Functional emulsion for cathode electrophoretic coating as well as preparation method and application of functional emulsion

Abstract

The invention belongs to the technical field of electrophoretic coatings, and particularly relates to a functional emulsion for a cathode electrophoretic coating as well as a preparation method and application of the functional emulsion. The method comprises the following steps: (1) adding an initiator into amino-containing epoxy butyronitrile resin, preserving heat, and then carrying out polymerization reaction to obtain ultra-large molecular weight amino-containing epoxy butyronitrile resin; (2) preparing modified hectorite; and (3) uniformly mixing ultra-large molecular weight amino-containing epoxy butyronitrile resin and the modified hectorite, adding a neutralizer, carrying out a reaction, and then adding water for emulsification to obtain the functional emulsion for the cathode electrophoretic coating. The modified hectorite endows the functional emulsion for the cathode electrophoretic coating with good wear resistance and corrosion resistance; the ultra-large molecular weight amino-containing epoxy butyronitrile resin in the functional emulsion for the cathode electrophoretic coating greatly improves the edge corrosion resistance of an electrophoretic coating film, and enhances the flexibility, impact resistance and tear resistance of the electrophoretic coating film.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings, and in particular relates to a functional emulsion for cathode electrophoretic coatings and a preparation method and application thereof. Background Art

[0002] Cathodic electrophoretic coating is a special coating that applies the paint to the surface of the object through the principle of electrophoresis. This coating has the characteristics of uniform coating thickness, suitable for parts of various shapes, excellent corrosion resistance, high permeability, high leveling and high decorativeness. With the continuous advancement of science and technology and the increasing requirements for environmental protection, cathodic electrophoretic coating has been widely used in the fields of automotive industry, building materials, light industry, household appliances, etc. In order to meet the special requirements of coating performance in different fields, the research and development and application of functional emulsions are particularly important.

[0003] During the curing and baking process of the cathodic electrophoretic paint coating, the surface temperature of the coating at the edge of the painted workpiece is higher than that of other parts, which makes its melt viscosity relatively low, resulting in a surface tension difference between the coating at the edge of the workpiece and the inner coating. The coating at the edge with smaller surface tension gradually flows toward the inside of the workpiece until the surface tension difference is not enough to drive the coating flow, resulting in the coating thickness at the edge of the workpiece being significantly lower than that at other parts. This is also the fundamental reason why the electrophoretic coating has poor resistance to sharp edge corrosion.

[0004] In order to solve the problem of sharp edge corrosion resistance and wear resistance of coatings, researchers generally synthesize microgel emulsions and then add the microgel emulsions to cathodic electrophoretic paint emulsions. However, this microgel resin has poor shrinkage inhibition on the edge of the coating during baking, and the sharp edge corrosion resistance and wear resistance of the coating are poor. Therefore, it is necessary to design a functional emulsion for the preparation of cathodic electrophoretic coatings with excellent sharp edge corrosion resistance and wear resistance. Summary of the invention

[0005] One of the purposes of the present invention is to provide a method for preparing a functional emulsion for cathode electrophoretic coating, wherein the functional emulsion has an ultra-high molecular weight and is added to the cathode electrophoretic emulsion to significantly increase the melt viscosity of the coating at high temperature, and prevent the coating from shrinking inward at the edge of the workpiece due to surface tension difference during the curing process of the coating, thereby improving the anti-sharp edge corrosion ability of the electrophoretic coating. The addition of modified hectorite added to the functional emulsion can give the coating good wear resistance.

