A high-gloss electroplated silver coating composition, an electroplated silver coating, and a method of making the same

Abstract

The application discloses a high-gloss electroplated silver coating composition, characterized in that the composition comprises, in percentage by weight, 1.8-2.2% of electroplated silver aluminum paste, 4.0-6.0% of electroplated silver resin, 0.04-0.06% of hydroxyl hyperbranched resin, 0.3-0.5% of blocked isocyanate resin, 0.03-0.05% of anti-silver dropping additive, 0.08-0.13% of additive, and 91.0-93.0% of solvent. The electroplated silver coating composition is used in combination with black primer and varnish, the 20° gloss of the composite coating is greater than 230, the gloss is much higher than the range value of 170-180 of the conventional electroplated silver coating composition, and the water resistance and recoating performance are qualified, and the electroplated silver coating composition can be used in combination with liquid varnish or powder varnish. The application further discloses an electroplated silver coating comprising the electroplated silver coating composition and a preparation method and application thereof.

Description

Technical Field

[0001] This invention relates to the technical field of automotive coatings. More specifically, it relates to a high-gloss electroplated silver coating composition, an electroplated silver coating, and a method for preparing the same. Background Technology

[0002] In recent years, with the rapid development of the automotive industry, the color and appearance of related automotive products such as wheels have also shown diversified demands, such as electroplated wheels and electroplated silver-coated wheels. Compared with automotive wheels coated with traditional paint, electroplated wheels and electroplated silver-coated wheels have high gloss and metallic texture, making them very popular with consumers. Among them, the gloss of electroplated wheels is higher than that of electroplated silver-coated wheels. There are two electroplating processes: water electroplating and vacuum electroplating. Water electroplating wheel processes have the disadvantage of generating wastewater that is difficult to treat and polluting the environment; vacuum electroplating wheel processes require baking the paint layer at a high temperature of 220-230℃, which can affect the mechanical strength of aluminum alloy wheels, thus limiting the large-scale application of electroplated wheels.

[0003] Therefore, it is necessary to provide a high-gloss electroplated silver coating composition and its preparation method, which can be used in conjunction with both liquid varnish and powder varnish. Summary of the Invention

[0004] The first objective of this invention is to provide a high-gloss electroplating silver coating composition. This electroplating silver coating composition, when used in conjunction with a black primer and clear coat, produces a composite coating with a 20° gloss > 230, which is significantly higher than the 170-180 range of conventional electroplating silver coating compositions. Furthermore, it exhibits satisfactory water resistance and recoating performance, and can be used with either liquid or powder clear coats.

[0005] The second objective of this invention is to provide a high-gloss electroplated silver coating.

[0006] The third objective of this invention is to provide a method for preparing a high-gloss electroplated silver coating.

[0007] The fourth objective of this invention is to provide an application of a high-gloss electroplated silver coating.

[0008] To achieve the first objective mentioned above, the present invention adopts the following technical solution:

[0009] A high-gloss electroplated silver coating composition, comprising, by weight percentage:

[0010]

[0011] Furthermore, the aluminum powder in the electroplating silver aluminum paste has a particle size of 8-14 μm, and the non-volatile content of the electroplating silver aluminum paste is 9.90-10.10%.

[0012] Furthermore, the electroplating silver resin has a non-volatile content of 7.5-8.5% and a Gardner viscosity of W-Z3.

[0013] Furthermore, the hydroxyl hyperbranched resin has a non-volatile content of 53.0-63.0%, a viscosity of 150-550 mPa.s at 25°C, and a hydroxyl content of 4.8-6.3% based on solid resin.

[0014] Furthermore, the non-volatile content of the terminated isocyanate resin is 73.0-77.0%, the deblocking temperature is 110-150℃, and the content of terminated isocyanate functional groups in the terminated isocyanate resin is 8%-12wt%.

[0015] Furthermore, the anti-silver-dropping additive is a low-acid modified polyester compound with a non-volatile content of 78.0-82.0%.

[0016] Furthermore, the additive is selected from one or more of the following: leveling agents, ultraviolet absorbers, light stabilizers, coupling agents, or wetting and dispersing agents.

[0017] Further, the additives comprise, by weight percentage of the total weight of the electroplating silver coating composition:

[0018]

[0019] Furthermore, the solvent is selected from one or more of ketone solvents, ester solvents, and aromatic solvents.

[0020] Furthermore, the ester solvent is selected from one or more of propylene glycol methyl ether acetate, ethyl 3-ethoxypropionate, butyl propionate, butyl acetate, and ethyl acetate, and the ester solvent accounts for 56.0-60.0% of the total weight of the electroplating silver coating composition.

[0021] Furthermore, the ketone solvent is selected from one or more of cyclohexanone, methylpentyl ketone, methyl isopentyl ketone and methyl isobutyl ketone, and the ketone solvent accounts for 16.0-20.0% of the total weight of the electroplating silver coating composition.

[0022] Furthermore, the aromatic solvent is selected from one or more of xylene, S-100#, and S-150#, and the aromatic solvent accounts for 14.0-18.0% of the total weight of the electroplating silver coating composition.

[0023] To achieve the second objective mentioned above, the present invention adopts the following technical solution:

[0024] A high-gloss electroplating silver coating, wherein the raw materials of the electroplating silver coating include the high-gloss electroplating silver coating composition as described in the first objective above.

[0025] To achieve the third objective mentioned above, the present invention adopts the following technical solution:

[0026] A method for preparing a high-gloss electroplated silver coating includes the following steps:

[0027] 1) Passivate the electroplated silver aluminum paste to obtain passivated electroplated silver aluminum paste;

[0028] 2) Dissolve the hydroxyl hyperbranched resin and the end-capped isocyanate resin in a portion of the solvent, mix well, and obtain a mixed resin semi-finished product;

[0029] 3) Mix the electroplating silver resin with the passivated electroplating silver aluminum paste, then mix it with the mixed resin semi-finished product, add the additives and the remaining solvent to obtain the high-gloss electroplating silver coating.

