Low-temperature-resistant acid-alkali-resistant roof waterproof coating and preparation method thereof

Abstract

The invention discloses a low-temperature-resistant, acid-resistant and alkali-resistant roof waterproof coating and a preparation method thereof. The coating is prepared from various raw materials such as acrylate-organosilicone copolymer emulsion and polyurethane modified acrylate resin, and a key raw material is prepared through free radical polymerization and addition polymerization reaction. The preparation method comprises the steps of pre-dispersion, auxiliary agent dispersion, pigment and filler dispersion, emulsion and functional auxiliary agent compounding, performance regulation and control and the like. The acrylate-organic silicon copolymer emulsion and the polyurethane modified acrylate resin form an interpenetrating network through physical blending and chemical crosslinking, and the low-temperature toughness of a flexible phase and the chemical resistance of a rigid phase are both achieved. In a low-temperature environment, the rigidity embrittlement of the polyurethane resin is counteracted by the flexibility of the organosilicone chain segment, so that the cracking of the coating is avoided; in an acid-base environment, a urethane bond of polyurethane and a silicon-oxygen bond of organic silicon cooperate to resist chemical erosion, molecular chain breakage is reduced, and the problem that an existing waterproof coating is insufficient in performance in the low-temperature and acid-base environment is effectively solved.

Description

Technical Field

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

[0002] In the construction field, roof waterproofing is a key link to ensure the safety and normal use of buildings. With the development of the construction industry, the performance requirements for roof waterproof coatings are becoming increasingly stringent. Currently, ordinary roof waterproof coatings on the market expose many problems when facing complex usage environments. For example, in low-temperature environments, the flexibility of ordinary waterproof coatings will significantly deteriorate. When the temperature is lower than its glass transition temperature, the movement ability of polymer chain segments is limited, and the stress inside the coating cannot be effectively released, resulting in the coating being extremely prone to cracking under temperature changes or slight external stretching. Once the coating cracks, the waterproof function will fail, and water will penetrate into the roof structure, eroding the main structure of the building and shortening the service life of the building. In acid-alkali environments, such as in areas with severe industrial pollution, acidic gases in the air (such as sulfur dioxide, nitrogen oxides, etc.) react with water to form acid rain, and acid-alkali substances around some special buildings (such as chemical plants, laboratories, etc.) will corrode the waterproof coating. Acid-alkali substances will damage the molecular structure of the coating, break the chemical bonds of the coating, resulting in a decline in the performance of the coating such as strength and adhesion, and the coating will gradually be eroded and peeled off, greatly shortening the service life of the waterproof coating, increasing the building maintenance cost, and even posing a threat to the structural safety of the building.

[0003] Although there are some low-temperature resistant coatings and acid-alkali resistant coatings in the prior art, it is often difficult to meet both performance requirements simultaneously. Coatings with both low-temperature resistance and acid-alkali resistance face many difficulties in the research and development and production processes. 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 vulnerable in acid-alkali environments; on the other hand, to enhance the acid-alkali resistance of the coating, highly cross-linked polymers or a large amount of corrosion-resistant fillers are generally used, which may also lead to poor flexibility of the coating and easy cracking 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-alkali resistance, construction performance, film-forming performance, cost, etc.

[0004] Therefore, how to simultaneously solve the improvement of the comprehensive performance of the coating in terms of low-temperature resistance and acid-alkali resistance is a difficult problem that needs to be urgently solved by those skilled in the art. Summary of the Invention

[0005] The object of the present invention is to provide a low-temperature resistant and acid-alkali resistant roof waterproof coating and its preparation method, aiming to solve the problems that the flexibility of existing waterproof coatings becomes poor and is prone to cracking in low-temperature environments, and the molecular structure is damaged and the performance decreases in acid-alkali environments, meet the waterproof requirements 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: In the first aspect, the present invention provides a low-temperature resistant and acid-alkali resistant roof waterproof coating, which comprises the following raw material components in parts by weight: 15 - 25 parts of acrylate-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 alkanolamine ether compounds, 3 - 6 parts of dispersant, 1 - 3 parts of defoamer, 1 - 3 parts of bactericidal and mildew-proof agent, 2 - 4 parts of film-forming aid, 2 - 5 parts of rheological modifier, 2 - 5 parts of propylene glycol, 30 - 50 parts of solvent; Among them, the raw materials of the acrylate-silicone copolymer emulsion include 60 - 70 parts by weight of acrylate monomers, 5 - 15 parts by weight of silicone monomers, 3 - 8 parts by weight of hydroxyethyl acrylate, 2 - 5 parts by weight of emulsifier and 0.3 - 1.0 part by weight of initiator, and are prepared by free radical polymerization reaction. The silicone monomer is introduced into the copolymer chain segment through a silicon-oxygen bond, the glass transition temperature is controlled at -20°C to -10°C, and the molecular weight dispersity is 1.5 - 2.0.

[0007] The present invention introduces a silicon-oxygen bond through free radical polymerization, and its low glass transition temperature Tg = -20°C to -10°C enables the molecular chain segments to maintain flexibility at low temperatures and offsets the rigid embrittlement of the polyurethane resin. The low cohesive energy density of the silicon-oxygen bond can effectively reduce the intermolecular force and prevent the coating from cracking due to chain segment freezing below -30°C. In addition, the high hydrolysis activation energy of the silicon-oxygen bond forms a hydrophobic barrier to delay the penetration of acid and alkali; the hydroxyl group provided by hydroxyethyl acrylate crosslinks with the polyurethane prepolymer to enhance the overall stability of the coating. The present invention combines low-temperature toughness and chemical resistance for the first time through the copolymerization of silicon-oxygen bond and acrylate, and solves the problem that a single silicone emulsion in the prior art has insufficient acid-alkali resistance although it has low-temperature resistance.

[0008] The raw materials of the polyurethane-modified acrylate resin in the present invention include 60 - 70 parts by weight of non-hydroxy acrylate monomers, 10 - 20 parts by weight of hydroxy acrylate monomers, 30 - 40 parts by weight of diisocyanate and 10 - 20 parts by weight of diol, and are prepared by addition polymerization reaction. The molar ratio of isocyanate group to hydroxyl group is 1.2 - 1.5:1, the glass transition temperature is controlled at 10°C to 20°C, and the molecular weight dispersity is 1.5 - 2.0.

[0009] The present invention forms urethane bonds through addition polymerization, and its glass transition temperature Tg = 10°C to 20°C serves as the rigid phase, forming a "rigid-flexible interpenetrating network" with the flexible silicone emulsion. At low temperatures, it restricts excessive deformation of the flexible phase and maintains the stability of the coating structure. Meanwhile, the cross-linked network of urethane bonds physically blocks the penetration of acid and base molecules, and the polar groups enhance the interfacial binding force with pigments and fillers, improving the coating adhesion.

[0010] In the coating of the present invention, a "rigid-flexible interpenetrating network" is formed by compounding the acrylate-silicone copolymer emulsion of the flexible phase with the polyurethane-modified acrylate resin of the rigid phase. At low temperatures, the flexible phase absorbs stress, and at normal temperatures, the rigid phase provides support, achieving a balance between no cracking at -30°C and acid and alkali erosion resistance. In addition, titanium dioxide in the pigments and fillers reflects ultraviolet rays to inhibit photoaging, heavy calcium carbonate fills pores, and zinc oxide enhances the interfacial binding force, jointly constructing a physical barrier layer to delay the penetration of acid and alkali.

