An aqueous acrylic dispersion, its preparation method and application

Abstract

The present invention relates to an aqueous acrylic dispersion, a preparation method thereof and an application, belonging to the technical field of aqueous coatings. The aqueous acrylic dispersion described in the present invention comprises a first copolymer; the copolymerization monomers of the first copolymer include a first monomer, and the first monomer is sorbitan oleate; the first monomer accounts for 1-20 wt% of the solid content of the aqueous acrylic dispersion; the solid content acid value of the aqueous acrylic dispersion is 15-35 mg KOH / g, and the solid content hydroxyl value is 50-165 mg KOH / g. The aqueous acrylic dispersion has excellent storage stability, and the aqueous coating using the aqueous acrylic dispersion as the main film-forming substance has the advantages of high gloss, long pot life and good water resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of waterborne coatings, and particularly to a waterborne acrylic dispersion and its preparation method and application. Background Art

[0002] With the increasing emphasis on environmental protection in the coating industry, the use of solvent-based coatings is facing more and more restrictions. Nowadays, waterborne coatings with low VOC (volatile organic compounds) have become an inevitable trend in the development of the coating industry. Waterborne coatings using waterborne acrylic dispersions as the main film-forming substances (such as two-component waterborne polyurethane coatings) stand out with their significant advantages. The coatings formed not only have high gloss and fullness, but also excellent weather resistance and chemical resistance, especially outstanding light and color retention performance. Their comprehensive performance has approached or even reached the level of solvent-based two-component polyurethane coatings, so they have been widely used in the coating fields of substrates such as wood and metal, and have become an important force in promoting the green transformation of the industry.

[0003] CN100402615C discloses a waterborne base dispersion (waterborne acrylic dispersion). By using alicyclic unsaturated monomers to participate in free radical polymerization and then using triethanolamine as a neutralizing agent, a waterborne acrylic dispersion with high hardness, water resistance, and excellent chemical resistance can be obtained. CN101353470B discloses a secondary polymer aqueous dispersion (waterborne acrylic dispersion). By using long-chain aliphatic unsaturated monomers to participate in free radical polymerization, a waterborne acrylic dispersion with a high bubble-free film thickness can be obtained. CN114920884A discloses a hydroxyl acrylic dispersion that is universal for waterborne and oil-based curing agents. By using a reactive emulsifier as a comonomer, the obtained hydroxyl acrylic dispersion has good compatibility with waterborne and oil-based polyisocyanate curing agents.

[0004] However, these waterborne acrylic dispersions all have some defects, and there is room for further improvement in the pot life, water resistance, and gloss of waterborne coatings using the above waterborne acrylic dispersions as the main film-forming substances. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to provide a waterborne acrylic dispersion and its preparation method and application. The waterborne acrylic dispersion has excellent storage stability, and the waterborne coating using the waterborne acrylic dispersion as the main film-forming substance has the advantages of high gloss, long pot life, and good water resistance.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] The present invention provides an aqueous acrylic dispersion, comprising a first copolymer; the comonomers of the first copolymer include a first monomer, and the first monomer has the structure of formula (1) (i.e., the first monomer is sorbitan oleate); the first monomer accounts for 1-20 wt% of the solid content of the aqueous acrylic dispersion; the solid content acid value of the aqueous acrylic dispersion is 15-35 mg KOH / g, and the solid content hydroxyl value is 50-165 mg KOH / g;

[0008]

[0009] In formula (1), R1, R2, R3, and R4 are independently one of -C(=O)-(CH2)7CH=CH(CH2)7CH3 and H, and at least one of R1, R2, R3, and R4 is a -C(=O)-(CH2)7CH=CH(CH2)7CH3 group, and the statistical average value of a + b + c + d is 0-40.

[0010] Surprisingly, through research, the present invention finds that in the aqueous acrylic dispersion, the first copolymer obtained by using the first monomer with a specific structure as a comonomer can significantly improve the gloss, pot life, and water resistance of the aqueous coating using the aqueous acrylic dispersion as the main film-forming substance.

[0011] In the present invention, the first monomer has the structure of formula (1) and is sorbitan oleate. The first monomer contains an oleate group (oleate group: -O-C(=O)-(CH2)7CH=CH(CH2)7CH3, which is composed of the -C(=O)-(CH2)7CH=CH(CH2)7CH3 group and the "O" connected thereto). The oleate group in the first monomer contains an unsaturated double bond that can participate in free radical polymerization. Through the free radical polymerization of the unsaturated double bond, it is introduced into the first copolymer, so that the first copolymer has a hydrophobic long-chain oleate group, thereby significantly improving the water resistance of the first copolymer, and further improving the water resistance of the aqueous acrylic dispersion and its aqueous coating. The first monomer (sorbitan oleate) is an emulsifier. By ingeniously designing and introducing the first monomer into the first copolymer, the present invention can improve the compatibility of the first copolymer with the crosslinking agent (such as polyisocyanate crosslinking agent) in the aqueous coating, especially has a good emulsifying effect on the hydrophobic crosslinking agent (such as hydrophobic polyisocyanate crosslinking agent), so that the aqueous coating can obtain a high-gloss coating film. In addition, the oleate group also has the characteristic of large steric hindrance. After the first monomer is introduced into the first copolymer, the large-steric-hindrance oleate group will wrap the first copolymer, making it more difficult for the hydroxyl groups in the first copolymer to contact and react with the crosslinking agent (such as polyisocyanate crosslinking agent) in the aqueous phase state, so that the aqueous coating has a long pot life.

[0012] In the aqueous acrylic dispersion of the present invention, the first monomer accounts for 1-20 wt% of the solid content of the aqueous acrylic dispersion. If the content of the first monomer is too low, the improvement effects on gloss, pot life, and water resistance are not obvious; if the content of the first monomer is too high, since the first monomer contains an oleate group and has a relatively soft structure, the hardness of the coating film will be significantly reduced.

[0013] The solid content acid value of the aqueous acrylic dispersion of the present invention is 15-35 mg KOH / g, and the solid content hydroxyl value is 50-165 mg KOH / g. Too low an acid value easily leads to poor storage stability of the aqueous acrylic dispersion; too high an acid value will catalyze the side reaction between the crosslinking agent (such as polyisocyanate crosslinking agent) and water after the aqueous acrylic dispersion is formulated into an aqueous coating with a crosslinking agent, resulting in a short pot life of the aqueous coating, and too high an acid value will also make the first copolymer too hydrophilic, ultimately leading to poor water resistance of the aqueous coating. Too low a hydroxyl value will result in too low a crosslinking density of the aqueous coating, affecting water resistance; too high a hydroxyl value will make the synthesis of the aqueous acrylic dispersion difficult, easily leading to problems such as high viscosity and poor fineness.

[0014] As a preferred embodiment of the present invention, the comonomers of the first copolymer further include a second monomer, a third monomer, and a fourth monomer; wherein: the first monomer accounts for 5-35 wt% of the total amount of the comonomers of the first copolymer; the second monomer is a hydroxyl-functionalized unsaturated monomer different from the first monomer, and the second monomer accounts for 10-40 wt% of the total amount of the comonomers of the first copolymer; the third monomer is a carboxyl-functionalized unsaturated monomer, and the third monomer accounts for 0-30 wt% of the total amount of the comonomers of the first copolymer; the fourth monomer is an other unsaturated monomer different from the first monomer, the second monomer, and the third monomer, and the fourth monomer accounts for 20-65 wt% of the total amount of the comonomers of the first copolymer. Preferably, the sum of the amounts of the monomers of the comonomers of the first copolymer is 100 wt%, that is, the sum of the amounts of the first monomer, the second monomer, the third monomer, and the fourth monomer is the sum of the amounts of the comonomers of the first copolymer.

[0015] It should be emphasized that the first copolymer in the aqueous acrylic dispersion of the present invention can be a copolymerization product of a first monomer, a second monomer, a third monomer, and a fourth monomer; it can also be a copolymerization product of a first monomer, a second monomer, and a fourth monomer; or it can be a mixture of the above two copolymerization products. Those skilled in the art can select and set according to actual needs, as long as the first monomer accounts for 1-20 wt% of the solid content of the aqueous acrylic dispersion; the solid content acid value of the aqueous acrylic dispersion is 15-35 mg KOH / g, and the solid content hydroxyl value is 50-165 mg KOH / g.

[0016] As a preferred embodiment of the present invention, the aqueous acrylic dispersion may further include a second copolymer; the copolymerization monomers of the second copolymer include a fifth monomer and / or a sixth monomer and / or a seventh monomer; wherein, the fifth monomer is a hydroxyl-functionalized unsaturated monomer different from the first monomer (i.e., the selection ranges of the fifth monomer and the second monomer are the same, but they are independent of each other); the sixth monomer is a carboxyl-functionalized unsaturated monomer (i.e., the selection ranges of the sixth monomer and the third monomer are the same, but they are independent of each other); the seventh monomer is other unsaturated monomers different from the first monomer, the fifth monomer, and the sixth monomer (i.e., the selection ranges of the seventh monomer and the fourth monomer are the same, but they are independent of each other).