[0030] To achieve the fourth objective mentioned above, the present invention also protects the application of the high-gloss electroplated silver coating described in the second objective above in the coating of automobile wheel hubs.

[0031] The beneficial effects of this invention are as follows:

[0032] The high-gloss electroplating silver coating composition provided by this invention uses a specially selected electroplating silver resin as the directional resin for electroplating silver aluminum powder, and hydroxyl hyperbranched resin and end-capped isocyanate resin as crosslinking and curing resins, along with suitable additives. When used in a high-gloss electroplating silver coating, the resulting high-gloss electroplating silver coating composition, when used in conjunction with a black primer and clear coat, exhibits a 20° gloss level >230, significantly higher than the 170-180 range of conventional electroplating silver coating compositions. Furthermore, it demonstrates satisfactory water resistance and recoating performance, and can be used with either liquid or powder clear coats. The high-gloss electroplating silver coating provided by this invention is well-suited for application in the coating of automotive wheel hubs. Detailed Implementation

[0033] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments, further clarifies the invention. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive, and should not be construed as limiting the scope of protection of the present invention.

[0034] To overcome the problems of environmentally unfriendly processes and reduced wheel performance in existing electroplating processes for automobiles, one specific embodiment of the present invention provides a high-gloss electroplating silver coating composition, wherein, by weight percentage, the composition comprises:

[0035]

[0036] In this electroplating silver coating composition, a specially selected electroplating silver resin is used as the directional resin for electroplating silver aluminum powder, and hydroxyl hyperbranched resin and end-capped isocyanate resin are combined as crosslinking and curing resins. The addition amount of each component is controlled, and appropriate additives are added. When used in a high-gloss electroplating silver coating, the resulting high-gloss electroplating silver coating composition is used in conjunction with black primer and clear coat. The composite coating has a 20° gloss > 230, which is much higher than the 20° gloss range of 170-180 of conventional electroplating silver coating compositions. Moreover, it has good water resistance and recoating performance. It can be used in conjunction with liquid clear coat or powder clear coat and is suitable for wheel hub coating.

[0037] In one example, the aluminum powder particle size in the electroplating silver aluminum paste is 8-14 μm, and the non-volatile content of the electroplating silver aluminum paste is 9.90-10.10%. Electroplating silver aluminum pastes suitable for this embodiment include, but are not limited to, TS-408PM, purchased from Zhaoqing Dongyang, which has an aluminum powder particle size of 8 μm and a non-volatile content of 10.0%, or selected from... A-41014, purchased from ECKART, has an aluminum powder particle size of 14μm and a non-volatile content of 10.0%.

[0038] In one example, the electroplating silver resin has a non-volatile content of 7.5-8.5% and a Gardner viscosity of W-Z3. Electroplating silver resins suitable for this embodiment include, but are not limited to, those selected from AMORSO-789A (purchased from Huai'an Shangyan Chemical Co., Ltd.) with a non-volatile content of 8.5% and a Gardner viscosity of Y-Z3, or those selected from A-108 (purchased from Guangzhou Baiya Chemical Co., Ltd.) with a non-volatile content of 8% and a Gardner viscosity of WZ.

[0039] In this embodiment, the applicant discovered that the electroplating silver resin itself has almost no reactive groups. However, by blending it with a cross-linking curing resin, the coating film can be endowed with good interlayer adhesion, water resistance, and recoatability. But the type and amount of the cross-linking resin used in the blend can interfere with the arrangement of the electroplating silver aluminum powder, thereby reducing the gloss of the electroplating silver coating. Examples include conventional combinations of acrylic resin and amino resin, or polyester resin and amino resin. Therefore, selecting a cross-linking resin that minimizes interference with the arrangement of the electroplating silver aluminum powder and reducing its dosage while ensuring coating performance is crucial for designing high-gloss electroplating silver coating formulations. Through testing and verification, the applicant found that: the end-capped isocyanate resin interferes less with the arrangement of aluminum powder in electroplating silver than the acrylic or polyester resins commonly used in conventional electroplating silver coatings; the hydroxyl hyperbranched resin has the advantages of small molecular weight and a large number of reactive functional groups. The use of hydroxyl hyperbranched resin can ensure that a sufficient number of reactive groups are provided with a small amount of mixed resin. Moreover, the reaction between the end-capped isocyanate resin and the hydroxyl hyperbranched resin forms elastic urethane bonds, which balances the brittleness of the electroplating silver film caused by the polymer electroplating silver resin. This makes the electroplating silver coating have excellent flexibility, meets the requirements of recoatability of composite coatings, and is compatible with powder varnishes that require high-temperature baking and curing.

[0040] In this embodiment, the hydroxyl hyperbranched resin is a polyester polyol with a hyperbranched structure. In a preferred example, the hydroxyl hyperbranched resin has a non-volatile content of 53.0-63.0%, a viscosity of 150-550 mPa.s@25°C, and a hydroxyl content of 4.8-6.3% based on solid resin. Suitable hydroxyl hyperbranched resins for this invention include, but are not limited to, CYGLAZ BB 500, purchased from Nippon Paint (China) Co., Ltd., with a non-volatile content of 53.0-55.0%, a viscosity of 150-250 mPa.s@25°C, and a hydroxyl content of 6.3% based on solid resin; or CYGLAZ BB 600, also purchased from Nippon Paint (China) Co., Ltd., with a non-volatile content of 61.0-63.0%, a viscosity of 400-550 mPa.s@25°C, and a hydroxyl content of 6.3% based on solid resin.

