A low-temperature resistant, acid and alkali resistant roofing waterproof coating and its preparation method

Abstract

The present invention discloses a low-temperature resistant and acid- and alkali-resistant roof waterproof coating and a preparation method thereof. The coating is composed of a variety of raw materials such as acrylate-organic silicon copolymer emulsion, polyurethane-modified acrylate resin, and the key raw materials are prepared by free radical polymerization and addition polymerization. The preparation method includes the steps of pre-dispersion, auxiliary agent dispersion, pigment and filler dispersion, emulsion and functional additive compounding, and performance regulation. The acrylate-organic silicon copolymer emulsion and polyurethane-modified acrylate resin in the present invention form an interpenetrating network through physical blending and chemical cross-linking, which has both the low-temperature toughness of the flexible phase and the chemical resistance of the rigid phase. Under low-temperature conditions, the flexibility of the silicone chain segment offsets the rigid embrittlement of the polyurethane resin, avoiding cracking of the coating; in acidic and alkaline environments, the urethane bond of the polyurethane and the silicon-oxygen bond of the silicone work together to resist chemical erosion, reduce molecular chain breakage, and effectively solve the problem of insufficient performance of existing waterproof coatings under low temperature and acidic and alkaline environments.

Description

Technical Field

[0001] The present invention relates to the technical field of waterproof coatings, in particular to a low-temperature resistant, acid- and alkali-resistant roof waterproof coating and a preparation method thereof. Background Art

[0002] In the construction industry, roof waterproofing is a critical component in ensuring building safety and proper operation. With the development of the construction industry, the performance requirements for roof waterproofing coatings have become increasingly stringent. Currently, common roof waterproofing coatings on the market have exposed numerous issues when subjected to complex operating environments. For example, their flexibility deteriorates significantly at low temperatures. When temperatures fall below their glass transition temperature, the mobility of polymer chains is limited, preventing the effective release of stress within the coating. This makes the coating susceptible to cracking due to temperature fluctuations or even slight external stretching. Once the coating cracks, its waterproofing function is lost, allowing moisture to penetrate the roof structure, corroding the building's core structure and shortening its service life. In acidic and alkaline environments, such as those in areas with severe industrial pollution, acidic gases in the air (such as sulfur dioxide and nitrogen oxides) react with water to form acid rain. Furthermore, acidic and alkaline substances around certain specialized buildings (such as chemical plants and laboratories) can corrode the waterproofing coating. Acidic and alkaline substances will destroy the molecular structure of the coating, break the chemical bonds of the coating, and cause the coating's strength, adhesion and other properties to decline. The coating will gradually be eroded and peeled off, greatly shortening the service life of the waterproof coating, increasing building maintenance costs, and even posing a threat to the structural safety of the building.

[0003] Although there are some low-temperature resistant coatings and acid- and alkali-resistant coatings in the existing technology, it is often difficult to meet both performance requirements at the same time. Coatings that are both low-temperature resistant and acid- and alkali-resistant face many difficulties in the research and development and production process. On the one hand, to improve the low-temperature resistance of the coating, it is usually necessary to increase the content of soft polymers or introduce special low-temperature plasticizers. However, this may reduce the hardness and chemical corrosion resistance of the coating, making it more susceptible to damage in acidic and alkaline environments; on the other hand, to enhance the acid- and alkali resistance of the coating, highly cross-linked polymers are generally used or a large amount of corrosion-resistant fillers are added, which in turn may cause the flexibility of the coating to deteriorate and easily crack at low temperatures. In addition, during the preparation process of this type of coating, it is also necessary to balance its low-temperature resistance, acid- and alkali resistance with its construction performance, film-forming properties, and cost.

[0004] Therefore, how to simultaneously improve the low-temperature resistance and acid-base resistance of the coating is a difficult problem that technicians in this field urgently need to solve. Summary of the Invention

[0005] The purpose of the present invention is to provide a low-temperature resistant, acid- and alkali-resistant roof waterproof coating and a preparation method thereof, aiming to solve the problems of existing waterproof coatings such as poor flexibility and easy cracking in low-temperature environments, and molecular structure destruction and performance degradation in acidic and alkaline environments, meet the waterproofing needs of building roofs in complex environments, extend the service life of buildings, and reduce building maintenance costs.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] In a first aspect, the present invention provides a low-temperature resistant, acid- and alkali-resistant roof waterproof coating comprising the following raw material components in parts by weight:

[0008] 15-25 parts of acrylate-organic silicone copolymer emulsion, 5-15 parts of polyurethane-modified acrylate resin, 5-10 parts of titanium dioxide, 8-15 parts of heavy calcium carbonate, 2-5 parts of zinc oxide, 2-5 parts of organic alcohol amine ether compound, 3-6 parts of dispersant, 1-3 parts of defoamer, 1-3 parts of bactericide and mildewproofing agent, 2-4 parts of film-forming aid, 2-5 parts of rheology modifier, 2-5 parts of propylene glycol, and 30-50 parts of solvent;

[0009] The raw materials of the acrylate-silicone copolymer emulsion include 60-70 parts by weight of acrylate monomer, 5-15 parts by weight of silicone monomer, 3-8 parts by weight of hydroxyethyl acrylate, 2-5 parts by weight of emulsifier and 0.3-1.0 parts by weight of initiator. It is prepared by free radical polymerization reaction, wherein the silicone monomer is introduced into the copolymer chain segment through silicon-oxygen bond, the glass transition temperature is controlled at -20°C to -10°C, and the molecular weight dispersion is 1.5-2.0.

[0010] The present invention introduces silicon-oxygen bonds through free radical polymerization, and its low glass transition temperature Tg = -20°C ~ -10°C allows the molecular segments to maintain flexibility at low temperatures, offsetting the rigid brittleness of the polyurethane resin. The low cohesive energy density of the silicon-oxygen bonds can effectively reduce the intermolecular forces and prevent the coating from cracking due to freezing of the segments below -30°C. In addition, the high hydrolysis activation energy of the silicon-oxygen bonds forms a hydrophobic barrier, delaying the penetration of acids and alkalis; the hydroxyl groups provided by hydroxyethyl acrylate cross-link with the polyurethane prepolymer to enhance the overall stability of the coating. The present invention achieves the combination of low-temperature toughness and chemical resistance for the first time through the copolymerization of silicon-oxygen bonds and acrylates, solving the problem in the prior art that single silicone emulsions are resistant to low temperatures but lack acid and alkali resistance.

[0011] The polyurethane-modified acrylate resin of the present invention comprises raw materials including 60-70 parts by weight of a non-hydroxyl acrylate monomer, 10-20 parts by weight of a hydroxyl acrylate monomer, 30-40 parts by weight of a diisocyanate and 10-20 parts by weight of a diol, and is prepared by addition polymerization. The molar ratio of isocyanate groups to hydroxyl groups is 1.2-1.5:1, the glass transition temperature is controlled at 10°C to 20°C, and the molecular weight dispersion is 1.5-2.0.

[0012] The present invention forms urethane bonds through addition polymerization. These bonds, with a glass transition temperature (Tg) of 10°C to 20°C, act as the rigid phase, forming a "rigid-flexible interpenetrating network" with the flexible silicone emulsion. This restricts excessive deformation of the flexible phase at low temperatures, maintaining a stable coating structure. Furthermore, the cross-linked urethane network physically blocks the penetration of acid and base molecules, while polar groups enhance interfacial bonding with pigments and fillers, improving coating adhesion.

