A coating composition for aluminum coils and its preparation method and application

Abstract

The present invention belongs to the technical field of coatings, and specifically relates to a coating composition for aluminum coils and a preparation method thereof. The raw materials of the coating composition include: boron-modified phenolic resin, silicone-modified polyester resin, blocked polyurethane resin, acrylic emulsion, sodium dodecylbenzene sulfonate, zinc phosphate, aluminum chloride, tributyl phosphate, defoamer, leveling agent, film-forming aid, adhesion promoter, pigment filler, cosolvent and water. The coating prepared by the present invention has strong adhesion to metal, chemical corrosion resistance and impact resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings, and in particular relates to a coating composition for aluminum coils, a preparation method thereof and an application thereof. Background Art

[0002] Aluminum coil coating is a process of applying coating to the surface of aluminum through roller coating, and then making color-coated aluminum sheet. It has the advantages of high mechanical strength, good flexibility and easy processing of aluminum sheet, and also has good decorative and corrosion resistance, and can be easily processed by punching, bending, deep drawing, etc. Due to its light weight, excellent performance and low price, it is widely used in various types of buildings such as industrial plants, stations, airports, gymnasiums, high-end buildings and home appliance manufacturing.

[0003] Due to the poor ductility of aluminum sheets, the base material is prone to cracking when bent, which requires high bending resistance of the coating. The aluminum coil coating must be subjected to high-temperature rapid baking during coating. When used, the coated plate must be unrolled and directly cut, bite and other mechanical processing. Therefore, the aluminum coil coating is required to have good stability, mechanical properties and excellent adhesion to the substrate. Some special products also require high-efficiency anti-fouling, antibacterial and anti-graffiti requirements. Especially its wear resistance, in the subsequent preparation process of the coil, its surface is often damaged due to wear, which affects the product quality.

[0004] Chinese invention patent application CN107652854A discloses a UV system aluminum coil coating, wherein the weight percentages of the components of the aluminum coil coating are: pentaerythritol tetraacrylate: 10-15%, trimethylolpropane triacrylate: 25-35%, E-20 epoxy resin dimethacrylate: 10-16%, diethylene glycol diacrylate: 20-30%, methyl propylene glycol diacrylate: 15-25%, photoinitiator 184: 1-3%, various color pigments: 2-10%, precipitated barium sulfate: 10-15%, polyethylene wax powder: 1-3%, wetting dispersant: 2-4%, defoamer: 1-2%, leveling agent: 2-5%, and inhibitor: 0.5-1.5%. The coating has the characteristics of energy saving and environmental protection, but has poor adhesion to metals.

[0005] Chinese invention patent application CN107652859A discloses a low-temperature curing water-based energy-saving aluminum coil coating, which comprises by weight: 70% water-based polyester resin 30-50%, 70% water-based polyurethane resin 25-50%, polyvinyl alcohol formal resin 4-8%, 717 amino resin 15-25%, various color pigments 2-8%, talc 0-10%, kaolin 0-5%, water-based bentonite 2-5%, water-based leveling agent 1-3%, water-based defoamer 0.5-1.5%, water-based dispersant 3-6%, substrate wetting agent 1-3%, drying accelerator 1-3%, water-based polyethylene wax emulsion 0.5-1.5%, Amp-951% and deionized water 8-20%. However, the anti-bending performance of the coating needs to be improved.

[0006] Chinese invention patent application CN105273581A achieves rapid curing (10 to 30 seconds) by changing the curing method and the formula of the powder coating. It also has excellent weather resistance and acid and alkali resistance. This is mainly because it uses fluorocarbon resin. However, the addition of fluorocarbon resin will affect the adhesion of the coating and the T-bend performance of the coating. For aluminum plates, which have higher coating requirements, this type of powder coating will result in poor T-bend performance and adhesion of the coating.

