Weather-resistant, heat-insulating and heat-preserving waterproof coating for outer wall and preparation method thereof

Abstract

The invention discloses a weather-resistant heat-insulation waterproof coating for an outer wall and a preparation method of the weather-resistant heat-insulation waterproof coating. The waterproof coating comprises the following components in parts by weight: 27-35 parts of modified acrylate polymer emulsion, 35-50 parts of composite filler, 5-10 parts of a curing system, 4-8 parts of a coalescing agent, 0.1-0.5 part of a defoaming agent, 0.3-0.8 part of a flatting agent, 0.2-0.6 part of a mildew preventive, 0.5-1.0 part of a thickening agent and 1-5 parts of a pH regulator, the modified acrylate polymer emulsion is prepared by carrying out pretreatment and silanization modification on cardanol and then carrying out monomer pre-emulsification and free radical polymerization. According to the waterproof coating provided by the invention, a Si-O-C network and a hindered amine free radical capture system are introduced, so that the weather resistance is improved; fluoride-nano silicon dioxide is used for constructing a roughness-low surface energy synergistic waterproof interface; acid-washed fly ash floating beads, silicon dioxide aerogel and expanded perlite filler are compounded to form multiple heat conduction scattering paths so as to realize cross-scale porous filler heat preservation; the waterproof coating can serve in complex environments with large temperature difference fluctuation, acid rain and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water-based paint, in particular to a weather-resistant, heat-insulating and waterproof coating for exterior walls and a preparation method thereof. BACKGROUND

[0002] Building exterior wall paint is a paint applied to the entire building exterior wall. Its main functions are decoration and protection of the exterior wall, making the building look neat and beautiful while protecting the building. Compared with interior wall paint, exterior wall paint needs to be exposed to outdoor environments and needs to withstand multiple tests such as ultraviolet radiation, temperature changes, and rain erosion for a long time. However, the existing technology has significant defects in the performance balance of exterior wall paint:

[0003] 1. Insufficient weather resistance: traditional resin modification often uses a single silane coupling agent to achieve weather resistance modification, which can temporarily improve the interfacial adhesion, but lacks a free radical capture mechanism. Under long-term ultraviolet radiation, the coating is prone to oxidative degradation, which is manifested as a decrease in gloss retention (≤80% after 3000h), an increase in color difference (ΔE≥3.2), and even a powdering phenomenon;

[0004] 2. Limited thermal insulation performance: single porous thermal insulation materials such as carbonized red mud and expanded perlite are often used, which have a single pore structure and cannot form an effective thermal conduction barrier path, resulting in low thermal insulation efficiency (thermal conductivity generally ≥0.035 W / (m·K)).

[0005] 3. Defects in waterproof interface: when building a waterproof interface, the conventional hydrophobic layer achieves waterproofing by physically blending fluorides, and there is a lack of coordination between surface energy regulation and roughness design. The water contact angle is usually ≤105°, and swelling occurs after soaking. SUMMARY

[0006] To solve the above technical problems, the present application provides a waterproof coating for exterior walls with weather resistance, thermal insulation, and thermal preservation, and a preparation method thereof.

[0007] The present application provides a waterproof coating for exterior walls with weather resistance, thermal insulation, and thermal preservation, comprising the following components by weight:

[0008] 27-35 parts of modified acrylate polymer emulsion, 35-50 parts of composite filler, 5-10 parts of curing system, 4-8 parts of film-forming aid, 0.1-0.5 parts of defoamer, 0.3-0.8 parts of leveling agent, 0.2-0.6 parts of mildewcide, 0.5-1.0 parts of thickening agent, and 1-5 parts of pH regulator;

[0009] The modified acrylate polymer emulsion is prepared by the following steps:

[0010] a. Cardanol pretreatment and silanization modification: cardanol is pretreated by acid washing, molecular distillation and dehydration, and then modified with piperazine-based silane coupling agent to obtain silanized cardanol; after pretreatment, the hydroxyl value of the cardanol is 180-200 mgKOH / g, and the acid value is ≤2 mgKOH / g;

[0011] b. Monomer pre-emulsification: the mixed monomers containing silanized cardanol are dissolved in butanone-butyl acetate solvent to obtain an oil phase, and then mixed with an aqueous phase containing an emulsifier to form a pre-emulsified liquid by homogenization emulsification; the mixed monomers include silanized cardanol, branched butyl acrylate, methyl methacrylate and hindered amine light stabilizer in a molar ratio of 1:2.5:1-1.5:0.5-1;

[0012] c. Free radical polymerization: the pre-emulsified liquid of step b is added to the reaction kettle twice with initiator to carry out a two-step polymerization process; then an oxidation-reduction system is added to terminate the polymerization to obtain a modified acrylate polymer emulsion;

[0013] The curing system includes bifuran monomer, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylmethyl ester, free radical scavenger and guanidino catalyst; the molar ratio of bifuran monomer to 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylmethyl ester is 1:1.05-1.5;

[0014] The hydroxyl value reflects the content of hydroxyl groups in cardanol and serves as the active site for modification reaction with silane coupling agent; low hydroxyl value will result in insufficient grafting rate, incomplete silane network, and poor weather resistance and water resistance of the coating. The acid value reflects the content of free fatty acids in cardanol; high acid value will lead to unstable pH of the system, inhibit catalyst activity, interfere with silanization reaction and subsequent free radical polymerization, and deteriorate the mechanical properties of the coating.

