Boiling-resistant aluminum material powder coating and preparation method thereof

Abstract

The invention discloses a boiling-resistant aluminum material powder coating and a preparation method thereof, and relates to the technical field of powder coatings. The boiling-resistant aluminum material powder coating is prepared from 135 to 160 parts of binder, 5 to 16 parts of curing agent, 0.3 to 0.6 part of benzoin, 0.8 to 1.2 parts of flatting agent, 1.6 to 2.6 parts of dispersing agent and 50 to 80 parts of pigment filler. Wherein the binder comprises carboxyl-terminated polyester resin, epoxypropyl methacrylate and carboxyl acrylic resin, and the binder is formed by mixing epoxypropyl methacrylate and a small amount of carboxyl acrylic resin in the carboxyl-terminated polyester resin, so that the boiling resistance of the powder coating can be effectively improved; according to the present invention, the powder coating can maintain the good weather resistance, the surface hardness of the coating can be improved, and the wear resistance and the scratch resistance of the coating can be further improved, such that the service life of the powder coating when the powder coating is used outdoors can be easily prolonged, and the powder coating can be more suitable for the surface treatment of the outdoor aluminum profile.

Description

Technical Field

[0001] The invention relates to the technical field of powder coatings, in particular to a boiling-resistant aluminum powder coating and a preparation method thereof. Background Art

[0002] Aluminum profiles are the main structural materials for doors, windows and curtain walls today, and have been widely used around the world. Since aluminum alloy extruded profiles without surface treatment have a single appearance and are prone to corrosion, aluminum profiles are generally surface treated to meet the requirements of high decorativeness and strong weather resistance of building materials. According to the process method, the current aluminum profile surface treatment technology can be divided into three categories: anodizing, anodizing-electrophoresis, and powder coating. Among them, powder coating is a surface treatment method that uses powder coating to form a coating on the surface of aluminum profiles and provides all-round protection for aluminum profiles. Due to the simple processing process and low cost of powder coating, the coating is strong and durable after treatment, and has good chemical resistance, powder coating accounts for a large proportion of aluminum profile surface treatment on the current market.

[0003] However, since aluminum profiles are often used for outdoor painting and decoration, and are often exposed to the sun and rain, some powder coatings with poor water resistance and weather resistance are prone to surface loss of gloss, coating bubbles, large color changes and other problems under long-term direct sunlight or rain erosion, which will seriously affect the service life of powder coatings and aluminum profiles. Therefore, improving the formula of powder coatings and further improving the water boiling resistance and weather resistance of powder coatings is of great significance for the surface treatment of aluminum profiles. Summary of the invention

[0004] In order to improve the boiling water resistance of powder coatings and further increase the service life of powder coatings when used outdoors, the present application provides a boiling water resistant aluminum powder coating and a preparation method thereof.

[0005] In the first aspect, the present application provides a boiling-resistant aluminum powder coating that adopts the following technical solution: A boiling resistant powder coating comprises the following raw materials in parts by weight: Binder: 135-160 parts; Curing agent: 5-16 parts; Benzoin: 0.3-0.6 parts; Leveling agent: 0.8-1.2 parts; Dispersant: 1.6-2.6 parts; Pigments and fillers: 50-80 parts; Wherein, the binder comprises a carboxyl-terminated polyester resin, glycidyl methacrylate and a carboxyl acrylic resin, the weight ratio of the carboxyl-terminated polyester resin, the glycidyl methacrylate and the carboxyl acrylic resin is 10:(2.5-4):(0.1-1), and the acid value of the carboxyl-terminated polyester resin is 40-60 mgKOH / g; The curing agent includes one of triglycidyl isocyanurate or β-hydroxyalkylamide.

