A high-penetration electrophoretic coating, its preparation method and application

Abstract

This invention belongs to the field of coating technology and discloses a high-penetration electrophoretic coating, its preparation method, and its application. The preparation method includes the following steps: mixing epoxy resin, dihydroxypolydimethylsiloxane, adamantane, a silane coupling agent, alcohol, and water; then adding modified pigments and additives and mixing to obtain the electrophoretic coating. The preparation of the modified pigment includes the following steps: mixing pigment, polyethylene glycol, a silane coupling agent, 2,2-dimethylolpropionic acid, sodium dodecyl sulfonate, and water to obtain the modified pigment. The electrophoretic coating of this invention has a penetration rate exceeding 66.0%, even reaching 71.1%, and the impact strength of the coating film formed by the electrophoretic coating can exceed 58 kg·cm.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, and specifically relates to a high-penetration electrophoretic coating, its preparation method, and its application. Background Technology

[0002] Cathodic electrophoretic coatings are a common type of coating, often applied to the surface of metal parts. They not only enhance aesthetics but also significantly improve corrosion protection. However, existing metal parts are often irregularly shaped, with uneven surfaces such as protrusions, depressions, and gaps. This irregularity leads to uneven film formation by some existing electrophoretic coatings on the surface (e.g., thicker film in some areas, thinner film in some cavities, or even no film formation in some places). This is mainly attributed to the poor penetration of the electrophoretic coating. Electrophoretic coatings with poor penetration can result in significant differences in corrosion resistance across different locations on the same metal part, negatively impacting its service life. Uneven film formation also leads to a poor appearance of the metal parts.

[0003] Existing electrophoretic coatings have also made improvements to address the aforementioned film-forming problems. However, these improvements often require complex modification of the epoxy resin, which undoubtedly increases the manufacturing cost of the electrophoretic coatings. Moreover, the penetration of the prepared electrophoretic coatings is generally difficult to exceed 66.0% (using the four-element test), and the impact strength of the film is often only around 52 kg·cm, which is insufficient to meet further industrial requirements.

[0004] Therefore, there is an urgent need to provide a new electrophoretic coating with good penetration and good film appearance. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a high-penetration electrophoretic coating, its preparation method, and its application. The electrophoretic coating of the present invention has a penetration rate exceeding 66.0%, and can even reach 71.1%, and the impact strength of the coating film formed by the electrophoretic coating can exceed 58 kg·cm.

[0006] The inventive concept of this invention is as follows: The electrophoretic coating is prepared directly using epoxy resin, dihydroxy polydimethylsiloxane, adamantane, a silane coupling agent, alcohols, modified pigments, additives, and water. Specifically, epoxy resin, dihydroxy polydimethylsiloxane, and adamantane are used as the film-forming base components of the coating. The introduction of dihydroxy polydimethylsiloxane not only introduces siloxane groups but also facilitates the interaction of the dihydroxy structure with other components, forming a more stable network structure. The unique skeleton structure of adamantane further enhances the space of the coating after film formation, which is beneficial for the compatibility and dispersion uniformity of the modified pigments and film-forming substances. The pigments are modified with polyethylene glycol, a silane coupling agent, and 2,2-dimethylolpropionic acid, resulting in a hydroxyl-grafted structure on the pigment surface. This not only improves the dispersion stability of the pigments but also significantly enhances the compatibility between the modified pigments and film-forming substances, thereby improving the electrophoretic coating's penetration and impact resistance. In the process of preparing electrophoretic coatings, graphene oxide is further added. Due to the special two-dimensional electronic structure of graphene oxide, it has electronic interactions with pigments and adamantane, thereby further improving the electrophoretic coating's penetration.

[0007] The first aspect of the present invention provides a method for preparing a high-penetration electrophoretic coating.

[0008] Specifically, a method for preparing a high-penetration electrophoretic coating includes the following steps:

[0009] Epoxy resin, dihydroxy polydimethylsiloxane, adamantane, silane coupling agent, alcohol, and water are stirred and mixed, and then modified pigments and additives are added and mixed to obtain the electrophoretic coating.

[0010] The preparation process of the modified pigment includes the following steps: mixing pigment, polyethylene glycol, silane coupling agent, 2,2-dimethylolpropionic acid, sodium dodecyl sulfonate, and water to obtain the modified pigment.

[0011] Preferably, the weight ratio of the epoxy resin, dihydroxypolydimethylsiloxane, adamantane, silane coupling agent, alcohol, water, and modified pigment is 50:(8-15):(0.3-3):(5-15):(3-15):(50-120):(40-80); more preferably, it is 50:(10-15):(0.5-1.5):(6-12):(5-12):(60-100):(40-80). A reasonable selection of the proportions of each component is beneficial for obtaining electrophoretic coatings with good performance.

