Low-voc environment-friendly outer wall anti-salt and alkali primer emulsion and preparation method and application thereof

Abstract

This invention provides a low-VOC, environmentally friendly exterior wall anti-efflorescence alkaline primer emulsion, its preparation method, and its application. The raw materials of this primer emulsion, by weight, include: 0.8-1.7 parts of biodegradable emulsifier, 0.2-1.0 parts of reactive emulsifier, 13-25 parts of styrene, 13-23 parts of acrylate monomers, 0.6-1.6 parts of unsaturated carboxylic acids, 0.3-0.7 parts of acrylamide monomers, 0.25-0.5 parts of silane coupling agent, 0.3-0.5 parts of persulfate initiator, 0.06-0.09 parts of post-treatment agent, 0.6-1.6 parts of pH adjuster, 0.03-0.12 parts of plant-based defoamer, and 42-54 parts of deionized water. This invention employs a combination of biodegradable and reactive emulsifiers, along with seed emulsion polymerization and flash stripping post-treatment processes, to achieve an emulsion VOC content ≤10g / L, meeting the GB 18582-2020 standard, and exhibiting excellent resistance to salt efflorescence, sealing properties, and water resistance.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically relating to a low-VOC environmentally friendly exterior wall anti-alkali primer emulsion, its preparation method, and its application. Background Technology

[0002] With increasing environmental awareness, the environmental requirements for architectural coatings are becoming increasingly stringent. VOCs (volatile organic compounds), as the main pollutants in coatings, are subject to strict emission limits. While existing exterior wall anti-efflorescence primer emulsions can address the issue of efflorescence to some extent, most do not adequately consider VOC control. Some products exceed environmental standards for VOC content, releasing harmful substances during construction and use, polluting indoor and outdoor air, and endangering human health. Traditional primer emulsions are no longer sufficient to meet the needs of densely populated areas with high environmental requirements, such as schools, hospitals, and residences.

[0003] Meanwhile, some of the emulsifiers, defoamers, and other additives used in traditional primer emulsions have poor biodegradability and are prone to accumulate in the environment, posing a potential threat to the ecological environment. Therefore, developing an exterior wall primer emulsion that combines excellent resistance to efflorescence and low VOC environmental performance has become an important demand in the current coatings industry.

[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 a low-VOC environmentally friendly exterior wall anti-alkali primer emulsion and its preparation method.

[0006] To solve the above-mentioned technical problems, the low-VOC environmentally friendly exterior wall anti-efflorescence alkaline primer emulsion of the present invention adopts the following technical solution: The raw materials for preparing the primer emulsion include the following components in parts by weight: 0.8-1.7 parts of biodegradable emulsifier; 0.2-1.0 parts of reactive emulsifier; 13-25 parts of styrene; 13-23 parts of acrylate monomers; 0.6-1.6 parts of unsaturated carboxylic acids; 0.3-0.7 parts of acrylamide monomers; 0.25-0.5 parts of silane coupling agent; 0.3-0.5 parts of persulfate initiator; 0.06-0.09 parts of post-treatment agent; 0.6-1.6 parts of pH adjuster; 0.03-0.12 parts of plant-based defoamer; and 42-54 parts of deionized water.

[0007] Furthermore, in the above-mentioned primer emulsion technical solution, the raw materials also include the following components in parts by weight: 0.06 to 0.16 parts of environmentally friendly bactericide; the environmentally friendly bactericide is an isothiazolinone bactericide.

[0008] Furthermore, in the above-mentioned primer emulsion technical solution, the biodegradable emulsifier is one or a combination of two or more of ethoxylated alcohol ammonium sulfate, sodium decyl diphenyl ether disulfonate, polyglycerol fatty acid ester, and sucrose fatty acid ester.

[0009] Furthermore, in the above-mentioned primer emulsion technical solution, the reactive emulsifier is one of sodium 3-allyloxy-1-hydroxy-1-propanesulfonate or sodium 2-acrylamide-2-methylpropanesulfonate.

