Electrosilvering imitation coating and preparation method thereof

Abstract

The invention relates to the technical field of functional coatings, and provides an electrosilvering imitation coating and a preparation method thereof. In the components of the coating, the mass ratio of the film-forming substance to the organic solvent to the aluminum paste to the auxiliary agent is (20-30): (50-60): (12-18): (1-10). The film-forming substance is polyvinyl butylimidazole hexafluorophosphate grafted modified cellulose acetate butyrate, and the preparation method comprises the following steps: firstly preparing polyvinyl butylimidazole grafted modified cellulose acetate butyrate, then compounding with bromobutane, and then carrying out anion replacement with potassium hexafluorophosphate. By adopting the film-forming substances, the glossiness, distinctness of image and solvent resistance of the coating are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of functional coatings, and provides an imitation electroplated silver coating and a preparation method thereof. Background Art

[0002] The imitation electroplated silver coating is a functional coating that uses polymer resin as a film-forming substance, aluminum powder flakes as pigments, and adds various additives to simulate the mirror effect of metal electroplating. It is widely used in the fields of automobiles, home appliances and electronic products, handicrafts and packaging, and architectural decoration. Its cost is lower than the electroplating process, and it can realize the coating construction of complex curved substrates.

[0003] In the imitation electroplated silver coating, the aluminum powder particles are flaky, and the aspect ratio ranges from 40 - 100:1. During the flow and film-forming process, the aluminum powder tends to be arranged parallel to the substrate, and the aluminum powders are connected to each other to form a continuous metal film layer, which can not only cover the surface of the substrate, but also reflect external light (visible light, ultraviolet light and infrared light), making the surface of the coated object appear silver-white and bright.

[0004] Generally, the aluminum powder paint uses acrylic resin, epoxy resin, etc. as film-forming substances, and cellulose acetate butyrate as an additive to assist the directional arrangement of aluminum powder. In the imitation electroplated silver coating, high molecular weight cellulose acetate butyrate can be used as the main film-forming substance, which is not only beneficial to the orientation of aluminum powder, but also can improve the adhesion between the coating and the substrate, the ultraviolet resistance and yellowing resistance of the coating.

[0005] For the imitation electroplated silver coating using cellulose acetate butyrate as the film-forming substance, there is still room for improvement in the metallic feeling (glossiness) and mirror effect (distinctness of image) of the coating. Moreover, the solvent resistance of the coating is poor, which to a certain extent limits its application. By modifying to obtain an imitation electroplated silver coating with better glossiness, distinctness of image and solvent resistance, its application range can be expanded and its application effect can be improved. Summary of the Invention

[0006] In view of the above situation, the present invention proposes an imitation electroplated silver coating and a preparation method thereof to improve the glossiness, distinctness of image and solvent resistance of the coating.

[0007] To achieve the above object, the specific technical solutions involved in the present invention are as follows: First of all, the present invention provides an imitation electroplated silver coating, and its components include a film-forming substance, an organic solvent, aluminum silver paste, and additives. Preferably, in the imitation electroplated silver coating, the mass ratio of the film-forming substance, the organic solvent, the aluminum silver paste, and the additives is 20 - 30:50 - 60:12 - 18:1 - 10.

[0008] The film-forming substance is polyvinyl butyl imidazole hexafluorophosphate graft-modified cellulose acetate butyrate.

[0009] Preferably, the preparation process of the polyvinyl butyl imidazole hexafluorophosphate grafted modified cellulose acetate butyrate is: (1) Add cellulose acetate butyrate and benzoyl peroxide to a mixed solvent of ethyl acetate / ethylene glycol butyl ether, stir and heat until completely dissolved, then dropwise add 1-vinylimidazole, reflux at 85-100°C for 5-7h, cool and filter, then add acetone to swell, purify with cyclohexane in a Soxhlet extractor, and vacuum dry to obtain polyvinyl imidazole-grafted modified cellulose acetate butyrate; (2) Add the product of step (1) to dimethylformamide and 2 Under protection, butyl bromide is added dropwise, refluxed at 60-80°C for 20-30h, cooled and filtered, washed with deionized water and chloroform in turn, and vacuum dried to obtain polyvinyl butyl imidazole bromide grafted modified cellulose acetate butyrate; (3) Add the product of step (2) to dimethylformamide and 2 Under protection, add a deionized aqueous solution of potassium hexafluorophosphate dropwise, reflux at 50-60°C for 12-18h, cool and filter, wash with deionized water, and dry in vacuo.

