Preparation method and application of impact-resistant cathode electrophoretic paint

Abstract

The invention belongs to the technical field of coatings, and discloses a preparation method and application of an impact-resistant cathode electrophoretic coating. The preparation method comprises the following steps: adding epoxy resin into a mixed solvent of ethyl acetate and benzyl glycidyl ether, then adding 2, 2 ', 6, 6'-tetrahydroxybiphenyl and dihydroxyl-terminated polydimethylsiloxane, stirring and mixing, adding an emulsifier, and dispersing to obtain a film-forming emulsion; and mixing the filler, the curing agent, the catalyst, the water and the auxiliary agent, and then adding the mixture into the film-forming emulsion for mixing to prepare the cathode electrophoretic coating. According to the invention, a ring-opening reaction during curing of epoxy resin, polyhydroxy and aromatic ring structures of 2, 2 ', 6, 6'-tetrahydroxybiphenyl and dihydroxy-terminated polydimethylsiloxane are utilized to be cured with the curing agent, so that a stable spatial three-dimensional network structure with good elasticity can be formed, and the filler can be uniformly dispersed in the spatial three-dimensional network structure, so that the stability of the epoxy resin is improved, and the service life of the epoxy resin is prolonged. And finally, the coating with good impact resistance is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings, and particularly relates to a preparation method and application of an impact-resistant cathode electrophoretic coating. Background Art

[0002] The impact resistance of the coating affects the application of the coating. If the impact resistance of the coating is poor, the coating is prone to damage, peeling or cracking, which reduces the protective effect of the coating on the substrate and further reduces the service life of the substrate. Therefore, impact resistance is an important performance indicator of the coating.

[0003] Cathodic electrophoretic coatings are widely used, and impact resistance is also an important performance indicator of cathodic electrophoretic coatings. However, the impact strength that existing cathodic electrophoretic coatings can generally withstand is about 50kg / cm, and it is difficult to exceed 62kg / cm. This limits the application scope of cathodic coatings to a certain extent.

[0004] Therefore, there is an urgent need to provide a cathode electrophoretic coating with better impact resistance. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a method for preparing an impact-resistant cathode electrophoretic coating and its application. The impact strength of the cathode electrophoretic coating of the present invention exceeds 62kg / cm, and can even reach 68kg / cm, which is very conducive to further expanding the application scope of the cathode electrophoretic coating.

[0006] A first aspect of the present invention provides a method for preparing an impact-resistant cathodic electrophoretic coating.

[0007] Specifically, a method for preparing an impact-resistant cathodic electrophoretic coating comprises the following steps:

[0008] (1) adding epoxy resin to a mixed solvent of ethyl acetate and benzyl glycidyl ether, then adding 2,2',6,6'-tetrahydroxybiphenyl and dihydroxy-terminated polydimethylsiloxane, stirring and mixing, and then adding an emulsifier, dispersing, and obtaining a film-forming emulsion;

[0009] (2) The filler, curing agent, catalyst, water and auxiliary agent are mixed, and then added into the film-forming emulsion, and mixed to obtain the cathode electrophoretic coating.

[0010] Preferably, in step (1), the epoxy resin comprises bisphenol A epoxy resin and / or bisphenol F epoxy resin. Further preferably, the epoxy resin is composed of bisphenol A epoxy resin and bisphenol F epoxy resin in a mass ratio of 1:(1-3).

[0011] Preferably, in step (1), the mass ratio of the epoxy resin, 2,2',6,6'-tetrahydroxybiphenyl, dihydroxy-terminated polydimethylsiloxane and emulsifier is 50:(5-20):(5-20):(2-10), and more preferably 50:(8-15):(5-10):(4-10).

[0012] Preferably, in step (1), the emulsifier is at least one of polysorbate 80, sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, and polyoxyethylene ether. More preferably, the emulsifier is polysorbate 80 and at least one of sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, and polyoxyethylene ether. The emulsifier composed of polysorbate 80 and at least one of sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, and polyoxyethylene ether can make the components dispersed more evenly.