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

[0007] A method for preparing a functional emulsion for cathode electrophoretic coating comprises the following steps:

[0008] (1) adding an initiator to an amino-containing epoxy nitrile resin, and maintaining the temperature at 55-60° C. for 30-45 minutes to obtain an amino-containing epoxy nitrile resin with a super large molecular weight;

[0009] (2) Preparation of modified hectorite:

[0010] a. Mix laponite, NiCo2O4, surfactant, additive and water, and ball mill to obtain a mixed slurry;

[0011] b. dissolving bismuth nitrate and ammonium metamolybdate in an aqueous nitric acid solution, then adding tartaric acid and N,N-dimethylacrylamide, stirring to obtain a mixed solution, slowly adding the mixed solution to the mixed slurry of step a under heating conditions, stirring to obtain a sol, drying the sol, calcining, and grinding to obtain;

[0012] (3) The ultra-large molecular weight epoxy nitrile resin containing amino groups and the modified hectorite are uniformly mixed, a neutralizing agent is added to react, and then water is added for emulsification to obtain the functional emulsion for the cathode electrophoretic coating.

[0013] The present invention mixes ultra-large molecular weight amino-containing epoxy nitrile resin with modified hectorite to prepare a functional emulsion for cathode electrophoretic coating. The hectorite has good suspension performance and emulsion stability, can prevent the sedimentation and agglomeration of particles in the coating, and the treatment of ball milling and surfactant can reduce the surface tension between the components of the coating, promote the uniform dispersion and close combination between the hectorite, NiCo2O4 and the components, thereby improving the wear resistance of the coating. The loading of bismuth molybdate enables the electrophoretic coating to form a dense protective layer on the surface of the material during coating, prevent heat from penetrating into the interior of the coating, and protect the coating from decomposition, so that the coating has good wear resistance and corrosion resistance.

[0014] Furthermore, in step a, the mass ratio of the laponite, NiCo2O4, surfactant, additive and deionized water is 1:(0.15-0.5):(0.1-0.3):(0.05-0.2):(2-4), the surfactant is dodecyl dimethyl betaine; and the additive is carboxymethyl cellulose or hydroxypropyl methyl cellulose.

[0015] Furthermore, in step a, the ball milling speed is 300-400 rpm / min, and the ball milling time is 2-5 h.

[0016] Furthermore, the particle size of the hectorite is 200-500nm, and the diameter of the NiCo2O4 nanowire is 50-100nm.

[0017] Furthermore, the concentration of the nitric acid aqueous solution in step b is 7-9wt%; the mass ratio of bismuth nitrate, ammonium metamolybdate, tartaric acid, and N,N-dimethylacrylamide is 1:(0.14-0.16):(1-1.3):(1-1.5).

[0018] Furthermore, in step (3), the mass ratio of the ultra-large molecular weight amino-containing epoxy nitrile resin, modified hectorite, and neutralizer is 1:(0.2-0.6):(0.01-0.02); and the neutralizer is at least one of glacial acetic acid, lactic acid, formic acid, and aminosulfonic acid.

[0019] Furthermore, the temperature of the neutralization reaction in step (3) is 60-65° C., and the time of the neutralization reaction is 30-45 min.

[0020] Furthermore, the initiator in step (1) is any one of benzoyl peroxide, tert-butyl benzoyl peroxide, methyl ethyl ketone peroxide or tert-butyl peroxide (2-ethylhexanoate).

[0021] Furthermore, the preparation method of the amino-containing epoxy butyronitrile resin in step (1) comprises the following steps:

[0022] The epoxy nitrile prepolymer, bisphenol A and methyl isobutyl ketone are mixed and heated to 100°C, a catalyst is added, and the temperature is further raised to 155-160°C for reaction for 3-4 hours to obtain epoxy nitrile resin; methyl isobutyl ketone is added to the epoxy nitrile resin, and after cooling, an organic amine is added to carry out an amination reaction to obtain an amino-containing epoxy nitrile resin.

[0023] Furthermore, the epoxy nitrile prepolymer comprises a bisphenol A glycidyl ether with a rubber content of 20 to 60% and a nitrile rubber adduct; the catalyst is any one of dimethylmonoethanolamine, dimethylbenzylamine and tetrabutylammonium bromide; and the organic amine is any one of diethanolamine and methylmonoethanolamine.

[0024] Furthermore, the mass ratio of the epoxy resin, bisphenol A and organic amine is (75-85):(15-25):(9-15); the amount of the catalyst used is 0.03%-0.05% of the total mass of the epoxy nitrile resin and bisphenol A; the temperature of the amination reaction is 120-125° C., and the time is 2-2.5 hours.