[0011] In some feasible embodiments, the dispersant is a compound of an anionic dispersant and a non-ionic dispersant, and the weight ratio of the two is 1:(1 - 2); wherein the anionic dispersant is selected from one or more of sodium polyacrylate, alkyl naphthalene sulfonates, and lignin sulfonates, and the non-ionic dispersant is selected from one or more of octylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, and polyoxyethylene ether. The compound of the anionic dispersant and the non-ionic dispersant, through the synergistic effect of electrostatic repulsion and steric hindrance, makes the dispersion fineness of pigments and fillers such as titanium dioxide < 45μm, avoiding coating defects caused by agglomeration.

[0012] In some feasible embodiments, the defoamer is a compound of a silicone defoamer and a mineral oil defoamer, and the weight ratio of the two is (5 - 7):(3 - 5); wherein the silicone defoamer is selected from one or more of polydimethylsiloxane emulsion, polyether-modified silicone oil, and self-emulsifying silicone defoamer; the mineral oil defoamer is selected from one or more of white oil, paraffin oil, and their emulsion-type defoamers compounded with surfactants. In the present invention, the silicone defoamer can achieve rapid defoaming, and the mineral oil defoamer can effectively inhibit foam regeneration without shrinkage defects.

[0013] 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 non-ionic polyurethane associative thickeners, hydrophobically modified alkali-swellable thickeners, and hydrophobically modified cellulose ethers; the cellulose ether thickeners are selected from one or more of hydroxyethyl cellulose, hydroxypropyl methyl cellulose, and ethyl hydroxyethyl cellulose.

[0014] In the present invention, the associative thickener forms a dynamic network by associating hydrophobic groups with latex particles. Shearing force destroys the network and reduces the viscosity, and the network is rebuilt after the shearing is removed. The cellulose ethers form a three-dimensional network structure through hydrogen bonds of hydroxyl groups, which increases the viscosity under static conditions, prevents the pigment and filler from settling, and achieves an ideal rheological curve of high shear and low viscosity and low shear and high viscosity, suitable for multiple scenarios such as brushing / spraying.

[0015] In some feasible ways, the weight ratio of the components targeting bacteria and molds 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 molds is selected from one of pyridines and azoles.

[0016] On the second aspect, the present invention also provides a preparation method of a low-temperature resistant and acid-base resistant roofing waterproof coating, including the following steps: (1) Pre-dispersion: Add deionized water to the reaction kettle. During stirring, add part of the rheological modifier. After it is dissolved, add the organic alcohol amine ether compound and continue stirring; (2) Auxiliary agent dispersion: During stirring, sequentially add the dispersant, part of the defoamer, and the bactericidal and mildew-proof agent into the reaction kettle and stir evenly; (3) Pigment and filler dispersion: During stirring, add titanium dioxide, heavy calcium carbonate, and zinc oxide, and continue stirring until the fineness of the coating is detected to be below 45μm; (4) Emulsion and functional auxiliary agent compounding: First, fully mix the acrylate-silicone copolymer emulsion and the polyurethane-modified acrylate resin evenly, and then add the mixed material into the reaction kettle in step (3). During stirring, sequentially add the film-forming auxiliary agent, propylene glycol, the remaining rheological modifier, and the defoamer, and continue stirring; (5) Performance regulation: Control the viscosity of the coating at 105 ± 3 KU, adjust by adding deionized water or rheological modifier, and finally filter and discharge.

[0017] Among them, in the acrylate-silicone copolymer emulsion, the silicon-oxygen bond of the silicone monomer breaks under the action of the initiator to form free radicals, and copolymerizes with the carbon-carbon double bonds of the acrylate monomers and hydroxyethyl acrylate to form a copolymer chain segment containing a silicon-oxygen bond; in the polyurethane-modified acrylate resin, the isocyanate group in the polyurethane prepolymer reacts with the hydroxyl group in the acrylate resin to generate a urethane bond.

[0018] In some feasible ways, after adding the rheological modifier in step (1), stir at a low speed of 300 - 500 r / min until it is completely dissolved, then add the organic alcohol amine ether compound and continue stirring for 10 - 15 min.

[0019] In some feasible ways, after raising the rotational speed to 900 r / min in step (2), a dispersant, an antifoaming agent, and a bactericidal and mildew-proof agent are added in sequence, and stirred for 20 - 30 min until uniform.

[0020] In some feasible ways, 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 rotational speed is increased to 1600 - 1800 r / min, and dispersed for 30 - 40 min. The temperature inside the kettle is controlled at 25 - 35 °C by a temperature sensor, and the fineness is detected to be below 45 μm.

[0021] In the present invention, low-speed stirring is used to avoid the breakage of the molecular chain of hydroxyethyl cellulose, and high-speed dispersion is used to break the agglomerates of pigments and fillers to a fineness < 45 μm, forming a closely packed structure.

[0022] In some feasible ways, in step (4), an independent reaction vessel is used. First, the stirring speed is set to 100 - 150 r / min, ethyl acetate accounting for 30% - 40% of the total amount of solvents in the coating formulation is added as a solvent, and an acrylate-silicone copolymer emulsion is slowly added, and continuously stirred for 15 - 20 minutes to ensure that the emulsion is fully dispersed in the solvent; Then, a polyurethane-modified acrylate resin is slowly added dropwise at a rate of 5 - 10 mL / min, and the dropping process lasts for 30 - 45 minutes. During the dropping, the stirring speed is increased to 200 - 250 r / min to ensure full mixing of the two; After the dropping is completed, the stirring speed is maintained at 150 - 200 r / min, and stirring is continued for 60 - 90 minutes to further uniformly disperse the two substances; After the above two resins are fully mixed and uniform, the mixed material is transferred to the reaction kettle used in steps (1) - (3). Then, at a stirring speed of 150 - 200 r / min, a film-forming aid, propylene glycol, a rheology modifier, and the remaining antifoaming agent are added in sequence, and stirring is continued for 15 - 20 min.

[0023] In some feasible ways, at the initial stage of the reaction in step (4), the temperature inside the reaction kettle is controlled at 30 - 35 °C and maintained for 30 - 45 minutes to avoid premature side reactions of the raw materials; 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-silicone copolymer emulsion and the polyurethane-modified acrylate resin; Finally, raise the temperature to 60 - 65°C and maintain it for 60 - 90 minutes to ensure complete reaction. The reaction time is controlled within 240 - 360 minutes. During the reaction process, samples are taken every 30 - 60 minutes to check for layering and precipitation. After the reaction, let the sample stand for 24 - 48 hours, observe the layering situation again, and detect the performance indicators of the paint's viscosity and solid content. The viscosity is 105 ± 3 KU, and the solid content is 50% - 70%.

[0024] In the present invention, segmented temperature control is adopted to match the reaction activities of different chemical bonds. First, low temperature is used to initiate silane copolymerization to avoid hydrolysis, then medium temperature is used to promote the formation of urethane bonds, and finally high temperature is used to complete the condensation of silicon - oxygen bonds to ensure molecular - level mixing of the biphasic resin.