[0017] It should be further noted that for the present invention, those skilled in the art can choose whether the aqueous acrylic dispersion of the present invention includes or does not include the second copolymer according to actual needs, as long as the "first monomer accounts for 1-20 wt% of the solid content of the aqueous acrylic dispersion, the acid value of the solid content of the aqueous acrylic dispersion is 15-35 mg KOH / g, and the hydroxyl value of the solid content is 50-165 mg KOH / g" in the aqueous acrylic dispersion of the present invention can be satisfied. For example, for the first copolymer in the aqueous acrylic dispersion of the present invention, if it can provide conditions that meet "the first monomer accounts for 1-20 wt% of the solid content of the aqueous acrylic dispersion; the acid value of the solid content of the aqueous acrylic dispersion is 15-35 mg KOH / g, and the hydroxyl value of the solid content is 50-165 mg KOH / g", then the second copolymer can be chosen not to be included. If the first copolymer in the aqueous acrylic dispersion of the present invention cannot meet the conditions of "the first monomer accounts for 1-20 wt% of the solid content of the aqueous acrylic dispersion; the acid value of the solid content of the aqueous acrylic dispersion is 15-35 mg KOH / g, and the hydroxyl value of the solid content is 50-165 mg KOH / g", such as the content of the first monomer in the solid content of the aqueous acrylic dispersion is too high, the acid value of the solid content of the aqueous acrylic dispersion is too high or too low, and the hydroxyl value of the solid content is too high or too low, the aqueous acrylic dispersion of the present invention can choose to include the second copolymer, and choose each monomer (the fifth monomer, the sixth monomer, the seventh monomer) for copolymerization to obtain the corresponding second copolymer according to the needs of each condition, so that the aqueous acrylic dispersion of the present invention can meet the conditions of "the first monomer accounts for 1-20 wt% of the solid content of the aqueous acrylic dispersion; the acid value of the solid content of the aqueous acrylic dispersion is 15-35 mg KOH / g, and the hydroxyl value of the solid content is 50-165 mg KOH / g".

[0018] As a preferred embodiment of the present invention, the first monomer is at least one of sorbitan monooleate, sorbitan trioleate, polyoxyethylene sorbitan monooleate, and polyoxyethylene sorbitan trioleate.

[0019] As a preferred embodiment of the present invention, the second monomer and the fifth monomer are independently at least one of 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, and 4-hydroxybutyl methacrylate. The second monomer and the fifth monomer can provide hydroxyl groups to enable the aqueous acrylic dispersion of the present invention to have a solid content hydroxyl value that meets the requirements.

[0020] As a preferred embodiment of the present invention, the third monomer and the sixth monomer are independently at least one of methacrylic acid, acrylic acid, itaconic acid, and crotonic acid. The third monomer and the sixth monomer can provide carboxyl groups to enable the aqueous acrylic dispersion of the present invention to have a solid acid value that meets the requirements.

[0021] As a preferred embodiment of the present invention, the fourth monomer and the seventh monomer are (meth)acrylate esters, vinyl aromatic hydrocarbons, and / or vinyl esters without hydroxyl groups and carboxyl groups in which the alcohol part contains a C1-C18 hydrocarbon group. The fourth monomer and the seventh monomer can be used to adjust the content of the first monomer in the solid content of the aqueous acrylic dispersion, the solid acid value of the aqueous acrylic dispersion, and the solid hydroxyl value.

[0022] Preferably, the fourth monomer and the seventh monomer are independently at least one of C1-C18 hydrocarbon esters of methacrylic acid, C1-C18 hydrocarbon esters of acrylic acid, styrene, substituted styrene, vinyl acetate, and vinyl versatate. For example, the fourth monomer and the seventh monomer are independently at least one of methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, n-butyl methacrylate, n-butyl acrylate, isobutyl methacrylate, isobutyl acrylate, tert-butyl methacrylate, tert-butyl acrylate, 2-ethylhexyl methacrylate, 2-ethylhexyl acrylate, dodecyl methacrylate, dodecyl acrylate, octadecyl methacrylate, octadecyl acrylate, cyclohexyl methacrylate, cyclohexyl acrylate, 4-tert-butylcyclohexyl methacrylate, 4-tert-butylcyclohexyl acrylate, isobornyl methacrylate, isobornyl acrylate, styrene, p-methylstyrene, m-methylstyrene, α-methylstyrene, vinyl acetate, vinyl versatate, etc.

[0023] As a preferred embodiment of the present invention, the aqueous acrylic dispersion further includes a neutralizing agent, and the neutralization degree of the aqueous acrylic dispersion is 40-110%. If the neutralization degree is too low, the storage stability of the aqueous acrylic dispersion will be poor, and it is easy to stratify and precipitate; if the neutralization degree is too high, after the aqueous acrylic dispersion is formulated with a crosslinking agent into an aqueous coating, it will catalyze the side reaction between the crosslinking agent (such as a polyisocyanate crosslinking agent) and water, resulting in a shorter pot life of the aqueous coating. In addition, it should be noted that the neutralizing agent needs to be added before adding water (water-in-dispersion). Preferably, the neutralizing agent is at least one of N,N-dimethylethanolamine, triethanolamine, ammonia water, sodium hydroxide, and potassium hydroxide.

[0024] As a preferred embodiment of the present invention, the aqueous acrylic dispersion further comprises water and an organic solvent; the solid content of the aqueous acrylic dispersion is 30 - 60 wt%; the content of the organic solvent in the aqueous acrylic dispersion is 2 - 10 wt%. Too little organic solvent will cause too high viscosity during the polymerization reaction and low polymerization conversion rate; too much organic solvent will cause the aqueous coating to have a high VOC content, which is disadvantageous from an environmental protection perspective.

[0025] The present invention also provides an application of any one of the above-mentioned aqueous acrylic dispersions in an aqueous coating. The aqueous coating using the aqueous acrylic dispersion as the main film-forming substance has the advantages of high gloss, long pot life, and good water resistance.

[0026] Specifically, the present invention provides an aqueous coating, comprising any one of the above-mentioned aqueous acrylic dispersions and a crosslinking agent.

[0027] As a preferred embodiment of the present invention, the crosslinking agent is a polyisocyanate crosslinking agent containing free NCO groups. That is, the present invention provides an application of any one of the above-mentioned aqueous acrylic dispersions in combination with a polyisocyanate crosslinking agent in an aqueous two-component polyurethane coating.

[0028] The present invention also provides a coating film obtained by applying any one of the above-mentioned aqueous coatings on a substrate.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] The aqueous acrylic dispersion has excellent storage stability, and the aqueous two-component polyurethane coating formulated with a polyisocyanate crosslinking agent has the advantages of high gloss, long pot life, and good water resistance. Specific Embodiments

[0031] The present invention will be further described below in conjunction with examples. These examples are only used to illustrate the present invention and not to limit the scope of the present invention. The experimental methods without specific conditions in the following examples are generally carried out according to the conventional conditions in the art or according to the conditions recommended by the manufacturer; the raw materials, reagents, etc. used, unless otherwise specified, are all raw materials and reagents that can be obtained from conventional markets and other commercial channels. Any non-substantive changes and substitutions made by those skilled in the art based on the present invention fall within the scope of protection required by the present invention.

[0032] Example 1

[0033] This example provides an aqueous acrylic dispersion, comprising an organic solvent, a first copolymer, a second copolymer, a neutralizing agent, and deionized water. Among them:

[0034] The comonomers of the first copolymer include 20.6 wt% of the first monomer, 29.1 wt% of the second monomer, 16.1 wt% of the third monomer (acrylic acid), and 34.2 wt% of the fourth monomer. Among them, the first monomer is Tween 85, that is, polyoxyethylene (20) sorbitan trioleate, which has the structure of formula (1).

[0035]

[0036] Wherein: R1, R2 and R4 are -C(=O)-(CH2)7CH=CH(CH2)7CH3, R3 is H; the statistical average value of a + b + c + d is about 20.

[0037] The comonomers of the second copolymer include the fifth monomer and the seventh monomer.

[0038] This embodiment also provides a method for preparing an aqueous acrylic dispersion, comprising the following steps:

[0039] Nitrogen is introduced into the reaction vessel, the organic solvent (54.0 g of propylene glycol monobutyl ether) is added to the reaction vessel and stirred to raise the temperature to 145 °C. The fifth monomer (72.0 g of 2-hydroxyethyl methacrylate), the seventh monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate), and the initiator (7.0 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a uniform speed within 193 min, while maintaining the reaction temperature at 145 °C. After the dropping is completed, keep the temperature for 60 minutes. The first monomer (12.0 g of Tween 85), the second monomer (17.0 g of 2-hydroxyethyl methacrylate), the third monomer (9.4 g of acrylic acid), the fourth monomer (15.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate), and the initiator (1.7 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a uniform speed within 47 min, while maintaining the reaction temperature at 145 °C. After the dropping is completed, keep the temperature at this temperature for 180 minutes. Cool down to about 90 °C, add 9.3 g of N,N-dimethylethanolamine, and stir for 15 min. Slowly add 309.0 g of deionized water dropwise under high-speed stirring, and it is added dropwise in about 2 hours to obtain an aqueous acrylic dispersion with a milky white appearance.

[0040] The aqueous acrylic dispersion of this example is mainly synthesized by a two-stage method. During the heat preservation reaction in the first stage, the fifth monomer (72.0 g of 2-hydroxyethyl methacrylate) and the seventh monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate) are copolymerized to synthesize the second copolymer; during the heat preservation reaction in the second stage, the first monomer (12.0 g of Tween 85), the second monomer (17.0 g of 2-hydroxyethyl methacrylate), the third monomer (9.4 g of acrylic acid) and the fourth monomer (15.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate) are copolymerized to synthesize the first copolymer.

