WO2023206768A1 - Salt-fog-resistant self-drying acrylate emulsion and preparation method therefor and application thereof - Google Patents

Abstract

Disclosed is a salt-fog-resistant self-drying acrylate emulsion, which is prepared from the following components in parts by weight: 40-60 parts of deionized water, 38-58 parts of raw material monomers, 0.001-0.15 part of a polymerizable acrylic phosphate monomer, 0.05-0.1 part of a polymerizable carbamido monomer, 0.5-2 parts of an emulsifier, 0.1-0.6 part of an initiator, 0.1-0.5 part of a buffering agent, 0.05-0.1 part of an oxidant, 0.05-0.1 part of a reducing agent, and 0.2-0.6 part of a neutralizing agent. The present invention also provides a preparation method for the salt-fog-resistant self-drying acrylate emulsion and an application thereof in the field of coatings. A coating prepared according to the formula and the method can effectively improve the salt fog resistance and corrosion resistance of steel.

Description

A kind of salt spray-resistant self-drying acrylic emulsion and its preparation method and application

[Amended 11.07.2022 in accordance with Rule 26]
This application claims priority from Chinese patent application 202210462494X with a filing date of April 28, 2022. This application cites the full text of the above-mentioned Chinese patent application.

Technical field

The invention relates to a salt spray-resistant self-drying acrylic emulsion and its preparation method and application, and belongs to the technical field of coatings.

Background technique

At present, due to the characteristics of fast drying and high weather resistance of acrylic emulsion, water-based one-component self-drying acrylic coatings are more and more widely used in steel structure coatings. However, since the film-forming mechanism of self-drying acrylic emulsion paint is generally the stacking of ordinary physically dry latex particles, the density of the final paint film is relatively average, resulting in gaps between the particles, and the salt spray resistance and anti-corrosion effect is greatly reduced.

Contents of the invention

The purpose of this invention is to synthesize an emulsion that has excellent salt spray corrosion resistance to steel substrates by introducing special functional monomers and changing the process. The core of the technology is to introduce polymerizable acrylic acid phosphate and polymerizable Urea-based monomer, through appropriate proportions and appropriate feeding processes, the emulsion prepared in the steel structure coating can improve the adhesion between the coating and the substrate, thereby greatly improving its salt spray and corrosion resistance.

The invention provides a salt spray-resistant self-drying acrylic emulsion. Each component in the raw materials for preparation includes: 40-60 parts by weight of deionized water, 38-58 parts of raw material monomers, and polymerizable acrylic phosphate. Monomer 0.001-0.15 parts, polymerizable urea monomer 0.05-0.1 parts, emulsifier 0.5-2 parts, initiator 0.1-0.6 parts, buffer 0.1-0.5 parts, oxidizing agent 0.05-0.1 part, reducing agent 0.05- 0.1 part, neutralizer 0.2-0.6 part.

Preferably, the raw material monomers include styrene, n-butyl acrylate, methyl methacrylate, ethyl acrylate, isooctyl methacrylate, isooctyl acrylate, acrylic acid, methacrylic acid, acrylamide, methyl Various types of acrylamide.

Preferably, the polymerizable acrylic phosphate monomer includes PAM100 and/or PAM200.

Preferably, the polymerizable urea-based monomer includes MEEU50W and/or WAM-II.

Preferably, the emulsifier includes anionic emulsifier and/or nonionic emulsifier, wherein the anionic emulsifier includes fatty alcohol polyoxyethylene ether sulfate, alkyl sulfate and alkyl alcohol ether amber. Acid, the nonionic emulsifier includes fatty alcohol polyoxyethylene ethers.

Preferably, the initiator is a persulfate compound, including one or more of ammonium persulfate and potassium persulfate.

Preferably, the buffering agent includes one or more of sodium bicarbonate, ammonium bicarbonate, sodium dihydrogen phosphate, and ammonia water.

Preferably, the oxidizing agent includes one or more of hydrogen peroxide and tert-butyl hydroperoxide.

Preferably, the reducing agent includes one or more of sodium bisulfite, sodium formaldehyde sulfoxylate, ascorbic acid, and erythorbic acid.

Preferably, the neutralizing agent includes one or more of ammonia, dimethylethanolamine, 2-amino-2-methyl-1-propanol, sodium hydroxide, and potassium hydroxide.

