Water-based metal finish paint as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of water-based paint, and discloses water-based metal finish paint as well as a preparation method and application thereof. The water-based metal finish paint is prepared from the following components in parts by weight: 30 to 55 parts of water-based hydroxy acrylic resin, 10 to 15 parts of modified water-based polyurethane dispersion, 3 to 10 parts of saturated polyester resin, 7 to 15 parts of amino resin, 12 to 20 parts of effect pigment paste and 0.5 to 1 part of wetting agent, the hydroxyl value of the saturated polyester resin is 310 mgKOH / g to 600 mgKOH / g; the amino resin is mixed etherified melamine formaldehyde resin. According to the water-based metal finishing paint, water is used as a dispersion medium, comprehensive breakthrough of the water-based metal finishing paint among corrosion resistance, thermal stability, freezing-resistant stability, durability and environment friendliness is achieved through multi-component collaborative design and accurate proportion control, a paint film formed by the water-based metal finishing paint has metallic luster and excellent mechanical properties, and the water-based metal finishing paint can be widely applied to the field of metal products. The water-based paint can be widely applied to the fields of automobiles, household appliances, building metal components and the like, and a new solution is provided for high performance of the water-based industrial paint.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water-based paint, in particular to a water-based metal finish paint, a preparation method and application thereof. BACKGROUND

[0002] Traditional solvent-based paint contains a large amount of volatile organic compounds (VOC), which will emit a large amount of harmful substances into the atmosphere during production, construction and use, causing serious pollution to the environment and posing a potential threat to human health. For example, the oil-based high-temperature metal paint widely used in the field of aluminum alloy door and window coating contains a large amount of harmful solvents such as dimethylbenzene. These harmful solvents volatilize into the air during construction, not only seriously endanger the health of construction workers, but also may cause respiratory diseases, nervous system damage and other health problems after long-term contact. Moreover, with the tightening of environmental protection policies, oil-based high-temperature metal paint with high VOC emission is facing strict policy restrictions, and its production and use are subject to many constraints, and the market development space is gradually shrinking. Under this situation, water-based paint gradually becomes the mainstream direction of the development of the paint industry with its obvious advantages of low VOC emission, non-toxic and odorless, no fire hazard during construction, and easy cleaning of coating tools, and gradually replaces traditional solvent-based paint in many fields.

[0003] However, in actual industrial application, water-based paint still has the following significant defects: (1) drying and hardness performance defects: the high water content of existing water-based paint will significantly prolong the surface drying and real drying time of the paint film, significantly reduce production efficiency, and the hardness of the dried paint film is poor, which is easy to scratch during transportation and installation, affecting the qualified rate of finished products; (2) poor low-temperature adaptability: the freezing property of water makes the existing water-based paint prone to freezing during transportation in winter low-temperature environment (<0℃), resulting in emulsion demulsification and performance degradation, which cannot be used normally; at present, although the problem can be solved by using heat preservation transportation, the heat preservation cost will significantly increase the overall cost due to the fact that the water-based paint market has not yet formed a scale effect, which restricts its market application; (3) insufficient corrosion resistance: the presence of hydrophilic groups in existing water-based paint leads to a decrease in the medium resistance of the paint film, which is easily eroded by water, acid and alkali, especially poor resistance to organic acids such as acetic acid, which seriously affects the long-term stability of the coating in humid or corrosive environments (such as kitchens and acid rain areas). In addition, the existing water-based paint also attempts to improve water resistance and freeze-thaw stability by adding additives, but the presence of additives will affect the hardness, adhesion and weather resistance of the paint film after high-temperature baking, making it difficult to be practically applied.

[0004] Therefore, it is of urgent practical significance to develop a water-based high-temperature metal finish paint that can replace oil-based high-temperature metal paint, meet the stringent use requirements of aluminum alloy doors and windows, and has both acetic acid corrosion resistance and freeze stability, in order to promote the green transformation of the aluminum alloy door and window coating industry. SUMMARY

[0005] The present application aims to overcome the deficiencies of the prior art and provide a water-based metallic finish, a preparation method and application thereof.

