CN110885406B

CN110885406B - Preparation method of acrylic emulsion, acrylic emulsion and application thereof

Info

Publication number: CN110885406B
Application number: CN201911241145.XA
Authority: CN
Inventors: 方武成; 赵鹏伟; 马吉全; 纪学顺; 邓俊英
Original assignee: Wanhua Chemical Group Co Ltd; Wanhua Chemical Ningbo Co Ltd; Wanhua Chemical Guangdong Co Ltd
Current assignee: Wanhua Chemical Group Co Ltd; Wanhua Chemical Ningbo Co Ltd; Wanhua Chemical Guangdong Co Ltd
Priority date: 2019-12-06
Filing date: 2019-12-06
Publication date: 2022-03-11
Anticipated expiration: 2039-12-06
Also published as: CN110885406A

Abstract

The invention provides a preparation method of acrylic emulsion, the acrylic emulsion and application thereof, wherein the preparation method comprises the following steps: mixing an emulsifier, an acrylate monomer and a water phase to form a first-step pre-emulsion; mixing an emulsifier, an acrylate monomer and a functional monomer acid with the water phase to form a second-step pre-emulsion for later use; firstly, adding the first-step pre-emulsion and a water-soluble initiator into a reaction container to initiate polymerization; and cooling, and adding the second-step pre-emulsion and an oil-soluble initiator to initiate polymerization. The invention adopts a step-by-step emulsion polymerization method, functional monomer acid with strong hydrophilicity can be uniformly distributed in a polymer chain segment on the surface of an emulsion particle to form self-thickening emulsion with high pseudoplasticity, and the phenomenon that the functional monomer acid with strong hydrophilicity is easy to self-polymerize in a water phase in a shell layer enrichment polymerization in the traditional emulsion polymerization is overcome.

Description

Preparation method of acrylic emulsion, acrylic emulsion and application thereof

Technical Field

The invention relates to an acrylic emulsion, in particular to a preparation method of a self-thickening acrylic emulsion with high pseudoplasticity, an acrylic emulsion and application thereof, belonging to the technical field of high polymer materials.

Background

The silver paint, namely the aluminum paint, is characterized in that aluminum powder is used as a pigment to be dispersed in resin, fine aluminum powder scales form a parallel arrangement structure in colored paint, and the paint has a strong reflection function on visible light, ultraviolet rays, infrared rays and radiant heat, so that a paint film after spraying has a strong metal flashing effect to obtain an excellent appearance, can effectively delay the aging of the ultraviolet rays, and can prevent water, gas and ions from passing through, therefore, the paint has better weather resistance and corrosion resistance compared with the common colored paint, and is widely applied to the decoration and corrosion resistance of vehicles, hubs, security doors, iron towers and metal pipelines.

The silver paint is generally prepared by adding an orientation assistant into a colored paint to ensure that flaky aluminum powder is aligned in parallel with the surface orientation of a paint film. The publication CN109762425A provides an acrylic emulsion with high thixotropy, which comprises a hydrophobic core layer and an externally wrapped hydrophilic shell layer. The hydrophilic shell layer contains polymer chains containing a large number of carboxyl groups, and after the pH regulator is added, the carboxyl groups are neutralized and are negatively charged, and the polymer chain segments of the outer layer are stretched in the water phase due to the mutual repulsion between the same charges, so that the latex particles are intertwined with each other. Exhibit high viscosity at low shear; while high shear can break this entanglement and exhibit low viscosity. The high-thixotropy emulsion is used as matrix resin of the silver paint, so that the use of an orientation aid and a thickening agent can be greatly reduced, the cost is reduced, and the applicability of a paint formula is improved. However, the acrylic emulsion prepared by this method has a large amount of carboxyl groups in the shell layer, which are provided only by methacrylic acid, and cannot use acrylic acid with stronger acidity and better repulsion effect, because acrylic acid has stronger water solubility, and a large amount of acrylic acid is easily self-polymerized in the water phase when being concentrated in the shell layer for polymerization, so that the acrylic acid cannot be uniformly distributed in the polymer chain segment of the shell layer, and thus the desired effect cannot be achieved. Meanwhile, a certain amount of cross-linking agent is added in the preparation method, so that the wrapping property of the resin and the silver powder is reduced, and the plate surface is easy to blacken.

