Water-based acrylic dispersion as well as preparation method and application thereof

Abstract

The invention relates to a water-based acrylic dispersion as well as a preparation method and application thereof, and belongs to the technical field of water-based paint. The water-based acrylic acid dispersion comprises a first copolymer, comonomers of the first copolymer comprise a first monomer, and the first monomer is sorbitan oleic acid; the first monomer accounts for 1-20wt% of the solid content of the water-based acrylic acid dispersion; the solid acid value of the water-based acrylic acid dispersion is 15 to 35 mg KOH / g, and the solid hydroxyl value of the water-based acrylic acid dispersion is 50 to 165 mg KOH / g. The water-based acrylic acid dispersion has excellent storage stability, and the water-based paint using the water-based acrylic acid dispersion as a main film-forming substance has the advantages of high gloss, long service life and good water resistance.

Description

Technical Field

[0001] The invention relates to the technical field of water-based coatings, and in particular to a water-based acrylic acid dispersion and a preparation method and application thereof. Background Art

[0002] As the coatings industry pays more attention to environmental protection, the use of solvent-based coatings faces more and more restrictions. Today, low-VOC (volatile organic compounds) water-based coatings have become an inevitable trend in the development of the coatings industry. Water-based coatings (such as two-component water-based polyurethane coatings) that use water-based acrylic dispersions as the main film-forming substances stand out with their significant advantages. The coatings they form not only have high gloss and fullness, but also have excellent weather resistance and chemical resistance, and their gloss and color retention properties are particularly outstanding; 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 field of coatings for substrates such as wood and metal, and have become an important force in promoting green changes in the industry.

[0003] CN100402615C discloses an aqueous base material dispersion (aqueous acrylic dispersion), which uses alicyclic unsaturated monomers to participate in free radical polymerization, and then uses triethanolamine as a neutralizer to obtain an aqueous acrylic dispersion with high hardness, excellent water resistance and chemical resistance. CN101353470B discloses a secondary polymer aqueous dispersion (aqueous acrylic dispersion), which uses long-chain aliphatic unsaturated monomers to participate in free radical polymerization to obtain an aqueous acrylic dispersion with high bubble-free film thickness. CN114920884A discloses a hydroxylated acrylic dispersion that is universal for both aqueous and oily curing agents, which uses a reactive emulsifier as a comonomer, and the obtained hydroxylated acrylic dispersion has good compatibility with aqueous and oily polyisocyanate curing agents.

[0004] However, all of the above aqueous acrylic dispersions have some defects. The usable time, water resistance and gloss of water-based coatings using the above aqueous acrylic dispersions as the main film-forming material need to be further improved. Summary of the invention

[0005] Based on this, the object of the present invention is to provide an aqueous acrylic dispersion and a preparation method and application thereof, wherein the aqueous acrylic dispersion has excellent storage stability, and a water-based coating using the aqueous acrylic dispersion as a main film-forming substance has the advantages of high gloss, long usable time and good water resistance.

[0006] To achieve the above object, the present invention adopts the following technical solutions: The present invention provides an aqueous acrylic dispersion, comprising a first copolymer; the comonomer of the first copolymer comprises a first monomer, the first monomer having a structure of formula (1) (i.e., the first monomer is sorbitan oleate); the first monomer accounts for 1-20wt% 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;

[0007] 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.

[0008] The present invention surprisingly found through research that the water-based acrylic dispersion contains a first monomer with a specific structure as a copolymer to obtain a first copolymer, which can significantly improve the gloss, usable time and water resistance of water-based coatings using the water-based acrylic dispersion as the main film-forming material.

[0009] In the present invention, the first monomer has a structure of formula (1), which is sorbitan oleate, and the first monomer contains an oleate group (oleate group: -OC(=O)-(CH2)7CH=CH(CH2)7CH3, where the -C(=O)-(CH2)7CH=CH(CH2)7CH3 group and the "O" to which it is connected together constitute an oleate group). The oleate group in the first monomer contains an unsaturated double bond that can participate in free radical polymerization, which is introduced into the first copolymer through free radical polymerization of the unsaturated double bond, 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. The present invention introduces the first monomer into the first copolymer through a clever design, which can improve the compatibility of the first copolymer with the crosslinking agent (such as polyisocyanate crosslinking agent) in the water-based paint, especially with the hydrophobic crosslinking agent (such as hydrophobic polyisocyanate crosslinking agent). It has a good emulsifying effect, so that the water-based paint can obtain a high-gloss coating film. In addition, the oleate group also has a 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 group in the first copolymer to contact and react with the crosslinking agent (such as polyisocyanate crosslinking agent) in the water phase state, thereby making the water-based paint have a long usable time.

[0010] In the aqueous acrylic dispersion of the present invention, the first monomer accounts for 1-20wt% of the solid content of the aqueous acrylic dispersion. If the content of the first monomer is too low, the effect of improving the gloss, usable time and water resistance is not obvious; if the content of the first monomer is too high, since the first monomer contains an oleate group, the structure is soft and the hardness of the coating film will be significantly reduced.

[0011] The solid acid value of the waterborne acrylic dispersion of the present invention is 15-35 mg KOH / g, and the solid hydroxyl value is 50-165 mg KOH / g. Too low an acid value can easily lead to poor storage stability of the waterborne acrylic dispersion; too high an acid value can cause the waterborne acrylic dispersion to be formulated into a waterborne coating by catalyzing the side reaction of the crosslinking agent (such as a polyisocyanate crosslinking agent) with water, thereby shortening the usable time of the waterborne coating, and too high an acid value can also make the first copolymer too hydrophilic, ultimately resulting in poor water resistance of the waterborne coating. Too low a hydroxyl value can make the crosslinking density of the waterborne coating too low, affecting water resistance; too high a hydroxyl value can make the waterborne acrylic dispersion difficult to synthesize, and can easily lead to problems such as high viscosity and poor fineness.

[0012] 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 5-35wt% 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 10-40wt% 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 0-30wt% of the total amount of the comonomers of the first copolymer; the fourth monomer is another unsaturated monomer different from the first monomer, the second monomer, and the third monomer, and the fourth monomer accounts for 20-65wt% of the total amount of the comonomers of the first copolymer. Preferably, the sum of the comonomers of the first copolymer is 100wt%, 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.

[0013] It should be emphasized in the present invention that the first copolymer in the aqueous acrylic dispersion 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; it can also be: a mixture of the above two copolymerization products. Those skilled in the art can select and set it according to actual needs, so that the first monomer accounts for 1-20wt% of the solid content of the aqueous acrylic dispersion; the solid acid value of the aqueous acrylic dispersion is 15-35 mg KOH / g, and the solid hydroxyl value is 50-165 mg KOH / g.

[0014] As a preferred embodiment of the present invention, the aqueous acrylic dispersion may further include a second copolymer; 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 (i.e., the fifth monomer has the same selection range as the second monomer, but is independent of each other); the sixth monomer is a carboxyl-functionalized unsaturated monomer (i.e., the sixth monomer has the same selection range as the third monomer, but is independent of each other); and the seventh monomer is another unsaturated monomer different from the first monomer, the fifth monomer, and the sixth monomer (i.e., the seventh monomer has the same selection range as the fourth monomer, but is independent of each other).