[0013] The coating of this invention utilizes a flexible acrylate-silicone copolymer emulsion compounded with a rigid polyurethane-modified acrylate resin to form a "rigid-flexible interpenetrating network." The flexible phase absorbs stress at low temperatures, while the rigid phase provides support at room temperature, achieving a balance between crack-free performance at -30°C and resistance to acid and alkali corrosion. Furthermore, titanium dioxide in the pigments and fillers reflects ultraviolet light to inhibit photoaging, while ground calcium carbonate fills pores and zinc oxide enhances interfacial bonding, creating a physical barrier that slows acid and alkali penetration.

[0014] In some implementations, the dispersant is a combination of an anionic dispersant and a nonionic dispersant, with a weight ratio of 1:(1-2). The anionic dispersant is selected from one or more of sodium polyacrylate, alkylnaphthalene sulfonates, and lignin sulfonates, and the nonionic dispersant is selected from one or more of octylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, and polyoxyethylene ethers. The combination of anionic and nonionic dispersants, through the synergistic effects of electrostatic repulsion and steric hindrance, allows pigments and fillers such as titanium dioxide to be dispersed to a fineness of less than 45 μm, preventing coating defects caused by agglomeration.

[0015] In some possible implementations, the defoamer is a combination of a silicone defoamer and a mineral oil defoamer, with the weight ratio of the two being (5-7):(3-5). The silicone defoamer is selected from one or more of polydimethylsiloxane emulsions, polyether-modified silicone oils, and self-emulsifying silicone defoamers; and the mineral oil defoamer is selected from one or more of white oil, paraffin oil, and emulsion-type defoamers combined with surfactants. In the present invention, the silicone defoamer can achieve rapid foam breaking, while the mineral oil defoamer can effectively inhibit foam regeneration and is free of shrinkage defects.

[0016] In some feasible embodiments, the rheology modifier is a compound of an associative thickener and a cellulose ether thickener, and the weight ratio of the two is 1:(1-1.2); the associative thickener is selected from one or more of a nonionic polyurethane associative thickener, a hydrophobically modified alkali-swellable thickener, and a hydrophobically modified cellulose ether; and the cellulose ether thickener is selected from one or more of hydroxyethyl cellulose, hydroxypropyl methylcellulose, and ethyl hydroxyethyl cellulose.

[0017] In the present invention, the associative thickener forms a dynamic network by associating with latex particles through hydrophobic groups. The shear force destroys the network and reduces the viscosity. The network is rebuilt after the shear is removed. The cellulose ether forms a three-dimensional network structure through hydroxyl hydrogen bonds, which increases the viscosity under static conditions and prevents the sedimentation of pigments and fillers, achieving ideal rheological curves of high shear low viscosity and low shear high viscosity, adapting to multiple brushing / spraying scenarios.

[0018] In some feasible embodiments, the weight ratio of the components targeting bacteria and mold in the bactericidal and mildew-proof agent is 1:(1-1.5), the component targeting bacteria is selected from one of quaternary ammonium salts and isothiazolinones; the component targeting mold is selected from one of pyridines and azoles.

[0019] In a second aspect, the present invention also provides a method for preparing a low-temperature resistant acid and alkali resistant roof waterproof coating, comprising the following steps:

[0020] (1) Pre-dispersion: Add deionized water to the reactor, add part of the rheology modifier during stirring, wait for it to dissolve, then add the organic alcohol amine ether compound and continue stirring;

[0021] (2) Dispersion of additives: During the stirring process, add dispersant, part of defoamer, and bactericide and mildew inhibitor into the reactor in sequence and stir evenly;

[0022] (3) Pigment and filler dispersion: During the stirring process, add titanium dioxide, heavy calcium carbonate, and zinc oxide, and continue stirring until the paint fineness is detected to be below 45 μm;

[0023] (4) Compounding of emulsion and functional additives: First, fully mix the acrylate-silicone copolymer emulsion and the polyurethane-modified acrylate resin, then add the film-forming additive, propylene glycol, the remaining rheology modifier and defoamer in the reaction kettle of step (3) and continue stirring;

[0024] (5) Performance control: Control the coating viscosity to 105±3KU, adjust it by adding deionized water or rheology modifier, and finally filter the material.

[0025] Among them, acrylate-silicone copolymer emulsion utilizes the siloxy bond of silicone monomer to break under the action of initiator to form free radicals, which copolymerize with the carbon-carbon double bond of acrylate monomer and hydroxyethyl acrylate to form copolymer chain segments containing siloxy bonds; polyurethane modified acrylate resin utilizes the isocyanate group in polyurethane prepolymer to undergo addition reaction with the hydroxyl group in acrylate resin to generate urethane bond.

[0026] In some achievable methods, after the rheology modifier is added in step (1), stirring is performed at a low speed of 300-500 r / min until it is completely dissolved, and then the organic alcohol amine ether compound is added and stirring is continued for 10-15 minutes.

[0027] In some feasible methods, after the rotation speed is increased to 900 r / min in step (2), a dispersant, a defoaming agent, and a bactericide and mildew inhibitor are added in sequence and stirred for 20-30 minutes until uniform.

[0028] In some feasible methods, after stirring at a low speed of 300-500 r / min for 15-20 min in step (3), titanium dioxide, heavy calcium carbonate, and zinc oxide are added, and the speed is increased to 1600-1800 r / min, and dispersed for 30-40 min. The temperature in the kettle is controlled at 25-35°C by a temperature sensor, and the fineness is detected to be below 45 μm.

[0029] In the present invention, low-speed stirring is used to avoid the breakage of the hydroxyethyl cellulose molecular chain, and high-speed dispersion is used to break the pigment and filler agglomerates to a fineness of less than 45 μm, thereby forming a densely packed structure.

[0030] In some achievable embodiments, in step (4), a separate reaction vessel is used, the stirring speed is first set to 100-150 r / min, ethyl acetate accounting for 30%-40% of the total solvent in the coating formulation is added as a solvent, and the acrylate-silicone copolymer emulsion is slowly added, and stirring is continued for 15-20 minutes to ensure that the emulsion is fully dispersed in the solvent;

[0031] Then slowly add polyurethane modified acrylate resin at a rate of 5-10mL / min for 30-45 minutes. During the addition, increase the stirring speed to 200-250r / min to ensure that the two are fully mixed.

[0032] After the addition is complete, maintain the stirring speed at 150-200 r / min and continue stirring for 60-90 minutes to further evenly disperse the two substances;

[0033] After the two resins are fully mixed, the mixture is transferred to the reactor used in steps (1) to (3), and then the film-forming aid, propylene glycol, rheology modifier and remaining defoamer are added in sequence at a stirring speed of 150-200 r / min, and stirring is continued for 15-20 minutes.

[0034] In some achievable methods, in the initial stage of the reaction in step (4), the temperature in the reactor is controlled at 30-35°C and maintained for 30-45 minutes to avoid premature side reactions of the raw materials;

[0035] Then, the temperature is raised to 50-55°C at a rate of 1-2°C / min, and the reaction is carried out at this temperature for 120-180 minutes to promote the reaction between the acrylate-organic silicone copolymer emulsion and the polyurethane-modified acrylate resin;

[0036] Finally, the temperature is raised to 60-65°C and maintained for 60-90 minutes to ensure complete reaction. The reaction time is controlled within 240-360 minutes. During the reaction, samples are taken every 30-60 minutes to check for stratification and precipitation. After the reaction is completed, the samples are allowed to stand for 24-48 hours and the stratification is observed again. The viscosity and solid content performance indicators of the coating are tested, and the viscosity is 105±3KU, and the solid content is 50%-70%.

[0037] The present invention adopts segmented temperature control to match the reactivity of different chemical bonds. Silane copolymerization is first initiated at low temperature to avoid hydrolysis, then the urethane bond formation is promoted at medium temperature, and finally the silicon-oxygen bond condensation is completed at high temperature to ensure molecular-level mixing of the two-phase resin.

