Electrophoretic paint on silane pretreatment

Abstract

The application discloses an electrophoretic paint on silane pretreatment, which comprises the following components in percentage by weight: cationic electrodeposition coating emulsion 25%-35%, silica sol 1.5%-2.5%, color paste 5%-7%, and deionized water 55%-65%; wherein the cationic electrodeposition coating emulsion comprises a first emulsion and a second emulsion; the first emulsion comprises amine modified epoxy resin and blocked isocyanate curing agent; and the second emulsion comprises organic silicon / fatty acid modified epoxy flexible resin. The electrophoretic paint prepared by the application has good electrodeposition coating adaptability and excellent corrosion resistance on the matched environment-friendly film pretreatment, especially the silane pretreatment, and the corrosion resistance effect is very close to or reaches the corrosion resistance effect of phosphating pretreatment, so that the application has a wide application prospect in the industry.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrophoretic paint, and particularly relates to an electrophoretic paint on silane pretreatment. BACKGROUND

[0002] Cationic electrodeposition paint is widely used in the industries of automobile, tricycle, machinery and hardware because of its excellent coating workability, the ability to coat each part of metal workpiece with complex shape and structure uniformly, and the good physical and chemical properties of the formed coating film.

[0003] In recent years, with the increasing environmental protection requirements and the large-scale use of aluminum and aluminum alloy, the traditional zinc-based phosphating pretreatment is limited to use, and the use of environmentally friendly film pretreatment process is increasing. However, the pretreatment film of the environmentally friendly film pretreatment is relatively thin, generally only about 0.5-1.2 microns, while the film thickness of the traditional zinc-based phosphating pretreatment can reach about 3-4 microns. This leads to the fact that the same paint is significantly better in corrosion resistance when matched with zinc-based phosphating pretreatment than when matched with film pretreatment process, especially when matched with silane pretreatment process. Because the silane pretreatment film contains a large amount of Si-O-Si structure, the wettability requirement of the paint on the pretreatment film is very high, and the electrophoretic paint needs to have good electrodeposition coating adaptability to ensure that the paint film has good appearance and performance. SUMMARY

[0004] The purpose of the present application is to provide an electrophoretic paint on silane pretreatment, which solves one or more of the above-mentioned problems in the prior art.

[0005] The present application provides an electrophoretic paint on silane pretreatment, which comprises the following components by weight percentage:

[0006]

[0007]

[0008] The cationic electrodeposition paint emulsion comprises a first emulsion and a second emulsion, the first emulsion comprises amine-modified epoxy resin and blocked isocyanate curing agent, and the second emulsion comprises silicone / fatty acid-modified epoxy flexible resin.

[0009] In some embodiments, the electrophoretic paint on silane pretreatment comprises the following components by weight percentage:

[0010]

[0011] In some embodiments, the first emulsion comprises the following components by weight percentage:

[0012]

[0013] In certain embodiments, the first emulsion comprises the following components by weight percentage:

[0014]

[0015]

[0016] In certain embodiments, the second emulsion comprises the following components by weight percentage:

[0017]

[0018] In certain embodiments, the second emulsion comprises the following components by weight percentage:

[0019]

[0020] In certain embodiments, the mass concentration of lactic acid is 20%, the mass concentration of sulfamic acid is 20%, and the mass concentration of acetic acid is 20%.

[0021] In certain embodiments, the first emulsion is prepared by the following method:

[0022] In a reactor equipped with a thermometer and a stirrer, add the amine-modified epoxy resin and the blocked isocyanate curing agent, and then add lactic acid and sulfamic acid under stirring. Neutralize and ionize the resin at a temperature of 40-50°C for 1 h, and finally add deionized water in batches and emulsify for 30 min to obtain the first emulsion.

[0023] In certain embodiments, the second emulsion is prepared by the following method:

[0024] In a reactor equipped with a thermometer and a stirrer, add the silicone / fatty acid-modified epoxy flexible resin, and then add acetic acid under stirring. Neutralize and ionize the resin at a temperature of 40-50°C for 1 h, and finally add deionized water in batches and emulsify for 30 min to obtain the second emulsion.

[0025] In certain embodiments, the amine-modified epoxy resin is prepared by the following method:

[0026] Under the action of a catalyst, perform ring-opening chain extension reaction of the base epoxy resin and the chain extender at a reaction temperature of 130-190°C. When the epoxy equivalent weight reaches 900-1100 g / mol, cool to 90-100°C, and then add an organic amine compound. Perform amination and chain extension reaction at a temperature of 110-120°C to obtain the amine-modified epoxy resin.