[0013] Preferably, in step (2), the curing agent comprises isocyanate and diethylenetriamine.

[0014] Preferably, the isocyanate is selected from at least one of toluene diisocyanate, diphenylmethane diisocyanate and hexamethylene diisocyanate.

[0015] Preferably, in the curing agent, the mass ratio of isocyanate to diethylenetriamine is 1:(1-4), more preferably 1:(1-2).

[0016] Preferably, in step (2), the weight ratio of the film-forming emulsion, filler, curing agent, catalyst, water and additive is 60:(5-35):(10-22):(1-5):(25-80):(0.5-8); further preferably, the weight ratio of the film-forming emulsion, filler, curing agent, catalyst, water and additive is 60:(10-30):(12-20):(1-5):(35-70):(0.5-5).

[0017] Preferably, the catalyst is selected from at least one of dibutyltin dilaurate and dibutyltin dioctoate.

[0018] Preferably, the auxiliary agent includes at least one of a defoaming agent and a wetting agent.

[0019] Preferably, the defoaming agent is dimethyl polysiloxane.

[0020] Preferably, the wetting agent is propylene glycol block polyether or phosphate ester.

[0021] Preferably, the filler is illite and / or potassium feldspar.

[0022] Preferably, a method for preparing an impact-resistant cathodic electrophoretic coating comprises the following steps:

[0023] (1) adding an epoxy resin to a mixed solvent of ethyl acetate and benzyl glycidyl ether, then adding 2,2',6,6'-tetrahydroxybiphenyl and dihydroxy-terminated polydimethylsiloxane, stirring and mixing, and then adding an emulsifier, dispersing, and obtaining a film-forming emulsion, wherein the mass ratio of the epoxy resin, 2,2',6,6'-tetrahydroxybiphenyl, dihydroxy-terminated polydimethylsiloxane, and emulsifier is 50:(5-20):(5-20):(2-10);

[0024] (2) Mixing filler, curing agent, catalyst, water and auxiliary agent, and then adding them into film-forming emulsion and mixing, thereby obtaining the cathode electrophoretic coating; the weight ratio of film-forming emulsion, filler, curing agent, catalyst, water and auxiliary agent is 60:(5-35):(10-22):(1-5):(25-80):(0.5-8).

[0025] Preferably, when adding the auxiliary agent, phloroglucinol is also added. The addition of phloroglucinol helps the cathode electrophoretic coating to further form a more compact three-dimensional network.

[0026] More preferably, the mass ratio of phloroglucinol to the film-forming emulsion is 0.1-1:20, and more preferably 0.2-0.5:20.

[0027] A second aspect of the present invention provides an impact-resistant cathodic electrophoretic coating.

[0028] Specifically, an impact-resistant cathodic electrophoretic coating is prepared by the above preparation method.

[0029] A third aspect of the present invention provides a use of an impact-resistant cathodic electrophoretic coating.

[0030] Application of the impact-resistant cathodic electrophoretic coating in the fields of automobiles, hardware and building materials, or household appliances.

[0031] Preferably, the cathode electrophoretic coating is heated to 60-90°C and cured for 20-50 minutes, then further heated to 120-160°C and cured for 20-60 minutes. The present invention adopts staged heating and curing, so that the cathode electrophoretic coating forms a more stable and dense coating on the substrate surface.

[0032] Preferably, the substrate is metal or plastic.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] (1) The cathode electrophoretic coating of the present invention uses epoxy resin, 2,2',6,6'-tetrahydroxybiphenyl, and dihydroxy-terminated polydimethylsiloxane as main film-forming substances, and utilizes the ring-opening reaction during epoxy resin curing, as well as the polyhydroxyl and aromatic ring structures of 2,2',6,6'-tetrahydroxybiphenyl and dihydroxy-terminated polydimethylsiloxane. After curing with a curing agent, a stable and elastic three-dimensional network structure can be formed, and fillers can be evenly dispersed in the three-dimensional network structure, thereby finally obtaining a coating with good impact resistance.

