifier CO-897 emulsifier are added into a reaction kettle, and stirred and mixed uniformly at a stirring speed of 300 r / min. Then, 48 g of trimethylolpropane diallyl ether and 20 g of vinyltrimethoxysilane are added, and stirred and mixed for 30 min. The temperature is increased to 80 ℃, and a potassium persulfate solution (1.5 g of potassium persulfate is previously dissolved in 10 g of deionized water) is added. The stirring speed is 200 r / min, and the reaction is performed for 70 min. Then, the following two materials are synchronously and uniformly added through two constant-pressure dropping funnels:

[0090] Pre-emulsion: 260 g of butyl acrylate, 30 g of maleic acid monobutyl ester, 50 g of methacrylic acid dodecafluoroheptyl ester, and 32 g of vinyl fluorosilicone oil are added into a stirrer, and stirred and mixed uniformly;

[0091] Potassium persulfate solution: 2.0 g of potassium persulfate is previously dissolved in 20 g of deionized water;

[0092] The dropping time is about 3 h, and the temperature is controlled at 80 ℃ during the dropping. After the dropping is completed, the temperature is increased to 90 ℃, and the system is kept at 90 ℃ for 1.5 h. Then, the system is cooled to 55 ℃, and vacuum distillation is performed under a vacuum degree of -0.08 MPa until no distillate is discharged. The system is cooled to 40 ℃, filtered, and adjusted to a solid content of 50% by using deionized water to obtain the modified silicone-acrylate emulsion.

[0093] Preparation Example 3

[0094] The preparation method of the modified silicone-acrylate emulsion of the present preparation example comprises the following steps:

[0095] Under nitrogen atmosphere, 100 g of deionized water, 50 g of isopropyl alcohol, 100 g of propylene glycol methyl ether, 3 g of emulsifier DNS-86 and 2 g of emulsifier CO-897 were added into a reaction kettle, stirred and mixed uniformly at a speed of 300 r / min, 40 g of trimethylolpropane diallyl ether and 16 g of vinyl trimethoxysilane were added, stirred and mixed for 25 min, the temperature was raised to 90℃, and potassium persulfate solution (1.5 g of potassium persulfate was previously dissolved in 10 g of deionized water) was added, and stirred at a speed of 200 r / min for 80 min. The following two materials were synchronously and uniformly added through two constant pressure dropping funnels:

[0096] Pre-emulsion: 250 g of butyl acrylate, 25 g of maleic acid monobutyl ester, 45 g of methacrylic acid dodecafluoroheptyl ester and 26 g of vinyl fluorosilicone oil were added into a stirrer and stirred and mixed uniformly;

[0097] Potassium persulfate solution: 2.5 g of potassium persulfate was previously dissolved in 20 g of deionized water;

[0098] The dropping time was about 3 h, and the temperature was controlled at 90℃ during the period. After the dropping was completed, the system was kept for 1 h, then cooled to 55℃, and reduced pressure distillation was carried out under a vacuum degree of -0.08 MPa until no distillate flowed out. The system was cooled to 40℃, filtered, and deionized water was used to adjust the system to a solid content of 55%, to obtain a modified silicone-acrylate emulsion.

[0099] Preparation of polyurethane-acrylate core-shell emulsion

[0100] Preparation Example 4

[0101] The preparation method of the polyurethane-acrylate core-shell emulsion of the present preparation example comprises the following steps:

[0102] Under nitrogen atmosphere, 50 g of polytetrahydrofuran diol, 25 g of isophorone diisocyanate, 3 g of dimethylol propionic acid, 0.1 g of dibutyl tin dilaurate and 40 g of acetone were added into a reactor, the temperature was raised to 60℃, and reacted for 4 h. The system was cooled to 35℃, and triethylamine was used to adjust the pH to 7.5. The system was added into 75 g of deionized water containing 1.5 g of emulsifier CO-436 at a stirring speed of 1000 r / min, and the temperature was raised to 70℃. The following two materials were synchronously and uniformly added through two constant pressure dropping funnels:

[0103] Pre-emulsion: 25 g of butyl acrylate, 10 g of methyl methacrylate and 5 g of maleic acid monobutyl ester were added into a stirrer and stirred and mixed uniformly;

[0104] Potassium persulfate solution: 0.5 g of potassium persulfate was previously dissolved in 10 g of deionized water;

[0105] The dropping time is about 1 h, and the temperature is controlled at 70°C during the dropping. After the dropping is completed, the temperature is increased to 80°C, and the system is kept at 80°C for 1.5 h. Then the system is cooled to 45°C, and vacuum distillation is carried out at a vacuum degree of -0.08 MPa until no distillate is obtained. The system is cooled to 40°C, and deionized water is added to adjust the solid content to 50%, thereby obtaining the polyurethane-acrylate core-shell emulsion.