[0010] Step (1) is a process of grafting cellulose acetate butyrate with 1-vinylimidazole. First, benzoyl peroxide is decomposed into active free radicals by heat, which capture the active hydrogen atoms on the hydroxyl groups in the cellulose acetate butyrate structure to form primary free radicals. The primary free radicals then add to the 1-vinylimidazole monomer to obtain monomer free radicals. The monomer free radicals continue to react with other monomers to achieve chain growth, thereby forming polyvinyl imidazole grafted chains on the structure of cellulose acetate butyrate. Preferably, in step (1), the mass ratio of cellulose acetate butyrate, benzoyl peroxide, ethyl acetate, ethylene glycol butyl ether, and 1-vinylimidazole is 12-15:0.1-0.2:8-12:4-6:6-8.

[0011] Step (2) is a process in which butyl bromide forms a compound with the imidazole ring on the grafted chain of cellulose acetate butyrate. Preferably, in step (2), the mass ratio of polyvinyl imidazole grafted modified cellulose acetate butyrate, dimethylformamide, and butyl bromide is 2:80-100:1-1.2.

[0012] Step (3) is a process in which potassium hexafluorophosphate and imidazolium bromide on the grafted chain of cellulose acetate butyrate are subjected to anion replacement, so that the imidazolium bromide is converted into imidazolium hexafluorophosphate. Preferably, in step (3), the mass ratio of polyvinyl butyl imidazolium bromide grafted modified cellulose acetate butyrate, dimethylformamide, potassium hexafluorophosphate, and deionized water is 2:80-90:0.9-1.1:10-15.

[0013] It is well-known that for imitation electroplated coatings, metallic feeling and mirror effect are important aspects to measure their appearance quality. In terms of metallic feeling, the higher the glossiness of the coating, the better the metallic feeling. The factors affecting glossiness are not only the aluminum flakes themselves (such as the size and surface condition of the aluminum powder), but also closely related to the orientation arrangement of the aluminum flakes. The lower the surface tension of the overall coating system, the easier it is for the aluminum flakes to be oriented during the coating process under the action of shear force, thus showing a higher glossiness. In terms of mirror effect, the higher the DOI (distinctness of image) grade of the coating, the better the mirror effect. Due to the small thickness and large diameter-thickness ratio of the aluminum flakes, they tend to agglomerate, and it is easy for the flakes to stack between each other. The agglomeration of aluminum flakes will cause a decrease in the DOI of the coating.

[0014] In the present invention, poly(vinylbutylimidazolium hexafluorophosphate) is used to graft-modify cellulose acetate butyrate. On the one hand, the original hydroxyl groups in the structure of cellulose acetate butyrate are reacted, and on the other hand, a hydrophobic ionic liquid chain structure is introduced (especially the F atoms can significantly reduce the surface tension). Both of these aspects can make the entire coating system have a lower surface tension, which is not only beneficial to the uniform dispersion of aluminum flakes, reducing the agglomeration phenomenon caused by surface tension differences, thereby improving the DOI, but also beneficial to the orientation arrangement of aluminum flakes under the action of shear force, thereby improving the glossiness. Moreover, poly(vinylbutylimidazolium hexafluorophosphate) forms graft side chains on the cellulose acetate butyrate molecular chain. The existence of the graft chains can form more and denser steric hindrance, further preventing the agglomeration of aluminum flakes and reducing the arrangement defects caused by agglomeration, thus further improving the glossiness and DOI.