Disclosure of Invention

The invention aims at providing a preparation method of acrylic emulsion, which comprises the steps of firstly polymerizing a nuclear layer monomer without functional monomer acid, then fully mixing and swelling a pre-emulsified liquid containing a large amount of functional monomer acid with the reaction system, and finally polymerizing the monomer only on the surface of latex particles by using an oil-soluble initiator, so that the phenomenon that the functional monomer acid with strong hydrophilicity easily self-polymerizes in a water phase when the functional monomer acid with strong hydrophilicity is subjected to enrichment polymerization in a shell layer in the traditional emulsion polymerization is overcome, and the functional monomer acid with strong hydrophilicity is successfully and uniformly distributed in a polymer chain segment on the surface of the latex particles; when the amine regulator is added to neutralize the acid, the polymer chain segments on the surface layer of the latex particles can be mutually repelled and stretched to form the self-thickening emulsion with high thixotropy. Another object of the present invention is to provide an acrylic emulsion having high pseudoplasticity, which is obtained by the above-mentioned method. The invention also aims to provide application of the acrylic emulsion prepared by the method in preparing silver paint coating, in particular water-based silver paint coating.

Acrylic emulsion and application thereof.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a preparation method of acrylic emulsion comprises the following steps:

1) mixing an emulsifier, an acrylate monomer and a water phase to form a first-step pre-emulsion for later use;

2) mixing an emulsifier, an acrylate monomer and a functional monomer acid with the water phase to form a second-step pre-emulsion for later use;

3) mixing an emulsifier and water, adding the mixture into a reaction container, introducing nitrogen to remove air, and then heating to 70-90 ℃;

4) adding the pre-emulsion obtained in the first step in the step 1) into a reaction container, and adding a water-soluble initiator to initiate polymerization;

5) after the reaction is finished, cooling the system to 40-60 ℃, preferably 50 ℃, and preserving heat for 0.5-2 hours, preferably 1 hour;

6) adding the pre-emulsion in the second step into a reaction system, and adding an oil-soluble initiator to initiate polymerization, wherein the reaction time is 0.5-2h, preferably 1 h;

7) after the reaction is finished, the temperature is reduced to below 40 ℃, preferably 30 ℃, then a neutralizing agent is added to adjust the pH value to 6-8, preferably 7, and the mixture is filtered and discharged.

Further, the addition amount of each substance in the method is respectively as follows according to the parts by mass:

0.5-2 parts of emulsifier, 70-90 parts of acrylate monomer and 15-30 parts of water are added in the step 1);

0.1-1 part of emulsifier, 5-25 parts of acrylate monomer, 1-5 parts of functional monomer acid and 3-10 parts of water are added in the step 2);

0.1-0.5 part of emulsifier and 100-200 parts of water are added in the step 3);

the adding amount of the water-soluble initiator in the step 4) is 0.1-1 part;

the addition amount of the oil-soluble initiator in the step 6) is 0.5-2 parts.

Further, the polymerization initiation reaction in the step 4) is divided into two steps, firstly, part of the first-step pre-emulsion is added into a reaction container, and part of the water-soluble initiator is added to initiate polymerization; after reacting for 15-60min, continuously dropwise adding the rest of the first-step pre-emulsion and the water-soluble initiator, and finishing dropwise adding within 1-4h, preferably 2 h; after dripping, the temperature is kept for 0.5 to 2 hours, preferably 1 hour.

Further, the first adding amount of the first-step pre-emulsion in the step 4) is 1-10 wt% and preferably 4 wt% of the total amount (wt% represents mass percentage); the first addition of water-soluble initiators is 10-60% by weight, preferably 40% by weight, of the total amount thereof.

Further, the oil-soluble initiator comprises an oil-soluble oxidizing agent and a reducing agent; the weight ratio of the oil-soluble oxidant to the reducing agent is 1: 1-0.5;

preferably, the oil-soluble oxidizing agent is one or more of di-tert-amyl peroxide, di-tert-butyl peroxide and cumene hydroperoxide, more preferably cumene hydroperoxide; the reducing agent is one or more of sodium hydrosulfite, sodium metabisulfite and sodium bisulfite, and the sodium hydrosulfite is more preferable.