[0106] Preparation Example 5

[0107] The preparation method of the polyurethane-acrylate core-shell emulsion of the present preparation example comprises the following steps:

[0108] Under a nitrogen atmosphere, 60 g of polytetrahydrofuran diol, 35 g of isophorone diisocyanate, 4 g of dimethylol propionic acid, 0.2 g of dibutyl tin dilaurate, and 50 g of acetone are added to a reactor, the temperature is increased to 80°C, and the reaction is carried out for 2 h. The system is cooled to 35°C, triethylamine is added to adjust the pH to 7.5, and the mixture is stirred at a stirring speed of 800 r / min. Then, the mixture is added to 100 g of deionized water containing 2.0 g of emulsifier CO-436, and the mixture is stirred and mixed uniformly. The temperature is increased to 80°C, and the following two materials are synchronously and uniformly dropped through two constant-pressure dropping funnels:

[0109] Pre-emulsion: 30 g of butyl acrylate, 20 g of methyl methacrylate, and 10 g of maleic acid monobutyl ester are added to a stirrer, and the mixture is stirred and mixed uniformly.

[0110] Ammonium persulfate solution: 0.5 g of ammonium persulfate is pre-dissolved in 10 g of deionized water.

[0111] The dropping time is about 1 h, and the temperature is controlled at 80°C during the dropping. After the dropping is completed, the temperature is increased to 90°C, and the system is kept at 90°C for 2.5 h. Then the system is cooled to 45°C, and vacuum distillation is carried out at a vacuum degree of -0.08 MPa until no distillate is obtained. The system is cooled to 40°C, and deionized water is added to adjust the solid content to 55%, thereby obtaining the polyurethane-acrylate core-shell emulsion.

[0112] Preparation Example 6

[0113] The preparation method of the polyurethane-acrylate core-shell emulsion of the present preparation example comprises the following steps:

[0114] Under a nitrogen atmosphere, 55 g of polytetrahydrofuran diol, 30 g of isophorone diisocyanate, 4 g of dimethylol propionic acid, 0.15 g of dibutyl tin dilaurate, and 50 g of acetone are added to a reactor, the temperature is increased to 70°C, and the reaction is carried out for 3 h. The system is cooled to 30°C, triethylamine is added to adjust the pH to 7.5, and the mixture is stirred at a stirring speed of 800 r / min. Then, the mixture is added to 100 g of deionized water containing 2.0 g of emulsifier CO-436, and the mixture is stirred and mixed uniformly. The temperature is increased to 90°C, and the following two materials are synchronously and uniformly dropped through two constant-pressure dropping funnels:

[0115] Pre-emulsion: 30 g of butyl acrylate, 15 g of methyl methacrylate and 10 g of monobutyl maleate were added into a stirrer and stirred and mixed uniformly;

[0116] Potassium persulfate solution: 0.55 g of potassium persulfate was previously dissolved in 10 g of deionized water;

[0117] The dropping time was about 1 h, during which the temperature was controlled at 90°C, after the dropping was completed, the system was continuously incubated for 2 h, then the system was cooled to 45°C, and the vacuum distillation was carried out under the vacuum degree of -0.08 MPa until no fraction was flowed out, and then the system was cooled to 40°C, and deionized water was used to adjust the solid content to 55%, thus a polyurethane-acrylate core-shell emulsion was obtained.