[0025] In some feasible ways, in step (5), the pH value is adjusted to 7.5 - 8.5 by adding dilute acid or dilute alkali.

[0026] In some feasible ways, the preparation method of the acrylate - organosilicon copolymer emulsion includes the following steps: (1) Mix 60 - 70 parts by weight of acrylate monomers, 5 - 15 parts by weight of organosilicon monomers, 3 - 8 parts by weight of hydroxyethyl acrylate, 2 - 5 parts by weight of emulsifier with 50 - 75 parts by weight of deionized water, and pre - emulsify for 30 - 60 minutes at a stirring speed of 300 - 500 rpm to obtain a pre - emulsion. The pre - emulsification process disperses the monomers into nanoscale micro - droplets, and the emulsifier stabilizes the latex particles through electrostatic repulsion and steric hindrance to avoid agglomeration.

[0027] (2) Dissolve 0.3 - 1.0 part by weight of initiator in 50 - 75 parts by weight of deionized water to obtain an initiator solution; (3) Add 1 / 3 volume of the pre - emulsion and 0.1 - 0.5 part by weight of buffer to the reaction kettle, raise the temperature to 70 - 75°C, drop - wise add 1 / 3 volume of the initiator solution, and keep the reaction for 30 minutes; then synchronously drop - wise add the remaining pre - emulsion and the remaining initiator solution within 2 - 3 hours, control the reaction temperature at 75 - 85°C; after the drop - wise addition, raise the temperature to 85 - 90°C and keep the reaction for 1 - 2 hours to obtain an acrylate - organosilicon copolymer emulsion with a weight - average molecular weight of 30000 - 50000. Three - stage temperature control is adopted to match the hydrolysis and polymerization reaction kinetics of silicon - oxygen bonds and avoid gel defects caused by early cross - linking.

[0028] The present invention adopts a segmented polymerization method. In the low - temperature initiation (70 - 75°C) stage, 1 / 3 of the pre - emulsion reacts with the buffer to form a seed emulsion; in the medium - temperature drop - wise addition (75 - 85°C) stage, the remaining pre - emulsion and the initiator are synchronously drop - wise added to control the free - radical polymerization rate; in the high - temperature holding (85 - 90°C) stage, the condensation of silicon - oxygen bonds is promoted to ensure complete cross - linking.

[0029] In some feasible embodiments, the preparation method of the polyurethane-modified acrylate resin comprises the following steps: (1) Prepare a hydroxyl-containing acrylate resin: Mix 60-70 parts by weight of non-hydroxyl acrylate monomers, 10-20 parts by weight of hydroxyl acrylate monomers, 80-100 parts by weight of anhydrous solvent and 0.5-1.5 parts by weight of initiator, heat up to 80-90 °C, and dropwise add the remaining monomers and initiator solution within 3-4 hours, and keep the temperature for reaction to obtain a base resin with a hydroxyl content of 2-5% and a weight-average molecular weight of 10,000-20,000. The non-hydroxyl acrylate monomers include at least one of methyl methacrylate and butyl acrylate, and the hydroxyl acrylate monomer is 2-hydroxyethyl acrylate; (2) Prepare a polyurethane prepolymer: Under nitrogen protection, add 30-40 parts by weight of diisocyanate and 10-20 parts by weight of diol to a reaction kettle, heat up to 60-70 °C, and 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, and 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.

[0030] The acrylate-silicone copolymer emulsion forms stable micro-droplets through pre-emulsification, and the copolymerization rate is controlled by segmented dropping to avoid gelation; the polyurethane-modified resin regulates the crosslinking density by controlling the -NCO / -OH molar ratio in the range of 1.2-1.5:1, taking into account flexibility and rigidity. Among them, during free radical polymerization, the silicon-oxygen bond breaks to form free radicals, which copolymerize with the acrylate double bond to form a random copolymer, and the glass transition temperature is determined by the monomer ratio; during the addition polymerization process, the isocyanate group reacts with the hydroxyl group to form a urethane bond, and nitrogen protection prevents water from reacting with NCO to form CO2 bubbles.

[0031] The present invention realizes the construction of a network structure with both rigidity and flexibility through the use of an acrylate-silicone copolymer emulsion (flexible phase) and a polyurethane-modified acrylate resin (rigid phase). Among them, the silicone chain segment with a low glass transition temperature endows the coating with flexibility and elasticity at low temperatures, and the molecular chain segments can still move at low temperatures, effectively dispersing the temperature stress and avoiding cracking. The silicon-oxygen bond of the silicone monomer improves the weather resistance and hydrophobicity, reducing the damage to the coating caused by water penetration. The urethane bond structure with a high glass transition temperature forms a rigid crosslinked network, improving the hardness, wear resistance and acid and alkali corrosion resistance of the coating. The polar groups of the polyurethane enhance the interfacial binding force with the pigment and filler, improving the coating adhesion and structural stability.

[0032] The two form an interpenetrating network through physical blending and chemical cross-linking, combining the low-temperature toughness of the flexible phase and the chemical resistance of the rigid phase. In a low-temperature environment, the flexibility of the silicone chain segments offsets the rigid embrittlement of the polyurethane resin, preventing the coating from cracking; in an acidic or alkaline environment, the urethane bonds of the polyurethane and the siloxane bonds of the silicone cooperate to resist chemical erosion and reduce the breakage of molecular chains.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Through the compounding of acrylate-silicone copolymer emulsion and polyurethane-modified acrylate resin, the present invention forms a "rigid-flexible" structure. At low temperatures, the silicone chain segments endow the coating with flexibility, and the molecular chain segments can move, effectively dispersing stress, enabling the prepared coating to remain uncracked for 24 hours at -30°C. In contrast, Comparative Example 1 containing only a flexible emulsion has slight cracking, Comparative Example 2 containing only a rigid resin has obvious cracking, and Comparative Example 3 with a common acrylic emulsion has severe cracking. The present invention significantly improves the low-temperature resistance of the coating.

[0034] 2. The present invention improves the weather resistance and hydrophobicity through the siloxane bonds of the silicone chain segments, and the urethane bonds of the polyurethane-modified acrylate resin form a rigid cross-linked network, and the two cooperate to resist acid and alkali erosion. After the coating of the example is immersed in a 5% hydrochloric acid solution and a 5% sodium hydroxide solution for 7 days, the color changes slightly, there is no foaming or peeling phenomenon, and the adhesion is grade 0; Comparative Example 1 lacks the protection of the rigid resin and has limited acid and alkali resistance; Comparative Example 2 is alkali-resistant but lacks the weather resistance of silicone; Comparative Example 3 has no special modification, and the coating fails quickly under acid and alkali, indicating that the coating of the present invention has outstanding acid and alkali resistance and can adapt to harsh chemical environments.