Further, the acrylate monomer is at least one of methyl acrylate, ethyl acrylate, butyl acrylate, isooctyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isooctyl methacrylate, hydroxyethyl methacrylate and hydroxypropyl methacrylate.

Further, the functional monomer acid is at least one of acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid, and maleic acid.

Further, the emulsifier is at least one of sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, fatty alcohol-polyoxyethylene ether and salts thereof, and fatty alcohol ether phosphate and salts thereof;

preferably, the water-soluble initiator is one of potassium persulfate, sodium persulfate and ammonium persulfate, and more preferably ammonium persulfate;

preferably, the neutralizing agent is one or more of ammonia, ethanolamine, triethylamine and N, N-dimethylethanolamine, more preferably N, N-dimethylethanolamine.

The invention also provides the self-thickening acrylic emulsion with high pseudoplasticity prepared by the method.

The invention also provides application of the self-thickening acrylic emulsion with high pseudoplasticity prepared by the method in preparing silver paint coating, in particular water-based silver paint coating.

The water-based silver paint coating also comprises at least one of the following components: film forming assistant, wetting agent, defoaming agent, water-based aluminum powder, pH regulator, dispersant and amino resin. Other components and amounts of the aqueous silver paint coating can be selected and adjusted by those skilled in the art using techniques commonly used in the art.

The invention adopts a stepwise emulsion polymerization method, firstly, pre-emulsion of acrylate monomer without functional monomer acid is polymerized at 70-85 ℃, then cooling to 40-60 ℃ to inactivate the oil-soluble initiator, directly adding the pre-emulsion containing a large amount of functional monomer acid into the reaction system in the first step for mixing and swelling, adding the specific oil-soluble initiator for initiating polymerization, so that the functional monomer acid can only be polymerized on the surface of the latex particles, overcoming the phenomenon that the functional monomer acid with strong hydrophilicity is easy to self-polymerize in a water phase when the functional monomer acid with strong hydrophilicity is subjected to shell layer enrichment polymerization in the traditional emulsion polymerization, successfully and uniformly distributing the functional monomer acid with strong hydrophilicity in a polymer chain segment on the surface of the latex particles, and finally neutralizing the acid, the polymer chain segments on the surface of the latex particles are mutually repelled and stretched to form the self-thickening emulsion with high pseudoplasticity.

Detailed Description

The present invention is further illustrated by the following specific examples, which are intended to be illustrative of the invention and are not to be construed as limiting the scope of the invention.

The main raw materials and sources are shown in table 1:

TABLE 1 raw materials and sources for preparing acrylic emulsions

For short	Compound (I)	Manufacturer of the product
			MMA	Methacrylic acid methyl ester	Wanhua Chemical Group Co., Ltd.
BA	Acrylic acid butyl ester	Wanhua Chemical Group Co., Ltd.
			HEMA	Hydroxyethyl methacrylate	Wanhua Chemical Group Co., Ltd.
(M)AA	(meth) acrylic acid	Wanhua Chemical Group Co., Ltd.
			APS	Ammonium persulfate	Jinan Fengle chemical Co Ltd
SDS	Sodium dodecyl sulfate	Shanghai Youyang industries Ltd
			CHP	Cumene hydroperoxide	Aladdin reagent
DMEA	N, N-dimethylethanolamine	BASF CHINA Co.,Ltd.

Other raw materials can be obtained by a commercial route unless otherwise specified.

The pseudoplasticity test method of the water-based silver paint comprises the following steps: and (3) using a Brookfeald viscometer, and characterizing the pseudoplasticity of the silver paint by using a Ti value, wherein the Ti value is the ratio of the viscosity value of the silver paint measured at 6r to the viscosity value measured at 60r, and the larger the ratio is, the stronger the pseudoplasticity is.

[ example 1 ]

(1) 1g of SDS, 26g of water, 69g of MMA and 17g of BA were sequentially added to a vessel to conduct pre-emulsification, thereby obtaining a first-step pre-emulsion.

