Weather-proof, heat-insulating and waterproof coating for external walls and preparation method thereof

Abstract

The application discloses a waterproof coating for outer wall weather resistance, heat insulation and heat preservation and a preparation method thereof. The waterproof coating comprises the following components in parts 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, mildew-proof agent 0.2-0.6 parts, thickening agent 0.5-1.0 parts and pH regulator 1-5 parts. The modified acrylate polymer emulsion is prepared by pretreating and silanization modifying cardanol, monomer pre-emulsification and free radical polymerization. The waterproof coating provided by the application introduces Si-O-C network and hindered amine free radical capture system to improve weather resistance; fluorine compound-nano silicon dioxide constructs roughness-low surface energy synergistic waterproof interface; acid washing fly ash floating beads, silica aerogel and expanded perlite filler are compounded to form multiple heat conduction scattering paths to realize cross-scale porous filler heat preservation; and the waterproof coating can serve in complex environments such as large temperature difference fluctuation and acid rain.

Description

Technical Field

[0001] This invention relates to the field of water-based coatings technology, specifically to a waterproof coating for exterior wall weather resistance and thermal insulation, and its preparation method. Background Technology

[0002] Exterior wall coatings are paints applied to the entire exterior walls of buildings. Their main functions are decoration and protection, making the building look smooth and aesthetically pleasing while also protecting it. Compared to interior wall coatings, exterior wall coatings are exposed to the outdoor environment and must withstand multiple challenges, including ultraviolet radiation, temperature fluctuations, and rain erosion. However, current technologies have significant shortcomings in achieving a balance of performance in exterior wall coatings.

[0003] 1. Insufficient weather resistance: Traditional resin modification often uses a single silane coupling agent to achieve weather resistance modification. Although it can temporarily improve interfacial bonding, it lacks a free radical scavenging mechanism. Under long-term ultraviolet irradiation, the coating is prone to oxidative degradation, manifested as a decrease in gloss retention (≤80% after 3000h), increased color difference (ΔE=≥3.2), and even chalking.

[0004] 2. Limited thermal insulation performance: Most of them use single porous thermal insulation materials such as carbonized red mud and expanded perlite. Their pore structure is simple and cannot form an effective heat conduction barrier path, resulting in low thermal insulation efficiency (thermal conductivity is generally ≥0.035W / (m·K)).

[0005] 3. Waterproof interface defects: When constructing a waterproof interface, conventional hydrophobic layers achieve waterproofing through physical blending of fluorides, but the surface energy control and roughness design lack coordination. The water contact angle is mostly ≤105°, and swelling easily occurs after immersion. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a weather-resistant, heat-insulating, and waterproof coating for exterior walls, and its preparation method.

[0007] This invention provides a weather-resistant, heat-insulating, and waterproof coating for exterior walls, comprising the following components in parts by weight:

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

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

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

[0011] b. Monomer pre-emulsification: A mixed monomer containing silanized cashew nut shells is dissolved in a butanone-butyl acetate solvent to obtain an oil phase, which is then mixed with an aqueous phase containing an emulsifier and homogenized to form a pre-emulsion; the mixed monomers include silanized cashew nut shells and branched butyl acrylate, methyl methacrylate and hindered amine light stabilizer in a molar ratio of 1:2.5:1 to 1.5:0.5 to 1.

[0012] c. Free radical polymerization: The pre-emulsion and initiator from step b are added to the reactor in two separate steps to carry out a two-step polymerization process; then a redox system is added to terminate the polymerization, resulting in a modified acrylate polymer emulsion.

[0013] The curing system includes a difuran monomer, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, a free radical scavenger, and a guanidine catalyst; wherein the molar ratio of the difuran monomer to the 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate is 1:1.05 to 1.5.

[0014] The hydroxyl value reflects the hydroxyl content in cashew nut shell phenols and serves as the active site for the silane coupling agent modification reaction. A low hydroxyl value leads to insufficient grafting rate, an incomplete silane network, and poor weather resistance and water resistance of the coating. The acid value reflects the content of free fatty acids in cashew nut shell phenols: an excessively high acid value leads to pH instability in the system, inhibits catalyst activity, interferes with silanization reactions and subsequent free radical polymerization, and degrades the mechanical properties of the coating.

