An anti-salt and alkali seepage primer emulsion for exterior wall and a preparation method and application thereof

Abstract

This invention provides an anti-efflorescence alkaline primer emulsion for exterior walls, its preparation method, and its application. The raw materials of this primer emulsion, by weight, include: 0.7-1.6 parts emulsifier, 15-27 parts styrene, 10-25 parts acrylate monomers, 0.5-1.8 parts unsaturated carboxylic acids, 0.3-0.8 parts acrylamide monomers, 0.2-0.6 parts silane coupling agent, 0.3-0.5 parts persulfate initiator, 0.05-0.15 parts post-treatment agent, 0.05-0.16 parts environmentally friendly bactericide, 0.5-1.6 parts pH adjuster, 0.03-0.11 parts defoamer, and 41-54 parts water. This invention introduces a silicon-containing or rigid skeleton structure to form a dense cross-linked network, blocking the penetration of salt and alkali ions. This gives the emulsion excellent resistance to salt and alkali, water resistance, and adhesion. It can effectively prevent efflorescence, discoloration, chalking, and peeling of the wall surface, and extend the service life of the topcoat. It is especially suitable for exterior wall coating in high saline and alkaline environments such as coastal areas.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically relating to an anti-efflorescence alkaline primer emulsion for exterior walls, its preparation method, and its application. Background Technology

[0002] Coastal areas are highly corrosive environments. High rainfall, high humidity, and trace amounts of salt create a persistently damp environment for coatings, leading to prolonged condensation and creating conditions for moisture to penetrate the walls. This not only causes severe corrosion to building structures, reducing their durability, but also significantly damages and poses hidden dangers to the coatings. Given the harsh environment of coastal areas, even slight issues with the quality of coating materials and application will inevitably result in more serious problems such as salt precipitation, peeling, flaking, and fading. Repairing coating defects is extremely difficult, requiring substantial financial and human resources, disrupting the owner's normal use, and potentially causing economic disputes and blame-shifting among relevant parties, ultimately leading to project delays.

[0003] To prevent exterior wall coatings from fading, discoloration, peeling, and flaking after a period of exposure to wind, rain, and sun, a coat of alkali-resistant primer is typically applied before applying the main exterior wall coating to improve its durability and decorative effect. However, traditional primers lack sufficient salt and alkali resistance, creating a market demand for high-performance salt and alkali resistant primer emulsions to extend the lifespan of the substrate and reduce maintenance costs.

[0004] Based on the above, the inventors propose the following technical solutions. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide an anti-alkali primer emulsion for exterior walls, its preparation method and application.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: an anti-efflorescence alkaline primer emulsion for exterior walls, the raw materials comprising, by weight, the following: 0.7-1.6 parts emulsifier, 15-27 parts styrene, 10-25 parts acrylate monomers, 0.5-1.8 parts unsaturated carboxylic acids, 0.3-0.8 parts acrylamide monomers, 0.2-0.6 parts silane coupling agent, 0.3-0.5 parts persulfate initiator, 0.05-0.15 parts post-treatment agent, 0.05-0.16 parts environmentally friendly bactericide, 0.5-1.6 parts pH adjuster, 0.03-0.11 parts defoamer, and 41-54 parts water.

[0007] Furthermore, in the above-mentioned primer emulsion technical solution, the emulsifier is a combination of anionic emulsifiers, nonionic emulsifiers, and reactive emulsifiers used in any proportion; wherein the anionic emulsifier is one of alkyl polyoxyethylene ether monoester disodium succinate, sodium tridecyl alcohol polyoxyethylene ether sulfate, and sodium fatty alcohol polyoxyethylene ether sulfate; the nonionic emulsifier is one of polyethylene glycol fatty acid ester and fatty alcohol polyoxyethylene ether; and the reactive emulsifier is one of 3-allyloxy-1-hydroxy-1-propanesulfonate sodium salt and 2-acrylamide-2-methylpropanesulfonate sodium salt.

[0008] Furthermore, in the above-mentioned primer emulsion technical solution, the acrylate monomers are multiple substances selected from methyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, isooctyl acrylate, butyl acrylate, lauryl methacrylate, and ethyl acrylate, mixed in any proportion.