[0027] In certain embodiments, the base epoxy resin is a bisphenol A type epoxy resin having an epoxy equivalent weight between 180-540 g / mol, the base epoxy resin is one or more mixed epoxy equivalent weight resins;

[0028] The chain extender is a monophenol, a polyphenol, a polyether polyol, a polyester polyol, and an amine having one or two active hydrogens, the chain extender has a molecular weight between 50-2000; the chain extender is one or more mixed bisphenol A, monophenol, polyether polyol, polyester polyol, bisphenol A type polyether polyol.

[0029] In certain embodiments, the silicone / fatty acid modified epoxy flexible resin is prepared by the following method:

[0030] The ring opening chain extension reaction is carried out by the epoxy reactive diluent, the chain extender, and the fatty acid under the action of a catalyst at a temperature of 130-190 °C, after reaching the theoretical epoxy equivalent weight, the temperature is lowered to 90-100 °C, the organic amine and the silane coupling agent are added, and the amination and chain extension reaction is carried out at a temperature of 120-130 °C, thereby obtaining the silicone / fatty acid modified epoxy flexible resin.

[0031] In certain embodiments, the silicone / fatty acid modified epoxy flexible resin is prepared by the following method:

[0032] The epoxy reactive diluent and the chain extender are mixed, the reaction system is warmed to 100 °C under stirring, the catalyst is added, after the addition is complete, the temperature is first raised to 170 °C, and the reaction is carried out at 170 °C for 35 min, then the epoxy equivalent weight is measured, when the epoxy equivalent weight of the system reaches 710-755, the fatty acid is added, the temperature is lowered to 160 °C, and the reaction is carried out for 1.5 h, when the epoxy equivalent weight of the system reaches 2600-2800 and the acid value is 0-1.0, the temperature is lowered; the temperature is lowered to 90-95 °C, the silicone coupling agent is added at once, the temperature is raised to 95-100 °C, and the reaction is carried out for 40 min, then the organic amine is added, the temperature is raised to 120-130 °C, and the reaction is carried out for 3 h; after the reaction is complete, the silicone / fatty acid modified epoxy flexible resin is obtained, and the solid content of the final resin is 99%.

[0033] In certain embodiments, the epoxy reactive diluent is any one or a mixture of two of aliphatic glycidyl ether type epoxy, aliphatic glycidyl ester type epoxy, and alicyclic epoxy containing two epoxy groups in the molecular structure, including but not limited to any one or a mixture of two of ethylene glycol diglycidyl ether, C3-C14 alkyl glycidyl ether, polypropylene glycol glycidyl ether, 1,4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, and versatic acid glycidyl ether;

[0034] The fatty acid is a long carbon chain saturated or unsaturated fatty acid containing one or two carboxyl groups, including but not limited to any one or mixture of two of monobasic acid, dimer acid, coconut oil acid, linoleic acid, ricinoleic acid, C3-C25 oleic acid;

[0035] The silane coupling agent is an organic silicon molecule structure containing amino or epoxy groups, including but not limited to any one or mixture of two of γ―(2,3-epoxypropoxy) propyl trimethoxysilane, 3-aminopropyl triethoxysilane;

[0036] The organic amine includes but is not limited to any one or mixture of two of monoethanolamine, diethanolamine, N-methyl ethanolamine, 1,3-dimethylpropylamine, ketimine organic amine, and the ketimine organic amine includes methyl isobutyl ketimine or ketimine modified polyamide.

[0037] In some embodiments, the silica sol used is a dispersion of nano-sized silica particles in water or solvent. The particle size of the silica sol is less than 10 nm.

[0038] In some embodiments, the particle size of the silica sol is 1-5 nm.

[0039] In some embodiments, the color paste is prepared by the following method:

[0040] The pigment dispersion resin, titanium oxide, kaolin, carbon black, dioctyl tin oxide, bismuth hydroxide and deionized water are mixed uniformly, then sand-milled for 15 h by a ball mill to obtain a color paste with a solid content of 56%.

[0041] Compared with the prior art, the electrophoretic paint of the present application has good electrodeposition coating adaptability and excellent corrosion resistance before the treatment of the matching environmentally friendly film, especially in the silane pretreatment. DETAILED DESCRIPTION

[0042] The technical solutions of the present application will be described in detail below in combination with various embodiments.

