Coating composition, preparation method thereof, anodic electrophoretic paint and electronic equipment

Abstract

The invention provides a coating composition, a preparation method thereof, anodic electrophoretic paint and electronic equipment, the coating composition comprises an acrylic copolymer and a cross-linking agent, the acrylic copolymer comprises a structural unit derived from a (methyl) acrylic monomer, the structural units derived from the (methyl) acrylic monomer comprise at least one structural unit represented by a formula (I), at least one structural unit represented by a formula (II) and at least one structural unit represented by a formula (III), R5 is substituted, substituent groups at least comprise hydroxyl groups, the molar ratio of the structural units represented by the formula (I) is 14-22%, and the molar ratio of the structural units represented by the formula (III) is 4-12%. The molar ratio of the structural unit represented by the formula (III) is 2-5%, and the molar ratio of the structural unit in which R1, R2 and R3 are methyl to the structural unit in which R1, R2 and R3 are methyl is H is (0.7-1.3): 1. # imgabs0 #

Description

Technical Field

[0001] The present application relates to the technical field of coating compositions, and particularly relates to a coating composition with excellent comprehensive performance, a preparation method thereof, an anodic electrophoretic paint, and an electronic device. Background Art

[0002] With the rapid development of industries such as automobiles, household appliances, and 3C products, metal materials are widely used in many fields of these industries. In order to effectively protect the metal surface and improve the appearance, a paint film formed by an anodic electrophoretic paint can be covered on the metal surface. However, applying a conventional coating composition to the metal surface affects the appearance of the metal surface. Summary of the Invention

[0003] In view of this, the main purpose of the present application is to provide a coating composition. The paint film formed by the anodic electrophoretic paint made from this coating composition has good performance in terms of hardness, adhesion, and abrasion resistance on the metal surface.

[0004] To achieve the above purpose, the present application provides the following technical solutions.

[0005] The first aspect of the present application provides a coating composition, comprising an acrylic copolymer and a crosslinking agent. The acrylic copolymer comprises structural units derived from (meth)acrylic monomers. The structural units derived from (meth)acrylic monomers comprise at least one structural unit represented by formula (I), at least one structural unit represented by formula (II), and at least one structural unit represented by formula (III).

[0006]

[0007]

[0008] Among them, in formula (I), formula (II) and formula (III), R1, R2 and R3 are each independently H or methyl; in formula (II), R4 is a substituted or unsubstituted C1-C10 alkyl group, and the substitution means being substituted by one or more substituents selected from nitro group, cyano group, halogen atom, ester group, amide group, C1-C10 alkyl group, C1-C10 alkoxy group, 6- to 10-membered aryl group; in formula (III), R5 is a substituted C1-C10 alkyl group, and the substitution means being substituted by one or more substituents selected from hydroxyl group, nitro group, cyano group, halogen atom, ester group, amide group, C1-C10 alkyl group, C1-C10 alkoxy group, 6- to 10-membered aryl group, and the substituents include at least a hydroxyl group; relative to the total molar number of the structural units of the acrylic copolymer, the molar proportion of the structural unit represented by formula (I) is 14% to 22%; relative to the total molar number of the structural units of the acrylic copolymer, the molar proportion of the structural unit represented by formula (III) is 2% to 5%; relative to the total molar number of the structural units represented by formula (I), formula (II) and formula (III) in the structural units of the acrylic copolymer, the molar ratio of the structural unit in which R1, R2 and R3 are methyl to the structural unit in which R1, R2 and R3 are H is (0.7 to 1.3):1.

[0009] According to an embodiment of the present application, in formula (II), R4 is a substituted or unsubstituted C1-C10 alkyl group; in formula (III), R5 is a substituted C1-C10 alkyl group, and the substituent is a hydroxyl group.

[0010] According to an embodiment of the present application, in formula (II), R4 is a substituted or unsubstituted C1-C10 alkyl group; in formula (III), R5 is a substituted C1-C10 alkyl group, and the substituent is a hydroxyl group.

[0011] According to an embodiment of the present application, relative to the total molar number of the structural units of the acrylic copolymer, the molar proportion of the structural unit derived from (meth)acrylic monomers is 80% to 90%.

[0012] According to an embodiment of the present application, the mass ratio of the acrylic copolymer to the crosslinking agent is 100:(20 to 60).

[0013] According to an embodiment of the present application, the crosslinking agent is an etherified melamine formaldehyde resin.

[0014] The second aspect of the present application provides a method for preparing a coating composition according to any of the above embodiments. The method includes subjecting comonomers to a free radical polymerization reaction in an organic solvent to obtain a solution of an acrylic copolymer, wherein the comonomers include the (meth)acrylic monomers; and mixing the solution of the acrylic copolymer with a crosslinking agent to obtain the coating composition.

[0015] The third aspect of the present application provides an anodic electrophoretic paint, comprising a silane coupling agent and a coating composition, wherein the coating composition includes an acrylic copolymer and a crosslinking agent, the acrylic copolymer includes structural units derived from (meth)acrylic monomers, and the structural units derived from (meth)acrylic monomers include at least one structural unit represented by formula (I), at least one structural unit represented by formula (II), and at least one structural unit represented by formula (III).

[0016]

[0017] Wherein, in formula (I), formula (II), and formula (III), R1, R2, and R3 are each independently H or methyl.

[0018] In formula (II), R4 is a substituted or unsubstituted C1-C10 alkyl group, and the substitution means being substituted by one or more substituents selected from nitro, cyano, halogen atom, ester group, amide group, C1-C10 alkyl group, C1-C10 alkoxy group, and 6- to 10-membered aryl group.

[0019] In formula (III), R5 is a substituted C1-C10 alkyl group, and the substitution means being substituted by one or more substituents selected from hydroxyl, nitro, cyano, halogen atom, ester group, amide group, C1-C10 alkyl group, C1-C10 alkoxy group, and 6- to 10-membered aryl group, and the substituent includes at least hydroxyl.

[0020] Relative to the total molar amount of the structural units of the acrylic copolymer, the molar proportion of the structural unit represented by formula (I) is 14% to 22%.

[0021] Relative to the total molar amount of the structural units of the acrylic copolymer, the molar proportion of the structural unit represented by formula (III) is 2% to 5%.

[0022] Relative to the total molar amount of the structural units represented by formula (I), formula (II), and formula (III) in the structural units of the acrylic copolymer, the molar ratio of the structural unit in which R1, R2, and R3 are methyl to the structural unit in which R1, R2, and R3 are H is (0.7 to 1.3):1.

[0023] According to an embodiment of the present application, relative to the mass of the electrophoretic paint, the mass percentage of the acrylic copolymer is 7% to 10%, and the mass percentage of the silane coupling agent is 0.2% to 0.6%.

[0024] According to an embodiment of the present application, the pH of the anodic electrophoretic paint is 8 to 10.

[0025] A fourth aspect of the present application provides an electronic device, including a main body and a housing for accommodating the main body. The main body includes electronic components, and the housing includes a metal appearance structure member. The metal appearance structure member includes a paint film and a substrate. The substrate is made of a metal material. On at least one surface of the substrate, the paint film is formed by depositing an anodic electrophoretic paint on the surface through an anodic electrophoretic process and baking and curing. Among them, the anodic electrophoretic paint includes a silane coupling agent and a coating composition. The coating composition includes an acrylic copolymer and a crosslinking agent. The acrylic copolymer includes structural units derived from (meth)acrylic monomers. The structural units derived from (meth)acrylic monomers include at least one structural unit represented by formula (I), at least one structural unit represented by formula (II), and at least one structural unit represented by formula (III).