[0006] To achieve the above-mentioned object, the technical scheme adopted by the present application is as follows:

[0007] In a first aspect, the present application provides a water-based metallic finish, comprising the following components in parts by weight: water-based hydroxyl acrylic resin 30-55 parts, modified water-based polyurethane dispersion 10-15 parts, saturated polyester resin 3-10 parts, amino resin 7-15 parts, effect pigment paste 12-20 parts, wetting agent 0.5-1 part; the hydroxyl value of the saturated polyester resin is 310 mgKOH / g-600 mgKOH / g; the amino resin is mixed etherified melamine formaldehyde resin; the mass ratio of the saturated polyester resin and the amino resin is 1:(1.2-5).

[0008] The water-based metallic finish of the present application is a stable and high-performance water-based coating system constructed through the synergistic effect of water-based hydroxyl acrylic resin, modified water-based polyurethane dispersion, saturated polyester resin, mixed etherified melamine formaldehyde resin, effect pigment paste, and wetting agent, which has excellent durability, wear resistance, corrosion resistance, thermal storage stability, freeze-thaw resistance, and the formed paint film has excellent metallic texture, decorative properties, and outstanding mechanical properties. Among them, the water-based hydroxyl acrylic resin of the present application as the main film-forming material can synergize with other components to make the water-based metallic finish have excellent weather resistance, chemical corrosion resistance, and initial adhesion, and the hydroxyl functional group thereof can crosslink with the amino resin (mixed etherified melamine formaldehyde resin) to form a crosslinked network, significantly improving the solvent resistance of the water-based metallic finish and the hardness of the paint film. Secondly, the water-based metallic finish of the present application introduces flexible segments through modified water-based polyurethane dispersion, forming an interpenetrating network structure with acrylic resin, which not only maintains the hardness but also endows the paint film with excellent flexibility, impact resistance, and low-temperature toughness, avoiding brittle cracking. At the same time, the saturated polyester resin with a specific hydroxyl value of the present application can not only rapidly react with the amino resin (mixed etherified melamine formaldehyde resin) to shorten the curing time, but also fill in the micro-defects in the acrylic-polyurethane network to form a more dense three-dimensional structure. On the other hand, it can synergize with other components to improve the freeze-thaw resistance of the water-based metallic finish, making it suitable for extreme climate areas (such as outdoor facilities in cold regions) or cold chain transportation scenarios. In addition, through the synergistic design of multiple components and precise proportion control, the present application has achieved a comprehensive breakthrough in the decorative properties, mechanical properties, durability, and environmental friendliness of the water-based metallic finish, and the formed paint film has both metallic luster, high hardness, excellent wear resistance, and super-long corrosion resistance, which can be widely applied in the fields of automobiles, home appliances, and building metal components, providing a new solution for the high performance of water-based industrial coatings.

[0009] As a preferred embodiment of the water-based metallic finish paint, the hydroxyl value of the saturated polyester resin is 330 mgKOH / g-560 mgKOH / g.

[0010] As a preferred embodiment of the water-based metallic finish paint, the mass ratio of the saturated polyester resin and the amino resin is 1:(1.2-2.4).

[0011] Preferably, the mass ratio of the saturated polyester resin and the amino resin is one or a range value of two of 1:1.2, 1:1.5, 1:2, 1:2.4.

[0012] As a preferred embodiment of the water-based metallic finish paint, the hydroxyl value of the water-based hydroxyl acrylate resin is 80 mgKOH / g-100 mgKOH / g.

[0013] As a preferred embodiment of the water-based metallic finish paint, the molar ratio of the hydroxymethyl, imino, methoxy, butoxy of the mixed etherified melamine formaldehyde resin is 1:(2-5):(4-9):(3-7); the degree of polymerization of the mixed etherified melamine formaldehyde resin is <1.8, and the solid content is >75%.

[0014] Preferably, the molar ratio of the hydroxymethyl, imino, methoxy, butoxy of the mixed etherified melamine formaldehyde resin is 1:3.2:5.5:4.1.