[0025] A second object of the present invention is to provide a functional emulsion for cathode electrophoretic coating.

[0026] To achieve the above object, the present invention adopts the following technical solutions:

[0027] A functional emulsion for cathode electrophoretic coating is prepared by the preparation method.

[0028] The third object of the present invention is to provide the use of the functional emulsion for cathode electrophoretic coating in the preparation of electrophoretic coating.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The functional emulsion for cathode electrophoretic coating of the present invention uses an ultra-large molecular weight amino-containing epoxy nitrile resin, which has a high melt viscosity at high temperature. When added to the cathode electrophoretic coating emulsion, it can effectively inhibit the shrinkage of the electrophoretic coating at the edge of the workpiece, greatly improving the edge corrosion resistance of the electrophoretic coating.

[0031] (2) The epoxy nitrile prepolymer used in the present invention has a low glass transition temperature and a soft molecular chain segment. The ultra-large molecular weight amino-containing epoxy nitrile resin synthesized therefrom can enhance the flexibility, impact resistance and tear resistance of the electrophoretic coating.

[0032] (3) Modified hectorite is also added to the functional emulsion for cathode electrophoretic coating of the present invention, and the modified hectorite gives the functional emulsion for cathode electrophoretic coating good wear resistance and corrosion resistance. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further explained below in conjunction with specific embodiments, comparative examples and test examples.

[0034] In the following examples, comparative examples and test examples, the raw materials and preparation methods used are conventional materials and techniques in the art unless otherwise specified.

[0035] Example 1

[0036] A method for preparing a functional emulsion for cathode electrophoretic coating comprises the following steps:

[0037] (1) 194.8 parts of epoxy nitrile prepolymer (86840 resin, rubber content 40%), 38.9 parts of bisphenol A and 10.2 parts of methyl isobutyl ketone are mixed and heated to 100° C., 0.1 parts of tetrabutylammonium bromide are added, and the temperature is further raised to 160° C. and reacted for 3.5 hours to obtain epoxy nitrile resin; 68.7 parts of ethylene glycol monobutyl ether are added to the epoxy nitrile resin at 160° C., 23.1 parts of diethanolamine are added when the temperature is lowered to 100° C., and then the temperature is raised to 125° C. for amination reaction for 2.5 hours to obtain amino-containing epoxy nitrile resin; 55.0 parts of methyl isobutyl ketone are added to the amino-containing epoxy nitrile resin, and 5.2 parts of tert-butyl peroxide (2-ethylhexanoate) are added after the temperature is lowered to 60° C., and the mixture is kept at 60° C. for 30 minutes for polymerization reaction to obtain ultra-high molecular weight amino-containing epoxy nitrile resin;

[0038] (2) Preparation of modified hectorite:

[0039] a. 1 part of laponite, 0.3 parts of NiCo2O4, 0.2 parts of dodecyl dimethyl betaine, 0.1 parts of carboxymethyl cellulose and 2.5 parts of deionized water were placed in a ball mill and mixed uniformly, and ball milled at 350r / min for 3.5h to obtain a mixed slurry;

[0040] b. 1 part of bismuth nitrate and 0.15 parts of ammonium metamolybdate were dissolved in 25 mL of nitric acid aqueous solution (8 wt %), and then 1.1 parts of tartaric acid and 1.2 parts of N, N-dimethylacrylamide were added and stirred to obtain a mixed solution, and the mixed solution was slowly added to the mixed slurry of step a under heating conditions, stirred to obtain a sol, and the sol was dried at 120 ° C for 12 h, placed in a tubular furnace at 500 ° C for calcination for 2 h, and ground to obtain;

[0041] (3) 1 part of ultra-high molecular weight epoxy nitrile resin containing amino groups and 0.4 parts of modified hectorite are mixed evenly, 0.015 parts of glacial acetic acid are added, and the mixture is kept at 60° C. for 30 minutes for neutralization reaction to obtain an acidified solution, and the acidified solution is added to 890.9 parts of deionized water for emulsification to obtain the product.