[0009] Furthermore, in the above-mentioned primer emulsion technical solution, the unsaturated carboxylic acid is a mixture of multiple types of acrylic acid, methacrylic acid, and itaconic acid in any proportion; the acrylamide monomer is a mixture of two types of acrylamide and N-hydroxymethylacrylamide in any proportion; and the silane coupling agent is a mixture of one or more types of vinyltriethoxysilane, vinyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane in any proportion.

[0010] Furthermore, in the above-mentioned primer emulsion technical solution, the persulfate initiator is one of potassium persulfate, ammonium persulfate, and sodium persulfate.

[0011] Furthermore, in the above-mentioned primer emulsion technical solution, the post-treatment agent is composed of an oxidant and a reducing agent, wherein the oxidant is tert-butyl hydrogen peroxide and the reducing agent is a deodorizing reducing agent.

[0012] Furthermore, in the above-mentioned primer emulsion technical solution, the pH adjuster is either liquid alkali or ammonia water; the bactericide is an isothiazolinone bactericide; and the defoamer is a polyether-modified silicone oil defoamer.

[0013] This invention also provides a method for preparing an anti-efflorescence alkaline primer emulsion for exterior walls, comprising the following steps: S1: While maintaining stirring, adding a portion of deionized water, a portion of emulsifier, a portion of styrene, and a portion of acrylamide monomers sequentially to an emulsification tank to prepare a stable pre-emulsion; S2: In a reaction vessel equipped with a stirring device, adding the remaining deionized water and a portion of emulsifier sequentially and heating to 60-65°C, adding 5%-10% of the total mass of the pre-emulsion to the reaction vessel and stirring for 5-15 minutes, then heating to 70-75°C, and adding an initiator solution prepared with 15%-30% of the total mass of persulfate initiator to carry out a seed reaction; S3: While maintaining stirring, adding the remaining styrene, the remaining acrylamide monomers, all acrylate monomers, unsaturated carboxylic acids, silane coupling agents, and the remaining portion of emulsifier to the remaining pre-emulsion in step S1. Pre-emulsion II was prepared by adding a pre-emulsion agent. In step S4, after the seed reaction had proceeded for 20-30 minutes, pre-emulsion II was added dropwise, along with the remaining initiator solution. The reaction temperature was controlled at 80-85℃. Pre-emulsion II was added dropwise for 2-3 hours, with the initiator solution addition laging behind pre-emulsion II by 15-30 minutes to reduce residual monomer content. The mixture was then kept at this temperature for 1-2 hours before cooling. In step S5, the temperature was lowered to 65-72℃ and kept at this temperature. Post-treatment agents were then added dropwise, controlling the dropwise rate, and completed within 15-30 minutes. The mixture was then kept at this temperature for another 30 minutes to eliminate residual monomer. After cooling to below 40℃, the remaining emulsifier was added and stirred evenly. The pH was adjusted to 7.0-8.0 using a pH adjuster. Then, a bactericide and defoamer were added. Finally, deionized water was added to adjust the solid content to 44.0-46.0%. The mixture was filtered to obtain the anti-efflorescence alkaline primer emulsion for exterior walls.

[0014] The primer emulsion prepared by the above method has a pH of 7.0-8.0, a solid content of 44.0-46.0%, a viscosity of 2000-5500 mPa·s at 25℃, a glass transition temperature (Tg) of 25-40℃, and a minimum film-forming temperature of 20-33℃. The prepared primer emulsion exhibits good water resistance, good resistance to alkali efflorescence, and good water permeability. When used in exterior wall primer coatings, it ensures a good sealing effect after the substrate dries, extending the substrate's service life and reducing maintenance costs.

[0015] Compared with existing primer emulsions, the present invention has the following advantages and effects:

[0016] 1. By using copolymerization processes (such as introducing silicon-containing or rigid framework structures), a dense cross-linked network is formed, which can block the penetration path of salt and alkali ions and prevent the substrate from pulverizing or peeling due to ion exchange or crystal expansion.

[0017] 2. The emulsion molecular chain has a low density of hydrophilic groups, which can reduce the swelling effect of water molecules on the paint film and prevent salt and alkali from migrating to the substrate surface with the water to form "alkali bloom".

[0018] 3. The active groups (such as hydroxyl and carboxyl groups) in the paint film can form chemical bonds with the ions on the substrate surface, stabilize the interface structure, and inhibit the damage of the coating by salts and alkalis through chemical replacement reaction.