The invention also provides a method for preparing a salt spray-resistant self-drying acrylic emulsion, which specifically includes the following steps:

S1. Preparation of pre-emulsion: Add a certain amount of water and emulsifier into the pre-emulsification kettle, start stirring to 200-350r/min, stir for 15-20 minutes, then add some raw material monomers to completely dissolve, and then slowly Add the remaining raw material monomers, increase the rotation speed to 400-600 rpm, and stir and disperse at high speed for 30-60 minutes to prepare a pre-emulsion;

S2. Preparation of dripping initiator solution: accurately weigh and add a certain amount of water to the initiator tank, then add part of the initiator as the dripping initiator, and fully dissolve it for later use;

S3. Preparation of the initial priming initiator aqueous solution: Add a certain amount of deionized water to a container, and then add a certain amount of initiator as the initial priming initiator, and fully dissolve it for later use;

S4. Add a certain amount of deionized water, all buffers, and the remaining emulsifier to the reaction kettle equipped with a condensation tube, a dripping device, a stirrer, a thermometer, and a circulating water jacket, and start stirring to 150-200r. /min, turn on heating and circulating cooling water, and heat to 80-90°C;

S5. When the temperature of the reaction kettle is stabilized at 80-90°C, take 3-10% of the pre-emulsion prepared in step S1 and flow it directly into the reaction kettle. At the same time, add the initial primer initiator aqueous solution prepared in step S3 and observe the reaction. The color of the kettle changes to blue and the temperature rises significantly;

S6. After waiting for the reaction in the kettle for 10-15 minutes and the temperature stabilizing at 80-90°C, continue to drip the remaining pre-emulsion and the dripping initiator solution prepared in step S2 at a constant speed. Control the temperature at 80-90°C and add dropwise. The stirring speed during the process is increased by 15 rpm every 30 minutes;

S7. When the dropping process continues for 2 hours, add all the polymerizable acrylic phosphate monomer and polymerizable urea monomer to the remaining pre-emulsion above and continue stirring at 400-600 rpm. Evenly dispersed;

S8. Continue to drip the pre-emulsion and drip the initiator solution until all materials are dripped. The total dripping time before and after is controlled at 3-3.5 hours. After the dripping is completed, keep it warm for 1.5-2 hours. The insulation temperature is controlled at 84 -88℃;

S9. Prepare the oxidant aqueous solution and the reducing agent aqueous solution respectively during the heat preservation process;

S10. After the heat preservation is completed, quickly lower the temperature in the reaction kettle to 55-75°C;

S11. After the temperature drops to the above range, drop the oxidant aqueous solution and the reducing agent aqueous solution prepared in step S9 at the same time. The dropping time is 30 minutes and the temperature is maintained at 55-75°C;

S12. After the dropwise addition is completed, keep it at 55-75°C for 30-60 minutes;

S13. After the heat preservation is completed, quickly cool down to below 40°C, slowly add the neutralizer, and adjust the pH of the emulsion in the kettle to 7-9;

S14. After adjusting the pH value of the emulsion, continue to cool to room temperature, filter and discharge the material to obtain a salt spray-resistant self-drying acrylic emulsion.

More preferably, the temperature of steps S4, S5 and S6 is 82-86°C.

More preferably, the temperature of steps S10, S11 and S12 is 65-75°C.

The polymer emulsion prepared by the above steps has a solid content of 45-47%, a pH of 7-9, a viscosity of 1500-5000 mPa.s, a theoretical glass transition temperature of the polymer of 30°C-60°C, and a minimum composition of The film temperature is between 20-45℃.

The present invention also provides an application of the above-mentioned salt spray-resistant self-drying acrylic emulsion in the field of coatings.

The technical characteristics and core advantages of the present invention are: by adding polymerizable acrylic acid phosphate monomer and polymerizable urea monomer, not only can the synthesis process be more stable, but also the hydrophilic segment of the outer layer of the polymer particles can be introduced It contains more phosphate ester groups and urea-based monomers, so that after the polymer paint film dries, it can better adhere to the steel substrate, and further passivates the steel substrate, thereby improving the corrosion resistance of the steel. Compared with self-drying acrylic water-based paints that do not add such substances, the salt spray-resistant self-drying acrylic emulsion paint prepared by this invention has more obvious salt spray resistance and anti-corrosion properties.