Sequentially adding 0.5g of SDS, 4g of water, 2g of MMA, 3g of HEMA, 5g of BA and 3g of AA into a container for pre-emulsification to obtain a second-step pre-emulsion;

(2) 0.2g SDS, 160g water were added to the reaction kettle, stirring and heating were turned on. When the temperature in the kettle rises to 85 ℃, taking out the first-step pre-emulsion accounting for 4% of the total mass of the kettle, putting the first-step pre-emulsion into a reaction container, then adding 10 wt% of APS aqueous solution accounting for 40% of the total mass of the kettle (3 g in total), after polymerization reaction for 30min, dropwise adding the rest of the first-step pre-emulsion and the 10 wt% of APS aqueous solution for 2h in total, and preserving heat for 1h after dropwise adding;

(3) and (3) reducing the temperature of the reaction kettle to 50 ℃, continuously preserving the heat for 1h, then putting all the pre-emulsion in the second step into the reaction kettle to be uniformly mixed with a reaction system, then sequentially adding 0.8g of CHP and 6g of 10 wt% sodium hydrosulfite aqueous solution into the reaction kettle to initiate polymerization, reacting for 1h, then reducing the temperature to 30 ℃, adjusting the pH to 7.0 by using DMEA, filtering and discharging to obtain the final emulsion.

[ example 2 ]

An acrylic emulsion was prepared by the method of example 1, except that the amounts of the respective raw materials shown in Table 2 were different.

[ example 3 ]

[ example 4 ]

[ example 5 ]

[ example 6 ]

An acrylic emulsion was prepared by the method of example 1, except for the amounts of the respective raw materials and the following differences in the operation of step (3) as shown in Table 2: 1) reducing the temperature of the reaction kettle to 40 ℃, continuously preserving the heat for 0.5h, and then adding the pre-emulsion in the second step; 2) the oil-soluble oxidant is di-tert-amyl peroxide, and the reducing agent is 10 wt% of sodium metabisulfite aqueous solution; 3) the reaction time of the second pre-emulsion and the oil-soluble initiator is 0.5 h.

[ example 7 ]

An acrylic emulsion was prepared by the method of example 1, except for the amounts of the respective raw materials and the following differences in the operation of step (3) as shown in Table 2: 1) reducing the temperature of the reaction kettle to 60 ℃, continuously preserving the heat for 2 hours, and then adding the pre-emulsion in the second step; 2) the oil-soluble oxidant is di-tert-butyl peroxide, and the reducing agent is 10 wt% of sodium bisulfite aqueous solution; 3) the reaction time of the pre-emulsion and the oil-soluble initiator in the second step is 2 h.

Comparative example 1

(2) 0.2g SDS, 160g water were added to the reaction kettle, stirring and heating were turned on. When the temperature in the kettle rises to 85 ℃, taking out the first-step pre-emulsion accounting for 4 percent of the total mass of the kettle, putting the first-step pre-emulsion into a reaction container, then adding APS aqueous solution accounting for 40 percent of the total mass of the first-step pre-emulsion (3 g in total), after polymerization reaction for 30min, dropwise adding the rest first-step pre-emulsion and APS aqueous solution accounting for 40 percent of the total mass of the first-step pre-emulsion for 2h in total, and preserving heat for 1h after dropwise adding; then, continuously dropwise adding the pre-emulsion in the second step and the residual 10 wt% of APS aqueous solution for 0.5h, and preserving heat for 1h after dropwise adding;

(3) cooling to 30 ℃, adjusting the pH value to 7.0 by using DMEA, filtering and discharging to obtain the final emulsion.

Comparative example 2

An acrylic emulsion was prepared by the method of comparative example 1, except that the amounts of the respective raw materials shown in Table 2 were different.

Table 2, examples and comparative examples the amounts of the respective raw materials

The aqueous silver paint coating was prepared from the acrylic emulsions obtained in the above examples and comparative examples, and the formulation is shown in table 3:

TABLE 3 formula of aqueous silver paint

Note: the raw materials of the non-marked factories can be commonly used as long as the raw materials are of the same type

The preparation method comprises the following steps:

firstly, 147g of water, 80g of PAIST W-153, 4.0g of BYK-192, 3.5g of 10% DMEA and 80g of ethylene glycol monobutyl ether are sequentially added into a dispersion tank, stirred for 20min at 800 r/min and placed at room temperature for soaking for 4h to obtain aqueous aluminum powder slurry for later use.