[0019] 4. The surface of the emulsion particles has polar groups, which can enhance the adhesion to porous substrates (such as concrete, cement mortar, aerated blocks, etc.) through chemical bonding or physical adsorption. Even if there are a small amount of salt and alkali residues on the substrate surface, a strong coating can still be formed. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0021] This invention provides an exterior wall anti-efflorescence primer emulsion, the raw materials of which include the following components in parts by weight:

[0022] Emulsifier 0.7-1.6 parts;

[0023] 15-27 parts of styrene;

[0024] 10-25 parts of acrylate monomers;

[0025] 0.5-1.8 parts of unsaturated carboxylic acids;

[0026] Acrylamide monomers: 0.3-0.8 parts;

[0027] 0.2-0.6 parts of silane coupling agent;

[0028] 0.3-0.5 parts of persulfate initiator;

[0029] Post-treatment agent 0.05-0.15 parts;

[0030] 0.05-0.16 parts of environmentally friendly bactericide;

[0031] pH adjuster 0.5-1.6 parts;

[0032] Defoamer 0.03-0.11 parts;

[0033] Water 41-54 parts.

[0034] The present invention will be further described in detail below through examples.

[0035] Example 1

[0036] The anti-alkali efflorescence primer emulsion for exterior walls in this embodiment 1 is prepared using the following raw materials and dosages:

[0037] Pre-emulsion component 1: 200g deionized water, 6g disodium alkyl polyoxyethylene ether monoester succinate, 240.5g styrene, and 2g acrylamide.

[0038] The two components of the pre-emulsion are: 170.5g butyl acrylate, 10.5g isooctyl acrylate, 7g acrylic acid, 15g tert-butyl acrylate, 2g N-hydroxymethylacrylamide, 2.8g vinyltriethoxysilane, and 3g sodium 3-allyloxy-1-hydroxy-1-propanesulfonate.

[0039] Initial additions to the reactor: 280g of deionized water and 1.5g of disodium alkyl polyoxyethylene ether monoester succinate.

[0040] Initiator solution: 20g deionized water, 4g ammonium persulfate.

[0041] Post-treatment to eliminate residual monomers: 0.35g of tert-butyl hydrogen peroxide is mixed with 10g of deionized water; 0.37g of Solpregain EC15 deodorizing and reducing agent is mixed with 10g of deionized water.

[0042] Other excipients: 3g fatty alcohol polyoxyethylene ether, appropriate amount of ammonia (to adjust pH), 1g bactericide, 0.4g defoamer.

[0043] The preparation steps are as follows:

[0044] S1: While maintaining stirring, deionized water, disodium alkyl polyoxyethylene ether monoester succinate, styrene, and acrylamide are added sequentially to the emulsification tank to prepare a stable pre-emulsion.

[0045] S2: In a four-necked flask reactor equipped with a stirrer, deionized water and disodium alkyl polyoxyethylene ether monoester succinate were added in sequence and the temperature was raised to 64°C. 6% of the total mass of the pre-emulsion was added to the reactor and stirred for 10 minutes. The temperature was then raised to 75°C, and an initiator solution of 15% of the total mass of persulfate initiator was added to carry out the seed reaction.

[0046] S3: While maintaining stirring, add butyl acrylate, isooctyl acrylate, acrylic acid, tert-butyl acrylate, N-hydroxymethylacrylamide, vinyltriethoxysilane, and sodium 3-allyloxy-1-hydroxy-1-propanesulfonate to the remaining preemulsion one from step S1 to prepare preemulsion two.

[0047] S4: After the seeds have reacted for 20 minutes, start adding pre-emulsion solution II dropwise, while simultaneously adding the remaining initiator solution. Control the reaction temperature at 83-85℃. Add pre-emulsion solution II dropwise for about 3 hours, and then add the initiator solution 30 minutes later than pre-emulsion solution II to reduce the amount of residual monomer. Then keep warm for 2 hours and then cool down.

[0048] S5 is cooled to 70-72℃ and held at this temperature. The post-treatment agent (tert-butyl hydrogen peroxide aqueous solution and Solpregain EC15 aqueous solution) is then added dropwise, controlling the dropping rate and completing the addition within 15 minutes. The mixture is then held at this temperature for another 30 minutes to eliminate residual monomers. After cooling to below 40℃, fatty alcohol polyoxyethylene ether is added and stirred thoroughly. The pH is then adjusted to 7.5-8.0 using ammonia water. Bactericides and defoamers are then added, and finally, an appropriate amount of deionized water is added to adjust the solid content. The mixture is then filtered to obtain the target emulsion.