[0041] In this scheme, the presence of end-capped isocyanates also effectively improves the recoating adhesion of electroplated silver coatings. In a preferred example, the end-capped isocyanate resin has a non-volatile content of 73.0-77.0%, a desealing temperature of 110-150°C, and an end-capped isocyanate functional group content of 8%-12 wt%. The end-capped isocyanate resin includes, but is not limited to, DESMODUR BL 3575SN (purchased from BAYER Corporation), with a non-volatile content of 73.0-77.0%, a desealing temperature of 112°C, and an end-capped isocyanate functional group content of 11.1 wt%, or TKA-B75S (purchased from Asahi Kasei Corporation), with a non-volatile content of 73.0-77.0%, a desealing temperature of 142°C, and an end-capped isocyanate functional group content of 11.2 wt%.

[0042] The presence of anti-silver-drop additives helps improve the recoating adhesion of electroplated silver coatings. In a preferred example, the anti-silver-drop additive is a low-acid modified polyester compound with a non-volatile content of 78.0-82%, such as anti-silver-drop additive 120, purchased from Shanghai Aofan Chemical Co., Ltd.

[0043] In a preferred example, the additive is selected from one or more of leveling agents, ultraviolet absorbers, light stabilizers, coupling agents, or wetting and dispersing agents.

[0044] Furthermore, the leveling agent is an acrylic leveling agent, including but not limited to DYNOADD F-1, purchased from DYNEA; the ultraviolet absorber is selected from TINUVIN-384-2, purchased from BASF, or from CHISORB5228, purchased from Debixi Chemical Trading (Shanghai) Co., Ltd.; the light stabilizer is selected from TINUVIN-292, purchased from BASF, or CHISORB532, purchased from Debixi Chemical Trading (Shanghai) Co., Ltd.; and the coupling agent is selected from SE 01-A2, purchased from Shingoku Chemical Co., Ltd.

[0045] Furthermore, the additives comprise, by weight percentage of the total weight of the high-gloss electroplated silver coating:

[0046]

[0047] In a preferred embodiment, the solvent is selected from one or more of ketone solvents, ester solvents, and aromatic solvents. Specifically, the ester solvent is selected from one or more of propylene glycol methyl ether acetate, ethyl 3-ethoxypropionate, butyl propionate, butyl acetate, and ethyl acetate, and the ester solvent accounts for 66.0-70.0% of the total weight of the electroplating silver coating composition; the ketone solvent is selected from one or more of cyclohexanone, methylpentyl ketone, methyl isopentyl ketone, and methyl isobutyl ketone, and the ketone solvent accounts for 16.0-20.0% of the total weight of the electroplating silver coating composition; the aromatic solvent is selected from one or more of xylene, S-100#, and S-150#, and the aromatic solvent accounts for 14.0-18.0% of the total weight of the electroplating silver coating composition.

[0048] Another specific embodiment of the present invention provides a high-gloss electroplating silver coating, wherein the raw materials of the electroplating silver coating include a high-gloss electroplating silver coating composition as described in the first specific embodiment above.

[0049] It is understandable that, because the raw materials include the electroplating silver coating composition described above, the electroplating silver coating also possesses the effects of the electroplating silver coating composition. That is, when used in conjunction with a black primer and clear coat, the composite coating exhibits a 20° gloss > 230, which is significantly higher than the 170-180 range of conventional electroplating silver coating compositions. Furthermore, it demonstrates satisfactory water resistance and recoating performance, and can be used with either liquid or powder clear coats, making it suitable for coating automotive wheel rims.

[0050] Another specific embodiment of the present invention provides a method for preparing the electroplated silver coating as described above, the method comprising the following steps:

[0051] 1) Passivate the electroplated silver aluminum paste to obtain passivated electroplated silver aluminum paste;

[0052] 2) Dissolve the hydroxyl hyperbranched resin and the end-capped isocyanate resin in a portion of the solvent, mix well, and obtain a mixed resin semi-finished product;

[0053] 3) Mix the electroplating silver resin with the passivated electroplating silver aluminum paste, then mix it with the mixed resin semi-finished product, add the additives and the remaining solvent to obtain the high-gloss electroplating silver coating.

[0054] In some examples, in step 1), a coupling agent is used to passivate the electroplated silver-aluminum paste. The passivated electroplated silver-aluminum paste, when used in the preparation of the electroplated silver coating, can give the electroplated silver coating better water resistance.

[0055] In some other examples, in step 3), the electroplating silver resin is first dispersed and dissolved in a ketone solvent, and then mixed with the passivated electroplating silver aluminum paste. In this case, the electroplating silver resin exhibits better miscibility with other resins, resulting in a coating with strong adhesion. In some preferred examples, the method for preparing the electroplating silver coating includes the following steps:

[0056] 1) Passivation of electroplated silver aluminum paste: Add the prescribed amount of electroplated silver aluminum paste and part of the ester solvent into container A, stir at 300-400 r / min, add the prescribed amount of coupling agent, stir for 10-15 min, then add the prescribed amount of anti-silver-dropping additive, continue stirring for 30-40 min, stop stirring, then take part of the ester solvent to rinse the aluminum paste on the stirring paddle and container wall, seal container A, and let stand for 4 h to passivate the aluminum paste for later use;

[0057] 2) Preparation of mixed resin semi-finished product: Add part of the ester solvent into container B, stir at 200-300 r / min, add the formulated amount of hydroxyl hyperbranched resin, and then take some more ester solvent to rinse the container wall and the agitator. Stir for 5-10 min, then add the formulated amount of end-capped isocyanate, increase the stirring speed to 400-500 r / min and continue stirring for 20-30 min, then stop stirring and set aside.