[0015] It is necessary to further explain that the present invention can select the aqueous acrylic dispersion of the present invention to include or exclude the second copolymer according to actual needs, and the aqueous acrylic dispersion of the present invention can meet the conditions that "the first monomer accounts for 1-20wt% of the solid content of the aqueous acrylic dispersion, the solid acid value of the aqueous acrylic dispersion is 15-35 mg KOH / g, and the solid hydroxyl value is 50-165 mg KOH / g". For example, the first copolymer in the aqueous acrylic dispersion of the present invention can provide the conditions that "the first monomer accounts for 1-20wt% of the solid content of the aqueous acrylic dispersion; the solid acid value of the aqueous acrylic dispersion is 15-35 mg KOH / g, and the solid hydroxyl value is 50-165 mg KOH / g", and then the second copolymer can be selected not to include. The first copolymer in the aqueous acrylic dispersion of the present invention cannot satisfy the condition that "the first monomer accounts for 1-20wt% 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 mgKOH / g". If 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, or the hydroxyl value of the solid content is too high or too low, the aqueous acrylic dispersion of the present invention may include the second copolymer, and each monomer (fifth monomer, sixth monomer, seventh monomer) is selected according to the requirements of each condition to copolymerize to obtain the corresponding second copolymer, so that the aqueous acrylic dispersion of the present invention satisfies the condition that "the first monomer accounts for 1-20wt% 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".

[0016] 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.

[0017] 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 so that the aqueous acrylic dispersion of the present invention has a solid content hydroxyl value that meets the requirements.

[0018] 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 a carboxyl group so that the aqueous acrylic dispersion of the present invention has a solid acid value that meets the requirements.

[0019] As a preferred embodiment of the present invention, the fourth monomer and the seventh monomer are (meth)acrylates and / or vinyl aromatics and / or vinyl esters having C1-C18 hydrocarbon groups in the alcohol portion and having no hydroxyl group and carboxyl 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 content acid value, and the solid content hydroxyl value of the aqueous acrylic dispersion.

[0020] Preferably, the fourth monomer and the seventh monomer are independently selected from at least one of C1-C18 alkyl methacrylate, C1-C18 alkyl acrylate, styrene, substituted styrene, vinyl acetate, and versatile vinyl carbonate. For example, the fourth monomer and the seventh monomer are independently selected from 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, versatile vinyl carbonate, and the like.

[0021] As a preferred embodiment of the present invention, the aqueous acrylic dispersion further includes a neutralizer, and the degree of neutralization of the aqueous acrylic dispersion is 40-110%. Too low a neutralization degree will result in poor storage stability of the aqueous acrylic dispersion, and easy stratification and precipitation; too high a neutralization degree will cause the aqueous acrylic dispersion to be formulated into a water-based coating with a crosslinker, and the catalytic crosslinker (such as a polyisocyanate crosslinker) and water will react with the side reaction, resulting in a shortened usable time of the water-based coating. In addition, it should be noted that the neutralizer needs to be added before adding water (dispersion in water). Preferably, the neutralizer is at least one of N,N-dimethylethanolamine, triethanolamine, ammonia water, sodium hydroxide, and potassium hydroxide.

[0022] 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 30-60wt%; the content of the organic solvent in the aqueous acrylic dispersion is 2-10wt%. Too little organic solvent will lead to excessive viscosity during the polymerization reaction and low polymerization conversion rate; too much organic solvent will lead to a high VOC content in the water-based coating, which is disadvantageous from an environmental protection perspective.

[0023] The present invention also provides a use of any of the above-mentioned aqueous acrylic dispersions in aqueous coatings. The aqueous coating using the aqueous acrylic dispersion as the main film-forming substance has the advantages of high gloss, long usable time and good water resistance.

[0024] Specifically, the present invention provides a water-based coating comprising any of the above-mentioned water-based acrylic dispersions and a cross-linking agent.

[0025] 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 the use of any of the above-mentioned aqueous acrylic dispersions in combination with a polyisocyanate crosslinking agent in an aqueous two-component polyurethane coating.

[0026] The present invention also provides a coating film, which is obtained by applying any of the above-mentioned water-based coatings on a substrate.

[0027] Compared with the prior art, the present invention has the following beneficial effects: The water-based acrylic dispersion has excellent storage stability, and the water-based two-component polyurethane coating prepared with a polyisocyanate crosslinking agent has the advantages of high gloss, long usable time and good water resistance. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with examples. These examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples that do not specify specific conditions are usually carried out according to 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 commercial channels such as conventional markets. Any non-substantial changes and substitutions made by those skilled in the art on the basis of the present invention belong to the scope of protection claimed by the present invention.

[0029] Example 1 This embodiment provides an aqueous acrylic dispersion, comprising an organic solvent, a first copolymer, a second copolymer, a neutralizing agent and deionized water. The first copolymer comprises 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. The first monomer is Tween 85, i.e., polyoxyethylene (20) sorbitan trioleate, having a structure of formula (1):

[0030] 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 20.

[0031] The comonomers of the second copolymer include the fifth monomer and the seventh monomer.

[0032] This embodiment also provides a method for preparing an aqueous acrylic acid dispersion, comprising the following steps: The reaction vessel was purged with nitrogen, and an organic solvent (54.0 g of propylene glycol butyl ether) was added into the reaction vessel and heated to 145°C with stirring. 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 uniform speed within 193 min, maintaining the reaction temperature at 145°C. After the addition was completed, the mixture was kept warm for 60 minutes. The first monomer (12.0g Tween 85), the second monomer (17.0g 2-hydroxyethyl methacrylate), the third monomer (9.4g acrylic acid), the fourth monomer (15.0g methyl methacrylate, 5.0g n-butyl acrylate), and the initiator (1.7g di-tert-butyl peroxide) were mixed evenly and uniformly added dropwise to the reaction container within 47 minutes, and the reaction temperature was maintained at 145°C. After the addition was completed, the temperature was kept at this temperature for 180 minutes. The temperature was lowered to about 90°C, 9.3g N,N-dimethylethanolamine was added, and stirred for 15 minutes. 309.0g deionized water was slowly added dropwise under high-speed stirring, and the addition was completed in about 2 hours to obtain a milky white aqueous acrylic dispersion.

[0033] The aqueous acrylic dispersion of this embodiment 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, and 30.0 g of n-butyl acrylate) are copolymerized to form a 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 (9.4 g of acrylic acid) and the fourth monomer (15.0 g of methyl methacrylate and 5.0 g of n-butyl acrylate) are copolymerized to form a first copolymer.

[0034] The solid content of the aqueous acrylic dispersion of this embodiment is 45 wt %, the solid acid value is 24 mg KOH / g, the solid hydroxyl value 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.