Adding 400g of acrylic emulsion and 209.1g of deionized water, adding 32.8g of 10% DMEA to adjust the pH, sequentially adding 3.0g of Tego270, 3.0g of BYK-028 and 37.6g of Cymel 325, and stirring at 800 revolutions per minute for 20min to obtain a water-based varnish component; then adding the aqueous aluminum paste, and stirring at 800 r/min for 20min to obtain the aqueous silver paint with solid content of 18.6% and pH of 8.5.

The pseudoplasticity of the aqueous silver paint prepared from the acrylic emulsion of each example and comparative example is tested, and the performance evaluation results are shown in Table 4:

TABLE 4 comparison of pseudoplasticity of aqueous silver paints

	Pseudoplasticity
		Example 1	7.5
Example 2	5.3
		Example 3	6.0
Example 4	7.6
		Example 5	6.2
Example 6	5.7
		Example 7	6.4
Comparative example 1	2.3
		Comparative example 2	5.0

Analyzing the above results, (1) it can be seen from comparative examples 1 and 2 that the pseudoplasticity is very much reduced after the functional monomer acid is changed from methacrylic acid to acrylic acid by the conventional emulsion polymerization method, as described above, since acrylic acid is too hydrophilic and tends to self-polymerize significantly in the aqueous phase when the shell layer is polymerized in a large amount, and thus acrylic acid is not uniformly distributed in the polymer segments of the shell layer, resulting in failure to cause mutual repulsion between segments after neutralization; (2) as can be seen from comparison of examples 1-2 with comparative examples 1-2, the difference in the results obtained by the two polymerization methods is not large when the functional monomer acid is methacrylic acid, and the difference in the results obtained by the two different polymerization methods is significant when the functional monomer acid is acrylic acid, indicating that the hydrophilic acrylic acid can be uniformly distributed in the polymer segment of the shell layer by the polymerization method of the present invention; (3) comparing examples 3-4 with examples 1-2, it can be seen that when the amount of functional monomer acid is reduced, the pseudoplasticity is also reduced, since the reduction of carboxyl groups leads to a reduction in the repulsive force between the segments after neutralization; when the amount of the functional monomer acid is increased, the pseudoplasticity is not changed greatly, which indicates that the distribution of the outer layer acid is close to saturation, and the increase of the amount of the acid also has little influence on the pseudoplasticity; (4) as can be seen from the comparison of examples 5 to 6 with example 1, the pseudoplasticity of the latex is reduced compared with the shell ratio of example 1, whether the shell ratio is increased or decreased, because when the shell ratio is increased and the acid content of the functional monomer is not changed, the distribution ratio of carboxyl groups on the polymer segments is decreased, so that the repulsive force between the segments after neutralization is weakened, and when the shell ratio is decreased, although the distribution ratio of carboxyl groups is increased, the shell polymer ratio is too small in the whole latex particle, so that the effect of self-thickening of the latex by segment repulsion is also remarkably weakened, thereby it can be seen that the core-shell monomer ratio of example 1 is a relatively optimized choice; (5) example 7 in comparison with example 1 shows that if the hydrophilic monomer HEMA is changed to MMA and BA, which are relatively hydrophobic, the pseudoplasticity of the paint is also reduced, which indicates that the hydrophilicity and hydrophobicity of other components in the polymer segment can also affect the pseudoplasticity of the final paint in addition to the hydrophilic functional monomer acid.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and additions can be made without departing from the method of the present invention, and these modifications and additions should also be regarded as the protection scope of the present invention.

Claims

1. The preparation method of the acrylic emulsion is characterized by comprising the following steps:

5) after the reaction is finished, cooling the system to 40-60 ℃, and preserving heat for 0.5-2 h;

6) adding the pre-emulsion in the second step into a reaction system, and adding an oil-soluble initiator to initiate polymerization;

7) cooling to below 40 ℃ after the reaction is finished, adding a neutralizing agent to adjust the pH value to 6-8, filtering and discharging;

the initiation polymerization reaction in the step 4) is divided into two steps, firstly, part of the first-step pre-emulsion is added into a reaction container, and part of the water-soluble initiator is added to initiate polymerization; after reacting for 15-60min, continuously dropwise adding the rest of the first-step pre-emulsion and the water-soluble initiator, and finishing dropwise adding within 1-4 h; after dripping, keeping the temperature for 0.5-2 h;

the functional monomer acid is at least one of acrylic acid, itaconic acid, crotonic acid, fumaric acid and maleic acid.