[0049] Example 2

[0050] The anti-alkali efflorescence primer emulsion for exterior walls in this embodiment is prepared using the following raw materials and dosages:

[0051] Pre-emulsion component 1: 210g deionized water, 5.5g sodium fatty alcohol polyoxyethylene ether sulfate, 100g styrene, 60g methyl methacrylate, 3g N-hydroxymethylacrylamide.

[0052] The two components of the pre-emulsion are: styrene 100g, acrylamide 1g, butyl acrylate 165g, lauryl methacrylate 10g, itaconic acid 3g, acrylic acid 5g, and vinyltrimethoxysilane 3.3g.

[0053] Initial additions to the reactor: 270g deionized water, 2.5g sodium fatty alcohol polyoxyethylene ether sulfate, and 2.5g sodium 3-allyloxy-1-hydroxy-1-propanesulfonate.

[0054] Initiator solution: 20g deionized water, 3.7g sodium persulfate.

[0055] Post-treatment to eliminate residual monomers: 0.4g of tert-butyl hydrogen peroxide is mixed with 10g of deionized water; 0.3g of Solpregain EC15 deodorizing and reducing agent is mixed with 10g of deionized water.

[0056] Other excipients: 2.5g polyethylene glycol fatty acid ester, appropriate amount of liquid alkali (to adjust pH), 1g bactericide, 0.47g defoamer.

[0057] The preparation steps are as follows:

[0058] S1: While maintaining stirring, deionized water, sodium fatty alcohol polyoxyethylene ether sulfate, a portion of styrene, methyl methacrylate, and N-hydroxymethylacrylamide are added sequentially to the emulsification tank to prepare a stable pre-emulsion.

[0059] S2: In a four-necked flask reactor equipped with a stirrer, deionized water, sodium fatty alcohol polyoxyethylene ether sulfate, and sodium 3-allyloxy-1-hydroxy-1-propanesulfonate were added sequentially and the temperature was raised to 65°C. 7% of the total mass of the pre-emulsion was added to the reactor and stirred for 10 minutes. The temperature was then raised to 72°C, and an initiator solution of 20% of the total mass of persulfate initiator was added to carry out the seed reaction.

[0060] S3: While maintaining stirring, add the remaining styrene, acrylamide, butyl acrylate, lauryl methacrylate, itaconic acid, acrylic acid, and vinyltrimethoxysilane to the remaining preemulsion one from step S1 to prepare preemulsion two.

[0061] S4: After the seeds have reacted for 25 minutes, start adding pre-emulsion solution II dropwise, while simultaneously adding the remaining initiator solution. Control the reaction temperature at 80-83℃. Add pre-emulsion solution II dropwise for about 2 hours, and then add the initiator solution 15 minutes later than pre-emulsion solution II to reduce the amount of residual monomer. Then keep warm for 2 hours and then cool down.

[0062] S5: Cool to 65-67℃ and maintain the temperature. Begin adding the post-treatment agent dropwise, controlling the dropping rate, and complete the addition within 30 minutes. Maintain the temperature for another 30 minutes to eliminate residual monomers. Cool to below 40℃, add polyethylene glycol fatty acid ester, stir evenly, adjust the pH to 7.5-8.0 using liquid alkali, then add bactericide and defoamer. Finally, add an appropriate amount of deionized water to adjust the solid content, filter, and the target emulsion is obtained.

[0063] Example 3

[0064] The anti-alkali efflorescence primer emulsion for exterior walls in this embodiment is prepared using the following raw materials and dosages:

[0065] Pre-emulsion component 1: 220g deionized water, 6.5g sodium tridecyl alcohol polyoxyethylene ether sulfate, 255g styrene, 7g acrylic acid.

[0066] The two components of the pre-emulsion are: 180g butyl acrylate, 3.5g N-hydroxymethylacrylamide, 3g sodium 2-acrylamide-2-methylpropanesulfonate, and 3g γ-glycidyl etheroxypropyltrimethoxysilane.