[0043] Example 1 Preparation of amine modified epoxy resin

[0044] Component Amount (g) Base Epoxy Resin Bisphenol A 188 Phenol 68.4 Dimethylbenzylamine 15 Methyl isobutyl ketone 0.3 N-methylethanolamine 50 Ketimine 18.5 Ethylene glycol butyl ether 30.1 Total 15 Component Amount (g) 385.3

[0045] wherein,

[0046] The base epoxy resin is a bisphenol A type epoxy resin manufactured by DOW Company, EEW = 186-190;

[0047] Phenol is used as a molecular weight regulator;

[0048] Ketimine is prepared by reaction of diethylene triamine and methyl isobutyl ketone, the final product has solid content of 73% and amine value of 450-480 mgKOH / g.

[0049] In a reaction bottle equipped with a thermometer, a stirrer and a reflux condenser, the formula amount of base epoxy resin, bisphenol A, phenol and methyl isobutyl ketone are sequentially added. After the addition is completed, the reaction system is warmed to 100°C under stirring, and then dimethyl benzyl amine catalyst is added. After the addition is completed, the temperature is first increased to 140°C, and then the reaction is carried out for 60 min. The epoxy equivalent weight is measured. When the epoxy equivalent weight of the system reaches 900-1100, the temperature is decreased to 90-100°C, and N-methyl ethanol amine and ketimine are added at one time. The temperature is increased to 110-120°C, and then the reaction is carried out for 2 h. After the reaction is completed, ethylene glycol butyl ether is added to obtain a modified epoxy resin with a solid content of 84%.

[0050] Preparation of blocked isocyanate curing agent in Example 2

[0051]

[0052]

[0053] In a reaction bottle equipped with a thermometer, a stirrer and a reflux condenser, the formula amount of base epoxy resin, bisphenol A, phenol and methyl isobutyl ketone are sequentially added. After the addition is completed, the reaction system is warmed to 100°C under stirring, and then dimethyl benzyl amine catalyst is added. After the addition is completed, the temperature is first increased to 140°C, and then the reaction is carried out for 60 min. The epoxy equivalent weight is measured. When the epoxy equivalent weight of the system reaches 900-1100, the temperature is decreased to 90-100°C, and N-methyl ethanol amine and ketimine are added at one time. The temperature is increased to 110-120°C, and then the reaction is carried out for 2 h. After the reaction is completed, ethylene glycol butyl ether is added to obtain a modified epoxy resin with a solid content of 84%.

[0054] Preparation of silicone / fatty acid modified epoxy flexible resin in Example 3

[0055] Epoxy reactive diluent 1 Bisphenol A Dimer acid (acid value = 190-200) 1530 Dimethylimidazole 300 Silicone coupling agent 1 470 N-methylethanolamine 0.8 Ketimine 3 26.8 Total 76 Component Amount (g) 100 Epoxy reactive diluent 1 2503.6

[0056] 1-Epoxy active diluent: polypropylene glycol diglycidyl ether manufactured by DOW Company, EEW = 290-300, total chlorine content < 2000 ppm;

[0057] 2-Silicone coupling agent: amino functional silane KH550;

[0058] 3-Ketimine: prepared by reaction of diethylene triamine and methyl isobutyl ketone, the final product has solid content of 70% and amine value = 450-480 mgKOH / g.

[0059] In a reaction bottle equipped with a thermometer, a stirrer and a reflux condenser, the formula amount of epoxy reactive diluent and bisphenol A were added in sequence. After the addition was completed, the reaction system was heated to 100°C under stirring. Then dimethyl imidazole catalyst was added. After the addition was completed, the temperature was first increased to 170°C for 35 minutes of reaction. The epoxy equivalent weight was measured. When the epoxy equivalent weight of the system reached 720-755, dimeric acid was added. The temperature was decreased to 160°C for 1.5 hours of reaction. When the epoxy equivalent weight of the system reached 2600-2800 and the acid value was 0-1.0, the temperature was decreased. When the temperature decreased to 90-95°C, silicone coupling agent was added at one time. After 40 minutes of reaction at 95-100°C, N-methyl ethanolamine and ketimine were added. The temperature was increased to 120-130°C for 3 hours of reaction. Finally, the silicone / fatty acid modified epoxy flexible resin with a solid content of 99% was obtained.