[0026]

[0027] Among them, in formula (I), formula (II), and formula (III), R1, R2, and R3 are each independently H or methyl;

[0028] In formula (II), R4 is a substituted or unsubstituted C1-C10 alkyl group, and the substitution means being substituted by one or more substituents selected from nitro, cyano, halogen atom, ester group, amide group, C1-C10 alkyl group, C1-C10 alkoxy group, and 6- to 10-membered aryl group;

[0029] In formula (III), R5 is a substituted C1-C10 alkyl group, and the substitution means being substituted by one or more substituents selected from hydroxyl, nitro, cyano, halogen atom, ester group, amide group, C1-C10 alkyl group, C1-C10 alkoxy group, and 6- to 10-membered aryl group, and the substituent at least includes a hydroxyl group;

[0030] Relative to the total molar number of the structural units of the acrylic copolymer, the molar proportion of the structural unit represented by formula (I) is 14% to 22%;

[0031] Relative to the total molar number of the structural units of the acrylic copolymer, the molar proportion of the structural unit represented by formula (III) is 2% to 5%;

[0032] With respect to the total molar number of the structural units represented by formula (I), the structural units represented by formula (II), and the structural units represented by formula (III) in the structural units of the acrylic copolymer, the molar ratio of the structural units in which R1, R2, and R3 are methyl groups to the structural units in which R1, R2, and R3 are methyl groups and H is 1 is (0.7 to 1.3):1.

[0033] According to an embodiment of the present application, the metal material of the housing is a magnesium alloy.

[0034] According to an embodiment of the present application, the target area of the metal appearance structural member includes a sealing substance for sealing the target area of the substrate, and the sealing substance includes a corrosion inhibitor.

[0035] In addition to the technical problems solved by the present application, the technical features constituting the technical solution, and the beneficial effects brought by these technical features described above, other technical problems that the present application can solve, other technical features included in the technical solution, and the beneficial effects brought by these technical features will be further described in detail in the following specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0037] Figure 1 It is a schematic cross-sectional view of an electronic device in an embodiment of the present application.

[0038] Figure 2 It is a schematic cross-sectional view of an electronic device in another embodiment of the present application.

[0039] Figure 3 It is a schematic cross-sectional view of an electronic device in yet another embodiment of the present application.

[0040] Figure 4 It is a flowchart of the penetration step of the preparation method of the housing of the electronic device in an embodiment of the present application.

[0041] Figure 5 It is a flowchart of the penetration step of the preparation method of the housing of the electronic device in another embodiment of the present application.

[0042] Figure 6 It is a flowchart of the preparation method of the housing of the electronic device in yet another embodiment of the present application.

[0043] Figure 7 Images after penetration, polishing, and electrophoresis in the method for preparing the housing of an electronic device in an embodiment of the present application. Detailed implementation manners

[0044] Next, the technical solutions of the present application will be clearly and completely described in conjunction with the detailed implementation manners. Obviously, the described implementation manners are only a part of the implementation manners of the present application, rather than all of the implementation manners. Based on the implementation manners in the present application, all other implementation manners obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present application.

[0045] Throughout the specification, unless otherwise specifically stated, the terms used herein should be understood as having the meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as the general understanding of those skilled in the art to which this application belongs. In case of conflict, this specification prevails.

[0046] It should be noted that in the present application, the term "including" or any other variant thereof is intended to cover non-exclusive inclusion, such that a method or device including a series of elements not only includes those elements explicitly recited, but also includes other elements not explicitly listed, or further includes elements inherent to the implementation of the method or device. Without further limitation, the elements defined by the statement "comprising..." do not preclude the presence of additional related elements in the method or device including such element.

[0047] Term definitions

[0048] As used herein, the term "(meth)acrylic acid" refers to acrylic acid and / or methacrylic acid.

[0049] As used herein, the term "monomer" is a molecule that can covalently bind to other molecules of the same type (and optionally, other types) to form a polymer, which is a macromolecule composed of several monomer residues.

[0050] The term "alkyl" includes both branched and straight-chain saturated aliphatic hydrocarbon groups and has a specified number of carbon atoms, for example, having 1 to 12 carbon atoms. As used herein, the term "C1-C10 alkyl" means an alkyl having 1 to 10 carbon atoms, such as C1-C8, C1-C6, or C1-C4 alkyl. Examples of alkyl include, but are not limited to: methyl, ethyl, n-propyl, isopropyl, n-butyl, 3-methylbutyl, tert-butyl, n-pentyl, sec-pentyl, hexyl, heptyl, octyl, isooctyl, nonyl, decyl.

[0051] The term "alkoxy" refers to an alkyl group as defined above having a specified number of carbon atoms connected by an oxygen bridge. As used herein, the term "C1-C10 alkoxy" means an alkyl group having 1 to 10 carbon atoms connected by an oxygen bridge, such as C1-C8, C1-C6, or C1-C4 alkoxy. Examples of alkoxy groups include, but are not limited to: methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy, heptyloxy, octyloxy, nonyloxy, decyloxy, 3-hexyloxy, and 3-methylpentyloxy.

[0052] The term "aryl" refers to an aromatic group having one or more rings formed by a backbone structure, for example, containing 5 to 14 carbon atoms. As described herein, a "6- to 10-membered aryl" contains 6 to 10 carbon atoms, such as phenyl and naphthyl.

[0053] As used herein, the term "substituted" or "substituent" means that at least one hydrogen atom of a group is replaced by a substituent.

[0054] Currently, the paint films formed by commercially available acrylic anodic electrophoretic paints commonly applicable to metals such as steel or aluminum alloy cannot balance wear resistance, adhesion, hardness, etc. Especially when such anodic electrophoretic paints are used for magnesium alloys, the above-mentioned various properties of the paint films are significantly insufficient, making it difficult to meet the relevant application requirements in 3C products and urgently needing to be further improved. This is because such anodic electrophoretic paints are often complex electrolyte mixtures, usually including (meth)acrylic monomers, crosslinking agents, and some additives (such as fillers, leveling agents, anti-cratering agents, light stabilizers, antioxidants, pH regulators, etc.); compared with steel or aluminum alloy, when magnesium alloy contacts the conventional acrylic anodic electrophoretic paint, it is more likely to corrode and form a loose layer on the surface, so the performance of the paint film formed thereon is worse.

[0055] Based on this, the present application provides a coating composition with excellent comprehensive performance, a preparation method thereof, an anodic electrophoretic paint, and an electronic device. The following provides a more specific description of the present application and optional embodiments.

[0056] Coating composition

[0057] A first aspect of the present application aims to provide a coating composition, including an acrylic copolymer and a crosslinking agent. The acrylic copolymer includes structural units derived from (meth)acrylic monomers, and the structural units derived from (meth)acrylic monomers include at least one structural unit represented by formula (I), at least one structural unit represented by formula (II), and at least one structural unit represented by formula (III).

[0058]

[0059]

[0060] Among them, in formula (I), formula (II) and formula (III), R1, R2 and R3 are each independently H or methyl; in formula (II), R4 is a substituted or unsubstituted C1-C10 alkyl group, and the substitution means being substituted by one or more substituents selected from nitro, cyano, halogen atom, ester group, amide group, C1-C10 alkyl group, C1-C10 alkoxy group, 6- to 10-membered aryl group; in formula (III), R5 is a substituted C1-C10 alkyl group, and the substitution means being substituted by one or more substituents selected from hydroxyl group, nitro, cyano, halogen atom, ester group, amide group, C1-C10 alkyl group, C1-C10 alkoxy group, 6- to 10-membered aryl group, and the substituents include at least a hydroxyl group; relative to the total molar number of the structural units of the acrylic copolymer, the molar proportion of the structural units represented by formula (I) is 14% to 22%; relative to the total molar number of the structural units of the acrylic copolymer, the molar proportion of the structural units represented by formula (III) is 2% to 5%; relative to the total molar number of the structural units represented by formula (I), formula (II) and formula (III) in the structural units of the acrylic copolymer, the molar ratio of the structural units in which R1, R2 and R3 are methyl to the structural units in which R1, R2 and R3 are H is (0.7 to 1.3):1.