[0015] In addition, the method of the present invention can also improve the solvent resistance of the coating (resistance to ethanol, acetone, etc.). This is because: firstly, through graft modification, the original hydroxyl groups in the structure of cellulose acetate butyrate are reacted and connected with polyhydrophobic ionic liquid molecular chains, reducing the affinity of the coating for solvents such as ethanol. Secondly, using the polyionic liquid graft-modified cellulose acetate butyrate of the present invention is beneficial to preventing the agglomeration of aluminum flakes and promoting orientation arrangement, thus forming a more perfect continuous metal film layer and improving the physical barrier effect of the coating against solvents.

[0016] Preferably, the organic solvent is composed of xylene, butyl acetate, and cyclohexanone in a mass ratio of 5:3:2, or composed of methyl isobutyl ketone and isopropanol in a mass ratio of 3:2, or composed of ethyl acetate and propylene glycol methyl ether acetate in a mass ratio of 1:1.

[0017] Preferably, the aluminum powder content of the aluminum silver paste is 60 - 80 wt%, the diameter of the aluminum flakes is 5 - 20 μm, and the thickness is 0.1 - 0.2 μm.

[0018] Preferably, the additives include but are not limited to one or more of a leveling agent, a dispersant, and an anti-settling stabilizer.

[0019] The present invention also provides a method for preparing the above imitation electroplated silver coating, specifically as follows: First, add the film-forming substance into an organic solvent, stir at 1000 - 1500 r / min for 5 - 20 min, then add aluminum silver paste and additives, and continue to stir for 10 - 20 min to obtain the product.

[0020] As can be seen from the above, the present invention provides an imitation electroplated silver coating and a method for preparing the same. Compared with the prior art, its prominent features and excellent effects are as follows: The present invention uses polyvinylbutylimidazolium hexafluorophosphate to graft-modify cellulose acetate butyrate, and uses this as the film-forming substance of the imitation electroplated silver coating. Through graft modification, not only the original hydroxyl groups on the structure of cellulose acetate butyrate are reacted, but also a polyhydrophobic ionic liquid molecular chain is grafted, making the entire coating system have a lower surface tension, and the grafted chain can form more and denser steric hindrance, thereby preventing the aggregation of aluminum powder flakes and promoting their oriented arrangement, making the coating have better gloss and distinctness of image. Moreover, this modification also improves the physical barrier effect of the coating to solvents, reduces the affinity of the coating to solvents, and makes the coating have better solvent resistance. Specific Embodiments

[0021] The following is a detailed description of the technical solution of the present invention, which does not constitute a limitation to the protection scope of the present invention. All substitutions or changes made according to ordinary technical knowledge and conventional means in the art shall be included in the scope of the present invention. Example 1

[0022] Prepare polyvinylbutylimidazolium hexafluorophosphate graft-modified cellulose acetate butyrate: (1) Add cellulose acetate butyrate and benzoyl peroxide into an ethyl acetate / ethylene glycol monobutyl ether mixed solvent, stir and heat until completely dissolved, then dropwise add 1-vinylimidazole, and reflux at 95°C for 6 h. Cool and filter, then add to acetone for swelling, purify with cyclohexane in a Soxhlet extractor, and vacuum dry to obtain polyvinylimidazole graft-modified cellulose acetate butyrate; (2) Add the product of step (1) into dimethylformamide, and dropwise add bromobutane under N 2 protection, reflux at 70°C for 25 h, cool and filter, wash successively with deionized water and chloroform, and vacuum dry to obtain polyvinylbutylimidazolium bromide graft-modified cellulose acetate butyrate; (3) Add the product of step (2) into dimethylformamide, and dropwise add an aqueous solution of potassium hexafluorophosphate in deionized water under N 2 protection, reflux at 55°C for 15 h, cool and filter, wash with deionized water, and vacuum dry to obtain the product.

[0023] The cellulose acetate butyrate is CAB-381-20, purchased from Shanghai Jiushi Chemical Co., Ltd.