[0015] Through acid washing (removal of free fatty acids), molecular distillation (removal of phenolic oligomers) and dehydration (reduction of moisture), the hydroxyl active sites of cardanol are more fully exposed, and the silanization reaction is more uniform.

[0016] Alternatively, in step a: the modification process is specifically as follows: the ethanol-water solution of piperazine-based silane coupling agent with pH 4-5 is pre-hydrolyzed at 50-60°C for 30-40 min, and then modified with pretreated cardanol in a water bath at 65-80°C for 2-3 h; the piperazine-based silane coupling agent is γ-piperazine propyl methyl dimethoxy silane.

[0017] The silane is anchored on the cardanol molecule in the form of a covalent bond, ensuring water resistance while retaining the double bonds in the side chains of cardanol.

[0018] Optionally, in step b: the water / oil volume ratio is 3-5:1, the amount of emulsifier in the aqueous phase is 0.5-2.0 wt%; the hindered amine light stabilizer is 2,2,6,6-tetramethyl-4-piperidyl methacrylate;

[0019] The homogenization treatment conditions are: nitrogen atmosphere, 4000-10000 rpm rotation speed for 30 min, control the emulsion D50 = 300 ± 50 nm, and adjust the pH to 7-7.5 with sodium bicarbonate.

[0020] Optionally, in step c: the two-step polymerization process is specifically:

[0021] 1) Under a nitrogen atmosphere, take 70-80 wt% of the pre-emulsion of step b and 50 wt% of the initiator into a reaction kettle, react at 70-78℃ for 1-2h to obtain an oligomer seed;

[0022] 2) Then add the remaining pre-emulsion and initiator, heat to 80-85℃, continue to incubate for 1-1.5h; add 0.4-0.8 wt% of the redox system to terminate the reaction and eliminate residual monomers; after the system cools to room temperature, adjust the pH to 8.0-8.5 with ammonia water for storage;

[0023] The initiator is ammonium persulfate, and the amount is 0.8-1.5 wt% of the total monomer mass; the redox system is t-butyl hydroperoxide and ascorbic acid with a mass ratio of 2:1, the branching degree of branched butyl acrylate is 3-5 branches, and the glass transition temperature is ≤-45℃.

[0024] Optionally, the difuran monomer is one of 2,2'-difuran-5,5'-dimethyl dicarboxylate, difuran malonate, difuran benzoate, and furil.

[0025] The guanidino catalyst is 0.05-0.20 wt% tetramethylguanidine, and the free radical scavenger is 0.5-1.0 wt% diphenyl iodonium salt, based on the mass of the difuran monomer.

[0026] Optionally, the film-forming aid is a mixture of nano-silicon dioxide and fluorine-containing acrylate monomer with a mass ratio of 1:3-5; the particle size of the nano-silicon dioxide is 20-30 nm; the fluorine-containing monomer is a fluorine-containing alkyl methacrylate with 6-10 fluorine atoms in the molecule and a fluorine-containing alkyl carbon chain length of 4-8 carbon atoms, including but not limited to perfluorobutyl methacrylate and octafluoropentyl methacrylate.

[0027] The nano-silica forms a micro-rough surface by physical accumulation, and after being compounded with a low-surface-energy fluorine-containing acrylate, the water contact angle is improved by the synergistic effect of roughness and low surface energy. The fluorine molecule chain segment wraps the nano-silica, and the nano-silica has both hydrophobicity and flexibility. The silicon hydroxyl groups on the surface of the nano-silica can also form hydrogen bonds with the Si-O-C network in the modified acrylate polymer, thereby improving the cohesion of the coating and increasing the tensile strength.

[0028] Optionally, the composite filler is acid-washed fly ash floating beads, silica aerogel and expanded perlite in a mass ratio of 5-7:2-4:1, and is ultrasonically dispersed in a 1.5-2.5 wt% silane coupling agent solution at 50-60 DEG C.

[0029] The preservative is isothiazolinone and zinc pyrithione, the defoaming agent is a polyether defoaming agent, the thickening agent is hydroxyethyl cellulose, the leveling agent is a polyurethane leveling agent, and the pH adjuster is triethanolamine.