[0058] 3) In another container C, add the ketone solvent of the formula and stir at 200-300 r / min. Add the electroplating silver resin of the formula, increase the stirring speed to 400-500 r / min, stir for 5-10 min, add the electroplating silver aluminum paste from step 1, and rinse container A with the remaining ester solvent and add it together. Stir for 20-30 min.

[0059] 4) Add the mixed resin semi-finished product from step 2 to container C, and add it together after rinsing container B with some ester solvent. Stir for 10-20 minutes.

[0060] 5) Add the formulated amount of additives, remaining ester solvents and aromatic solvents to container C, and continue stirring for 30-40 minutes to obtain the high-gloss electroplating silver coating composition.

[0061] In the above preparation method, the high molecular weight electroplating silver resin using ketone solvents has good solubility. Dissolving and dispersing the electroplating silver resin with ketone solvents first can ensure good miscibility between the electroplating silver resin and the mixed crosslinked resin. Using some aromatic solvents can prevent the electroplating silver coating from biting the primer during wet-on-wet spraying with the black primer.

[0062] Another specific embodiment of the present invention provides the application of the high-gloss electroplated silver coating as described above in the coating of automobile wheel hubs.

[0063] Specifically, this high-gloss electroplated silver coating is used in the coating of automotive aluminum alloy wheels.

[0064] The technical solution of the present invention will be described below with reference to some specific embodiments:

[0065] raw material:

[0066] Electroplating silver aluminum paste TS-408PM, purchased from Zhaoqing Dongyang, or A-41014, purchased from ECKART;

[0067] Electroplating silver resin AMORSO-789A, purchased from Huai'an Shangyan Chemical Co., Ltd., or A-108, purchased from Guangzhou Baiya Chemical Co., Ltd.;

[0068] Hydroxyl hyperbranched resin CYGLAZ BB 500, purchased from Nippon Paint (China) Co., Ltd., or CYGLAZ BB600, also purchased from Nippon Paint (China) Co., Ltd.

[0069] The end-capped isocyanate resin DESMODUR BL 3575SN was purchased from BAYER Corporation, or TKA-B75S was purchased from Asahi Kasei Corporation.

[0070] Anti-silver-dropping additive 120, purchased from Shanghai Aofan Chemical Co., Ltd.

[0071] Acrylic leveling agent DYNOADD F-1, purchased from DYNEA Company;

[0072] Ultraviolet absorber TINUVIN-384-2, purchased from BASF, or CHISORB5228, purchased from Debbie Chemical Trading (Shanghai) Co., Ltd.

[0073] Light stabilizer TINUVIN-292, purchased from BASF, or CHISORB532, purchased from Debbie Chemical Trading (Shanghai) Co., Ltd.

[0074] Coupling agent SE 01-A2, purchased from Shin-Etsu Chemical Co., Ltd.

[0075] Example 1

[0076] A high-gloss electroplated silver coating, the raw material composition formula of which is shown in Table 1.

[0077] Table 1. Raw material weight parts for Example 1

[0078]

[0079]

[0080] The preparation of the high-gloss electroplated silver coating includes the following steps:

[0081] 1) Passivation of electroplated silver aluminum paste: Add 2 parts of electroplated silver aluminum paste and 10 parts of butyl acetate to container A, stir at 300-400 r / min, add 0.02 parts of coupling agent SE 01-A2, stir for 10-15 min, then add 0.04 parts of anti-silver-dropping additive 120, continue stirring for 30-40 min, stop stirring, then take 8.89 parts of butyl acetate solvent to rinse the aluminum paste on the stirring paddle and container wall, seal container A, and let stand for 4 h to passivate the aluminum paste for later use;

[0082] 2) Preparation of mixed resin semi-finished product: Add 5 parts of propylene glycol methyl ether acetate to container B, stir at 200-300 r / min, add 0.06 parts of hydroxyl hyperbranched resin CYGLAZ BB 500, and rinse the container wall and stirrer with 2 parts of propylene glycol methyl ether acetate. Stir for 5-10 min, then add 0.4 parts of end-capped isocyanate DESMODUR BL 3575SN, increase the stirring speed to 400-500 r / min and continue stirring for 20-30 min. Stop stirring and set aside.

[0083] 3) In another container C, add 18 parts of methyl isobutyl ketone and stir at 200-300 r / min. Add 5.0 parts of electroplating silver resin AMORSO-789A, increase the stirring speed to 400-500 r / min, stir for 5-10 min, add the electroplating silver aluminum paste from step 1, and add 10 parts of propylene glycol methyl ether acetate after rinsing container A. Stir for 20-30 min.

[0084] 4) Add the mixed resin semi-finished product from step 2 to container C, and add 10 parts of propylene glycol methyl ether acetate after rinsing container B. Stir for 10-20 minutes.

[0085] 5) Add the formulated amount of additives, the remaining 9 parts of propylene glycol methyl ether acetate, 3.5 parts of ethyl 3-ethoxypropionate and 16 parts of aromatic solvent S-100# to container C, and continue stirring for 30-40 minutes to obtain the high-gloss electroplating silver coating composition.

[0086] Comparative Example 1

[0087] Example 1 was repeated, except that the amount of commercially available hydroxyl acrylic resin AP 545 or other solids was used to replace the hydroxyl hyperbranched resin in Example 1, while the amounts of other materials remained unchanged.

[0088] Comparative Example 2

[0089] Example 1 was repeated, except that the end-capped isocyanate resin in Example 1 was replaced with commercially available amino resin BR 20SE and other solids, while the amounts of other materials remained unchanged.