[0010] Furthermore, in the above-mentioned primer emulsion technical solution, the acrylate monomers are a combination of two or more of methyl methacrylate, methyl acrylate, tert-butyl acrylate, tert-butyl methacrylate, isooctyl acrylate, butyl acrylate, lauryl methacrylate, and ethyl acrylate; the acrylamide monomers are a combination of one or more of acrylamide, N-hydroxymethylacrylamide, and diacetone acrylamide.

[0011] Furthermore, in the above-mentioned primer emulsion technical solution, the silane coupling agent is one or a combination of two or more of vinyltriethoxysilane, vinyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane; the persulfate initiator is one of potassium persulfate, ammonium persulfate, or sodium persulfate; the pH adjuster is liquid alkali or 2-amino-2-methyl-1-propanol; and the plant-based defoamer is a turpentine derivative defoamer.

[0012] Furthermore, in the above-mentioned primer emulsion technical solution, the post-treatment agent is composed of an oxidant and a reducing agent, and the oxidant is tert-butyl hydrogen peroxide.

[0013] The preparation method of the primer emulsion of the present invention adopts the following technical solution: The preparation method includes the following steps: S1 Under the condition of stirring, a portion of deionized water, a portion of biodegradable emulsifier, a portion of styrene, a portion of acrylate monomers and a portion of acrylamide monomers are added sequentially to an emulsification tank to prepare a stable pre-emulsion one; S2 In a reaction vessel equipped with a stirring device, the remaining deionized water, the remaining biodegradable emulsifier and a portion of reactive emulsifier are added sequentially and the temperature is raised to 60-65℃. 5%-10% of the total mass of the pre-emulsion one is added to the reaction vessel and stirred for 5-15 minutes, then the temperature is raised to 70-75℃, and an initiator solution prepared by adding 15%-30% of the total mass of persulfate initiator is added to carry out a seed reaction; S3 Under the condition of stirring, the remaining styrene, the remaining acrylate monomers, the unsaturated carboxylic acid, the remaining acrylamide monomers, the remaining reactive emulsifier and the silane coupling agent are added to the remaining pre-emulsion one in step S1 to prepare a pre-emulsion one. S4. After the above seed reaction has proceeded for 20-30 minutes, begin adding pre-emulsion II dropwise, simultaneously adding the initiator solution prepared from the remaining persulfate initiator. Control the reaction temperature at 80-85℃. Add pre-emulsion II dropwise for 2-3 hours, with the initiator solution addition ending 15-30 minutes after pre-emulsion II to reduce residual monomer content. S5. Then maintain the temperature for 1-2 hours, followed by flash evaporation and stripping to complete the degassing treatment. The flash evaporation conditions are: [Insert conditions here]. The material is steamed for 1.5-3 hours under vacuum of -0.05 to -0.095 MPa at a temperature of 60-80°C. During the stripping process, a post-treatment agent is added dropwise, with the dropping rate controlled and the dropping time being 15-30 minutes. After cooling to below 40°C, the pH is adjusted to 7.0-8.0 using a pH adjuster. Then, an environmentally friendly bactericide and a plant-based defoamer are added. Finally, deionized water is added to adjust the solid content, and the material is filtered out to obtain the low-VOC environmentally friendly exterior wall anti-efflorescence alkaline primer emulsion.

[0014] Furthermore, in the above preparation method, in step S6, before adjusting the pH, the remaining biodegradable emulsifier can be added to optimize the emulsion stability.

[0015] The present invention provides a low-VOC environmentally friendly anti-alkali primer emulsion for exterior walls, which is used as a primer coating for building exterior walls. The low-VOC environmentally friendly anti-alkali 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℃, a minimum film-forming temperature of 20-33℃, and a VOC content ≤ 10 g / L.

[0016] Compared with existing primer emulsions, the present invention has the following advantages and effects:

[0017] 1. Excellent environmental performance: Biodegradable emulsifiers and plant-based defoamers are selected to replace traditional non-environmentally friendly additives. By optimizing the monomer ratio, the amount of volatile monomers is reduced, so that the VOC content of the emulsion is ≤10 g / L, which meets the GB 18582-2020 standard "Limits of Hazardous Substances in Wall Coatings for Buildings". The release of harmful substances is low during construction and use, which is friendly to the environment and human health.