[0015] The mixed etherified melamine formaldehyde resin with specific functional groups of the present application can have a high-efficiency cross-linking reaction with the base resin to form a dense three-dimensional network structure, and through the synergistic regulation of the functional group ratio, the water resistance, flexibility and acetic acid resistance of the water-based metallic finish paint are further effectively improved, so that the water-based metallic finish paint can still remain stable in a humid environment or acidic medium, thereby providing key technical support for the application of water-based high-temperature metallic finish paint in the field of high-end metal products.

[0016] As a preferred embodiment of the water-based metallic finish paint, the effect pigment paste includes oily aluminum powder, pH adjuster, metal inhibitor and cosolvent; the mass ratio of the oily aluminum powder, pH adjuster, metal inhibitor and cosolvent is 1:(0.02-0.04):(0.2-0.4):(1-2).

[0017] Preferably, the mass ratio of the oily aluminum powder, pH adjuster, metal inhibitor and cosolvent is 1:0.03:0.3:1.5.

[0018] Preferably, the effect pigment paste further includes a colorant.

[0019] As a preferred embodiment of the water-based metallic finish paint, the co-solvent is propylene glycol butyl ether and / or ethylene glycol hexyl ether; the pH regulator is dimethyl ethanolamine; and the metal inhibitor is a phosphorus-containing organic compound.

[0020] Preferably, the co-solvent is propylene glycol butyl ether.

[0021] As a preferred embodiment of the water-based metallic finish paint, the lubricant includes a modified silicone wetting agent and / or an acetylenic diol wetting agent.

[0022] Preferably, the lubricant includes a modified silicone wetting agent and an acetylenic diol wetting agent in a mass ratio of 1:1.

[0023] In a second aspect, the present application provides a preparation method of the water-based metallic finish paint, including the following steps:

[0024] (1) uniformly mixing the water-based hydroxyl acrylic resin and the modified water-based polyurethane dispersion to obtain a mixture A;

[0025] (2) slowly adding the saturated polyester resin to the mixture A, uniformly mixing, and then adding the amino resin to obtain a mixture B;

[0026] (3) slowly adding the effect pigment paste to the mixture B, uniformly mixing, and then adding the wetting agent to obtain a mixture C;

[0027] (4) filtering the mixture C to obtain the water-based metallic finish paint.

[0028] As a preferred embodiment of the preparation method of the water-based metallic finish paint, in step (1) and / or in step (2), the mixing is performed by stirring; and the stirring speed is 400 rpm-800 rpm.

[0029] As a preferred embodiment of the preparation method of the water-based metallic finish paint, in step (3), the mixing is performed by stirring; and the stirring speed is 300 rpm-600 rpm.

[0030] As a preferred embodiment of the preparation method of the water-based metallic finish paint, in step (4), the filter hole diameter of the filtering is 100 μm-200 μm.

[0031] In a third aspect, the present application provides an application of the water-based metallic finish paint in building equipment, home equipment, transportation equipment, and industrial mechanical equipment.

[0032] Compared with existing technologies, the beneficial effects of this invention are as follows: The water-based metallic topcoat of this invention uses water as the dispersion medium. Through multi-component synergistic design and precise ratio control, it achieves a comprehensive breakthrough in corrosion resistance, thermal stability, durability, and environmental friendliness. The resulting paint film possesses both metallic luster and excellent mechanical properties, and can be widely applied in the automotive, home appliance, and building metal component fields, providing a new solution for the high-performance of water-based industrial coatings. Specifically, the water-based metallic topcoat of this invention has a high metallic rating and its decorative properties far exceed those of traditional colored paints, meeting the appearance requirements of high-end metal products such as automotive and home appliance casings. Furthermore, the paint film adhesion meets national standards, and the paint film hardness is higher than ordinary water-based paints. It can form strong chemical bonds with the substrate, maintaining its integrity even after thermal expansion and contraction or mechanical stress, effectively resisting mechanical impacts during transportation and installation, and significantly extending its service life. Secondly, the dense cross-linked structure of the water-based metallic topcoat of this invention endows it with excellent water resistance and acid and alkali resistance, enabling it to resist corrosion from acidic industrial environments (such as chemical plant equipment), atmospheric acid rain, and alkaline environments (such as cement buildings and cleaning agent contact scenarios) for extended periods, making it particularly suitable for humid environments. Simultaneously, the water-based metallic topcoat of this invention exhibits excellent environmental adaptability; the state of the paint liquid and film remains unchanged after high-temperature aging, effectively avoiding problems such as layering, clumping, or performance degradation during storage. Furthermore, it possesses excellent freeze-thaw resistance, easily adapting to extreme climatic conditions in cold-climate outdoor facilities or cold chain transportation scenarios. Moreover, the preparation method of the water-based metallic topcoat of this invention is mild, with simple preparation steps, facilitating repeated operation and mass production. Detailed Implementation