[0041] The solid content of the aqueous acrylic dispersion of this example is 45 wt%, the acid value of the solid content is 24 mg KOH / g, the hydroxyl value of the solid content is 127 mg KOH / g, the neutralization degree is 80%, and the first monomer accounts for 4.0 wt% of the solid content of the aqueous acrylic dispersion.

[0042] The aqueous acrylic dispersion of this example has no obvious precipitation and stratification after being stored in an oven at 50 °C for 2 weeks.

[0043] Example 2

[0044] This example provides an aqueous acrylic dispersion, which includes an organic solvent, a first copolymer, a second copolymer, a neutralizing agent and deionized water. Among them:

[0045] The copolymerization monomers of the first copolymer include 7.0 wt% of the first monomer, 34.1 wt% of the second monomer, 18.8 wt% of the third monomer, and 40.1 wt% of the fourth monomer. Among them, the first monomer is Tween 85 (the same as in Example 1), that is, polyoxyethylene (20) sorbitan trioleate.

[0046] The copolymerization monomers of the second copolymer include the fifth monomer and the seventh monomer.

[0047] The preparation method of the aqueous acrylic dispersion of this example includes the following steps:

[0048] Nitrogen is introduced into the reaction vessel. An organic solvent (54.0 g of propylene glycol butyl ether) is added to the reaction vessel and stirred while heating up to 145 °C. The fifth monomer (72.0 g of 2-hydroxyethyl methacrylate), the seventh monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate), and an initiator (7.0 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a uniform speed within 193 min, maintaining the reaction temperature at 145 °C. After the dropping is completed, keep the temperature for 60 minutes. The first monomer (3.5 g of Tween 85), the second monomer (17.0 g of 2-hydroxyethyl methacrylate), the third monomer (9.4 g of acrylic acid), the fourth monomer (15.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate), and an initiator (1.7 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a uniform speed within 47 min, maintaining the reaction temperature at 145 °C. After the dropping is completed, keep the temperature at this temperature for 180 minutes. Cool down to about 90 °C, add 9.3 g of N,N-dimethylethanolamine, and stir for 15 min. Slowly add 298.0 g of deionized water dropwise under high-speed stirring, and finish the dropping in about 2 hours to obtain an aqueous acrylic dispersion with a milky white appearance.

[0049] The aqueous acrylic dispersion of this example is mainly synthesized by a two-stage method. During the heat preservation reaction process of the first stage, the fifth monomer (72.0 g of 2-hydroxyethyl methacrylate) and the seventh monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate) copolymerize to synthesize the second copolymer; during the heat preservation reaction process of the second stage, the first monomer (3.5 g of Tween 85), the second monomer (17.0 g of 2-hydroxyethyl methacrylate), the third monomer (9.4 g of acrylic acid), and the fourth monomer (15.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate) copolymerize to synthesize the first copolymer.

[0050] The solid content of the aqueous acrylic dispersion of this example is 45 wt%, the solid acid value is 25 mg KOH / g, the solid hydroxyl value is 130 mg KOH / g, the neutralization degree is 80%, and the first monomer accounts for 1.2 wt% of the solid content of the aqueous acrylic dispersion.

[0051] The aqueous acrylic dispersion of this example has no obvious precipitation and stratification after being stored in an oven at 50 °C for 2 weeks.

[0052] Example 3

[0053] This example provides an aqueous acrylic dispersion, which includes an organic solvent, a first copolymer P1, a second copolymer P2, a neutralizing agent, and deionized water. Among them:

[0054] The comonomers of the first copolymer P1 include 16.9 wt% of the first monomer M1a, 30.4 wt% of the second monomer M2a, 52.7 wt% of the fourth monomer M4a, and do not contain the third monomer. Among them, the first monomer M1a is Tween 85 (the same as in Example 1), that is, polyoxyethylene (20) sorbitan trioleate.

[0055] The comonomers of the second copolymer P2 include 34.2 wt% of the first monomer M1b, 29.1 wt% of the second monomer M2b, 16.1 wt% of the third monomer M3b, and 20.6 wt% of the fourth monomer M4b. Among them, the first monomer M1b is Tween 85 (the same as in Example 1), that is, polyoxyethylene (20) sorbitan trioleate.

[0056] The preparation method of the aqueous acrylic dispersion of this example includes the following steps:

[0057] Nitrogen is introduced into the reaction vessel, and the organic solvent (54.0 g of propylene glycol butyl ether) is added to the reaction vessel and stirred to raise the temperature to 145 °C. The first monomer M1a (40.0 g of Tween 85), the second monomer M2a (72.0 g of 2-hydroxyethyl methacrylate), the fourth monomer M4a (58.0 g of methyl methacrylate, 35.0 g of styrene, 22.0 g of isobutyl methacrylate, 10.0 g of n-butyl acrylate), and the initiator (7.0 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a constant speed within 193 min, keeping the reaction temperature at 145 °C. After the dropping is completed, keep the temperature for 60 minutes. The first monomer M1b (20.0 g of Tween 85), the second monomer M2b (17.0 g of 2-hydroxyethyl methacrylate), the third monomer M3b (9.4 g of acrylic acid), the fourth monomer M4b (12.0 g of methyl methacrylate), and the initiator (1.7 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a constant speed within 47 min, keeping the reaction temperature at 145 °C. After the dropping is completed, keep the temperature at this temperature for 180 minutes. Cool down to about 90 °C, add 9.3 g of N,N-dimethylethanolamine, and stir for 15 min. Slowly add 309.0 g of deionized water dropwise under high-speed stirring, and finish the dropping in about 2 hours to obtain an aqueous acrylic dispersion with a milky white appearance.

[0058] The aqueous acrylic dispersion of this example is mainly synthesized by a two-stage method. During the heat preservation reaction in the first stage, the first monomer M1a (40.0 g of Tween 85), the second monomer M2a (72.0 g of 2-hydroxyethyl methacrylate), and the fourth monomer M4a (58.0 g of methyl methacrylate, 35.0 g of styrene, 22.0 g of isobutyl methacrylate, 10.0 g of n-butyl acrylate) are copolymerized to synthesize the first copolymer P1; during the heat preservation reaction in the second stage, the first monomer M1b (20.0 g of Tween 85), the second monomer M2b (17.0 g of 2-hydroxyethyl methacrylate), the third monomer M3b (9.4 g of acrylic acid), and the fourth monomer M4b (12.0 g of methyl methacrylate) are copolymerized to synthesize the first copolymer P2.

[0059] The solid content of the aqueous acrylic dispersion of this example is 45 wt%, the acid value of the solid content is 24 mg KOH / g, the hydroxyl value of the solid content is 132 mg KOH / g, the neutralization degree is 80%, and the first monomer (the total amount of the first monomer M1a + the first monomer M1b) accounts for 19.7 wt% of the solid content of the aqueous acrylic dispersion.

[0060] The aqueous acrylic dispersion of this example has no obvious precipitation and stratification after being stored in an oven at 50 °C for 2 weeks.

[0061] Example 4

[0062] This example provides an aqueous acrylic dispersion, which includes an organic solvent, a first copolymer, a second copolymer, a neutralizing agent, and deionized water. Among them:

[0063] The copolymerization monomers of the first copolymer include 5.1 wt% of the first monomer, 30.4 wt% of the second monomer, 64.5 wt% of the fourth monomer, and do not contain the third monomer. Among them, the first monomer is Tween 85 (the same as in Example 1), that is, polyoxyethylene (20) sorbitan trioleate.

[0064] The copolymerization monomers of the second copolymer include a fifth monomer, a sixth monomer, and a seventh monomer.

[0065] The preparation method of the aqueous acrylic dispersion of this example includes the following steps:

[0066] Nitrogen is introduced into the reaction vessel. An organic solvent (54.0 g of propylene glycol butyl ether) is added to the reaction vessel and stirred while heating up to 145 °C. The first monomer (12.0 g of Tween 85), the second monomer (72.0 g of 2-hydroxyethyl methacrylate), the fourth monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 18.0 g of n-butyl acrylate), and the initiator (7.0 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a constant speed within 193 min. The reaction temperature is maintained at 145 °C. After the dropping is completed, keep the temperature for 60 minutes. The fifth monomer (17.0 g of 2-hydroxyethyl methacrylate), the sixth monomer (9.4 g of acrylic acid), the seventh monomer (20.0 g of methyl methacrylate, 12.0 g of n-butyl acrylate), and the initiator (1.7 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a constant speed within 47 min. The reaction temperature is maintained at 145 °C. After the dropping is completed, keep the temperature at this temperature for 180 minutes. Cool down to about 90 °C, add 9.3 g of N,N-dimethylethanolamine, and stir for 15 min. Slowly add 309.0 g of deionized water dropwise under high-speed stirring, and finish dropping in about 2 hours to obtain a milky white aqueous acrylic dispersion.