[0007] Chinese invention patent application CN111073471A discloses a coil coating for a velvet glittering surface veneer for aluminum coils, the coating comprising the following components and their weight percentages: environmentally friendly solvent: 5-10%; dispersant: 0.5-1%; catalyst: 0.5-1%; amino 5-10%; defoamer: 0.3-0.5%; adhesion agent: 0.5%-1.0%; leveling agent 0.3-3%; directional arrangement aid: 1-3%; antistatic aid: 0.5-1%; nano-level pearlescent slurry: 10-20%; polyester resin 50-70%; silane oligomer powder: 3%-6%; the coil coating of the invention has the advantages of good surface visual effect and a velvet glittering surface veneer for aluminum coils with a smooth feel. However, the coating is not resistant to high temperatures and has low bending resistance.

[0008] The existing aluminum coil coatings are not resistant to high temperatures, have poor adhesion to metals, are easily separated from metals after a period of time, and have low crosslinking density with metals. Therefore, it is necessary to develop an aluminum coil coating that is resistant to high temperatures, has good stability, excellent mechanical properties, and excellent adhesion to substrates. Summary of the invention

[0009] In view of the shortcomings of the prior art, the present invention provides a coating composition for aluminum coils, a preparation method thereof and an application thereof. The coating prepared by the present invention has strong adhesion to metals, good flexibility of the coating film and high cross-linking density, and excellent chemical corrosion resistance and heat resistance.

[0010] The present invention is achieved through the following technical solutions:

[0011] A coating composition for aluminum coils, the raw materials of the coating composition comprising: boron-modified phenolic resin, silicone-modified polyester resin, blocked polyurethane resin, acrylic emulsion, sodium dodecylbenzene sulfonate, zinc phosphate, aluminum chloride, tributyl phosphate, defoamer, leveling agent, film-forming aid, adhesion promoter, pigment filler, cosolvent and water.

[0012] Preferably, the raw materials of the coating composition include, by weight: 20-30 parts of boron-modified phenolic resin, 20-30 parts of silicone-modified polyester resin, 5-10 parts of blocked polyurethane resin, 3-6 parts of acrylic emulsion, 1-2 parts of sodium dodecylbenzene sulfonate, 0.5-2 parts of zinc phosphate, 0.5-2 parts of aluminum chloride, 1-3 parts of tributyl phosphate, 0.2-0.5 parts of defoaming agent, 0.2-0.5 parts of leveling agent, 0.1-0.4 parts of film-forming aid, 0.1-0.5 parts of adhesion promoter, 1-5 parts of pigment and filler, 1-5 parts of cosolvent and 20-30 parts of water.

[0013] Further preferably, the raw materials of the coating composition include, by weight: 25 parts of boron-modified phenolic resin, 25 parts of silicone-modified polyester resin, 8 parts of blocked polyurethane resin, 5 parts of acrylic emulsion, 1.5 parts of sodium dodecylbenzene sulfonate, 1 part of zinc phosphate, 1 part of aluminum chloride, 2 parts of tributyl phosphate, 0.3 parts of defoaming agent, 0.3 parts of leveling agent, 0.3 parts of film-forming aid, 0.2 parts of adhesion promoter, 4 parts of pigments and fillers, 4 parts of cosolvent and 25 parts of water.

[0014] Preferably, the defoaming agent is selected from one or more of organosiloxane, ethylene oxide, polyethylene wax, phosphate ester and mineral oil, preferably a mixture of ethylene oxide and polyethylene wax.

[0015] The leveling agent is selected from one or more of polyether siloxane, polyvinyl alcohol, acrylate and aldehyde ketone resin, preferably polyvinyl alcohol.

[0016] Preferably, the film-forming aid is selected from one or more of propylene glycol methyl ether acetate, benzyl alcohol, dodecyl alcohol ester and hexylene glycol butyl ether acetate, preferably propylene glycol methyl ether acetate; the color filler is selected from at least one of titanium dioxide, kaolin, diatomaceous earth, mica powder and cuprous oxide, preferably titanium dioxide.

[0017] Preferably, the adhesion promoter is selected from one or more of methyltrimethoxysilane, dimethyldiethoxysilane, methyltriethoxysilane and dimethyldimethoxysilane, preferably methyltrimethoxysilane; the cosolvent is selected from one or more of propylene glycol butyl ether, n-butanol, isobutanol, propylene glycol ethyl ether, isopropanol, diethylene glycol ethyl ether and diethylene glycol butyl ether.