[0042] Example 2

[0043] A method for preparing a functional emulsion for cathode electrophoretic coating comprises the following steps:

[0044] (1) 194.8 parts of epoxy nitrile prepolymer (86140 resin, rubber content 20%), 57.3 parts of bisphenol A and 10.2 parts of methyl isobutyl ketone are mixed and heated to 100° C., 0.1 parts of tetrabutylammonium bromide are added, and the temperature is further raised to 160° C. and reacted for 3.5 hours to obtain epoxy nitrile resin; 68.7 parts of ethylene glycol monobutyl ether are added to the epoxy nitrile resin at 160° C., 34.3 parts of diethanolamine are added as an amide when the temperature is lowered to 100° C., and then the temperature is raised to 125° C. for amination reaction for 2.5 hours to obtain amino-containing epoxy nitrile resin; 55.0 parts of methyl isobutyl ketone are added to the amino-containing epoxy nitrile resin, and 5.2 parts of tert-butyl peroxide (2-ethylhexanoate) are added after the temperature is lowered to 60° C., and the mixture is kept at 60° C. for 30 minutes for polymerization reaction to obtain ultra-high molecular weight amino-containing epoxy nitrile resin;

[0045] (2) Preparation of modified hectorite:

[0046] a. 1 part of laponite, 0.5 parts of NiCo2O4, 0.3 parts of dodecyl dimethyl betaine, 0.2 parts of carboxymethyl cellulose and 4 parts of deionized water were placed in a ball mill and mixed uniformly, and ball milled at 300r / min for 5h to obtain a mixed slurry;

[0047] b. 1 part of bismuth nitrate and 0.16 parts of ammonium metamolybdate were dissolved in 25 mL of aqueous nitric acid solution (8 wt%), and then 1.3 parts of tartaric acid and 1.5 parts of N, N-dimethylacrylamide were added and stirred to obtain a mixed solution, and the mixed solution was slowly added to the mixed slurry of step a under heating conditions, stirred to obtain a sol, and the sol was dried at 120 ° C for 12 h, placed in a tubular furnace at 500 ° C for calcination for 2 h, and ground to obtain;

[0048] (3) 1 part of ultra-high molecular weight epoxy nitrile resin containing amino groups and 0.2 parts of modified hectorite are mixed evenly, 0.01 parts of glacial acetic acid are added, and the mixture is kept at 65° C. for 40 minutes for neutralization reaction to obtain an acidified solution, and the acidified solution is added to 890.9 parts of deionized water for emulsification to obtain the product.

[0049] Example 3

[0050] A method for preparing a functional emulsion for cathode electrophoretic coating comprises the following steps:

[0051] (1) 194.8 parts of epoxy nitrile prepolymer (86140 resin, rubber content 20%), 48.7 parts of bisphenol A and 10.2 parts of methyl isobutyl ketone are mixed and heated to 100° C., 0.1 parts of tetrabutylammonium bromide are added, and the temperature is further raised to 160° C. and reacted for 3.5 hours to obtain epoxy nitrile resin; 68.7 parts of ethylene glycol monobutyl ether are added to the epoxy nitrile resin at 160° C., 30.4 parts of diethanolamine are added as an amide when the temperature is lowered to 100° C., and then the temperature is raised to 125° C. for amination reaction for 2.5 hours to obtain amino-containing epoxy nitrile resin; 55.0 parts of methyl isobutyl ketone are added to the amino-containing epoxy nitrile resin, and 5.2 parts of tert-butyl peroxide (2-ethylhexanoate) are added after the temperature is lowered to 60° C., and the mixture is kept at 60° C. for 30 minutes for polymerization reaction to obtain ultra-high molecular weight amino-containing epoxy nitrile resin;

[0052] (2) Preparation of modified hectorite:

[0053] a. 1 part of laponite, 0.15 parts of NiCo2O4, 0.1 parts of dodecyl dimethyl betaine, 0.05 parts of carboxymethyl cellulose and 2 parts of deionized water were placed in a ball mill and mixed uniformly, and ball-milled at 400r / min for 2h to obtain a mixed slurry;

[0054] b. Dissolve 1 part of bismuth nitrate and 0.14 parts of ammonium metamolybdate in 25 mL of aqueous nitric acid solution (8 wt %), then add 1 part of tartaric acid and 1 part of N, N-dimethylacrylamide, stir to obtain a mixed solution, slowly add the mixed solution to the mixed slurry of step a under heating conditions, stir to obtain a sol, dry the sol at 120 ° C for 12 h, calcine at 500 ° C in a tubular furnace for 2 h, and grind to obtain;

[0055] (3) 1 part of ultra-high molecular weight epoxy nitrile resin containing amino groups and 0.6 parts of modified hectorite are mixed evenly, 0.02 parts of glacial acetic acid are added, and the mixture is kept at 55° C. for 40 minutes for neutralization reaction to obtain an acidified solution, and the acidified solution is added to 890.9 parts of deionized water for emulsification to obtain the product.

[0056] Comparative Example 1

[0057] The difference between Comparative Example 1 and Example 1 is that the addition of NiCo2O4 is omitted in step a, and the rest is consistent with Example 1.

[0058] Comparative Example 2

[0059] The difference between this comparative example 2 and embodiment 1 is that step b is omitted, and the rest is consistent with embodiment 1.

[0060] Comparative Example 3

[0061] The difference between this comparative example 3 and example 1 is that step (2) is omitted, the ultra-high molecular weight amino-containing epoxy nitrile resin and laponite of step (1) are uniformly mixed, 5 parts of glacial acetic acid are added, and the mixture is heated at 55° C. for 40 minutes to carry out neutralization reaction to obtain an acidified solution, and the acidified solution is added to 890.9 parts of deionized water for emulsification. The rest is consistent with example 1.

[0062] Comparative Example 4

[0063] The difference between this comparative example 4 and Example 1 is that the ultra-high molecular weight epoxy nitrile resin containing amino groups prepared in step (1) is replaced with an epoxy nitrile resin containing amino groups, and the rest is consistent with Example 1.

[0064] The effects of the functional emulsions for cathode electrophoretic coatings obtained in Examples 1-3 of the present invention and Comparative Examples 1-4 are described below.

[0065] Application Example 1

[0066] A cathode electrophoretic coating tank liquid, the preparation method is as follows:

[0067] 94 parts of cathode electrophoretic coating emulsion (Weibang coating WB851 emulsion) were added into a beaker, and the mixture was placed under a stirrer. 6 parts of the functional emulsion for cathode electrophoretic coating obtained in Example 1-3 or Comparative Example 1-4 were added under stirring, and emulsion 1-B was obtained after stirring for 20 minutes.

[0068] The Weibang coating WB851 mortar, emulsion 1-B and deionized water were uniformly mixed in a mass ratio of 1:5:6 to obtain a cathode electrophoretic coating tank liquid.

[0069] Test Example 1

[0070] After stirring and aging the above-mentioned cathode electrophoretic coating bath solutions for 48 hours, the test was carried out according to the general test method for electrophoretic coatings in HGT3334-2012, and the baking condition was 170°C (plate temperature) for 20 minutes. Among them:

[0071] (1) Appearance is tested according to the test standard of HG / T3952-2007;

[0072] (2) The film thickness is tested according to the test standard of GB / T13452.2;

[0073] (3) Pencil hardness is tested according to the test standard of GB / T6739;

[0074] (4) Impact strength is tested according to the test standard of GB / T173;

[0075] (5) Adhesion is tested according to the test standard of GB / T9286;

[0076] (6) The coating cup protrusion is tested according to the test standard of GB / T9753;

[0077] (7) Flexibility is tested according to the test standard of GB / T1731;