[0024] In step (1), the mass ratio of cellulose acetate butyrate, benzoyl peroxide, ethyl acetate, ethylene glycol monobutyl ether, and 1-vinylimidazole is 14:0.15:10:5:6.

[0025] In step (2), the mass ratio of polyvinylimidazole-grafted cellulose acetate butyrate, dimethylformamide, and bromobutane is 2:90:1.

[0026] In step (3), the mass ratio of polyvinylbutylimidazolium bromide-grafted cellulose acetate butyrate, dimethylformamide, potassium hexafluorophosphate, and deionized water is 2:85:0.9:12.

[0027] To prepare the imitation electroplated silver coating: First, add the film-forming substance to the organic solvent and stir at 1200 r / min for 10 min. Then add the aluminum silver paste, leveling agent, and anti-settling stabilizer, and continue stirring for 15 min. The mass ratio of the film-forming substance, organic solvent, aluminum silver paste, leveling agent, and anti-settling stabilizer is 25:55:15:1:0.5.

[0028] The organic solvent is composed of xylene, butyl acetate, and cyclohexanone in a mass ratio of 5:3:2.

[0029] The aluminum powder content of the aluminum silver paste is 80 wt%, the diameter of the aluminum powder flakes is 10 ± 2 μm, and the average thickness is 0.15 μm.

[0030] The leveling agent is polyether-modified polydimethylsiloxane, purchased from Wuhan Kemike Biopharmaceutical Technology Co., Ltd.

[0031] The anti-settling stabilizer is fumed silica HDK T40, purchased from Shanghai Kayin Chemical Co., Ltd. Example 2

[0032] To prepare polyvinylbutylimidazolium hexafluorophosphate-grafted cellulose acetate butyrate: The preparation steps are the same as those in Example 1. The differences are: In step (1), the mass ratio of cellulose acetate butyrate, benzoyl peroxide, ethyl acetate, ethylene glycol monobutyl ether, and 1-vinylimidazole is 14:0.15:10:5:7.

[0033] In step (2), the mass ratio of polyvinylimidazole-grafted cellulose acetate butyrate, dimethylformamide, and bromobutane is 2:90:1.1.

[0034] In step (3), the mass ratio of polyvinylbutylimidazolium bromide-grafted cellulose acetate butyrate, dimethylformamide, potassium hexafluorophosphate, and deionized water is 2:85:1:12.

[0035] Preparation of imitation electroplated silver coating: First, add the film-forming substance into the organic solvent, stir at 1500 r / min for 6 min, then add aluminum silver paste, leveling agent and anti-settling stabilizer, and continue to stir for 12 min. The mass ratio of the film-forming substance, organic solvent, aluminum silver paste, leveling agent and anti-settling stabilizer is 25:55:15:1:0.5.

[0036] The organic solvent is composed of methyl isobutyl ketone and isopropyl alcohol in a mass ratio of 3:2.

[0037] The selection of cellulose acetate butyrate, aluminum silver paste, leveling agent and anti-settling stabilizer is the same as that in Example 1. Example 3

[0038] Preparation of polyvinyl butylimidazole hexafluorophosphate graft-modified cellulose acetate butyrate: The preparation steps are the same as those in Example 1. The differences are as follows: In step (1), the mass ratio of cellulose acetate butyrate, benzoyl peroxide, ethyl acetate, ethylene glycol monobutyl ether and 1-vinylimidazole is 14:0.15:10:5:8.

[0039] In step (2), the mass ratio of polyvinylimidazole graft-modified cellulose acetate butyrate, dimethylformamide and bromobutane is 2:90:1.2.

[0040] In step (3), the mass ratio of polyvinyl butylimidazole bromide graft-modified cellulose acetate butyrate, dimethylformamide, potassium hexafluorophosphate and deionized water is 2:85:1.1:12.

[0041] Preparation of imitation electroplated silver coating: First, add the film-forming substance into the organic solvent, stir at 1000 r / min for 18 min, then add aluminum silver paste, leveling agent and anti-settling stabilizer, and continue to stir for 18 min. The mass ratio of the film-forming substance, organic solvent, aluminum silver paste, leveling agent and anti-settling stabilizer is 25:55:15:1:0.5.