[0018] Preferably, the solvent is a mixture of propylene glycol butyl ether and n-butanol, and the mass ratio of the propylene glycol butyl ether to n-butanol is 2-3:1.

[0019] The present invention also relates to a method for preparing the coating composition, comprising the following steps:

[0020] (1) mixing a boron-modified phenolic resin, a silicone-modified polyester resin, a blocked polyurethane resin and an acrylic emulsion, and stirring to obtain a mixture 1;

[0021] (2) adding sodium dodecylbenzene sulfonate, zinc phosphate, aluminum chloride, tributyl phosphate and a cosolvent to the mixture 1, and stirring to obtain a mixture 2;

[0022] (3) Add a defoamer, a leveling agent, a film-forming aid, an adhesion promoter and a pigment and filler into the mixture 2, add water and stir to obtain the coating composition.

[0023] Preferably, the stirring speed in step (1) is 800-1200 rpm, and the stirring time is 30-50 min; the stirring speed in step (2) is 1200-1500 rpm, and the stirring time is 10-20 min; the stirring speed in step (3) is 600-800 rpm, and the stirring time is 20-40 min.

[0024] The invention also relates to the application of the coating composition in coating.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The coating prepared by the various components and proportions of the present invention has strong adhesion to metals and is resistant to chemical corrosion and impact;

[0027] (2) The boron-modified phenolic resin, the silicone-modified polyester resin and the blocked polyurethane resin used in combination in the present invention have a significant synergistic effect, and the performance in terms of impact resistance, solvent resistance and T-bend properties is significantly improved;

[0028] (3) The present invention uses a specific surfactant sodium dodecylbenzene sulfonate, which is unexpectedly found to have a synergistic effect with tributyl phosphate. The simultaneous use of the two can improve the quality of the coating to a limited extent. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with specific embodiments, and the advantages and features of the present invention will become clearer as the description proceeds. However, these embodiments are exemplary only and do not constitute any limitation to the scope of the present invention. It should be understood by those skilled in the art that the details and forms of the technical solution of the present invention may be modified or replaced without departing from the spirit and scope of the present invention, but these modifications and replacements all fall within the scope of protection of the present invention.

[0030] Silicone-modified polyester resin, model: AD-1681, purchased from Dongguan Aide Synthetic Materials Co., Ltd.;

[0031] Blocked polyurethane resin, model: HY-1000F, purchased from Foshan Huiyou New Material Technology Co., Ltd.;

[0032] Boron-modified phenolic resin, product number: HK boron-modified phenolic resin 188M, purchased from Jining Huakai Resin Co., Ltd.;

[0033] Acrylic emulsion, model: KDD MR700, purchased from Shanghai Kaiyin Chemical Co., Ltd.;

[0034] Polyethylene wax, model: Clariant Ceridust Polyethylene wax 9615A

[0035] Polyvinyl alcohol, model: 080-44, brand: China Petrochemical Group Chongqing Chuanwei Chemical Co., Ltd., purchased from Shanghai Kaiyin Chemical Co., Ltd.;

[0036] The reagents not specifically described below are all common reagents in the art and are commercially available, and their sources are not specifically limited.

[0037] Example 1

[0038] A coating composition for aluminum coils, comprising the following raw materials, by weight: 25 parts of boron-modified phenolic resin, 25 parts of organosilicon-modified polyester resin, 8 parts of blocked polyurethane resin, 5 parts of acrylic emulsion, 1.5 parts of sodium dodecylbenzene sulfonate, 1 part of zinc phosphate, 1 part of aluminum chloride, 2 parts of tributyl phosphate, 0.3 parts of defoamer, 0.3 parts of leveling agent, 0.3 parts of film-forming aid, 0.2 parts of adhesion promoter, 4 parts of pigment and filler, 4 parts of cosolvent and 25 parts of water.

[0039] The defoaming agent is a mixture of ethylene oxide and polyethylene wax in a mass ratio of 1:1; the leveling agent is polyvinyl alcohol; the film-forming aid is propylene glycol methyl ether acetate; the color filler is titanium dioxide; the adhesion promoter is methyl trimethoxy silane; and the cosolvent is propylene glycol butyl ether and n-butanol in a mass ratio of 2.5:1.