[0118] Preparation examples 7~9 polyether polyol modified nanofillers

[0119] Preparation example 7

[0120] The preparation method of the polyether polyol modified nanofiller of the present preparation example comprises the following steps:

[0121] The nanosilica and nanattapulgite with a mass ratio of 1:1 were immersed in dilute nitric acid with a mass fraction of 10%, and then the temperature was increased to 60°C, and the mixture was stirred for 2 h, after centrifugal separation, deionized water was used for washing until neutral, and then the mixture was dried at 50°C until the weight was constant, thus obtaining acidified nanofiller;

[0122] Under the nitrogen atmosphere, 50 g of the acidified nanofiller was added into 200 g of toluene, and the mixture was stirred at a speed of 800 r / min for 30 min, then 0.05 g of dibutyltin dilaurate was added and mixed uniformly, and then 10 g of polyoxypropylene diol was added and mixed uniformly, and then the temperature was increased to 80°C, and the reaction was carried out for 6 h, and then the mixture was cooled to room temperature, centrifugal separation was carried out, the mixture was washed with toluene for 2 times, deionized water was used for washing until neutral, and then the mixture was dried at 50°C until the weight was constant, thus obtaining polyether polyol modified nanofiller.

[0123] Preparation example 8

[0124] The preparation method of the polyether polyol modified nanofiller of the present preparation example comprises the following steps:

[0125] The nanosilica and nanattapulgite with a mass ratio of 3:1 were immersed in dilute nitric acid with a mass fraction of 12%, and then the temperature was increased to 55°C, and the mixture was stirred for 2 h, after centrifugal separation, deionized water was used for washing until neutral, and then the mixture was dried at 50°C until the weight was constant, thus obtaining acidified nanofiller;

[0126] Under nitrogen atmosphere, 50g acidified nano-filler was added into 200g toluene, stirred and mixed at 800r / min for 30min, then 0.06g dibutyltin dilaurate was added and mixed uniformly, 15g polytetrahydrofuran diol was added and mixed uniformly, heated to 90℃, reacted for 5h, cooled to room temperature, centrifuged, washed twice with toluene, washed with deionized water until neutral, dried at 50℃ to constant weight, to obtain polyether polyol modified nano-filler.

[0127] Preparation Example 9

[0128] The preparation method of the polyether polyol modified nano-filler of the present preparation example comprises the following steps:

[0129] The mass ratio of nano-silica and nano-attapulgite was 2:1, and they were immersed in 10% dilute nitric acid, heated to 55℃, stirred and mixed for 3h, then centrifuged, washed with deionized water until neutral, and dried at 50℃ to constant weight to obtain acidified nano-filler;

[0130] Under nitrogen atmosphere, 50g acidified nano-filler was added into 200g toluene, stirred and mixed at 800r / min for 30min, then 0.06g dibutyltin dilaurate was added and mixed uniformly, 15g polytetrahydrofuran diol was added and mixed uniformly, heated to 90℃, reacted for 5h, cooled to room temperature, centrifuged, washed twice with toluene, washed with deionized water until neutral, dried at 50℃ to constant weight, to obtain polyether polyol modified nano-filler.

[0131] Example 1

[0132] The preparation process of the low-temperature resistant waterproof coating for housing building exterior wall of the present example comprises the following steps:

[0133] S1: 60g of composite solvent, 2g of dispersant, 1g of defoaming agent, and 40g of polyether polyol modified nano-filler were added into a stirrer, stirred and mixed at 800r / min for 30min to obtain a uniform slurry;

[0134] S2: 15g of chlorobutyl rubber nano-powder and 10g of liquid polyisoprene were added into a stirrer, stirred and mixed at 800r / min for 30min to obtain an elastomer blend;

[0135] S3: 200 g of modified silicone-acrylate emulsion and 75 g of polyurethane-acrylate core-shell emulsion were added into a mixer, stirred and mixed at a speed of 300 r / min for 15 min, then 12 g of film-forming agent was added, stirred and mixed for 15 min, and then 4 g of thickening agent was slowly added after adjusting the solid content to 50% with deionized water, and stirred and mixed for 15 min, 1 g of preservative and 2 g of ultraviolet absorber were added, and stirred and mixed for 10 min, the pH was adjusted to 7.5 with triethylamine, 0.5 g of defoaming agent was added, and stirred at a speed of 150 r / min for 5 min, to obtain the low-temperature-resistant waterproof coating.

[0136] The auxiliary agents include 2 g of dispersant, 1.5 g of defoaming agent, 4 g of thickening agent, 12 g of film-forming agent, 1 g of preservative, and 2 g of ultraviolet absorber; and the specific contents are as follows: the dispersant is a polycarboxylate dispersant; the defoaming agent is a polyether-modified silicone defoaming agent; the thickening agent is a hydrophobically modified polyurethane rheological thickening agent; the film-forming agent is dodecanol ester; the preservative is isothiazolinone; and the ultraviolet absorber is benzotriazole.