[0018] 2. Stable core performance: While upgrading environmental protection, by reasonably controlling the ratio of hard monomers and soft monomers and the amount of silane coupling agent, the performance parameters such as the glass transition temperature and minimum film-forming temperature of the emulsion are comparable to those of traditional anti-alkali primer emulsions. It can still form a dense cross-linked network, block the penetration of salt and alkali ions, effectively prevent efflorescence, powdering and peeling of the wall surface, and maintain excellent adhesion and substrate permeability to concrete substrates.

[0019] 3. Eco-friendly raw materials: The environmentally friendly bactericides used are isothiazolinones, which are highly effective and low in toxicity. Furthermore, the biodegradable emulsifiers are easily decomposed in the natural environment and will not cause ecological accumulation, further reducing potential harm to the environment.

[0020] The primer emulsion of this invention uses environmentally friendly raw materials such as biodegradable emulsifiers and plant-based defoamers, and optimizes the formula composition. While ensuring that the core properties such as resistance to salt efflorescence, sealing, and water resistance are not reduced, the VOC content is ≤ 10 g / L, which meets the latest environmental protection standards. Moreover, the raw materials have good biodegradability and are environmentally friendly, which can meet the needs of various exterior wall coating scenarios with high environmental protection requirements. Detailed Implementation

[0021] 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.

[0022] This invention provides a low-VOC, environmentally friendly exterior wall anti-efflorescence primer emulsion, the raw materials of which include the following components in parts by weight:

[0023] 0.8 to 1.7 parts of biodegradable emulsifier;

[0024] 0.2 to 1.0 parts of reactive emulsifier;

[0025] 13 to 25 parts of styrene;

[0026] 13 to 23 parts of acrylate monomers;

[0027] Unsaturated carboxylic acids, 0.6 to 1.6 parts;

[0028] Acrylamide monomers: 0.3 to 0.7 parts;

[0029] 0.25 to 0.5 parts of silane coupling agent;

[0030] Persulfate initiator: 0.3–0.5 parts;

[0031] Post-treatment agent 0.06 to 0.09 parts;

[0032] pH adjuster 0.6 to 1.6 parts;

[0033] Environmentally friendly bactericide, 0.06 to 0.16 parts;

[0034] 0.03 to 0.12 parts of plant-based defoamer;

[0035] 42 to 54 parts of deionized water.

[0036] The biodegradable emulsifier is one or a combination of two or more of ethoxylated alcohol ammonium sulfate, sodium decyl diphenyl ether disulfonate, polyglycerol fatty acid ester, and sucrose fatty acid ester; the reactive emulsifier is one of sodium 3-allyloxy-1-hydroxy-1-propanesulfonate and sodium 2-acrylamide-2-methylpropanesulfonate.

[0037] The acrylate monomers are combinations of two or more selected from methyl methacrylate, methyl acrylate, tert-butyl acrylate, tert-butyl methacrylate, isooctyl acrylate, butyl acrylate, lauryl methacrylate, and ethyl acrylate; the unsaturated carboxylic acids are combinations of one or more selected from acrylic acid, methacrylic acid, and itaconic acid; the acrylamide monomers are combinations of one or more selected from acrylamide, N-hydroxymethylacrylamide, and diacetone acrylamide; and the silane coupling agent is combinations of one or more selected from vinyltriethoxysilane, vinyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane.

[0038] The persulfate initiator is one of potassium persulfate, ammonium persulfate, or sodium persulfate; the post-treatment agent consists of an oxidant and a reducing agent, the oxidant being tert-butyl hydroperoxide and the reducing agent being Solpregain EC15 deodorizing reducing agent; the pH adjuster is liquid alkali or 2-amino-2-methyl-1-propanol; the environmentally friendly bactericide is an isothiazolinone bactericide; and the plant-based defoamer is a turpentine oil derivative defoamer.

[0039] The following are specific embodiments of the present invention and related test descriptions.