[0038] In some achievable embodiments, in step (5), the pH value is adjusted to 7.5-8.5 by adding dilute acid or dilute base.

[0039] In some achievable embodiments, the method for preparing the acrylate-silicone copolymer emulsion comprises the following steps:

[0040] (1) 60-70 parts by weight of an acrylic acid ester monomer, 5-15 parts by weight of an organosilicon monomer, 3-8 parts by weight of hydroxyethyl acrylate, 2-5 parts by weight of an emulsifier and 50-75 parts by weight of deionized water are mixed and pre-emulsified at a stirring speed of 300-500 rpm for 30-60 minutes to prepare a pre-emulsion; the pre-emulsification process disperses the monomer in nano-scale droplets, and the emulsifier stabilizes the latex particles through electrostatic repulsion and steric hindrance to prevent agglomeration.

[0041] (2) dissolving 0.3-1.0 parts by weight of an initiator in 50-75 parts by weight of deionized water to prepare an initiator solution;

[0042] (3) Add 1 / 3 volume of pre-emulsion and 0.1-0.5 parts by weight of buffer to the reactor, raise the temperature to 70-75°C, add 1 / 3 volume of initiator solution dropwise, and keep warm for 30 minutes; then, simultaneously add the remaining pre-emulsion and the remaining initiator solution dropwise over 2-3 hours, controlling the reaction temperature to 75-85°C; after the addition is complete, raise the temperature to 85-90°C and keep warm for 1-2 hours to obtain an acrylate-silicone copolymer emulsion with a weight-average molecular weight of 30,000-50,000. A three-stage temperature control is used to match the kinetics of silane bond hydrolysis and polymerization reactions to avoid gel defects caused by early cross-linking.

[0043] The present invention adopts a staged polymerization method, in which in the low-temperature initiation stage (70-75°C), 1 / 3 of the pre-emulsion is reacted with a buffer to form a seed emulsion; in the medium-temperature dropwise addition stage (75-85°C), the remaining pre-emulsion and the initiator are added dropwise simultaneously to control the free radical polymerization rate; in the high-temperature insulation stage (85-90°C), the condensation of silicon-oxygen bonds is promoted to ensure complete cross-linking.

[0044] In some achievable embodiments, the method for preparing the polyurethane-modified acrylate resin comprises the following steps:

[0045] (1) Preparation of hydroxyl-containing acrylate resin: 60-70 parts by weight of non-hydroxyl acrylate monomer, 10-20 parts by weight of hydroxyl acrylate monomer, 80-100 parts by weight of anhydrous solvent and 0.5-1.5 parts by weight of initiator are mixed, the temperature is raised to 80-90°C, the remaining monomer and initiator solution are added dropwise within 3-4 hours, and the mixture is kept warm for reaction to obtain a base resin having a hydroxyl content of 2-5% and a weight average molecular weight of 10,000-20,000, wherein the non-hydroxyl acrylate monomer comprises at least one of methyl methacrylate and butyl acrylate, and the hydroxyl acrylate monomer is hydroxyethyl acrylate;

[0046] (2) Preparation of polyurethane prepolymer: Under nitrogen protection, add 30-40 parts by weight of diisocyanate and 10-20 parts by weight of diol into a reactor, heat to 60-70°C, stir and react for 1-2 hours to obtain a polyurethane prepolymer;

[0047] (3) Modification reaction: Add the base resin to the polyurethane prepolymer and add 0.1-0.3 parts by weight of a catalyst. React at 60-80°C for 2-3 hours to obtain a polyurethane modified acrylate resin with a weight average molecular weight of 25,000-45,000. The -NCO / -OH molar ratio of the base resin to the prepolymer is 1.2-1.5:1.

[0048] Acrylate-silicone copolymer emulsions are pre-emulsified to form stable droplets, and the polymerization rate is controlled by staged addition to avoid gelation. Polyurethane-modified resins achieve a balanced balance of flexibility and rigidity by controlling the -NCO / -OH molar ratio within a range of 1.2-1.5:1 to adjust the crosslink density. During free radical polymerization, silanol bonds break to form free radicals, which copolymerize with the acrylate double bond to form a random copolymer. The glass transition temperature is determined by the monomer ratio. During addition polymerization, isocyanate groups react with hydroxyl groups to form urethane bonds. Nitrogen protection prevents the reaction of water with NCO to form CO2 bubbles.

[0049] The present invention achieves the construction of a network structure that combines both rigidity and flexibility through the use of an acrylate-silicone copolymer emulsion (flexible phase) and a polyurethane-modified acrylate resin (rigid phase). The silicone segments with a low glass transition temperature impart flexibility and elasticity to the coating at low temperatures, allowing the molecular segments to move even at low temperatures, effectively dispersing temperature stress and preventing cracking. The silicon-oxygen bonds of the silicone monomers enhance weather resistance and hydrophobicity, reducing damage to the coating caused by water penetration. The high glass transition temperature urethane bond structure forms a rigid cross-linked network, improving the coating's hardness, wear resistance, and acid and alkali corrosion resistance. The polar groups of the polyurethane enhance the interfacial bonding with pigments and fillers, improving the coating's adhesion and structural stability.

[0050] Through physical blending and chemical crosslinking, the two form an interpenetrating network, combining the low-temperature toughness of the flexible phase with the chemical resistance of the rigid phase. At low temperatures, the flexibility of the silicone segments offsets the brittleness of the polyurethane resin, preventing cracking in the coating. In acidic and alkaline environments, the urethane bonds of the polyurethane and the silicon-oxygen bonds of the silicone synergistically resist chemical attack and reduce molecular chain breakage.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] 1. The present invention forms a "rigid and flexible" structure by compounding an acrylate-organic silicone copolymer emulsion with a polyurethane-modified acrylate resin. At low temperatures, the silicone segments impart flexibility to the coating, allowing the molecular segments to move and effectively dissipate stress. This allows the prepared coating to remain crack-free for 24 hours at -30°C. In contrast, Comparative Example 1, containing only the flexible emulsion, exhibited slight cracking, Comparative Example 2, containing only the rigid resin, exhibited significant cracking, and Comparative Example 3, containing a conventional acrylic emulsion, exhibited severe cracking. This invention significantly improves the coating's low-temperature resistance.

[0053] 2. The present invention enhances weather resistance and hydrophobicity through the siloxy bonds of the organosilicon segments, while the urethane bonds of the polyurethane-modified acrylate resin form a rigid cross-linked network. These two components synergistically resist acid and alkali corrosion. After immersion in a 5% hydrochloric acid solution and a 5% sodium hydroxide solution for 7 days, the coating of the example exhibited a slight color change, no blistering or shedding, and a grade 0 adhesion. Comparative Example 1 lacked the rigid resin protection and had limited acid and alkali resistance. Comparative Example 2, while alkali-resistant, lacked the weather resistance of the organosilicon. Comparative Example 3, without any special modification, exhibited rapid degradation in acid and alkali conditions, demonstrating that the coating of the present invention exhibits outstanding acid and alkali resistance and is adaptable to harsh chemical environments.