[0035] 3. By compounding two resins to form a cross-linked network, the present invention enhances the hardness and wear resistance of the coating. The hardness of Examples 1-3 can reach 2H-3H, with good wear resistance, a wear amount ≤ 0.15 g / 10 min, and slight surface scratches; Comparative Example 1 lacks the rigid resin, with a hardness of only HB and poor wear resistance; Comparative Example 2 has high hardness but poor flexibility, with edge cracking during wear; Comparative Example 3 has a low film-forming strength with a common emulsion and the worst wear resistance. Thus, the present invention has obvious advantages in terms of hardness and wear resistance and can effectively protect the roof. Description of the Drawings

[0036] Figure 1 It is a process flow diagram of a preparation method of a low-temperature and acid-alkali resistant roof waterproof coating provided by the present invention. Detailed Embodiments

[0037] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0038] Embodiment 1: The embodiment of the present invention provides a low-temperature resistant and acid-alkali resistant roofing waterproof coating, including raw material components in parts by weight: 15 parts of acrylate-silicone copolymer emulsion, 5 parts of polyurethane-modified acrylate resin, 5 parts of titanium dioxide, 8 parts of heavy calcium carbonate, 2 parts of zinc oxide, 2 parts of organic alcohol amine ether compound, 3 parts of dispersant, 1 part of defoamer, 1 part of bactericidal and mildew-proof agent, 2 parts of film-forming aid, 2 parts of rheological modifier, 0.5 part of hydroxyethyl cellulose, 2 parts of propylene glycol, and 30 parts of deionized water. Among them, the dispersant includes 1 part of anionic dispersant sodium polyacrylate and 2 parts of non-ionic dispersant octylphenol polyoxyethylene ether; the defoamer includes 0.5 part of polydimethylsiloxane emulsion and 0.5 part of white oil compounded emulsion; the bactericidal and mildew-proof agent includes 0.4 part of quaternary ammonium salt mildew-proof agent and 0.6 part of pyridine mildew-proof agent; the rheological modifier includes 1 part of non-ionic polyurethane associative thickener and 1 part of hydroxyethyl cellulose.

[0039] In this embodiment, the preparation method of the acrylate-silicone copolymer emulsion includes the following steps: (1) Pre-emulsification: Mix 60 parts of methyl methacrylate, 4 parts of ethyl acrylate, 5 parts of vinyltrimethoxysilane, 3 parts of hydroxyethyl acrylate, 2 parts of sodium dodecyl sulfate with 50 parts of deionized water, and stir at 300 rpm for 60 minutes to obtain a pre-emulsion with a particle size of 85 nm.

[0040] (2) Segmented polymerization: Seed stage: Add 1 / 3 of the pre-emulsion and 0.1 part of sodium bicarbonate to the reaction kettle, heat up to 70 °C, and dropwise add 1 / 3 volume of 0.3 part of ammonium persulfate aqueous solution, and keep the reaction at a constant temperature for 30 minutes.

[0041] Dropwise addition stage: Synchronously dropwise add the remaining pre-emulsion and initiator solution within 2 hours, control the temperature at 75 °C, after dropping, heat up to 85 °C, and keep the temperature for 1 hour to obtain a copolymer emulsion with a weight average molecular weight of 30,000, a glass transition temperature of -20 °C, a molecular weight dispersity of 1.5, the glass transition temperature measured by differential scanning calorimetry (DSC) is -20 °C, and the silicon-oxygen bond content detected by infrared spectroscopy is 6%.

[0042] In this embodiment, the preparation method of the polyurethane-modified acrylate resin includes the following steps: (1)Synthesis of hydroxyl resin: 60 parts of methyl methacrylate, 10 parts of 2-hydroxyethyl acrylate, 80 parts of ethyl acetate and 0.5 part 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.

[0043] (2)Preparation of prepolymer: Under nitrogen protection, 30 parts of toluene diisocyanate and 10 parts of polyethylene glycol (molecular weight 400) were added to a reaction kettle and stirred at 60 °C for 1 hour to obtain a prepolymer with an isocyanate group content of 3.5%.

[0044] (3)Modification reaction: The base resin and the 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 reaction was carried out at 60 °C for 2 hours to obtain a modified resin with a weight-average molecular weight of 25,000, a molecular weight dispersity of 1.5, and a glass transition temperature of 10 °C measured by differential scanning calorimetry.

[0045] The preparation method of the coating in this example includes the following steps: (1)Predispersion: 30 parts of deionized water were added to a reaction kettle, stirred at a low speed of 300 r / min, and 0.5 part of a rheological modifier was slowly added and continuously stirred until completely dissolved to form a uniform colloidal solution, and the solution showed a certain viscosity at this time. Then 2 parts of triethanolamine were added and stirred for another 10 minutes to further enhance the dispersion performance of the system, so that the organic alcohol amine ether compounds were uniformly dispersed in the solution, providing a stable dispersion environment for the subsequent addition of raw materials.

[0046] (2)Dispersion of additives: The rotation speed was increased to 900 rpm, and a dispersant, 0.4 part of an antifoaming agent, and a bactericidal and mildew-proof agent were added in sequence and stirred for 20 minutes until uniform. The higher stirring speed enables the dispersant to quickly adsorb on the surface of the pigment and filler, reducing its surface tension and promoting dispersion; the antifoaming agent timely eliminates the bubbles generated during stirring, avoiding the adverse effects of bubbles on subsequent dispersion and reaction; the bactericidal and mildew-proof agent is uniformly dispersed in the system, providing preliminary antibacterial and mildew-proof protection for the coating. Stir continuously for 20 min to ensure that each additive is fully mixed and uniform.

[0047] (3)Dispersion of pigment and filler: First, stir at a low speed of 300 r / min for 15 min to make 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 rotation speed to 1600 r / min. Under high-speed stirring, the pigment and filler particles are continuously refined and uniformly dispersed in the coating system. The fineness is detected to be below 45 μm to ensure that the dispersion effect of the pigment and filler meets the requirements and ensure that the smoothness and performance of the coating are not affected by large particles.

[0048] (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 a reaction kettle, add 2 parts of propylene glycol, the remaining 1.5 parts of rheological modifier and the remaining 0.6 parts of defoamer, stir for 15 minutes, and filter and discharge.

[0049] During the reaction process, strictly control the temperature and time. At the initial stage of the reaction, control the temperature in the reaction kettle at 30 °C and maintain it for 30 minutes to avoid premature side reactions of the raw materials. Then slowly raise the temperature to 50 °C at a rate of 1 °C / min and react at this temperature for 120 minutes to promote the full chemical reaction between the acrylate-silicone copolymer emulsion and the polyurethane-modified acrylate resin, so that the molecular chains of the two resins are intertwined and reacted to form a stable structure. Finally, raise the temperature to 60 °C and maintain it for 60 minutes to ensure complete reaction. During the reaction process, take samples every 30 minutes and check for layering and precipitation by observing the appearance of the samples; after the reaction is completed, let the samples stand for 24 hours, observe the layering situation again, and detect the performance indicators such as the viscosity and solid content of the coating. The measured viscosity is 104 KU and the solid content is 50%.

[0050] (5)Performance regulation: Precisely adjust the coating viscosity to 105 KU by adding a small amount of deionized water to make the coating have good construction consistency and be easy to brush. Add dilute alkali to adjust the pH value to 7.5 to make the coating in a suitable pH range and reduce its own corrosion to the coating. Finally, filter and discharge to remove possible impurities to obtain the finished waterproof coating.