[0060] Preparation of silicone / fatty acid modified epoxy flexible resin of Example 4

[0061] Bisphenol A Coconut oil acid (molecular weight 343) Dimethylimidazole 1522.3 N-methylethanolamine 299.8 Polyetheramine D-400 467.8 Silicone coupling agent 2 0.8 Total 18.32 Component Amount (g) 200 Example 1 amine modified epoxy resin 30 Example 2 blocked isocyanate curing agent 2539.02

[0062] 1-Epoxy reactive diluent: polypropylene glycol diglycidyl ether manufactured by DOW company, EEW=290-300, total chlorine content <2000ppm;

[0063] 2-Silicone coupling agent: epoxy functional silane KH560;

[0064] D-400: HUNTSMAN D400 polyether amine.

[0065] In a reaction bottle equipped with a thermometer, a stirrer and a reflux condenser, the formula amount of epoxy reactive diluent and bisphenol A were added in sequence. After the addition was completed, the reaction system was heated to 100°C under stirring. Then dimethyl imidazole catalyst was added. After the addition was completed, the temperature was first increased to 170°C for 35 minutes of reaction. The epoxy equivalent weight was measured. When the epoxy equivalent weight of the system reached 710-750, dimeric acid was added. The temperature was decreased to 160°C for 1.5 hours of reaction. When the epoxy equivalent weight of the system reached 2600-2800 and the acid value was 0-1.0, the temperature was decreased. When the temperature decreased to 90-95°C, silicone coupling agent was added at one time. After 40 minutes of reaction at 95-100°C, N-methyl ethanolamine and polyether amine D-400 were added. The temperature was increased to 120-130°C for 3 hours of reaction. Finally, the silicone / fatty acid modified epoxy flexible resin with a solid content of 99% was obtained.

[0066] Preparation of cationic electrodeposition coating emulsion of Example 5

[0067] First emulsion:

[0068] 20% lactic acid 20% sulfamic acid Deionized water 370.76 Deionized water 200 Total 8 Component Amount (g) 20 Example 1 amine modified epoxy resin 549.79 Example 2 blocked isocyanate curing agent 518 20% lactic acid 1666.55

[0069] Into a reactor equipped with a thermometer and a stirrer, add the silicone / fatty acid modified epoxy flexible resin, and then add acetic acid under stirring. Disperse for 1 h at 40-50°C to neutralize and ionize the resin. Finally, add the required deionized water, and emulsify for 30 min to obtain an emulsion with a solid content of 33%.

[0070] Second emulsion:

[0071]

[0072]

[0073] Into a reactor equipped with a thermometer and a stirrer, add the silicone / fatty acid modified epoxy flexible resin, and then add acetic acid under stirring. Disperse for 1 h at 40-50°C to neutralize and ionize the resin. Finally, add the required deionized water, and emulsify for 30 min to obtain an emulsion with a solid content of 33%.

[0074] Preparation of the cationic electrodeposition coating emulsion of Example 6

[0075] First emulsion:

[0076] 20% sulfamic acid Deionized water Deionized water 370.76 Total 200 ​ 8 ​ 20 ​ 549.79 ​ 518 ​ 1666.55

[0077] Into a reactor equipped with a thermometer and a stirrer, add the silicone / fatty acid modified epoxy flexible resin, and then add acetic acid under stirring. Disperse for 1 h at 40-50°C to neutralize and ionize the resin. Finally, add the required deionized water, and emulsify for 30 min to obtain an emulsion with a solid content of 33%.

[0078] Second emulsion:

[0079]

[0080]

[0081] Into a reactor equipped with a thermometer and a stirrer, add the silicone / fatty acid modified epoxy flexible resin, and then add acetic acid under stirring. Disperse for 1 h at 40-50°C to neutralize and ionize the resin. Finally, add the required deionized water, and emulsify for 30 min to obtain an emulsion with a solid content of 33%.

[0082] Preparation of the color paste of Example 7

[0083] Add 830 g of pigment dispersing resin, 1450 g of titanium oxide, 700 g of kaolin, 30 g of carbon black, 100 g of dioctyl tin oxide, 100 g of bismuth hydroxide, and 200 g of deionized water, mix well, and then sand mill for 15 h to obtain a color paste with a solid content of 56%.

[0084] Specifically, the components of the electrophoretic coating are as follows:

[0085]

[0086]

[0087] 1. The used silica sol solid content is 15%.