[0015] By acid washing (removing free fatty acids), molecular distillation (removing phenolic oligomers), and dehydration (reducing moisture content), the hydroxyl active sites of cashew phenol are more fully exposed, and the silanization reaction is more uniform.

[0016] Optionally, in step a: the modification process specifically involves: pre-hydrolyzing an ethanol-water solution of a piperazine-silane coupling agent with a pH of 4-5 at 50-60°C for 30-40 min, and then reacting it with pretreated cashew phenol in a water bath at 65-80°C for 2-3 h; the piperazine-silane coupling agent is γ-piperazinylpropylmethyldimethoxysilane.

[0017] Silane is covalently anchored to the cashew phenol molecule to ensure waterproofing while preserving the double bonds in the cashew phenol side chain.

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

[0019] The homogenization emulsification conditions are as follows: homogenization at a nitrogen atmosphere and a rotation speed of 4000-10000 rpm for 30 min, controlling the emulsion D50 to 300±50 nm, and adjusting the pH to 7-7.5 with sodium bicarbonate.

[0020] Optionally, in step c: the two-step aggregation process specifically includes:

[0021] 1) Under a nitrogen atmosphere, 70-80 wt% of the pre-emulsion from step b and 50 wt% of the initiator are placed in a reactor and reacted at 70-78°C for 1-2 hours to obtain oligomeric seeds;

[0022] 2) Then add the remaining pre-emulsion and initiator, heat to 80-85℃, and continue to keep warm for 1-1.5h; add 0.4-0.8wt% 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 and store.

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

[0024] Optionally, the bisfuran monomer is one of 2,2'-bisfuran-5,5'-dicarboxylic acid dimethyl ester, bisfuran malonate, bisfuran benzoate, and furoyl;

[0025] The guanidine catalyst is 0.05–0.20 wt% tetramethylguanidine, and the free radical scavenger is 0.5–1.0 wt% diphenyliodonium salt, based on the mass of the bisfuran monomer.

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

[0027] Nano-silica forms a micro-rough surface through physical stacking. When combined with low-surface-energy fluorinated acrylates, it enhances the water contact angle through a synergistic effect of roughness and low surface energy. Furthermore, the fluoride molecular segments encapsulating the nano-silica impart both hydrophobicity and flexibility. The silanol groups on the nano-silica surface can also form hydrogen bonds with the Si-OC network in the modified acrylate polymer, increasing the coating's cohesion and tensile strength.

[0028] Optionally, the composite filler is obtained by ultrasonic dispersion of pickled fly ash cenospheres, silica aerogel and expanded perlite in a mass ratio of 5-7:2-4:1 in a 1.5-2.5 wt% silane coupling agent solution at 50-60°C.

[0029] The preservatives are isothiazolinone and zinc pyrithione, the defoamer is a polyether defoamer, the thickener is hydroxyethyl cellulose, the leveling agent is a polyurethane leveling agent, and the pH adjuster is triethanolamine.

[0030] Optionally, the preparation steps of the acid-washed fly ash celery beads are as follows: the fly ash celery beads are ultrasonically treated with a mixture of 5wt% oxalic acid and 3wt% hydrochloric acid (volume ratio 1:1); after washing with water until neutral, they are calcined at 700-800℃ for 2 hours and ball-milled until the D50 is 1-5μm and the specific surface area is ≥180m². 2 / g;

[0031] Fly ash cenospheres are activated by acid treatment to remove surface metal oxides, which can increase the specific surface area and thus enhance the interfacial bonding with acrylic acid and composite fillers.

[0032] Optionally, the silica aerogel has a pore size of 20–50 nm, a porosity ≥90%, and a specific surface area ≥800 m². 2 / g; the expanded perlite has a particle size of 30-60μm.

[0033] The nanoscale pores of silica aerogel restrict the thermal motion of air molecules, while the mesopores of fly ash cenospheres inhibit convective heat transfer; the macropores of expanded perlite form an air layer that reflects thermal radiation. These three components form a three-tiered scattering system of "nanopore-mesopore-macropore" to achieve heat preservation.