[0030] Optionally, the acid-washed fly ash floating beads are prepared by the following steps: ultrasonic treatment of fly ash floating beads with a 1:1 volume ratio of a 5 wt% oxalic acid and 3 wt% hydrochloric acid mixture; after washing to neutral, calcination at 700-800 DEG C for 2h, and ball milling to a D50 of 1-5 μm, a specific surface area of ≥180 m 2 / g.

[0031] The fly ash floating beads are activated and the surface metal oxides are removed by acid treatment, so that the specific surface area can be increased, and the interfacial bonding force with the acrylate and the composite filler can be enhanced.

[0032] Optionally, the silica aerogel has a pore size of 20-50 nm, a porosity of ≥90%, and a specific surface area of ≥800 m 2 / g; and the expanded perlite has a particle size of 30-60 μm.

[0033] The nano-scale pores of the silica aerogel can limit the thermal motion of air molecules, the mesopores of the fly ash floating beads can inhibit convective heat transfer, and the macropores of the expanded perlite can form an air layer to reflect thermal radiation. The three form a three-level scattering system of "nano-pore-mesopore-macropore" to achieve thermal insulation.

[0034] The application also protects a preparation method of the waterproof coating for the exterior wall weather-resistant thermal insulation, which comprises the following steps:

[0035] The modified acrylate polymer emulsion is premixed with the composite filler to obtain a premixed slurry; the curing system is added, and the remaining composite filler is added in 2-3 times during the process; the film-forming aid is added, and ultraviolet curing is performed under microwave assistance;

[0036] The defoaming agent, the leveling agent are added in sequence, and stirring is carried out for 8-12 min; the thickening agent and the preservative are added, and stirring is carried out; the pH adjusting agent is used for adjusting the pH to 7-8, so that the waterproof coating is obtained.

[0037] Optionally, the curing condition is that the reaction temperature is 75-85 DEG C, the reaction time is 1.5-2h, and the interval of adding the residual composite filler is not less than 20 min.

[0038] The ultraviolet curing condition is that the light intensity is 15-40 mW / cm 2 , the wavelength is 365-385 nm, the total curing time is 10-15 min, and the microwave auxiliary power is 200-300 W.

[0039] Beneficial effects:

[0040] The present application realizes the synergistic improvement of the weather resistance, thermal insulation and waterproof performance of the external wall coating through multi-dimensional technical innovation, and the specific embodiments are as follows.

[0041] The weather resistance is greatly improved: the Si-O-C network with ultraviolet shielding effect and the hindered amine radical capture system are constructed to inhibit the oxidative degradation of the coating. After 3000h QUV accelerated aging, the gloss retention is greater than or equal to 95%, the color difference ΔE is less than or equal to 1.2, and the surface is free of differentiation.

[0042] Cross-scale porous thermal insulation: acid-washed fly ash floating beads, silica aerogel and expanded perlite are compounded to form a large pore-mesoporous-nanoporous multiple heat conduction scattering path, and the thermal conductivity coefficient is as low as 0.028 W / (m·K).

[0043] Synergistic waterproof interface construction: the fluoride-nano silica compound forms a roughness-low surface energy hydrophobic interface, and the water contact angle is greater than or equal to 130 DEG; the tensile strength retention rate is greater than or equal to 88% under the environment of pH=2-12, and it can be applied to harsh environments such as large temperature difference fluctuation and acid rain.

[0044] Self-repairing adaptability: the double furan-epoxy curing system gives the coating a self-repairing efficiency of more than 84%, and the Diels-Alder reversible reaction can realize the self-healing of microcracks, and can be suitable for complex external wall substrate spraying. DETAILED DESCRIPTION

[0045] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below.

[0046] In the description of the specification, the description of the terms "one embodiment", "an example", "a specific example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0047] The following is the source of raw materials involved in the embodiments, and the experimental materials not mentioned can be purchased from conventional biochemical reagent companies.

[0048] Cashew phenol, purity 85%, Wuhan Micak Technology Co., Ltd.

[0049] γ-piperazinyl propyl methyl dimethoxy silane, Wuhan Canos Technology Co., Ltd.

[0050] BASF 9026V branched butyl acrylate, branching degree 4-5, Tg=-50 to-48℃;

[0051] Nano-silica, particle size D50=25nm, specific surface area 190m 2 / g, Jining Tangyi Chemical Co., Ltd.

[0052] Fly ash floating bead, 1250 mesh, Xingtai Jiahui Thermal Insulation Material Co., Ltd.

[0053] Expanded perlite, expansion ratio 12, SiO2 content 70wt%, density 80kg / m 3 , ground through 250 mesh sieve.

[0054] Nano-silica aerogel powder, particle size range 0.1-0.5mm, pore size 40nm, specific surface area 850m 2 / g, porosity 93%, Dacheng County Song Zhang Jikang jade thermal insulation material factory.