[0088] Performance test

[0089] Manufacture of test plate:

[0090] Metal substrate electrodeposition adaptability

[0091] After the aluminum plate (0.8mm*150mm*70mm), magnesium-aluminum alloy plate (0.8mm*150mm*70mm) are pretreated by degreasing and then silane pretreated as the pieces to be coated, they are coated with the electrophoretic paint obtained in the above Comparative Examples 1-5, and the paint film after coating is baked at 170°C for 20 min. The number of pores of the test piece after drying is calculated. All the plates are not subjected to surface chemical treatment so as to detect the adaptability to the plates.

[0092] *: no pores,

[0093] *: one small pore, but no substrate exposed,

[0094] *: 2-10 pores

[0095] *: more than 10 pores.

[0096] Corrosion resistance 1

[0097] After the cold-rolled plate (0.8mm*150mm*70mm) is pretreated by degreasing and then silane pretreated as the piece to be coated, it is coated with the electrophoretic paint obtained in Comparative Examples 1-5. The paint film after coating is baked at 170°C for 20 min, and the film thickness is controlled at 20-23 microns. According to the national standard NSS, the salt spray test is carried out for 800h, and the number of blisters and the corrosion width of the cut part are evaluated.

[0098] *: no blister from the cut part side not more than 2.0mm, and no blister near the cut part,

[0099] *: one blister from the cut part side not more than 2.0mm, and 1-2 blisters near the cut part,

[0100] *: one blister from the cut part side not more than 2.0mm, and 1-2 blisters near the cut part,

[0101] *: one blister from the cut part side not more than 2.0mm, and 1-2 blisters near the cut part,

[0102] Corrosion resistance 2

[0103] The cold-rolled plate (0.8mm*150mm*70mm) was pretreated by degreasing, then was subjected to zinc-based phosphating pretreatment, and was coated with the electrophoretic paint obtained in Comparative Examples 1-5 as a coating object. After coating, the paint film was baked at 170℃ for 20min, the film thickness was controlled at 20-23 microns, and the salt spray test was performed according to the national standard NSS for 800h to evaluate the blister number and the corrosion width of the scribed part.

[0104] *: no more than 2.0mm from one side of the scribed part, and no blister near the scribed part,

[0105] *: no more than 2.0mm from one side of the scribed part, and 1-2 blisters near the scribed part,

[0106] *: more than 2.0mm but less than 3.0mm from one side of the scribed part, and 1-2 blisters near the scribed part,

[0107] *: more than 2.0mm but less than 3.0mm from one side of the scribed part, and 2-5 blisters near the scribed part.

[0108] The above test results are shown in the following table:

[0109]

[0110]

[0111] As can be seen from the above table, the electrophoretic paint prepared from the first emulsion and the second emulsion has more excellent performance than the electrophoretic paint prepared from the first emulsion alone, mainly because the surface energy of the silane pretreated surface is relatively low, and the first emulsion has poor wetting effect on the surface. After adding the second emulsion, because the oleic acid component contains a long carbon chain, it is beneficial to wetting on the silane pretreated surface; in addition, the silicon hydroxyl and carboxyl groups in the second emulsion can increase the chemical bonding force with the silane pretreatment. At the same time, the particle size of the silica sol also has a certain influence on the prepared electrophoretic paint. The silica sol with small particle size has better compatibility with the emulsion, can be quickly deposited with the emulsion on the material surface by electrophoresis, and has a larger specific surface area, which is easy to form more chemical forces between the silane pretreated surface, and the formed paint film is more dense.

[0112] In summary: the electrophoretic paint prepared by the present application has good electrodeposition coating adaptability and excellent corrosion resistance on the matching environment-friendly thin film pretreatment, especially the silane pretreatment, and the corrosion resistance effect is very close to or reaches the corrosion resistance of the phosphating pretreatment, which has a wide application prospect in industry.

[0113] The reason for good corrosion resistance is as follows: on the one hand, the wetting performance of the coating on the film pretreatment (such as: silane system pretreatment) is improved, the adhesion between the coating and the substrate is improved, and the electrophoretic film forming is more compact. On the other hand, the Si-OH groups on the silica sol can react with the Si-OH in the film pretreatment (such as: silane system pretreatment), increasing the force between the coating and the pretreatment coating, thereby repairing the defects of the film pretreatment film.