[0035] The aqueous acrylic dispersion of this example showed no obvious precipitation and stratification after heat storage in an oven at 50° C. for 2 weeks.

[0036] Example 2 This embodiment provides an aqueous acrylic dispersion, comprising an organic solvent, a first copolymer, a second copolymer, a neutralizing agent and deionized water. The comonomers 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, wherein the first monomer is Tween 85 (the same as in Example 1), i.e., polyoxyethylene (20) sorbitan trioleate.

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

[0038] The preparation method of the aqueous acrylic acid dispersion of the present embodiment comprises the following steps: The reaction vessel was purged with nitrogen, and an organic solvent (54.0 g of propylene glycol butyl ether) was added into the reaction vessel and heated to 145°C with stirring. 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 uniform speed within 193 min, maintaining the reaction temperature at 145°C. After the addition was completed, the mixture was kept warm for 60 minutes. The first monomer (3.5g Tween 85), the second monomer (17.0g 2-hydroxyethyl methacrylate), the third monomer (9.4g acrylic acid), the fourth monomer (15.0g methyl methacrylate, 5.0g n-butyl acrylate), and the initiator (1.7g di-tert-butyl peroxide) were mixed evenly and uniformly added dropwise to the reaction container within 47 minutes, and the reaction temperature was maintained at 145°C. After the addition was completed, the temperature was kept at this temperature for 180 minutes. The temperature was lowered to about 90°C, 9.3g N,N-dimethylethanolamine was added, and stirred for 15 minutes. 298.0g deionized water was slowly added dropwise under high-speed stirring, and the addition was completed in about 2 hours to obtain a milky white aqueous acrylic dispersion.

[0039] The aqueous acrylic dispersion of this embodiment 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, and 30.0 g of n-butyl acrylate) are copolymerized to form a 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 and 5.0 g of n-butyl acrylate) are copolymerized to form a first copolymer.

[0040] The solid content of the aqueous acrylic dispersion of this embodiment 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.

[0041] The aqueous acrylic dispersion of this example showed no obvious precipitation and stratification after heat storage in an oven at 50° C. for 2 weeks.

[0042] Example 3 This embodiment provides an aqueous acrylic dispersion, comprising an organic solvent, a first copolymer P1, a second copolymer P2, a neutralizing agent and deionized water. The first copolymer P1 has comonomers including 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 no third monomer. The first monomer M1a is Tween 85 (the same as in Example 1), i.e., polyoxyethylene (20) sorbitan trioleate.

[0043] 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, wherein the first monomer M1b is Tween 85 (the same as in Example 1), i.e., polyoxyethylene (20) sorbitan trioleate.

[0044] The preparation method of the aqueous acrylic acid dispersion of the present embodiment comprises the following steps: Nitrogen was passed through the reaction container, an organic solvent (54.0 g of propylene glycol butyl ether) was added into the reaction container and the temperature was raised to 145°C with stirring, 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 an initiator (7.0 g of di-tert-butyl peroxide) were mixed evenly, and added dropwise into the reaction container at a uniform speed within 193 min, the reaction temperature was maintained at 145°C, and after the addition was completed, the mixture was kept warm for 60 minutes. The first monomer M1b (20.0g Tween 85), the second monomer M2b (17.0g 2-hydroxyethyl methacrylate), the third monomer M3b (9.4g acrylic acid), the fourth monomer M4b (12.0g methyl methacrylate), and the initiator (1.7g di-tert-butyl peroxide) were mixed evenly and uniformly added dropwise to the reaction container within 47 minutes, and the reaction temperature was maintained at 145°C. After the addition was completed, the temperature was kept at this temperature for 180 minutes. The temperature was lowered to about 90°C, 9.3g N,N-dimethylethanolamine was added, and stirred for 15 minutes. 309.0g deionized water was slowly added dropwise under high-speed stirring, and the addition was completed in about 2 hours to obtain a milky white aqueous acrylic dispersion.

[0045] The aqueous acrylic dispersion of this embodiment is mainly synthesized by a two-stage method. During the first stage of the heat preservation reaction process, the first monomer M1a (40.0 g Tween 85), the second monomer M2a (72.0 g 2-hydroxyethyl methacrylate) and the fourth monomer M4a (58.0 g methyl methacrylate, 35.0 g styrene, 22.0 g isobutyl methacrylate, 10.0 g n-butyl acrylate) are copolymerized to form the first copolymer P1; during the second stage of the heat preservation reaction process, the first monomer M1b (20.0 g Tween 85), the second monomer M2b (17.0 g 2-hydroxyethyl methacrylate), the third monomer M3b (9.4 g acrylic acid) and the fourth monomer M4b (12.0 g methyl methacrylate) are copolymerized to form the first copolymer P2.

[0046] The aqueous acrylic dispersion of this embodiment has a solid content of 45 wt %, a solid acid value of 24 mg KOH / g, a solid hydroxyl value of 132 mg KOH / g, a neutralization degree of 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.

[0047] The aqueous acrylic dispersion of this example showed no obvious precipitation and stratification after heat storage in an oven at 50° C. for 2 weeks.

[0048] Example 4 This embodiment provides an aqueous acrylic dispersion, comprising an organic solvent, a first copolymer, a second copolymer, a neutralizing agent and deionized water. The comonomers 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 no third monomer. The first monomer is Tween 85 (the same as in Example 1), i.e., polyoxyethylene (20) sorbitan trioleate.

[0049] The comonomers of the second copolymer include a fifth monomer, a sixth monomer, and a seventh monomer.

[0050] The preparation method of the aqueous acrylic acid dispersion of the present embodiment comprises the following steps: The reaction vessel was purged with nitrogen, and an organic solvent (54.0 g of propylene glycol butyl ether) was added into the reaction vessel and heated to 145°C with stirring. 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 an initiator (7.0 g of di-tert-butyl peroxide) were 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 addition was completed, the mixture was kept warm for 60 minutes. The fifth monomer (17.0g 2-hydroxyethyl methacrylate), the sixth monomer (9.4g acrylic acid), the seventh monomer (20.0g methyl methacrylate, 12.0g n-butyl acrylate), and the initiator (1.7g di-tert-butyl peroxide) were mixed evenly and uniformly added dropwise to the reaction vessel within 47 minutes, and the reaction temperature was maintained at 145°C. After the addition was completed, the temperature was kept at this temperature for 180 minutes. The temperature was lowered to about 90°C, 9.3g N,N-dimethylethanolamine was added, and stirred for 15 minutes. 309.0g deionized water was slowly added dropwise under high-speed stirring, and the addition was completed in about 2 hours to obtain a milky white aqueous acrylic dispersion.

[0051] The aqueous acrylic dispersion of this embodiment is mainly synthesized by a two-stage method. During the heat preservation reaction process of the first stage, the first monomer (12.0 g Tween 85), the second monomer (72.0 g 2-hydroxyethyl methacrylate) and the fourth monomer (58.0 g methyl methacrylate, 35.0 g styrene, 42.0 g isobutyl methacrylate, 18.0 g n-butyl acrylate) are copolymerized to form a first copolymer; during the heat preservation reaction process of the second stage, the fifth monomer (17.0 g 2-hydroxyethyl methacrylate), the sixth monomer (9.4 g acrylic acid) and the seventh monomer (20.0 g methyl methacrylate, 12.0 g n-butyl acrylate) are copolymerized to form a second copolymer.