[0034] This invention also protects the preparation method of the aforementioned weather-resistant, heat-insulating, and waterproof coating for exterior walls, comprising the following steps:

[0035] The modified acrylate polymer emulsion was premixed with the composite filler to obtain a premixed slurry; it was added to the curing system and cured by clicking, with the remaining composite filler added in 2 to 3 batches during the process; then a film-forming aid was added and cured under microwave-assisted UV curing.

[0036] Add defoamer and leveling agent in sequence, and stir for 8-12 minutes; then add thickener and preservative and stir; adjust the pH to 7-8 with pH adjuster to obtain waterproof coating.

[0037] Optionally, the curing conditions are: a reaction temperature of 75-85°C, a reaction time of 1.5-2 hours, and an interval of not less than 20 minutes between additions of the remaining composite filler;

[0038] The UV curing conditions are: light intensity of 15–40 mW / cm². 2 The wavelength is 365-385nm, and the total curing time is 10-15min; the microwave-assisted power is 200-300W.

[0039] Beneficial effects:

[0040] This invention achieves a synergistic improvement in the weather resistance, thermal insulation, and waterproofing performance of exterior wall coatings through multi-dimensional technological innovation, as detailed below:

[0041] Significant improvement in weather resistance: A Si-OC network with UV shielding effect and a hindered amine radical capture system are constructed to inhibit coating oxidative degradation. After 3000h QUV accelerated aging, the gloss retention rate is ≥95%, the color difference ΔE is ≤1.2, and there is no surface differentiation.

[0042] Multi-scale porous insulation: Acid-washed fly ash cenospheres, silica aerogel and expanded perlite are combined to form a multi-pore heat conduction and scattering path of macropore-mesopore-nanopore, with a thermal conductivity as low as 0.028W / (m·K).

[0043] Synergistic waterproof interface construction: Fluoride-nano silica compound forms a rough-low surface energy hydrophobic interface with a water contact angle ≥130°; tensile strength retention rate ≥88% under pH=2~12 environment, suitable for harsh environments such as large temperature fluctuations and acid rain.

[0044] Self-healing adaptability: The dual furan-epoxy curing system gives the coating a self-healing efficiency of over 84%, and the Diels-Alder reversible reaction enables microcrack self-healing, making it suitable for spraying on complex exterior wall substrates. Detailed Implementation

[0045] To make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to specific examples.

[0046] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0047] The following are the sources of raw materials involved in the implementation method. Experimental materials not mentioned can be purchased from conventional biochemical reagent companies.

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

[0049] γ-piperazinylpropylmethyldimethoxysilane, Wuhan Kanos Technology Co., Ltd.

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

[0051] Nano-silica with a particle size D50 of 25 nm and a specific surface area of ​​190 m² 2 / g, Jining Tangyi Chemical Co., Ltd.

[0052] Fly ash cenospheres, 1250 mesh, Xingtai Jia Hui Insulation Materials Co., Ltd.

[0053] Expanded perlite, expansion ratio 12, SiO2 content 70wt%, density 80kg / m³ 3 It was ground through a 250-mesh sieve.

[0054] Nano-sized silica aerogel powder, with a particle size range of 0.1–0.5 mm, a pore size of 40 nm, and a specific surface area of ​​850 m². 2 / g, porosity 93%, Dacheng County Songzhang Jikangyu Insulation Material Factory.

[0055] TAFIGEL-PUR80 polyurethane leveling agent, pH ~ 7.5, Dongguan Terunde Chemical Materials Co., Ltd.

[0056] SH-237-7 Polyether Defoamer, Shenzhen Jipeng Silicon Fluorine Materials Co., Ltd.

[0057] In a specific embodiment of the present invention, the pickling process for pickling fly ash cenospheres is as follows:

[0058] Take 100g of fly ash cenospheres and add them to a 1:1 mixture of 5wt% oxalic acid and 3wt% hydrochloric acid (200mL). Sonicate the mixture at 200W for 30min, wash with distilled water until neutral, and calcine in a muffle furnace at 800℃ for 2h. Finally, ball mill the mixture to D50 = 2.5μm.