[0040] Example 1

[0041] The low-VOC environmentally friendly exterior wall anti-alkali primer emulsion in Example 1 is prepared using the following raw materials and dosages:

[0042] The first component of the pre-emulsion consists of: 220g deionized water, 6.5g ethoxylated alcohol ammonium sulfate, 215g styrene, and 2.2g acrylamide.

[0043] The two components of the pre-emulsion are: 168g butyl acrylate, 12g methyl acrylate, 7.5g acrylic acid, 12g tert-butyl acrylate, 2.5g N-hydroxymethylacrylamide, and 3.0g vinyltriethoxysilane.

[0044] Initial additions to the reactor: 260g deionized water, 2g ethoxylated alcohol ammonium sulfate, and 2g sodium 3-allyloxy-1-hydroxy-1-propanesulfonate.

[0045] Initiator solution: 22g deionized water, 4.2g potassium persulfate.

[0046] Post-treatment to eliminate residual monomers: 0.39g of tert-butyl hydrogen peroxide was mixed with 11g of deionized water; 0.32g of Solpregain EC15 deodorizing and reducing agent was mixed with 11g of deionized water.

[0047] Other excipients: 3.2g polyglycerol fatty acid ester, 8.0g liquid alkali, 1.1g isothiazolinone bactericide, and 0.9g turpentine oil derivative defoamer.

[0048] The preparation steps are as follows:

[0049] S1. While stirring, deionized water, ethoxylated alcohol ammonium sulfate, a portion of styrene, and acrylamide are added sequentially to the emulsification tank to prepare a stable pre-emulsion.

[0050] S2 In a four-necked flask reactor equipped with a stirrer, deionized water, ethoxylated alcohol ammonium sulfate, and sodium 3-allyloxy-1-hydroxy-1-propanesulfonate were added sequentially and the temperature was raised to 63°C. 6% of the above pre-emulsion was added to the reactor and stirred for 15 minutes, then the temperature was raised to 73°C. Finally, 15% potassium persulfate aqueous solution was added to carry out the seed reaction.

[0051] S3 adds butyl acrylate, methyl acrylate, acrylic acid, tert-butyl acrylate, N-hydroxymethylacrylamide, and vinyltriethoxysilane to preemulsion one while stirring to prepare preemulsion two.

[0052] S4 After the above seeds have reacted for 20 minutes, start adding pre-emulsion II dropwise, and at the same time add the remaining potassium persulfate aqueous solution. Control the reaction temperature at 83-85℃. Add monomer pre-emulsion II dropwise for about 3 hours, and add potassium persulfate aqueous solution 30 minutes later than pre-emulsion II to reduce the amount of residual monomer.

[0053] S5 was then kept at a constant temperature for 1.5 hours, followed by flash evaporation and stripping to complete the degassing process. The flash evaporation process involved feeding for 2 hours, with a vacuum of -0.05 to -0.08 MPa and a temperature of 70 to 80°C. During the stripping process, tert-butyl hydrogen peroxide aqueous solution and Solpregain EC15 deodorizing reducing agent aqueous solution were added dropwise, with the dropping rate controlled and the addition completed in 15 minutes.

[0054] S6 is cooled to below 40°C, polyglycerol fatty acid esters are added (different types of emulsifiers are added to optimize stability), and after stirring evenly, the pH is adjusted to 7.0-7.5 using liquid alkali. Then, isothiazolinone bactericides and turpentine derivative defoamers are added. Finally, an appropriate amount of deionized water is added to adjust the solid content, and the product is filtered to obtain the target emulsion.

[0055] Example 2

[0056] The low-VOC environmentally friendly exterior wall anti-alkali primer emulsion in Example 2 is prepared using the following raw materials and dosages:

[0057] The first component of the pre-emulsion consists of: 200g deionized water, 5.5g sodium decyl diphenyl ether disulfonate, 100g styrene, 60g methyl methacrylate, and 3.2g N-hydroxymethylacrylamide.

[0058] The two components of the pre-emulsion are: styrene 105g, acrylamide 1.1g, butyl acrylate 160g, lauryl methacrylate 10g, itaconic acid 3.2g, acrylic acid 5.2g, vinyltrimethoxysilane 3.5g, and sodium 3-allyloxy-1-hydroxy-1-propanesulfonate 3g.