[0052] The solid content of the aqueous acrylic dispersion of this embodiment is 45 wt %, the solid acid value is 24 mg KOH / g, the solid hydroxyl value 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.

[0053] The aqueous acrylic dispersion of this example showed no obvious precipitation and stratification after heat storage in an oven at 50° C. for 2 weeks.

[0054] Example 5 This embodiment provides an aqueous acrylic dispersion, comprising an organic solvent, a first copolymer, a second copolymer, a neutralizing agent and deionized water. The first copolymer comprises 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. The first monomer is Tween 80, i.e., polyoxyethylene (20) sorbitan monooleate, having a structure of formula (1):

[0055] Among them: R4 is -C(=O)-(CH2)7CH=CH(CH2)7CH3, R1, R2 and R3 are H; the statistical average value of a+b+c+d is about 20.

[0056] The comonomers of the second copolymer include the fifth monomer and the seventh monomer.

[0057] The preparation method of the aqueous acrylic acid dispersion of the present embodiment comprises the following steps: The reaction vessel was purged with nitrogen, and an organic solvent (54.0 g of propylene glycol butyl ether) was added into the reaction vessel and heated to 145°C with stirring. 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 uniform speed within 193 min, maintaining the reaction temperature at 145°C. After the addition was completed, the mixture was kept warm for 60 minutes. The first monomer (12.0g Tween 80), the second monomer (17.0g 2-hydroxyethyl methacrylate), the third monomer (9.4g acrylic acid), the fourth monomer (15.0g methyl methacrylate, 5.0g n-butyl acrylate), and the initiator (1.7g di-tert-butyl peroxide) were mixed evenly and added dropwise to the reaction container at a uniform speed within 47 minutes, and the reaction temperature was maintained at 145°C. After the addition was completed, the temperature was kept at this temperature for 180 minutes. The temperature was lowered to about 90°C, 9.3g N,N-dimethylethanolamine was added, and stirred for 15 minutes. 309.0g deionized water was slowly added dropwise under high-speed stirring, and the addition was completed in about 2 hours to obtain a milky white aqueous acrylic dispersion.

[0058] The aqueous acrylic dispersion of this embodiment 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, and 30.0 g of n-butyl acrylate) are copolymerized to form a second copolymer; during the heat preservation reaction process of 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 and 5.0 g of n-butyl acrylate) are copolymerized to form a first copolymer.

[0059] The aqueous acrylic dispersion of this embodiment has a solid content of 45 wt %, a solid acid value of 24 mg KOH / g, a solid hydroxyl value of 131 mg KOH / g, a neutralization degree of 80%, and the first monomer accounts for 4.0 wt % of the solid content of the aqueous acrylic dispersion.

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

[0061] Example 6 This embodiment provides an aqueous acrylic dispersion, comprising an organic solvent, a first copolymer, a second copolymer, a neutralizing agent and deionized water. The first copolymer comprises 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. The first monomer is Span 85, i.e., sorbitan trioleate, having a structure of formula (1):

[0062] 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 0.

[0063] The comonomers of the second copolymer include the fifth monomer and the seventh monomer.

[0064] The preparation method of the aqueous acrylic acid dispersion of the present embodiment comprises the following steps: The reaction vessel was purged with nitrogen, and an organic solvent (54.0 g of propylene glycol butyl ether) was added into the reaction vessel and heated to 145°C with stirring. 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 uniform speed within 193 min, maintaining the reaction temperature at 145°C. After the addition was completed, the mixture was kept warm for 60 minutes. The first monomer (12.0g Span 85), the second monomer (17.0g 2-hydroxyethyl methacrylate), the third monomer (9.4g acrylic acid), the fourth monomer (15.0g methyl methacrylate, 5.0g n-butyl acrylate), and the initiator (1.7g di-tert-butyl peroxide) were mixed evenly and added dropwise to the reaction container at a uniform speed within 47 minutes, and the reaction temperature was maintained at 145°C. After the addition was completed, the temperature was kept at this temperature for 180 minutes. The temperature was lowered to about 90°C, 9.3g N,N-dimethylethanolamine was added, and stirred for 15 minutes. 309.0g deionized water was slowly added dropwise under high-speed stirring, and the addition was completed in about 2 hours to obtain a milky white aqueous acrylic dispersion.

[0065] The aqueous acrylic dispersion of this embodiment 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, and 30.0 g of n-butyl acrylate) are copolymerized to form a second copolymer; during the heat preservation reaction process of 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 and 5.0 g of n-butyl acrylate) are copolymerized to form a first copolymer.

[0066] The aqueous acrylic dispersion of this embodiment has a solid content of 45 wt %, a solid acid value of 24 mg KOH / g, a solid hydroxyl value of 128 mg KOH / g, a neutralization degree of 80%, and the first monomer accounts for 4.0 wt % of the solid content of the aqueous acrylic dispersion.

[0067] The aqueous acrylic dispersion of this example showed no obvious precipitation and stratification after heat storage in an oven at 50° C. for 2 weeks.

[0068] Example 7 This embodiment provides an aqueous acrylic dispersion, comprising an organic solvent, a first copolymer, a second copolymer, a neutralizing agent and deionized water. The first copolymer comprises 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. The first monomer is Span 80, i.e., sorbitan monooleate, having a structure of formula (1):

[0069] Wherein: R4 is -C(=O)-(CH2)7CH=CH(CH2)7CH3, R1, R2 and R3 are H; the statistical average value of a+b+c+d is 0.

[0070] The comonomers of the second copolymer include the fifth monomer and the seventh monomer.

[0071] The preparation method of the aqueous acrylic acid dispersion of the present embodiment comprises the following steps: The reaction vessel was purged with nitrogen, and an organic solvent (54.0 g of propylene glycol butyl ether) was added into the reaction vessel and heated to 145°C with stirring. 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 uniform speed within 193 min, maintaining the reaction temperature at 145°C. After the addition was completed, the mixture was kept warm for 60 minutes. The first monomer (12.0g Span 80), the second monomer (17.0g 2-hydroxyethyl methacrylate), the third monomer (9.4g acrylic acid), the fourth monomer (15.0g methyl methacrylate, 5.0g n-butyl acrylate), and the initiator (1.7g di-tert-butyl peroxide) were mixed evenly and uniformly added dropwise to the reaction container within 47 minutes, and the reaction temperature was maintained at 145°C. After the addition was completed, the temperature was kept at this temperature for 180 minutes. The temperature was lowered to about 90°C, 9.3g N,N-dimethylethanolamine was added, and stirred for 15 minutes. 309.0g deionized water was slowly added dropwise under high-speed stirring, and the addition was completed in about 2 hours to obtain a milky white aqueous acrylic dispersion.