[0051] Example 2: This example is basically the same as Example 1, the difference is that the low-temperature resistant and acid-base resistant roofing waterproof coating of this example includes 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 defoamer, 2 parts of bactericidal and mildew-proof agent, 3 parts of film-forming aid, 3 parts of rheological modifier, 3 parts of propylene glycol, and 40 parts of deionized water. Among them, the dispersant includes 1.3 parts of anionic dispersant alkylnaphthalene sulfonate and 2.7 parts of non-ionic 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 mildew-proof agent includes 0.8 parts of isothiazolinone mildew-proof agent and 1.2 parts of azole mildew-proof agent; the rheological modifier includes 1.4 parts of non-ionic polyurethane associative thickener and 1.6 parts of hydroxypropyl methyl cellulose.

[0052] The preparation method of the acrylate-silicone copolymer emulsion in this example includes the following steps: (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 with 60 parts of deionized water, and stir at 400 rpm for 45 minutes to obtain a pre-emulsion.

[0053] (2)Staged polymerization: Seed stage: Add 1 / 3 of the pre-emulsion and 0.2 parts of sodium bicarbonate to the reaction kettle, heat up to 72 °C, dropwise add an aqueous solution of 0.6 parts of ammonium persulfate with a volume of 1 / 3, and keep the temperature for reaction for 30 minutes.

[0054] Dropwise addition stage: Synchronously dropwise add the remaining pre-emulsion and the initiator solution within 2.5 hours, control the temperature at 80 °C, after dropping, heat up to 88 °C, and keep the temperature for 1.5 hours to obtain a copolymer emulsion with a weight average molecular weight of 40000, a glass transition temperature of -15 °C, and a molecular weight dispersity of 1.7.

[0055] The preparation method of the polyurethane-modified acrylate resin in this example includes the following steps: (1)Hydroxy resin synthesis: Mix 65 parts of butyl acrylate, 15 parts of hydroxyethyl acrylate, 90 parts of ethyl acetate with 1 part of initiator, and react at 85 °C for 3.5 hours to obtain a base resin with a hydroxy content of 3.5% and a weight average molecular weight of 15000.

[0056] (2)Prepolymer preparation: Under nitrogen protection, add 35 parts of isophorone diisocyanate and 15 parts of polyethylene glycol (molecular weight 600) to the reaction kettle, stir at 65 °C for 1.5 hours to obtain a prepolymer.

[0057] (3)Modification reaction: Mix the base resin and the prepolymer according to a molar ratio of isocyanate group to hydroxy group of 1.3:1, add 0.2 parts of catalyst, and react at 70 °C for 2.5 hours to obtain a modified resin with a weight average molecular weight of 35000 and a glass transition temperature of 15 °C, and a molecular weight dispersity of 1.7.

[0058] The preparation method of the polyurethane-modified acrylate resin in this example includes the following steps: (1)Pre-dispersion: Add deionized water to the reaction kettle, add 1 part of rheological modifier under stirring at 300 rpm, after dissolution, add diethanolamine, and stir for 12 minutes.

[0059] (2)Auxiliary agent dispersion: Raise the rotation speed to 900 rpm, sequentially add a dispersant, 1.2 parts of defoamer, and bactericidal and mildew-proof agent in proportion, and stir for 25 minutes.

[0060] (3) Pigment and filler dispersion: Add titanium dioxide, calcium carbonate, and zinc oxide in proportion. After stirring at low speed for 18 minutes, disperse at high speed (1700 rpm) for 35 minutes, and detect the fineness to 40 μm.

[0061] (4) Resin compounding: Mix 20 parts of copolymer emulsion and 10 parts of modified resin at 120 rpm for 20 minutes, transfer to a reaction kettle, add 3 parts of propylene glycol, the remaining rheological modifier and defoamer, stir for 18 minutes, and filter and discharge.

[0062] (5) Performance regulation: According to the test results, fine-tune the coating viscosity to 105 KU by adding an appropriate amount of rheological modifier, and adjust the pH value to 8.0 by adding dilute acid to make the coating performance reach the best. Finally, filter and discharge to obtain a waterproof coating with excellent performance.

[0063] Example 3: This example is basically the same as Example 1, except that the low-temperature resistant and acid-alkali resistant roof waterproof coating in this example includes the following raw material components in parts by weight: 25 parts of acrylate-silicone copolymer emulsion, 15 parts of polyurethane-modified acrylate resin, 10 parts of titanium dioxide, 15 parts of heavy calcium carbonate, 5 parts of zinc oxide, 5 parts of organic alkanolamine ether compound, 6 parts of dispersant, 3 parts of defoamer, 3 parts of bactericidal and mildew-proof agent, 4 parts of film-forming aid, 5 parts of rheological modifier, 5 parts of propylene glycol, and 50 parts of deionized water. Among them, the dispersant includes 2 parts of anionic dispersant alkylnaphthalenesulfonate and 4 parts of non-ionic dispersant fatty alcohol polyoxyethylene ether; the defoamer includes a compound emulsion of 2 parts of polyether-modified silicone oil and 1 part of paraffin oil; the bactericidal and mildew-proof agent includes 1.2 parts of isothiazolinone mildew-proof agent and 1.8 parts of azole mildew-proof agent; the rheological modifier includes 2.3 parts of non-ionic polyurethane associative thickener and 2.7 parts of hydroxypropyl methylcellulose.

[0064] The preparation method of the acrylate-silicone copolymer emulsion in this example includes the following steps: (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 dodecyl sulfate and 75 parts of deionized water, and stir at 500 rpm for 30 minutes to obtain a pre-emulsion.

[0065] (2) Stepwise polymerization: Seed stage: Add 1 / 3 of the pre-emulsion and 0.5 part of sodium bicarbonate to the reaction kettle, heat up to 75 °C, dropwise add 1 / 3 volume of 1.0 part of ammonium persulfate aqueous solution, and keep the reaction at a constant temperature for 30 minutes.

[0066] Dropping stage: The remaining pre-emulsion and initiator solution were synchronously dropped within 3 hours, the temperature was controlled at 85°C, and after dropping, 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.

[0067] The preparation method of the polyurethane-modified acrylate resin in this example includes the following steps: (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.

[0068] (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 reaction kettle and stirred at 70°C for 2 hours to obtain a prepolymer.

[0069] (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 part of catalyst was added, and the reaction was carried out 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.

[0070] The preparation method of the coating in this example includes the following steps: (1) Pre-dispersion: 50 parts of deionized water were added to the reaction kettle, 1.5 parts of rheological modifier were added under stirring at 500 rpm, and after dissolution, 5 parts of organic alcohol amine ether compound were added and stirred for 15 minutes.

[0071] (2) Auxiliary agent dispersion: The rotation speed was increased to 900 rpm, 6 parts of dispersant, 1.5 parts of defoamer and 1.5 parts of bactericidal and mildew-proof agent were added in sequence and stirred for 30 minutes.

[0072] (3) Pigment and filler dispersion: 10 parts of titanium dioxide, 15 parts of calcium carbonate and 5 parts of zinc oxide were added, stirred at low speed for 20 minutes, and then dispersed at high speed (1800 rpm) for 40 minutes, and the fineness was detected to 35 μm.