[0067] Initial additions to the reactor: 250g deionized water, 1.5g sodium tridecyl alcohol polyoxyethylene ether sulfate, and 3g fatty alcohol polyoxyethylene ether.

[0068] Initiator solution: 20g deionized water, 4.1g potassium persulfate.

[0069] Post-treatment to eliminate residual monomers: 0.42g of tert-butyl hydrogen peroxide is mixed with 10g of deionized water; 0.35g of Solpregain EC15 deodorizing and reducing agent is mixed with 10g of deionized water.

[0070] Other auxiliary materials: appropriate amount of ammonia (to adjust pH), 1g of bactericide, and 0.5g of defoamer.

[0071] The preparation steps are as follows:

[0072] S1: While maintaining stirring, deionized water, sodium tridecyl alcohol polyoxyethylene ether sulfate, styrene, and acrylic acid are added sequentially to the emulsification tank to prepare a stable pre-emulsion.

[0073] S2: In a four-necked flask reactor equipped with a stirrer, deionized water, sodium tridecyl alcohol polyoxyethylene ether sulfate, and fatty alcohol polyoxyethylene ether are added in sequence and the temperature is raised to 65°C. 8% of the total mass of the pre-emulsion is added to the reactor and stirred for 5 minutes. The temperature is then raised to 73°C, and an initiator solution of 20% of the total mass of persulfate initiator is added to carry out the seed reaction.

[0074] S3: While maintaining stirring, add butyl acrylate, N-hydroxymethylacrylamide, sodium 2-acrylamide-2-methylpropanesulfonate, and γ-glycidyl etheroxypropyltrimethoxysilane to the remaining preemulsion one from step S1 to prepare preemulsion two.

[0075] S4: After the seeds have reacted for 20 minutes, start adding pre-emulsion solution II dropwise, while simultaneously adding the remaining initiator solution. Control the reaction temperature at 82-84℃. Add pre-emulsion solution II dropwise for about 3 hours, and add the initiator solution 20 minutes later than pre-emulsion solution II to reduce the amount of residual monomer. Then keep warm for 1.5 hours and then cool down.

[0076] S5: Cool to 67-68℃ and maintain the temperature. Begin adding the post-treatment agent dropwise, controlling the dropping rate. Complete the addition in 20 minutes. Maintain the temperature for another 20 minutes to eliminate residual monomers. Cool to below 40℃, adjust the pH to 7.0-7.5 using ammonia, then add bactericide and defoamer. Finally, add an appropriate amount of deionized water to adjust the solid content. Filter the product to obtain the target emulsion.

[0077] Example 4

[0078] The anti-alkali efflorescence primer emulsion for exterior walls in this embodiment is prepared using the following raw materials and dosages:

[0079] Pre-emulsion component 1: 210g deionized water, 7g sodium fatty alcohol polyoxyethylene ether sulfate, 2g fatty alcohol polyoxyethylene ether, 250g styrene, 4g acrylamide.

[0080] The two components of the pre-emulsion are: 190g butyl acrylate, 8g acrylic acid, 3g sodium 2-acrylamide-2-methylpropanesulfonate, and 3g vinyltriethoxysilane.

[0081] Initial additions to the reactor: 280g of deionized water and 1g of sodium fatty alcohol polyoxyethylene ether sulfate.

[0082] Initiator solution: 20g deionized water, 3.6g potassium persulfate.

[0083] Post-treatment to eliminate residual monomers: 0.4g of tert-butyl hydrogen peroxide is mixed with 10g of deionized water; 0.34g of Solpregain EC15 deodorizing and reducing agent is mixed with 10g of deionized water.

[0084] Other excipients: appropriate amount of liquid alkali (to adjust pH), 1g bactericide, 0.3g defoamer.

[0085] The preparation steps are as follows:

[0086] S1: While maintaining stirring, deionized water, sodium fatty alcohol polyoxyethylene ether sulfate, fatty alcohol polyoxyethylene ether, styrene, and acrylamide are added sequentially to the emulsification tank to prepare a stable pre-emulsion.

[0087] S2: In a four-necked flask reactor equipped with a stirrer, deionized water and sodium fatty alcohol polyoxyethylene ether sulfate are added in sequence and the temperature is raised to 70°C. 10% of the total mass of the pre-emulsion is added to the reactor and stirred for 5 minutes. Then, an initiator solution of 25% of the total mass of persulfate initiator is added and the temperature is raised to 74°C to carry out the seed reaction.