[0055] TAFIGEL-PUR80 polyurethane leveling agent, pH ~ 7.5, Dongguan Teirun Chemical Material Co., Ltd.;

[0056] SH-237-7 polyether defoamer, Shenzhen Jipeng Silicon Fluorine Material Co., Ltd.

[0057] In the specific embodiments of the present application, the acid pickling process of fly ash floating bead is as follows:

[0058] Take 100 g of fly ash floating beads, add 5 wt% oxalic acid and 3 wt% hydrochloric acid mixed solution (200 mL) with a volume ratio of 1:1, ultrasonic treatment for 30 min under 200 W power, wash with distilled water until neutral, calcine in a muffle furnace at 800°C for 2 h; finally ball mill to D50 = 2.5 μm.

[0059] After the acid washing of fly ash floating beads, the specific surface area is increased from 1.6 m 2 / g to 210 m 2 / g by BET.

[0060] Preparation Example 1

[0061] Preparation of modified acrylate emulsion:

[0062] a. Cardanol pretreatment and silanization reaction:

[0063] Pretreatment: cardanol is ultrasonically acid washed in a 5 wt% citric acid solution at 60°C for 30 min, and the acid solution is removed by separation; after washing to neutral, filtration is performed, and then the cardanol is transferred to a molecular distillation device; under the conditions of a vacuum degree of 0.1 kPa, an evaporation surface temperature of 150°C, and a condensation surface temperature of 80°C, the cardanol fraction is collected, and the monophenol content is measured to be 90%; finally, the cardanol is dehydrated at 110°C for 30 min under nitrogen bubbling protection until the moisture content is ≤0.3 wt% to avoid side reactions of silane hydrolysis.

[0064] Silanization reaction: 0.11 mol of γ-piperazinylpropylmethyldimethoxysilane is dissolved in 150 mL of an ethanol-water (v:v = 4:1) solvent, and the system pH is adjusted to 4.5 with acetic acid, and hydrolysis is performed at 50°C for 30 min until the solution is clear; 0.10 mol of pretreated cardanol is added, and the reaction is performed in a constant temperature water bath at 80°C for 2.5 h at a pH of 4.5; after the reaction is completed, ammonia water is added to neutralize to pH = 7, and silanized cardanol is obtained.

[0065] b. Monomer pre-emulsification: prepare 200 mL of an aqueous phase with 1.2 wt% emulsifier and preheat to 60°C; mix 0.05 mol of silanized cardanol with 0.125 mol of branched butyl acrylate, 0.075 mol of methyl methacrylate, and 0.025 mol of 2,2,6,6-tetramethyl-4-piperidyl isobutyrylate in a mixture of methyl ethyl ketone and butyl acetate (v:v = 1:1) to obtain an oil phase; add the oil phase to the preheated aqueous phase, and then homogenously emulsify under a nitrogen atmosphere at 5000 rpm for 30 min, and control the pH to 7 with sodium bicarbonate to obtain a pre-emulsion; the particle size D50 is measured to be 305 nm;

[0066] c. Free radical polymerization:

[0067] 1) Under nitrogen atmosphere, 80% mass of the pre-emulsion obtained in step b was taken into a reaction kettle with 0.23 g of ammonium persulfate, and reacted at 75 °C for 2 h to obtain an oligomer seed;

[0068] 2) The remaining 20% mass of the pre-emulsion and 0.23 g of ammonium persulfate were added synchronously through a constant pressure dropping funnel, and the temperature was raised to 80 °C. The system was kept at 80 °C for 1 h, and then 0.2 g of tert-butyl hydroperoxide and 0.1 g of ascorbic acid were added to terminate the polymerization. The system was cooled to room temperature, and the pH was adjusted to 8.0 with ammonia water to obtain a modified acrylate polymer emulsion.

[0069] Preparation Example 2

[0070] The difference from Preparation Example 1 is that in step a: the molecular distillation temperature is increased to 200 °C, and the time is extended to 120 min to remove more phenolic hydroxyl groups, and the vacuum degree is maintained at 0.1 kPa.

[0071] Preparation Example 3

[0072] The difference from Preparation Example 1 is that in step a: the concentration of citric acid pickling is reduced to 1 wt%, and the time is shortened to 15 min; and the drying time is extended to 2 h.

[0073] Preparation Example 4

[0074] The difference from Preparation Example 1 is that the pretreatment process in step a is omitted.

[0075] Preparation Example 5

[0076] The difference from Preparation Example 1 is that the silanization modification process in step a is omitted.

[0077] Preparation Example 6

[0078] The difference from Preparation Example 1 is that 2,2,6,6-tetramethyl-4-piperidyl methacrylate is not added in the oil phase in step b.