[0059] After acid washing, the specific surface area of ​​fly ash cenospheres, measured by BET, increased from 1.6 m² / s². 2 / g rises to 210m 2 / g.

[0060] Preparation Example 1

[0061] Preparation of modified acrylate polymer emulsion:

[0062] a. Cashew nut pretreatment and silanization reaction:

[0063] Pretreatment: Cashew phenol was ultrasonically acid-washed in a 5 wt% citric acid solution at 60°C for 30 min, and the acid was removed by separation. After washing to neutrality, it was filtered and then transferred to a molecular distillation apparatus. The cashew phenol fraction was collected under vacuum of 0.1 kPa, evaporation surface temperature of 150°C, and condensation surface temperature of 80°C, and its monophenol content was measured to be 90%. Finally, under nitrogen bubbling protection, it was dehydrated at 110°C for 30 min until the water content was ≤0.3 wt% to avoid silane hydrolysis side reaction.

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

[0065] b. Monomer pre-emulsification: Prepare 200 mL of an aqueous phase containing 1.2 wt% emulsifier and preheat to 60 °C; mix 0.05 mol of silanized cashew nut shell powder 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-piperidinyl isobutylene ester in a methyl ethyl ketone-butyl acetate mixed solvent (v:v = 1:1) to obtain an oil phase; add the oil phase to the aforementioned preheated aqueous phase, and then homogenize and emulsify at 5000 rpm for 30 min under a nitrogen atmosphere, controlling the pH to 7 with sodium bicarbonate to obtain a pre-emulsion; the particle size D50 was measured to be 305 nm;

[0066] c. Free radical polymerization:

[0067] 1) Under a nitrogen atmosphere, 80% of the pre-emulsion obtained in step b and 0.23 g of ammonium persulfate were placed in a reactor and reacted at 75°C for 2 h to obtain oligomeric seeds;

[0068] 2) Add the remaining 20% ​​of the pre-emulsion and 0.23g of ammonium persulfate simultaneously through a constant pressure dropping funnel, raise the temperature to 80℃, continue to keep warm for 1 hour, and then add 0.2g of tert-butyl hydrogen peroxide and 0.1g of ascorbic acid to terminate the polymerization; cool the system to room temperature, adjust the pH to 8.0 with ammonia water to obtain the 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 for washing is reduced to 1 wt%, the washing 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-piperidinyl isobutylene ester is not added to 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 cashew phenol to branched butyl acrylate, methyl methacrylate, and 2,2,6,6-tetramethyl-4-piperidinyl isobutylene ester is adjusted to 1:2.5:1:1.

[0081] The relevant properties of the modified acrylate polymer emulsions prepared in Examples 1-7 were tested:

[0082] The hydroxyl value was calculated by acetylation method (GB / T 7651-2008) based on the amount of acetic anhydride consumed. The acid value was determined by titration method (GB / T264-1983), with phenolphthalein as an indicator to determine the free acid content. The moisture content was determined by Karl Fischer method.

[0083] The silicon content was determined using an elemental analyzer (Vario EL Cube, Germany), and the grafting rate of silanized cashew nut shell powder was calculated. The grafting rate was calculated as: (modified silicon content × cashew nut shell powder dosage) / total silicon content of the silane coupling agent.

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

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

[0086] Table 1

[0087]

[0088] Table 1 shows the effects of different cashew nut shell pretreatment conditions on the silanization modification process and the properties of the subsequent polymer. In Preparation Example 2, the hydroxyl value was further reduced compared to Preparation Example 1, but the pretreatment was more thorough. Therefore, although the number of silanization sites decreased, the uniformity of the formed silane network increased, and the PDI decreased. In Preparation Example 3, the acid washing process was weakened, resulting in a high residual acid value and impurities interfering with silanization, leading to a decrease in PDI. In Preparation Example 4, cashew nut shell shell was directly silanized without pretreatment, resulting in a higher residual amount of free fatty acids and phenolic oligomers, and the lowest grafting rate. Simultaneously, the excessively high moisture content inhibited the free radical polymerization process, causing a decrease in molecular weight.