[0088] S3: While maintaining stirring, add butyl acrylate, acrylic acid, sodium 2-acrylamide-2-methylpropanesulfonate, and vinyltriethoxysilane to the remaining preemulsion one from step S1 to prepare preemulsion two.

[0089] S4: After the seeds have reacted for 30 minutes, start adding pre-emulsion solution II dropwise, and at the same time add the remaining initiator solution. Control the reaction temperature at 84-85℃. Add pre-emulsion solution II dropwise for about 2.5 hours. Add the initiator solution 20 minutes later than pre-emulsion solution II to reduce the amount of residual monomer. Then keep warm for 1 hour and then cool down.

[0090] S5: Cool to 66-68℃ and maintain the temperature. Begin adding the post-treatment agent dropwise, controlling the dropping rate. Complete the addition in 20 minutes, then maintain the temperature for another 30 minutes to eliminate residual monomers. Cool to below 40℃, adjust the pH to 7.0-7.5 using liquid alkali, then add bactericide and defoamer. Finally, add an appropriate amount of deionized water to adjust the solid content. Filter the product to obtain the target emulsion.

[0091] Application test cases

[0092] To verify the performance of the primer emulsion of the present invention, performance tests were conducted on the emulsions prepared in Examples 1 to 4 and four commercially available comparative samples.

[0093] I. Basic Sample Information

[0094] Example 1: Solid content 45.2%, minimum film-forming temperature (MFFT) 20℃, glass transition temperature (Tg) 36℃, viscosity (25℃) 2780 mPa·s, pH value 7.7. Description: Example of the present invention.

[0095] Example 2: Solid content 44.8%, MFFT 21℃, Tg 20℃, viscosity 3450 mPa·s, pH value 7.6. Description: Example of the present invention.

[0096] Example 3: Solid content 44.7%, MFFT 26℃, Tg 35℃, viscosity 3640 mPa·s, pH value 7.3. Description: Example of the present invention.

[0097] Example 4: Solid content 45.1%, MFFT 27℃, Tg 35℃, viscosity 4120 mPa·s, pH value 7.2. Description: Example of the present invention.

[0098] Market Sample 1: Solid content 45.3%, MFFT 29℃, Tg 41℃, viscosity 2280 mPa·s, pH value 7.8. Description: General-purpose exterior wall primer from a mainstream domestic brand.

[0099] Market Sample 2: Solid content 44.8%, MFFT 27℃, Tg 34℃, viscosity 3850 mPa·s, pH value 7.9. Description: An economical acrylic primer from a foreign brand.

[0100] Market Sample 3: Solid content 45.6%, MFFT 26℃, Tg 33℃, viscosity 3720 mPa·s, pH value 7.3. Description: Domestic economical styrene-acrylic emulsion primer.

[0101] Market Sample 4: Solid content 44.5%, MFFT 23℃, Tg 36℃, viscosity 4060 mPa·s, pH value 7.5. Description: Domestic general-purpose exterior wall primer.

[0102] II. Testing Methods

[0103] 1. Alkali resistance test: The test was conducted according to GB / T 9265-2009 "Determination of alkali resistance of architectural coatings". The medium was saturated calcium hydroxide solution (pH≈12.5), and the conditions were immersion at 23±2°C for 48 hours. The bubbling, softening, peeling, and discoloration were observed.

[0104] 2. Accelerated Test for Resistance to Efflorescence: A custom method was used (referencing JG / T 210-2007 and engineering practice). A composite salt-alkali solution was prepared: 5% NaCl + 2% Ca(OH)2 + 1% Na2SO4, simulating a coastal / freeze-thaw saline-alkali environment. The salt-alkali solution was sprayed onto the back of the coating, while the front was exposed to a 40°C / 70% RH environment for 7 days (sprayed once daily, drying for 23 hours). Rating criteria: efflorescence area (white crystals / blemishes), adhesion change, and ΔE color difference.

[0105] III. Test Results

[0106] 1. Alkali resistance test results (48 h)

[0107] Example 1: No bubbling, no softening, no peeling, color change ΔE+0.4, conclusion: passed.

[0108] Example 2: No bubbling, no softening, no peeling, color change ΔE+0.3, conclusion: passed.