[0137] The composite solvent includes 24 g of deionized water, 24 g of propylene glycol methyl ether, and 12 g of isopropyl alcohol.

[0138] The modified silicone-acrylate emulsion is from Preparation Example 1; the polyurethane-acrylate core-shell emulsion is from Preparation Example 4; and the polyether polyol modified nano filler is from Preparation Example 7.

[0139] Example 2

[0140] The preparation process of the low-temperature-resistant waterproof coating for the exterior wall of a house building in this example includes the following steps:

[0141] S1: 100 g of composite solvent, 3 g of dispersant, 2 g of defoaming agent, and 60 g of polyether polyol modified nano filler were added into a stirrer, stirred and mixed at a speed of 800 r / min for 30 min to obtain a uniform slurry;

[0142] S2: 25 g of chlorobutyl rubber nano powder and 20 g of liquid polyisoprene were added into a stirrer, stirred and mixed at a speed of 800 r / min for 30 min to obtain an elastomer blend;

[0143] S3: 250 g of modified silicone-acrylate emulsion and 125 g of polyurethane-acrylate core-shell emulsion were added into a mixer, stirred and mixed at a speed of 300 r / min for 15 min, then 16 g of film-forming agent was added, stirred and mixed for 15 min, and then 6 g of thickening agent was slowly added after adjusting the solid content to 50% with deionized water, and stirred and mixed for 15 min, 2 g of preservative and 4 g of ultraviolet absorber were added, and stirred and mixed for 10 min, then pH was adjusted to 8.5 with triethylamine, 1 g of defoaming agent was added, and stirred at a speed of 150 r / min for 5 min, to obtain the low-temperature resistant waterproof coating.

[0144] The auxiliary agents include 3 g of dispersant, 3 g of defoaming agent, 6 g of thickening agent, 16 g of film-forming agent, 2 g of preservative and 4 g of ultraviolet absorber, and the specific contents are as follows: the dispersant is polycarboxylate dispersant; the defoaming agent is polyether modified silicone defoaming agent; the thickening agent is hydrophobically modified polyurethane rheological thickening agent; the film-forming agent is dodecanol ester; the preservative is isothiazolinone; and the ultraviolet absorber is benzotriazole;

[0145] The composite solvent includes 50 g of deionized water, 25 g of propylene glycol methyl ether and 25 g of isopropyl alcohol;

[0146] The modified silicone-acrylate emulsion is from Preparation Example 2; the polyurethane-acrylate core-shell emulsion is from Preparation Example 5; and the polyether polyol modified nano filler is from Preparation Example 8.

[0147] Example 3

[0148] The preparation process of the low-temperature resistant waterproof coating for the exterior wall of a house building in the example includes the following steps:

[0149] S1: 80 g of composite solvent, 2.5 g of dispersant, 1.5 g of defoaming agent and 50 g of polyether polyol modified nano filler were added into a stirrer, stirred and mixed at a speed of 800 r / min for 30 min to obtain a uniform slurry;

[0150] S2: 20 g of nitrile rubber nano powder and 15 g of liquid polyisoprene were added into a stirrer, stirred and mixed at a speed of 800 r / min for 30 min to obtain an elastomer blend;

[0151] S3: 230 g of modified silicone-acrylate emulsion and 100 g of polyurethane-acrylate core-shell emulsion were added into a mixing machine, stirred and mixed at a speed of 300 r / min for 15 min, 14 g of film-forming agent was added, stirred and mixed for 15 min, then deionized water was used to adjust the solid content to 50%, 5 g of thickening agent was slowly added, stirred and mixed for 15 min, 1.5 g of preservative and 3 g of ultraviolet absorber were added, stirred and mixed for 10 min, triethylamine was used to adjust the pH to 8.0, 1 g of defoaming agent was added, and stirred at 150 r / min for 5 min to obtain a low-temperature-resistant waterproof coating.

[0152] The auxiliary agents include 2.5 g of dispersant, 2.5 g of defoaming agent, 5 g of thickening agent, 14 g of film-forming agent, 1.5 g of preservative and 3 g of ultraviolet absorber; and the specific types are as follows: the dispersant is polycarboxylate dispersant; the defoaming agent is polyether-modified silicone defoaming agent; the thickening agent is hydrophobically modified polyurethane rheological thickening agent; the film-forming agent is dodecanol ester; the preservative is isothiazolinone; and the ultraviolet absorber is benzotriazole;

[0153] The composite solvent includes 50 g of deionized water, 35 g of propylene glycol methyl ether and 15 g of isopropyl alcohol.