[0089] Preparation Example 5 did not introduce piperazine and silane groups; the polymer molecular weight decreased due to the lack of siloxane crosslinking, while the PDI increased due to uneven chain segment distribution. Preparation Example 6 did not add 2,2,6,6-tetramethyl-4-piperidinyl isobutylene ester and lacked a free radical scavenger; therefore, Mw decreased while PDI increased slightly. Preparation Example 7 increased the proportion of hindered amine light stabilizer, improving the flexibility and regularity of the polymer chains.

[0090] Example 1

[0091] A weather-resistant, heat-insulating, and waterproof coating for exterior walls, the preparation steps of which are as follows:

[0092] 30g of pickled fly ash cenospheres, 15g of silica aerogel and 5g of expanded perlite were mixed in 20mL of water, and 1g of KH-570 was added; the mixture was dispersed in a 60℃ water bath and under 300W ultrasonic power for 30min to obtain a composite filler.

[0093] 32g of the modified acrylate polymer emulsion obtained in Preparation Example 1 was premixed with 30% of the above-mentioned composite filler and sonicated at 300W for 20 min to ensure uniform dispersion. Then, 15 mmol of 2,2'-bisfuran-5,5'-dicarboxylic acid dimethyl ester and 18.8 mmol of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate were added, followed by 0.045g of tetramethylguanidine and 0.495g of diphenyliodonium salt, which were mixed thoroughly. The system was reacted in an oil bath at 78°C for 1.5 h (the furan ring double bond peak was monitored at 910 cm⁻¹ by FT-IR). -1 (Disappears); 40% and 30% of the above composite filler were added at 0.5h and 1h of the reaction, respectively.

[0094] Subsequently, 1.2g of premixed nano-silica and 4.8g of hexafluorobutyl methacrylate were incorporated into the mixture, ultrasonically dispersed, and then transferred to a quartz dish. The dish was then placed in a UV curing chamber with a UV wavelength of 365nm and a light intensity of 35mW / cm². 2 The resin matrix was obtained by curing under microwave power of 500W and frequency of 2.45GHz for 12 minutes.

[0095] Next, add 0.4g of polyether defoamer and 0.6g of polyurethane leveling agent in sequence, and stir for 10 minutes; then add 0.82g of hydroxyethyl cellulose and 0.4g of preservative, and stir for 5 minutes; adjust the pH to 8 with triethanolamine to obtain the finished waterproof coating.

[0096] Examples 2-3

[0097] A weather-resistant, heat-insulating, and waterproof coating for exterior walls, which differs from Example 1 in that the modified acrylic polymer emulsion components used are those obtained in Preparation Example 2 and Preparation Example 7, respectively.

[0098] Example 4

[0099] A waterproof coating for weather-resistant and heat-insulating exterior walls differs from Example 1 in that, while keeping the total amount of composite filler unchanged, the mass ratio of fly ash cenospheres, silica aerogel, and perlite is adjusted to 5:4:1.

[0100] Example 5

[0101] A waterproof coating for weather-resistant, heat-insulating, and heat-preserving exterior walls, which differs from Example 1 in that the fluorinated monomer of methacrylic acid used is octafluoropentyl methacrylate.

[0102] Example 6

[0103] A waterproof coating for weather-resistant, heat-insulating, and thermally insulating exterior walls differs from Example 1 in that the bisfuran monomer used is replaced with furoyl, while the dosage remains the same.

[0104] Comparative Examples 1-4

[0105] An exterior wall waterproof coating differs from Example 1 in that the modified acrylic polymer emulsion components used are those obtained in Preparation Examples 3 to 6.

[0106] Comparative Example 5

[0107] An exterior wall waterproof coating differs from Example 1 in that perfluorobutyl methacrylate is not added to the film-forming aid; instead, an equal mass of nano-silica is used.

[0108] Comparative Example 6

[0109] An exterior wall waterproof coating differs from Example 1 in that it uses un-acid-washed fly ash instead of acid-washed fly ash celery beads.

[0110] Comparative Example 7

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

[0112] The exterior wall weather-resistant, heat-insulating, and waterproof coatings of all embodiments were tested against the comparative exterior wall waterproof coatings:

[0113] Thermal conductivity: Tested according to GB / T 10294-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials". Laser thermal conductivity meter (TC3000E, Beijing), test temperature 25℃±1℃, humidity 50%±5%.