[0078] (8) Neutral salt spray resistance: Refer to GB / T1771-2007 Determination of neutral salt spray resistance of paints and varnishes. The qualified standard of salt spray test is that the single-side corrosion expansion at the scribe line is ≤2.0mm, and there is no blistering at the unscribe line;

[0079] (9) The substrate for the sharp edge corrosion resistance test is an A-10 metal paper cutting blade (size 10cm*1.8cm, blade width 0.2mm). The pre-treatment process of the blade electrophoresis is: degreasing-surface conditioning-phosphating. After the blade is electrophoresed, a salt spray test is carried out according to the above-mentioned GB / T1771-2007 standard. The blade is vertically upward, and both the front and back sides are exposed to the salt spray environment. After 168 hours of the salt spray test, the blade is taken out, the floating rust on the blade is cleaned, and the corrosion of the blade is immediately observed under a magnifying glass. The number of bubbles with a diameter of 0.1-0.4mm and greater than 0.4mm on the blade part (0.5cm away from both ends of the blade is not within the observation range) is counted separately. Three blades are electrophoresed in parallel for each tank sample. The number of bubbles in the sharp edge corrosion resistance in the following table is the average value of the three parallel samples;

[0080] (10) Abrasion resistance test The test was carried out according to the standard of ASTM 2357-2010.

[0081] Table 1

[0082]

[0083]

[0084] It can be seen from the test data in Table 1 that the cathode electrophoretic coating tank liquid to which the functional emulsion obtained in Examples 1 to 3 is added has good sharp edge corrosion resistance and wear resistance. Comparing Example 1 with Example 2, it can be seen that the number of blade blisters in Example 1, especially the number of blisters greater than 0.4 mm, is significantly less than that in Example 2, indicating that the higher the rubber content in the epoxy nitrile prepolymer, the better the sharp edge corrosion resistance of the synthesized functional emulsion. The possible reason is that the higher the rubber content, the higher molecular weight amino-containing epoxy nitrile resin can be formed through free radical polymerization under the action of the initiator. In addition, the cupping test results of Examples 1 to 3 are also good, indicating that the functional emulsion for cathode electrophoretic coating of the present invention can improve the tensile strength and flexibility of the electrophoretic coating, which is determined by the soft characteristics of the molecular chain segments of the epoxy nitrile prepolymer.

[0085] Compared with Examples 1-3, the cathode electrophoretic coating bath liquid to which the functional emulsion obtained in Comparative Examples 1-4 was added had varying degrees of decline in sharp edge corrosion resistance and wear resistance.

[0086] In Comparative Examples 1 and 2, the preparation process was changed when preparing the modified hectorite, and its wear resistance was greatly reduced. In Comparative Example 3, the modified hectorite was replaced with hectorite, and the wear resistance was also reduced. The above results show that the modified hectorite prepared in Example 1 can significantly improve the wear resistance of the coating.

[0087] In Comparative Example 4, the ultra-large molecular weight epoxy nitrile resin containing amino groups is replaced with an amino-containing epoxy nitrile resin. The sharp edge corrosion resistance of the cathode electrophoretic coating tank liquid finally obtained is significantly reduced. This indicates that the ultra-large molecular weight epoxy nitrile resin containing amino groups can increase the yield value of the coating in the viscous flow state, increase the film thickness at the edge, and thus improve the sharp edge corrosion resistance of the electrophoretic coating.

[0088] In summary, adding the functional emulsion prepared in Examples 1-3 of the present invention to the cathode electrophoretic coating emulsion can significantly reduce the number of blisters caused by blade corrosion, improve the ability of the electrophoretic coating to resist sharp edge corrosion, and also significantly improve the tensile strength of the electrophoretic coating.