[0067] The aqueous acrylic dispersion of this example is mainly synthesized by a two-stage method. During the heat preservation reaction process of the first stage, the first monomer (12.0 g of Tween 85), the second monomer (72.0 g of 2-hydroxyethyl methacrylate), and the fourth monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 18.0 g of n-butyl acrylate) copolymerize to synthesize the first copolymer; during the heat preservation reaction process of the second stage, the fifth monomer (17.0 g of 2-hydroxyethyl methacrylate), the sixth monomer (9.4 g of acrylic acid), and the seventh monomer (20.0 g of methyl methacrylate, 12.0 g of n-butyl acrylate) copolymerize to synthesize the second copolymer.

[0068] The solid content of the aqueous acrylic dispersion of this example is 45 wt%, the acid value of the solid content is 24 mg KOH / g, the hydroxyl value of the solid content is 127 mg KOH / g, the neutralization degree is 80%, and the first monomer accounts for 4.0 wt% of the solid content of the aqueous acrylic dispersion.

[0069] The aqueous acrylic dispersion of this example has no obvious precipitation and stratification after being stored in an oven at 50 °C for 2 weeks.

[0070] Example 5

[0071] This example provides an aqueous acrylic dispersion, which includes an organic solvent, a first copolymer, a second copolymer, a neutralizing agent, and deionized water. Among them:

[0072] The comonomers of the first copolymer include 20.6 wt% of the first monomer, 29.1 wt% of the second monomer, 16.1 wt% of the third monomer, and 34.2 wt% of the fourth monomer. Among them, the first monomer is Tween 80, that is, polyoxyethylene (20) sorbitan monooleate, having the structure of formula (1).

[0073]

[0074] Wherein: R4 is -C(=O)-(CH2)7CH=CH(CH2)7CH3, and R1, R2, and R3 are H; the statistical average value of a + b + c + d is about 20.

[0075] The comonomers of the second copolymer include the fifth monomer and the seventh monomer.

[0076] The preparation method of the aqueous acrylic dispersion of this example includes the following steps:

[0077] Nitrogen is introduced into the reaction vessel, the organic solvent (54.0 g of propylene glycol butyl ether) is added to the reaction vessel and stirred to raise the temperature to 145 °C. The fifth monomer (72.0 g of 2-hydroxyethyl methacrylate), the seventh monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate), and the initiator (7.0 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a constant speed within 193 min, keeping the reaction temperature at 145 °C. After the dropping is completed, keep the temperature for 60 minutes. The first monomer (12.0 g of Tween 80), the second monomer (17.0 g of 2-hydroxyethyl methacrylate), the third monomer (9.4 g of acrylic acid), the fourth monomer (15.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate), and the initiator (1.7 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a constant speed within 47 min, keeping the reaction temperature at 145 °C. After the dropping is completed, keep the temperature at this temperature for 180 minutes. Cool down to about 90 °C, add 9.3 g of N,N-dimethylethanolamine, and stir for 15 min. Slowly add 309.0 g of deionized water dropwise under high-speed stirring, and finish the dropping in about 2 hours to obtain an aqueous acrylic dispersion with a milky white appearance.

[0078] The aqueous acrylic dispersion of this example is mainly synthesized by a two-stage method. During the heat preservation reaction in the first stage, the fifth monomer (72.0 g of 2-hydroxyethyl methacrylate) and the seventh monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate) are copolymerized to synthesize the second copolymer; during the heat preservation reaction in the second stage, the first monomer (12.0 g of Tween 80), the second monomer (17.0 g of 2-hydroxyethyl methacrylate), the third monomer (9.4 g of acrylic acid) and the fourth monomer (15.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate) are copolymerized to synthesize the first copolymer.

[0079] The solid content of the aqueous acrylic dispersion of this example is 45 wt%, the solid acid value is 24 mg KOH / g, the solid hydroxyl value is 131 mg KOH / g, the neutralization degree is 80%, and the first monomer accounts for 4.0 wt% of the solid content of the aqueous acrylic dispersion.

[0080] The aqueous acrylic dispersion of this example has no obvious precipitation and stratification after being stored in an oven at 50 °C for 2 weeks.

[0081] Example 6

[0082] This example provides an aqueous acrylic dispersion, which includes an organic solvent, a first copolymer, a second copolymer, a neutralizing agent and deionized water. Among them:

[0083] The copolymerization monomers of the first copolymer include 20.6 wt% of the first monomer, 29.1 wt% of the second monomer, 16.1 wt% of the third monomer, and 34.2 wt% of the fourth monomer. Among them, the first monomer is Span 85, that is, sorbitan trioleate, and has the structure of formula (1)

[0084]

[0085] Among them: R1, R2 and R4 are -C(=O)-(CH2)7CH=CH(CH2)7CH3, R3 is H; the statistical average value of a + b + c + d is 0.

[0086] The copolymerization monomers of the second copolymer include the fifth monomer and the seventh monomer.

[0087] The preparation method of the aqueous acrylic dispersion of this example includes the following steps:

[0088] Nitrogen was introduced into the reaction vessel. An organic solvent (54.0 g of propylene glycol butyl ether) was added to the reaction vessel and stirred while heating up to 145 °C. The fifth monomer (72.0 g of 2-hydroxyethyl methacrylate), the seventh monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate), and an initiator (7.0 g of di-tert-butyl peroxide) were mixed evenly and added dropwise into the reaction vessel at a constant rate within 193 min, maintaining the reaction temperature at 145 °C. After the dropping was completed, it was kept warm for 60 minutes. The first monomer (12.0 g of Span 85), the second monomer (17.0 g of 2-hydroxyethyl methacrylate), the third monomer (9.4 g of acrylic acid), the fourth monomer (15.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate), and an initiator (1.7 g of di-tert-butyl peroxide) were mixed evenly and added dropwise into the reaction vessel at a constant rate within 47 min, maintaining the reaction temperature at 145 °C. After the dropping was completed, it was kept warm at this temperature for 180 minutes. The temperature was lowered to about 90 °C, 9.3 g of N,N-dimethylethanolamine was added, and it was stirred for 15 min. Deionized water (309.0 g) was slowly added dropwise under high-speed stirring, and the dropping was completed in about 2 hours to obtain a water-based acrylic dispersion with a milky white appearance.

[0089] The water-based acrylic dispersion in this example was mainly synthesized by a two-stage method. During the heat preservation reaction in the first stage, the fifth monomer (72.0 g of 2-hydroxyethyl methacrylate) and the seventh monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate) copolymerized to synthesize the second copolymer; during the heat preservation reaction in the second stage, the first monomer (12.0 g of Span 85), the second monomer (17.0 g of 2-hydroxyethyl methacrylate), the third monomer (9.4 g of acrylic acid), and the fourth monomer (15.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate) copolymerized to synthesize the first copolymer.

[0090] The solid content of the water-based acrylic dispersion in this example was 45 wt%, the solid acid value was 24 mg KOH / g, the solid hydroxyl value was 128 mg KOH / g, the neutralization degree was 80%, and the first monomer accounted for 4.0 wt% of the solid content of the water-based acrylic dispersion.

[0091] The water-based acrylic dispersion in this example had no obvious precipitation and stratification after being stored in an oven at 50 °C for 2 weeks.

[0092] Example 7

[0093] This example provides a water-based acrylic dispersion, which includes an organic solvent, a first copolymer, a second copolymer, a neutralizing agent, and deionized water. Among them:

[0094] The comonomers of the first copolymer include 20.6 wt% of the first monomer, 29.1 wt% of the second monomer, 16.1 wt% of the third monomer, and 34.2 wt% of the fourth monomer. Among them, the first monomer is Span 80, that is, sorbitan monooleate, having the structure of formula (1).

[0095]

[0096] Wherein: R4 is -C(=O)-(CH2)7CH=CH(CH2)7CH3, and R1, R2, and R3 are H; the statistical average value of a + b + c + d is 0.

[0097] The comonomers of the second copolymer include the fifth monomer and the seventh monomer.

[0098] The preparation method of the aqueous acrylic dispersion in this example includes the following steps:

[0099] Nitrogen is introduced into the reaction vessel, and the organic solvent (54.0 g of propylene glycol butyl ether) is added to the reaction vessel and stirred to raise the temperature to 145 °C. The fifth monomer (72.0 g of 2-hydroxyethyl methacrylate), the seventh monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate), and the initiator (7.0 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a constant speed within 193 min, maintaining the reaction temperature at 145 °C. After the addition is completed, keep the temperature for 60 minutes. The first monomer (12.0 g of Span 80), the second monomer (17.0 g of 2-hydroxyethyl methacrylate), the third monomer (9.4 g of acrylic acid), the fourth monomer (15.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate), and the initiator (1.7 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a constant speed within 47 min, maintaining the reaction temperature at 145 °C. After the addition is completed, keep the temperature at this temperature for 180 minutes. Cool down to about 90 °C, add 9.3 g of N,N-dimethylethanolamine, and stir for 15 min. Slowly add 309.0 g of deionized water dropwise under high-speed stirring, and it is added dropwise in about 2 hours to obtain an aqueous acrylic dispersion with a milky white appearance.

[0100] The aqueous acrylic dispersion of this example is mainly synthesized by a two-stage method. During the heat preservation reaction in the first stage, the fifth monomer (72.0 g of 2-hydroxyethyl methacrylate) and the seventh monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate) are copolymerized to synthesize the second copolymer; during the heat preservation reaction in the second stage, the first monomer (12.0 g of Span 80), the second monomer (17.0 g of 2-hydroxyethyl methacrylate), the third monomer (9.4 g of acrylic acid) and the fourth monomer (15.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate) are copolymerized to synthesize the first copolymer.