[0012] Preferably, the preparation process of the modified pigment includes the following steps: according to the weight parts, 10 parts of pigment, 10-20 parts of polyethylene glycol, 8-20 parts of silane coupling agent, 1-5 parts of 2,2-dimethylolpropionic acid, 3-10 parts of sodium dodecyl sulfonate, and 50-100 parts of water are stirred and mixed to obtain the modified pigment.

[0013] More preferably, the preparation process of the modified pigment includes the following steps: according to the weight parts, 10 parts pigment, 10-20 parts polyethylene glycol, 8-20 parts silane coupling agent, 1-5 parts 2,2-dimethylolpropionic acid, 3-10 parts sodium dodecyl sulfonate, and 50-100 parts water are stirred and mixed at 60-90°C for 1-3 hours to obtain the modified pigment.

[0014] Preferably, the epoxy resin is selected from bisphenol A type epoxy resin and / or bisphenol F type epoxy resin; more preferably, the epoxy resin is composed of bisphenol A type epoxy resin and bisphenol F type epoxy resin in a weight ratio of 1:(0.8-1.2). At this ratio, the obtained electrophoretic coating has better performance.

[0015] Preferably, the alcohol is selected from at least one of ethanol, 1,2-butanediol or glycerol.

[0016] Preferably, the pigment is selected from either titanium dioxide or iron oxide.

[0017] Preferably, the additives include at least one of curing agents, surfactants, defoamers, antioxidants, and ultraviolet absorbers.

[0018] Preferably, the curing agent is selected from at least one of diethylenetriamine, allyl ether, and phthalic anhydride.

[0019] Preferably, the surfactant is selected from at least one of sodium dodecyl sulfonate or sodium hexadecyl sulfonate.

[0020] Preferably, the defoamer is silicone oil.

[0021] Preferably, the antioxidant is selected from at least one of antioxidant 1010 or antioxidant 168.

[0022] Preferably, the ultraviolet absorber includes at least one of phenyl phthalate or 2,4-dihydroxybenzophenone.

[0023] Preferably, the solvent is water, and more preferably deionized water.

[0024] Preferably, the silane coupling agent is selected from at least one of KH550 or KH560.

[0025] Preferably, a method for preparing a high-penetration electrophoretic coating includes the following steps:

[0026] Epoxy resin, dihydroxypolydimethylsiloxane, adamantane, silane coupling agent, alcohol, and water are stirred and mixed at a temperature of 60-80°C for 30-60 minutes. Then, modified pigments and additives are added. The weight ratio of epoxy resin, dihydroxypolydimethylsiloxane, adamantane, silane coupling agent, alcohol, water, and modified pigments is 50:(8-15):(0.3-3):(5-15):(3-15):(50-120):(40-80), and the weight ratio of epoxy resin to additives is 50:(3-20). The mixture is stirred at a speed of 800-1500 rpm for 20-40 minutes to obtain the electrophoretic coating.

[0027] The preparation process of the modified pigment includes the following steps: according to the weight parts, 10 parts pigment, 10-20 parts polyethylene glycol, 8-20 parts silane coupling agent, 1-5 parts 2,2-dimethylolpropionic acid, 3-10 parts sodium dodecyl sulfonate, and 50-100 parts water are stirred and mixed at 60-90°C for 1-3 hours to obtain the modified pigment.

[0028] Preferably, graphene oxide is also added when adding epoxy resin. For example, 0.1-1 parts of graphene oxide are added. The addition of graphene oxide helps to improve the penetration of the electrophoretic coating.

[0029] A second aspect of the present invention provides a high-penetration electrophoretic coating.

[0030] Specifically, a method for preparing a high-penetration electrophoretic coating is described above.

[0031] Preferably, the electrophoretic coating has a penetration rate of over 66.0%, for example, a penetration rate of 67.0-71.0%, or even up to 71.1%.

[0032] Preferably, the impact strength of the coating film formed by the electrophoretic coating can exceed 58 kg·cm, for example, the impact strength can be 59-65 kg·cm.

[0033] A third aspect of the present invention provides an application of a high-penetration electrophoretic coating.

[0034] A metal device comprising a film layer formed by the aforementioned electrophoretic coating.