[0040] Preparation method of the above coating composition:

[0041] (1) mixing a boron-modified phenolic resin, a silicone-modified polyester resin, a blocked polyurethane resin and an acrylic emulsion, and stirring at 1000 rpm for 30 min to obtain a mixture 1;

[0042] (2) adding sodium dodecylbenzene sulfonate, zinc phosphate, aluminum chloride, tributyl phosphate and solvent under stirring, and stirring at 1200 rpm for 10 min to obtain a mixture 2;

[0043] (3) A defoamer, a leveling agent, a film-forming aid, and an adhesion promoter were added to the mixture 2, and water was added to adjust the viscosity. The mixture was stirred at 700 rpm for 30 min to obtain the coating composition.

[0044] Example 2

[0045] A coating composition for aluminum coils comprises the following raw materials, measured by weight: 20 parts of zinc borate-modified phenolic resin, 20 parts of organosilicon-modified polyester resin, 5 parts of blocked polyurethane resin, 3 parts of acrylic emulsion, 1 part of sodium dodecylbenzene sulfonate, 0.5 parts of zinc phosphate, 0.5 parts of aluminum chloride, 1 part of tributyl phosphate, 0.2 parts of defoaming agent, 0.2 parts of leveling agent, 0.1 parts of film-forming aid, 0.1 parts of adhesion promoter, 1 part of cosolvent and 20 parts of water.

[0046] The defoaming agent is a mixture of ethylene oxide and polyethylene wax in a mass ratio of 1:1; the leveling agent is polyvinyl alcohol; the film-forming aid is propylene glycol methyl ether acetate; the color filler is titanium dioxide; the adhesion promoter is methyl trimethoxy silane; and the cosolvent is propylene glycol butyl ether and n-butanol in a mass ratio of 2:1.

[0047] Preparation method of the above coating composition:

[0048] (1) mixing a boron-modified phenolic resin, a silicone-modified polyester resin, a blocked polyurethane resin and an acrylic emulsion, and stirring at 800 rpm for 50 min to obtain a mixture 1;

[0049] (2) adding sodium dodecylbenzene sulfonate, zinc phosphate, aluminum chloride, tributyl phosphate and solvent under stirring, and stirring at 1000 rpm for 20 min to obtain a mixture 2;

[0050] (3) A defoamer, a leveling agent, a film-forming aid, and an adhesion promoter were added to the mixture 2, and water was added to adjust the viscosity. The mixture was stirred at 600 rpm for 40 minutes to obtain the coating composition.

[0051] Example 3

[0052] A coating composition for aluminum coils comprises the following raw materials, measured by weight: 30 parts of zinc borate-modified phenolic resin, 30 parts of organosilicon-modified polyester resin, 10 parts of blocked polyurethane resin, 6 parts of acrylic emulsion, 2 parts of sodium dodecylbenzene sulfonate, 2 parts of zinc phosphate, 2 parts of aluminum chloride, 3 parts of tributyl phosphate, 0.5 parts of defoaming agent, 0.5 parts of leveling agent, 0.4 parts of film-forming aid, 0.5 parts of adhesion promoter, 5 parts of cosolvent and 30 parts of water.

[0053] The defoaming agent is a mixture of ethylene oxide and polyethylene wax in a mass ratio of 1:1; the leveling agent is polyvinyl alcohol; the film-forming aid is propylene glycol methyl ether acetate; the color filler is titanium dioxide; the adhesion promoter is methyl trimethoxy silane; and the cosolvent is propylene glycol butyl ether and n-butanol in a mass ratio of 3:1.

[0054] Preparation method of the above coating composition:

[0055] (1) mixing a boron-modified phenolic resin, a silicone-modified polyester resin, a blocked polyurethane resin and an acrylic emulsion, and stirring at 1200 rpm for 40 min to obtain a mixture 1;

[0056] (2) adding sodium dodecylbenzene sulfonate, zinc phosphate, aluminum chloride, tributyl phosphate and solvent under stirring, and stirring at 1500 rpm for 10 min to obtain a mixture 2;

[0057] (3) Add defoaming agent, leveling agent, film-forming aid and adhesion promoter to mixture 2, add water to adjust viscosity, and stir at 800 rpm for 20 min to obtain the coating composition.