[0054] 3. The present invention enhances the coating's hardness and wear resistance by compounding two resins to form a cross-linked network. Examples 1-3 achieve hardnesses of 2H-3H, good wear resistance, wear losses ≤ 0.15g / 10min, and minimal surface scratches. Comparative Example 1 lacks a rigid resin, resulting in a hardness of only HB and poor wear resistance. Comparative Example 2, while hard, suffers from poor flexibility and cracks at the edges upon wear. The conventional emulsion in Comparative Example 3 exhibits low film-forming strength and the worst wear resistance. This demonstrates that the present invention offers significant advantages in hardness and wear resistance, effectively protecting roofs. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 The present invention provides a process flow chart of a method for preparing a low-temperature resistant, acid- and alkali-resistant roof waterproof coating. DETAILED DESCRIPTION

[0056] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0057] Example 1: The present invention provides a low-temperature resistant and acid- and alkali-resistant roof waterproof coating, comprising the following raw material components in parts by weight:

[0058] 15 parts acrylate-organic silicone copolymer emulsion, 5 parts polyurethane-modified acrylate resin, 5 parts titanium dioxide, 8 parts ground calcium carbonate, 2 parts zinc oxide, 2 parts organic alcohol amine ether compound, 3 parts dispersant, 1 part defoamer, 1 part bactericide and mildew inhibitor, 2 parts film-forming aid, 2 parts rheology modifier, 0.5 parts hydroxyethyl cellulose, 2 parts propylene glycol, and 30 parts deionized water. The dispersant includes 1 part anionic dispersant sodium polyacrylate and 2 parts nonionic dispersant octylphenol polyoxyethylene ether; the defoamer includes 0.5 parts polydimethylsiloxane emulsion and 0.5 parts white oil emulsion; the bactericide and mildew inhibitor include 0.4 parts quaternary ammonium salt mildew inhibitor and 0.6 parts pyridine mildew inhibitor; the rheology modifier includes 1 part nonionic polyurethane associative thickener and 1 part hydroxyethyl cellulose.

[0059] The preparation method of the acrylate-silicone copolymer emulsion in this embodiment includes the following steps:

[0060] (1) Pre-emulsification: 60 parts of methyl methacrylate, 4 parts of ethyl acrylate, 5 parts of vinyltrimethoxysilane, 3 parts of hydroxyethyl acrylate, 2 parts of sodium lauryl sulfate and 50 parts of deionized water were mixed and stirred at 300 rpm for 60 minutes to obtain a pre-emulsion with a particle size of 85 nm.

[0061] (2) Segment aggregation:

[0062] Seed stage: Add 1 / 3 of the pre-emulsion and 0.1 parts of sodium bicarbonate to the reactor, heat to 70°C, add 1 / 3 of the volume of 0.3 parts of ammonium persulfate aqueous solution dropwise, and keep the reaction warm for 30 minutes.

[0063] Dropwise addition stage: the remaining pre-emulsion and initiator solution were added dropwise simultaneously within 2 hours, the temperature was controlled at 75°C, and the temperature was raised to 85°C after the dropwise addition was completed and kept warm for 1 hour to obtain a copolymer emulsion with a weight-average molecular weight of 30,000 and a glass transition temperature of -20°C. The molecular weight dispersity was 1.5, the glass transition temperature was measured to be -20°C by differential scanning calorimetry (DSC), and the silicon-oxygen bond content was quantitatively detected by infrared spectroscopy to be 6%.

[0064] The preparation method of the polyurethane modified acrylate resin in this embodiment comprises the following steps:

[0065] (1) Synthesis of hydroxyl resin: 60 parts of methyl methacrylate, 10 parts of hydroxyethyl acrylate, 80 parts of ethyl acetate and 0.5 parts of azobisisobutyronitrile were mixed and reacted at 80°C for 3 hours to obtain a base resin with a hydroxyl content of 2% and a weight-average molecular weight of 10,000.

[0066] (2) Preparation of prepolymer: Under nitrogen protection, 30 parts of toluene diisocyanate and 10 parts of polyethylene glycol (molecular weight 400) were added to the reactor and stirred at 60°C for 1 hour to obtain a prepolymer with an isocyanate group content of 3.5%.

[0067] (3) Modification reaction: The base resin and prepolymer were mixed at a molar ratio of isocyanate group to hydroxyl group of 1.2:1, 0.1 part of dibutyltin dilaurate was added, and the mixture was reacted at 60°C for 2 hours to obtain a modified resin with a weight average molecular weight of 25,000 and a molecular weight dispersion of 1.5. The glass transition temperature was measured by differential scanning calorimetry to be 10°C.

[0068] The preparation method of the coating in this embodiment comprises the following steps:

[0069] (1) Pre-dispersion: Add 30 parts of deionized water to the reactor and stir at a low speed of 300 r / min. Slowly add 0.5 parts of rheology modifier and continue stirring until it is completely dissolved to form a uniform colloidal solution. At this time, the solution has a certain viscosity. Then add 2 parts of triethanolamine and continue stirring for 10 minutes to further enhance the dispersion performance of the system, so that the organic alcohol amine ether compound is evenly dispersed in the solution, providing a stable dispersion environment for the subsequent addition of raw materials.

[0070] (2) Dispersion of additives: Increase the speed to 900 rpm and add dispersant, 0.4 parts of defoamer, and fungicide and mildew inhibitor in proportion. Stir for 20 minutes until uniform. The high stirring speed allows the dispersant to quickly adsorb on the surface of the pigment and filler, reducing its surface tension and promoting dispersion. The defoamer promptly eliminates bubbles generated during stirring to prevent them from adversely affecting subsequent dispersion and reaction. The fungicide and mildew inhibitor is evenly dispersed in the system, providing preliminary antibacterial and mildew protection for the coating. Continue stirring for 20 minutes to ensure that all additives are fully mixed.

[0071] (3) Dispersion of pigments and fillers: First, stir at a low speed of 300 r / min for 15 minutes to keep the reaction system in a mild stirring state, then add titanium dioxide, calcium carbonate, and zinc oxide, stir at a low speed for 15 minutes, and then quickly increase the speed to 1600 r / min. Under high-speed stirring, the pigment and filler particles are continuously refined and evenly dispersed in the coating system. The fineness is detected to be below 45 μm, ensuring that the dispersion effect of the pigments and fillers meets the requirements and that the smoothness and performance of the coating are not affected by large particles.

[0072] (4) Resin compounding: Mix 15 parts of acrylate-silicone copolymer emulsion and 5 parts of polyurethane modified acrylate resin at 100 rpm for 15 minutes, transfer to the reactor, add 2 parts of propylene glycol, the remaining 1.5 parts of rheology modifier and the remaining 0.6 parts of defoamer, stir for 15 minutes, and filter the material.

[0073] During the reaction, temperature and time are strictly controlled. Initially, the temperature in the reactor is maintained at 30°C for 30 minutes to prevent premature side reactions in the raw materials. The temperature is then slowly raised to 50°C at a rate of 1°C / min, and the reaction is carried out at this temperature for 120 minutes. This promotes the full chemical reaction between the acrylate-silicone copolymer emulsion and the polyurethane-modified acrylate resin, allowing the molecular chains of the two resins to intertwine and react, forming a stable structure. Finally, the temperature is raised to 60°C and maintained for 60 minutes to ensure complete reaction. During the reaction, samples are taken every 30 minutes to inspect the appearance of the samples for stratification and precipitation. After the reaction is complete, the samples are allowed to stand for 24 hours, and stratification is again observed. The coating's performance indicators, such as viscosity and solids content, are then tested, with the viscosity measured at 104KU and the solids content at 50%.

[0074] (5) Performance Control: By adding a small amount of deionized water, the coating viscosity is precisely adjusted to 105KU, giving the coating a good construction consistency and facilitating brushing. Dilute alkali is added to adjust the pH value to 7.5, keeping the coating within the appropriate pH range to reduce self-corrosion to the coating. Finally, the material is filtered to remove any impurities, resulting in the finished waterproof coating.