[0035] (2) In the process of preparing the cathode electrophoretic coating, the present invention further adds phloroglucinol, which is beneficial to further improve the toughness of the three-dimensional network structure of the coating space, thereby further improving the impact resistance and glossiness. DETAILED DESCRIPTION

[0036] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be noted that the following embodiments do not limit the protection scope of the present invention.

[0037] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0038] Example 1

[0039] A method for preparing an impact-resistant cathode electrophoretic coating comprises the following steps:

[0040] (1) adding epoxy resin (bisphenol A epoxy resin) to a mixed solvent of ethyl acetate and benzyl glycidyl ether (the volume ratio of ethyl acetate to benzyl glycidyl ether is 2:1) (the volume ratio of epoxy resin to the mixed solvent is 1:3), then adding 2,2',6,6'-tetrahydroxybiphenyl and dihydroxy-terminated polydimethylsiloxane, stirring and mixing, then adding an emulsifier (the emulsifier is composed of polysorbate 80 and sodium dodecyl sulfate in a mass ratio of 1:2), dispersing, the stirring speed during dispersion is 1000 rpm, the dispersion time is 15 minutes, and a film-forming emulsion is obtained, wherein the mass ratio of epoxy resin, 2,2',6,6'-tetrahydroxybiphenyl, dihydroxy-terminated polydimethylsiloxane, and emulsifier is 50:15:10:5;

[0041] (2) a filler (illite), a curing agent (the curing agent is composed of toluene diisocyanate and diethylenetriamine in a mass ratio of 1:1.2), a catalyst (dibutyltin dilaurate), water, and an auxiliary agent (the auxiliary agent is composed of dimethylpolysiloxane and phosphate in a mass ratio of 1:1) are mixed, the stirring speed during mixing is 800 rpm, and the dispersion time is 10 minutes, and then added to the film-forming emulsion, mixed (the stirring speed during mixing is 1200 rpm, and the dispersion time is 8 minutes), to prepare a cathode electrophoretic coating;

[0042] The weight ratio of the film-forming emulsion, filler, curing agent, catalyst, water and additive is 60:15:12:50:0.8.

[0043] Example 2

[0044] A method for preparing an impact-resistant cathode electrophoretic coating comprises the following steps:

[0045] (1) adding an epoxy resin (the epoxy resin is composed of bisphenol A epoxy resin and bisphenol F epoxy resin in a mass ratio of 1:1.2) to a mixed solvent of ethyl acetate and benzyl glycidyl ether (the volume ratio of ethyl acetate to benzyl glycidyl ether is 2:0.8) (the volume ratio of epoxy resin to the mixed solvent is 1:4), then adding 2,2',6,6'-tetrahydroxybiphenyl and dihydroxy-terminated polydimethylsiloxane and stirring and mixing, then adding an emulsifier (the emulsifier is composed of polyoxyethylene ether and sodium dodecyl sulfate in a mass ratio of 1:2) and dispersing, the stirring speed during dispersion is 1100 rpm, the dispersion time is 15 minutes, and a film-forming emulsion is obtained, wherein the mass ratio of epoxy resin, 2,2',6,6'-tetrahydroxybiphenyl, dihydroxy-terminated polydimethylsiloxane and emulsifier is 50:12:8:5;

[0046] (2) a filler (the filler is composed of illite and potassium feldspar in a mass ratio of 1:0.2), a curing agent (the curing agent is composed of toluene diisocyanate and diethylenetriamine in a mass ratio of 1:2), a catalyst (dibutyltin dilaurate), water, and an auxiliary agent (the auxiliary agent is composed of dimethylpolysiloxane and phosphate in a mass ratio of 1:0.8) are mixed, the stirring speed during mixing is 1000 rpm, and the dispersion time is 10 minutes, and then added to the film-forming emulsion, mixed (the stirring speed during mixing is 1500 rpm, and the dispersion time is 8 minutes), to prepare a cathode electrophoretic coating;

[0047] The weight ratio of the film-forming emulsion, the filler, the curing agent, the catalyst, the water and the additive is 60:20:10:55:0.9.