[0154] The modified silicone-acrylate emulsion is from Preparation Example 3; the polyurethane-acrylate core-shell emulsion is from Preparation Example 6; and the polyether polyol modified nano filler is from Preparation Example 9.

[0155] Example 4

[0156] The difference between this example and Example 3 is that:

[0157] S3: 230 g of modified silicone-acrylate emulsion and 100 g of polyurethane-acrylate core-shell emulsion were added into a mixing machine, stirred and mixed at a speed of 300 r / min for 15 min, 14 g of film-forming agent was added, stirred and mixed for 15 min, then deionized water was used to adjust the solid content to 50%, 5 g of thickening agent was slowly added, stirred and mixed for 15 min, 1.5 g of preservative and 3 g of ultraviolet absorber were added, stirred and mixed for 10 min, triethylamine was used to adjust the pH to 8.0, 1 g of defoaming agent was added, and stirred at 150 r / min for 5 min to obtain a low-temperature-resistant waterproof coating.

[0158] The rest is the same as Example 3.

[0159] Example 5

[0160] The difference between this example and Example 4 is that:

[0161] S1: 80 g of the composite solvent, 2.5 g of the dispersant, 1.5 g of the defoaming agent, 50 g of the polyether polyol modified nano filler, and 3 g of the microsilica powder were added into a stirrer, stirred and mixed at a rotating speed of 800 r / min for 30 min, and a uniform slurry was obtained;

[0162] Before use, the microsilica powder was subjected to the following pretreatment steps:

[0163] 0.08 g of the silane coupling agent KH560 was added into 10 g of the ethanol aqueous solution, 5% acetic acid was used to adjust the pH to 5.0, the temperature was increased to 50°C, and hydrolysis was performed under stirring for 60 min to obtain a pretreatment liquid;

[0164] 3 g of the microsilica powder was placed in a container, 3.6 g of the pretreatment liquid was slowly added under stirring at a speed of 150 r / min, and stirring was continued until the mixture was uniformly mixed, and then the mixture was transferred into a 50°C drying oven for drying until the weight was constant, and then the mixture was slightly ground and dispersed for standby.

[0165] The volume ratio of ethanol to deionized water in the ethanol aqueous solution was 1:1.

[0166] The other steps were the same as in Example 4.

[0167] Example 6

[0168] The difference between this example and Example 5 is that:

[0169] S1: 80 g of the composite solvent, 2.5 g of the dispersant, 1.5 g of the defoaming agent, 50 g of the polyether polyol modified nano filler, 3 g of the microsilica powder, and 2 g of the calcined kaolin were added into a stirrer, stirred and mixed at a rotating speed of 800 r / min for 30 min, and a uniform slurry was obtained;

[0170] Before use, the microsilica powder and the calcined kaolin were subjected to the following pretreatment steps:

[0171] 0.15 g of the silane coupling agent KH560 was added into 15 g of the ethanol aqueous solution, 5% acetic acid was used to adjust the pH to 4.5, the temperature was increased to 55°C, and hydrolysis was performed under stirring for 70 min to obtain a pretreatment liquid;

[0172] 3 g of the microsilica powder and 2 g of the calcined kaolin were placed in a container, 7.5 g of the pretreatment liquid was slowly added under stirring at a speed of 150 r / min, and stirring was continued until the mixture was uniformly mixed, and then the mixture was transferred into a 50°C drying oven for drying until the weight was constant, and then the mixture was slightly ground and dispersed for standby.

[0173] The volume ratio of ethanol to deionized water in the ethanol aqueous solution was 1:1.

[0174] The other steps were the same as in Example 5.

[0175] Example 7

[0176] The difference between this embodiment and embodiment 5 is that:

[0177] The amount of carbodiimide is 2 g.

[0178] The other is the same as embodiment 5.