Detailed ways

The present invention will be further described with reference to the following examples, but the protection scope of the present invention is not limited thereto.

Example 1

A method for preparing a salt spray-resistant self-drying acrylic emulsion, which specifically includes the following steps:

S1. Preparation of pre-emulsion: Accurately weigh 185g of deionized water and 7.2g of anionic emulsifier sodium lauryl sulfate, put them into the pre-emulsification bottle, turn on stirring to 210r/min, stir for 15 minutes; then weigh accurately in sequence 7.3g acrylamide and 6.8g acrylic acid. After continuing to stir for 15 minutes, add 258.6g styrene, 88.2g n-butyl acrylate, and 78.9g isooctyl acrylate in sequence, increase the rotation speed to 420r/min, and disperse at high speed for 30 minutes to prepare Pre-emulsion;

S2. Preparation of dripping initiator solution: Add 12.7g of deionized water accurately into the initiator tank, and then add 1.75g of ammonium persulfate to fully dissolve and set aside;

S3. Preparation of initial primer initiator solution: Add 8g of deionized water to a container, then add 0.8g of ammonium persulfate, stir to fully dissolve and set aside;

S4. Add 259.4g deionized water, 1.03g buffer sodium bicarbonate, and 7.7g anionic emulsifier dodecyl into a reaction kettle equipped with a condensation tube, a dripping device, a stirrer, a thermometer, and a circulating water jacket. Sodium sulfate, 1.9g non-ionic emulsifier OP-10, start stirring to 160 rpm, start heating and circulating cooling water, heat to 82-86°C;

S5. When the temperature of the reaction kettle is stable at 82-86°C, take 45g of the pre-emulsion prepared in step S1 and add it directly into the reaction kettle. At the same time, add the initial primer aqueous solution prepared in step S3 and observe the color change in the reaction kettle. It is blue and the temperature has increased significantly;

S6. Wait for the reaction in the kettle for 10-15 minutes. After the temperature stabilizes at 82-86°C, continue to drip the remaining pre-emulsion and the dripping initiator solution prepared in step S2 at a constant speed. Control the temperature at 82-86°C and add dropwise. The stirring speed during the process is increased by 15r/min every 30 minutes;

S7. When the dropping process continues for 2 hours, add 4.2g of polymerizable acrylic phosphate monomer PAM100 and 4.5g of polymerizable urea-based monomer MEEU50W into the remaining pre-emulsion above at 400-600 rpm. Continue stirring for several minutes to disperse evenly;

S8. Continue dripping until all the pre-emulsion and initiator solutions have been added. The total dripping time before and after is controlled to 3-3.5 hours. After the pre-emulsion and initiator solutions have been added, keep warm for 1.5-2 hours. The temperature is controlled at 84-88℃;

S9. During the heat preservation process, add 12.6g water and 0.78g tert-butyl hydroperoxide oxidant into a container, stir evenly, and prepare the oxidant solution; weigh 12.6g water into another container and add 0.48g substantia Sodium bisulfate reducing agent, stir evenly to prepare a reducing agent solution;

S10. After the heat preservation is completed, quickly lower the temperature in the reaction kettle to 65-75°C;

S11. After the temperature drops to the above range, drip the oxidant aqueous solution and the reducing agent aqueous solution prepared in step S9 at the same time. The dripping time is 30 minutes and the temperature is maintained at 55-75°C;

S12. After the dropwise addition is completed, keep it at 55-75°C for 30-60 minutes;

S13. After the heat preservation is completed, quickly cool down to below 40°C, slowly add 4.8g of neutralizing agent ammonia water, and adjust the pH of the emulsion in the kettle to 7-9;

S14. After adjusting the pH value of the emulsion, continue to cool to room temperature, filter and discharge the material to obtain a salt spray-resistant self-drying acrylic emulsion.