[0075] Example 2: This example is basically consistent with Example 1, with the difference being that the low-temperature resistant, acid- and alkali-resistant roof waterproof coating of this example comprises the following raw material components in parts by weight: 20 parts of acrylate-silicone copolymer emulsion, 10 parts of polyurethane-modified acrylate resin, 8 parts of titanium dioxide, 12 parts of heavy calcium carbonate, 3 parts of zinc oxide, 3 parts of organic alcohol amine ether compound, 4 parts of dispersant, 2 parts of defoaming agent, 2 parts of bactericidal and mildew-proof agent, 3 parts of film-forming aid, 3 parts of rheology modifier, 3 parts of propylene glycol, and 40 parts of deionized water. The dispersant includes 1.3 parts of anionic dispersant alkylnaphthalene sulfonate and 2.7 parts of nonionic dispersant fatty alcohol polyoxyethylene ether; the defoamer includes 1.2 parts of polyether modified silicone oil and 0.8 parts of paraffin oil compound emulsion; the bactericidal and mildewproof agent includes 0.8 parts of isothiazolinone mildewproof agent and 1.2 parts of azole mildewproof agent; the rheology modifier includes 1.4 parts of nonionic polyurethane associative thickener and 1.6 parts of hydroxypropyl methylcellulose.

[0076] The preparation method of the acrylate-silicone copolymer emulsion in this embodiment includes the following steps:

[0077] (1) Pre-emulsification: Mix 65 parts of ethyl acrylate, 10 parts of methyl methacrylate, 10 parts of vinyltrimethoxysilane, 5 parts of hydroxyethyl acrylate, 3 parts of OP-10 and 60 parts of deionized water, and stir at 400 rpm for 45 minutes to prepare a pre-emulsion.

[0078] (2) Segment aggregation:

[0079] Seed stage: Add 1 / 3 of the pre-emulsion and 0.2 parts of sodium bicarbonate to the reactor, heat it to 72°C, add 1 / 3 of the volume of 0.6 parts of ammonium persulfate aqueous solution dropwise, and keep the reaction warm for 30 minutes.

[0080] Dropwise addition stage: the remaining pre-emulsion and initiator solution were added dropwise simultaneously within 2.5 hours, the temperature was controlled at 80°C, and after the dropwise addition was completed, the temperature was raised to 88°C and kept warm for 1.5 hours to obtain a copolymer emulsion with a weight-average molecular weight of 40,000 and a glass transition temperature of -15°C. The molecular weight dispersion was 1.7.

[0081] The preparation method of the polyurethane modified acrylate resin in this embodiment comprises the following steps:

[0082] (1) Synthesis of hydroxyl resin: 65 parts of butyl acrylate, 15 parts of hydroxyethyl acrylate, 90 parts of ethyl acetate and 1 part of initiator were mixed and reacted at 85°C for 3.5 hours to obtain a base resin with a hydroxyl content of 3.5% and a weight-average molecular weight of 15,000.

[0083] (2) Preparation of prepolymer: Under nitrogen protection, 35 parts of isophorone diisocyanate and 15 parts of polyethylene glycol (molecular weight 600) were added to the reactor and stirred at 65°C for 1.5 hours to obtain the prepolymer.

[0084] (3) Modification reaction: The base resin and prepolymer were mixed at a molar ratio of isocyanate group to hydroxyl group of 1.3:1, 0.2 parts of catalyst was added, and the mixture was reacted at 70°C for 2.5 hours to obtain a modified resin with a weight-average molecular weight of 35,000 and a glass transition temperature of 15°C. The molecular weight dispersion was 1.7.

[0085] The preparation method of the polyurethane modified acrylate resin in this embodiment comprises the following steps:

[0086] (1) Pre-dispersion: Add deionized water to the reactor, add 1 part of rheology modifier under stirring at 300 rpm, add diethanolamine after dissolution, and stir for 12 minutes.

[0087] (2) Dispersion of auxiliary agents: Increase the speed to 900 rpm, add dispersant, 1.2 parts of defoaming agent, and bactericide and mildew inhibitor in proportion, and stir for 25 minutes.

[0088] (3) Dispersion of pigments and fillers: Add titanium dioxide, calcium carbonate and zinc oxide in proportion, stir at low speed for 18 minutes, and then disperse at high speed (1700 rpm) for 35 minutes. The fineness is tested to 40 μm.

[0089] (4) Resin compounding: Mix 20 parts of copolymer emulsion with 10 parts of modified resin at 120 rpm for 20 minutes, transfer to the reactor, add 3 parts of propylene glycol, the remaining rheology modifier and defoamer, stir for 18 minutes, and filter the material.

[0090] (5) Performance Control: Based on the test results, the coating viscosity was fine-tuned to 105KU by adding an appropriate amount of rheology modifier and the pH value was adjusted to 8.0 by adding dilute acid to optimize the coating performance. Finally, the material was filtered to obtain a waterproof coating with excellent performance.

[0091] Example 3: This example is essentially the same as Example 1, except that the low-temperature, acid- and alkali-resistant roof waterproof coating of this example comprises the following raw materials, in parts by weight: 25 parts of acrylate-organic silicone copolymer emulsion, 15 parts of polyurethane-modified acrylate resin, 10 parts of titanium dioxide, 15 parts of ground calcium carbonate, 5 parts of zinc oxide, 5 parts of an organic alcohol amine ether compound, 6 parts of a dispersant, 3 parts of a defoamer, 3 parts of a fungicide and mildew inhibitor, 4 parts of a film-forming aid, 5 parts of a rheology modifier, 5 parts of propylene glycol, and 50 parts of deionized water. The dispersant comprises 2 parts of an anionic dispersant (alkyl naphthalene sulfonate) and 4 parts of a nonionic dispersant (fatty alcohol polyoxyethylene ether); the defoamer comprises a composite emulsion of 2 parts of polyether-modified silicone oil and 1 part of paraffin oil; the fungicide and mildew inhibitor comprises 1.2 parts of an isothiazolinone mildew inhibitor and 1.8 parts of an azole mildew inhibitor; and the rheology modifier comprises 2.3 parts of a nonionic polyurethane associative thickener and 2.7 parts of hydroxypropyl methylcellulose.

[0092] The preparation method of the acrylate-silicone copolymer emulsion in this embodiment includes the following steps:

[0093] (1) Pre-emulsification: Mix 70 parts of methyl methacrylate, 15 parts of ethyl acrylate, 15 parts of vinyltrimethoxysilane, 8 parts of hydroxyethyl acrylate, 5 parts of sodium lauryl sulfate and 75 parts of deionized water, and stir at 500 rpm for 30 minutes to prepare a pre-emulsion.

[0094] (2) Segment aggregation:

[0095] Seed stage: Add 1 / 3 of the pre-emulsion and 0.5 parts of sodium bicarbonate to the reactor, heat to 75°C, add 1 / 3 volume of 1.0 parts of ammonium persulfate aqueous solution dropwise, and keep warm for 30 minutes.

[0096] Dropwise addition stage: the remaining pre-emulsion and initiator solution were added dropwise simultaneously within 3 hours, the temperature was controlled at 85°C, and after the addition was completed, the temperature was raised to 90°C and kept warm for 2 hours to obtain a copolymer emulsion with a weight average molecular weight of 50,000 and a glass transition temperature of -10°C.

[0097] The preparation method of the polyurethane modified acrylate resin in this embodiment comprises the following steps:

[0098] (1) Synthesis of hydroxyl resin: 70 parts of butyl acrylate, 20 parts of hydroxyethyl acrylate, 100 parts of ethyl acetate and 1.5 parts of initiator were mixed and reacted at 90°C for 4 hours to obtain a base resin with a hydroxyl content of 5% and a weight-average molecular weight of 20,000.

[0099] (2) Preparation of prepolymer: Under nitrogen protection, 40 parts of toluene diisocyanate and 20 parts of polyethylene glycol (molecular weight 800) were added to the reactor and stirred at 70°C for 2 hours to obtain the prepolymer.