[0033] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below with reference to specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0034] The following description, in conjunction with specific embodiments, illustrates the practical effects of the present invention.

[0035] Unless otherwise specified, the experimental methods used in the examples are conventional methods; the materials, reagents, equipment, etc. used are all commercially available unless otherwise specified.

[0036] The raw materials used in the following embodiments and comparative examples are described below, but are not limited to these materials:

[0037] The waterborne hydroxyl acrylic resin, purchased from Changzhou Guangshu Chemical Technology Co., Ltd., is model GS-360, with a hydroxyl content of 99 mg KOH / g.

[0038] Modified waterborne polyurethane dispersion, purchased from Wanhua Chemical Group Co., Ltd., model number: 6140;

[0039] Saturated polyester resin 1, purchased from Deshengli Chemical Co., Ltd., model Worlée Pol 1181 / 03, hydroxyl value content 330 mg KOH / g;

[0040] Saturated polyester resin 2, purchased from Pastro, model CAPA 3031, hydroxyl value content 560 mg KOH / g;

[0041] Mixed etherified melamine formaldehyde resin, purchased from Allnex Co., Ltd., model CYMEL 202, which contains hydroxymethyl, imino, methoxy, butoxy functional groups, the molar ratio of hydroxymethyl, imino, methoxy, butoxy is 1:3.2:5.5:4.1; the polymerization degree is 1.6, and the solid content is 80%;

[0042] Metal inhibitor is a phosphorus-containing organic compound, purchased from Guangdong Di'aishengtongde Resin Co., Ltd., model WD01;

[0043] Wetting agent includes modified siloxane wetting agent and acetylenic diol wetting agent in a mass ratio of 1:1, the modified siloxane weting agent is purchased from BYK Germany, model BYK-348; the acetylenic diol wetting agent is purchased from Yinchuang, model Surfynol 104BC;

[0044] Oily aluminum powder, purchased from Shandong Yinzhen Metal Pigment Co., Ltd., model BD09, D50 is 17 μm.

[0045] The hydroxyl value content of the above resin refers to the milligrams of potassium hydroxide (KOH) equivalent to the hydroxyl group in 1 gram of solid or dry resin, and the test standard is GB / T 31412-2015.

[0046] The preparation method of the effect pigment paste used in the following examples and comparative examples includes the following steps:

[0047] (1) Take a clean and water-free container, add a cosolvent, stir at a shear speed of 250 rpm, and slowly add a metal inhibitor, disperse until uniform and transparent;

[0048] (2) Then slowly add dimethyl ethanolamine (DMEA) into the container of step (1) and disperse uniformly, at this time the temperature of the mixture in the container will rise slightly;

[0049] (3) When the temperature of the mixture in the container is below 35℃, slowly add oily aluminum powder, continue to disperse, ensure that the oily aluminum powder is fully stirred and uniformly dispersed, and there is no caking phenomenon, so that the metal inhibitor can fully coat and passivate the surface of the aluminum powder.

[0050] Table 1: Raw material component ratio of effect pigment paste (weight percentage)

[0051]

[0052]

[0053] Example 1:

[0054] The present example provides a waterborne high temperature metallic finish, which is prepared from the following components in the following weight percentages: 40 wt% waterborne hydroxyl acrylic resin, 15 wt% modified waterborne polyurethane dispersion, 5 wt% saturated polyester resin 1, 12 wt% mixed etherified melamine formaldehyde resin, 15 wt% effect pigment paste 1, 0.5 wt% wetting agent, 12.5 wt% deionized water.