[0061] The acrylic copolymer in the coating composition of the present application has both hydroxyl groups (in the structural unit of formula (III)) and carboxyl groups (in the structural unit of formula (I)) as reactive functional groups, and can react with the crosslinking agent of the present application during baking to form crosslinking points. It is generally considered that the structural unit with R1, R2, and R3 being H is a flexible segment, which is beneficial to improving the flexibility of the cured paint film; the structural unit with R1, R2, and R3 being methyl is a rigid segment, which is beneficial to improving the hardness of the cured paint film. Therefore, by increasing the ratio of methacrylic acid monomers to acrylic acid monomers, the hardness of the paint film formed by the electrophoretic paint including the coating composition can be improved. However, the inventors of the present application have found that no matter how the ratio of methacrylic acid monomers to acrylic acid monomers is adjusted, it is impossible to take into account the hardness, adhesion, and abrasion resistance of the paint film. Either the paint film is too soft, or cracks are easily generated, and the adhesion and abrasion resistance are insufficient. In addition, simply increasing the hydroxyl and carboxyl contents is not enough to fully improve the abrasion resistance and adhesion. Too high a hydroxyl content will have an adverse effect on water resistance. By making the molar proportion of the structural unit represented by formula (III) (i.e., the hydroxyl content in the acrylic copolymer) at a relatively low level in the present application, and at the same time the molar proportion of the structural unit represented by formula (I) (i.e., the carboxyl content in the acrylic copolymer) within the scope of the present application, the molar ratio of the structural unit with R1, R2, and R3 being methyl to the structural unit with R1, R2, and R3 being H (i.e., the ratio of methacrylic acid monomers to acrylic acid monomers) can be at a relatively low level in the present application, improving the hardness of the paint film and taking into account the adhesion and abrasion resistance. In addition, the paint film formed by the electrophoretic paint including the coating composition of the present application has good transparency and gloss, reducing white spots and bubbles.

[0062] In formulas (I), (II) and (III), R1, R2 and R3 are each independently H or methyl. That is, a structural unit has the structure represented by formula (I), where R1 can be H or methyl, regardless of whether R1, R2 or R3 in other structural units having the structures represented by formula (I), formula (II) or formula (III) is H or methyl. Similarly, a structural unit has the structure represented by formula (II), where R2 can be H or methyl, regardless of whether R1, R2 or R3 in other structural units having the structures represented by formula (I), formula (II) or formula (III) is H or methyl. Similarly, a structural unit has the structure represented by formula (III), where R3 can be H or methyl, regardless of whether R1, R2 or R3 in other structural units having the structures represented by formula (I), formula (II) or formula (III) is H or methyl. Exemplarily, the structural units derived from (meth)acrylic acid monomers include two structural units represented by formula (II), wherein, for the two structural units, R2 is H for both, or R2 is methyl for both, or R2 is H for one structural unit and R2 is methyl for the other structural unit.

[0063] Relative to the total molar amount of the structural units of the acrylic copolymer, the molar proportion of the structural unit represented by formula (I) is 14% to 22%. Exemplarily, the above molar proportion can be 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, or a value between any two values, but is not limited thereto. The structural unit represented by formula (I) may contain a carboxyl group and can also form an anion after adjusting the pH, which is beneficial for anodic deposition during electrophoresis.

[0064] Relative to the total molar amount of the structural units of the acrylic copolymer, the molar proportion of the structural unit represented by formula (III) is 2% to 5%. Exemplarily, the above molar proportion can be 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or a value between any two values, but is not limited thereto.

[0065] Relative to the total molar amount of the structural units represented by formula (I), formula (II) and formula (III) in the structural units of the acrylic copolymer, the molar ratio of the structural unit with R1, R2 and R3 being methyl to the structural unit with R1, R2 and R3 being H is (0.7 to 1.3):1. Exemplarily, the above molar ratio can be 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1 or a value between any two values, but is not limited thereto.

[0066] In this text, the term "hardness" refers to the ability of a paint film to resist the penetration of a hard object into its surface, which can be measured with reference to ASTM D3363. Exemplarily, a Mitsubishi Uni pencil can be used to draw across the paint film with a tip load of 500 g, starting from the hardest pencil until the paint film is scratched; the hardness of the hardest pencil that does not scratch the paint film is the hardness of the paint film.

[0067] In this text, the term "adhesion" refers to the adhesion of a relatively ductile paint film on a metal substrate evaluated by applying and removing a pressure-sensitive tape on a cut made in the paint film, which can be measured with reference to ASTM D3359. Exemplarily, at the cut where the paint film is scratched with a knife, a 3M610 tape, for example, can be applied and removed, and then, according to the image Figure 1 shown, a grade from 0B to 5B can be evaluated.

[0068] In this text, the term "abrasion resistance" refers to the ability of a paint film to resist wear and tear, which can be obtained by performing an RCA abrasion resistance test with reference to ASTM F2357. Exemplarily, a Norman abrasion tester (type IBB) can be used to perform 175 g cyclic friction until visual changes are detected, and the number of cycles is recorded as a measure of the RCA abrasion resistance.

[0069] According to some embodiments, in formula (II), R4 is a substituted or unsubstituted C1-C10 alkyl group; in formula (III), R5 is a substituted C1-C10 alkyl group, and the substituent is a hydroxyl group. Thus, it is more conducive to reducing raw material costs and is economical and environmentally friendly. Exemplarily, in formula (II), R4 can be a substituted or unsubstituted C1-C4 alkyl group; in formula (III), R5 can be a substituted C1-C4 alkyl group.

[0070] According to some embodiments, relative to the total molar amount of the structural units of the acrylic copolymer, the molar proportion of the structural units derived from (meth)acrylic monomers is 80% to 90%. Exemplarily, the above molar proportion can be 80%, 82%, 84%, 86%, 88%, 90% or a value within the range composed of any two values, but is not limited thereto.

[0071] According to some embodiments, in the coating composition, the mass ratio of the acrylic copolymer to the crosslinking agent is 100:(20-60). Exemplarily, the above mass ratio can be 100:20, 100:30, 100:40, 100:50, 100:60 or a value within the range composed of any two values, but is not limited thereto.

[0072] As a crosslinking agent, any one or a combination of multiple crosslinking agents can be used as long as it can coexist with hydroxyl groups and carboxyl groups stably at room temperature and can react with hydroxyl groups and carboxyl groups to form crosslinks after heat treatment. The crosslinking agent can be, but is not limited to, etherified melamine formaldehyde resin or blocked isocyanate crosslinking agent.

[0073] According to some embodiments, the crosslinking agent is an etherified melamine formaldehyde resin, such as methyl-etherified, butanol-etherified or isobutanol-etherified melamine resin. Thereby, it is beneficial to improve the water resistance of the paint film.

[0074] Preparation method of the coating composition

[0075] The present disclosure also provides a method for preparing the coating composition according to any of the above embodiments. The method includes subjecting the comonomers to a free radical polymerization reaction in an organic solvent to obtain a solution of an acrylic copolymer, wherein the comonomers include the (meth)acrylic monomers; and mixing the solution of the acrylic copolymer and the crosslinking agent to obtain the coating composition. Through the above free radical polymerization reaction process in solution, it is beneficial to control the stability of the polymerization process, make the quality of the acrylic copolymer in the coating composition stable, and the process is simple.

[0076] In this article, the term "(meth)acrylic monomer" refers to acrylic acid or methacrylic acid and derivatives obtained by its esterification or amidation reactions, such as monomers corresponding to the structural units represented by formula (I), (II), (III). The monomer corresponding to the structural unit represented by (I) is acrylic acid or methacrylic acid. The monomers corresponding to the structural unit represented by (II) include, but are not limited to, (meth)acrylic acid methyl ester, (meth)acrylic acid ethyl ester, (meth)acrylic acid propyl ester, (meth)acrylic acid butyl ester, (meth)acrylic acid hexyl ester, (meth)acrylic acid octyl ester, (meth)acrylic acid cyclohexyl ester, trifluoroethyl methacrylate, hexafluorobutyl methacrylate, etc. The monomers corresponding to the structural unit represented by (III) include, but are not limited to, (meth)acrylic acid hydroxyethyl ester, (meth)acrylic acid hydroxypropyl ester, (meth)acrylic acid hydroxybutyl ester, (meth)acrylic acid (poly)ethylene glycol monoester, (meth)acrylic acid (poly)propylene glycol monoester, etc.

[0077] As comonomers, other unsaturated monomers can also be included, such as styrene, (meth)acrylonitrile, butyl vinyl ether, (meth)allyl alcohol, etc.

[0078] As the organic solvent, any one or a combination of multiple solvents that can dissolve the acrylic copolymer at room temperature can be used. Exemplarily, the solvent can be isopropyl alcohol, butanol, ethylene glycol, propylene glycol, ethoxypropanol, butyl ethylene glycol (butyl cellosolve), dipropylene glycol dimethyl ether, dipropylene glycol monomethyl ether, ethylene glycol dimethyl ether, butyl ethylene glycol acetate, butyl diglycol acetate, methoxypropyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, N-methylpyrrolidone, xylene, etc.