[0079] Preparation Example 7

[0080] The difference from Preparation Example 1 is that in step b: the molar ratio of silanized cardanol to branched butyl acrylate, methyl methacrylate, and 2,2,6,6-tetramethyl-4-piperidyl methacrylate is adjusted to 1:2.5:1:1.

[0081] The related indexes of the modified acrylate polymer emulsions of Preparation Examples 1-7 were tested:

[0082] The hydroxyl value was calculated by the amount of acetic anhydride consumed through acetylation method (GB / T 7651-2008). The acid value was determined by titration method (GB / T 264-1983), and the free acid content was determined with phenolphthalein as an indicator. The moisture content was detected by Karl Fischer method.

[0083] The silicon content was measured with an elemental analyzer (Vario EL Cube, Germany), and the grafting rate of silanized cardanol was calculated. The grafting rate = (silicon content after modification x cardanol dosage) / total silicon content of silane coupling agent.

[0084] The Mw and PDI values of the modified acrylate polymer were tested by gel permeation chromatography (GPC). Test conditions: THF solvent, flow rate 1.0 mL / min, column temperature 35°C.

[0085] The test results of the above indicators are summarized in Table 1.

[0086] Table 1

[0087]

[0088] From Table 1, Preparation Examples 1-4 show the influence of different cardanol pretreatment conditions on the silanization modification process and the properties of the subsequent polymer. The hydroxyl value of Preparation Example 2 is further reduced than that of Preparation Example 1, but the pretreatment is more thorough, so although the silanization sites are reduced, the uniformity of the silane network increases and the PDI decreases. The acid washing process in Preparation Example 3 is weakened, the acid value is high, and impurities interfere with silanization, resulting in a decrease in PDI; in Preparation Example 4, the cardanol is not pretreated and is directly silanized, resulting in a high content of free fatty acids and phenolic oligomers, the lowest grafting rate, and a high water content that inhibits the free radical polymerization process, resulting in a decrease in molecular weight.

[0089] In Preparation Example 5, no piperazine and silane groups are introduced, the molecular weight of the polymer decreases due to the lack of siloxane cross-linking, and the PDI increases due to uneven chain segment distribution. In Preparation Example 6, no 2,2,6,6-tetramethyl-4-piperidyl methacrylate, a free radical trapping agent, is added, so the Mw decreases and the PDI increases slightly. In Preparation Example 7, the proportion of hindered amine light stabilizer is increased, and the flexibility and regularity of the polymer chain segment are improved.

[0090] Example 1

[0091] A kind of outer wall weather-resistant thermal insulation waterproof coating, its preparation steps are:

[0092] 30g acid-washed fly ash floating bead, 15g silicon dioxide aerogel and 5g expanded perlite are mixed in 20mL water, 1g KH-570 is added, and the composite filler is obtained by dispersing at 60°C water bath and 300W ultrasonic power for 30min;

[0093] To 32 g of the modified acrylate polymer emulsion obtained in Preparation Example 1, 30% of the above-mentioned composite filler was premixed, and ultrasonic dispersion was performed for 20 min at a power of 300 W to uniformly disperse; then 15 mmol of 2,2'-dimethyl furan-5,5'-dicarboxylic acid dimethyl ester and 18.8 mmol of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexyl carboxylate were added, and 0.045 g of a mixture of tetramethyl guanidine and 0.495 g of diphenyl iodonium salt was further added and uniformly mixed, and the system was reacted at 78°C in an oil bath for 1.5 h (the furan ring double bond peak at 910 cm -1 disappeared); at 0.5 h and 1 h of the reaction, 40% and 30% of the above-mentioned composite filler was added, respectively.

[0094] Then 1.2 g of the premixed nano-silica and 4.8 g of hexafluorobutyl methacrylate were added, and after ultrasonic dispersion, the mixture was transferred to a quartz dish and placed in an ultraviolet curing box, and the ultraviolet wavelength was set to 365 nm and the light intensity was set to 35 mW / cm 2 ; and under the auxiliary conditions of microwave power of 500 W and frequency of 2.45 GHz, the mixture was cured for 12 min to obtain a resin matrix.

[0095] Then 0.4 g of a polyether antifoaming agent and 0.6 g of a polyurethane leveling agent were added in sequence, and stirred for 10 min; then 0.82 g of hydroxyethyl cellulose and 0.4 g of a preservative were added, and stirred for 5 min; and the pH was adjusted to 8 with triethanolamine to obtain a waterproof coating product.

[0096] Examples 2-3

[0097] A waterproof coating for exterior walls with weather resistance, heat insulation and thermal insulation, which differs from Example 1 in that the modified acrylate polymer emulsion component used is obtained from Preparation Example 2 and Preparation Example 7, respectively.

[0098] Example 4

[0099] A waterproof coating for exterior walls with weather resistance, heat insulation and thermal insulation, which differs from Example 1 in that the mass ratio of fly ash floating beads, silica aerogel and perlite is adjusted to 5:4:1 while the total amount of the composite filler remains unchanged.