[0090] Comparative Example 3

[0091] Example 1 was repeated, except that the solids of commercially available thermosetting acrylic resin TAR-3753-70 and amino resin BR20SE were used to replace the end-capped isocyanate resin DESMODUR BL 3575SN and hydroxyl hyperbranched resin CYGLAZ BB 500 in Example 1. The solid ratio of TAR-3753-70 to BR 20SE was 7:3, and the amounts of other materials remained unchanged.

[0092] Comparative Example 4

[0093] Example 1 was repeated, except that commercially available polyester resin SETAL173 VS 60 and amino resin BR 20SE were used to replace the capped isocyanate resin DESMODUR BL 3575SN and hydroxyl hyperbranched resin CYGLAZ BB 500 in Example 1. The solid ratio of SETAL173 VS 60 and BR 20SE was 7:3, and the amounts of other materials remained unchanged.

[0094] Comparative Example 5

[0095] Comparative Example 3 is a commercially available ordinary electroplating silver coating, which has an electroplating silver aluminum paste content of 0.19% by solids, which is basically the same as Example 1.

[0096] Comparative Example 6

[0097] Example 1 was repeated, except that the weight parts of the raw materials for Comparative Example 6 were as shown in Table 2.

[0098] Table 2. Raw material weight parts for Example 6

[0099]

[0100] Comparative Example 7

[0101] Example 1 was repeated, except that the weight parts of the raw materials for Comparative Example 7 were as shown in Table 3.

[0102] Table 3 Comparative Example 7 Raw Material Weight Parts

[0103]

[0104] Comparative Example 8

[0105] Example 1 was repeated, except that the weight parts of the raw materials in Comparative Example 8 were as shown in Table 4.

[0106]

[0107] Comparative Example 9

[0108] Example 1 was repeated, except that the weight parts of the raw materials for Comparative Example 9 were as shown in Table 5.

[0109]

[0110] Experimental Example 1: Performance Testing of High-Gloss Electroplated Silver Coating

[0111] a. Preparation of composite coating samples compatible with liquid varnish

[0112] Substrate: Aluminum alloy sheet coated with powder primer

[0113] The coating composition of a single product is as follows: aluminum alloy plate coated with powder primer + black primer (baked at 140℃ for 25 minutes) + electroplated silver paint + liquid varnish (baked at 140℃ for 25 minutes).

[0114] The composition of a recoating of a substandard coating: a sample of a substandard coating + black primer (baked at 140℃ for 25 minutes) + electroplated silver paint + liquid varnish (baked at 140℃ for 25 minutes).

[0115] Composition of the second-coated sample: first-coated sample + black primer (baked at 140℃ for 25 minutes) + electroplated silver paint + liquid varnish (baked at 140℃ for 25 minutes).

[0116] b. Preparation of composite coating samples compatible with powder varnish

[0117] Substrate: Aluminum alloy sheet coated with powder primer

[0118] The coating composition of the first-piece product is as follows: aluminum alloy plate coated with powder primer + black primer (flash-dry at 80℃ for 5 minutes) + electroplated silver coating (baked at 140℃ for 25 minutes) + powder clear varnish (baked at 180℃ for 20 minutes).

[0119] The composition of the first-time recoating of the substandard coating is as follows: first-time coating sample + black primer (80℃*5min flash-dry) + electroplated silver paint (140℃*25min baking) + powder clear varnish (180℃*20min baking).

[0120] Composition of the second-coated sample: first-coated sample + black primer (80℃*5min flash-dry) + electroplated silver paint (140℃*25min baking) + powder clear varnish (180℃*20min baking).

[0121] The performance testing methods are shown in Table 6:

[0122] Table 6 Performance Testing Methods

[0123] Testing items Testing methods and requirements Coating appearance Visually, the paint film is smooth and the aluminum powder is evenly distributed. 20° gloss ≥230 Adhesion Adhesion ≤ Grade 1, 2mm cross-cut adhesion test Water resistance After 40℃ for 240 hours, no abnormalities such as bubbles, whitening, or peeling were observed; secondary adhesion was ≤ Grade 1. 2-coat properties Adhesion ≤ Grade 1, 2mm cross-cut adhesion test CASS (Acid and Salt Spray Resistant) 240h, maximum single-sided corrosion ≤3mm

[0124] The baking performance of Example 1 and Comparative Examples 1-7 was tested using the above method, and the results are shown in Tables 7, 8, 9, 10, 11 and 12.

[0125] Table 7. Coating performance of Examples 1 and Comparative Examples 1-3 in conjunction with liquid varnish.

[0126]

[0127] Table 8. Coating performance of Examples 1 and Comparative Examples 1-3 in conjunction with powder varnish.

[0128]

[0129]

[0130] Table 9 shows the coating performance of Comparative Examples 4-7 with liquid varnish.

[0131]

[0132] Table 10 shows the coating performance of Comparative Examples 4-7 when used with powder varnish.

[0133]

[0134] Table 11 shows the coating performance of Comparative Examples 8-9 when used with liquid varnish.

[0135]

[0136] Table 12 shows the coating performance of Comparative Examples 8-9 in conjunction with powder varnish.

[0137]

[0138]

[0139] As can be seen from Tables 7 and 8, the high-gloss electroplated silver coating prepared in Example 1, when used with liquid varnish and powder varnish, has a composite coating with a 20° gloss > 230, and the coating film has qualified properties such as water resistance and recoating.

[0140] In Comparative Example 1, commercially available hydroxyl acrylic resin AP 545 and other solids were used to replace the hydroxyl hyperbranched resin in Example 1. Because the amount of hydroxyl acrylic resin was small, it had little interference with the arrangement of aluminum powder. The 20° gloss of the composite coating was >230, which was acceptable. However, the number of reactive groups of the hydroxyl acrylic resin was insufficient, resulting in insufficient crosslinking density with the end-capped isocyanate resin. The water resistance, recoating and acid salt spray resistance were all unacceptable.