[0079] According to some embodiments, the free radical polymerization reaction of the comonomer in the organic solvent can be achieved by heating a solution including the comonomer, the free radical initiator, and the organic solvent. Examples of the free radical initiator can be, but are not limited to, one or more of di-tert-butyl peroxide, dicumyl peroxide, benzoyl peroxide, cumene hydroperoxide, tert-butyl hydroperoxide, tert-butyl perbenzoate, tert-butyl per-2-ethylhexanoate, cyclohexanone peroxide, methyl isobutyl ketone peroxide, azobisisobutyronitrile.

[0080] Anodic electrophoretic paint

[0081] The present application also provides an anodic electrophoretic paint, including a silane coupling agent and a coating composition, wherein the coating composition includes an acrylic copolymer and a crosslinking agent, the acrylic copolymer includes structural units derived from (meth)acrylic monomers, and the structural units derived from (meth)acrylic monomers include at least one structural unit represented by formula (I), at least one structural unit represented by formula (II), and at least one structural unit represented by formula (III).

[0082]

[0083] Wherein, in formula (I), formula (II), and formula (III), R1, R2, and R3 are each independently H or methyl;

[0084] In formula (II), R4 is a substituted or unsubstituted C1-C10 alkyl group, and the substitution means being substituted by one or more substituents selected from nitro, cyano, halogen atom, ester group, amide group, C1-C10 alkyl group, C1-C10 alkoxy group, 6- to 10-membered aryl group;

[0085] In formula (III), R5 is a substituted C1-C10 alkyl group, and the substitution means being substituted by one or more substituents selected from hydroxyl, nitro, cyano, halogen atom, ester group, amide group, C1-C10 alkyl group, C1-C10 alkoxy group, 6- to 10-membered aryl group, and the substituent includes at least hydroxyl;

[0086] The molar proportion of the structural unit represented by the formula (I) is 14% to 22% relative to the total molar number of the structural units of the acrylic copolymer;

[0087] The molar proportion of the structural unit represented by the formula (III) is 2% to 5% relative to the total molar number of the structural units of the acrylic copolymer;

[0088] Relative to the total molar number of the structural units represented by the formula (I), the formula (II), and the formula (III) in the structural units of the acrylic copolymer, the molar ratio of the structural unit with R1, R2, and R3 being methyl to the structural unit with R1, R2, and R3 being methyl and H being 1 is (0.7 to 1.3):1. Thus, in addition to at least having the same advantages as the above coatings, by adding a silane coupling agent, it is also beneficial for the anodic electrophoretic paint to adhere uniformly to the metal surface. Exemplarily, the silane coupling agent is selected from aminopropyltrialkoxysilane and / or γ-glycidoxypropyltrialkoxysilane. The anodic electrophoretic paint may further comprise conventional paint additives, for example, fillers, thickeners, leveling agents, light stabilizers, etc.

[0089] According to some embodiments, the mass percentage of the acrylic copolymer is 7% to 10% relative to the mass of the electrophoretic paint, and the mass percentage of the silane coupling agent is 0.2% to 0.6%. Thereby, it is more beneficial to ensure the quality of the paint film.

[0090] According to some embodiments, the pH of the anodic electrophoretic paint is 8 to 10. For example, it can be adjusted by using an organic amine, such as triethylamine. Thereby, it is more beneficial to maintain the stability and curing effect of the electrophoretic paint.

[0091] Electronic device

[0092] The present application also provides an electronic device, comprising a main body and a housing for accommodating the main body, the main body comprising electronic components, the housing comprising a metal appearance structural member, the metal appearance structural member comprising a paint film and a substrate, the substrate being made of a metal material, on at least one surface of the substrate, the paint film being a paint film formed by depositing an anodic electrophoretic paint on the surface and baking and curing, wherein the anodic electrophoretic paint comprises a silane coupling agent and a paint composition, the paint composition comprising an acrylic copolymer and a crosslinking agent, the acrylic copolymer comprising structural units derived from (meth)acrylic monomers, the structural units derived from (meth)acrylic monomers comprising at least one structural unit represented by the formula (I), at least one structural unit represented by the formula (II), and at least one structural unit represented by the formula (III),

[0093]

[0094] Among them, in formula (I), formula (II) and formula (III), R1, R2 and R3 are each independently H or methyl;

[0095] In formula (II), R4 is a substituted or unsubstituted C1-C10 alkyl group, and the substitution means being substituted by one or more substituents selected from nitro, cyano, halogen atom, ester group, amide group, C1-C10 alkyl group, C1-C10 alkoxy group, 6- to 10-membered aryl group;

[0096] In formula (III), R5 is a substituted C1-C10 alkyl group, and the substitution means being substituted by one or more substituents selected from hydroxyl, nitro, cyano, halogen atom, ester group, amide group, C1-C10 alkyl group, C1-C10 alkoxy group, 6- to 10-membered aryl group, and the substituent at least includes hydroxyl;

[0097] Relative to the total molar number of the structural units of the acrylic copolymer, the molar proportion of the structural unit represented by formula (I) is 14% - 22%;

[0098] Relative to the total molar number of the structural units of the acrylic copolymer, the molar proportion of the structural unit represented by formula (III) is 2% - 5%;

[0099] Relative to the total molar number of the structural units represented by formula (I), formula (II) and formula (III) in the structural units of the acrylic copolymer, the molar ratio of the structural unit in which R1, R2 and R3 are methyl to the structural unit in which R1, R2 and R3 are H is (0.7 - 1.3):1. As described above, the paint film formed by the coating composition on the metal surface has good performance in terms of hardness, adhesion and abrasion resistance, which is beneficial to increasing the service life of the electronic device.

[0100] According to an embodiment of the present application, the target area of the metal appearance structure member includes a sealing substance, and the sealing substance is used to seal the target area of the substrate, and the sealing substance includes a corrosion inhibitor

[0101] The present application does not particularly limit the electronic device, and it can be a computer, a mobile phone, a tablet, etc. The present application does not particularly limit the shape of the electronic device, provided that the housing of the electronic device satisfies a predetermined shape that matches the main body, and the predetermined shape can accommodate the main body. Exemplarily, in an embodiment of the present application, the electronic device is rectangular, and a schematic diagram of a cross-section along a symmetry axis thereof can be seen Figure 1 , and the electronic device includes a main body 101 and a housing 102.

[0102] The main body 101 of the present application may include electronic devices, and there is no particular limitation on the electronic devices, which may include one or more of a central processing unit, a graphics processing unit, a display screen, a hard disk, and other electronic devices.

[0103] The housing 102 of the present application may include a metal appearance structural member composed of a paint film 1022 and a substrate 1021 having the shape of the housing, and the substrate 1021 is made of a metal material. Exemplarily, the metal material may be stainless steel, aluminum alloy, magnesium alloy, etc.

[0104] According to some embodiments, the metal material of the substrate 1021 may be magnesium alloy. Magnesium alloy itself has advantages such as relatively high strength, good thermal conductivity, and good shielding effect on electromagnetic interference. On this basis, the paint film on the surface of the magnesium alloy housing of the present application may have excellent hardness, adhesion, wear resistance, and a bright appearance. Exemplarily, the model of the magnesium alloy may be AZ31B, AZ91D, or AW70M, etc.

[0105] The paint film 1022 may be on all surfaces of the substrate 1021, and the paint film may be a paint film formed by depositing an anodic electrophoretic paint on the surface through an anodic electrophoretic process and baking and curing.

[0106] The present application has no special limitation on the anodic electrophoretic process and baking and curing, and those skilled in the art can select appropriate conditions according to the specific thickness of the paint film. Exemplarily, the substrate may be used as the anode of the electrophoretic tank, and titanium, stainless steel, or graphite, etc. may be used as the cathode. The anodic electrophoretic paint of the present application is added to the electrophoretic tank. For a paint film with a thickness of 20 μm to 30 μm, the solid mass content of the electrophoretic paint may be set to 10% to 15%, the voltage may be 40 V to 70 V, and electrophoretic coating may be carried out for 30 seconds to 60 seconds to coat the anodic electrophoretic paint on the surface of the substrate, and then baking and curing may be carried out at 160 °C to 180 °C to form a paint film.