[0101] The solid content of the aqueous acrylic dispersion of this example is 45 wt%, the acid value of the solid content is 24 mg KOH / g, the hydroxyl value of the solid content is 131 mg KOH / g, the neutralization degree is 80%, and the first monomer accounts for 4.0 wt% of the solid content of the aqueous acrylic dispersion.

[0102] The aqueous acrylic dispersion of this example has no obvious precipitation and stratification after being stored in an oven at 50 °C for 2 weeks.

[0103] Example 8

[0104] This example provides an aqueous acrylic dispersion, which includes an organic solvent, a first copolymer, a second copolymer, a neutralizing agent and deionized water. Among them:

[0105] The copolymerization monomers of the first copolymer include 20.6 wt% of the first monomer, 29.1 wt% of the second monomer, 16.1 wt% of the third monomer, and 34.2 wt% of the fourth monomer. Among them, the first monomer is polyoxyethylene (38) sorbitan trioleate, having the structure of formula (1)

[0106]

[0107] Among them: R1, R2 and R4 are -C(=O)-(CH2)7CH=CH(CH2)7CH3, R3 is H; the statistical average value of a + b + c + d is about 38.

[0108] The specific synthesis method of polyoxyethylene (38) sorbitan trioleate is as follows:

[0109] Preheat 957.7 g of Span 85 (sorbitan trioleate) and put it into the reaction kettle. Add 2.0 g of sodium hydroxide under stirring, and evacuate to remove water. After dehydration is completed, displace the air in the kettle with nitrogen, heat up to 140 °C and start to introduce 1672 g of ethylene oxide, control the reaction pressure at 2 - 3 atmospheres, and react for 6 - 10 h. Add an appropriate amount of glacial acetic acid to neutralize sodium hydroxide in the reaction system and adjust the pH to 6 - 7. Remove volatile impurities by vacuum distillation. Wash the product with an appropriate amount of deionized water and separate the organic phase. Dry the product to obtain 2420 g of a pale yellow to amber viscous liquid, which is polyoxyethylene (38) sorbitan trioleate.

[0110] The comonomers of the second copolymer include the fifth monomer and the seventh monomer.

[0111] The preparation method of the aqueous acrylic dispersion of this example includes the following steps:

[0112] Pass nitrogen into the reaction vessel, add the organic solvent (54.0 g of propylene glycol butyl ether) into the reaction vessel and stir to heat up to 145 °C. Mix the fifth monomer (72.0 g of 2-hydroxyethyl methacrylate), the seventh monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate), and the initiator (7.0 g of di-tert-butyl peroxide) evenly, and drop them into the reaction vessel at a uniform speed within 193 min, keeping the reaction temperature at 145 °C. After dropping, keep the temperature for 60 minutes. Mix the first monomer (12.0 g of polyoxyethylene (38) sorbitan trioleate), the second monomer (17.0 g of 2-hydroxyethyl methacrylate), the third monomer (9.4 g of acrylic acid), the fourth monomer (15.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate), and the initiator (1.7 g of di-tert-butyl peroxide) evenly, and drop them into the reaction vessel at a uniform speed within 47 min, keeping the reaction temperature at 145 °C. After dropping, keep the temperature at this temperature for 180 minutes. Cool down to about 90 °C, add 9.3 g of N,N-dimethylethanolamine, and stir for 15 min. Slowly drop 309.0 g of deionized water under high-speed stirring, and finish dropping in about 2 hours to obtain an aqueous acrylic dispersion with a milky white appearance.

[0113] The aqueous acrylic dispersion of this example is mainly synthesized by a two-stage method. During the heat preservation reaction in the first stage, the fifth monomer (72.0 g of 2-hydroxyethyl methacrylate) and the seventh monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate) are copolymerized to synthesize the second copolymer; during the heat preservation reaction in the second stage, the first monomer (12.0 g of polyoxyethylene (38) sorbitan trioleate), the second monomer (17.0 g of 2-hydroxyethyl methacrylate), the third monomer (9.4 g of acrylic acid) and the fourth monomer (15.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate) are copolymerized to synthesize the first copolymer.

[0114] The solid content of the aqueous acrylic dispersion of this example is 45 wt%, the acid value of the solid content is 24 mg KOH / g, the hydroxyl value of the solid content is 127 mg KOH / g, the neutralization degree is 80%, and the first monomer accounts for 4.0 wt% of the solid content of the aqueous acrylic dispersion.

[0115] The aqueous acrylic dispersion of this example has no obvious precipitation and stratification after being stored in an oven at 50 °C for 2 weeks.

[0116] Example 9

[0117] This example provides an aqueous acrylic dispersion, which includes an organic solvent, a first copolymer, a second copolymer, a neutralizing agent and deionized water. Among them:

[0118] The copolymerization monomers of the first copolymer include 21.8 wt% of the first monomer, 30.9 wt% of the second monomer, 10.9 wt% of the third monomer (acrylic acid), and 36.4 wt% of the fourth monomer. Among them, the first monomer is Tween 85 (the same as in Example 1), that is, polyoxyethylene (20) sorbitan trioleate.

[0119] The copolymerization monomers of the second copolymer include the fifth monomer and the seventh monomer.

[0120] This example also provides a preparation method of an aqueous acrylic dispersion, which includes the following steps:

[0121] Nitrogen is introduced into the reaction vessel, and the organic solvent (54.0 g of propylene glycol butyl ether) is added to the reaction vessel and stirred while heating up to 145 °C. The fifth monomer (72.0 g of 2-hydroxyethyl methacrylate), the seventh monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate), and the initiator (7.0 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a uniform speed within 193 min, maintaining the reaction temperature at 145 °C. After the dropping is completed, keep the temperature for 60 minutes. The first monomer (12.0 g of Tween 85), the second monomer (17.0 g of 2-hydroxyethyl methacrylate), the third monomer (6.0 g of acrylic acid), the fourth monomer (15.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate), and the initiator (1.7 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a uniform speed within 47 min, maintaining the reaction temperature at 145 °C. After the dropping is completed, keep the temperature at this temperature for 180 minutes. Cool down to about 90 °C, add 7.5 g of N,N-dimethylethanolamine, and stir for 15 min. Slowly add 306.0 g of deionized water dropwise under high-speed stirring, and finish the dropping in about 2 hours to obtain a water-based acrylic dispersion with a milky white appearance.

[0122] The water-based acrylic dispersion of this example is mainly synthesized by a two-stage method. During the heat preservation reaction process of the first stage, the fifth monomer (72.0 g of 2-hydroxyethyl methacrylate) and the seventh monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate) copolymerize to synthesize the second copolymer; during the heat preservation reaction process of the second stage, the first monomer (12.0 g of Tween 85), the second monomer (17.0 g of 2-hydroxyethyl methacrylate), the third monomer (6.0 g of acrylic acid), and the fourth monomer (15.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate) copolymerize to synthesize the first copolymer.

[0123] The solid content of the water-based acrylic dispersion of this example is 45 wt%, the solid acid value is 15 mg KOH / g, the solid hydroxyl value is 129 mg KOH / g, the neutralization degree is 100%, and the first monomer accounts for 4.0 wt% of the solid content of the water-based acrylic dispersion.

[0124] The water-based acrylic dispersion of this example has no obvious precipitation and stratification after being stored in an oven at 50 °C for 2 weeks.

[0125] Example 10

[0126] This example provides a water-based acrylic dispersion, which includes an organic solvent, a first copolymer, a second copolymer, a neutralizing agent, and deionized water. Among them:

[0127] The comonomers of the first copolymer include 19.2 wt% of the first monomer, 27.2 wt% of the second monomer, 21.6 wt% of the third monomer (acrylic acid), and 32.0 wt% of the fourth monomer. Among them, the first monomer is Tween 85 (the same as in Example 1), that is, polyoxyethylene (20) sorbitan trioleate.

[0128] The comonomers of the second copolymer include the fifth monomer and the seventh monomer.

[0129] This example also provides a method for preparing an aqueous acrylic dispersion, which includes the following steps:

[0130] Nitrogen is introduced into the reaction vessel, and the organic solvent (54.0 g of propylene glycol monobutyl ether) is added to the reaction vessel and stirred to raise the temperature to 145°C. The fifth monomer (72.0 g of 2-hydroxyethyl methacrylate), the seventh monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate), and the initiator (7.0 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a constant speed within 193 min, while maintaining the reaction temperature at 145°C. After the dropping is completed, keep the temperature for 60 minutes. The first monomer (12.0 g of Tween 85), the second monomer (17.0 g of 2-hydroxyethyl methacrylate), the third monomer (13.5 g of acrylic acid), the fourth monomer (15.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate), and the initiator (1.7 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a constant speed within 47 min, while maintaining the reaction temperature at 145°C. After the dropping is completed, keep the temperature at this temperature for 180 minutes. Cool down to about 90°C, add 7.5 g of N,N-dimethylethanolamine, and stir for 15 min. Slowly add 365.0 g of deionized water dropwise under high-speed stirring, and complete the dropping in about 2 hours to obtain an aqueous acrylic dispersion with a milky white appearance.