[0100] (3) Modification reaction: The base resin and prepolymer were mixed at a molar ratio of isocyanate group to hydroxyl group of 1.5:1, 0.3 parts of catalyst was added, and the mixture was reacted at 80°C for 3 hours to obtain a modified resin with a weight average molecular weight of 45,000 and a glass transition temperature of 20°C.

[0101] The preparation method of the coating in this embodiment comprises the following steps:

[0102] (1) Pre-dispersion: Add 50 parts of deionized water to the reactor, add 1.5 parts of rheology modifier under stirring at 500 rpm, add 5 parts of organic alcohol amine ether compound after dissolution, and stir for 15 minutes.

[0103] (2) Dispersion of additives: Increase the speed to 900 rpm, add 6 parts of dispersant, 1.5 parts of defoamer, and 1.5 parts of bactericide and mildew inhibitor in sequence, and stir for 30 minutes.

[0104] (3) Dispersion of pigments and fillers: Add 10 parts of titanium dioxide, 15 parts of calcium carbonate, and 5 parts of zinc oxide, stir at low speed for 20 minutes, and then disperse at high speed (1800 rpm) for 40 minutes. The fineness is tested to 35 μm.

[0105] (4) Resin compounding: Mix 25 parts of copolymer emulsion with 15 parts of modified resin at 150 rpm for 25 minutes, transfer to the reactor, add 4 parts of propylene glycol, the remaining rheology modifier and defoamer, stir for 20 minutes, and filter the material.

[0106] During the initial reaction, the temperature was maintained at 35°C for 45 minutes. The temperature was then raised to 55°C at a rate of 2°C / min and allowed to react for 180 minutes. Finally, the temperature was raised to 65°C and maintained for 90 minutes. Samples were taken every 60 minutes to check for stratification and precipitation. After the reaction, the samples were allowed to stand for 48 hours and observed again for stratification. The coating's viscosity was 106 kU and its solids content was 70%.

[0107] (5) Performance control: The coating viscosity was adjusted to 105KU by adding a small amount of deionized water, the pH value was adjusted to 8.5 by adding dilute alkali, and the material was finally filtered to obtain a waterproof coating that met the performance requirements.

[0108] Comparative Example 1: The difference between Comparative Example 1 and the embodiment is that only acrylate-silicone copolymer emulsion (flexible phase) is used, and no polyurethane-modified acrylate resin (rigid phase) is added. The preparation method of the coating is basically the same as that of Example 1, and pre-dispersion, auxiliary agent dispersion, and pigment and filler dispersion are carried out in sequence.

[0109] The difference is that in this comparative example, only the acrylate-silicone copolymer emulsion was added during the emulsion and functional additive compounding step. The film-forming agent, propylene glycol, rheology modifier, and defoamer were then added sequentially and stirred until uniformly mixed. The coating viscosity was controlled at 105 ± 3 kU, the pH was adjusted to 7.5-8.5, and the material was finally filtered.

[0110] Performance Estimates:

[0111] 1. Low temperature resistance: Because the glass transition temperature of acrylate-silicone copolymer emulsion itself is low, the molecular chain segments still have a certain mobility at low temperatures and can effectively absorb and disperse external stress.

[0112] 2. Acid and alkali resistance: Although acrylate-silicone copolymer emulsion has certain water resistance and weather resistance, its acid and alkali resistance is limited under long-term acid and alkali erosion and cannot provide sufficient protection.

[0113] 3. Hardness and wear resistance: Due to the lack of polyurethane modified acrylate resin, sufficient rigid structure and cross-linking points are not formed in the coating, and it cannot effectively resist friction and scratches caused by external forces.

[0114] Comparative Example 2: The difference between Comparative Example 2 and the embodiment is that only polyurethane-modified acrylate resin (rigid phase) is used, and acrylate-silicone copolymer emulsion (flexible phase) is not added. The preparation method of the coating is basically the same as that of Example 1, and pre-dispersion, auxiliary agent dispersion, and pigment and filler dispersion are carried out in sequence.

[0115] The difference is that in this comparative example, in the step of compounding the emulsion and the functional additives, only the polyurethane-modified acrylate resin is added, and then other additives are added and stirred evenly, and the material is filtered and discharged after the performance adjustment is completed.

[0116] Performance Estimates:

[0117] 1. Low temperature resistance: Because the glass transition temperature of polyurethane modified acrylate resin is relatively high, the molecular chain segments have difficulty moving at low temperatures and cannot adapt to the stress generated by temperature changes, resulting in increased brittleness of the coating and easy cracking.

[0118] 2. Acid and alkali resistance: The stability of the urethane bond in polyurethane modified acrylate resin can effectively resist the erosion of acid and alkali substances.

[0119] 3. Flexibility: Due to the structural characteristics of polyurethane-modified acrylic resin itself, it sacrifices some flexibility while providing hardness and strength.

[0120] Comparative Example 3: The difference between Comparative Example 3 and the embodiment is that not only does not use acrylate-silicone copolymer emulsion, but also does not use polyurethane-modified acrylate resin, but instead uses ordinary acrylic emulsion to completely replace the two core resins, as follows:

[0121] Raw material preparation: Weigh 25 parts of a common acrylic emulsion (with parameters such as weight-average molecular weight and glass transition temperature different from those in the examples) to replace the acrylate-silicone copolymer emulsion and polyurethane-modified acrylate resin in the invention. The acrylic emulsion is manufactured by Beijing Huacai Paint Technology Co., Ltd. and is produced under the brand name BJ-PA-03.

[0122] The types, amounts and specifications of other raw materials (titanium dioxide, heavy calcium carbonate, etc.) are the same as those in Example 1.

[0123] The coating in this comparative example was prepared according to the preparation method of the embodiment, including the steps of pre-dispersion, dispersion of additives, dispersion of pigments and fillers, compounding of emulsion and functional additives, and performance control.

[0124] Performance Estimates:

[0125] 1. Low temperature resistance: Ordinary acrylic emulsion has a high glass transition temperature and cannot maintain good flexibility at low temperatures, and cannot meet the requirements of low temperature resistance.

[0126] 2. Acid and alkali resistance: Ordinary acrylic emulsions lack silicone monomers and polyurethane modified structures, and their acid and alkali resistance is far inferior to that of the coating in the invention.

[0127] 3. Overall performance: The coating performs poorly in terms of film-forming properties, hardness, and abrasion resistance. The film strength after film formation is low and easily scratched, making it unable to effectively protect the roof.

[0128] In order to compare and test the low temperature resistance, acid and alkali resistance, hardness and wear resistance of the coatings prepared in the above examples and comparative examples, the following test methods are provided:

[0129] 1. Low temperature resistance test:

[0130] 1. Specimen specifications and dimensions

[0131] Base material: standard cement mortar board (size: 100mm×100mm×10mm, in line with GB / T17671-1999 standard).

[0132] Coating thickness: The wet film thickness is controlled at (200±20) μm, and the dry film thickness after drying is approximately (100±10) μm (calibrated using a wet film thickness gauge and a dry film thickness gauge).

[0133] 2. Specific test methods

[0134] Sample preparation: Apply the coating evenly on the surface of the cement mortar board and cure it at room temperature (23±2℃, relative humidity 50±5%) for 7 days to ensure that the coating is completely dry and forms a film.

[0135] Low-temperature treatment: Place the specimen in a low-temperature test chamber (accuracy ±1°C) and cool it to -30°C at a rate of 1°C / min for 24 hours. Place silica gel desiccant in the chamber to prevent condensation from affecting the coating.

[0136] Observation and evaluation: Take out the test piece, place it at room temperature for 2 hours, and observe the coating surface with a 5x magnifying glass.

[0137] Judgment criteria:

[0138] Excellent: no cracking, no peeling;

[0139] Good: 1-2 fine lines (length ≤ 5mm);

[0140] Poor: more than 3 cracks or peeling area >5%.