[0072] The aqueous acrylic dispersion of this embodiment 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, and 30.0 g of n-butyl acrylate) are copolymerized to form a second copolymer; during the heat preservation reaction process of 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 and 5.0 g of n-butyl acrylate) are copolymerized to form a first copolymer.

[0073] The aqueous acrylic dispersion of this embodiment has a solid content of 45 wt %, a solid acid value of 24 mg KOH / g, a solid hydroxyl value of 131 mg KOH / g, a neutralization degree of 80%, and the first monomer accounts for 4.0 wt % of the solid content of the aqueous acrylic dispersion.

[0074] The aqueous acrylic dispersion of this example showed no obvious precipitation and stratification after heat storage in an oven at 50° C. for 2 weeks.

[0075] Example 8 This embodiment provides an aqueous acrylic dispersion, comprising an organic solvent, a first copolymer, a second copolymer, a neutralizing agent and deionized water. The first copolymer comprises 20.6 wt% of a first monomer, 29.1 wt% of a second monomer, 16.1 wt% of a third monomer, and 34.2 wt% of a fourth monomer. The first monomer is polyoxyethylene (38) sorbitan trioleate, having a structure of formula (1):

[0076] 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.

[0077] The synthesis method of polyoxyethylene (38) sorbitan trioleate is specifically as follows: Preheat 957.7g of Span 85 (sorbitan trioleate) and put it into a reactor. Add 2.0g of sodium hydroxide under stirring and vacuum dehydrate. After dehydration, replace the air in the reactor with nitrogen, heat to 140°C and start to introduce 1672g of ethylene oxide, control the reaction pressure to 2-3 atmospheres, and react for 6-10h. Add an appropriate amount of glacial acetic acid to neutralize the 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 2420g of light yellow to amber viscous liquid, which is polyoxyethylene (38) sorbitan trioleate.

[0078] The comonomers of the second copolymer include the fifth monomer and the seventh monomer.

[0079] The preparation method of the aqueous acrylic acid dispersion of the present embodiment comprises the following steps: The reaction vessel was purged with nitrogen, and an organic solvent (54.0 g of propylene glycol butyl ether) was added into the reaction vessel and heated to 145°C with stirring. 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 uniform speed within 193 min, maintaining the reaction temperature at 145°C. After the addition was completed, the mixture was kept warm for 60 minutes. The first monomer (12.0g polyoxyethylene (38) sorbitan trioleate), the second monomer (17.0g 2-hydroxyethyl methacrylate), the third monomer (9.4g acrylic acid), the fourth monomer (15.0g methyl methacrylate, 5.0g n-butyl acrylate), and the initiator (1.7g di-tert-butyl peroxide) were mixed evenly and added dropwise to the reaction container at a uniform speed within 47 minutes, and the reaction temperature was maintained at 145°C. After the addition was completed, the temperature was kept at this temperature for 180 minutes. The temperature was lowered to about 90°C, 9.3g N,N-dimethylethanolamine was added, and stirred for 15 minutes. 309.0g deionized water was slowly added dropwise under high-speed stirring, and the addition was completed in about 2 hours to obtain a milky white aqueous acrylic dispersion.

[0080] The aqueous acrylic dispersion of this embodiment 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, and 30.0 g of n-butyl acrylate) are copolymerized to form a second copolymer; during the heat preservation reaction process of 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 and 5.0 g of n-butyl acrylate) are copolymerized to form a first copolymer.

[0081] The solid content of the aqueous acrylic dispersion of this embodiment is 45 wt %, the solid acid value is 24 mg KOH / g, the solid hydroxyl value 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.

[0082] The aqueous acrylic dispersion of this example showed no obvious precipitation and stratification after heat storage in an oven at 50° C. for 2 weeks.

[0083] Example 9 This embodiment provides an aqueous acrylic dispersion, comprising an organic solvent, a first copolymer, a second copolymer, a neutralizing agent and deionized water. The comonomers 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. The first monomer is Tween 85 (the same as in Example 1), i.e., polyoxyethylene (20) sorbitan trioleate.

[0084] The comonomers of the second copolymer include the fifth monomer and the seventh monomer.

[0085] This embodiment also provides a method for preparing an aqueous acrylic acid dispersion, comprising the following steps: The reaction vessel was purged with nitrogen, and an organic solvent (54.0 g of propylene glycol butyl ether) was added into the reaction vessel and heated to 145°C with stirring. 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 uniform speed within 193 min, maintaining the reaction temperature at 145°C. After the addition was completed, the mixture was kept warm for 60 minutes. The first monomer (12.0g Tween 85), the second monomer (17.0g 2-hydroxyethyl methacrylate), the third monomer (6.0g acrylic acid), the fourth monomer (15.0g methyl methacrylate, 5.0g n-butyl acrylate), and the initiator (1.7g di-tert-butyl peroxide) were mixed evenly and uniformly added dropwise to the reaction container within 47 minutes, and the reaction temperature was maintained at 145°C. After the addition was completed, the temperature was kept at this temperature for 180 minutes. The temperature was lowered to about 90°C, 7.5g N,N-dimethylethanolamine was added, and stirred for 15 minutes. 306.0g deionized water was slowly added dropwise under high-speed stirring, and the addition was completed in about 2 hours to obtain a milky white aqueous acrylic dispersion.

[0086] The aqueous acrylic dispersion of this embodiment 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, and 30.0 g of n-butyl acrylate) are copolymerized to form a 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 and 5.0 g of n-butyl acrylate) are copolymerized to form a first copolymer.

[0087] The aqueous acrylic dispersion of this embodiment has a solid content of 45 wt %, a solid acid value of 15 mg KOH / g, a solid hydroxyl value of 129 mg KOH / g, a neutralization degree of 100%, and the first monomer accounts for 4.0 wt % of the solid content of the aqueous acrylic dispersion.

[0088] The aqueous acrylic dispersion of this example showed no obvious precipitation and stratification after heat storage in an oven at 50° C. for 2 weeks.

[0089] Example 10 This embodiment provides an aqueous acrylic dispersion, comprising an organic solvent, a first copolymer, a second copolymer, a neutralizing agent and deionized water. 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. The first monomer is Tween 85 (the same as in Example 1), i.e., polyoxyethylene (20) sorbitan trioleate.

[0090] The comonomers of the second copolymer include the fifth monomer and the seventh monomer.

[0091] This embodiment also provides a method for preparing an aqueous acrylic acid dispersion, comprising the following steps: The reaction vessel was purged with nitrogen, and an organic solvent (54.0 g of propylene glycol butyl ether) was added into the reaction vessel and heated to 145°C with stirring. 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 uniform speed within 193 min, maintaining the reaction temperature at 145°C. After the addition was completed, the mixture was kept warm for 60 minutes. The first monomer (12.0g Tween 85), the second monomer (17.0g 2-hydroxyethyl methacrylate), the third monomer (13.5g acrylic acid), the fourth monomer (15.0g methyl methacrylate, 5.0g n-butyl acrylate), and the initiator (1.7g di-tert-butyl peroxide) were mixed evenly and uniformly added dropwise to the reaction container within 47 minutes, and the reaction temperature was maintained at 145°C. After the addition was completed, the temperature was kept at this temperature for 180 minutes. The temperature was lowered to about 90°C, 7.5g N,N-dimethylethanolamine was added, and stirred for 15 minutes. 365.0g deionized water was slowly added dropwise under high-speed stirring, and the addition was completed in about 2 hours to obtain a milky white aqueous acrylic dispersion.