[0055] The specific preparation method comprises the following steps:

[0056] (1) Take a clean container, and sequentially add the waterborne hydroxyl acrylic resin and the modified waterborne polyurethane dispersion, and mix under the shearing speed of 600 rpm; then slowly add the saturated polyester resin 1, and continuously disperse until the system is uniform; and then slowly add the mixed etherified melamine formaldehyde resin, and continue to stir until completely dispersed and uniform.

[0057] (2) Adjust the stirring speed to 500 rpm, slowly add the prepared effect pigment paste 1, and fully stir until uniform; then add the wetting agent and the deionized water, and continuously disperse until all components are completely fused, to obtain the initial mixture.

[0058] (3) Filter the initial mixture above, and the filter pore size is 150 microns, to obtain the waterborne high temperature metallic finish.

[0059] Examples 2-10:

[0060] The waterborne high temperature metallic finishes of Examples 2-10 below and Example 1 differ only in the types and / or mass percentages of the raw materials (as shown in Table 3).

[0061] Table 2: Raw material component proportions (weight percentages) of examples

[0062]

[0063] Comparative Example 1:

[0064] The present comparative example provides a waterborne high temperature metallic finish, which differs from Example 1 only in that the effect pigment paste used is effect pigment paste 6.

[0065] Comparative Example 2:

[0066] The comparative example provides a water-based high-temperature metallic finish paint, which is different from example 1 in that the effect pigment paste used is effect pigment paste 7.

[0067] Comparative example 3:

[0068] The comparative example provides a water-based high-temperature metallic finish paint, which is different from example 1 in that the effect pigment paste used is effect pigment paste 8.

[0069] Comparative example 4:

[0070] The comparative example provides a water-based high-temperature metallic finish paint, which is different from example 1 in that the effect pigment paste used is effect pigment paste 9.

[0071] Comparative example 5:

[0072] The comparative example provides a water-based high-temperature metallic finish paint, which is different from example 1 in that a mixture of propylene glycol butyl ether and water-based silicon-coated aluminum powder with a mass ratio of 1:1 is used instead of effect pigment paste 1; wherein the water-based silicon-coated aluminum powder is purchased from Shandong Yinjian Metal Pigment Co., Ltd., the model number is ZW-7116, and the D50 is 16 μm.

[0073] Comparative example 6:

[0074] The comparative example provides a water-based high-temperature metallic finish paint, which is different from example 1 in that a mixture of propylene glycol butyl ether and passivated silver powder with a mass ratio of 1:1 is used instead of effect pigment paste 1; wherein the passivated silver powder is purchased from Shandong Yinjian Metal Pigment Co., Ltd., the model number is ZW-6117, and the D50 is 17 μm.

[0075] The comparative example provides a water-based high-temperature metallic finish paint, which is different from example 1 in that the polyester resin purchased from Zhenxin Resin (China) Co., Ltd., the model number is 6306SS-60 is used instead of saturated polyester resin 1; wherein, The hydroxyl value of the 6306SS-60 polyester resin is 90 mgKOH / g.

[0076] Comparative example 8:

[0077] The comparative example provides a water-based high-temperature metallic finish paint, which is different from example 1 in that the polyester resin purchased from Zhenxin Resin (China) Co., Ltd., the model number is DUROFTAL VPE 6117 is used instead of saturated polyester resin 1; wherein the hydroxyl value of the DUROFTAL VPE 6117 polyester resin is 130 mgKOH / g.

[0078] The comparative example provides a water-based high-temperature metal finish, which is different from example 1 in that: using the methoxylated amino resin with model number CYMEL 325 purchased from Zhenxin Resin (China) Co., Ltd. instead of mixed etherified melamine formaldehyde resin; wherein the methoxylated amino resin CYMEL 325 does not contain butoxyl, the molar ratio of hydroxymethyl, imino, methoxyl content is 1:2.2:4.8; the solid content is 80%, and the degree of polymerization is 1.5.

[0079] The comparative example provides a water-based high-temperature metal finish, which is different from example 1 in that: using the methoxylated amino resin with model number CYMEL 303 purchased from Zhenxin Resin (China) Co., Ltd. instead of mixed etherified melamine formaldehyde resin; wherein the methoxylated amino resin CYMEL 303 contains hydroxymethyl and methoxyl, and the molar ratio of methoxyl to hydroxymethyl is about 13:1, and the imino and butoxyl contents are both 0%; the solid content is 100%, and the degree of polymerization is 1.7.