[0179] Comparative example 1

[0180] The difference between this comparative example and embodiment 1 is that:

[0181] The silanized nano filler is prepared by replacing the polyether polyol modified nano filler with silane modified nano filler of the same mass;

[0182] The preparation method of the silanized nano filler comprises the following steps:

[0183] Take 50 g of a premix of nano-silicon dioxide and nano-attapulgite with a mass ratio of 1:1, add it to the reactor, then add 200 g of an ethanol aqueous solution, stir and mix at a stirring speed of 1000 r / min for 30 min, then add 6 g of silane coupling agent KH560, adjust the stirring speed to 300 r / min, stir and mix uniformly, adjust the pH to 5.0 with 10% acetic acid, heat to 55°C, stir and mix for 4 h, centrifugal separation, wash once with anhydrous ethanol, wash with deionized water until neutral, dry at 60°C to constant weight, and obtain the silanized nano filler.

[0184] The other is the same as embodiment 1.

[0185] Comparative example 2

[0186] The difference between this comparative example and embodiment 1 is that:

[0187] The preparation method of the modified silicone-acrylate emulsion in this comparative example comprises the following steps:

[0188] Under a nitrogen atmosphere, add 100 g of deionized water, 50 g of isopropyl alcohol, 50 g of propylene glycol methyl ether, 2 g of emulsifier DNS-86, and 2 g of emulsifier CO-897 to the reaction kettle, stir and mix uniformly at a stirring speed of 300 r / min, add 32 g of trimethylolpropane diallyl ether, 12 g of vinyltrimethoxysilane, 240 g of butyl acrylate, 20 g of monobutyl maleate, 40 g of dodecafluoroheptyl methacrylate, and 20 g of vinyl fluorosilicone oil, continue to stir and mix for 20 min, heat to 70°C, add a potassium persulfate solution (4.4 g of potassium persulfate is pre-dissolved in 30 g of deionized water), stir at a stirring speed of 200 r / min for 4.5 h, heat to 80°C, and maintain for 2 h, then cool the system to 55°C, perform vacuum distillation at a vacuum degree of -0.08 MPa until no distillate flows out, cool to 40°C, filter, adjust the system to a solid content of 55% with deionized water, and obtain the modified silicone-acrylate emulsion.

[0189] Other embodiments as in Example 1.

[0190] Comparative Example 3

[0191] The preparation method of the modified silicone-acrylate emulsion of the present comparative example comprises the following steps:

[0192] Under a nitrogen atmosphere, 100 g of deionized water, 50 g of isopropyl alcohol, 50 g of propylene glycol methyl ether, 2 g of emulsifier DNS-86, and 2 g of emulsifier CO-897 were added to a reaction kettle and stirred at a speed of 300 r / min until uniformly mixed. Then, 32 g of trimethylolpropane diallyl ether and 12 g of vinyl trimethoxysilane were added, and stirring was continued for 20 min. The temperature was then raised to 70°C, and a potassium persulfate solution (1.6 g of potassium persulfate was previously dissolved in 10 g of deionized water) was added. The reaction was stirred at a speed of 200 r / min for 90 min. The following two materials were simultaneously and uniformly added through two constant-pressure dropping funnels:

[0193] Pre-emulsion: 240 g of butyl acrylate, 40 g of dodecafluoroheptyl methacrylate, and 20 g of vinyl fluorosilicone oil were added to a stirrer and stirred until uniformly mixed;

[0194] Potassium persulfate solution: 2.8 g of potassium persulfate was previously dissolved in 20 g of deionized water;

[0195] The dropping time was about 3 h, during which the temperature was controlled at 70°C. After the dropping was completed, the temperature was raised to 80°C, and the system was kept at this temperature for 2 h. Then, the system was cooled to 55°C, and vacuum distillation was performed at a vacuum degree of -0.08 MPa until no distillate was obtained. The system was then cooled to 40°C, filtered, and adjusted to a solid content of 55% using deionized water to obtain the modified silicone-acrylate emulsion.