Example 2

A method for preparing a salt spray-resistant self-drying acrylic emulsion, which specifically includes the following steps:

S1. Preparation of pre-emulsion: Accurately weigh 185g of deionized water and 8.1g of anionic emulsifier A102, put them into the pre-emulsification bottle, turn on stirring to 210r/min, and stir for 15 minutes; then accurately weigh 7.3g of acrylamide, 6.8g of acrylic acid, continue stirring for 15 minutes, add 258.6g of styrene, 88.2g of n-butyl acrylate, and 78.9g of isooctyl acrylate, increase the rotation speed to 420r/min, and disperse at high speed for 30 minutes to prepare a pre-emulsion;

S2. Preparation of dripping initiator solution: Add 12.7g of deionized water accurately into the initiator tank, and then add 1.75g of ammonium persulfate to fully dissolve and set aside;

S3. Preparation of initial primer initiator solution: Add 8g of deionized water to a container, then add 0.8g of ammonium persulfate, stir to fully dissolve and set aside;

S4. Add 259.4g deionized water, 1.03g buffer sodium bicarbonate, 7.7g anionic emulsifier A102, and 2.1g into the reaction kettle equipped with a condensation tube, a dripping device, a stirrer, a thermometer, and a circulating water jacket heating. Non-ionic emulsifier NP-10, start stirring to 160 rpm, start heating and circulating cooling water, heat to 82-86°C;

S5. When the temperature of the reaction kettle is stable at 82-86°C, take 45g of the pre-emulsion prepared in step S1 and add it directly into the reaction kettle. At the same time, add the initial primer aqueous solution prepared in step S3 and observe the color change in the reaction kettle. It is blue and the temperature has increased significantly;

S6. Wait for the reaction in the kettle for 10-15 minutes. After the temperature stabilizes at 82-86°C, continue to drip the remaining pre-emulsion and the dripping initiator solution prepared in step S2 at a constant speed. Control the temperature at 82-86°C and add dropwise. The stirring speed during the process is increased by 15r/min every 30 minutes;

S7. When the dropping process continues for 2 hours, add 4.2g of polymerizable acrylic phosphate monomer PAM200 and 4.5g of polymerizable urea-based monomer WAM-Ⅱ into the remaining pre-emulsion above, at 400- Continue stirring at 600 rpm to disperse evenly;

S8. Continue dripping until all the pre-emulsion and initiator solutions have been added. The total dripping time before and after is controlled to 3-3.5 hours. After the pre-emulsion and initiator solutions have been added, keep warm for 1.5-2 hours. The temperature is controlled at 84-88℃;

S9. During the heat preservation process, add 12.6g water and 0.78g tert-butyl hydroperoxide oxidant in a container, stir evenly, and prepare the oxidant solution; weigh 12.6g water in another container and add 0.48g sulfate. Sodium bisulfate reducing agent, stir evenly to prepare a reducing agent solution;

S10. After the heat preservation is completed, quickly lower the temperature in the reaction kettle to 65-75°C;

S11. After the temperature drops to the above range, drop the oxidant aqueous solution and the reducing agent aqueous solution prepared in step S9 at the same time. The dropping time is 30 minutes and the temperature is maintained at 55-75°C;

S12. After the dropwise addition is completed, keep it at 55-75°C for 30-60 minutes;

S13. After the heat preservation is completed, quickly cool down to below 40°C, slowly add 4.8g of neutralizing agent ammonia water, and adjust the pH of the emulsion in the kettle to 7-9;

S14. After adjusting the pH value of the emulsion, continue to cool to room temperature, filter and discharge the material to obtain a salt spray-resistant self-drying acrylic emulsion.

Example 3

A method for preparing a salt spray-resistant self-drying acrylic emulsion, which specifically includes the following steps:

S1. Preparation of pre-emulsion: Accurately weigh 185g of deionized water and 7.6g of anionic emulsifier FES32, put them into the pre-emulsification bottle, turn on stirring to 210r/min, and stir for 15 minutes; then accurately weigh 7.3g of acrylamide, 6.8g of acrylic acid, continue stirring for 15 minutes, add 258.6g of styrene, 88.2g of n-butyl acrylate, and 78.9g of isooctyl acrylate, increase the rotation speed to 420r/min, and disperse at high speed for 30 minutes to prepare a pre-emulsion;

S2. Preparation of dripping initiator solution: Add 12.7g of deionized water accurately into the initiator tank, and then add 1.75g of ammonium persulfate to fully dissolve and set aside;