[0035] Preferably, the metal device is a metal device containing iron, aluminum, or copper. For example, metal parts in household appliances.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] (1) The present invention directly prepares the electrophoretic coating using epoxy resin, dihydroxy polydimethylsiloxane, adamantane, silane coupling agent, alcohol, modified pigment, additives, and water. In this invention, epoxy resin, dihydroxy polydimethylsiloxane, and adamantane are used as the film-forming base components of the coating. The introduction of dihydroxy polydimethylsiloxane not only introduces siloxane groups, but the dihydroxy structure also facilitates interaction with other components, forming a more stable network structure. The unique dry skeleton structure of adamantane further enhances the space of the coating after film formation, which is beneficial to the compatibility and dispersion uniformity of the modified pigment and the film-forming substance. The pigment is modified by polyethylene glycol, silane coupling agent, and 2,2-dimethylolpropionic acid, resulting in a hydroxyl-grafted structure on the pigment surface. This not only improves the dispersion stability of the pigment but also significantly enhances the compatibility between the modified pigment and the film-forming substance, thereby improving the electrophoretic coating's penetration and impact resistance.

[0038] (2) In the process of preparing the electrophoretic coating, graphene oxide is further added. Due to the special two-dimensional electronic structure of graphene oxide, there is an electronic interaction between it and the pigment and adamantane, which further enhances the electrophoretic coating's penetration. Detailed Implementation

[0039] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0040] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0041] Example 1: Preparation of Electrophoretic Coating

[0042] A method for preparing a high-penetration electrophoretic coating includes the following steps:

[0043] Epoxy resin (bisphenol A type epoxy resin and bisphenol F type epoxy resin, weight ratio 1:1), dihydroxy polydimethylsiloxane, adamantane, silane coupling agent KH560, alcohol (glycerol), and water were stirred and mixed at 70°C for 40 minutes. Then, modified pigments and additives (1 part diethylenetriamine, 2 parts allyl ether, 2 parts phthalic anhydride, 1.5 parts sodium dodecyl sulfonate, and 1.5 parts silicone oil) were added. The weight ratio of epoxy resin, dihydroxy polydimethylsiloxane, adamantane, silane coupling agent, alcohol, water, and modified pigment was 50:10:1:8:10:80:70, and the weight ratio of epoxy resin to additives was 50:8. The mixture was stirred at 1000 rpm for 30 minutes to obtain an electrophoretic coating.

[0044] The preparation process of the modified pigment includes the following steps: according to the weight parts, 10 parts of titanium dioxide, 15 parts of polyethylene glycol, 10 parts of silane coupling agent KH560, 4 parts of 2,2-dimethylolpropionic acid, 5 parts of sodium dodecyl sulfonate, and 55 parts of water are stirred and mixed at 80°C for 2.5 hours to obtain the modified pigment.

[0045] Example 2: Preparation of Electrophoretic Coating

[0046] A method for preparing a high-penetration electrophoretic coating includes the following steps:

[0047] Epoxy resin (bisphenol A type epoxy resin and bisphenol F type epoxy resin, weight ratio 1:0.8), dihydroxy polydimethylsiloxane, adamantane, silane coupling agent KH550, alcohol (glycerol), and water were stirred and mixed at 75°C for 35 minutes. Then, modified pigments and additives (1 part diethylenetriamine, 2 parts allyl ether, 2 parts phthalic anhydride, 1 part sodium dodecyl sulfonate, 2 parts silicone oil, and 0.5 parts antioxidant 1010) were added. The weight ratio of epoxy resin, dihydroxy polydimethylsiloxane, adamantane, silane coupling agent, alcohol, water, and modified pigment was 50:12:0.8:7:12:85:65, and the weight ratio of epoxy resin to additives was 50:8.5. The mixture was stirred at 1200 rpm for 40 minutes to obtain an electrophoretic coating.

[0048] The preparation process of the modified pigment includes the following steps: according to the weight parts, 10 parts of titanium dioxide, 12 parts of polyethylene glycol, 11 parts of silane coupling agent KH550, 2 parts of 2,2-dimethylolpropionic acid, 5 parts of sodium dodecyl sulfonate, and 50 parts of water are stirred and mixed at 85°C for 2 hours to obtain the modified pigment.

[0049] Example 3: Preparation of Electrophoretic Coating

[0050] A method for preparing a high-penetration electrophoretic coating includes the following steps:

[0051] Epoxy resin (bisphenol A type epoxy resin and bisphenol F type epoxy resin, weight ratio 1:1.2), dihydroxy polydimethylsiloxane, adamantane, silane coupling agent KH550, alcohol (glycerol), and water were stirred and mixed at 75°C for 35 minutes. Then, modified pigments and additives (1 part diethylenetriamine, 2 parts allyl ether, 2 parts phthalic anhydride, 1 part sodium dodecyl sulfonate, 2 parts silicone oil, and 0.5 parts antioxidant 1010) were added. The weight ratio of epoxy resin, dihydroxy polydimethylsiloxane, adamantane, silane coupling agent, alcohol, water, and modified pigment was 50:11:0.9:8:12:85:65, and the weight ratio of epoxy resin to additives was 50:8.5. The mixture was stirred at 1200 rpm for 40 minutes to obtain an electrophoretic coating.