[0080] Comparative example 11:

[0081] The comparative example provides a water-based high-temperature metal finish, which is different from example 1 in that: using the low-hydroxyl value water-based acrylic emulsion with model number SETAQUA 6803 purchased from Zhenxin Resin (China) Co., Ltd. instead of water-based hydroxyl acrylic resin; wherein the solid content of the low-hydroxyl value water-based acrylic emulsion SETAQUA 6803 is 24%, and the hydroxyl value is 30 mg KOH / g.

[0082] Comparative example 12:

[0083] The comparative example provides a water-based high-temperature metal finish, which is different from example 1 in that: using the high-hydroxyl value water-based hydroxyl acrylic resin with model number A2470 purchased from Covestro instead of water-based hydroxyl acrylic resin; wherein, the solid content of the high-hydroxyl value water-based hydroxyl acrylic resin A2470 is 45%, and the hydroxyl value is 128 mg KOH / g.

[0084] Comparative example 13:

[0085] The comparative example provides a water-based high-temperature metal finish, which is different from example 1 in that: using the thermosetting water-based acrylic modified polyester with model number RESYDROL AY 5537 purchased from Zhenxin Resin (China) Co., Ltd. instead of water-based hydroxyl acrylic resin; wherein the solid content of the thermosetting water-based acrylic modified polyester RESYDROL AY 5537 is 35%.

[0086] Comparative example 14:

[0087] ​This comparative example provides a waterborne high temperature metallic finish, which differs from Example 1 in that saturated polyester 1 is not used.

[0088] Comparative Example 15:

[0089] This comparative example provides a waterborne high temperature metallic finish, which differs from Example 1 in that the mass percentage of saturated polyester 1 is 15wt%.

[0090] Comparative Example 16:

[0091] This comparative example provides a waterborne high temperature metallic finish, which differs from Example 1 in that the mass percentage of mixed etherified melamine formaldehyde resin is 2wt%.

[0092] Comparative Example 17:

[0093] This comparative example provides a waterborne high temperature metallic finish, which differs from Example 1 in that the mass percentage of mixed etherified melamine formaldehyde resin is 30wt%.

[0094] Comparative Example 18:

[0095] This comparative example provides a waterborne high temperature metallic finish, which differs from Example 1 in that waterborne hydroxyl acrylic resin is not used.

[0096] Comparative Example 19:

[0097] This comparative example provides a waterborne high temperature metallic finish, which differs from Example 1 in that modified waterborne polyurethane dispersion is not used.

[0098] Test Example:

[0099] The relevant properties of the waterborne high temperature metallic finishes of the above examples and comparative examples are tested.

[0100] Test panel preparation: aluminum plates with a size of 150mm x 70mm are selected as the substrate, the aluminum plates are polished using 200 mesh sandpaper and are used after oil removal; the waterborne high temperature metallic finishes of each example and comparative example are sprayed on the aluminum plates to have a film thickness of 30μm; then flash drying is performed at 25℃, 50% RH for 30min, and then baking is performed at 140℃ for 15min to obtain the test panel, which is finally placed at room temperature for 1 day for performance testing.

[0101] (1) Metallic feeling test:

[0102] Test method and standard: the metallic feeling of the paint film on the test panel is directly observed by the eye to obtain the initial appearance test result, and the metallic feeling is divided into three levels of strong, slightly poor, and poor.

[0103] (2) Adhesion test:

[0104] Test standard: GB / T 9286-2021 "Paints and varnishes - Crosshatch adhesion test".

[0105] Test method: The adhesion grade of the sample was tested by crosshatch test at 25℃, and was graded. There were six grades in total, and the higher the grade, the more serious the peeling phenomenon of the paint film on the sample, and the worse the adhesion of the water-based high-temperature metal finish.

[0106] (3) Hardness test

[0107] Test standard: GB / T 6739-2006 "Pencil hardness of paint film".