[0141] 2. Acid and alkali resistance test:

[0142] 1. Specimen specifications and dimensions

[0143] Base material: Q235 carbon steel plate (size: 150mm×70mm×2mm, surface sandblasted).

[0144] Coating thickness: Dry film thickness (200±20) μm (measured by a magnetic thickness gauge).

[0145] 2. Specific test methods

[0146] Sample preparation: Apply the coating evenly on the surface of the steel plate, cure at room temperature for 7 days, and seal the edge of the specimen with paraffin after drying (leaving a 50mm×50mm test area).

[0147] Immersion test:

[0148] Acid solution: 5% hydrochloric acid solution, the volume of the solution should immerse the test area of the specimen ≥ 20mm.

[0149] Alkali solution: 5% sodium hydroxide solution, the volume of the solution is the same as that of the acid solution.

[0150] The two groups of specimens were immersed in acid and alkali solutions respectively at a constant temperature of 23±2℃ for 7 days without changing the solution.

[0151] Performance evaluation:

[0152] Appearance inspection: Remove the test piece, rinse it with clean water and dry it, then observe the coating color change (ΔE value is measured using a colorimeter), blistering (bubble diameter and density), and peeling area.

[0153] Adhesion test: The cross-cut test was carried out in accordance with GB / T9286-1998 "Determination of Adhesion of Paints and Varnishes - Cross-cut Method", using a 1mm spacing cutter. Rating criteria:

[0154] Level 0: The cutting edge is completely smooth, with no coating falling off;

[0155] Level 1: A small amount of coating falls off at the cutting intersection, with an area of ≤5%;

[0156] Level 4: The coating falls off over a large area, with the area > 65%.

[0157] Hardness test (pencil hardness method)

[0158] 1. Specimen specifications and dimensions

[0159] Substrate: 3 mm thick transparent organic glass plate (size: 100 mm × 100 mm).

[0160] Coating thickness: Dry film thickness (80±10) μm (measured by eddy current thickness gauge).

[0161] 2. Specific test methods

[0162] Sample preparation: Apply the coating evenly on the surface of the organic glass plate and cure at room temperature for 7 days.

[0163] Test steps:

[0164] According to GB / T6739-2006 “Paints and varnishes - Determination of film hardness by pencil method”, high-grade Zhonghua brand drawing pencils (hardness grades from 6B to 6H) were used.

[0165] The pencil is at a 45° angle to the coating surface, a pressure of about 1 kg is applied, and it is advanced at a speed of 1 mm / s. Each hardness level is tested 3 times.

[0166] Judgment criteria:

[0167] The highest pencil hardness level without scratches in the three tests is taken as the coating hardness value (for example, a 3H pencil has no scratches, and a 4H pencil has scratches, then the hardness is 3H).

[0168] 4. Abrasion resistance test (falling sand method)

[0169] 1. Specimen specifications and dimensions

[0170] Substrate: 5mm thick concrete slab (size: 150mm×150mm, surface polished).

[0171] Coating thickness: Dry film thickness (300±30) μm (measured by ultrasonic thickness gauge).

[0172] 2. Specific test methods

[0173] Sample preparation: Apply the coating evenly on the surface of the concrete slab and cure at room temperature for 14 days.

[0174] Test setup:

[0175] Falling sand abrasion tester (compliant with ASTM D968 standard), the sand particles are 20-30 mesh quartz sand, the falling sand height is 500mm, and the sand flow rate is controlled at 200g / min.

[0176] Test steps:

[0177] Fix the specimen horizontally under the instrument, turn on the sand falling device, and continue abrasion for 10 minutes.

[0178] Collect the sand particles and coating debris after wear, weigh the mass of the specimen before and after wear using an analytical balance, and calculate the wear amount (g / 10min).

[0179] Judgment criteria:

[0180] A wear loss of 0.15 g / 10 min or less is excellent, 0.15-0.3 g / 10 min is good, and >0.3 g / 10 min is poor.

[0181] Note: All tests must be performed in a standard laboratory environment (temperature 23±2°C, relative humidity 50±5%) to avoid environmental factors interfering with the results.

[0182] The following are experimental data of performance comparison tests of Examples and Comparative Examples:

[0183] 1. Low temperature resistance test data

[0184]

[0185] 2. Acid and alkali resistance test data

[0186]

[0187] 3. Hardness and wear resistance experimental data

[0188]

[0189] Combined with the above experimental data, the performance analysis of the coatings prepared in the examples and comparative examples is as follows:

[0190] Low temperature resistance: Examples 1-3 contain both low glass transition temperature acrylate-silicone copolymer emulsion and rigid polyurethane modified acrylate resin, forming a "rigid and flexible" structure. The molecular chain segments maintain mobility at low temperatures without cracking.

[0191] Comparative Example 1 contains only flexible emulsion, which has insufficient stress dispersion ability at low temperatures (slight cracking); Comparative Example 2 contains only rigid resin, has a high glass transition temperature (10°C~20°C), and is significantly brittle at low temperatures; Comparative Example 3 contains ordinary acrylic emulsion with an even higher glass transition temperature and cannot adapt to low-temperature deformation.

[0192] Acid and alkali resistance: The silicone segments and urethane bonds in the examples work together to resist acid and alkali erosion, and have excellent adhesion; Comparative Example 1 lacks rigid resin protection, and the emulsion molecular chains are easily destroyed by acids and alkalis; Comparative Example 2 has better alkali resistance due to its polyurethane structure, but lacks the weather resistance of silicone; Comparative Example 3 has no special modification, and the coating quickly fails under acid and alkali conditions.

[0193] Hardness and wear resistance: The embodiment forms a cross-linked network through resin compounding, and has excellent hardness (2H~3H) and wear resistance (wear amount ≤0.15g); Comparative Example 1 lacks rigid resin and has a hardness of only HB; Comparative Example 2 has a high hardness (3H), but poor flexibility, resulting in edge cracking during wear; Comparative Example 3 has low film-forming strength of ordinary emulsion and the worst wear resistance.

[0194] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A low-temperature resistant acid and alkali resistant roof waterproof coating, characterized in that: Including raw material components in parts by weight: 15-25 parts of acrylate-organic silicone copolymer emulsion, 5-15 parts of polyurethane-modified acrylate resin, 5-10 parts of titanium dioxide, 8-15 parts of heavy calcium carbonate, 2-5 parts of zinc oxide, 2-5 parts of organic alcohol amine ether compound, 3-6 parts of dispersant, 1-3 parts of defoamer, 1-3 parts of bactericide and mildewproofing agent, 2-4 parts of film-forming aid, 2-5 parts of rheology modifier, 2-5 parts of propylene glycol, and 30-50 parts of solvent; The raw materials of the acrylate-organic silicone copolymer emulsion include 60-70 parts by weight of acrylate monomer, 5-15 parts by weight of organosilicon monomer, 3-8 parts by weight of hydroxyethyl acrylate, 2-5 parts by weight of emulsifier and 0.3-1.0 parts by weight of initiator, and are prepared by free radical polymerization, wherein the organosilicon monomer is introduced into the copolymer segment through a silicon-oxygen bond, the glass transition temperature is controlled to be -20°C to -10°C, and the molecular weight dispersion is 1.5-2.0; The polyurethane-modified acrylate resin comprises raw materials including 60-70 parts by weight of a non-hydroxyl acrylate monomer, 10-20 parts by weight of a hydroxyl acrylate monomer, 30-40 parts by weight of a diisocyanate, and 10-20 parts by weight of a diol, and is prepared by addition polymerization. The molar ratio of isocyanate groups to hydroxyl groups is 1.2-1.5:1, the glass transition temperature is controlled at 10°C to 20°C, and the molecular weight dispersion is 1.5-2.