[0052] The preparation process of the modified pigment includes the following steps: according to the weight parts, 10 parts of iron oxide, 17 parts of polyethylene glycol, 12 parts of silane coupling agent KH550, 3 parts of 2,2-dimethylolpropionic acid, 5 parts of sodium dodecyl sulfonate, and 50 parts of water are stirred and mixed at 85°C for 2 hours to obtain the modified pigment.

[0053] Example 4: Preparation of Electrophoretic Coating

[0054] A method for preparing a high-penetration electrophoretic coating includes the following steps:

[0055] Epoxy resin (bisphenol A type epoxy resin and bisphenol F type epoxy resin, weight ratio 1:1), graphene oxide, dihydroxy polydimethylsiloxane, adamantane, silane coupling agent KH560, alcohol (glycerol), and water were mixed at 70°C for 40 minutes. Then, modified pigments and additives (1 part diethylenetriamine, 2 parts allyl ether, 2 parts phthalic anhydride, and 1 part sodium dodecyl sulfonate) were added. The following ingredients were mixed: 1.5 parts epoxy resin, 1.5 parts silicone oil, epoxy resin, dihydroxypolydimethylsiloxane, adamantane, silane coupling agent, alcohol, water, and modified pigment in a weight ratio of 50:10:1:8:10:80:70; epoxy resin to graphene oxide in a weight ratio of 50:0.2; and epoxy resin to additives in a weight ratio of 50:8. The mixture was stirred at 1000 rpm for 30 minutes to obtain an electrophoretic coating.

[0056] The preparation process of the modified pigment includes the following steps: according to the weight parts, 10 parts of titanium dioxide, 15 parts of polyethylene glycol, 10 parts of silane coupling agent KH560, 4 parts of 2,2-dimethylolpropionic acid, 5 parts of sodium dodecyl sulfonate, and 55 parts of water are stirred and mixed at 80°C for 2.5 hours to obtain the modified pigment.

[0057] Example 5: Preparation of Electrophoretic Coating

[0058] A method for preparing a high-penetration electrophoretic coating includes the following steps:

[0059] Epoxy resin (bisphenol A type epoxy resin), dihydroxy polydimethylsiloxane, adamantane, silane coupling agent KH560, alcohol (glycerol), and water were stirred and mixed at 70°C for 40 minutes. Then, modified pigments and additives (1 part diethylenetriamine, 2 parts allyl ether, 2 parts phthalic anhydride, 1.5 parts sodium dodecyl sulfonate, and 1.5 parts silicone oil) were added. The weight ratio of epoxy resin, dihydroxy polydimethylsiloxane, adamantane, silane coupling agent, alcohol, water, and modified pigment was 50:10:1:8:10:80:70, and the weight ratio of epoxy resin to additives was 50:8. The mixture was stirred at 1000 rpm for 30 minutes to obtain an electrophoretic coating.

[0060] The preparation process of the modified pigment includes the following steps: according to the weight parts, 10 parts of titanium dioxide, 15 parts of polyethylene glycol, 10 parts of silane coupling agent KH560, 4 parts of 2,2-dimethylolpropionic acid, 5 parts of sodium dodecyl sulfonate, and 55 parts of water are stirred and mixed at 80°C for 2.5 hours to obtain the modified pigment.

[0061] Comparative Example 1

[0062] Compared with Example 1, in Comparative Example 1, an equal amount of dihydroxypolydimethylsiloxane was used instead of adamantane, and the remaining components and processes were the same as in Example 1.

[0063] Comparative Example 2

[0064] Compared with Example 1, in the preparation process of the modified pigment in Comparative Example 2, 2,2-dimethylolpropionic acid was not used, and the remaining components and processes were the same as in Example 1.

[0065] Comparative Example 3

[0066] Compared with Example 1, in Comparative Example 1, polyethylene glycol was used instead of dihydroxypolydimethylsiloxane in an equal amount, and the remaining components and processes were the same as in Example 1.