[0131] The aqueous acrylic dispersion of this example is mainly synthesized by a two-stage method. During the heat preservation reaction in the first stage, the fifth monomer (72.0 g of 2-hydroxyethyl methacrylate) and the seventh monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate) copolymerize to synthesize the second copolymer; during the heat preservation reaction in the second stage, the first monomer (12.0 g of Tween 85), the second monomer (17.0 g of 2-hydroxyethyl methacrylate), the third monomer (13.5 g of acrylic acid), and the fourth monomer (15.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate) copolymerize to synthesize the first copolymer.

[0132] The solid content of the aqueous acrylic dispersion in this example is 42 wt%, the solid acid value is 34 mg KOH / g, the solid hydroxyl value is 126 mg KOH / g, the neutralization degree is 45%, and the first monomer accounts for 4.0 wt% of the solid content of the aqueous acrylic dispersion.

[0133] After being stored in an oven at 50 °C for 2 weeks, the aqueous acrylic dispersion in this example has no obvious precipitation and stratification.

[0134] Example 11

[0135] This example provides an aqueous acrylic dispersion, which includes an organic solvent, a first copolymer, a second copolymer, a neutralizing agent, and deionized water. Among them:

[0136] The copolymerization monomers of the first copolymer include 20.5 wt% of the first monomer, 12.0 wt% of the second monomer, 16.1 wt% of the third monomer (acrylic acid), and 51.4 wt% of the fourth monomer. Among them, the first monomer is Tween 85 (the same as in Example 1), that is, polyoxyethylene (20) sorbitan trioleate.

[0137] The copolymerization monomers of the second copolymer include a fifth monomer and a seventh monomer.

[0138] This example also provides a preparation method of an aqueous acrylic dispersion, which includes the following steps:

[0139] Nitrogen is introduced into the reaction vessel, the organic solvent (54.0 g of propylene glycol monobutyl ether) is added to the reaction vessel and stirred to raise the temperature to 145 °C. The fifth monomer (28.0 g of 2-hydroxyethyl methacrylate), the seventh monomer (72.0 g of methyl methacrylate, 45.0 g of styrene, 62.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate), and the initiator (7.0 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a constant speed within 193 min, keeping the reaction temperature at 145 °C. After the dropping is completed, keep the temperature for 60 minutes. The first monomer (12.0 g of Tween 85), the second monomer (7.0 g of 2-hydroxyethyl methacrylate), the third monomer (9.4 g of acrylic acid), the fourth monomer (20.0 g of methyl methacrylate, 10.0 g of n-butyl acrylate), and the initiator (1.7 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a constant speed within 47 min, keeping the reaction temperature at 145 °C. After the dropping is completed, keep the temperature at this temperature for 180 minutes. Cool down to about 90 °C, add 9.3 g of N,N-dimethylethanolamine, and stir for 15 min. Slowly add 309.0 g of deionized water dropwise under high-speed stirring, and finish the dropping in about 2 hours to obtain an aqueous acrylic dispersion with a milky white appearance.

[0140] The aqueous acrylic dispersion of this example is mainly synthesized by a two-stage method. During the heat preservation reaction in the first stage, the fifth monomer (28.0 g of 2-hydroxyethyl methacrylate) and the seventh monomer (72.0 g of methyl methacrylate, 45.0 g of styrene, 62.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate) are copolymerized to synthesize the second copolymer; during the heat preservation reaction in the second stage, the first monomer (12.0 g of Tween 85), the second monomer (7.0 g of 2-hydroxyethyl methacrylate), the third monomer (9.4 g of acrylic acid) and the fourth monomer (20.0 g of methyl methacrylate, 10.0 g of n-butyl acrylate) are copolymerized to synthesize the first copolymer.

[0141] The solid content of the aqueous acrylic dispersion of this example is 45 wt%, the acid value of the solid content is 24 mg KOH / g, the hydroxyl value of the solid content is 51 mg KOH / g, the neutralization degree is 80%, and the first monomer accounts for 4.0 wt% of the solid content of the aqueous acrylic dispersion.

[0142] The aqueous acrylic dispersion of this example has no obvious precipitation and stratification after being stored in an oven at 50 °C for 2 weeks.

[0143] Example 12

[0144] This example provides an aqueous acrylic dispersion, which includes an organic solvent, a first copolymer, a second copolymer, a neutralizing agent and deionized water. Among them:

[0145] The copolymerization monomers of the first copolymer include 20.6 wt% of the first monomer, 32.5 wt% of the second monomer, 16.1 wt% of the third monomer (acrylic acid), and 30.8 wt% of the fourth monomer. Among them, the first monomer is Tween 85 (the same as in Example 1), that is, polyoxyethylene (20) sorbitan trioleate.

[0146] The copolymerization monomers of the second copolymer include the fifth monomer and the seventh monomer.

[0147] This example also provides a preparation method of an aqueous acrylic dispersion, which includes the following steps:

[0148] Nitrogen is introduced into the reaction vessel. An organic solvent (54.0 g of propylene glycol butyl ether) is added to the reaction vessel and stirred while heating up to 145 °C. The fifth monomer (30.0 g of 4-hydroxybutyl acrylate, 69.0 g of 2-hydroxyethyl methacrylate), the seventh monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 33.0 g of isobutyl methacrylate, 12.0 g of n-butyl acrylate), and an initiator (7.0 g of di-tert-butyl peroxide) are mixed evenly and slowly added dropwise into the reaction vessel within 193 min, maintaining the reaction temperature at 145 °C. After the dropping is completed, keep the temperature for 60 minutes. The first monomer (12.0 g of Tween 85), the second monomer (5.0 g of 4-hydroxybutyl acrylate, 14.0 g of 2-hydroxyethyl methacrylate), the third monomer (9.4 g of acrylic acid), the fourth monomer (13.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate), and an initiator (1.7 g of di-tert-butyl peroxide) are mixed evenly and slowly added dropwise into the reaction vessel within 47 min, maintaining the reaction temperature at 145 °C. After the dropping is completed, keep the temperature at this temperature for 180 minutes. Cool down to about 90 °C, add 9.3 g of N,N-dimethylethanolamine, and stir for 15 min. While stirring at high speed, slowly add 309.0 g of deionized water, and finish adding in about 2 hours to obtain a milky white aqueous acrylic dispersion.

[0149] The aqueous acrylic dispersion of this example is mainly synthesized by a two-stage method. During the heat preservation reaction process of the first stage, the fifth monomer (30.0 g of 4-hydroxybutyl acrylate, 69.0 g of 2-hydroxyethyl methacrylate) and the seventh monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 33.0 g of isobutyl methacrylate, 12.0 g of n-butyl acrylate) copolymerize to synthesize the second copolymer; during the heat preservation reaction process of the second stage, the first monomer (12.0 g of Tween 85), the second monomer (5.0 g of 4-hydroxybutyl acrylate, 14.0 g of 2-hydroxyethyl methacrylate), the third monomer (9.4 g of acrylic acid), and the fourth monomer (13.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate) copolymerize to synthesize the first copolymer.

[0150] The solid content of the aqueous acrylic dispersion of this example is 45 wt%, the solid acid value is 24 mg KOH / g, the solid hydroxyl value is 164 mg KOH / g, the neutralization degree is 80%, and the first monomer accounts for 4.0 wt% of the solid content of the aqueous acrylic dispersion.

[0151] The aqueous acrylic dispersion of this example has no obvious precipitation and stratification after being stored in an oven at 50 °C for 2 weeks.

[0152] Comparative Example 1

[0153] This comparative example provides an aqueous acrylic dispersion, which includes an organic solvent, a second copolymer Q1, a second copolymer Q2, a neutralizing agent, and deionized water, and does not contain a first copolymer. Among them:

[0154] The comonomers of the second copolymer Q1 include a fifth monomer M5a and a seventh monomer M7a.

[0155] The comonomers of the second copolymer Q2 include a fifth monomer M5b, a sixth monomer M6b, and a seventh monomer M7b.

[0156] This comparative example also provides a preparation method of the aqueous acrylic dispersion, which includes the following steps:

[0157] Nitrogen is introduced into the reaction vessel, and the organic solvent (54.0 g of propylene glycol butyl ether) is added to the reaction vessel and stirred and heated to 145 °C. The fifth monomer M5a (72.0 g of 2-hydroxyethyl methacrylate), the seventh monomer M7a (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate), and the initiator (7.0 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a constant speed within 193 min, keeping the reaction temperature at 145 °C. After the dropping is completed, keep the temperature for 60 minutes. The fifth monomer M5b (17.0 g of 2-hydroxyethyl methacrylate), the sixth monomer M6b (9.4 g of acrylic acid), the seventh monomer M7b (15.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate), and the initiator (1.7 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a constant speed within 47 min, keeping the reaction temperature at 145 °C. After the dropping is completed, keep the temperature at this temperature for 180 minutes. Cool down to about 90 °C, add 9.3 g of N,N-dimethylethanolamine, and stir for 15 min. Slowly add 294.0 g of deionized water dropwise under high-speed stirring, and finish dropping in about 2 hours to obtain an aqueous acrylic dispersion with a milky white appearance.

[0158] The aqueous acrylic dispersion of this comparative example is mainly synthesized by a two-stage method. During the heat preservation reaction process of the first stage, the fifth monomer M5a (72.0 g of 2-hydroxyethyl methacrylate) and the seventh monomer M7a (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate) copolymerize to synthesize the second copolymer Q1; during the heat preservation reaction process of the second stage, the fifth monomer M5b (17.0 g of 2-hydroxyethyl methacrylate), the sixth monomer M6b (9.4 g of acrylic acid), and the seventh monomer M7b (15.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate) copolymerize to synthesize the second copolymer Q2.