S3. Preparation of initial primer initiator solution: Add 8g of deionized water to a container, then add 0.8g of ammonium persulfate, stir to fully dissolve and set aside;

S4. Add 259.4g deionized water, 1.03g buffer sodium bicarbonate, 7.9g anionic emulsifier FES32, and 2.2g into the reaction kettle equipped with a condensation tube, a dripping device, a stirrer, a thermometer, and a circulating water jacket heating. Nonionic emulsifier S90, start stirring to 160 rpm, start heating and circulating cooling water, and heat to 82-86°C;

S5. When the temperature of the reaction kettle is stable at 82-86°C, take 45g of the pre-emulsion prepared in step S1 and add it directly into the reaction kettle. At the same time, add the initial primer aqueous solution prepared in step S3 and observe the color change in the reaction kettle. It is blue and the temperature has increased significantly;

S6. Wait for the reaction in the kettle for 10-15 minutes. After the temperature stabilizes at 82-86°C, continue to drip the remaining pre-emulsion and the dripping initiator solution prepared in step S2 at a constant speed. Control the temperature at 82-86°C and add dropwise. The stirring speed during the process is increased by 15r/min every 30 minutes;

S7. When the dripping process continues for 2 hours, add 4.2g of polymerizable acrylic phosphate monomer PAM200 and 4.5g of polymerizable urea-based monomer MEEU50W into the remaining pre-emulsion above, and rotate at 400-600 rpm. Continue stirring every minute to disperse evenly;

S8. Continue dripping until all the pre-emulsion and initiator solutions have been added. The total dripping time before and after is controlled to 3-3.5 hours. After the pre-emulsion and initiator solutions have been added, keep warm for 1.5-2 hours. The temperature is controlled at 84-88℃;

S9. During the heat preservation process, add 12.6g water and 0.78g tert-butyl hydroperoxide oxidant in a container, stir evenly, and prepare the oxidant solution; weigh 12.6g water in another container and add 0.48g sulfate. Sodium bisulfate reducing agent, stir evenly to prepare a reducing agent solution;

S10. After the heat preservation is completed, quickly lower the temperature in the reaction kettle to 65-75°C;

S11. After the temperature drops to the above range, drip the oxidant aqueous solution and the reducing agent aqueous solution prepared in step S9 at the same time. The dripping time is 30 minutes and the temperature is maintained at 55-75°C;

S12. After the dropwise addition is completed, keep it at 55-75°C for 30-60 minutes;

S13. After the heat preservation is completed, quickly cool down to below 40°C, slowly add 4.8g of neutralizing agent ammonia water, and adjust the pH of the emulsion in the kettle to 7-9;

S14. After adjusting the pH value of the emulsion, continue to cool to room temperature, filter and discharge the material to obtain a salt spray-resistant self-drying acrylic emulsion.

Comparative ratio

A method for preparing a self-drying acrylic emulsion with ordinary salt spray resistance. The basic process is the same as Comparative Example 1, except that step S7 is omitted.

Implementation Effect

(1) Emulsion performance data

The basic test data of the emulsions prepared in the above examples and comparative examples are shown in Table 1.

Table 1 Test data of basic parameters of emulsion

Test items	Example 1	Example 2	Example 3	Comparative ratio
Solid content	46.7%	46.4%	46.6%	46.4%
viscosity	2892mPa.s	2570mPa.s	2769mPa.s	2570mPa.s
PH	7.3	7.4	7.5	7.4
particle size	101nm	104nm	103nm	104nm

(2) Preparation of paint

Table 2 Preparation raw materials for water-washed industrial paint steel structure topcoat

serial number	materials	Proportion (mass percentage, %)	supplier
1	water	8.0	​
2	2-Amino-2-methyl-1-propanol (AMP-95)	0.2	Dow
3	Dispersant 190	0.8	Peak
4	Defoaming agent 810	0.1	Digo
5	Titanium dioxide	3	dragon python
6	ZPA aluminum silicate modified zinc phosphate anti-rust pigment	10	German Haibo

7	black pulp	1	Cody
8	lotion	60	The above homemade
9	alcohol ester twelve	3.5	Eastman
10	Defoaming agent 902W	0.05	Digo
11	Anti-flash rust additive FA-179	0.5	hemmings
12	Wetting agent 270	0.2	Digo
13	Thickener 8W	0.3	Dow
14	Thickener 12W	0.1	Dow
15	Add water	12.25	​
​	total	100	​