[0092] The aqueous acrylic dispersion of this embodiment 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, and 30.0 g of n-butyl acrylate) are copolymerized to form a 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 (13.5 g of acrylic acid) and the fourth monomer (15.0 g of methyl methacrylate and 5.0 g of n-butyl acrylate) are copolymerized to form a first copolymer.

[0093] The solid content of the aqueous acrylic dispersion of this embodiment 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.

[0094] The aqueous acrylic dispersion of this example showed no obvious precipitation and stratification after heat storage in an oven at 50° C. for 2 weeks.

[0095] Embodiment 11 This embodiment provides an aqueous acrylic dispersion, comprising an organic solvent, a first copolymer, a second copolymer, a neutralizing agent and deionized water. The comonomers 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. The first monomer is Tween 85 (the same as in Example 1), i.e., polyoxyethylene (20) sorbitan trioleate.

[0096] The comonomers of the second copolymer include the fifth monomer and the seventh monomer.

[0097] This embodiment also provides a method for preparing an aqueous acrylic acid dispersion, comprising the following steps: The reaction vessel was purged with nitrogen, and an organic solvent (54.0 g of propylene glycol butyl ether) was added into the reaction vessel and heated to 145°C with stirring. 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 an initiator (7.0 g of di-tert-butyl peroxide) were 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 addition was completed, the mixture was kept warm for 60 minutes. The first monomer (12.0g Tween 85), the second monomer (7.0g 2-hydroxyethyl methacrylate), the third monomer (9.4g acrylic acid), the fourth monomer (20.0g methyl methacrylate, 10.0g n-butyl acrylate), and the initiator (1.7g di-tert-butyl peroxide) were mixed evenly and uniformly added dropwise to the reaction container within 47 minutes, and the reaction temperature was maintained at 145°C. After the addition was completed, the temperature was kept at this temperature for 180 minutes. The temperature was lowered to about 90°C, 9.3g N,N-dimethylethanolamine was added, and stirred for 15 minutes. 309.0g deionized water was slowly added dropwise under high-speed stirring, and the addition was completed in about 2 hours to obtain a milky white aqueous acrylic dispersion.

[0098] The aqueous acrylic dispersion of this embodiment is mainly synthesized by a two-stage method. During the heat preservation reaction process of 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, and 30.0 g of n-butyl acrylate) are copolymerized to form a second copolymer; during the heat preservation reaction process of 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 and 10.0 g of n-butyl acrylate) are copolymerized to form a first copolymer.

[0099] The aqueous acrylic dispersion of this embodiment has a solid content of 45 wt %, a solid acid value of 24 mg KOH / g, a solid hydroxyl value of 51 mg KOH / g, a neutralization degree of 80%, and the first monomer accounts for 4.0 wt % of the solid content of the aqueous acrylic dispersion.

[0100] The aqueous acrylic dispersion of this example showed no obvious precipitation and stratification after heat storage in an oven at 50° C. for 2 weeks.

[0101] Example 12 This embodiment provides an aqueous acrylic dispersion, comprising an organic solvent, a first copolymer, a second copolymer, a neutralizing agent and deionized water. The comonomers 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. The first monomer is Tween 85 (the same as in Example 1), i.e., polyoxyethylene (20) sorbitan trioleate.

[0102] The comonomers of the second copolymer include the fifth monomer and the seventh monomer.

[0103] This embodiment also provides a method for preparing an aqueous acrylic acid dispersion, comprising the following steps: The reaction vessel was purged with nitrogen, and an organic solvent (54.0 g of propylene glycol butyl ether) was added into the reaction vessel and heated to 145°C with stirring. 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) were 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 addition was completed, the mixture was kept warm for 60 minutes. The first monomer (12.0g Tween 85), the second monomer (5.0g 4-hydroxybutyl acrylate, 14.0g 2-hydroxyethyl methacrylate), the third monomer (9.4g acrylic acid), the fourth monomer (13.0g methyl methacrylate, 5.0g n-butyl acrylate), and the initiator (1.7g di-tert-butyl peroxide) were mixed evenly and uniformly added dropwise to the reaction container within 47 minutes, and the reaction temperature was maintained at 145°C. After the addition was completed, the temperature was kept at this temperature for 180 minutes. The temperature was lowered to about 90°C, 9.3g N,N-dimethylethanolamine was added, and stirred for 15 minutes. 309.0g deionized water was slowly added dropwise under high-speed stirring, and the addition was completed in about 2 hours to obtain a milky white aqueous acrylic dispersion.

[0104] The aqueous acrylic dispersion of this embodiment is mainly synthesized by a two-stage method. During the heat preservation reaction process of the first stage, the fifth monomer (30.0 g 4-hydroxybutyl acrylate, 69.0 g 2-hydroxyethyl methacrylate) and the seventh monomer (58.0 g methyl methacrylate, 35.0 g styrene, 33.0 g isobutyl methacrylate, 12.0 g n-butyl acrylate) are copolymerized to form a second copolymer; during the heat preservation reaction process of the second stage, the first monomer (12.0 g Tween 85), the second monomer (5.0 g 4-hydroxybutyl acrylate, 14.0 g 2-hydroxyethyl methacrylate), the third monomer (9.4 g acrylic acid) and the fourth monomer (13.0 g methyl methacrylate, 5.0 g n-butyl acrylate) are copolymerized to form a first copolymer.

[0105] The aqueous acrylic dispersion of this embodiment has a solid content of 45 wt %, a solid acid value of 24 mg KOH / g, a solid hydroxyl value of 164 mg KOH / g, a neutralization degree of 80%, and the first monomer accounts for 4.0 wt % of the solid content of the aqueous acrylic dispersion.

[0106] The aqueous acrylic dispersion of this example showed no obvious precipitation and stratification after heat storage in an oven at 50° C. for 2 weeks.

[0107] Comparative Example 1 This comparative example provides an aqueous acrylic dispersion, comprising an organic solvent, a second copolymer Q1, a second copolymer Q2, a neutralizing agent and deionized water, but excluding the first copolymer. The comonomers of the second copolymer Q1 include a fifth monomer M5a and a seventh monomer M7a.

[0108] The comonomers of the second copolymer Q2 include a fifth monomer M5b, a sixth monomer M6b, and a seventh monomer M7b.