[0100] Example 5

[0101] A waterproof coating for exterior walls with weather resistance, heat insulation and thermal insulation, which differs from Example 1 in that the fluorine-containing monomer used is octafluoropentyl methacrylate.

[0102] Example 6

[0103] A waterproof coating for exterior walls with weather resistance, heat insulation and thermal insulation, which differs from Example 1 in that the furfuryl dihydrazide monomer is replaced with furfuryl, and the amount remains unchanged.

[0104] Comparative Examples 1-4

[0105] An exterior wall waterproof coating, different from Example 1 in that the modified acrylate polymer emulsion component used is obtained in Preparation Examples 3-6, respectively.

[0106] Comparative Example 5

[0107] An exterior wall waterproof coating, different from Example 1 in that no perfluorobutyl methacrylate is added to the film-forming aid, and an equal amount of nanosilica is used instead.

[0108] Comparative Example 6

[0109] An exterior wall waterproof coating, different from Example 1 in that unacid-washed fly ash is used instead of acid-washed fly ash floating beads.

[0110] Comparative Example 7

[0111] An exterior wall waterproof coating, different from Example 1 in that no bisfuran monomer is added to the curing system.

[0112] The exterior wall weather-resistant, heat-insulating, waterproof coatings of all the examples and the exterior wall waterproof coatings of the comparative examples are tested as follows:

[0113] Thermal conductivity: tested in accordance with GB / T 10294-2008 “Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials”. Laser thermal conductivity instrument (TC3000E, Beijing), test temperature 25℃±1℃, humidity 50%±5%.

[0114] Dry adhesion grade determined in accordance with GB / T9286-1998.

[0115] Resistance to artificial climate aging: QUV accelerated aging box (Q-Lab QUV / spray), 340nm ultraviolet lamp, 40℃ condensation + 60℃ drying cycle.

[0116] Gloss retention after 3000h: tested using a UV-2600 ultraviolet spectrophotometer; and chromatic aberration (CIELab, CR-400 chromatic aberration instrument, Konica Minolta) measured at the same point before and after aging, D65 light source.

[0117] Water contact angle: contact angle measuring instrument (JC2000C1), 5μL deionized water droplet, measurement environment 25℃, 5-point average value;

[0118] Waterproof performance: in accordance with GB / T 1733-1993, the exterior wall waterproof coating is coated on a tinplate, completely immersed in 47-50℃, 3wt% salt water, observed once every 48h, and the time (d) of peeling, bubbling or cracking recorded.

[0119] Self-repairing efficiency: blade scratch coating (depth to substrate, width 50 pm), placed at 130 °C, humidity 50% ± 5% for 2 h, and the scratch healing degree was observed by optical microscope (BX53, Japan).

[0120] Acid and alkali resistance: according to GB / T 16777 (building waterproof coating) and GB / T 528 (rubber tensile) standards: respectively in pH = 2 hydrochloric acid solution and pH = 12 caustic solution, room temperature for 7 days. Sample size: dumbbell type I specimen, test speed: 500 mm / min. Tested by universal testing machine. Tensile strength retention rate = strength after immersion / initial strength x 100%.

[0121] The above test results are summarized in Table 2.

[0122] Table 2

[0123]

[0124]

[0125] The exterior wall weather-resistant thermal insulation waterproof coating of examples 1-6 has the synergistic effect of hindered amine silane capturing free radicals and Si-O-C network, realizing ultra-high gloss retention rate (≥95%). The tensile strength retention rate of the waterproof coating in the environment of pH = 2-12 is all ≥84%, among which the hydrolysis rate of epoxy group in strong alkali is faster, resulting in a difference in retention rate, so the tensile strength retention rate at pH = 12 is slightly lower than that at pH = 2 by 1-2%, but still meets the requirements of medium resistance.

[0126] Combining examples 1, 2 and comparative examples 1-2, the acid value and hydroxyl value of cardanol affect the properties of modified acrylate polymer and subsequent exterior wall waterproof coating. Among them, the hydroxyl value of cardanol used in example 2 is lower than that of example 1, but the removal rate of phenolic oligomers and free fatty acids and other impurities is higher, so the molecular structure is more regular, and the silane grafting rate increases. This phenomenon breaks the traditional cognition that the hydroxyl value is positively correlated with the grafting rate. The acid value of cardanol pretreatment is too high (comparative example 1) or cardanol is not pretreated (comparative example 2), which causes impurities to remain in the competition reaction site with the silane coupling agent, resulting in insufficient Si-O-C bond density, uneven silane network, and low crosslinking density; further leading to increased heat conduction path and increased thermal conductivity coefficient; the residual acid value also causes catalytic degradation, rapid decrease in pH = 12 retention rate, and easy oxidation chain scission of the coating under ultraviolet radiation, accelerating the aging of the coating, decreasing the gloss retention rate, and increasing the color difference.