[0114] The dry adhesion rating was determined according to GB / T9286-1998.

[0115] Artificial weathering resistance: QUV accelerated aging chamber (Q-Lab QUV / spray), 340nm ultraviolet lamp, 40℃ condensation + 60℃ drying cycle.

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

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

[0118] Waterproof performance: According to GB / T 1733-1993, the exterior wall waterproof coating is applied to the tinplate and completely immersed in a 3wt% salt solution at 47-50℃. Observe every 48 hours and record the time (d) for peeling, blistering or cracking.

[0119] Self-healing efficiency: The coating (depth to substrate, width 50μm) with blade scratches was placed at 130℃ and humidity 50%±5% for 2h, and the degree of scratch healing was observed using an optical microscope (BX53, Japan).

[0120] Acid and alkali resistance: According to GB / T 16777 (Building Waterproof Coatings) and GB / T 528 (Rubber Tensile Testing) standards: Immersed in hydrochloric acid solution (pH=2) and caustic soda solution (pH=12) at room temperature for 7 days respectively. Specimen size: Dumbbell-shaped Type I specimen; Testing speed: 500 mm / min. Tested using a universal testing machine. Tensile strength retention rate = (Strength after immersion / Initial strength) × 100%.

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

[0122] Table 2

[0123]

[0124]

[0125] The weather-resistant and heat-insulating waterproof coatings for exterior walls in Examples 1-6 exhibit a synergistic effect of hindered amine silanes capturing free radicals and a Si-OC network, achieving an ultra-high gloss retention rate (≥95%). The tensile strength retention rate of the waterproof coatings is ≥84% in environments ranging from pH 2 to 12. The epoxy groups hydrolyze more rapidly in strong alkalis, leading to differences in retention rates; therefore, the tensile strength retention rate at pH 12 is slightly lower (1-2%) than at pH 2, but still meets the requirements for resistance to various media.

[0126] In conjunction with Examples 1 and 2, as well as Comparative Examples 1 and 2, the acid value and hydroxyl value of cashew phenol both affect the properties of the modified acrylate polymer and the subsequent exterior waterproof coating. Specifically, the cashew phenol used in Example 2 had a lower hydroxyl value than that in Example 1, but the removal rate of impurities such as phenolic oligomers and free fatty acids was higher, resulting in a more regular molecular structure and an increased silane grafting rate. This phenomenon breaks through the traditional understanding that hydroxyl value and grafting rate are positively correlated. Excessively high acid value in cashew phenol pretreatment (Comparative Example 1) or no pretreatment (Comparative Example 2) both resulted in residual impurities competing with the silane coupling agent for reaction sites, leading to insufficient Si-OC bond density, uneven silane network, and low crosslinking density. This, in turn, increased heat conduction paths and increased thermal conductivity. Residual acid value also triggers catalytic degradation, a rapid decrease in retention rate at pH=12, and accelerated coating aging due to oxidative chain scission under ultraviolet radiation, resulting in decreased gloss retention and increased color difference.

[0127] Compared to Example 1, Example 3 showed an increased proportion of hindered amine light stabilizer, which improved the light stability and weather resistance of the waterproof coating for exterior wall weathering and thermal insulation. Simultaneously, the modified acrylate polymer segments exhibited high flexibility and high self-healing efficiency. In contrast, the exterior wall waterproof coating of Comparative Example 3, without silanization modification, only provided waterproofing for 15 days. Comparative Example 4, lacking the hindered amine monomer 2,2,6,6-tetramethyl-4-piperidinyl isobutylene ester, experienced decreased mobility of the modified acrylate polymer segments, resulting in a significant reduction in the self-healing efficiency, acid and alkali resistance, and color difference of the exterior wall waterproof coating.

[0128] Example 4 further reduced the thermal conductivity of the weather-resistant and heat-insulating waterproof coating for exterior walls by increasing the proportion of nanoporous aerogel and optimizing the heat conduction path. Comparative Example 6 used fly ash that was not acid-washed, and its specific surface area was only 1.6 m². 2 / g, poor interfacial bonding and uneven filler dispersion; Fe2O3 residue on the surface forms thermal bridges, making the heat conduction path straight and increasing the thermal conductivity of the waterproof coating for weather-resistant and heat-insulating exterior walls; interface defects accelerate aging.