[0067] Product effectiveness test

[0068] Electrophoretic coatings prepared in Examples 1, 4, and 5, and Comparative Examples 1-3, were subjected to electrophoretic coating. During the electrophoretic coating process, the electrophoresis tank temperature was set to 25°C, the anode was a stainless steel container, and the cathode was a cold-rolled steel sheet treated with zinc phosphate (200mm long, 80mm wide, and 2mm thick). Electrophoresis was performed at 250V for 3 minutes. After coating, the coated cold-rolled steel sheet was removed from the electrophoresis tank, rinsed three times with water, and baked at 160°C for 18 minutes to form an electrophoretic coating layer on the cold-rolled steel sheet. The appearance of the film layer on the surface of the cold-rolled steel sheet was then observed, and the penetration performance was tested (referring to HG / T 3334-2012 "General Test Methods for Electrophoretic Coatings": 4.3.2 "Penetration Strength of Electrophoretic Coatings - Four-Piece Box Method"). The impact resistance of the film layer was also tested (referring to GB / T 1732-79 "Determination of Impact Resistance of Paint Films"). The results are shown in Table 1.

[0069] Table 1

[0070]

[0071]

[0072] As can be seen from Table 1, the electrophoretic coatings prepared in the examples have significantly better film appearance, penetration, and impact resistance than comparative examples 1-3.

[0073] The results from Examples 1 and Comparative Examples 1-3 show that the use of dihydroxypolydimethylsiloxane, adamantane, and 2,2-dimethylolpropionic acid has a significant impact on the performance of the membrane. Examples 1 and 4 show that the addition of graphene oxide helps to further improve the permeability of the membrane. The epoxy resin in Example 5 was a bisphenol A type epoxy resin, which resulted in a decrease in membrane performance compared to Example 1. Therefore, it is evident that a composite solution using bisphenol A type epoxy resin and bisphenol F type epoxy resin yields better membrane performance.

[0074] The effects of the other embodiments described above are similar to those of Embodiment 1.

[0075] Furthermore, the cold-rolled steel sheet corresponding to Example 1 of this invention and the coated workpiece prepared in Example 4 of CN109627951A were immersed in 0.1 mol / L hydrochloric acid at 40°C and the appearance of the surface film was observed. The results showed that the cold-rolled steel sheet corresponding to Example 1 of this invention began to show local pinholes after 36 hours, while the coated workpiece prepared in Example 4 of CN109627951A already showed local pinholes after 24 hours. This demonstrates that the film formed by the electrophoretic coating of this invention has better corrosion resistance.

Claims

1. A method for the preparation of an electrophoretic paint, characterized in that, The preparation method comprises the following steps: The epoxy resin, graphene oxide, dihydroxy polydimethylsiloxane, adamantane, silane coupling agent, alcohol, water are stirred and mixed, then the modified pigment and the additive are added and mixed to obtain the electrophoretic coating; the weight ratio of the epoxy resin, dihydroxy polydimethylsiloxane, adamantane, silane coupling agent, alcohol, water and modified pigment is 50: (8-15): (0.3-3): (5-15): (3-15): (50-120): (40-80); The epoxy resin is composed of bisphenol A type epoxy resin and bisphenol F type epoxy resin in a weight ratio of 1: (0.8-1.2) ; The preparation process of the modified pigment comprises the following steps: 10 parts of pigment, 10-20 parts of polyethylene glycol, 8-20 parts of silane coupling agent and 1-5 parts of 2, 2 dimethylol propionic acid, 3-10 parts of sodium dodecyl sulfonate and 50-100 parts of water are stirred and mixed to obtain the modified pigment; The pigment is selected from any one of titanium dioxide and iron oxide.

2. The production method according to claim 1, characterized by, The alcohol is selected from at least one of ethanol, 1, 2-butylene glycol or glycerol.

3. The preparation method according to claim 1, characterized in that, The additive comprises at least one of curing agent, surfactant, defoaming agent, antioxidant, ultraviolet absorber.

4. The production method according to claim 3, characterized by, The curing agent is selected from at least one of diethylene triamine, allyl ether and phthalic anhydride.

5. The preparation method according to claim 3, characterized in that, The surfactant is selected from at least one of sodium dodecyl sulfonate or sodium hexadecyl sulfonate; and / or, the defoaming agent is silicone oil; and / or, the antioxidant is selected from at least one of antioxidant 1010 or antioxidant 168; and / or, the ultraviolet absorber comprises at least one of phenyl o-hydroxybenzoate or 2, 4-dihydroxybenzophenone.

6. An electrocoat material characterized by comprising: The preparation method is prepared by any one of claims 1-5.

7. A metal device, characterized by The film layer formed by the electrophoretic coating of claim 6.

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