[0141] In Comparative Example 2, commercially available amino resin BR 20SE and other solids were used to replace the end-capped isocyanate resin in Example 1. The amino resin BR 20SE interfered with the arrangement of aluminum powder, and the 20° gloss of the electroplated silver composite coating was <230, which was unqualified. Furthermore, the crosslinking density produced by the reaction of amino resin and hydroxyl hyperbranched resin was not as high as that produced by the reaction of end-capped isocyanate resin and hydroxyl hyperbranched resin, resulting in unqualified water resistance, recoating and acid salt spray resistance.

[0142] In Comparative Example 3, commercially available thermosetting acrylic resin TAR-3753-70 and amino resin BR 20SE were used to replace the end-capped isocyanate resin DESMODUR BL 3575 SN and hydroxyl hyperbranched resin CYGLAZ BB 500 in Example 1. The acrylic and amino resins were fully crosslinked, and the coating film passed the tests for water resistance, recoating, and acid salt spray resistance. However, the arrangement of the electroplated silver aluminum powder was disturbed, and the 20° gloss of the electroplated silver composite coating was <230, which was not up to standard.

[0143] As can be seen from Tables 9 and 10, in Comparative Example 4, commercially available polyester resin SETAL173 VS 60 and amino resin BR 20SE were used to replace the end-capped isocyanate resin DESMODUR BL 3575 SN and hydroxyl hyperbranched resin CYGLAZ BB 500 in Example 1. The polyester resin and amino resin were fully crosslinked, and the coating film met the requirements for water resistance, recoating, and acid salt spray resistance. However, the arrangement of the electroplated silver aluminum powder was disturbed, and the 20° gloss of the electroplated silver composite coating was <230, which was not up to standard.

[0144] Comparative Example 5 is a commercially available ordinary electroplated silver coating. The electroplated silver composite coating has a gloss of <230 at 20°, which is unqualified.

[0145] Comparative Example 6: The amount of electroplating silver resin AMORSO-789A exceeded the upper limit of 6%. The 20° gloss of the composite coating was >230, which was qualified. However, the excessive amount of electroplating silver resin made the electroplated silver coating brittle, and the composite coating failed to meet the requirements for water resistance, recoating and other properties.

[0146] Comparative Example 7: The amount of AMORSO-789A electroplating resin was less than the lower limit of 4%, resulting in poor arrangement of electroplated silver aluminum powder and a gloss level of <230 for the electroplated silver composite coating at 20°, which was considered unqualified.

[0147] As can be seen from Tables 11 and 12, in Comparative Example 8, the amount of hydroxyl hyperbranched resin CYGLAZ BB 500 was below the lower limit of 0.04%, and the 20° gloss of the composite coating was >230, which was qualified. However, the reduced number of hydroxyl reactive groups led to insufficient crosslinking density of the electroplated silver layer paint film, and the coating film failed to meet the requirements for water resistance, recoating, and acid salt spray resistance.

[0148] Comparative Example 9: The amount of the end-capped isocyanate resin DESMODUR BL 3575SN was below the lower limit of 0.3%. The 20° gloss of the composite coating was >230, which was qualified. However, the reduced number of isocyanate reactive groups resulted in insufficient crosslinking density of the electroplated silver layer film. The coating film failed to meet the requirements for water resistance, recoating, and acid salt spray resistance.

[0149] Example 2

[0150] Example 1 is repeated, except that the weight parts of the raw materials in Example 2 are as shown in Table 13.

[0151] Table 13. Raw material weight parts for Example 2

[0152]

[0153] Example 3

[0154] Example 1 was repeated, except that the weight proportions of the raw materials in Example 3 are shown in Table 14. The capped isocyanate resin used was TKA-B75S with a non-volatile content of 75%.

[0155] Table 14. Raw material weight parts for Example 3

[0156]

[0157] The preparation of the high-gloss electroplated silver coating includes the following steps:

[0158] 1) Passivation of electroplated silver aluminum paste: Add 2 parts of electroplated silver aluminum paste and 10 parts of butyl acetate to container A, stir at 300-400 r / min, add 0.02 parts of coupling agent SE 01-A2, stir for 10-15 min, then add 0.04 parts of anti-silver-dropping additive 120, continue stirring for 30-40 min, stop stirring, then take 8.99 parts of butyl acetate solvent to rinse the aluminum paste on the stirring paddle and container wall, seal container A, and let stand for 4 h to passivate the aluminum paste for later use;

[0159] 2) Preparation of mixed resin semi-finished product: Add 5 parts of propylene glycol methyl ether acetate to container B, stir at 200-300 r / min, add 0.06 parts of hydroxyl hyperbranched resin CYGLAZ BB 500, and rinse the container wall and stirring paddle with 2 parts of propylene glycol methyl ether acetate. Stir for 5-10 min, then add 0.4 parts of end-capped isocyanate TKA-B75S, increase the stirring speed to 400-500 r / min and continue stirring for 20-30 min. Stop stirring and set aside.

[0160] 3) In another container C, add 18 parts of methyl isobutyl ketone and stir at 200-300 r / min. Add 5.0 parts of electroplating silver resin AMORSO-789A, increase the stirring speed to 400-500 r / min, stir for 5-10 min, add the electroplating silver aluminum paste from step 1, and add 10 parts of propylene glycol methyl ether acetate after rinsing container A. Stir for 20-30 min.

[0161] 4) Add the mixed resin semi-finished product from step 2 to container C, and add 10 parts of propylene glycol methyl ether acetate after rinsing container B. Stir for 10-20 minutes.