[0107] Optionally, referring to Figure 2 , the paint film 1022 may be on one surface of the substrate 1021. Exemplarily, it may be achieved through the following steps: other surfaces of the substrate 1021 except the surface with the paint film may be protected, such as spraying an insulating protective layer; the surface to be deposited with the anodic electrophoretic paint may be locally polished or machined by turning to expose the metal again; using the substrate with the exposed metal surface as the anode of the electrophoretic tank, the anodic electrophoretic paint may be coated on the exposed metal surface through the anodic electrophoretic process; removing the insulating protective layer on other surfaces; and baking and curing to form a paint film.

[0108] Optionally, referring to Figure 3, the housing 102 of the present application further includes other layers 1023 in addition to the paint film 1022. The present application has no special limitation on the other layers 1023. For example, it can be a coating film, a film, an oxide film, etc. The present application also has no special limitation on the process for forming the other layers 1023. Those skilled in the art can select appropriate process conditions according to the specific type of the other layers.

[0109] In an embodiment of the present application, the electronic device may include the housing provided in the above embodiment; the housing includes a metal appearance structural member; the target area of the metal appearance structural member may include a sealing substance, and the sealing substance can be used to seal the target area of the metal appearance structural member, and the sealing substance may include a corrosion inhibitor.

[0110] In this embodiment, a method for preparing a housing is also provided. Refer to Figure 4 As shown, the preparation method includes: S108, infiltrating the sealing substance into the target area of the substrate to seal the target area of the substrate; wherein, the sealing substance includes a corrosion inhibitor.

[0111] In a possible case, the target area of the substrate may be the micro-shrinkage holes of the substrate.

[0112] Optionally, the sealing substance may be an infiltrant, which can infiltrate into the micro-shrinkage holes of the substrate to seal the micro-shrinkage holes of the substrate.

[0113] The corrosion inhibitor can be an organic corrosion inhibitor, such as: benzotriazole (BTA), imidazoline derivatives, fatty amine compounds, thiol compounds, environmentally friendly organophosphorus compounds, etc.; or it can be an inorganic corrosion inhibitor, such as: molybdate system, rare earth metal salts (such as cerium salts), nano-silicates, zinc phosphate, layered double hydroxides (LDH), etc.

[0114] Vacuum infiltration can be a process of filling the infiltrant into the internal micro-porosity defects of die-castings through the action of vacuum and pressure, which can be used to seal the pores of die-castings and improve the surface quality. Among them, the die-casting can be a substrate formed by die-casting process.

[0115] The preparation method provided in this embodiment can seal the micro-shrinkage holes of the substrate by infiltrating the sealing substance into the target area of the substrate, and thus can effectively remove the micro-shrinkage holes existing on the high-gloss surface of the substrate, and can also improve the corrosion resistance of the substrate. As a result, the appearance of the electronic device made from the substrate through subsequent processes is flat, without defects such as pits and pinholes, and the overall corrosion resistance (such as salt spray resistance, boiling water resistance, high temperature and high humidity resistance, etc.) of the electronic device is significantly improved. At the same time, the surface finish, brightness, and gloss of the electronic device can be improved.

[0116] In some embodiments, the sealing material may include: methacrylate monomer, hexanediol dimethacrylate, initiator, inhibitor, and surfactant.

[0117] In one possible case, the formulation of the infiltrant may include methacrylate monomer, hexanediol dimethacrylate, initiator, inhibitor, surfactant, and corrosion inhibitor.

[0118] The formulation of the infiltrant provided by the embodiments of the present application, compared with the traditional use of organic sealants such as silanes, can not only effectively seal the micro-pores of the substrate, but also improve the corrosion resistance of the substrate.

[0119] In some embodiments, the sealing material may include: methacrylate monomer, accounting for 25% - 35% of the weight of the sealing material; hexanediol dimethacrylate, accounting for 60% - 70% of the weight of the sealing material; initiator, accounting for 0.06% - 0.1% of the weight of the sealing material; inhibitor, accounting for 0.5% - 1% of the weight of the sealing material; surfactant, accounting for 1% - 2% of the weight of the sealing material; corrosion inhibitor, accounting for 1% - 2% of the weight of the sealing material.

[0120] The formulation of the infiltrant provided by the embodiments of the present application, compared with the traditional use of organic sealants such as silanes, can not only effectively seal the micro-pores of the substrate, but also improve the corrosion resistance of the substrate.

[0121] In some embodiments, the viscosity of the sealing material may be: not less than 5 mPa·S and not more than 15 mPa·S.

[0122] The formulation of the infiltrant provided by the embodiments of the present application, compared with the traditional use of organic sealants such as silanes, can not only effectively seal the micro-pores of the substrate, but also improve the corrosion resistance of the substrate.

[0123] In some embodiments, referring to Figure 5 As shown, infiltrating the sealing material into the target area of the substrate for sealing the target area of the substrate may include: S108a, performing a first vacuum treatment on the substrate having the target area to extract the gas in the target area of the substrate; and S108b, increasing the pressure and injecting the sealing material into the target area of the substrate for infiltration.

[0124] Exemplarily, taking the sealing material as an infiltrant as an example for illustration. In one possible case, the substrate can be placed in an infiltration tank, and then the substrate can be subjected to a first vacuum treatment to extract the gas in the micro-pores of the substrate. Then the substrate can be placed in the infiltrant in the infiltration tank, and the pressure is increased to inject the infiltrant into the micro-pores of the substrate to seal the micro-pores of the substrate (as shown in the left figure of Figure 7 )

[0125] In some embodiments, during the first vacuum pumping process, the degree of vacuum can be less than or equal to 10 mbar (millibar).

[0126] Optionally, the relevant data of the impregnation process according to the embodiments of the present application are shown in Table 1 below:

[0127] Table 1 Relevant data of the impregnation process

[0128]

[0129] As can be seen from Table 1, when the degree of vacuum is 10 mbar, the vacuum pumping time can be 20 and 30 minutes, the pressure can be 0.5 MPa, and the temperature in the impregnation tank can be 20 - 25 °C, the impregnation effect meets the requirements. By impregnating the impregnating agent into the microshrinkage pores of the substrate to seal the microshrinkage pores of the substrate, it is possible to effectively remove the microshrinkage pores existing on the high-gloss surface of the substrate, and moreover, it can also improve the corrosion resistance of the substrate.

[0130] In some embodiments, as shown in Figure 6 before impregnating the sealing substance into the target area of the substrate, it may include:

[0131] S101, after simultaneously performing die casting and the second vacuum pumping process on metal particles, performing computer numerical control machining to form a substrate with a target area;

[0132] S102, performing a grinding process on the substrate with the target area;

[0133] S103, performing a chemical conversion process on the substrate with the target area after the grinding process;

[0134] S104, performing a painting process on the substrate with the target area after the chemical conversion process;

[0135] S105, performing computer numerical control surface high-gloss treatment on the substrate with the target area after the painting process;

[0136] S106, performing a degreasing process on the substrate with the target area after the computer numerical control surface high-gloss treatment;

[0137] S107, performing a water washing process on the substrate with the target area after the degreasing process.

[0138] Optionally, the target area may refer to microshrinkage pores.

[0139] In step S101, during the die casting of metal particles, a vacuum pumping process can be simultaneously performed to extract the air in the mold cavity. Compared with the traditional die casting process that only performs die casting on metal particles without a vacuum pumping step, this embodiment can improve the density of die-cast workpieces and reduce the porosity.

[0140] Then, the substrate with microvoids can be polished to remove the mold release agent on the surface of the substrate.

[0141] Then, the substrate with microvoids after polishing can be subjected to chemical conversion treatment to increase the adhesion.

[0142] Then, the substrate with microvoids after chemical conversion treatment can be painted to improve the aesthetics of the substrate.

[0143] Then, the substrate with microvoids after painting can be subjected to computer numerical control (CNC) surface high-gloss treatment to further improve the aesthetics of the substrate.