[0109] This comparative example also provides a method for preparing an aqueous acrylic acid dispersion, comprising the following steps: Nitrogen was passed through the reaction container, an organic solvent (54.0 g of propylene glycol butyl ether) was added into the reaction container and the temperature was raised to 145°C with stirring, 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 an initiator (7.0 g of di-tert-butyl peroxide) were mixed evenly, and added dropwise into the reaction container at a uniform speed within 193 min, the reaction temperature was maintained at 145°C, and after the addition was completed, the mixture was kept warm for 60 minutes. The fifth monomer M5b (17.0g 2-hydroxyethyl methacrylate), the sixth monomer M6b (9.4g acrylic acid), the seventh monomer M7b (15.0g methyl methacrylate, 5.0g n-butyl acrylate), and the initiator (1.7g di-tert-butyl peroxide) were mixed evenly and uniformly added dropwise to the reaction container within 47 minutes, and the reaction temperature was maintained at 145°C. After the addition was completed, the temperature was kept at this temperature for 180 minutes. The temperature was lowered to about 90°C, 9.3g N,N-dimethylethanolamine was added, and stirred for 15 minutes. 294.0g deionized water was slowly added dropwise under high-speed stirring, and the addition was completed in about 2 hours to obtain a milky white aqueous acrylic dispersion.

[0110] The aqueous acrylic dispersion of this comparative example is mainly synthesized by a two-stage method. During the first stage of the heat preservation reaction, 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, and 30.0 g of n-butyl acrylate) are copolymerized to form the second copolymer Q1; during the second stage of the heat preservation reaction, 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 and 5.0 g of n-butyl acrylate) are copolymerized to form the second copolymer Q2.

[0111] The aqueous acrylic dispersion of this comparative example has a solid content of 45 wt %, a solid acid value of 25 mg KOH / g, a solid hydroxyl value of 131 mg KOH / g, and a degree of neutralization of 80%.

[0112] The aqueous acrylic dispersion of this comparative example had no obvious precipitation and stratification after heat storage in an oven at 50° C. for 2 weeks.

[0113] Comparative Example 2 This comparative example provides an aqueous acrylic dispersion, comprising an organic solvent, a first copolymer, a second copolymer, a neutralizing agent and deionized water. The comonomers of the first copolymer include 22.2 wt% of the first monomer, 31.5 wt% of the second monomer, 9.3 wt% of the third monomer, and 37.0 wt% of the fourth monomer, wherein the first monomer is Tween 85 (the same as in Example 1), i.e., polyoxyethylene (20) sorbitan trioleate.

[0114] The comonomers of the second copolymer include the fifth monomer and the seventh monomer.

[0115] The preparation method of the aqueous acrylic acid dispersion of this comparative example comprises the following steps: The reaction vessel was purged with nitrogen, and an organic solvent (54.0 g of propylene glycol butyl ether) was added into the reaction vessel and heated to 145°C with stirring. 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 uniform speed within 193 min, maintaining the reaction temperature at 145°C. After the addition was completed, the mixture was kept warm for 60 minutes. The first monomer (12.0g Tween 85), the second monomer (17.0g 2-hydroxyethyl methacrylate), the third monomer (5.0g acrylic acid), the fourth monomer (15.0g methyl methacrylate, 5.0g n-butyl acrylate), and the initiator (1.7g di-tert-butyl peroxide) were mixed evenly and uniformly added dropwise to the reaction container within 47 minutes, and the reaction temperature was maintained at 145°C. After the addition was completed, the temperature was kept at this temperature for 180 minutes. The temperature was lowered to about 90°C, 6.0g N,N-dimethylethanolamine was added, and stirred for 15 minutes. 307.0g deionized water was slowly added dropwise under high-speed stirring, and the addition was completed in about 2 hours to obtain a milky white aqueous acrylic dispersion.

[0116] 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, and 30.0 g of n-butyl acrylate) are copolymerized to form a 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 and 5.0 g of n-butyl acrylate) are copolymerized to form a first copolymer.

[0117] The aqueous acrylic dispersion of this comparative example has a solid content of 45 wt %, a solid acid value of 13 mg KOH / g, a solid hydroxyl value of 129 mg KOH / g, a neutralization degree of 97%, and the first monomer accounts for 4.0 wt % of the solid content of the aqueous acrylic dispersion.

[0118] The aqueous acrylic acid dispersion of this comparative example showed a large amount of precipitation after heat storage in an oven at 50° C. for 1 day, and a stable aqueous dispersion could not be obtained.

[0119] Comparative Example 3 This comparative example provides an aqueous acrylic dispersion, comprising an organic solvent, a first copolymer, a second copolymer, a neutralizing agent and deionized water. The comonomers 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, wherein the first monomer is Tween 85 (the same as in Example 1), i.e., polyoxyethylene (20) sorbitan trioleate.

[0120] The comonomers of the second copolymer include the fifth monomer and the seventh monomer.

[0121] The preparation method of the aqueous acrylic acid dispersion of this comparative example comprises the following steps: The reaction vessel was purged with nitrogen, and an organic solvent (54.0 g of propylene glycol butyl ether) was added into the reaction vessel and heated to 145°C with stirring. 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 uniform speed within 193 min, maintaining the reaction temperature at 145°C. After the addition was completed, the mixture was kept warm for 60 minutes. The first monomer (12.0g Tween 85), the second monomer (17.0g 2-hydroxyethyl methacrylate), the third monomer (16.0g acrylic acid), the fourth monomer (15.0g methyl methacrylate, 5.0g n-butyl acrylate), and the initiator (1.7g di-tert-butyl peroxide) were mixed evenly and uniformly added dropwise to the reaction container within 47 minutes, and the reaction temperature was maintained at 145°C. After the addition was completed, the temperature was kept at this temperature for 180 minutes. The temperature was lowered to about 90°C, 8.0g N,N-dimethylethanolamine was added, and stirred for 15 minutes. 404.0g deionized water was slowly added dropwise under high-speed stirring, and the addition was completed in about 2 hours to obtain a milky white aqueous acrylic dispersion.

[0122] 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, and 30.0 g of n-butyl acrylate) are copolymerized to form a 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 and 5.0 g of n-butyl acrylate) are copolymerized to form a first copolymer.

[0123] The aqueous acrylic dispersion of this comparative example has a solid content of 40 wt %, a solid acid value of 40 mg KOH / g, a solid hydroxyl value of 125 mg KOH / g, a neutralization degree of 40%, and the first monomer accounts for 3.9 wt % of the solid content of the aqueous acrylic dispersion.

[0124] The aqueous acrylic dispersion of this comparative example had no obvious precipitation and stratification after heat storage in an oven at 50° C. for 2 weeks.

[0125] Comparative Example 4 This comparative example provides an aqueous acrylic dispersion, comprising an organic solvent, a second copolymer, a third copolymer, a neutralizing agent and deionized water. The comonomers of the second copolymer include the fifth monomer and the seventh monomer.

[0126] The comonomers of the third copolymer include nonionic reactive emulsifier ER-10, the second monomer, the third monomer, and the fourth monomer.