[0073] (4) Resin compounding: 25 parts of copolymer emulsion and 15 parts of modified resin were mixed at 150 rpm for 25 minutes, transferred to the reaction kettle, 4 parts of propylene glycol, the remaining rheological modifier and defoamer were added, stirred for 20 minutes, and filtered and discharged.

[0074] During the reaction, the temperature was controlled at 35°C in the initial stage of the reaction and maintained for 45 minutes; then it was heated to 55°C at a rate of 2°C / min and reacted for 180 minutes; finally, it was heated to 65°C and maintained for 90 minutes. During the reaction, samples were taken every 60 minutes to check for stratification and precipitation; after the reaction ended, the sample was allowed to stand for 48 hours, the stratification situation was observed again, and the viscosity of the coating was detected to be 106 KU and the solid content was 70%.

[0075] (5)Performance regulation: The viscosity of the coating was adjusted to 105 KU by adding a small amount of deionized water, the pH value was adjusted to 8.5 by adding dilute alkali, and finally it was filtered and discharged to obtain a waterproof coating that meets the performance requirements.

[0076] Comparative Example 1: The difference between Comparative Example 1 and the Example is that only acrylate-silicone copolymer emulsion (flexible phase) was used, and polyurethane-modified acrylate resin (rigid phase) was not added. The preparation method of the coating was basically the same as that of Example 1, and pre-dispersion, additive dispersion, and pigment and filler dispersion were carried out in sequence.

[0077] The difference is that in this comparative example, only acrylate-silicone copolymer emulsion was added in the emulsion and functional additive compounding step, and then film-forming aid, propylene glycol, rheological modifier, and defoamer were added in sequence and stirred and mixed evenly. The viscosity of the coating was controlled at 105 ± 3 KU, the pH value was adjusted to 7.5 - 8.5, and finally it was filtered and discharged.

[0078] Performance prediction: 1. Low-temperature resistance: Because the acrylate-silicone copolymer emulsion itself has a relatively low glass transition temperature, the molecular chain segments still have a certain degree of mobility at low temperatures and can effectively absorb and disperse external stress.

[0079] 2. Acid and alkali resistance: Although the acrylate-silicone copolymer emulsion has a certain degree of water resistance and weather resistance, its acid and alkali resistance is limited under long-term acid and alkali erosion and cannot provide sufficient protection.

[0080] 3. Hardness and abrasion resistance: Due to the lack of polyurethane-modified acrylate resin, no sufficient rigid structure and crosslinking points were formed in the coating, and it could not effectively resist external friction and scratching.

[0081] Comparative Example 2: The difference between Comparative Example 2 and the Example is that only polyurethane-modified acrylate resin (rigid phase) was used, and acrylate-silicone copolymer emulsion (flexible phase) was not added. The preparation method of the coating was basically the same as that of Example 1, and pre-dispersion, additive dispersion, and pigment and filler dispersion were carried out in sequence.

[0082] The difference is that in this comparative example, only polyurethane-modified acrylate resin was added in the emulsion and functional additive compounding step, and other additives were added and stirred evenly, and after the performance regulation was completed, it was filtered and discharged.

[0083] Performance prediction: 1. Low-temperature resistance: Since the glass transition temperature of the polyurethane-modified acrylate resin is relatively high, the molecular chain segments are difficult to move at low temperatures and cannot adapt to the stress generated by temperature changes, resulting in an increase in the brittleness of the coating and easy cracking.

[0084] 2. Acid and alkali resistance: The stability of the urethane bond in the polyurethane-modified acrylate resin can effectively resist the erosion of acid and alkali substances.

[0085] 3. Flexibility: Due to the structural characteristics of the polyurethane-modified acrylate resin itself, while providing hardness and strength, it sacrifices some flexibility.

[0086] Comparative Example 3: The difference between Comparative Example 3 and the Example is that: not only the acrylate-silicone copolymer emulsion is not used, but also the polyurethane-modified acrylate resin is not used, but a common acrylic emulsion is used to completely replace the two core resins, specifically as follows: Raw material preparation: Select a common acrylic emulsion (the weight average molecular weight, glass transition temperature and other parameters are different from those in the Example), weigh 25 parts of this common acrylic emulsion to replace the acrylate-silicone copolymer emulsion and polyurethane-modified acrylate resin in the invention. The manufacturer of the acrylic emulsion: Beijing Huacai Coating Technology Co., Ltd.; production grade: BJ-PA-03.

[0087] The types, dosages and specifications of other raw materials (such as titanium dioxide, heavy calcium carbonate, etc.) are the same as those in Example 1.

[0088] The coating in this comparative example is operated according to the preparation method of the example, including steps such as predispersion, dispersion of additives, dispersion of pigments and fillers, compounding of emulsion and functional additives, and performance regulation.

[0089] Performance prediction: 1. Low-temperature resistance: The glass transition temperature of the common acrylic emulsion is relatively high, and it cannot maintain good flexibility at low temperatures and cannot meet the requirements of low-temperature resistance.

[0090] 2. Acid and alkali resistance: The common acrylic emulsion lacks silicone monomers and polyurethane-modified structures, and its acid and alkali resistance is far inferior to the coating in the invention.

[0091] 3. Comprehensive performance: This coating performs poorly in terms of film-forming performance, hardness, abrasion resistance, etc. After film formation, the strength of the coating film is low and it is easy to be scratched, and it cannot effectively protect the roof.

[0092] In order to compare and test the low-temperature resistance, acid and alkali resistance, hardness and abrasion resistance of the coatings prepared in the above examples and comparative examples, the following test methods are provided: I. Low-temperature resistance performance test: 1. Specimen specifications Base material: Standard cement mortar board (size: 100mm×100mm×10mm, conforming to the standard of GB / T17671-1999).

[0093] Coating thickness: The wet film thickness is controlled to be (200±20)μm, and the dry film thickness after drying is about (100±10)μm (calibrated with a wet film thickness gauge and a dry film thickness gauge).

[0094] 2. Specific test methods Specimen 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.

[0095] Low-temperature treatment: Place the specimen in a low-temperature test chamber (accuracy ±1℃), cool it at a rate of 1℃ / min to -30℃, and maintain it for 24 hours. Place silica gel desiccant in the test chamber to avoid the influence of condensed water on the coating.

[0096] Observation and evaluation: Take out the specimen, place it at room temperature for 2 hours, and observe the coating surface with a 5-fold magnifying glass.

[0097] Judgment criteria: Excellent: No cracking, no peeling; Good: 1-2 fine lines (length ≤5mm); Poor: More than 3 cracks or peeling area >5%.

[0098] II. Acid and alkali resistance test: 1. Specimen specifications Base material: Q235 carbon steel plate (size: 150mm×70mm×2mm, surface sandblasted).

[0099] Coating thickness: Dry film thickness (200±20)μm (measured with a magnetic thickness gauge).

[0100] 2. Specific test methods Specimen preparation: Apply the coating evenly on the surface of the steel plate, cure it at room temperature for 7 days, and seal the edge of the specimen with paraffin after drying (leaving a 50mm×50mm test area).