[0144] Then, the substrate with microvoids after CNC surface high-gloss treatment can be degreased to remove the cutting oil used in CNC.

[0145] Then, the substrate with microvoids after degreasing can be washed with water.

[0146] In some embodiments, in the second vacuum pumping process, the vacuum degree can be less than 40 mbar.

[0147] In some embodiments, referring to Figure 6 as shown, after the sealing material is infiltrated into the target area of the substrate, it may include:

[0148] S109, the infiltrated substrate can be spin-dried;

[0149] S110, the spin-dried substrate can be washed with water;

[0150] S111, the substrate after washing with water can be heat-cured;

[0151] S112, the high-gloss surface of the substrate after heat-curing can be polished;

[0152] S113, the substrate after polishing can be dewaxed;

[0153] S114, the substrate after dewaxing can be phosphatized;

[0154] S115, the substrate after phosphatization can be subjected to transparent electrophoresis treatment to obtain the required metal appearance structural part.

[0155] In a possible case, the infiltrated substrate can be spin-dried first, and then the spin-dried substrate can be washed with water to wash off some non-infiltrated or excess infiltrant on the surface of the substrate.

[0156] Then, the substrate after the water washing treatment can be subjected to a thermal curing treatment to change the impregnating agent from a liquid to a solid, so as to seal the microscopic shrinkage pores of the substrate.

[0157] Then, the high-gloss surface of the substrate after the thermal curing treatment can be polished to remove water quality, water marks, etc. on the surface of the substrate, so as to improve the texture of the substrate (such as Figure 7 the middle figure in).

[0158] Then, the substrate after the polishing treatment can be subjected to a dewaxing treatment to remove the wax used in the polishing treatment.

[0159] Then, the substrate after the dewaxing treatment can be subjected to a ceramicizing treatment to increase the adhesion.

[0160] Then, the substrate after the ceramicizing treatment can be subjected to a transparent electrophoretic treatment to obtain the required metal appearance structural member. Further, the substrate after the ceramicizing treatment can be subjected to a colored transparent electrophoretic treatment to obtain the required metal appearance structural member (such as Figure 7 the right figure in). Figure 7 The left figure and the middle figure in both show a substrate, Figure 7 The right figure in shows four substrates arranged side by side after transparent electrophoresis. In this embodiment, a transparent polymer film is coated on the surface of the substrate through transparent electrophoresis, which can not only protect the substrate, but also well display the high-brightness state of the substrate, playing a very good decorative role.

[0161] In some embodiments, in the thermal curing treatment, the thermal curing parameters may include:

[0162] The thermal curing temperature is: not less than 110 °C and not more than 120 °C;

[0163] The thermal curing duration is: not less than 20 minutes and not more than 25 minutes;

[0164] The thermal curing shrinkage rate is: not less than 2% and not more than 4%.

[0165] In some embodiments, the metal particles may be magnesium alloy particles, and the substrate may be magnesium alloy.

[0166] Traditional aluminum alloy is heavier than magnesium alloy. The magnesium alloy appearance structural member made of magnesium alloy particles in this embodiment can achieve the effect of weight reduction, and it can be applied to different types of products, such as electronic devices such as laptops and mobile phones.

[0167] Embodiment

[0168] Hereinafter, embodiments of the present disclosure will be described. The embodiments described below are exemplary and are only used to explain the present disclosure, and should not be construed as a limitation of the present disclosure. For those not specifying specific technologies or conditions in the embodiments, the technologies or conditions described in the literature in this field or according to the product specifications are followed. For the reagents or instruments not indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0169] Example 1

[0170] Preparation of coating composition:

[0171] 60 parts of isopropanol and 8 parts of butyl cellosolve were added to a stainless steel reactor equipped with a temperature control device, a stirring paddle, and a condensation reflux system. The stirring device was started, and the stirring speed was set to 150 - 200 revolutions per minute; it was heated to reflux; by mass, 2 parts of hydroxyethyl methacrylate, 5 parts of acrylic acid, 4 parts of methacrylic acid, 25 parts of methyl methacrylate, 25 parts of ethyl acrylate, 8 parts of styrene, and 1 part of azobisisobutyronitrile were taken, and the above mixture was added dropwise under reflux and finished adding dropwise within 4 h, and then stirred for 1 h; then at the reflux temperature, 0.1 part of azobisisobutyronitrile was added every 0.5 h, after adding 3 times, stirred for 1 h again, and the polymerization was ended to obtain an acrylic copolymer solution, and the acid value was measured to be 50.5 mg KOH / g.

[0172] According to the methods for measuring the non-volatile content in HG / T 3334-2012 and GB / T 1725-2007, the solid mass content in the acrylic copolymer solution was measured to be 65%, that is, the mass content of the acrylic copolymer in the acrylic copolymer solution was 65%.

[0173] 100 parts of the above acrylic copolymer solution (corresponding to 65 parts of acrylic copolymer) was mixed with 40 parts of butanol etherified melamine formaldehyde resin solution (solid mass content of 65%, corresponding to 26 parts of butanol etherified melamine formaldehyde resin), heated and stirred at 80 °C for 5 h, and then adjusted to a solid mass content of 12% and a pH of 9 with triethylamine and water under stirring to obtain a coating composition, wherein the solid mass content of the acrylic copolymer was 8.6%. The "solid mass content of the coating composition" can also be measured according to the methods for measuring the non-volatile content in HG / T 3334-2012 and GB / T 1725-2007.

[0174] Preparation of anodic electrophoretic paint:

[0175] Take 100 parts of the coating composition, and slowly add 0.5 parts of 4,4'-dihydroxybenzophenone as a UV absorber, 0.3 parts of polyether modified silicone leveling agent, 0.5 parts of hydroxyethyl cellulose as a thickener, and 0.3 parts of silane coupling agent KH-550 at 50-60°C. Adjust the stirring speed to 200 rpm and stir for 90 minutes. After stirring, turn off the heating and stirring system and let it stand for 60 minutes to allow the tiny bubbles in the paint to escape naturally, reducing the bubble defects of the finished paint.

[0176] The paint liquid after standing is transported to the filtering equipment through a pipeline and filtered by a 300-mesh stainless steel filter to remove foreign particles in the paint liquid. The pressure of the filtration process is controlled at 0.2MPa-0.4MPa to ensure that the paint liquid passes through the filter screen smoothly and avoid excessive pressure to break through the filter screen or cause splashing loss of the paint liquid. Water is added to adjust the solid mass content to 10% to obtain an anodic electrophoretic paint, wherein the mass percentage of the acrylic copolymer is 8.4% and the mass percentage of the silane coupling agent is 0.3% relative to the mass of the electrophoretic paint.

[0177] Preparation of paint film on magnesium alloy surface:

[0178] The above-mentioned anodic electrophoretic paint was used as the bath liquid and added into the electrophoretic tank. A magnesium alloy plate (model AW70M, size 100×70×0.5mm) was used as the anode and stainless steel was used as the cathode. The voltage was set to 65V and the electrophoretic coating was performed for 45 seconds. After washing with water, the magnesium alloy was baked and cured at 165°C for 30 minutes to obtain a magnesium alloy with a paint film.

[0179] Examples 2 to 3 and Comparative Examples 1 to 6

[0180] Examples 2 to 3 and Comparative Examples 1 to 6 were prepared in the same manner as Example 1, wherein the solid mass content was 12%, and the only difference was that the amounts of hydroxyethyl methacrylate, acrylic acid, methacrylic acid, methyl methacrylate, ethyl acrylate, and styrene were adjusted as shown in Table 1. Electrophoretic paint was prepared in the same manner as Example 1, wherein the mass percentage of the acrylic copolymer was 8.4% and the mass percentage of the silane coupling agent was 0.3% relative to the mass of the electrophoretic paint. A paint film was prepared on the surface of a magnesium alloy in the same manner as Example 1.

[0181] Table 1

[0182]

[0183] Comparative Examples 7 to 9

[0184] Using clear water paint (ELECOAT W-2), Kansai paint (AG210), and Nippon paint (A100) as electrophoretic paint, a paint film was prepared on the surface of the magnesium alloy in the same manner as in Example 1.