The emulsions described in the above examples and comparative examples were prepared according to the formula shown in Table 2 and according to the following steps to prepare a water-based industrial paint steel structure topcoat:

Step 1: Add materials 1, 2, 3 and 4 in sequence and stir evenly at low speed (200-300r/min);

Step 2: Add substances 5, 6 and 7 in sequence, stir evenly at medium speed (500-800r/min), then adjust to high speed (1000-1500r/min) and grind for 30 minutes until the fineness is <30 μm;

Step 3: Add substances 8-15 sequentially, stir for 10 minutes, adjust the viscosity to 90±5KU, filter and discharge the material, and prepare the coating.

(3) Conditions for coating film performance testing

a) Base material: polished carbon steel plate and tinplate;

b) Coating film preparation: wire rod scraping;

c) Preparation and maintenance conditions of double-layer coating: one coat of scraping with 100μm wire rod, curing for 4 hours under standard conditions, the second coat of scraping with 100μm wire rod, and curing for 7 days under standard conditions.

(4) Paint film performance testing methods and standards

Table 3 Performance test related standards

Test items	Implementation standards
Paint film thickness/μm	GB/T 13452.2
Impact resistance test (cm)	GB/T 1732-1993
Pencil hardness (scratches)	GB/T 6739-2006
Adhesion test (cross-hatch)	GB/T 9286-1998

Water resistance test	GB/T 1732-1993
Salt water resistance test (3% NaCl aqueous solution)	GB/T 9274-1988
Salt spray resistance test	GB/T 1771-2007

(5) Paint film performance test results

Table 4 Performance test results of different paint films

Through the comparison of the final paint film test data above, the paint film made from the emulsion prepared by introducing polymerizable acrylic phosphate monomer and polymerizable urea monomer is better than the emulsion paint film prepared without adding these two types of materials. The water resistance, salt water resistance and salt spray resistance have been significantly improved, proving that this type of self-drying acrylic emulsion has excellent anti-corrosion properties.

Claims (10)

1. A salt-spray-resistant self-drying acrylic emulsion, characterized in that the raw materials for its preparation include, by weight, 40-60 parts of deionized water, 38-58 parts of raw material monomers, and polymerizable acrylic phosphoric acid. Ester monomer 0.001-0.15 parts, polymerizable urea monomer 0.05-0.1 parts, emulsifier 0.5-2 parts, initiator 0.1-0.6 parts, buffer 0.1-0.5 parts, oxidizing agent 0.05-0.1 part, reducing agent 0.05 -0.1 part, neutralizer 0.2-0.6 part.
2. A kind of salt spray resistant self-drying acrylic emulsion as claimed in claim 1, characterized in that the raw material monomers include: styrene, n-butyl acrylate, methyl methacrylate, ethyl acrylate, methyl methacrylate Isooctyl acrylate, isooctyl acrylate, acrylic acid, methacrylic acid, acrylamide, methacrylamide, ethylene urea ethoxy methacrylate, and acrylic acid phosphate monomers.
3. A salt spray-resistant self-drying acrylic emulsion as claimed in claim 1, characterized in that the polymerizable acrylic phosphate monomer includes PAM100 and/or PAM200.
4. A salt spray-resistant self-drying acrylic emulsion as claimed in claim 1, characterized in that the polymerizable urea-based monomer includes MEEU50W and/or WAM-II.
5. A kind of salt spray resistant self-drying acrylic emulsion as claimed in claim 1, characterized in that the emulsifier includes anionic emulsifier and/or nonionic emulsifier, wherein the anionic emulsifier It includes one or more of fatty alcohol polyoxyethylene ether sulfate, alkyl sulfate and alkyl alcohol ether succinic acid, and the nonionic emulsifier includes fatty alcohol polyoxyethylene ethers.
6. A kind of salt spray resistant self-drying acrylic emulsion as claimed in claim 1, characterized in that:

   The initiator is a persulfate compound, including one or more of ammonium persulfate and potassium persulfate;