[0108] Test method: The hardness grade of the paint film on the sample was tested at 25℃. For high-temperature paint, the hardness grade commonly used in the coating industry was from low to high: 3B-2B-B-HB-F-H-2H-3H-4H-5H-6H.

[0109] (4) Impact resistance test

[0110] Test standard: GB / T 1732-2020 "Paint film impact resistance test method".

[0111] (5) Water resistance test

[0112] Test standard: GB / T 5209-1985 "Water resistance of paints and varnishes - Immersion method".

[0113] Test method: The water resistance of the water-based high-temperature metal finish was tested. The deionized water used had a conductivity of ≤4 μs / cm, the water temperature was controlled at 99±1℃, and the test was conducted for 2 hours. The surface was observed for bubbles, wrinkles, discoloration, etc.

[0114] (6) Sulfuric acid resistance test

[0115] Test standard: GB / T 9274-1988 "Determination of resistance of paints and varnishes to liquid media".

[0116] Test method: The acid resistance of the water-based high-temperature metal finish was tested using the first method (immersion method). The test liquid was a 10% sulfuric acid solution, the test time was 48 hours, and the surface state change was observed.

[0117] (7) Alkali resistance test

[0118] Test standard: GB / T 9274-1988 "Determination of resistance of paints and varnishes to liquid media".

[0119] Test method: The alkali resistance of the water-based high-temperature metal finish was tested by using the A method (immersion method), the test liquid was a 10% sodium hydroxide solution by mass fraction, the test time was 48 hours, and the surface state change was observed.

[0120] (8) Acetic acid resistance performance test

[0121] Test standard: GB / T 9274-1988 "Determination of Resistance to Liquid Media of Color Paint and Varnish".

[0122] Test method: The acid resistance of the water-based high-temperature metal finish was tested by using the A method (immersion method), the test liquid was a 10% acetic acid solution by mass fraction, the test time was 48 hours, and the surface state change was observed.

[0123] (9) Heat storage stability performance test

[0124] Test method: The water-based high-temperature metal finish was sealed and placed in a constant temperature oven at 50°C for 30 days, then taken out and cooled to room temperature, the state of the sample paint was observed, then the sample plate was made, and the state of the paint film on the sample plate was observed directly by eye to obtain the heat storage stability test result.

[0125] (10) Freeze-thaw resistance test

[0126] Test method: The water-based high-temperature metal finish was sealed in a sample jar and placed in a freezer at -40°C, the sample jar did not contact the wall or bottom of the freezer (the sample jar could be placed on a shelf), and at least 25mm gap was left between adjacent sample jars and between the sample jar and the wall of the freezer to facilitate the free circulation of air around the sample. After 24 hours in the freezer, the sample jar was taken out and placed at room temperature.

[0127] Freeze-thaw performance result evaluation: The sample jar taken out of the freezer was placed for 6 hours for inspection and evaluation, and the sample was checked for ice hardening and fineness change, which was 1 cycle. If there was no ice hardening and fineness change, the next cycle was entered, the freeze-thaw resistance cycle number was tested and recorded. The maximum test cycle of the present application was 10 cycles, and when the freeze-thaw resistance cycle number was 10, it indicated that after 10 cycles, the state of the coating was still normal and the performance was not reduced.

[0128] Table 3: Performance test results of the water-based high-temperature metal finish of the test example of the present application

[0129]

[0130]

[0131]