[0127] The preparation method of the aqueous acrylic acid dispersion of this comparative example comprises the following steps: The reaction vessel was purged with nitrogen, and an organic solvent (54.0 g of propylene glycol butyl ether) was added into the reaction vessel and heated to 145°C with stirring. 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 uniform speed within 193 min, maintaining the reaction temperature at 145°C. After the addition was completed, the mixture was kept warm for 60 minutes. 12.0g ER-10 (Japan Aidico, non-ionic reactive emulsifier), the second monomer (17.0g 2-hydroxyethyl methacrylate), the third monomer (16.0g acrylic acid), the fourth monomer (15.0g methyl methacrylate, 5.0g n-butyl acrylate), and the initiator (1.7g di-tert-butyl peroxide) were mixed evenly and uniformly added dropwise to the reaction container within 47 minutes, and the reaction temperature was maintained at 145°C. After the addition was completed, the temperature was kept at this temperature for 180 minutes. The temperature was lowered to about 90°C, 8.0g N,N-dimethylethanolamine was added, and stirred for 15 minutes. 404.0g deionized water was slowly added dropwise under high-speed stirring, and the addition was completed in about 2 hours to obtain a water-based acrylic dispersion with a milky white appearance.

[0128] 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, and 30.0 g of n-butyl acrylate) are copolymerized to form a second copolymer; during the heat preservation reaction process of the second stage, 12.0 g of ER-10 (Japan Aidico, a 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 the initiator (1.7 g of di-tert-butyl peroxide) are copolymerized to form a third copolymer.

[0129] The aqueous acrylic dispersion of this comparative example has a solid content of 40 wt %, a solid acid value of 40 mg KOH / g, a solid hydroxyl value of 125 mg KOH / g, a neutralization degree of 80%, and the first monomer accounts for 3.9 wt % of the solid content of the aqueous acrylic dispersion.

[0130] The aqueous acrylic dispersion of this comparative example had no obvious precipitation and stratification after heat storage in an oven at 50° C. for 2 weeks.

[0131] Embodiment 13 This embodiment provides an application of a water-based acrylic dispersion in a water-based two-component polyurethane coating.

[0132] Specifically provided is a water-based two-component polyurethane coating, comprising component A and component B; wherein component A comprises 60wt% of any water-based acrylic dispersion of Examples 1-12, 30wt% of white pulp (titanium dioxide content is 75wt%), 0.1wt% of neutralizer, 6wt% of cosolvent, 0.2wt% of wetting agent, 0.5wt% of wetting defoamer, 4wt% of thickener, and 2.8wt% of pure water. Component B comprises 70wt% of polyisocyanate crosslinking agent and 30wt% of cosolvent, and the selection of each component is shown in Table 1. Component A and component B are mixed according to the molar ratio of the content of NCO groups in the polyisocyanate crosslinking agent to the content of hydroxyl groups in the water-based acrylic dispersion being NCO / OH=1.5 to obtain.

[0133] This embodiment also provides a coating film, which is obtained by applying the water-based two-component polyurethane coating of this embodiment to the surface of a wood or metal substrate.

[0134] Performance Testing The aqueous acrylic dispersions of Examples 1-12, Comparative Examples 1, 3-4 and commercial aqueous acrylic dispersion PA-4842 were respectively used in aqueous two-component polyurethane coatings in combination with polyisocyanate crosslinking agents.

[0135] Commercialized waterborne acrylic dispersion PA-4842: Guangzhou Guanzhi New Materials, solid hydroxyl value 110 mg KOH / g, solid acid value 24 mg KOH / g, solid content 43wt%.

[0136] Polyisocyanate crosslinker: Wannate HT-600, Wanhua Chemical, commercial hydrophobic HDI type polyisocyanate, solid content: 100%, NCO value 23.0%.

[0137] Table 1 Waterborne two-component polyurethane coating formula

[0138] 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.

[0139] 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.

[0140] Gloss (60°) test: Tested in accordance with standard GB / T 9754-2007.

[0141] 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.

[0142] 40℃ water resistance test: Soak the dried coating film in 40℃ water and observe the time it takes for no bubbles or gloss loss.

[0143] The performance test results are shown in Table 2: Table 2 Performance test of coatings

[0144] According to the above results, we can know that: 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.

[0145] 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.

[0146] The solid 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 failure to obtain a storage-stable aqueous acrylic dispersion.

[0147] The solid acid value of the aqueous acrylic dispersion of Comparative Example 3 is too high. Too high an acid value will catalyze the side reaction between the polyisocyanate crosslinker and water, shortening the usable time of the aqueous two-component polyurethane coating corresponding to the aqueous acrylic dispersion of Comparative Example 2. Too high an acid value will also make the first polymer too hydrophilic, resulting in poor water resistance of the aqueous two-component polyurethane coating.

[0148] 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 usable time of the aqueous two-component polyurethane coating corresponding to the aqueous acrylic dispersion of Comparative Example are better, the water resistance is poor due to the introduction of a large number of hydrophilic polyether groups.

[0149] Commercial PA-4842 does not contain the first copolymer within the scope of the present invention, and its corresponding waterborne two-component polyurethane coating exhibits poor gloss, pot life and water resistance.

[0150] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, and the present invention is also intended to include these modifications and modifications.

Claims

1. An aqueous acrylic dispersion, characterized in that: The invention comprises a first copolymer; the comonomer of the first copolymer comprises a first monomer, the first monomer having a structure of formula (1); the first monomer accounts for 1-20wt% 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; 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, characterized in that: 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 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 comonomers of the first copolymer; The third monomer is a carboxyl-functionalized unsaturated monomer, and the third monomer accounts for 0-30wt% of the total amount of comonomers of the first copolymer; The fourth monomer is an 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.

3. The aqueous acrylic dispersion according to claim 2, characterized in that: It also includes a second copolymer, the comonomer of which includes 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; and the seventh monomer is another unsaturated monomer different from the first monomer, the fifth monomer, and the sixth monomer.

4. The aqueous acrylic dispersion according to claim 1, characterized in that: 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, characterized in that: 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 third monomer and the sixth monomer are independently at least one of methacrylic acid, acrylic acid, itaconic acid and crotonic acid; The fourth monomer and the seventh monomer are independently at least one of (meth)acrylate, vinyl aromatic hydrocarbon and vinyl ester having a C1-C18 hydrocarbon group in the alcohol portion and no hydroxyl group and carboxyl group.

6. The aqueous acrylic dispersion according to claim 1, characterized in that: A neutralizing agent is also included, 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. The solid content of the aqueous acrylic dispersion is 30-60wt%; the content of the organic solvent in the aqueous acrylic dispersion is 2-10wt%.

8. A water-based paint, characterized in that: The method comprises an aqueous acrylic dispersion as described in any one of claims 1 to 7 and a crosslinking agent.

9. The water-based paint according to claim 8, characterized in that: The crosslinking agent is a polyisocyanate crosslinking agent containing free NCO groups.

10. A coating film, characterized in that: The method is to apply the water-based coating according to claim 8 or 9 to a substrate.

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