[0059] Initial additions to the reactor: 260g deionized water, 2g sodium decyl diphenyl ether disulfonate, and 4g sucrose fatty acid ester.

[0060] Initiator solution: 21g deionized water, 3.9g sodium persulfate.

[0061] Post-treatment to eliminate residual monomers: 0.42g of tert-butyl hydrogen peroxide is mixed with 10g of deionized water; 0.32g of Solpregain EC15 deodorizing and reducing agent is mixed with 10g of deionized water.

[0062] Other excipients: 10.0g of 2-amino-2-methyl-1-propanol, 1.0g of isothiazolinone bactericide, and 0.5g of turpentine oil derivative defoamer.

[0063] The preparation steps are as follows:

[0064] S1. While stirring, deionized water, sodium decyl diphenyl ether disulfonate, a portion of styrene, methyl methacrylate, and N-hydroxymethyl acrylamide are added sequentially to the emulsion tank to prepare a stable pre-emulsion.

[0065] S2. Deionized water and sucrose fatty acid ester were added sequentially to a four-necked flask reactor equipped with a stirrer and the temperature was raised to 65°C. 7% of the above pre-emulsion was added to the reactor and stirred for 10 minutes. The temperature was then raised to 70°C, and 20% sodium persulfate aqueous solution was added to carry out seed reaction.

[0066] S3 While maintaining stirring, add the remaining styrene, acrylamide, butyl acrylate, lauryl methacrylate, itaconic acid, acrylic acid, vinyltrimethoxysilane and sodium 3-allyloxy-1-hydroxy-1-propanesulfonate to preemulsion one to prepare preemulsion two.

[0067] S4 After the above seeds have reacted for 25 minutes, start adding pre-emulsion II dropwise, and simultaneously add sodium persulfate aqueous solution. Control the reaction temperature at 81-84℃. Add monomer pre-emulsion II dropwise for about 2 hours, and add sodium persulfate aqueous solution 15 minutes later than pre-emulsion II to reduce the amount of residual monomer.

[0068] S5 was then kept at a constant temperature for 2 hours, followed by flash evaporation and stripping to complete the degassing process. The flash evaporation process involved feeding for 1.5 hours at a vacuum of -0.05 to -0.08 MPa and a temperature of 70 to 75°C. During stripping, tert-butyl hydrogen peroxide aqueous solution and Solpregain EC15 deodorizing reducing agent aqueous solution were added dropwise, with the addition rate controlled, and the process completed in 25 minutes.

[0069] S6 is cooled to below 40°C, and the pH is adjusted to 7.0-7.5 using 2-amino-2-methyl-1-propanol. Then, isothiazolinone bactericide and turpentine derivative defoamer are added. Finally, an appropriate amount of deionized water is added to adjust the solid content, and the product is filtered to obtain the target emulsion.

[0070] Example 3

[0071] The low-VOC environmentally friendly exterior wall anti-alkali primer emulsion in this embodiment three is prepared using the following raw materials and dosages:

[0072] Pre-emulsion component 1: 210g deionized water, 6g sodium decyl diphenyl ether disulfonate, 130g styrene, 2g diacetone acrylamide, 3.2g N-hydroxymethyl acrylamide.

[0073] The two components of the pre-emulsion are: styrene 120g, acrylamide 1.5g, butyl acrylate 165g, isooctyl acrylate 20g, itaconic acid 3g, acrylic acid 5g, and γ-glycidoxypropyltrimethoxysilane 3.5g.

[0074] Initial additions to the reactor: 260g deionized water, 2.6g sodium decyl diphenyl ether disulfonate, and 2.6g sodium 2-acrylamide-2-methylpropanesulfonate.

[0075] Initiator solution: 25g deionized water, 3.9g ammonium persulfate.

[0076] Post-treatment to eliminate residual monomers: 0.42g of tert-butyl hydrogen peroxide is mixed with 10g of deionized water; 0.32g of Solpregain EC15 deodorizing and reducing agent is mixed with 10g of deionized water.