[0132] As can be seen from the results in Table 3, the water-based high-temperature metallic finish of the embodiments of the present application performs well in terms of metal decoration effect, mechanical properties, chemical resistance and environmental adaptability, and has the potential to be used as a metallic finish in practical applications. Specifically, the water-based high-temperature metallic finish of the embodiments of the present application has a metal sense rating of "strong", indicating that the paint film achieves high dispersibility and directional arrangement of pigments, forming strong metallic luster and goniochromatic effect, and the decorative property is significantly better than that of traditional solid color paint, which can meet the appearance requirements of high-end metal products (such as automobile wheel hubs and household appliance housings). Secondly, the adhesion of the paint film formed by the water-based high-temperature metallic finish of the embodiments of the present application meets the GB / T 9286-2021 standard, and the hardness is also higher than that of ordinary water-based paint, indicating that a strong chemical bond can be formed between the paint film and the substrate, which can remain intact even after experiencing thermal expansion and contraction or mechanical stress, avoiding the risk of falling off and prolonging the service life; and the paint film is not easy to crack or peel off when subjected to high-speed impact, has high impact resistance, and is suitable for mechanical impact in scenarios such as transportation and installation. At the same time, the dense cross-linked structure of the water-based high-temperature metallic finish of the embodiments of the present application can effectively block the penetration of water, has excellent water resistance, and is suitable for humid environments; and has excellent acid and alkali resistance, which can resist acidic industrial environments (such as chemical plant equipment), atmospheric acid rain, and alkaline environments (such as cement buildings and cleaning agent contact scenarios). In addition, the water-based high-temperature metallic finish of the embodiments of the present application has excellent environmental adaptability. On the one hand, after aging at 50℃ for 30 days, the paint liquid and paint film state do not change, indicating that the metallic finish has excellent thermal stability, which can avoid phenomena such as delamination, caking or performance degradation during storage, and prolong the shelf life of the product; on the other hand, after several cycles of-40℃ to room temperature, the paint is in normal state, proving its low-temperature frost resistance and thermal storage stability, which can adapt to extreme climate regions (such as cold outdoor facilities) or cold chain transportation scenarios.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and not to limit the scope of protection of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. An aqueous metallic topcoat, characterized in that The water-based metal finish comprises the following components by weight: 30-55 parts of water-based hydroxyl acrylic resin, 10-15 parts of modified water-based polyurethane dispersion, 3-10 parts of saturated polyester resin, 7-15 parts of amino resin, 12-20 parts of effect pigment paste, 0.5-1 part of wetting agent; the saturated polyester resin has a hydroxyl value of 310 mgKOH / g-600 mgKOH / g; the amino resin is a mixed etherified melamine formaldehyde resin; the mass ratio of the saturated polyester resin to the amino resin is 1:(1.2-5).

2. The water-borne topcoat according to claim 1, wherein The mass ratio of the saturated polyester resin to the amino resin is 1:(1.2-2.4).

3. The water-borne topcoat according to claim 1, wherein The water-based hydroxyl acrylic resin has a hydroxyl value of 80 mgKOH / g-100 mgKOH / g.

4. The water-borne topcoat of claim 1, wherein, The mixed etherified melamine formaldehyde resin has a molar ratio of hydroxymethyl, imino, methoxy and butoxy of 1:(2-5):(4-9):(3-7); the mixed etherified melamine formaldehyde resin has a polymerization degree of <1.8 and a solid content of >75%.

5. The water-borne topcoat of claim 1, wherein The effect pigment paste comprises oily aluminum powder, pH adjuster, metal inhibitor and co-solvent; the mass ratio of the oily aluminum powder, pH adjuster, metal inhibitor and co-solvent is 1:(0.02-0.04):(0.2-0.4):(1-2).

6. The water-borne topcoat according to claim 5, wherein The co-solvent is propylene glycol butyl ether and / or ethylene glycol hexyl ether; the pH adjuster is dimethyl ethanolamine; the metal inhibitor is a phosphorus-containing organic compound.

7. The water-borne topcoat of claim 1, wherein The wetting agent is a modified siloxane wetting agent and / or acetylenic diol wetting agent.

8. Process for the production of the aqueous topcoat as claimed in any of claims 1 to 7, characterized in that The method comprises the following steps: (1) uniformly mixing the water-based hydroxyl acrylic resin and the modified water-based polyurethane dispersion to obtain a mixture A; (2) slowly adding the saturated polyester resin in the mixture A, uniformly mixing, and then adding the amino resin to obtain a mixture B; (3) slowly adding the effect pigment paste in the mixture B, uniformly mixing, and then adding the wetting agent to obtain a mixture C; (4) filtering the mixture C to obtain the water-based metal finish.

9. The production method according to claim 8, wherein In step (4), the filter hole diameter of the filtration is 100 μm-200 μm.

10. Application of the water-based metal finish of any one of claims 1-7 in construction equipment, home equipment, transportation equipment, industrial machinery equipment.

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