[0101] Immersion test: Acid solution: 5% hydrochloric acid solution, the solution volume submerges the specimen test area ≥20mm.

[0102] Alkali solution: 5% sodium hydroxide solution, the solution volume is the same as that of the acid solution.

[0103] Immerse the two groups of specimens in acid and alkali solutions respectively, and immerse them for 7 days under the constant temperature condition of 23±2℃ without changing the solution during the period.

[0104] Performance evaluation: Appearance inspection: Take out the test piece, rinse it with clean water and dry it, then observe the color change of the coating (ΔE value measured by a color difference meter), blistering (bubble diameter and density), and peeling area.

[0105] Adhesion test: Conduct the cross-cut test in accordance with GB / T9286-1998 "Determination of adhesion of paints and varnishes by cross-cut test", using a cutter with a 1mm spacing. Rating criteria: Grade 0: The cutting edge is completely smooth and there is no coating peeling. Grade 1: There is a little coating peeling at the cutting intersections, and the area ≤ 5%. Grade 4: The coating peels off in a large area, and the area > 65%.

[0106] Hardness test (pencil hardness method) 1. Specimen specifications Substrate: 3mm thick transparent organic glass plate (size: 100mm × 100mm).

[0107] Coating thickness: Dry film thickness (80 ± 10) μm (measured by an eddy current thickness gauge).

[0108] 2. Specific test method Sample preparation: Apply the coating evenly on the surface of the organic glass plate and cure it at room temperature for 7 days.

[0109] Test steps: In accordance with GB / T6739-2006 "Determination of film hardness of paints and varnishes by pencil method", use Zhonghua brand high-grade drawing pencils (hardness grades from 6B to 6H).

[0110] The pencil makes a 45° angle with the coating surface, applies a pressure of about 1kg, and advances at a speed of 1mm / s. Each hardness grade is tested 3 times.

[0111] Judgment criteria: Take the highest pencil hardness grade without scratches in the 3 tests as the coating hardness value (for example, if the 3H pencil has no scratches and the 4H has scratches, the hardness is 3H).

[0112] IV. Abrasion resistance test (falling sand method) 1. Specimen specifications Substrate: 5mm thick concrete slab (size: 150mm × 150mm, surface ground).

[0113] Coating thickness: Dry film thickness (300 ± 30) μm (measured by an ultrasonic thickness gauge).

[0114] 2. Specific test method Sample preparation: The coating was evenly brushed on the surface of the concrete slab and cured at room temperature for 14 days.

[0115] Testing device: Abrasion tester with falling sand (complies with ASTM D968 standard), the sand grains are 20 - 30 mesh quartz sand, the falling sand height is 500 mm, and the sand flow rate is controlled at 200 g / min.

[0116] Testing procedure: Fix the specimen horizontally under the instrument, turn on the falling sand device, and continuously abrade for 10 minutes.

[0117] Collect the abraded sand grains and coating debris, weigh the mass of the specimen before and after abrasion with an analytical balance, and calculate the abrasion loss (g / 10 min).

[0118] Judgment criteria: An abrasion loss ≤ 0.15 g / 10 min is excellent, 0.15 - 0.3 g / 10 min is good, and > 0.3 g / 10 min is poor.

[0119] Note: All tests need to be carried out in a standard laboratory environment (temperature 23 ± 2 °C, relative humidity 50 ± 5%) to avoid interference of environmental factors on the results.

[0120] The following are the experimental data of the performance comparison test between the examples and the comparative examples: I. Experimental data of low-temperature resistance performance

[0121] II. Experimental data of acid and alkali resistance performance

[0122] III. Experimental data of hardness and wear resistance

[0123] Combined with the above experimental data, the performance analysis of the coatings prepared in the examples and the comparative examples is as follows: Low-temperature resistance performance: In Examples 1 - 3, due to the simultaneous presence of acrylate-silicone copolymer emulsion with a low glass transition temperature and rigid polyurethane-modified acrylate resin, a "rigid-flexible combination" structure is formed, and the molecular chain segments maintain their mobility at low temperatures without cracking.

[0124] In Comparative Example 1, only a flexible emulsion is contained, and the stress dispersion ability at low temperatures is insufficient (slight cracking); in Comparative Example 2, only a rigid resin is contained, and the glass transition temperature is high (10 °C - 20 °C), with significant low-temperature brittleness; in Comparative Example 3, the glass transition temperature of the ordinary acrylic emulsion is even higher, and it cannot adapt to low-temperature deformation.

[0125] Acid and alkali resistance: In the examples, the silicone chain segments and urethane bonds work together to resist acid and alkali erosion, with excellent adhesion; in Comparative Example 1, there is a lack of rigid resin protection, and the molecular chains of the emulsion are easily damaged by acids and alkalis; in Comparative Example 2, due to the good alkali resistance of the polyurethane structure, but the lack of weather resistance of silicone; in Comparative Example 3, there is no special modification, and the coating fails quickly under acids and alkalis.

[0126] Hardness and wear resistance: In the examples, a cross-linked network is formed through resin blending, with excellent hardness (2H - 3H) and wear resistance (wear amount ≤ 0.15 g); in Comparative Example 1, there is a lack of rigid resin, and the hardness is only HB; in Comparative Example 2, although the hardness is high (3H), the poor flexibility leads to edge cracking during wear; in Comparative Example 3, the film-forming strength of the ordinary emulsion is low, and the wear resistance is the worst.

[0127] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be encompassed within the present invention.

Claims

1. A low-temperature resistant, acid and alkali resistant roofing waterproof coating, characterized in that, Comprising raw material components in parts by weight: 15 - 25 parts of acrylate - 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 compounds, 3 - 6 parts of dispersant, 1 - 3 parts of defoamer, 1 - 3 parts of bactericidal and mildew - proof agent, 2 - 4 parts of film - forming aid, 2 - 5 parts of rheological modifier, 2 - 5 parts of propylene glycol, 30 - 50 parts of solvent; The raw materials of the acrylate - silicone copolymer emulsion include 60 - 70 parts by weight of acrylate monomers, 5 - 15 parts by weight of silicone monomers, 3 - 8 parts by weight of hydroxyethyl acrylate, 2 - 5 parts by weight of emulsifier and 0.3 - 1.0 part by weight of initiator, and it is prepared by free - radical polymerization reaction. The silicone monomer is introduced into the copolymer chain segment through a silicon - oxygen bond, the glass transition temperature is controlled at - 20°C to - 10°C, and the molecular weight dispersity is 1.5 - 2.0; The raw materials of the polyurethane - modified acrylate resin include 60 - 70 parts by weight of non - hydroxyl acrylate monomers, 10 - 20 parts by weight of hydroxyl acrylate monomers, 30 - 40 parts by weight of diisocyanate and 10 - 20 parts by weight of diol, and it is prepared by addition polymerization reaction. The molar ratio of isocyanate group to hydroxyl group is 1.2 - 1.5:1, the glass transition temperature is controlled at 10°C to 20°C, and the molecular weight dispersity is 1.5 - 2.

0.