[0129] Example 5 used octafluoropentyl ester, a fluorinated monomer with lower surface energy, increasing hydrophobicity; however, the octafluoropentyl ester carbon chain was too long, reducing the molecular migration rate, thus making the waterproof coating for weather-resistant and thermally insulating exterior walls prone to micro-cracks, affecting film formation and waterproofing performance. Example 6 used furo-oleoyl ester containing two additional carbonyl groups, whose conjugation effect could enhance the activity of furan ring double bonds, increasing the crosslinking rate. However, the hydrogen bonds formed between the carbonyl groups and the polymer chains hindered chain segment movement, thus reducing the flexibility of the waterproof coating for weather-resistant and thermally insulating exterior walls. Comparative Example 5 omitted perfluorobutyl methacrylate, resulting in a lack of a hydrophobic layer, leading to poorer waterproofing and insufficient acid resistance in the waterproof coating for weather-resistant and thermally insulating exterior walls. Comparative Example 7 lacked a difuran monomer, resulting in the absence of the interpenetrating network formed by the curing of furan rings and epoxy groups, increasing the network defect rate, and reducing the coating cohesion and mechanical strength of the waterproof coating for weather-resistant and thermally insulating exterior walls.

[0130] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A waterproof coating for exterior wall weather resistance and thermal insulation, characterized in that, The product comprises the following components in parts by weight: 27-35 parts modified acrylate polymer emulsion, 35-50 parts composite filler, 5-10 parts curing system, 4-8 parts film-forming aid, 0.1-0.5 parts defoamer, 0.3-0.8 parts leveling agent, 0.2-0.6 parts mildew inhibitor, 0.5-1.0 parts thickener, and 1-5 parts pH adjuster; the modified acrylate polymer emulsion is prepared by the following steps: a. Pretreatment and silanization modification of cashew nut shells: cashew nut shells are pretreated by acid washing, molecular distillation and dehydration, and then modified with piperazine silane coupling agent to obtain silanized cashew nut shells; after pretreatment, the cashew nut shells have a hydroxyl value of 180-200 mgKOH / g and an acid value ≤2 mgKOH / g; b. Monomer pre-emulsification: A mixed monomer containing silanized cashew nut shells is dissolved in a butanone-butyl acetate solvent to obtain an oil phase, which is then mixed with an aqueous phase containing an emulsifier and homogenized to form a pre-emulsion; the mixed monomers include silanized cashew nut shells and branched butyl acrylate, methyl methacrylate and hindered amine light stabilizer in a molar ratio of 1:2.5:1 to 1.5:0.5 to 1. c. Free radical polymerization: The pre-emulsion and initiator from step b are added to the reactor in two separate steps for a two-step polymerization process; then a redox system is added to terminate the polymerization, yielding a modified acrylate polymer emulsion; the curing system includes a difuran monomer, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, a free radical scavenger, and a guanidine catalyst; wherein the molar ratio of the difuran monomer to 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate is 1:1.05-1.5; the hindered amine light stabilizer is 2,2,6,6-tetramethyl-4-piperidinyl isobutylene ester; the composite filler is acid-washed fly ash celery beads, silica aerogel, and expanded perlite in a mass ratio of 5-7:2-4:1, in 1 The film-forming aid is obtained by ultrasonic dispersion in a 0.5-2.5 wt% silane coupling agent solution at 50-60°C; the film-forming aid is a mixture of nano-silica and fluorinated acrylate monomers in a mass ratio of 1:3-5; wherein the nano-silica particle size is 20-30 nm.

2. The waterproof coating as described in claim 1, characterized in that, In step a: the modification process specifically involves: pre-hydrolyzing an ethanol-water solution of a piperazine-silane coupling agent with a pH of 4-5 at 50-60°C for 30-40 min; then reacting it with pretreated cashew phenol at 65-80°C for 2-3 h; the piperazine-silane coupling agent is γ-piperazine-propylmethyldimethoxysilane.