[0077] Other excipients: 4g sucrose fatty acid ester, 9.0g liquid alkali, 1.0g isothiazolinone bactericide, and 0.8g turpentine oil derivative defoamer.

[0078] The preparation steps are as follows:

[0079] S1. While stirring, deionized water, sodium decyl diphenyl ether disulfonate, a portion of styrene, diacetone acrylamide, and N-hydroxymethyl acrylamide are added sequentially to the emulsion tank to prepare a stable pre-emulsion.

[0080] S2 In a four-necked flask reactor equipped with a stirrer, deionized water, sodium decyl diphenyl ether disulfonate and sodium 2-acrylamide-2-methylpropanesulfonate were added in sequence and the temperature was raised to 66°C. 9% of the above pre-emulsion was added to the reactor and stirred for 10 min. The temperature was then raised to 72°C and 20% ammonium persulfate aqueous solution was added to carry out seed reaction.

[0081] S3 While maintaining stirring, add the remaining styrene, remaining acrylamide, butyl acrylate, isooctyl acrylate, itaconic acid, acrylic acid, and γ-glycidyl etheroxypropyltrimethoxysilane to preemulsion one to prepare preemulsion two.

[0082] S4 After the above seeds have reacted for 30 minutes, start adding pre-emulsion II dropwise, and at the same time add the remaining ammonium persulfate aqueous solution. Control the reaction temperature at 80-84℃. Add monomer pre-emulsion II dropwise for about 2.5 hours, and add ammonium persulfate aqueous solution 15 minutes later than pre-emulsion II to reduce the amount of residual monomer.

[0083] S5 was then kept at this temperature for 2 hours before being cooled down, followed by flash evaporation and stripping to complete the degassing process. The flash evaporation process involved feeding for 1.5 hours at a vacuum of -0.06 to -0.08 MPa and a temperature of 65 to 75°C. During stripping, tert-butyl hydrogen peroxide aqueous solution and Solpregain EC15 deodorizing reducing agent aqueous solution were added dropwise, with the addition rate controlled, and the process was completed in 20 minutes.

[0084] S6 is cooled to below 40℃, and the pH is adjusted to 7.5-8.0 using liquid alkali. Then, isothiazolinone bactericide and turpentine derivative defoamer are added. Finally, an appropriate amount of deionized water is added to adjust the solid content, and the product is filtered out to obtain the target emulsion.

[0085] Application test cases

[0086] To verify the performance of the primer emulsion of the present invention, performance tests were conducted on the emulsions prepared in Examples 1 to 3 and three commercially available comparative samples, and the results are as follows.

[0087] I. Basic Sample Information

[0088] Example 1: Solid content 45.2%, minimum film-forming temperature (MFFT) 20℃, glass transition temperature (Tg) 34℃, viscosity (25℃) 2850 mPa·s, pH value 7.8. Description: Example of the present invention.

[0089] Example 2: Solid content 45.6%, MFFT 24℃, Tg 33℃, viscosity 2450 mPa·s, pH value 7.6. Description: Example of the present invention.

[0090] Example 3: Solid content 44.9%, MFFT 26℃, Tg 35℃, viscosity 3530 mPa·s, pH value 7.3. Description: Example of the present invention.

[0091] Market Sample 1: Solid content 45.1%, MFFT 27℃, Tg 37℃, viscosity 2570 mPa·s, pH value 7.7. Description: General-purpose primer emulsion from a mainstream domestic brand.

[0092] Market Sample 2: Solid content 45.3%, MFFT 25℃, Tg 35℃, viscosity 2970 mPa·s, pH value 7.7, description: foreign-made economical primer emulsion.

[0093] Market Sample 3: Solid content 44.7%, MFFT 27℃, Tg 37℃, viscosity 2760 mPa·s, pH value 7.7, description: low-priced primer emulsion.

[0094] II. Environmental performance (VOCs and harmful substances)

[0095] Example 1: VOC content 9.7 g / L, formaldehyde <1 mg / kg, APEO not detected, meets GB / T 38597-2020 standard.

[0096] Example 2: VOC content 9.5 g / L, formaldehyde <1 mg / kg, APEO not detected, meets GB / T 38597-2020 standard.