[0042] The organic solvent is composed of ethyl acetate and propylene glycol methyl ether acetate in a mass ratio of 1:1.

[0043] The selection of cellulose acetate butyrate, aluminum silver paste, leveling agent and anti-settling stabilizer is the same as that in Example 1. Comparative Example 1

[0044] Instead of preparing polyvinyl butylimidazolium hexafluorophosphate graft-modified cellulose acetate butyrate, a blend modification was carried out using an ionic liquid polymer (homopolymer), that is: directly adding cellulose acetate butyrate and polyvinyl butylimidazolium hexafluorophosphate to the coating components, and other conditions were the same as in Example 1. Among them, the preparation method of polyvinyl butylimidazolium hexafluorophosphate was: first, polyvinylimidazole was combined with bromobutane, and then an anion exchange was carried out with potassium hexafluorophosphate, referring to steps (2) and (3) in Example 1. Comparative Example 2

[0045] Instead of preparing polyvinyl butylimidazolium hexafluorophosphate graft-modified cellulose acetate butyrate, a blend modification was carried out using an unpolymerized ionic liquid, that is: directly adding cellulose acetate butyrate and 1-vinyl-3-butylimidazolium hexafluorophosphate to the coating components, and other conditions were the same as in Example 1.

[0046] Add the electroplated silver-like coatings prepared in the above examples and comparative examples into the spray gun cup, use an ABS plastic sheet as the substrate, spray evenly and dry in vacuum to form a 20-μm-thick coating. The following tests were carried out respectively: (1) Use a BGD512 single-angle gloss meter to measure the gloss of the paint film, the incident angle is 60°, the standard is a black glass plate with a polished refractive index of 1.567, and the calibration is 97 Gs; (2) Use a WGG60-BS digital gloss meter to measure the distinctness of image (DOI) value of the paint film; (3) Immerse a cotton gauze in ethanol for 10 minutes, take it out, hang it vertically for 5 minutes, and then repeatedly wipe the same position on the coating surface with the cotton gauze with a force of 5 N, and test the number of wipes required to wipe the position until it turns white.

[0047] The obtained data are shown in Table 1. It can be seen from Table 1 that: First, in the example, cellulose acetate butyrate was modified with polyvinyl butylimidazolium hexafluorophosphate, and the obtained coating had good gloss, distinctness of image and solvent resistance. And within the limited dosage range of the present invention, as the dosages of 1-vinylimidazole, bromobutane and potassium hexafluorophosphate increase, the gloss, distinctness of image and solvent resistance of the coating become better and better.

[0048] Second, the gloss, distinctness of image, and solvent resistance of the coating of Comparative Example 1 are all inferior to those of Example 1 because: in Comparative Example 1, the ionic liquid polymer was not grafted onto the cellulose acetate butyrate structure, but the ionic liquid homopolymer was directly added. The original hydroxyl groups on the cellulose acetate butyrate structure were not reacted, the surface tension of the coating system was higher than that of Example 1, and the affinity with ethanol solvent was stronger than that of Example 1. Moreover, the steric hindrance effect of the linear structure of the ionic liquid homopolymer was smaller than that of the grafted polymer structure. Therefore, compared with Example 1, Comparative Example 1 is not conducive to preventing the aggregation of aluminum flakes, the oriented arrangement of aluminum flakes, and the barrier to ethanol penetration, thus showing worse gloss, distinctness of image, and solvent resistance.

[0049] Third, the gloss, distinctness of image, and solvent resistance of the coating of Comparative Example 2 are all inferior to those of Comparative Example 1 because: like Comparative Example 1, Comparative Example 2 did not react the original hydroxyl groups on the cellulose acetate butyrate structure. Moreover, compared with Comparative Example 1, what was added in Comparative Example 2 was unpolymerized ionic liquid, which is a small molecule and does not even have the steric hindrance of the ionic liquid homopolymer in Comparative Example 1. Therefore, it is even less conducive to preventing the aggregation of aluminum flakes. The aggregated aluminum flakes will also cause arrangement defects, and ethanol can penetrate through the arrangement defects and the gaps between the aggregated particles, showing a further reduction in gloss, distinctness of image, and solvent resistance.