[0058] Comparative Example 1

[0059] A coating composition for aluminum coils, which differs from Example 1 only in that: 58 parts of boron-modified phenolic resin, 0 parts of organosilicon-modified polyester resin, and 0 parts of blocked polyurethane resin.

[0060] Comparative Example 2

[0061] A coating composition for aluminum coils, which differs from Example 1 only in that: 0 parts of boron-modified phenolic resin, 37.5 parts of silicone-modified polyester resin, and 20.5 parts of blocked polyurethane resin.

[0062] Comparative Example 3

[0063] A coating composition for aluminum coils, which differs from Example 1 only in that: 25 parts of boron-modified phenolic resin, 32 parts of organosilicon-modified polyester resin, and 0 parts of blocked polyurethane resin.

[0064] Comparative Example 4

[0065] A coating composition for aluminum coils, which differs from Example 1 only in that: 25 parts of boron-modified phenolic resin, 0 parts of organosilicon-modified polyester resin, and 32 parts of blocked polyurethane resin.

[0066] Comparative Example 5

[0067] A coating composition for aluminum coils, which differs from Example 1 only in that: 3.5 parts of sodium dodecylbenzene sulfonate and 0 parts of tributyl phosphate.

[0068] Comparative Example 6

[0069] A coating composition for aluminum coils, which differs from Example 1 only in that: 0 parts of sodium dodecylbenzene sulfonate and 3.5 parts of tributyl phosphate.

[0070] Comparative Example 7

[0071] A coating composition for aluminum coil, which differs from Example 1 only in that: the raw material ratio is different, including 10 parts of boron-modified phenolic resin, 40 parts of silicone-modified polyester resin, 10 parts of blocked polyurethane resin, 10 parts of acrylic emulsion, 4 parts of sodium dodecylbenzene sulfonate, 3 parts of zinc phosphate, 1 part of aluminum chloride, 2 parts of tributyl phosphate, 0.3 parts of defoamer, 0.3 parts of leveling agent, 0.3 parts of film-forming aid, 0.2 parts of adhesion promoter, 4 parts of pigment and filler, 4 parts of cosolvent and 25 parts of water.

[0072] Comparative Example 8

[0073] A coating composition for aluminum coil, which differs from Example 1 only in that: the raw material ratio is different, including 35 parts of boron-modified phenolic resin, 15 parts of silicone-modified polyester resin, 20 parts of blocked polyurethane resin, 5 parts of acrylic emulsion, 1.5 parts of sodium dodecylbenzene sulfonate, 1 part of zinc phosphate, 1 part of aluminum chloride, 2 parts of tributyl phosphate, 0.3 parts of defoamer, 0.3 parts of leveling agent, 0.3 parts of film-forming aid, 0.2 parts of adhesion promoter, 4 parts of pigment and filler, 4 parts of cosolvent and 25 parts of water.

[0074] Comparative Example 9

[0075] A coating composition for aluminum coils, which is different from Example 1 only in that zinc phosphate and aluminum chloride are not added.

[0076] Effect test

[0077] The coating compositions prepared in Examples 1-3 and Comparative Examples 1-8 were coated on coiled aluminum plates using a two-coat-one-bake coating process with a thickness of 60-100 μm and the following performance tests were performed:

[0078] The appearance was evaluated by visual inspection; the pencil hardness was tested according to GB / T 6739-2006; the impact performance was tested according to GB / T1732-2020; the 1000h xenon lamp aging test was tested according to GB / T 1865-2009; the solvent resistance (MEK) was tested according to GB / T 13448-2019; the T-bend performance was tested according to GB / T 13448-2019; the acid and alkali resistance was tested according to GB 9274-1988; the salt spray resistance test was tested according to GB / T 1771-2007; the adhesion ability test method: the adhesion test was tested according to ASTM D3359-2008 test method B, and the evaluation was based on a scale of 0-5, where a score of "0" indicates no adhesion failure and a score of "5" indicates that the film is completely separated from the substrate. The acid and alkali resistance was tested according to GB 9274-1988. The test results are shown in Table 1.