[0196] Comparative Example 4

[0197] The difference between the present comparative example and Example 1 is:

[0198] The preparation method of the polyurethane-acrylate core-shell emulsion of the present comparative example comprises the following steps:

[0199] Under a nitrogen atmosphere, 50 g of polytetrahydrofuran diol, 25 g of isophorone diisocyanate, 0.1 g of dibutyltin dilaurate, and 40 g of acetone were added to a reactor. The temperature was raised to 60°C, and the reaction was continued for 4 h. The temperature was then cooled to 35°C, and the pH was adjusted to 7.5 using triethylamine. The mixture was then added to 75 g of deionized water containing 1.5 g of emulsifier CO-436 at a stirring speed of 1000 r / min until uniformly mixed. The temperature was then raised to 70°C, and the following two materials were simultaneously and uniformly added through two constant-pressure dropping funnels:

[0200] Pre-emulsion: 25 g of butyl acrylate and 10 g of methyl methacrylate were added into a stirrer and stirred to mix uniformly;

[0201] Potassium persulfate solution: 0.5 g of potassium persulfate was pre-dissolved in 10 g of deionized water;

[0202] The dropping time was about 1 h, and the temperature was controlled at 70 ℃ during the dropping. After the dropping was completed, the temperature was increased to 80 ℃, and the temperature was kept for 1.5 h. Then, the system was cooled to 45 ℃, and the vacuum distillation was performed under a vacuum degree of -0.08 MPa until no distillate was obtained. The temperature was cooled to 40 ℃, and deionized water was used to adjust the solid content to 55%, to obtain the polyurethane-acrylate core-shell emulsion.

[0203] The other conditions were the same as in Example 1.

[0204] Comparative Example 5

[0205] The difference between this comparative example and Example 1 was that:

[0206] The modified silicone-acrylate emulsion was used to replace the polyurethane-acrylate core-shell emulsion.

[0207] The other conditions were the same as in Example 1.

[0208] Performance detection test

[0209] The low-temperature resistant waterproof coatings prepared in Examples 1-7 and Comparative Examples 1-5 were used to prepare standard samples according to the detection items:

[0210] (1) The coatings were uniformly coated on the surface of a standard cement mortar board, and the dry film thickness was controlled at (100±10) μm. After the surface was dried under standard conditions of a temperature of (23±2) ℃ and a relative humidity of (50±5)%, the sample was transferred into a low-temperature box at a temperature of (5±1) ℃ for solidification for 48 h. Then, the sample was cured under standard conditions of a temperature of (23±2) ℃ and a relative humidity of (50±5)% for 7 days.

[0211] (2) The coatings were poured on a flat polytetrafluoroethylene plate, and a scraper was used to control the thickness to prepare a coating film with uniform thickness. After curing under standard conditions of a temperature of (23±2) ℃ and a relative humidity of (50±5)% for 7 days, the coating film was removed, and a standard dumbbell-shaped cutter was used to cut the sample into a sample with a specified size.

[0212] Then, the performance detection was performed, and the detection results are shown in Table 1. The reference standards are as follows: adhesion: GB / T 5210-2006; tensile strength and elongation at break: GB / T 16777-2008; water resistance: GB / T 1733-1993.

[0213] Table 1 Performance detection data of the low-temperature resistant waterproof coatings prepared in Examples 1-7 and Comparative Examples 1-5

[0214]

[0215] The performance test data of the samples prepared in Comparative Examples 1-5 and Example 1 show that:

[0216] Comparative Example 1 uses silanized nano-filler, which has strong interface bonding rigidity, and its adhesion and flexibility are both insufficient, resulting in fine cracks when bending at low temperature, and the elongation at break is also lost; Comparative Example 2 has a wide molecular weight distribution due to the synthesis process, which leads to deterioration of adhesion, mechanical strength and water resistance; Comparative Examples 3 and 4 each lack a carboxyl-containing monomer, which weakens the emulsion stability and the interface bonding between components, resulting in insufficient film density and thus poor water resistance and adhesion; Comparative Example 5 only uses a silicone-acrylate emulsion, which has high adhesion and tensile strength, but lacks the elasticity provided by polyurethane, resulting in low elongation at break and poor low-temperature flexibility.

[0217] The performance test data of the samples prepared in Examples 1-7 show that by introducing carbodiimide and adding silane-treated micro-silica powder and calcined kaolin, the tensile strength of the coating film is gradually improved. At the same time, with the moderate increase in crosslinking density and rigid particle content, the movement ability of the polymer molecular chain is limited to a certain extent, and the elongation at break slowly decreases. The samples prepared in Examples 1-7, by optimizing the interface design, maintain relatively high adhesion while improving strength and rigidity, and also have excellent low-temperature flexibility and water resistance.