[0109] Example 3: No bubbling, no softening, no peeling, color change ΔE+0.2, conclusion: passed.

[0110] Example 4: No bubbling, no softening, no peeling, color change ΔE+0.5, conclusion: passed.

[0111] Market Sample 1: Microbubbles, slight softening, no peeling, discoloration ΔE+1.8, conclusion: partial failure.

[0112] Market Sample 2: Bubbling, obvious softening, local peeling, discoloration ΔE+2.5, Conclusion: Failed.

[0113] Market Sample 3: Severe blistering, softening and whitening, peeling at the edges, discoloration ΔE+3.2, conclusion: failure.

[0114] Market Sample 4: Severe blistering, softening and whitening, peeling at the edges, discoloration ΔE+3.3, Conclusion: Failure.

[0115] 2. Accelerated test results for resistance to efflorescence (7-day cycle)

[0116] Example 1: Alkali bloom area <5% (slight spots), very little salt crystallization, adhesion grade 0, ΔE increment +0.6, overall alkali bloom resistance grade 2 (slight).

[0117] Example 2: Alkali bloom area <3% (almost none), no salt crystallization, adhesion grade 1, ΔE increment +0.4, overall alkali bloom resistance grade 1 (no alkali bloom).

[0118] Example 3: No visible efflorescence area, no salt crystals, adhesion level 0, ΔE increment +0.3, overall efflorescence resistance level 1 (no efflorescence).

[0119] Example 4: Alkali bloom area <5%, small amount of salt crystallization, adhesion grade 1, ΔE increment +0.7, overall alkali bloom resistance grade 2 (slight).

[0120] Market Sample 1: Alkali bloom area 20-30% (white frost), obvious salt crystallization, adhesion level 2, ΔE increment +2.3, overall alkali bloom resistance level 4 (obvious).

[0121] Market Sample 2: Alkali efflorescence area >40% (whitening), severe salt crystallization, adhesion level 3, ΔE increment +3.0, overall alkali efflorescence resistance level 5 (severe alkali efflorescence + coating damage).

[0122] Market Sample 3: Extensive efflorescence with chalking, large amount of salt crystallization, adhesion level 3, ΔE increment +3.8, overall efflorescence resistance level 5 (severe efflorescence + coating damage).

[0123] Market Sample 4: Extensive efflorescence with chalking, large amount of salt crystallization, adhesion level 3, ΔE increment +3.7, overall efflorescence resistance level 5 (severe efflorescence + coating damage).

[0124] Anti-efflorescence rating description: Level 1 is no efflorescence, Level 2 is slight, Level 3 is moderate, Level 4 is obvious, and Level 5 is severe efflorescence + coating damage.

[0125] Through the above tests, the primer emulsions prepared in the four embodiments of the present invention all have excellent anti-alkali and alkali resistance properties, which are significantly better than those of commercially available comparative samples, and are suitable for exterior wall coating applications with high requirements for salt and alkali resistance.

[0126] Of course, the above description is only a specific embodiment of the present invention and is not intended to limit the scope of the present invention. All equivalent changes or modifications made to the structure, features and principles described in the claims of the present invention should be included in the scope of the claims of the present invention.

Claims

1. An anti-efflorescence alkaline primer emulsion for exterior walls, characterized in that, The raw materials of the primer emulsion include, by weight, 0.7-1.6 parts emulsifier, 15-27 parts styrene, 10-25 parts acrylate monomers, 0.5-1.8 parts unsaturated carboxylic acids, 0.3-0.8 parts acrylamide monomers, 0.2-0.6 parts silane coupling agent, 0.3-0.5 parts persulfate initiator, 0.05-0.15 parts post-treatment agent, 0.05-0.16 parts environmentally friendly bactericide, 0.5-1.6 parts pH adjuster, 0.03-0.11 parts defoamer, and 41-54 parts water.

2. The anti-efflorescence alkaline primer emulsion for exterior walls according to claim 1, characterized in that, The emulsifier is a combination of anionic emulsifiers, nonionic emulsifiers, and reactive emulsifiers used in any ratio; wherein the anionic emulsifier is one of alkyl polyoxyethylene ether monoester disodium succinate, sodium tridecyl alcohol polyoxyethylene ether sulfate, and sodium fatty alcohol polyoxyethylene ether sulfate; the nonionic emulsifier is one of polyethylene glycol fatty acid ester and fatty alcohol polyoxyethylene ether; and the reactive emulsifier is one of 3-allyloxy-1-hydroxy-1-propanesulfonate sodium salt and 2-acrylamide-2-methylpropanesulfonate sodium salt.