[0048] Example 3

[0049] A method for preparing an impact-resistant cathode electrophoretic coating comprises the following steps:

[0050] (1) adding epoxy resin (bisphenol A epoxy resin) to a mixed solvent of ethyl acetate and benzyl glycidyl ether (the volume ratio of ethyl acetate to benzyl glycidyl ether is 2:1) (the volume ratio of epoxy resin to the mixed solvent is 1:3), then adding 2,2',6,6'-tetrahydroxybiphenyl and dihydroxy-terminated polydimethylsiloxane, stirring and mixing, then adding an emulsifier (the emulsifier is composed of polysorbate 80 and sodium dodecyl sulfate in a mass ratio of 1:2), dispersing, the stirring speed during dispersion is 1000 rpm, the dispersion time is 15 minutes, and a film-forming emulsion is obtained, wherein the mass ratio of epoxy resin, 2,2',6,6'-tetrahydroxybiphenyl, dihydroxy-terminated polydimethylsiloxane, and emulsifier is 50:15:10:5;

[0051] (2) a filler (illite), a curing agent (the curing agent is composed of toluene diisocyanate and diethylenetriamine in a mass ratio of 1:1.2), a catalyst (dibutyltin dilaurate), water, an auxiliary agent (the auxiliary agent is composed of dimethyl polysiloxane and phosphate in a mass ratio of 1:1), and phloroglucinol are mixed, the stirring speed during mixing is 800 rpm, and the dispersion time is 10 minutes, and then added to the film-forming emulsion, mixed (the stirring speed during mixing is 1200 rpm, and the dispersion time is 8 minutes), to prepare a cathode electrophoretic coating;

[0052] The weight ratio of film-forming emulsion, filler, curing agent, catalyst, water and additive is 60:15:12:50:0.8;

[0053] The mass ratio of phloroglucinol to the film-forming emulsion is 0.8:20.

[0054] Example 4

[0055] A method for preparing an impact-resistant cathode electrophoretic coating comprises the following steps:

[0056] (1) adding epoxy resin (bisphenol A epoxy resin) to a mixed solvent of ethyl acetate and benzyl glycidyl ether (the volume ratio of ethyl acetate to benzyl glycidyl ether is 2:1) (the volume ratio of epoxy resin to the mixed solvent is 1:3), then adding 2,2',6,6'-tetrahydroxybiphenyl and dihydroxy-terminated polydimethylsiloxane, stirring and mixing, then adding an emulsifier (the emulsifier is polysorbate 80), dispersing, the stirring speed during dispersion is 1000 rpm, the dispersion time is 15 minutes, and a film-forming emulsion is obtained, wherein the mass ratio of epoxy resin, 2,2',6,6'-tetrahydroxybiphenyl, dihydroxy-terminated polydimethylsiloxane, and emulsifier is 50:15:10:5;

[0057] (2) a filler (illite), a curing agent (the curing agent is composed of toluene diisocyanate and diethylenetriamine in a mass ratio of 1:1.2), a catalyst (dibutyltin dilaurate), water, and an auxiliary agent (the auxiliary agent is composed of dimethylpolysiloxane and phosphate in a mass ratio of 1:1) are mixed, the stirring speed during mixing is 800 rpm, and the dispersion time is 10 minutes, and then added to the film-forming emulsion, mixed (the stirring speed during mixing is 1200 rpm, and the dispersion time is 8 minutes), to prepare a cathode electrophoretic coating;

[0058] The weight ratio of the film-forming emulsion, filler, curing agent, catalyst, water and additive is 60:15:12:50:0.8.

[0059] Comparative Example 1

[0060] Compared with Example 1, the only difference of Comparative Example 1 is that an equal amount of bisphenol A epoxy resin is used to replace 2,2',6,6'-tetrahydroxybiphenyl in Comparative Example 1, and the rest of the process is the same as that of Example 1.

[0061] Comparative Example 2

[0062] Compared with Example 1, the difference of Comparative Example 2 is that an equal amount of bisphenol A epoxy resin is used to replace bishydroxy-terminated polydimethylsiloxane in Comparative Example 2, and the rest of the process is the same as that of Example 1.