   The buffering agent includes one or more of sodium bicarbonate, ammonium bicarbonate, sodium dihydrogen phosphate, and ammonia water.
7. A kind of salt spray resistant self-drying acrylic emulsion as claimed in claim 1, characterized in that:

   The oxidizing agent includes one or more of hydrogen peroxide and tert-butyl hydroperoxide;

   The reducing agent includes one or more of sodium bisulfite, sodium formaldehyde sulfoxylate, ascorbic acid, and erythorbic acid;

   The neutralizing agent includes one or more of ammonia, dimethylethanolamine, 2-amino-2-methyl-1-propanol, sodium hydroxide, and potassium hydroxide.
8. A method for preparing a salt spray-resistant self-drying acrylic emulsion according to any one of claims 1-7, characterized in that it specifically includes the following steps:

   S1. Preparation of pre-emulsion: Add a certain amount of water and emulsifier into the pre-emulsification kettle, start stirring to 200-350r/min, stir for 15-20 minutes, then add some raw material monomers to completely dissolve, and then slowly Add the remaining raw material monomers, increase the rotation speed to 400-600 rpm, and stir and disperse at high speed for 30-60 minutes to prepare a pre-emulsion;

   S2. Preparation of dripping initiator solution: accurately weigh and add a certain amount of water to the initiator tank, then add part of the initiator as the dripping initiator, and fully dissolve it for later use;

   S3. Preparation of the initial priming initiator aqueous solution: Add a certain amount of deionized water to a container, and then add a certain amount of initiator as the initial priming initiator, and fully dissolve it for later use;

   S4. Add a certain amount of deionized water, all buffers, and the remaining emulsifier to the reaction kettle equipped with a condensation tube, a dripping device, a stirrer, a thermometer, and a circulating water jacket, and start stirring to 150-200r. /min, turn on heating and circulating cooling water, and heat to 80-90°C;

   S5. When the temperature of the reaction kettle is stabilized at 80-90°C, take 3-10% of the pre-emulsion prepared in step S1 and flow it directly into the reaction kettle. At the same time, add the initial priming initiator aqueous solution prepared in step S3 and observe the reaction. The color of the kettle changes to blue and the temperature rises significantly;

   S6. After waiting for the reaction in the kettle for 10-15 minutes and the temperature stabilizing at 80-90°C, continue to drip the remaining pre-emulsion and the dripping initiator solution prepared in step S2 at a constant speed. Control the temperature at 80-90°C and add dropwise. The stirring speed during the process is increased by 15 rpm every 30 minutes;

   S7. When the dropping process continues for 2 hours, add all the polymerizable acrylic phosphate monomer and polymerizable urea monomer to the remaining pre-emulsion above and continue stirring at 400-600 rpm. Evenly dispersed;

   S8. Continue to drip the pre-emulsion and drip the initiator solution until all materials are dripped. The total dripping time before and after is controlled at 3-3.5 hours. After the dripping is completed, keep it warm for 1.5-2 hours. The insulation temperature is controlled at 84 -88℃;

   S9. Prepare the oxidant aqueous solution and the reducing agent aqueous solution respectively during the heat preservation process;

   S10. After the heat preservation is completed, quickly lower the temperature in the reaction kettle to 55-75°C;

   S11. After the temperature drops to the above range, drop the oxidant aqueous solution and the reducing agent aqueous solution prepared in step S9 at the same time. The dropping time is 30 minutes and the temperature is maintained at 55-75°C;

   S12. After the dropwise addition is completed, keep it at 55-75°C for 30-60 minutes;

   S13. After the heat preservation is completed, quickly cool down to below 40°C, slowly add the neutralizer, and adjust the pH of the emulsion in the kettle to 7-9;

   S14. After adjusting the pH value of the emulsion, continue to cool to room temperature, filter and discharge the material to obtain a salt spray-resistant self-drying acrylic emulsion.
9. The salt spray-resistant self-drying acrylic emulsion prepared according to claims 1-8, characterized in that the solid content of the emulsion is 45-47%, the pH is 7-9, and the viscosity is 1500-5000mPa. s, the theoretical glass transition temperature of the polymer is 30℃-60℃, and the minimum film-forming temperature is 20-45℃.
10. An application of the salt spray-resistant self-drying acrylic emulsion in the field of coatings according to claims 1-9.