[0159] The solid content of the aqueous acrylic dispersion in this comparative example is 45 wt%, the solid acid value is 25 mg KOH / g, the solid hydroxyl value is 131 mg KOH / g, and the neutralization degree is 80%.

[0160] After heat storage in an oven at 50 °C for 2 weeks, the aqueous acrylic dispersion in this comparative example has no obvious precipitation and stratification.

[0161] Comparative Example 2

[0162] This comparative example provides an aqueous acrylic dispersion, which includes an organic solvent, a first copolymer, a second copolymer, a neutralizing agent, and deionized water. Among them:

[0163] The copolymerization monomers of the first copolymer include 22.2 wt% of a first monomer, 31.5 wt% of a second monomer, 9.3 wt% of a third monomer, and 37.0 wt% of a fourth monomer. Among them, the first monomer is Tween 85 (the same as in Example 1), that is, polyoxyethylene (20) sorbitan trioleate.

[0164] The copolymerization monomers of the second copolymer include a fifth monomer and a seventh monomer.

[0165] The preparation method of the aqueous acrylic dispersion in this comparative example includes the following steps:

[0166] Nitrogen is introduced into the reaction vessel, and the organic solvent (54.0 g of propylene glycol monobutyl ether) is added to the reaction vessel and stirred to raise the temperature to 145 °C. The fifth monomer (72.0 g of 2-hydroxyethyl methacrylate), the seventh monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate), and the initiator (7.0 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a constant speed within 193 min, maintaining the reaction temperature at 145 °C. After the addition is completed, keep the temperature for 60 minutes. The first monomer (12.0 g of Tween 85), the second monomer (17.0 g of 2-hydroxyethyl methacrylate), the third monomer (5.0 g of acrylic acid), the fourth monomer (15.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate), and the initiator (1.7 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a constant speed within 47 min, maintaining the reaction temperature at 145 °C. After the addition is completed, keep the temperature at this temperature for 180 minutes. Cool down to about 90 °C, add 6.0 g of N,N-dimethylethanolamine, and stir for 15 min. Slowly add 307.0 g of deionized water dropwise under high-speed stirring, and finish adding in about 2 hours to obtain an aqueous acrylic dispersion with a milky white appearance.

[0167] The aqueous acrylic dispersion of this comparative example was mainly synthesized by a two-stage method. During the heat preservation reaction in the first stage, the fifth monomer (72.0 g of 2-hydroxyethyl methacrylate) and the seventh monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate) were copolymerized to synthesize the second copolymer; during the heat preservation reaction in the second stage, the first monomer (12.0 g of Tween 85), the second monomer (17.0 g of 2-hydroxyethyl methacrylate), the third monomer (5.0 g of acrylic acid) and the fourth monomer (15.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate) were copolymerized to synthesize the first copolymer.

[0168] The solid content of the aqueous acrylic dispersion of this comparative example was 45 wt%, the solid acid value was 13 mg KOH / g, the solid hydroxyl value was 129 mg KOH / g, the neutralization degree was 97%, and the first monomer accounted for 4.0 wt% of the solid content of the aqueous acrylic dispersion.

[0169] A large amount of precipitation occurred after the aqueous acrylic dispersion of this comparative example was stored in an oven at 50 °C for 1 day, and a stable aqueous dispersion could not be obtained.

[0170] Comparative Example 3

[0171] This comparative example provides an aqueous acrylic dispersion, which includes an organic solvent, a first copolymer, a second copolymer, a neutralizing agent and deionized water. Among them:

[0172] The copolymerization monomers of the first copolymer include 18.5 wt% of the first monomer, 26.1 wt% of the second monomer, 24.6 wt% of the third monomer, and 30.8 wt% of the fourth monomer. Among them, the first monomer is Tween 85 (the same as in Example 1), that is, polyoxyethylene (20) sorbitan trioleate.

[0173] The copolymerization monomers of the second copolymer include the fifth monomer and the seventh monomer.

[0174] The preparation method of the aqueous acrylic dispersion of this comparative example includes the following steps:

[0175] Nitrogen is introduced into the reaction vessel. An organic solvent (54.0 g of propylene glycol butyl ether) is added to the reaction vessel and stirred while heating up to 145 °C. The fifth monomer (72.0 g of 2-hydroxyethyl methacrylate), the seventh monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate), and an initiator (7.0 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a constant rate within 193 min, maintaining the reaction temperature at 145 °C. After the dropping is completed, keep the temperature for 60 minutes. The first monomer (12.0 g of Tween 85), the second monomer (17.0 g of 2-hydroxyethyl methacrylate), the third monomer (16.0 g of acrylic acid), the fourth monomer (15.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate), and an initiator (1.7 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a constant rate within 47 min, maintaining the reaction temperature at 145 °C. After the dropping is completed, keep the temperature at this temperature for 180 minutes. Cool down to about 90 °C, add 8.0 g of N,N-dimethylethanolamine, and stir for 15 min. Slowly add 404.0 g of deionized water dropwise under high-speed stirring, and finish the dropping in about 2 hours to obtain an aqueous acrylic dispersion with a milky white appearance.

[0176] The aqueous acrylic dispersion of this comparative example is mainly synthesized by a two-stage method. During the heat preservation reaction process of the first stage, the fifth monomer (72.0 g of 2-hydroxyethyl methacrylate) and the seventh monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate) copolymerize to synthesize the second copolymer; during the heat preservation reaction process of the second stage, the first monomer (12.0 g of Tween 85), the second monomer (17.0 g of 2-hydroxyethyl methacrylate), the third monomer (5.0 g of acrylic acid), and the fourth monomer (15.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate) copolymerize to synthesize the first copolymer.

[0177] The solid content of the aqueous acrylic dispersion of this comparative example is 40 wt%, the solid content acid value is 40 mg KOH / g, the solid content hydroxyl value is 125 mg KOH / g, the neutralization degree is 40%, and the first monomer accounts for 3.9 wt% of the solid content of the aqueous acrylic dispersion.

[0178] The aqueous acrylic dispersion of this comparative example has no obvious precipitation and stratification after being stored in an oven at 50 °C for 2 weeks.

[0179] Comparative Example 4

[0180] This comparative example provides an aqueous acrylic dispersion, which includes an organic solvent, a second copolymer, a third copolymer, a neutralizing agent, and deionized water. Among them:

[0181] The comonomers of the second copolymer include a fifth monomer and a seventh monomer.

[0182] The comonomers of the third copolymer include a nonionic reactive emulsifier ER-10, a second monomer, a third monomer, and a fourth monomer.

[0183] The preparation method of the aqueous acrylic dispersion of this comparative example includes the following steps:

[0184] Nitrogen is introduced into the reaction vessel, an organic solvent (54.0 g of butyl carbitol) is added to the reaction vessel and stirred to raise the temperature to 145 °C. The fifth monomer (72.0 g of 2-hydroxyethyl methacrylate), the seventh monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate), and an initiator (7.0 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a constant speed within 193 min, maintaining the reaction temperature at 145 °C. After the dropping is completed, keep the temperature for 60 minutes. 12.0 g of ER-10 (ADEKA, Japan, nonionic reactive emulsifier), the second monomer (17.0 g of 2-hydroxyethyl methacrylate), the third monomer (16.0 g of acrylic acid), the fourth monomer (15.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate), and an initiator (1.7 g of di-tert-butyl peroxide) are mixed evenly and added dropwise into the reaction vessel at a constant speed within 47 min, maintaining the reaction temperature at 145 °C. After the dropping is completed, keep the temperature at this temperature for 180 minutes. Cool down to about 90 °C, add 8.0 g of N,N-dimethylethanolamine, and stir for 15 min. Slowly add 404.0 g of deionized water dropwise under high-speed stirring, and finish the dropping in about 2 hours to obtain an aqueous acrylic dispersion with a milky white appearance.

[0185] The aqueous acrylic dispersion of this comparative example is mainly synthesized by a two-stage method. During the heat preservation reaction process of the first stage, the fifth monomer (72.0 g of 2-hydroxyethyl methacrylate) and the seventh monomer (58.0 g of methyl methacrylate, 35.0 g of styrene, 42.0 g of isobutyl methacrylate, 30.0 g of n-butyl acrylate) copolymerize to synthesize the second copolymer; during the heat preservation reaction process of the second stage, 12.0 g of ER-10 (ADEKA, Japan, nonionic reactive emulsifier), the second monomer (17.0 g of 2-hydroxyethyl methacrylate), the third monomer (16.0 g of acrylic acid), the fourth monomer (15.0 g of methyl methacrylate, 5.0 g of n-butyl acrylate), and an initiator (1.7 g of di-tert-butyl peroxide) copolymerize to synthesize the third copolymer.

[0186] The solid content of the aqueous acrylic dispersion in this comparative example is 40 wt%, the solid acid value is 40 mg KOH / g, the solid hydroxyl value is 125 mg KOH / g, the neutralization degree is 80%, and the first monomer accounts for 3.9 wt% of the solid content of the aqueous acrylic dispersion.