[0185] For the paint films of the above-mentioned examples and comparative examples, hardness, adhesion, and RCA wear resistance performance tests were carried out with reference to ASTM D3363, ASTM D3359, and ASTM F2357. The paint film hardness of 3C electronic products is expected to reach above 2H, the adhesion reaches above 5B, and the RCA wear resistance reaches above 100 times.

[0186] In addition, in response to the requirements of 3C electronic products, tests for resistance to rubber friction, solvent abrasion resistance, sweat resistance, and high-temperature resistance were also carried out.

[0187] The test for resistance to rubber friction includes the following steps: At room temperature, use a friction machine (Shimadzu, Japan, rubber friction resistance machine) and EF74 rubber, with a force of 500 g / cm 2 force, at a distance of 6 cm and a speed of 1 round trip / second, rub the surface to be tested back and forth until a visual change is detected, and record the number of round trips as a measure of rubber friction resistance. The rubber friction resistance performance of 3C products is expected to reach above 1000 times.

[0188] The test for solvent abrasion resistance includes the following steps: At room temperature, use a friction machine (Taber 5750, USA) and 5 layers of pure cotton white gauze soaked in 95% ethanol (30×30 mm), with a force of 500 g / cm 2 force, at a distance of 6 cm and a speed of 1 round trip / second, rub the surface to be tested back and forth until a visual change is detected, and record the number of round trips as a measure of rubber friction resistance. The solvent abrasion resistance performance of 3C electronic products is expected to reach above 1000 times.

[0189] The test for sweat resistance includes the following steps: Prepare acidic artificial sweat by adding 1 kg of distilled water, 20 g / L of sodium chloride, 17.5 g / L of ammonium chloride, 5 g / L of urea, 2.5 g / L of acetic acid, 15 g / L of lactic acid, and adjusting the pH value to 4.7 with sodium hydroxide; prepare alkaline artificial sweat by adding 1 kg of distilled water, 10 g / L of sodium chloride, 4 g / L of ammonium carbonate, 2.5 g / L of sodium hydrogen phosphate, and adjusting the solution pH to 8.7; at room temperature, use 4 layers of absorbent cotton folded and a friction machine (Taber 5750, USA) soaked in the above two kinds of artificial sweat respectively, with a force of 500 g / cm 2 force, at a distance of 6 cm and a speed of 1 round trip / second, rub the surface to be tested back and forth until a visual change is detected, and record the number of round trips as a measure of rubber friction resistance. Reaching above 1000 times for both kinds of artificial sweat is considered qualified.

[0190] The high-temperature resistance test includes the following steps: Place the magnesium alloy with the paint film in a temperature and humidity conditioning chamber, maintain it at -40°C for 1 hour, then heat it from -40°C to 80°C within 2 hours with a humidity of 85%, maintain it for 1 hour, and then cool it to room temperature. This is 1 cycle. After 15 cycles in total, observe that the paint film is intact, the color is transparent and unchanged, and the adhesion test result is above 4B, which is considered qualified.

[0191] Perform the above performance tests on the paint films prepared on the magnesium alloy surfaces in the above Examples 1 to 3 and Comparative Examples 1 to 9, and the results are shown in Table 2.

[0192] Table 2

[0193]

[0194] According to the above results, it can be seen that by controlling the molar ratio of the hydroxy-containing (meth)acrylic acid monomers, the molar ratio of the carboxylic acid group-containing (meth)acrylic acid monomers, and the molar ratio of the structural units with R1, R2, and R3 being methyl to the structural units with R1, R2, and R3 being methyl within the scope of this application, the paint film hardness of Examples 1 to 3 all reaches above 2H, the adhesion all reaches above 5B, the RCA wear resistance all reaches above 100 times, the rubber friction resistance and solvent abrasion resistance all reach above 1000 times, and the sweat resistance and high-temperature resistance are all qualified. For the paint films of the 3 commercial anodic electrophoretic paints in Comparative Examples 7 to 8, although they are qualified in terms of adhesion, 2 of them are unqualified in terms of hardness, and the RCA wear resistance, rubber friction resistance, solvent abrasion resistance, sweat resistance, high-temperature resistance, etc. of all 3 are unqualified. In Comparative Example 1, the hydroxy content is increased too much, although it can make the adhesion qualified, but the wear resistance and hardness decrease instead. In Comparative Example 3, the carboxyl content is increased too much, although it can make the hardness qualified, but the wear resistance and adhesion decrease instead. In Comparative Example 5, the ratio of the methyl methacrylate monomer to the acrylic acid monomer is too low, and the paint film hardness, adhesion, and RCA wear resistance are all unqualified. However, in Comparative Example 6, too high a ratio leads to a decrease in the paint film adhesion and RCA wear resistance.

[0195] Example 4

[0196] Example 4 prepares the coating composition in the same method as Example 1, and the solid mass content of both is 12%. The only difference is that 2 parts of hydroxyethyl methacrylate are replaced with 2 parts of hydroxypropyl methacrylate. In the obtained acrylic copolymer, the molar ratio of the hydroxy-containing structural units is 2.0%, the molar ratio of the carboxylic acid group-containing structural units is 16.4%, and the molar ratio of the structural units with R1, R2, and R3 being methyl to the structural units with R1, R2, and R3 being methyl and H is 1:1. Then prepare the electrophoretic paint in the same method as Example 1.

[0197] Example 5

[0198] Example 5 The coating composition was prepared in the same manner as in Example 1, with a solid mass content of 12% in each case. The only difference was that methyl methacrylate was replaced with butyl methacrylate, and 4 parts of 2-hydroxyethyl methacrylate, 5 parts of acrylic acid, 5 parts of methacrylic acid, 30 parts of butyl methacrylate, 20 parts of ethyl acrylate, 8 parts of styrene, and 1 part of azobisisobutyronitrile were used. In the resulting acrylic copolymer, the molar proportion of the hydroxy-containing structural unit was 4.8%, the molar proportion of the carboxylic acid group-containing structural unit was 19.7%, and the molar ratio of the structural unit with R1, R2, and R3 being methyl to the structural unit with R1, R2, and R3 being methyl and H being 1.1:1. Then, the electrophoretic paint was prepared in the same manner as in Example 1.

[0199] Example 6

[0200] Example 6 The coating composition was prepared in the same manner as in Example 1, with a solid mass content of 12% in each case. The only difference was that methyl methacrylate was replaced with trifluoroethyl methacrylate, and 3 parts of 2-hydroxyethyl methacrylate, 4.5 parts of acrylic acid, 4 parts of methacrylic acid, 30 parts of trifluoroethyl methacrylate, 15 parts of ethyl acrylate, 8 parts of styrene, and 1 part of azobisisobutyronitrile were used. In the resulting acrylic copolymer, the molar proportion of the hydroxy-containing structural unit was 4.3%, the molar proportion of the carboxylic acid group-containing structural unit was 20.3%, and the molar ratio of the structural unit with R1, R2, and R3 being methyl to the structural unit with R1, R2, and R3 being methyl and H being 1.2:1. Then, the electrophoretic paint was prepared in the same manner as in Example 1.

[0201] Example 7

[0202] Example 7 The coating composition was prepared in the same manner as in Example 1, with a solid mass content of 12% in each case. The only difference was that methyl methacrylate was replaced with benzyl methacrylate, and 3.5 parts of 2-hydroxyethyl methacrylate, 3.5 parts of acrylic acid, 6 parts of methacrylic acid, 40 parts of benzyl methacrylate, 25 parts of ethyl acrylate, 8 parts of styrene, and 1 part of azobisisobutyronitrile were used. In the resulting acrylic copolymer, the molar proportion of the hydroxy-containing structural unit was 3.8%, the molar proportion of the carboxylic acid group-containing structural unit was 16.9%, and the molar ratio of the structural unit with R1, R2, and R3 being methyl to the structural unit with R1, R2, and R3 being methyl and H being 1.1:1. Then, the electrophoretic paint was prepared in the same manner as in Example 1.

[0203] For the paint films on the magnesium alloy surface prepared in Examples 4 to 7 above, hardness, adhesion, RCA abrasion resistance, rubber friction resistance, solvent abrasion resistance, sweat resistance, and high-temperature resistance tests were carried out, and the results are shown in Table 2.