[0127] Compared with Example 1, the proportion of hindered amine light stabilizer in Example 3 is increased, which improves the light stability and weather resistance of the waterproof coating for external wall weather resistance, heat insulation and thermal insulation; at the same time, the modified acrylate polymer chain segment has high flexibility and high self-repairing efficiency. The waterproof coating of Comparative Example 3 is not silanized, and the waterproof time is only 15 days. Comparative Example 4 lacks the hindered amine monomer 2,2,6,6-tetramethyl-4-piperidyl methacrylate, which leads to the decrease of the mobility of the modified acrylate polymer chain segment, and the self-repairing efficiency, acid and alkali resistance and color difference of the waterproof coating for external wall are greatly reduced.

[0128] Example 4 further reduces the thermal conductivity of the waterproof coating for external wall weather resistance, heat insulation and thermal insulation by increasing the proportion of nanoporous aerogel and optimizing the heat conduction path. The fly ash used in Comparative Example 6 is not acid-washed, and its specific surface area is only 1.6 m 2 / g, the interface bonding force is poor, and the filler is not uniformly dispersed; the surface Fe2O3 residue forms a thermal bridge, making the heat conduction path straight through, and the thermal conductivity of the waterproof coating for external wall weather resistance, heat insulation and thermal insulation increases; the interface defects accelerate aging.

[0129] Example 5 selects a fluorine-containing monomer octafluoropentyl ester with lower surface energy, which increases the hydrophobicity; but the carbon chain of octafluoropentyl ester is too long, and the molecular migration rate decreases, so the waterproof coating for external wall weather resistance, heat insulation and thermal insulation is prone to microcracks, and the film formation and waterproof performance are affected. Example 6 selects furfuryl, which contains two additional carbonyl groups, and its conjugation effect can enhance the activity of furan ring double bond, so as to improve the crosslinking rate. But the hydrogen bond formed between carbonyl group and polymer chain hinders the movement of chain segment, so the flexibility of the waterproof coating for external wall weather resistance, heat insulation and thermal insulation decreases. Comparative Example 5 omits perfluorobutyl methacrylate, resulting in the absence of the hydrophobic layer, and the waterproof performance of the waterproof coating for external wall weather resistance, heat insulation and thermal insulation is poor and the acid resistance is insufficient. Comparative Example 7 lacks a double-furan monomer, which leads to the absence of the interpenetrating network formed by the furan ring and the epoxy group curing, and the network defect rate increases, so the cohesion and mechanical strength of the coating of the waterproof coating for external wall weather resistance, heat insulation and thermal insulation decrease.

[0130] The above examples are only for illustrating the technical concept and characteristics of the present application, and are intended to enable those skilled in the art to understand the content of the present application and to implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and essence of the present application shall be covered within the protection scope of the present application.

Claims

1. A waterproof coating for exterior wall weather resistance and thermal insulation, characterized in that, The composition comprises the following components by weight: modified acrylate polymer emulsion 27-35 parts, composite filler 35-50 parts, curing system 5-10 parts, film forming aid 4-8 parts, defoaming agent 0.1-0.5 parts, leveling agent 0.3-0.8 parts, mildewcide 0.2-0.6 parts, thickening agent 0.5-1.0 parts, pH regulator 1-5 parts; The modified acrylate polymer emulsion is prepared by the following steps: a. Pretreatment and silanization modification of cardanol: cardanol is pretreated by acid washing, molecular distillation and dehydration, and modified with piperazine silane coupling agent to obtain silanized cardanol; after pretreatment, the hydroxyl value of the cardanol is 180-200 mgKOH / g, and the acid value is ≤2 mgKOH / g; b. Monomer pre-emulsification: the mixed monomers containing silanized cardanol are dissolved in butanone-butyl acetate solvent to obtain an oil phase, which is then mixed with an aqueous phase containing emulsifiers, and subjected to homogenization emulsification treatment to form a pre-emulsion; the mixed monomers include silanized cardanol, branched butyl acrylate, methyl methacrylate and hindered amine light stabilizer in a molar ratio of 1:2.5:1-1.5:0.5-1; c. Free radical polymerization: the pre-emulsion of step b and initiator are added to the reaction kettle in two steps to carry out a two-step polymerization process; then a redox system is added to terminate the polymerization and eliminate residual monomers, and a modified acrylate polymer emulsion is obtained; The curing system includes bifuran monomer, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylmethyl carboxylate, free radical scavenger and guanidino catalyst; the molar ratio of bifuran monomer to 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylmethyl carboxylate is 1:1.05-1.

5.