0.

2. The low-temperature resistant, acid- and alkali-resistant roof waterproof coating according to claim 1, characterized in that: The dispersant is a compound of anionic dispersant and nonionic dispersant, and the weight ratio of the two is 1: (1-2); The anionic dispersant is selected from one or more of sodium polyacrylate, alkylnaphthalene sulfonate, and lignin sulfonate, and the nonionic dispersant is selected from one or more of octylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, and polyoxyethylene ethers.

3. The low-temperature resistant, acid- and alkali-resistant roof waterproof coating according to claim 1, characterized in that: The defoamer is a compound of an organosilicon defoamer and a mineral oil defoamer, and the weight ratio of the two is (5-7): (3-5); The organosilicon defoamer is selected from one or more of polydimethylsiloxane emulsion, polyether modified silicone oil, and self-emulsifying organosilicon defoamer; the mineral oil defoamer is selected from one or more of white oil, paraffin oil, and emulsion defoamers compounded with surfactants.

4. The low-temperature resistant, acid- and alkali-resistant roof waterproof coating according to claim 1, characterized in that: The rheology modifier is a compound of an associative thickener and a cellulose ether thickener, and the weight ratio of the two is 1:(1-1.2); The associative thickener is selected from one or more of a nonionic polyurethane associative thickener, a hydrophobically modified alkali swellable thickener, and a hydrophobically modified cellulose ether; The cellulose ether thickener is selected from one or more of hydroxyethyl cellulose, hydroxypropyl methyl cellulose, and ethyl hydroxyethyl cellulose; And / or, the weight ratio of the components targeting bacteria and mold in the bactericidal and mildew-proof agent is 1:(1-1.5), the component targeting bacteria is selected from one of quaternary ammonium salts and isothiazolinones, and the component targeting mold is selected from one of pyridines and azoles.

5. A method for preparing the low-temperature resistant acid and alkali resistant roof waterproof coating according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) Pre-dispersion: Add deionized water into the reactor and add part of the rheology modifier and organic alcohol amine ether compound in sequence during the stirring process; (2) Dispersion of auxiliary agents: Add dispersant, part of defoamer, and bactericide and mildew-proof agent to the above mixture in sequence and continue stirring; (3) Pigment and filler dispersion: Add titanium dioxide, heavy calcium carbonate, and zinc oxide to the mixture of step (2) and continue stirring; (4) Compounding of emulsion and functional additives: First, fully mix the acrylate-silicone copolymer emulsion and the polyurethane-modified acrylate resin, then transfer the mixture to the reactor of step (3), and add the film-forming additive, propylene glycol, the remaining rheology modifier and defoamer in sequence, continue stirring, and finally filter the material; The acrylate-organic silicone copolymer emulsion utilizes the siloxane bond of the organosilicon monomer to break under the action of an initiator to form free radicals, which copolymerize with the carbon-carbon double bonds of the acrylate monomer and hydroxyethyl acrylate to form copolymer segments containing siloxane bonds; The polyurethane modified acrylate resin utilizes an addition reaction between the isocyanate group in the polyurethane prepolymer and the hydroxyl group in the acrylate resin to generate a urethane bond.

6. The preparation method according to claim 5, characterized in that: After adding the rheology modifier in step (1), stirring at a low speed of 300-500 r / min until completely dissolved, adding the organic alcohol amine ether compound, and continuing stirring for 10-15 minutes; And / or, in step (2), after increasing the rotation speed to 900 r / min, dispersant, defoamer, bactericide and mildewicide are added in sequence and stirred for 20-30 minutes until uniform; And / or, in step (3), after stirring at a low speed of 300-500 r / min for 15-20 min, titanium dioxide, heavy calcium carbonate and zinc oxide are added, and the speed is increased to 1600-1800 r / min, and dispersed for 30-40 min. The temperature in the kettle is controlled at 25-35°C by a temperature sensor, and the fineness is detected to be below 45 μm.

7. The preparation method according to claim 6, characterized in that: In step (4), the stirring speed is first set to 100-150 r / min, ethyl acetate is added as a solvent, and the acrylate-silicone copolymer emulsion is slowly added, and stirring is continued for 15-20 minutes; Then, slowly add the polyurethane modified acrylate resin at a rate of 5-10 mL / min for 30-45 minutes. During the addition, increase the stirring speed to 200-250 r / min. After the addition is completed, maintain the stirring speed at 150-200 r / min and continue stirring for 60-90 minutes. After the two resins are fully mixed, the mixture is transferred to the reactor used in step (3), and the film-forming aid, propylene glycol, the remaining rheology modifier and defoamer are added in sequence, and stirring is continued for 15-20 minutes.

8. The preparation method according to claim 7, characterized in that: In the initial stage of the reaction in step (4), the temperature in the reactor is controlled at 30-35°C and maintained for 30-45 minutes; then the temperature is raised to 50-55°C at a rate of 1-2°C / min, and the reaction is carried out at this temperature for 120-180 minutes; finally, the temperature is raised to 60-65°C and maintained for 60-90 minutes.

9. The preparation method according to claim 8, characterized in that: The preparation method of the acrylate-organic silicone copolymer emulsion comprises the following steps: (1) Mix 60-70 parts by weight of an acrylic acid ester monomer, 5-15 parts by weight of an organosilicon monomer, 3-8 parts by weight of hydroxyethyl acrylate, 2-5 parts by weight of an emulsifier, and 50-75 parts by weight of deionized water, and pre-emulsify the mixture at a stirring speed of 300-500 rpm for 30-60 minutes to prepare a pre-emulsion; (2) dissolving 0.3-1.0 parts by weight of an initiator in 50-75 parts by weight of deionized water to prepare an initiator solution; (3) Add 1 / 3 volume of pre-emulsion and 0.1-0.5 parts by weight of buffer into the reactor, heat to 70-75°C, add 1 / 3 volume of initiator solution dropwise, and keep warm for 30 minutes; then add the remaining pre-emulsion and the remaining initiator solution dropwise simultaneously within 2-3 hours, and control the reaction temperature to 75-85°C; after the addition is completed, heat to 85-90°C and keep warm for 1-2 hours to obtain an acrylate-silicone copolymer emulsion with a weight average molecular weight of 30,000-50,000.

10. The preparation method according to any one of claims 5 to 9, characterized in that: The preparation method of the polyurethane modified acrylate resin comprises the following steps: (1) Preparation of hydroxyl-containing acrylate resin: 60-70 parts by weight of non-hydroxyl acrylate monomer, 10-20 parts by weight of hydroxyl acrylate monomer, 80-100 parts by weight of anhydrous solvent and 0.5-1.5 parts by weight of initiator are mixed, the temperature is raised to 80-90°C, the remaining monomer and initiator solution are added dropwise within 3-4 hours, and the mixture is kept warm for reaction to obtain a base resin having a hydroxyl content of 2-5% and a weight average molecular weight of 10,000-20,000, wherein the non-hydroxyl acrylate monomer comprises at least one of methyl methacrylate and butyl acrylate, and the hydroxyl acrylate monomer is hydroxyethyl acrylate; (2) Preparation of polyurethane prepolymer: Under nitrogen protection, add 30-40 parts by weight of diisocyanate and 10-20 parts by weight of diol into a reactor, heat to 60-70°C, stir and react for 1-2 hours to obtain a polyurethane prepolymer; (3) Modification reaction: Add the base resin to the polyurethane prepolymer and add 0.1-0.3 parts by weight of a catalyst, react at 60-80°C for 2-3 hours to obtain a polyurethane modified acrylate resin with a weight average molecular weight of 25,000-45,000, and the -NCO / -OH molar ratio of the base resin to the prepolymer is 1.2-1.5:1.

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