[0097] Example 3: VOC content 9.8 g / L, formaldehyde <1 mg / kg, APEO not detected, meets GB / T 38597-2020 standard.

[0098] Market Sample 1: VOC content 48 g / L, formaldehyde 12 mg / kg, APEO not detected, close to the standard limit of 50 g / L, borderline.

[0099] Market Sample 2: VOC content 63 g / L, formaldehyde 25 mg / kg, APEO detected (trace amount), does not meet the standard (VOC exceeds the standard).

[0100] Market Sample 3: VOC content 65 g / L, formaldehyde 35 mg / kg, APEO detected, does not meet the standard.

[0101] III. Results of Accelerated Test for Resistance to Paleosis (7-day Cycle)

[0102] The test uses a 7-day cyclic accelerated efflorescence method to evaluate the efflorescence area, salt crystallization degree, adhesion (cross-cut test), and color difference ΔE increment of each sample coating, and gives a comprehensive rating (level 1 is no efflorescence, level 5 is severe efflorescence + coating damage).

[0103] Example 1: Alkali bloom area <5% (slight spots), very little salt crystallization, adhesion grade 0, ΔE increment +0.7, overall alkali bloom resistance grade 2 (slight).

[0104] 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).

[0105] Example 3: No visible efflorescence area, no salt crystals, adhesion level 1, ΔE increment +0.4, overall efflorescence resistance level 1 (no efflorescence).

[0106] 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).

[0107] Market Sample 2: Alkali efflorescence area >40% (whitening), severe salt crystallization, adhesion level 3, ΔE increment +3.1, overall alkali efflorescence resistance level 5 (severe alkali efflorescence + coating damage).

[0108] Market Sample 3: Extensive efflorescence accompanied by chalking, large amount of salt crystallization, adhesion level 3, ΔE increment +3.5, overall efflorescence resistance level 5 (severe efflorescence + coating damage).

[0109] The primer emulsion prepared in this embodiment of the invention has low VOC environmental friendliness and excellent resistance to salt efflorescence, which is significantly better than commercially available comparative samples. It is suitable for exterior wall coating applications with high requirements for environmental protection and weather resistance.

[0110] 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. A low-VOC environmentally friendly exterior wall anti-efflorescence primer emulsion, characterized in that, The raw materials for preparing the primer emulsion include the following components in parts by weight: 0.8 to 1.7 parts of biodegradable emulsifier; 0.2 to 1.0 parts of reactive emulsifier; 13 to 25 parts of styrene; 13 to 23 parts of acrylate monomers; Unsaturated carboxylic acids, 0.6 to 1.6 parts; Acrylamide monomers: 0.3 to 0.7 parts; 0.25 to 0.5 parts of silane coupling agent; Persulfate initiator: 0.3–0.5 parts; Post-treatment agent 0.06 to 0.09 parts; pH adjuster 0.6 to 1.6 parts; 0.03 to 0.12 parts of plant-based defoamer; 42 to 54 parts of deionized water.

2. The low-VOC environmentally friendly exterior wall anti-efflorescence alkaline primer emulsion according to claim 1, characterized in that, The raw materials also include the following components in parts by weight: 0.06 to 0.16 parts of an environmentally friendly bactericide; the environmentally friendly bactericide is an isothiazolinone bactericide.

3. The low-VOC environmentally friendly exterior wall anti-efflorescence primer emulsion according to claim 1, characterized in that, The biodegradable emulsifier is one or a combination of two or more of the following: ethoxylated alcohol ammonium sulfate, sodium decyl diphenyl ether disulfonate, polyglycerol fatty acid ester, and sucrose fatty acid ester.

4. The low-VOC environmentally friendly exterior wall anti-efflorescence alkaline primer emulsion according to claim 1, characterized in that, The reactive emulsifier is one of sodium 3-allyloxy-1-hydroxy-1-propanesulfonate or sodium 2-acrylamide-2-methylpropanesulfonate.