3. The waterproof coating as described in claim 1, characterized in that, In step b: the water-oil phase volume ratio is 3-5:1, the emulsifier dosage in the aqueous phase is 0.5-2.0 wt%; the homogenization emulsification conditions are: nitrogen atmosphere, homogenization at 4000-10000 rpm for 30 min, controlling the emulsion D50 to 300±50 nm, and adjusting the pH to 7-7.5 with sodium bicarbonate.

4. The waterproof coating as described in claim 1, characterized in that, In step c: the two-step polymerization process is as follows: 1) Under a nitrogen atmosphere, 70-80 wt% of the pre-emulsion from step b and 50 wt% of the initiator are placed in a reactor and reacted at 70-78°C for 1-2 hours to obtain oligomeric seeds; 2) the remaining pre-emulsion and initiator are then added, the temperature is raised to 80-85°C, and the temperature is maintained for 1-1.5 hours; 0.4-0.8 wt% of the 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 and stored; the initiator is ammonium persulfate, and the amount used is 0.8-1.5 wt% of the total monomer mass; the redox system is tert-butyl hydroperoxide and ascorbic acid in a mass ratio of 2:1, the branching degree of branched butyl acrylate is 3-5 branches, and the glass transition temperature is ≤-45°C.

5. The waterproof coating as described in claim 1, characterized in that, The bisfuran monomer is one of 2,2'-bisfuran-5,5'-dicarboxylic acid dimethyl ester, bisfuran malonate, bisfuran benzoate, and furoyl; the guanidine catalyst is 0.05-0.20 wt% tetramethylguanidine, and the free radical scavenger is 0.5-1.0 wt% diphenyliodonium salt, based on the mass of the bisfuran monomer.

6. The waterproof coating as described in claim 1, characterized in that, Fluorinated monomers of methacrylic acid are fluoroalkyl methacrylates containing 6 to 10 fluorine atoms in the molecule and fluoroalkyl carbon chains with a length of 4 to 8 carbon atoms, including perfluorobutyl methacrylate and octafluoropentyl methacrylate.

7. The waterproof coating as described in claim 1, characterized in that, The composite filler is obtained by ultrasonic dispersion of pickled fly ash cenospheres, silica aerogel and expanded perlite in a mass ratio of 5-7:2-4:1 in a 1.5-2.5 wt% silane coupling agent solution at 50-60°C; the mildew inhibitor is isothiazolinone and zinc pyridinethione, the defoamer is a polyether defoamer, the thickener is hydroxyethyl cellulose, the leveling agent is a polyurethane leveling agent, and the pH adjuster is triethanolamine.

8. The waterproof coating as described in claim 1, characterized in that, The preparation steps of the acid-washed fly ash celery beads are as follows: the fly ash celery beads are ultrasonically treated with a mixture of oxalic acid and hydrochloric acid, calcined at 700-800℃, and ball-milled until the D50 is 1-5μm and the specific surface area is ≥180m². 2 / g; the silica aerogel has a pore size of 20-50 nm, a porosity ≥90%, and a specific surface area ≥800 m² / g. 2 / g; the expanded perlite has a particle size of 30-60μm.

9. A method for preparing a weather-resistant, heat-insulating, and waterproof coating for exterior walls as described in any one of claims 1 to 8, characterized in that, The process includes the following steps: premixing the modified acrylate polymer emulsion with the composite filler to obtain a premixed slurry; Add to the curing system and click to cure. During this process, add the remaining composite filler in 2 to 3 batches. Then add the film-forming aid and cure under microwave-assisted UV curing. Add defoamer and leveling agent, and stir for 8-12 minutes; Add thickener and preservative and stir; adjust the pH to 7-8 with pH adjuster to obtain waterproof coating.

10. The preparation method according to claim 9, characterized in that, The click curing conditions are: reaction temperature of 75–85℃ and reaction time of 1.5–2 hours; the addition interval of the remaining composite filler is not less than 20 minutes; the UV curing conditions are: light intensity of 15–40 mW / cm². 2 The wavelength is 365-385nm, the curing time is 10-15min, and the microwave-assisted power is 200-300W.

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