3. The anti-efflorescence alkaline primer emulsion for exterior walls according to claim 1, characterized in that, The acrylate monomers are a mixture of multiple species selected from methyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, isooctyl acrylate, butyl acrylate, lauryl methacrylate, and ethyl acrylate in any proportion.

4. The anti-efflorescence alkaline primer emulsion for exterior walls according to claim 1, characterized in that... The unsaturated carboxylic acid is a mixture of acrylic acid, methacrylic acid, and itaconic acid in any proportion; the acrylamide monomer is a mixture of acrylamide and N-hydroxymethylacrylamide in any proportion; the silane coupling agent is a mixture of one or more of vinyltriethoxysilane, vinyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane in any proportion.

5. The anti-efflorescence alkaline primer emulsion for exterior walls according to claim 1, characterized in that, The persulfate initiator is one of potassium persulfate, ammonium persulfate, or sodium persulfate.

6. The anti-efflorescence alkaline primer emulsion for exterior walls according to claim 1, characterized in that, The post-treatment agent consists of an oxidant and a reducing agent, wherein the oxidant is tert-butyl hydrogen peroxide and the reducing agent is a deodorizing reducing agent.

7. The anti-efflorescence alkaline primer emulsion for exterior walls according to claim 1, characterized in that, The pH adjuster is either liquid alkali or ammonia water; the bactericide is an isothiazolinone bactericide; and the defoamer is a polyether-modified silicone oil defoamer.

8. A method for preparing an anti-efflorescence alkaline primer emulsion for exterior walls, characterized in that, The method for preparing the primer emulsion as described in any one of claims 1-7 is characterized by comprising the following steps: S1: While maintaining stirring, add a portion of deionized water, a portion of emulsifier, a portion of styrene, and a portion of acrylamide monomers sequentially to the emulsion tank to prepare a stable pre-emulsion. S2: In a reactor equipped with a stirrer, add the remaining deionized water and part of the emulsifier in sequence and heat to 60-65℃. Add 5%-10% of the total mass of the pre-emulsion to the reactor and stir for 5-15 minutes. Then heat to 70-75℃ and add an initiator solution prepared by adding 15%-30% of the total mass of the persulfate initiator to carry out seed reaction. S3 While maintaining stirring, add the remaining styrene, the remaining acrylamide monomers, all acrylate monomers, unsaturated carboxylic acid, silane coupling agent and the remaining part of the emulsifier to the remaining preemulsion one from step S1 to prepare preemulsion two. After the seeds have reacted for 20-30 minutes, start adding pre-emulsion solution II dropwise, while simultaneously adding the remaining initiator solution. Control the reaction temperature at 80-85℃. Add pre-emulsion solution II dropwise for 2-3 hours, and delay the addition of the initiator solution by 15-30 minutes compared to pre-emulsion solution II to reduce the amount of residual monomers. Then keep warm for 1-2 hours before cooling down. S5 is cooled to 65-72℃ and kept at that temperature. The post-treatment agent is then added dropwise, with the dropwise rate controlled. The addition is completed in 15-30 minutes. The temperature is then kept at that temperature for another 30 minutes to eliminate residual monomers. The temperature is then cooled to below 40℃. The remaining emulsifier is added and stirred evenly. The pH is then adjusted to 7.0-8.0 using a pH adjuster. The bactericide and defoamer are then added. Finally, deionized water is added to adjust the solid content to 44.0-46.0%. The mixture is then filtered and discharged to obtain the anti-efflorescence alkaline primer emulsion for exterior walls.

9. The method for preparing an anti-efflorescence alkaline primer emulsion for exterior walls according to claim 8, characterized in that: The prepared primer emulsion has a pH of 7.0-8.0, a solid content of 44.0-46.0%, a viscosity of 2000-5500 mPa·s at 25℃, a glass transition temperature (Tg) of 25-40℃, and a minimum film-forming temperature of 20-33℃.

10. The method for preparing an anti-efflorescence alkaline primer emulsion for exterior walls according to claim 8, characterized in that: The prepared emulsion is used in exterior wall primer coatings.