[0050] Table 1:

Claims

1. An electroplating silver-like paint, comprising a film-forming substance, an organic solvent, an aluminum-silver paste, and an additive, characterized in that: The film-forming substance is polyvinyl butyl imidazole hexafluorophosphate grafted modified cellulose acetate butyrate.

2. The electroplating silver-like paint according to claim 1, characterized in that: In the imitation electroplating silver paint, the mass ratio of the film-forming substance, the organic solvent, the aluminum silver paste and the auxiliary agent is 20-30:50-60:12-18:1-10.

3. The electroplating silver-like paint according to claim 1, characterized in that: The preparation process of the polyvinyl butyl imidazole hexafluorophosphate grafted modified cellulose acetate butyrate is as follows: (1) Add cellulose acetate butyrate and benzoyl peroxide to a mixed solvent of ethyl acetate / ethylene glycol butyl ether, stir and heat until completely dissolved, then dropwise add 1-vinylimidazole, reflux at 85-100°C for 5-7h, cool and filter, then add acetone to swell, purify with cyclohexane in a Soxhlet extractor, and vacuum dry to obtain polyvinyl imidazole-grafted modified cellulose acetate butyrate; (2) adding the product of step (1) into dimethylformamide, adding butyl bromide dropwise under N2 protection, reacting under reflux at 60-80°C for 20-30h, cooling and filtering, washing with deionized water and chloroform in turn, and vacuum drying to obtain polyvinyl butyl imidazole bromide grafted modified cellulose acetate butyrate; (3) Add the product of step (2) into dimethylformamide, add a deionized water solution of potassium hexafluorophosphate dropwise under N2 protection, reflux at 50-60°C for 12-18h, cool and filter, wash with deionized water, and dry in vacuo.

4. The imitation electroplating silver paint according to claim 3, characterized in that: In step (1), the mass ratio of cellulose acetate butyrate, benzoyl peroxide, ethyl acetate, ethylene glycol butyl ether, and 1-vinylimidazole is 12-15: 0.1-0.2：8-12：4-6：6-8。 5. The imitation electroplating silver paint according to claim 3, characterized in that: In step (2), the mass ratio of polyvinyl imidazole grafted modified cellulose acetate butyrate, dimethylformamide and butyl bromide is 2:80-100:1-1.

2.

6. The imitation electroplating silver paint according to claim 3, characterized in that: In step (3), the mass ratio of polyvinyl butyl imidazole bromide grafted modified cellulose acetate butyrate, dimethylformamide, potassium hexafluorophosphate, and deionized water is 2:80-90:0.9-1.1:10-15.

7. The electroplating silver-like paint according to claim 1, characterized in that: The organic solvent is composed of xylene, butyl acetate and cyclohexanone in a mass ratio of 5:3:2, or methyl isobutyl ketone and isopropanol in a mass ratio of 3:2, or ethyl acetate and propylene glycol methyl ether acetate in a mass ratio of 1:

1.

8. The electroplating silver-imitation paint according to claim 1, characterized in that: The aluminum powder flake content of the aluminum-silver paste is 60-80wt%, the diameter of the aluminum powder flake is 5-20μm, and the thickness is 0.1-0.2μm.

9. The imitation electroplating silver paint according to claim 1, characterized in that: The auxiliary agent is one or more of a leveling agent, a dispersant, and an anti-settling stabilizer.

10. The method for preparing the imitation electroplating silver coating according to any one of claims 1 to 9, characterized in that: The specific preparation method is: first add the film-forming substance into the organic solvent, stir at 1000-1500r / min for 5-20min, then add aluminum silver paste and additives, and continue stirring for 10-20min.

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