[0079] Table 1 Test results

[0080]

[0081] The above detailed description is a specific description of one feasible embodiment of the present invention. The embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not deviate from the present invention should be included in the scope of the technical solution of the present invention.

Claims

1. A coating composition for aluminum coil, characterized in that: The raw materials of the coating composition include, by weight: 20-30 parts of boron-modified phenolic resin, 20-30 parts of silicone-modified polyester resin, 5-10 parts of blocked polyurethane resin, 3-6 parts of acrylic emulsion, 1-2 parts of sodium dodecylbenzene sulfonate, 0.5-2 parts of zinc phosphate, 0.5-2 parts of aluminum chloride, 1-3 parts of tributyl phosphate, 0.2-0.5 parts of defoaming agent, 0.2-0.5 parts of leveling agent, 0.1-0.4 parts of film-forming aid, 0.1-0.5 parts of adhesion promoter, 1-5 parts of pigment and filler, 1-5 parts of cosolvent and 20-30 parts of water.

2. The coating composition according to claim 1, characterized in that The raw materials of the coating composition include, by weight: 25 parts of boron-modified phenolic resin, 25 parts of silicone-modified polyester resin, 8 parts of blocked polyurethane resin, 5 parts of acrylic emulsion, 1.5 parts of sodium dodecylbenzene sulfonate, 1 part of zinc phosphate, 1 part of aluminum chloride, 2 parts of tributyl phosphate, 0.3 parts of defoaming agent, 0.3 parts of leveling agent, 0.3 parts of film-forming aid, 0.2 parts of adhesion promoter, 4 parts of pigment and filler, 4 parts of cosolvent and 25 parts of water.

3. The coating composition according to claim 1, characterized in that The defoaming agent is selected from one or more of organic siloxane, ethylene oxide, polyethylene wax and mineral oil; the leveling agent is selected from one or more of polyether siloxane, polyvinyl alcohol, acrylate and aldehyde-ketone resin.

4. The coating composition according to claim 1, characterized in that The film-forming aid is selected from one or more of propylene glycol methyl ether acetate, benzyl alcohol, dodecyl alcohol ester and hexylene glycol butyl ether acetate; the pigment filler is selected from at least one of titanium dioxide, kaolin, diatomaceous earth, mica powder and cuprous oxide.

5. The coating composition according to claim 1, characterized in that The adhesion promoter is selected from one or more of methyltrimethoxysilane, dimethyldiethoxysilane, methyltriethoxysilane and dimethyldimethoxysilane; the cosolvent is selected from one or more of propylene glycol butyl ether, n-butanol, isobutanol, propylene glycol ethyl ether, isopropanol, diethylene glycol ethyl ether and diethylene glycol butyl ether.

6. The coating composition according to claim 1, characterized in that The solvent is a mixture of propylene glycol butyl ether and n-butanol, and the mass ratio of the propylene glycol butyl ether to n-butanol is 2-3:

1.

7. A method for preparing the coating composition according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) mixing a boron-modified phenolic resin, a silicone-modified polyester resin, a blocked polyurethane resin and an acrylic emulsion, and stirring to obtain a mixture 1; (2) adding sodium dodecylbenzene sulfonate, zinc phosphate, aluminum chloride, tributyl phosphate and a cosolvent to the mixture 1, and stirring to obtain a mixture 2; (3) Add a defoamer, a leveling agent, a film-forming aid, an adhesion promoter and a pigment and filler into the mixture 2, add water and stir to obtain the coating composition.

8. The preparation method according to claim 7, characterized in that: The stirring speed in step (1) is 800-1200 rpm, and the stirring time is 30-50 min; the stirring speed in step (2) is 1200-1500 rpm, and the stirring time is 10-20 min; the stirring speed in step (3) is 600-800 rpm, and the stirring time is 20-40 min.

9. Use of the coating composition according to any one of claims 1 to 6 in coating.

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