[0218] The specific embodiments are merely an explanation of the present application, and are not a limitation of the present application. Those skilled in the art can make modifications to the embodiments without creative contribution after reading the present specification, and as long as the modifications are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A low-temperature resistant waterproof coating for exterior walls of buildings, characterized in that, It is prepared from the following raw materials in parts by weight: 200-250 parts of modified silicone-acrylic emulsion, 75-125 parts of polyurethane-acrylate core-shell emulsion, 40-60 parts of polyether polyol modified nanofiller, 15-25 parts of rubber nanopowder, 10-20 parts of liquid polyisoprene, 22-34 parts of additives and 60-100 parts of composite solvent. The modified silicone-acrylic emulsion is specifically prepared by prepolymerizing a polyhydroxy compound containing double bonds and a silane coupling agent containing double bonds, and then copolymerizing it with monomer A and vinyl fluorosilicone oil. The polyurethane-acrylate core-shell emulsion is specifically formulated by prepolymerizing polyether polyol, isocyanate, and carboxyl-containing hydrophilic monomer, followed by copolymerization with monomer B. The monomer A includes butyl acrylate, monobutyl maleate, and dodecafluoroheptyl methacrylate. The monomer B includes butyl acrylate, methyl methacrylate, and monobutyl maleate.

2. The low-temperature resistant waterproof coating for exterior walls of buildings according to claim 1, characterized in that, The preparation method of the modified silicone-acrylic emulsion includes the following steps: Under an inert atmosphere, the composite solvent and emulsifier are mixed evenly, then a polyhydroxy compound containing double bonds and a silane coupling agent containing double bonds are added and mixed evenly. The mixture is heated to 70-90°C, a portion of the initiator is added, and the reaction is carried out for 60-90 minutes. Then, monomer A, vinyl fluorosilicone oil and the remaining initiator are added, and the mixture is kept at this temperature for 4-5 hours. The mixture is then distilled under reduced pressure, cooled, and the solid content is adjusted to obtain the modified silicone-acrylic emulsion.

3. The low-temperature resistant waterproof coating for exterior walls of buildings according to claim 2, characterized in that, The polyhydroxy compound containing a double bond is either trimethylolpropane diallyl ether or pentaerythritol triallyl ether.

4. The low-temperature resistant waterproof coating for exterior walls of buildings according to claim 1, characterized in that, The preparation method of the polyurethane-acrylate core-shell emulsion includes the following steps: Under an inert atmosphere, polyether polyol, isocyanate, carboxyl-containing hydrophilic monomer, catalyst, and acetone are added to a reactor, heated to 60-80°C, reacted for 2-4 hours, cooled, and the pH is adjusted to 7.5-8.

0. The mixture is then added to water containing emulsifier, mixed thoroughly, heated to 70-90°C, monomer B and initiator are added, and the mixture is kept at this temperature for 2.5-3.5 hours. The mixture is then distilled under reduced pressure, cooled, and the solid content is adjusted to obtain a polyurethane-acrylate core-shell emulsion.

5. The low-temperature resistant waterproof coating for exterior walls of buildings according to claim 1, characterized in that, The preparation method of the polyether polyol modified nanofiller includes the following steps: Under an inert atmosphere, the acidified nanofiller is uniformly dispersed in an organic solvent, a catalyst is added and mixed evenly, then polyether polyol is added and mixed evenly. The mixture is heated to 80-100℃ and reacted for 4-6 hours. After cooling, solid-liquid separation is performed, followed by washing and drying to obtain polyether polyol modified nanofiller.

6. The low-temperature resistant waterproof coating for exterior walls of buildings according to claim 5, characterized in that, The acidified nanofiller includes nano-silica and nano-attapulgite.

7. The low-temperature resistant waterproof coating for exterior walls of buildings according to claim 1, characterized in that, The polyether polyol is either polytetrahydrofuran diol or polyoxypropylene diol.

8. A preparation process for a low-temperature resistant waterproof coating for exterior walls of buildings as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1: Mix the composite solvent, the first part of the additives, and the polyether polyol modified nanofiller evenly to obtain a homogeneous slurry; S2: Mix rubber nanopowder and liquid polyisoprene evenly to obtain an elastomer blend; S3: After mixing the modified silicone-acrylic emulsion and polyurethane-acrylate core-shell emulsion evenly, add the homogenizing slurry, elastomer blend, and the second part of the additives and mix evenly. Adjust the solid content, then add the remaining additives and adjust the pH to 7.5~8.5 to obtain a low-temperature resistant waterproof coating.

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