[0162] 5) Add the formulated amount of additives, the remaining 9 parts of propylene glycol methyl ether acetate, 3.5 parts of ethyl 3-ethoxypropionate and 16 parts of aromatic solvent S-100# to container C, and continue stirring for 30-40 minutes to obtain the high-gloss electroplating silver coating composition.

[0163] Example 4

[0164] The raw material weight parts of the high-gloss electroplated silver coating composition in Example 4 are shown in Table 15.

[0165] Table 15. Raw material weight parts for Example 4

[0166]

[0167] The preparation of the high-gloss electroplated silver coating includes the following steps:

[0168] 1) Passivation of electroplated silver aluminum paste: Add 2 parts of electroplated silver aluminum paste and 10 parts of butyl acetate to container A, stir at 300-400 r / min, add 0.02 parts of coupling agent SE 01-A2, stir for 10-15 min, then add 0.04 parts of anti-silver-dropping additive 120, continue stirring for 30-40 min, stop stirring, then take 7.88 parts of butyl acetate solvent to rinse the aluminum paste on the stirring paddle and container wall, seal container A, and let stand for 4 h to passivate the aluminum paste for later use;

[0169] 2) Preparation of mixed resin semi-finished product: Add 5 parts of propylene glycol methyl ether acetate to container B, stir at 200-300 r / min, add 0.06 parts of hydroxyl hyperbranched resin CYGLAZ BB 500, and rinse the container wall and stirrer with 2 parts of propylene glycol methyl ether acetate. Stir for 5-10 min, then add 0.4 parts of end-capped isocyanate DESMODUR BL 3575SN, increase the stirring speed to 400-500 r / min and continue stirring for 20-30 min. Stop stirring and set aside.

[0170] 3) In another container C, add 18 parts of methyl isobutyl ketone and stir at 200-300 r / min. Add 5.0 parts of electroplating silver resin AMORSO-789A, increase the stirring speed to 400-500 r / min, stir for 5-10 min, add the electroplating silver aluminum paste from step 1, and add 10 parts of propylene glycol methyl ether acetate after rinsing container A. Stir for 20-30 min.

[0171] 4) Add the mixed resin semi-finished product from step 2 to container C, and add 10 parts of propylene glycol methyl ether acetate after rinsing container B. Stir for 10-20 minutes.

[0172] 5) Add the formulated amount of additives, the remaining 9 parts of propylene glycol methyl ether acetate, 3.5 parts of ethyl 3-ethoxypropionate and 16 parts of aromatic solvent S-100# to container C, and continue stirring for 30-40 minutes to obtain the high-gloss electroplating silver coating composition.

[0173] Example 5

[0174] Same as Example 1, except that the hydroxyl hyperbranched resin is CYGLAZ BB 600, which accounts for 0.04% of the total formulation.

[0175] Example 6

[0176] Same as Example 1, except that the electroplated silver aluminum paste is A-41014 has an aluminum powder particle size of 14μm and a non-volatile content of 10.0%.

[0177] Example 7

[0178] Same as Example 1, except that the end-capped isocyanate resin is TKA-B75S and has a non-volatile content of 75%.

[0179] Example 8

[0180] Same as Example 1, except that the electroplating silver resin is A-108, and its non-volatile content is 8%.

[0181] Example 9

[0182] Same as Example 1, except that the electroplated silver resin accounts for 4 wt% of the total amount, the hydroxyl hyperbranched resin accounts for 0.04 wt% of the total amount, and the end-capped isocyanate resin accounts for 0.3 wt% of the total amount.

[0183] Example 10

[0184] Same as Example 1, except that the electroplated silver resin accounts for 6 wt% of the total amount, the hydroxyl hyperbranched resin accounts for 0.06 wt% of the total amount, and the end-capped isocyanate resin accounts for 0.5 wt% of the total amount.

[0185] Following the method described in Example 1 above, the gloss and main coating properties of the high-gloss electroplated silver coating compositions obtained in Examples 2-10 were tested. The test results are shown in Tables 16 and 17, and the test results are similar to those in Example 1.

[0186] Table 16 Main film properties of the high-gloss electroplated silver coatings and liquid varnishes used in Examples 2-10

[0187] Example luster Water resistance Recoatability CASS Example 2 236, qualified Level 0, Qualified Level 0, Qualified 2mm, qualified Example 3 233, qualified Level 0, Qualified Level 0, Qualified 3mm, acceptable Example 4 241, qualified Level 0, Qualified Level 0, Qualified 2mm, qualified Example 5 238, qualified Level 0, Qualified Level 0, Qualified 2mm, qualified Example 6 235, qualified Level 0, Qualified Level 0, Qualified 3mm, acceptable Example 7 234, qualified Level 0, Qualified Level 0, Qualified 2mm, qualified Example 8 233, qualified Level 0, Qualified Level 0, Qualified 2mm, qualified Example 9 236, qualified Level 0, Qualified Level 0, Qualified 3mm, acceptable Example 10 239, qualified Level 0, Qualified Level 0, Qualified 1mm, acceptable

[0188] Table 17 Main film properties of the high-gloss electroplated silver coatings and powder varnishes used in Examples 2-10

[0189] Example luster Water resistance Recoatability CASS Example 2 234, qualified Level 0, Qualified Level 0, Qualified 1mm, acceptable Example 3 235, qualified Level 0, Qualified Level 1, Qualified 3mm, acceptable Example 4 243, qualified Level 0, Qualified Level 0, Qualified 2mm, qualified Example 5 239, qualified Level 0, Qualified Level 0, Qualified 2mm, qualified Example 6 232, qualified Level 0, Qualified Level 0, Qualified 2mm, qualified Example 7 236, qualified Level 0, Qualified Level 0, Qualified 2mm, qualified Example 8 235, qualified Level 0, Qualified Level 0, Qualified 2mm, qualified Example 9 238, qualified Level 0, Qualified Level 1, Qualified 2mm, qualified Example 10 241, qualified Level 0, Qualified Level 0, Qualified 1mm, acceptable

[0190] Example 11

[0191] Similar to Example 1, the only difference is that the aluminum powder was not passivated with coupling agent SE 01-A2, but was directly added in step 5. As a result, the water resistance of the high-gloss electroplated silver coating was not up to standard.