[0089] The above are only preferred embodiments of the present invention, and are not limited to the above examples. For those skilled in the art, various changes and variations are possible under the principle of the present invention. Any modifications and improvements made should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a functional emulsion for cathode electrophoretic coating, characterized in that: The steps include: (1) adding an initiator to an amino-containing epoxy nitrile resin, and maintaining the temperature at 55-60° C. for 30-45 minutes to obtain an amino-containing epoxy nitrile resin with a super large molecular weight; (2) Preparation of modified hectorite: a. Mix laponite, NiCo2O4, surfactant, additive and water, and ball mill to obtain a mixed slurry; b. dissolving bismuth nitrate and ammonium metamolybdate in an aqueous nitric acid solution, then adding tartaric acid and N,N-dimethylacrylamide, stirring to obtain a mixed solution, slowly adding the mixed solution to the mixed slurry of step a under heating conditions, stirring to obtain a sol, drying the sol, calcining, and grinding to obtain; (3) The ultra-large molecular weight epoxy nitrile resin containing amino groups and the modified hectorite are uniformly mixed, a neutralizing agent is added to react, and then water is added for emulsification to obtain the functional emulsion for the cathode electrophoretic coating.

2. The method for preparing the functional emulsion for cathode electrophoretic coating according to claim 1, characterized in that: The mass ratio of the laponite, NiCo2O4, surfactant, additive and deionized water in step a is 1:(0.15-0.5):(0.1-0.3):(0.05-0.2):(2-4), the surfactant is dodecyl dimethyl betaine; and the additive is carboxymethyl cellulose or hydroxypropyl methyl cellulose.

3. The method for preparing the functional emulsion for cathode electrophoretic coating according to claim 1, characterized in that: The concentration of the nitric acid aqueous solution in step b is 7-9wt%; the mass ratio of bismuth nitrate, ammonium metamolybdate, tartaric acid and N,N-dimethylacrylamide is 1:(0.14-0.16):(1-1.3):(1-1.5).

4. The method for preparing the functional emulsion for cathode electrophoretic coating according to claim 1, characterized in that: In step (3), the mass ratio of the ultra-high molecular weight amino-containing epoxy nitrile resin, modified hectorite, and neutralizer is 1:(0.2-0.6):(0.01-0.02); the neutralizer is at least one of glacial acetic acid, lactic acid, formic acid, and aminosulfonic acid.

5. The method for preparing the functional emulsion for cathode electrophoretic coating according to claim 1, characterized in that: The initiator in step (1) is any one of benzoyl peroxide, tert-butyl benzoyl peroxide, methyl ethyl ketone peroxide or tert-butyl peroxide (2-ethylhexanoate).

6. The method for preparing the functional emulsion for cathode electrophoretic coating according to claim 1, characterized in that: The preparation method of the amino-containing epoxy butyronitrile resin in step (1) comprises the following steps: The epoxy nitrile prepolymer, bisphenol A and methyl isobutyl ketone are mixed and heated to 100°C, a catalyst is added, and the temperature is further raised to 155-160°C for reaction for 3-4 hours to obtain epoxy nitrile resin; methyl isobutyl ketone is added to the epoxy nitrile resin, and after cooling, an organic amine is added to carry out an amination reaction to obtain an amino-containing epoxy nitrile resin.

7. The method for preparing the functional emulsion for cathode electrophoretic coating according to claim 6, characterized in that: The epoxy nitrile prepolymer comprises a bisphenol A glycidyl ether with a rubber content of 20-60% and an adduct of nitrile rubber; the catalyst is any one of dimethyl monoethanolamine, dimethyl benzylamine and tetrabutyl ammonium bromide; and the organic amine is any one of diethanolamine and methyl monoethanolamine.

8. The method for preparing the functional emulsion for cathode electrophoretic coating according to claim 6, characterized in that: The mass ratio of the epoxy resin, bisphenol A and organic amine is (75-85):(15-25):(9-15); the amount of the catalyst used is 0.03%-0.05% of the total mass of the epoxy nitrile resin and bisphenol A; the temperature of the amination reaction is 120-125° C., and the time is 2-2.5 hours.

9. A functional emulsion for cathode electrophoretic coating prepared according to the preparation method according to any one of claims 1 to 8.

10. Use of the functional emulsion for cathode electrophoretic coating according to claim 9 in the preparation of electrophoretic coating.

Images