2. The method for preparing acrylic emulsion according to claim 1, wherein in step 5), the temperature of the system is reduced to 50 ℃ after the reaction, and the temperature is maintained for 1 h.

3. The method for preparing an acrylic emulsion according to claim 1, wherein in step 7), after the reaction, the temperature is reduced to 30 ℃, and then a neutralizing agent is added to adjust the pH to 7, and the mixture is filtered and discharged.

4. The method for preparing acrylic emulsion according to claim 1, wherein the addition amount of each substance in the method is respectively as follows by mass parts:

0.1-0.5 part of emulsifier and 100-200 parts of water are added in the step 3);

the adding amount of the water-soluble initiator in the step 4) is 0.1-1 part;

the addition amount of the oil-soluble initiator in the step 6) is 0.5-2 parts.

5. The method for preparing acrylic emulsion according to claim 4, wherein the polymerization initiation in step 4) is divided into two steps, wherein a part of the first-step pre-emulsion is first added into a reaction vessel, and a part of the water-soluble initiator is added to initiate polymerization; after reacting for 15-60min, continuously dropwise adding the rest of the first-step pre-emulsion and the water-soluble initiator, and finishing dropwise adding within 2 h; and preserving the heat for 1h after dripping.

6. The method for preparing acrylic emulsion according to claim 5, wherein the first addition amount of the first-step pre-emulsion in the step 4) is 1-10 wt% of the total amount; the first addition amount of the water-soluble initiator is 10-60 wt% of the total amount of the initiator.

7. The method for preparing acrylic emulsion according to claim 6, wherein the first addition amount of the first pre-emulsion in the step 4) is 4 wt% of the total amount; the first addition of water-soluble initiator was 40 wt% of its total amount.

8. The method for preparing an acrylic emulsion according to any one of claims 1 to 7, wherein the oil-soluble initiator comprises an oil-soluble oxidizing agent, a reducing agent; the weight ratio of the oil-soluble oxidant to the reducing agent is 1: 1-0.5.

9. The method for producing an acrylic emulsion according to claim 8, wherein said oil-soluble oxidizing agent is one or more of di-t-amyl peroxide, di-t-butyl peroxide and cumene hydroperoxide; the reducing agent is one or more of sodium hydrosulfite, sodium metabisulfite and sodium bisulfite.

10. The method for producing an acrylic emulsion according to claim 9, wherein said oil-soluble oxidizing agent is cumene hydroperoxide; the reducing agent is sodium hydrosulfite.

11. The method of claim 8, wherein the acrylic monomer is at least one of methyl acrylate, ethyl acrylate, butyl acrylate, isooctyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isooctyl methacrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate.

12. The method for preparing an acrylic emulsion according to claim 11, wherein the emulsifier is at least one of sodium lauryl sulfate, sodium dodecylbenzenesulfonate, fatty alcohol-polyoxyethylene ether and salts thereof, and fatty alcohol ether phosphate and salts thereof.

13. The method of claim 12, wherein the water-soluble initiator is one of potassium persulfate, sodium persulfate, and ammonium persulfate.

14. The method of claim 13, wherein the water-soluble initiator is ammonium persulfate.

15. The method for producing an acrylic emulsion as claimed in claim 12, wherein said neutralizing agent is one or more of ammonia, ethanolamine, triethylamine and N, N-dimethylethanolamine.

16. The method of claim 15, wherein the neutralizing agent is N, N-dimethylethanolamine.

17. A self-thickening acrylic emulsion having high pseudoplasticity prepared by the method of any one of claims 1 to 16.

18. Use of the self-thickening acrylic emulsion with high pseudoplasticity prepared by the method of any one of claims 1 to 16 in preparing silver paint coating.

19. Use of the self-thickening acrylic emulsion with high pseudoplasticity prepared by the method of any one of claims 1 to 16 in preparation of water-based silver paint coating.