[0187] After heat storage in an oven at 50 °C for 2 weeks, the aqueous acrylic dispersion in this comparative example has no obvious precipitation and stratification.

[0188] Example 13

[0189] This example provides an application of an aqueous acrylic dispersion in an aqueous two-component polyurethane coating.

[0190] Specifically, an aqueous two-component polyurethane coating is provided, which includes component A and component B; among them, component A includes 60 wt% of the aqueous acrylic dispersion of any one of Examples 1-12, 30 wt% of white paste (titanium dioxide content is 75 wt%), 0.1 wt% of neutralizer, 6 wt% of cosolvent, 0.2 wt% of wetting agent, 0.5 wt% of wetting and defoaming agent, 4 wt% of thickener, and 2.8 wt% of pure water. Component B includes 70 wt% of polyisocyanate crosslinking agent and 30 wt% of cosolvent. The selection of each component is referred to Table 1. It is obtained by mixing component A and component B according to the molar ratio of the content of NCO groups in the polyisocyanate crosslinking agent to the content of hydroxyl groups in the aqueous acrylic dispersion of NCO / OH = 1.5.

[0191] This example also provides a coating film, which is obtained by applying the aqueous two-component polyurethane coating of this example on the surfaces of wood and metal substrates.

[0192] Performance Test

[0193] The aqueous acrylic dispersions of Examples 1-12, Comparative Examples 1, 3-4 and the commercial aqueous acrylic dispersion PA-4842 are respectively combined with a polyisocyanate crosslinking agent for use in an aqueous two-component polyurethane coating.

[0194] Commercial aqueous acrylic dispersion PA-4842: Guangzhou Guanzhi New Materials, solid hydroxyl value 110 mg KOH / g, solid acid value 24 mg KOH / g, solid content is 43 wt%.

[0195] Polyisocyanate crosslinking agent: Wannate HT-600, Wanhua Chemical, commercial hydrophobic HDI-type polyisocyanate, solid content: 100%, NCO value 23.0%.

[0196] Table 1 Formulation of Aqueous Two-Component Polyurethane Coating

[0197]

[0198] Specifically, the waterborne acrylic dispersions of Examples 1-12, Comparative Examples 1, 3-4 and commercial waterborne acrylic dispersion PA-4842 were formulated into waterborne two-component polyurethane coatings according to the formula in Table 1, and performance tests were performed.

[0199] The curing construction conditions are as follows: spray the water-based two-component polyurethane coating on the surface of the tinplate, place it at room temperature for 20 minutes, then bake it in an 80°C forced air oven for 1 hour, and then place it at room temperature for 3 days before conducting gloss and water resistance tests.

[0200] Gloss (60°) test: Tested in accordance with standard GB / T 9754-2007.

[0201] 35℃ Usable time test: Place the paint at 35℃, measure the coating gloss and paint viscosity every 0.5 hours, and the time without obvious change is the usable time.

[0202] 40℃ water resistance test: Soak the dried coating film in 40℃ water and observe the time it takes for no bubbles or gloss loss.

[0203] The performance test results are shown in Table 2:

[0204] Table 2 Performance test of coatings

[0205]

[0206] According to the above results, we can know that:

[0207] The waterborne two-component polyurethane coating prepared by using the waterborne acrylic dispersion of Examples 1-12 of the present invention in combination with a polyisocyanate crosslinker has excellent gloss, usable time and water resistance. This is because the oleate group in the first monomer contains a double bond that can participate in free radical polymerization, which is introduced into the first copolymer through free radical polymerization. The introduction of the hydrophobic long-chain oleate group greatly improves the water resistance of the first polymer, thereby improving the water resistance of the waterborne acrylic dispersion and the waterborne two-component polyurethane coating. The structure of the first monomer (sorbitan oleate) belongs to an emulsifier, which can improve the compatibility with the polyisocyanate crosslinker, especially has a good emulsifying effect on the hydrophobic polyisocyanate crosslinker, and can obtain a high-gloss coating film; the large sterically hindered oleate group will wrap the first copolymer, making it more difficult for the hydroxyl group in the waterborne acrylic dispersion to contact and react with the polyisocyanate crosslinker in the water phase state, so it has a long usable time.

[0208] The aqueous acrylic dispersion of Comparative Example 1 does not contain the first copolymer within the scope of the present invention, and the aqueous two-component polyurethane coating corresponding to the aqueous acrylic dispersion of Comparative Example 1 exhibits poor gloss, usable time and water resistance.

[0209] The solid content acid value of the aqueous acrylic dispersion of Comparative Example 2 is too low, resulting in poor storage stability of the aqueous acrylic dispersion of Comparative Example 2, and a storage-stable aqueous acrylic dispersion cannot be obtained.

[0210] The solid content acid value of the aqueous acrylic dispersion of Comparative Example 3 is too high. The too high acid value will catalyze the side reaction of the polyisocyanate crosslinking agent and water, making the pot life of the aqueous two-component polyurethane coating corresponding to the aqueous acrylic dispersion of Comparative Example 2 shorter. The too high acid value will also make the first polymer too hydrophilic, resulting in poor water resistance of the aqueous two-component polyurethane coating.

[0211] In the aqueous acrylic dispersion of Comparative Example 4, a non-ionic reactive emulsifier is used to replace the first monomer (i.e., sorbitan oleate). Although the gloss and pot life of the aqueous two-component polyurethane coating corresponding to the aqueous acrylic dispersion of the comparative example are good, due to the introduction of a large number of hydrophilic polyether groups, the water resistance is poor.

[0212] The commercial PA-4842 does not contain the first copolymer within the scope of the present invention, and the corresponding aqueous two-component polyurethane coating exhibits poor gloss, pot life and water resistance.

[0213] The above-described embodiments merely represent several embodiments of the present invention, and their descriptions are relatively specific and detailed, but should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and the present invention also intends to include these modifications and deformations.

Claims

1. An aqueous acrylic dispersion, characterized in that: It includes a first copolymer; the comonomers of the first copolymer include a first monomer, a second monomer, a third monomer, and a fourth monomer, and the first monomer has the structure of formula (1); the first monomer accounts for 5-35 wt% of the total amount of the comonomers of the first copolymer; the first monomer accounts for 1-20 wt% of the solid content of the aqueous acrylic dispersion; the second monomer is at least one of 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, and 4-hydroxybutyl methacrylate; the third monomer is at least one of methacrylic acid, acrylic acid, itaconic acid, and crotonic acid; the fourth monomer is at least one of (meth)acrylate without hydroxyl and carboxyl groups with an alcohol part containing a C1-C18 hydrocarbon group, vinyl aromatic hydrocarbons, and vinyl esters; the acid value of the solid content of the aqueous acrylic dispersion is 15-35 mg KOH / g, and the hydroxyl value of the solid content is 50-165 mgKOH / g; In formula (1), R1, R2, R3, and R4 are independently one of -C(=O)-(CH2)7CH=CH(CH2)7CH3 and H, and at least one of R1, R2, R3, and R4 is a -C(=O)-(CH2)7CH=CH(CH2)7CH3 group, and the statistical average value of a + b + c + d is 0-40.

2. The aqueous acrylic dispersion according to claim 1, wherein: The second monomer accounts for 10-40 wt% of the total amount of the comonomers of the first copolymer; The third monomer accounts for 0-30 wt% of the total amount of the comonomers of the first copolymer; The fourth monomer accounts for 20-65 wt% of the total amount of the comonomers of the first copolymer.

3. The aqueous acrylic dispersion according to claim 2, wherein: It further includes a second copolymer, and the comonomers of the second copolymer include a fifth monomer and / or a sixth monomer and / or a seventh monomer; wherein, the fifth monomer is a hydroxyl-functionalized unsaturated monomer different from the first monomer; the sixth monomer is a carboxyl-functionalized unsaturated monomer; the seventh monomer is other unsaturated monomers different from the first monomer, the fifth monomer, and the sixth monomer.

4. The aqueous acrylic dispersion according to claim 1, wherein: The first monomer is at least one of sorbitan monooleate, sorbitan trioleate, polyoxyethylene sorbitan monooleate, and polyoxyethylene sorbitan trioleate.

5. The aqueous acrylic dispersion according to claim 3, wherein: The fifth monomer is at least one of 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, and 4-hydroxybutyl methacrylate; The sixth monomer is at least one of methacrylic acid, acrylic acid, itaconic acid, and crotonic acid; The seventh monomer is at least one of (meth)acrylate without hydroxyl and carboxyl groups with an alcohol part containing a C1-C18 hydrocarbon group, vinyl aromatic hydrocarbons, and vinyl esters.

6. The aqueous acrylic dispersion according to claim 1, characterized in that: It further includes a neutralizing agent, and the neutralization degree of the aqueous acrylic dispersion is 40-110%.

7. The aqueous acrylic dispersion according to claim 1, characterized in that: It also includes water and an organic solvent, and the solid content of the aqueous acrylic dispersion is 30 - 60 wt%; the content of the organic solvent in the aqueous acrylic dispersion is 2 - 10 wt%.

8. An aqueous coating, characterized in that: It includes the aqueous acrylic dispersion according to any one of claims 1 - 7 and a crosslinking agent.

9. The waterborne coating according to claim 8, wherein: The crosslinking agent is a polyisocyanate crosslinking agent containing free NCO groups.

10. A coating film, characterized in that: It is obtained by applying the aqueous coating according to claim 8 or 9 on a substrate.

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