2. The low-temperature resistant and acid-alkali resistant roof waterproof coating according to claim 1, characterized in that: The dispersant is a compound of an anionic dispersant and a non - ionic dispersant, and the weight ratio of the two is 1:(1 - 2); The anionic dispersant is selected from one or more of sodium polyacrylate, alkyl naphthalene sulfonate, and lignin sulfonate, and the non - ionic dispersant is selected from one or more of octylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, and polyoxyethylene ether; 3. The low-temperature resistant and acid-alkali resistant roof waterproof coating according to claim 1, wherein: The defoamer is a compound of a silicone defoamer and a mineral oil defoamer, and the weight ratio of the two is (5 - 7):(3 - 5); The silicone defoamer is selected from one or more of polydimethylsiloxane emulsion, polyether - modified silicone oil, and self - emulsifying silicone defoamer; the mineral oil defoamer is selected from one or more of white oil, paraffin oil, and emulsion - type defoamer prepared by compounding them with surfactants.

4. The low-temperature resistant and acid-alkali resistant roof waterproof coating according to claim 1, characterized in that: The rheological 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 non - ionic polyurethane associative thickener, hydrophobically modified alkali - swellable thickener, and 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, in the bactericidal and mildew - proof agent, the weight ratio of the components against bacteria and molds is 1:(1 - 1.5). The component against bacteria is selected from one of quaternary ammonium salts and isothiazolinones, and the component against molds is selected from one of pyridines and azoles.

5. The preparation method of the low-temperature resistant and acid-alkali resistant roofing waterproof coating according to any one of claims 1-4, characterized in that, Including the following steps: (1) Predispersion: Add deionized water to the reaction kettle. During stirring, add part of the rheological modifier and organic alcohol amine ether compounds in sequence; (2) Auxiliary agent dispersion: successively add a dispersant, a part of defoamer, and a bactericidal and mildew-proof agent to the above mixture, and continuously stir; (3) Pigment and filler dispersion: add titanium dioxide, heavy calcium carbonate, and zinc oxide to the mixture in step (2), and continue to stir; (4) Emulsion and functional auxiliary agent compounding: first fully mix the acrylate-silicone copolymer emulsion and the polyurethane-modified acrylate resin evenly, then transfer the mixed material to the reaction kettle in step (3), and successively add a film-forming auxiliary agent, propylene glycol, the remaining rheological modifier, and defoamer, and continue to stir, and finally filter and discharge; The acrylate-silicone copolymer emulsion uses the silicon-oxygen bond of the silicone monomer to break to form free radicals under the action of an initiator, and copolymerizes with the carbon-carbon double bonds of acrylate monomers and 2-hydroxyethyl acrylate to form a copolymer chain segment containing a silicon-oxygen bond; The polyurethane-modified acrylate resin uses the isocyanate group in the polyurethane prepolymer to react with 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 rheological modifier in step (1), stir at a low speed of 300-500 r / min until it is completely dissolved, then add an organic alkanolamine ether compound, and continue to stir for 10-15 min; And / or, in step (2), after raising the rotation speed to 900 r / min, successively add a dispersant, a defoamer, and a bactericidal and mildew-proof agent, and stir for 20-30 min until it is uniform; And / or, in step (3), stir at a low speed of 300-500 r / min for 15-20 min, then add titanium dioxide, heavy calcium carbonate, and zinc oxide, raise the rotation speed to 1600-1800 r / min, disperse for 30-40 min, and control the temperature in the kettle at 25-35 °C through a temperature sensor, and detect the fineness to below 45 μm.

7. The preparation method according to claim 6, characterized in that: In step (4), first set the stirring speed to 100-150 r / min, add ethyl acetate as a solvent, slowly add the acrylate-silicone copolymer emulsion, and continuously stir for 15-20 minutes; Then slowly drop the polyurethane-modified acrylate resin at a speed of 5-10 mL / min, and the dropping process lasts for 30-45 minutes. During the dropping, raise the stirring speed to 200-250 r / min. After the dropping is completed, maintain the stirring speed at 150-200 r / min and continue to stir for 60-90 minutes; After the above two resins are fully mixed evenly, transfer the mixed material to the reaction kettle used in step (3), successively add a film-forming auxiliary agent, propylene glycol, the remaining rheological modifier, and defoamer, and continue to stir for 15-20 min.

8. The preparation method according to claim 7, characterized in that: In step (4) at the initial stage of the reaction, control the temperature in the reaction kettle at 30-35 °C and maintain it for 30-45 minutes; then raise the temperature to 50-55 °C at a speed of 1-2 °C / min, and react at this temperature for 120-180 minutes; finally, raise the temperature to 60-65 °C and maintain it for 60-90 minutes.

9. The preparation method according to claim 8, characterized in that: The preparation method of the acrylate-silicone copolymer emulsion includes the following steps: (1) Mix 60 - 70 parts by weight of acrylate monomers, 5 - 15 parts by weight of silicone monomers, 3 - 8 parts by weight of hydroxyethyl acrylate, 2 - 5 parts by weight of emulsifier with 50 - 75 parts by weight of deionized water, and pre-emulsify for 30 - 60 minutes at a stirring speed of 300 - 500 rpm to obtain a pre-emulsion. (2) Dissolve 0.3 - 1.0 part by weight of initiator in 50 - 75 parts by weight of deionized water to obtain an initiator solution. (3) Add 1 / 3 volume of the pre-emulsion and 0.1 - 0.5 part by weight of buffer to a reaction kettle, heat up to 70 - 75 °C, dropwise add 1 / 3 volume of the initiator solution, and keep the reaction at a constant temperature for 30 minutes; then simultaneously dropwise add the remaining pre-emulsion and the remaining initiator solution within 2 - 3 hours, controlling the reaction temperature at 75 - 85 °C; after the dropping is completed, heat up to 85 - 90 °C and keep the temperature for 1 - 2 hours to obtain an acrylate-silicone copolymer emulsion with a weight average molecular weight of 30000 - 50000.

10. The preparation method according to any one of claims 5-9, characterized in that: The preparation method of the polyurethane-modified acrylate resin comprises the following steps: (1) Prepare a hydroxyl-containing acrylate resin: Mix 60 - 70 parts by weight of non-hydroxyl acrylate monomers, 10 - 20 parts by weight of hydroxyl acrylate monomers, 80 - 100 parts by weight of anhydrous solvent and 0.5 - 1.5 parts by weight of initiator, heat up to 80 - 90 °C, dropwise add the remaining monomers and the initiator solution within 3 - 4 hours, and keep the reaction at a constant temperature to obtain a base resin with a hydroxyl content of 2 - 5% and a weight average molecular weight of 10000 - 20000. The non-hydroxyl acrylate monomers include at least one of methyl methacrylate and butyl acrylate, and the hydroxyl acrylate monomer is hydroxyethyl acrylate. (2) Prepare a polyurethane prepolymer: Under nitrogen protection, add 30 - 40 parts by weight of diisocyanate and 10 - 20 parts by weight of diol to a reaction kettle, heat up to 60 - 70 °C, and 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 part by weight of catalyst, and react at 60 - 80 °C for 2 - 3 hours to obtain a polyurethane-modified acrylate resin with a weight average molecular weight of 25000 - 45000, and the -NCO / -OH molar ratio of the base resin to the prepolymer is 1.2 - 1.5:1.

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