[0192] Example 12

[0193] Similar to Example 1, the only difference is that the solvent for dispersing the hydroxyl hyperbranched resin is an aromatic solvent. As a result, the high-gloss electroplated silver coating has poor recoating adhesion. The reason may be that the hydroxyl hyperbranched resin is highly polar and is not evenly dispersed in the non-polar aromatic solvent, resulting in agglomeration. Ultimately, it cannot fully react with the end-capped isocyanate resin, and the coating film is not fully cross-linked.

[0194] Example 13

[0195] Similar to Example 1, the only difference is that the electroplating silver resin was not pre-dissolved and dispersed with ketone solvents. Instead, the electroplating silver resin was added to container B after the end-capped isocyanate resin in step 2). As a result, the 20° gloss of the obtained electroplating silver coating composition was <230, and the adhesion was unqualified. The reason is that the electroplating silver resin has a large molecular weight and was not pre-dissolved and dispersed with a strong ketone solvent, resulting in poor miscibility of the electroplating silver resin with other resins, which led to reduced adhesion.

[0196] Example 14

[0197] Same as Example 1, except that the raw materials used in Example 14 are shown in Table 18. The coating performance test results of the high-gloss electroplated silver coating composition prepared in Example 14 are similar to those of Example 1.

[0198] Table 18. Raw material weight parts for Example 14

[0199]

[0200] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A high-gloss electroplated silver coating, characterized in that, The raw materials for the electroplating silver coating include an electroplating silver coating composition, which, by weight percentage, comprises: Electroplating silver aluminum paste: 1.8-2.2%; Electroplating silver resin 4.0-6.0%; Hydroxyl hyperbranched resin 0.04-0.06%; End-capped isocyanate resin 0.3-0.5%; Anti-silver-dropping agent: 0.03-0.05%; Additives 0.08-0.13%; Solvent content: 91.0-93.0%; The hydroxyl hyperbranched resin is a polyester polyol, and the non-volatile content of the hydroxyl hyperbranched resin is 53.0-63.0%, the viscosity is 150-550 mPa.s@25℃, and the hydroxyl content is 4.8-6.3% based on solid resin. The preparation of the electroplated silver coating includes the following steps: 1) Passivate the electroplated silver-aluminum paste using a coupling agent to obtain a passivated electroplated silver-aluminum paste; 2) Dissolve the hydroxyl hyperbranched resin and the end-capped isocyanate resin in a portion of the solvent, mix well, and obtain a mixed resin semi-finished product; 3) The electroplating silver resin is pre-dissolved and dispersed using ketone solvents, then the electroplating silver resin is mixed with the passivated electroplating silver aluminum paste, and then mixed with the mixed resin semi-finished product. Additives and remaining solvents are added to obtain the high-gloss electroplating silver coating.

2. The high-gloss electroplated silver coating according to claim 1, characterized in that, The aluminum powder in the electroplating silver aluminum paste has a particle size of 8-14μm, and the non-volatile content of the electroplating silver aluminum paste is 9.90-10.10%.

3. The high-gloss electroplated silver coating according to claim 1, characterized in that, The electroplating silver resin has a non-volatile content of 7.5-8.5% and a Gardner viscosity of W-Z3.

4. The high-gloss electroplated silver coating according to claim 1, characterized in that, The terminated isocyanate resin has a non-volatile content of 73.0-77.0%, a deblocking temperature of 110-150℃, and a terminated isocyanate functional group content of 8%-12wt%.

5. The high-gloss electroplated silver coating according to claim 1, characterized in that, The anti-silver-dropping additive is a low-acid modified polyester compound with a non-volatile content of 78.0-82%.

6. The high-gloss electroplated silver coating according to claim 1, characterized in that, The additives are selected from one or more of the following: leveling agents, ultraviolet absorbers, light stabilizers, coupling agents, or wetting and dispersing agents.

7. The high-gloss electroplated silver coating according to claim 6, characterized in that, The additives comprise, by weight percentage of the total weight of the electroplated silver coating composition: Leveling agent 0.04-0.06%; Ultraviolet absorber 0.02-0.03%; Light stabilizer 0.01-0.02%; Coupling agent 0.01-0.02%.

8. The high-gloss electroplated silver coating according to claim 1, characterized in that, The solvent is selected from one or more of ketone solvents, ester solvents, and aromatic solvents.

9. The high-gloss electroplated silver coating according to claim 8, characterized in that, The ester solvent is selected from one or more of propylene glycol methyl ether acetate, ethyl 3-ethoxypropionate, butyl propionate, butyl acetate, and ethyl acetate, and the ester solvent accounts for 56.0-60.0% of the total weight of the electroplating silver coating composition.

10. The high-gloss electroplated silver coating according to claim 8, characterized in that, The ketone solvent is selected from one or more of cyclohexanone, methylpentyl ketone, methyl isopentyl ketone and methyl isobutyl ketone, and the ketone solvent accounts for 16.0-20.0% of the total weight of the electroplating silver coating composition.

11. The high-gloss electroplated silver coating according to claim 8, characterized in that, The aromatic solvent is selected from one or more of xylene, S-100#, and S-150#, and the aromatic solvent accounts for 14.0-18.0% of the total weight of the electroplating silver coating composition.

12. The application of the high-gloss electroplated silver coating as described in claims 1-11 in the coating of automobile wheel hubs.

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