[0204] Table 3

[0205]

[0206] According to the above results, by controlling the molar proportion of the hydroxy group-containing (meth)acrylic monomer, the molar proportion of the carboxyl group-containing (meth)acrylic monomer, and the molar ratio of the structural unit with R1, R2, and R3 being methyl to the structural unit with R1, R2, and R3 being methyl within the scope of this application, the film hardness of Examples 4 to 7 all reaches above 2H, the adhesion all reaches above 5B, the RCA wear resistance all reaches above 100 times, the rubber friction resistance and solvent abrasion resistance both reach above 1000 times, and the sweat resistance and high temperature resistance are both qualified. In Example 5, butyl methacrylate with a larger molecular weight is used to replace methyl methacrylate, further significantly improving the RCA wear resistance of the film. In Example 7, benzyl methacrylate with an aryl group is used to replace methyl methacrylate, further significantly improving the solvent abrasion resistance of the film. In Example 6, hydrophobic trifluoroethyl methacrylate is used to replace methyl methacrylate, improving all three types of wear resistance.

[0207] The above are only some specific embodiments of the present disclosure, intended to illustrate the present disclosure and not to limit the scope of protection required by this application. All modifications, substitutions, or direct / indirect applications in other related technical fields made under the inventive concept of the present disclosure are included within the scope of protection required by this application.

Claims

1. A coating composition comprising an acrylic copolymer and a crosslinking agent, wherein the acrylic copolymer comprises structural units derived from (meth)acrylic monomers, and the structural units derived from (meth)acrylic monomers comprise at least one structural unit represented by formula (I), at least one structural unit represented by formula (II), and at least one structural unit represented by formula (III). Among them, In formula (I), formula (II) and formula (III), R1, R2 and R3 are each independently H or methyl. In formula (II), R4 is a substituted or unsubstituted C1-C10 alkyl group, and the substitution means being substituted by one or more substituents selected from a nitro group, a cyano group, a halogen atom, an ester group, an amide group, a C1-C10 alkyl group, a C1-C10 alkoxy group, and a 6- to 10-membered aryl group. In formula (III), R5 is a substituted C1-C10 alkyl group, and the substitution means being substituted by one or more substituents selected from a hydroxyl group, a nitro group, a cyano group, a halogen atom, an ester group, an amide group, a C1-C10 alkyl group, a C1-C10 alkoxy group, and a 6- to 10-membered aryl group, and the substituent at least includes a hydroxyl group. Relative to the total molar number of the structural units of the acrylic copolymer, the molar proportion of the structural unit represented by formula (I) is 14% to 22%. Relative to the total molar number of the structural units of the acrylic copolymer, the molar proportion of the structural unit represented by formula (III) is 2% to 5%. Relative to the total molar number of the structural units represented by formula (I), formula (II) and formula (III) in the structural units of the acrylic copolymer, the molar ratio of the structural unit in which R1, R2 and R3 are methyl to the structural unit in which R1, R2 and R3 are H is (0.7 to 1.3):

1.

2. The coating composition according to claim 1, wherein, In formula (II), R4 is a substituted or unsubstituted C1-C10 alkyl group; in formula (III), R5 is a substituted C1-C10 alkyl group, and the substituent is a hydroxyl group.

3. The coating composition according to claim 1, wherein, Relative to the total molar number of the structural units of the acrylic copolymer, the molar proportion of the structural units derived from (meth)acrylic monomers is 80% to 90%.

4. The coating composition according to claim 1, wherein In the coating composition, the mass ratio of the acrylic copolymer to the crosslinking agent is 100:(20 to 60).

5. The coating composition according to claim 1, wherein, The crosslinking agent is an etherified melamine formaldehyde resin.

6. A method for preparing the coating composition according to any one of claims 1 to 5, comprising: Carrying out a radical polymerization reaction on copolymerizable monomers in an organic solvent to obtain a solution of an acrylic copolymer, wherein the copolymerizable monomers comprise the (meth)acrylic monomers; and Mixing the solution of the acrylic copolymer and the crosslinking agent to obtain the coating composition.

7. An anodic electrophoretic paint, wherein, The anodic electrophoretic paint comprises a silane coupling agent and a coating composition. Among them, the coating composition comprises an acrylic copolymer and a crosslinking agent. The acrylic copolymer comprises structural units derived from (meth)acrylic monomers. The structural units derived from (meth)acrylic monomers comprise at least one structural unit represented by formula (I), at least one structural unit represented by formula (II), and at least one structural unit represented by formula (III). Wherein, in formula (I), formula (II) and formula (III), R1, R2 and R3 are each independently H or methyl; In formula (II), R4 is a substituted or unsubstituted C1-C10 alkyl group, and the substitution means being substituted by one or more substituents selected from nitro, cyano, halogen atom, ester group, amide group, C1-C10 alkyl group, C1-C10 alkoxy group, 6- to 10-membered aryl group; In formula (III), R5 is a substituted C1-C10 alkyl group, and the substitution means being substituted by one or more substituents selected from hydroxyl, nitro, cyano, halogen atom, ester group, amide group, C1-C10 alkyl group, C1-C10 alkoxy group, 6- to 10-membered aryl group, and the substituents at least include hydroxyl; Relative to the total molar amount of the structural units of the acrylic copolymer, the molar proportion of the structural unit represented by formula (I) is 14% to 22%; Relative to the total molar amount of the structural units of the acrylic copolymer, the molar proportion of the structural unit represented by formula (III) is 2% to 5%; Relative to the total molar amount of the structural units represented by formula (I), formula (II) and formula (III) in the structural units of the acrylic copolymer, the molar ratio of the structural unit with R1, R2 and R3 being methyl to the structural unit with R1, R2 and R3 being H is (0.7 to 1.3):

1.

8. The anodic electrophoretic paint according to claim 8, wherein, Relative to the mass of the electrophoretic paint, the mass percentage of the acrylic copolymer is 7% to 10%, and the mass percentage of the silane coupling agent is 0.2% to 0.6%.

9. An electronic device includes a main body and a housing for accommodating the main body. The main body includes electronic components, and the housing includes a metal appearance structural member. The metal appearance structural member includes a paint film and a base material. The base material is made of a metal material, and the paint film is on at least one surface of the base material. Among them, The paint film is formed by depositing the anodic electrophoretic paint on the surface through an anodic electrophoresis process and baking and curing. Among them, the anodic electrophoretic paint comprises a silane coupling agent and a coating composition. The coating composition comprises an acrylic copolymer and a crosslinking agent. The acrylic copolymer comprises structural units derived from (meth)acrylic monomers. The structural units derived from (meth)acrylic monomers comprise at least one structural unit represented by formula (I), at least one structural unit represented by formula (II), and at least one structural unit represented by formula (III). Wherein, in formula (I), formula (II) and formula (III), R1, R2 and R3 are each independently H or methyl; In formula (II), R4 is a substituted or unsubstituted C1-C10 alkyl group, and the substitution means being substituted by one or more substituents selected from nitro, cyano, halogen atom, ester group, amide group, C1-C10 alkyl group, C1-C10 alkoxy group, 6- to 10-membered aryl group; In formula (III), R5 is a substituted C1-C10 alkyl group, and the substitution means being substituted by one or more substituents selected from a hydroxyl group, a nitro group, a cyano group, a halogen atom, an ester group, an amide group, a C1-C10 alkyl group, a C1-C10 alkoxy group, and a 6- to 10-membered aryl group, and the substituents include at least a hydroxyl group; With respect to the total molar number of the structural units of the acrylic copolymer, the molar proportion of the structural unit represented by formula (I) is 14% to 22%; With respect to the total molar number of the structural units of the acrylic copolymer, the molar proportion of the structural unit represented by formula (III) is 2% to 5%; With respect to the total molar number of the structural units represented by formula (I), formula (II), and formula (III) in the structural units of the acrylic copolymer, the molar ratio of the structural unit in which R1, R2, and R3 are methyl groups to the structural unit in which R1, R2, and R3 are methyl groups and H is (0.7 to 1.3):

1.

10. The electronic device according to claim 9, wherein, The target area of the metal appearance structural member includes a sealing substance for sealing the target area of the substrate, and the sealing substance includes a corrosion inhibitor.

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