[0063] Product effect testing

[0064] The cathode electrophoretic coating prepared in the above-mentioned Examples 1-4 and Comparative Examples 1-2 was used to prepare an electrophoretic paint coating. The coating preparation conditions were as follows: electrophoretic temperature: 25°C, voltage 120V, electrophoretic time 4 minutes, after the electrophoresis was completed, the temperature was kept at 70°C for 30 minutes, and then further heated to 140°C and kept for 30 minutes. The coating thickness was about 20 μm. The impact strength of the coating was then tested according to the following standards, and the results are shown in Table 1.

[0065] Impact strength test: refer to GB1732-79 "Determination of impact resistance of paint film".

[0066] Table 1

[0067] Impact strength (kg / cm) Example 1 64.5 Example 2 62.9 Example 3 68.0 Example 4 64.1 Comparative Example 1 58.3 Comparative Example 2 59.7

[0068] It can be seen from Table 1 that the impact resistance of the coating formed by the cathodic electrophoretic coating prepared in the example is significantly better than that of the comparative example.

[0069] It can be seen from Example 1 and Comparative Examples 1-2 that 2,2',6,6'-tetrahydroxybiphenyl and dihydroxy-terminated polydimethylsiloxane have a significant effect on the impact resistance of the coating and affect the stability of the spatial network structure of the coating.

[0070] It can be seen from Example 1 and Example 3 that further adding phloroglucinol helps to improve the impact resistance of the coating.

[0071] In addition, the gloss of the coatings formed in Example 1 and Example 3 was tested. The gloss test was conducted in accordance with GB / T9754-1998 "Determination of 20°, 60° and 85° specular gloss of paints and varnishes without metallic pigments"; the results showed that the 60° gloss of the coating corresponding to Example 1 was 92%, while the 60° gloss of the coating corresponding to Example 3 was 97%. It can be seen that phloroglucinol is beneficial to further improve the gloss of the coating, making the appearance of the paint film more beautiful.

Claims

1. A method for preparing a cathodic electrophoretic coating, characterized in that: The following steps are involved: (1) adding epoxy resin to a mixed solvent of ethyl acetate and benzyl glycidyl ether, then adding 2,2',6,6'-tetrahydroxybiphenyl and dihydroxy-terminated polydimethylsiloxane, stirring and mixing, and then adding an emulsifier, dispersing, and obtaining a film-forming emulsion; (2) The filler, curing agent, catalyst, water and auxiliary agent are mixed, and then added into the film-forming emulsion, and mixed to obtain the cathode electrophoretic coating.

2. The preparation method according to claim 1, characterized in that: In step (1), the epoxy resin includes bisphenol A epoxy resin and / or bisphenol F epoxy resin.

3. The preparation method according to claim 1, characterized in that: In step (1), the mass ratio of the epoxy resin, 2,2',6,6'-tetrahydroxybiphenyl, dihydroxy-terminated polydimethylsiloxane, and emulsifier is 50:(5-20):(5-20):(2-10).

4. The preparation method according to claim 1, characterized in that: In step (1), the emulsifier is at least one of polysorbate 80, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and polyoxyethylene ether.

5. The preparation method according to claim 4, characterized in that: The emulsifier is composed of polysorbate 80 and at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate and polyoxyethylene ether.

6. The preparation method according to claim 1, characterized in that: In step (2), the curing agent includes isocyanate and diethylenetriamine.

7. The preparation method according to claim 1, characterized in that: In step (2), the weight ratio of the film-forming emulsion, filler, curing agent, catalyst, water and auxiliary agent is 60:(5-35):(10-22):(1-5):(25-80):(0.5-8).

8. The preparation method according to claim 1, characterized in that: When the auxiliary agent is added, phloroglucinol is also added.

9. A cathodic electrophoretic coating, characterized in that: The method is prepared according to any one of claims 1 to 8.

10. Use of the cathodic electrophoretic coating according to claim 9 in the fields of automobiles, hardware and building materials or household appliances.