5. The low-VOC environmentally friendly exterior wall anti-efflorescence primer emulsion according to claim 1, characterized in that, The acrylate monomers are combinations of two or more of the following: methyl methacrylate, methyl acrylate, tert-butyl acrylate, tert-butyl methacrylate, isooctyl acrylate, butyl acrylate, lauryl methacrylate, and ethyl acrylate. The acrylamide monomer is one or a combination of two or more of acrylamide, N-hydroxymethylacrylamide, and diacetone acrylamide.

6. The low-VOC environmentally friendly exterior wall anti-efflorescence alkaline primer emulsion according to claim 1, characterized in that, The silane coupling agent is one or a combination of two or more of vinyltriethoxysilane, vinyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane; the persulfate initiator is one of potassium persulfate, ammonium persulfate, or sodium persulfate; the pH adjuster is liquid alkali or 2-amino-2-methyl-1-propanol; and the plant-based defoamer is a turpentine derivative defoamer.

7. The low-VOC environmentally friendly exterior wall anti-efflorescence primer emulsion according to claim 1, characterized in that, The post-treatment agent consists of an oxidant and a reducing agent, with the oxidant being tert-butyl hydrogen peroxide.

8. A method for preparing a low-VOC environmentally friendly exterior wall anti-efflorescence alkaline primer emulsion, characterized in that, The method for preparing a low-VOC environmentally friendly exterior wall anti-efflorescence primer emulsion as described in any one of claims 1-7 includes the following steps: S1. While maintaining stirring, a portion of deionized water, a portion of biodegradable emulsifier, a portion of styrene, a portion of acrylate monomers, and a portion of acrylamide monomers are added sequentially to the emulsification tank to prepare a stable pre-emulsion. S2 In a reactor equipped with a stirrer, the remaining deionized water, the remaining biodegradable emulsifier, and part of the reactive emulsifier are added sequentially and the temperature is raised to 60-65℃. 5%-10% of the total mass of the pre-emulsion is added to the reactor and stirred for 5-15 minutes. The temperature is then raised to 70-75℃, and an initiator solution prepared by adding 15%-30% of the total mass of the persulfate initiator is added to carry out the seed reaction. S3 While maintaining stirring, add the remaining styrene, remaining acrylate monomers, unsaturated carboxylic acids, remaining acrylamide monomers, remaining reactive emulsifiers, and silane coupling agents to the remaining preemulsion one from step S1 to prepare preemulsion two. S4 After the above seeds have reacted for 20-30 minutes, start adding pre-emulsion II dropwise, and at the same time add the initiator solution prepared with the remaining persulfate initiator. Control the reaction temperature at 80-85℃. Add pre-emulsion II dropwise for 2-3 hours, and the addition of the initiator solution should be delayed by 15-30 minutes after the addition of pre-emulsion II to reduce the amount of residual monomer. S5 is then kept at a constant temperature for 1-2 hours, followed by flash evaporation and stripping to complete the degassing process. The flash evaporation conditions are: 1.5-3 hours of feeding, vacuum degree -0.05 to -0.095 MPa, and temperature 60-80℃. During the stripping process, a post-treatment agent is added dropwise, and the dropping rate is controlled. The dropping time is 15-30 minutes. S6 is cooled to below 40℃, and then the pH is adjusted to 7.0-8.0 using a pH adjuster. Then, an environmentally friendly bactericide and a plant-based defoamer are added. Finally, deionized water is added to adjust the solid content, and the material is filtered out to obtain the low-VOC environmentally friendly exterior wall anti-efflorescence alkaline primer emulsion.

9. The method for producing a low-VOC environmentally friendly exterior wall anti-efflorescence alkaline primer emulsion according to claim 8, characterized in that, In step S6, the remaining biodegradable emulsifier is added before adjusting the pH.

10. The method for producing a low-VOC environmentally friendly exterior wall anti-efflorescence alkaline primer emulsion according to claim 8, characterized in that, A low-VOC, environmentally friendly, anti-alkali efflorescence primer emulsion for exterior walls is prepared for use as a primer coating for building exterior walls; This low-VOC environmentally friendly exterior wall anti-alkali 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℃, a minimum film-forming temperature of 20-33℃, and a VOC content ≤ 10 g / L.