[0114] Those skilled in the art can clearly make various modifications to the above embodiments without departing from the overall spirit and concept of the present application. All fall within the scope of the present application. The protection scheme of the present application is subject to the claims attached to the present application.

Claims

1. An electrophoretic coating over a silane pretreatment, characterized in that, The components include the following weight percentages: Cationic electrodeposition coating emulsion 25%-35%, Silica sol 1.5%-2.5%, Color paste 5%-7%, Deionized water 55%-65%; The cationic electrodeposition coating emulsion includes a first emulsion and a second emulsion, the first emulsion includes an amine-modified epoxy resin and a blocked isocyanate curing agent, and the second emulsion includes an organic silicon / fatty acid-modified epoxy flexible resin. The first emulsion is prepared by the following method: In a reactor equipped with a thermometer and a stirrer, add the amine-modified epoxy resin and the blocked isocyanate curing agent, add lactic acid and aminosulfonic acid under stirring, neutralize and ionize the resin at a temperature of 40-50°C for 1h, and finally add deionized water in batches, emulsify for 30min, to obtain the first emulsion. The second emulsion is prepared by the following method: In a reactor equipped with a thermometer and a stirrer, add the organic silicon / fatty acid-modified epoxy flexible resin, add acetic acid under stirring, neutralize and ionize the resin at a temperature of 40-50°C for 1h, and finally add deionized water in batches, emulsify for 30min, to obtain the second emulsion. The particle size of the silica sol is less than 10nm.

2. An electrophoretic paint on a silane pretreatment according to claim 1, characterized in that, The first emulsion includes the following weight percentages of components: Amine-modified epoxy resin 20%-25%, Blocked isocyanate curing agent 10%-15%, Lactic acid 0.2%-0.5%, Aminosulfonic acid 1%-1.5%, First batch of deionized water 30%-35%, Second batch of deionized water 30%-32%.

3. The electrophoretic paint on silane pretreatment according to claim 2, characterized in that, The second emulsion includes the following weight percentages of components: Organic silicon / fatty acid-modified epoxy flexible resin 30%-35%, Acetic acid 2.5%-3.2%, First batch of deionized water 45%-50%, Second batch of deionized water 10%-20%.

4. The electrophoretic paint on silane pretreatment according to claim 2, characterized in that, The amine-modified epoxy resin is prepared by the following method: Under the action of a catalyst, the base epoxy resin and the chain extender are subjected to ring-opening chain extension reaction at a reaction temperature of 130-190°C, when the epoxy equivalent reaches 900-1100 g / mol, the temperature is lowered to 90-100°C, and an organic amine compound is added, and amine and chain extension reactions are carried out at 110-120°C to obtain the amine-modified epoxy resin.

5. The electrophoretic paint on a silane pretreatment according to claim 4, characterized in that, The base epoxy resin is a bisphenol A type epoxy resin with an epoxy equivalent of 180-540 g / mol, and the base epoxy resin is one or more mixed resins with different epoxy equivalents; The chain extender is a monophenol, a polyphenol, a polyether polyol, a polyester polyol, or an amine with one or two active hydrogens, and the molecular weight of the chain extender is between 50 and 2000.

6. The electrophoretic paint over silane pretreatment of claim 3, wherein, The organic silicon / fatty acid-modified epoxy flexible resin is prepared by the following method: Under the action of a catalyst, the epoxy active diluent, the chain extender and the fatty acid are subjected to ring-opening chain extension reaction at a temperature of 130-190°C, when the theoretical epoxy equivalent is reached, the temperature is lowered to 90-100°C, and an organic amine and a silane coupling agent are added, and amine and chain extension reactions are carried out at 120-130°C to obtain the organic silicon / fatty acid-modified epoxy flexible resin.

7. The electrophoretic paint on a silane pretreatment according to claim 6, characterized in that, The epoxy reactive diluent is any one or mixture of two of aliphatic glycidyl ether epoxy, aliphatic glycidyl ester epoxy, alicyclic epoxy containing two epoxy groups in the molecular structure; The fatty acid is any one or mixture of two of long carbon chain saturated or unsaturated fatty acid containing one or two carboxyl groups; The silane coupling agent is a coupling agent containing amino group or epoxy group; The organic amine includes but is not limited to any one or mixture of two of monoethanolamine, diethanolamine, N-methylethanolamine, 1,3-dimethylpropylamine, ketimine organic amine, the ketimine organic amine including methyl isobutyl ketimine or ketimine modified polyamide.

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