2. The water repellent coating according to claim 1, wherein In step a, the modification process is as follows: an ethanol-water solution of piperazine silane coupling agent with pH 4-5 is pre-hydrolyzed at 50-60°C for 30-40 min; then the pretreated cardanol is modified at 65-80°C for 2-3 h; the piperazine silane coupling agent is γ-piperazine propyl methyl dimethoxy silane.

3. The water repellent coating of claim 1, wherein In step b, the volume ratio of water-oil phase is 3-5:1, and the amount of emulsifier in the aqueous phase is 0.5-2.0 wt%; the hindered amine light stabilizer is 2,2,6,6-tetramethyl-4-piperidyl isobutyric acid ester. The treatment conditions for homogenization emulsification are as follows: nitrogen atmosphere, homogenization at 4000-10000 rpm for 30 min, control of emulsion D50 at 300±50 nm, and adjustment of pH to 7-7.5 with sodium bicarbonate.

4. The water repellent coating of claim 1, wherein In step c, the two-step polymerization process is as follows: 1) Under a nitrogen atmosphere, 70-80 wt% of the pre-emulsion of step b and 50 wt% of the initiator are taken into the reaction kettle, and reacted at 70-78°C for 1-2 h to obtain an oligomer seed; 2) Then the remaining pre-emulsion and initiator are added, the temperature is raised to 80-85°C, and the temperature is continued for 1-1.5 h; 0.4-0.8 wt% of a redox system is added to terminate the reaction and eliminate residual monomers; after the system is cooled to room temperature, the pH is adjusted to 8.0-8.5 with ammonia water for storage. The initiator is ammonium persulfate, and the amount is 0.8-1.5wt% of the total mass of monomers; the redox system is t-butyl hydroperoxide and ascorbic acid with a mass ratio of 2:1; the branching degree of branched butyl acrylate is 3-5 branches, and the glass transition temperature is ≤-45℃.

5. The water repellent coating of claim 1, wherein The bifuran monomer is one of 2,2'-bifuran-5,5'-dicarboxylic acid dimethyl ester, bifuran malonate, bifuran benzoate, and furil. The guanidino catalyst is 0.05-0.20wt% tetramethyl guanidine, and the free radical scavenger is 0.5-1.0wt% diphenyl iodonium salt, based on the mass of bifuran monomers.

6. The water repellent coating of claim 1, wherein The film-forming aid is a mixture of nano-silicon dioxide and fluorine-containing acrylate monomers with a mass ratio of 1:3-5; the particle size of nano-silicon dioxide is 20-30nm; the fluorine-containing monomer is a fluorinated alkyl methacrylate with 6-10 fluorine atoms in the molecule and a fluorinated alkyl carbon chain length of 4-8 carbon atoms, including but not limited to perfluorobutyl methacrylate and octafluoropentyl methacrylate.

7. The water repellent coating of claim 1, wherein The composite filler is acid-washed fly ash floating beads, silica aerogel, and expanded perlite with a mass ratio of 5-7:2-4:1, and is obtained by ultrasonic dispersion in a 1.5-2.5wt% silane coupling agent solution at 50-60℃; The preservative is isothiazolinone and zinc pyrithione, the defoaming agent is a polyether defoaming agent, the thickening agent is hydroxyethyl cellulose, the leveling agent is a polyurethane leveling agent, and the pH adjuster is triethanolamine.

8. The water repellent coating of claim 1, wherein, The acid-washed fly ash floating bead has the following preparation steps: fly ash floating bead is treated by ultrasonic wave in a mixed solution of oxalic acid and hydrochloric acid, calcined at 700-800 DEG C, ball milled to D50 of 1-5 mu m, and specific surface area of greater than or equal to 180 m 2 / g. The pore size of the silica aerogel is 20-50 nm, the porosity is ≥ 90%, and the specific surface area is ≥ 800 m 2 / g; the expanded perlite has a particle size of 30-60 μm.

9. The preparation method of the weather-proof, thermal-insulation, waterproof coating for exterior wall according to any one of claims 1-8, characterized in that, The method comprises the following steps: Pre-mix the modified acrylate polymer emulsion with the composite filler to obtain a pre-mixed slurry; Add the curing system, click to cure, and add the remaining composite filler in 2-3 portions during the process; then add the film-forming aid and ultraviolet cure under microwave assistance; Add the defoaming agent and leveling agent and stir for 8-12min; Then add the thickening agent and preservative and stir; Adjust the pH to 7-8 with the pH adjuster to obtain a waterproof coating.

10. The production method according to claim 9, wherein The click curing conditions are: the reaction temperature is 75-85℃, and the reaction time is 1.5-2h; the interval between the addition of the remaining composite filler is not less than 20min. The ultraviolet curing conditions are: light intensity of 15-40 mW / cm 2 , wavelength of 365-385 nm, and curing time of 10-15 min; and the microwave auxiliary power is 200-300 W.

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