[0006] By adopting the above technical scheme, glycidyl methacrylate and a small amount of carboxyl acrylic resin are mixed in the carboxyl-terminated polyester resin, which is not only conducive to improving the boiling resistance of the powder coating, so that the coating surface can still maintain a certain gloss after being immersed in boiling water for a long time, and has a high gloss retention rate, but also the carboxyl acrylic resin can make up for the weather resistance reduced by the addition of glycidyl methacrylate, which is conducive to making the powder coating have good weather resistance, and at the same time, it can also improve the surface hardness of the coating, which is conducive to improving the wear and scratch resistance of the coating. Therefore, the service life of the powder coating when applied outdoors can be further improved, making the powder coating more suitable for the surface treatment of outdoor aluminum profiles.

[0007] Optionally, the mixing weight ratio of the carboxyl-terminated polyester resin, the glycidyl methacrylate and the carboxyl acrylic resin is 10:(3.5-3.7):(0.3-0.5).

[0008] By adopting the above technical scheme, when the mixing weight ratio of the terminal carboxyl polyester resin, glycidyl methacrylate and carboxyl acrylic resin in the binder is within the range of 10:(3.5-3.7):(0.3-0.5), not only can the boiling resistance of the powder coating be improved by an appropriate amount of glycidyl methacrylate, but also the weather resistance and surface hardness of the powder coating can be improved by an appropriate amount of carboxyl acrylic resin, thereby preventing the weather resistance of the powder coating from being affected by the addition of glycidyl methacrylate, and helping the powder coating to have better comprehensive performance, so that the powder coating is more suitable for the surface treatment of outdoor aluminum profiles.

[0009] Optionally, the acid value of the carboxyl acrylic resin is 50-53.5 mgKOH / g.

[0010] By adopting the above technical scheme, the acid value of the carboxyl acrylic resin is controlled within the range of 50-53.5 mgKOH / g, which is beneficial for the coating formed by the powder coating to have good weather resistance and surface hardness. At the same time, it can also prevent the curing reaction of the terminal carboxyl polyester resin from being affected by the excessively high acid value of the carboxyl acrylic resin, so that the adhesive can be fully cured.

[0011] Optionally, the carboxyl-terminated polyester resin is a stearic acid-modified carboxyl-terminated polyester resin, and the modification step of the stearic acid-modified carboxyl-terminated resin comprises: The carboxyl-terminated polyester resin and stearic acid are mixed and dissolved by N,N-dimethylformamide, and then p-toluenesulfonic acid is added, and the mixture is heated to 125-135°C for reaction for 3-4 hours, and then vacuumed to continue the reaction for 12-18 hours. After cooling to room temperature, the pH value is adjusted to 4.5-7, and ethanol is used for precipitation and filtration. The filter residue is vacuum dried and then high-speed crushed to obtain a stearic acid-modified carboxyl-terminated polyester resin.

[0012] By adopting the above technical solution, stearic acid can fully react with the residual hydroxyl groups in the carboxyl-terminated polyester resin to undergo an esterification reaction, thereby reducing the influence of the hydroxyl groups in the carboxyl-terminated polyester resin on the boiling resistance of the coating, which is beneficial to further improve the boiling resistance of the powder coating. Secondly, after the carboxyl-terminated polyester resin is modified by stearic acid, a long-chain stearic acid group is introduced into the carboxyl-terminated polyester resin, which can effectively reduce the melt viscosity of the powder coating, thereby facilitating the improvement of the fluidity of the powder coating during melt solidification, so that the powder coating can form a uniform and smooth powder coating.

[0013] Optionally, the curing agent includes β-hydroxyalkylamide.

[0014] By adopting the above technical scheme, in the binder system of terminal carboxyl polyester resin-glycidyl methacrylate-carboxylic acrylic resin, when β-hydroxyalkylamide is used as a curing agent, not only the amount of addition is less, but also the formed coating has better weather resistance, color uniformity and surface hardness. At the same time, the toxicity classification of β-hydroxyalkylamide is approximately non-toxic and non-irritating, which has a certain environmental significance compared with the use of triglycidyl isocyanurate as a curing agent, and meets the environmental protection policy requirements of many countries.

[0015] Optionally, the curing agent also includes dicyandiamide, and the mixing weight ratio of the β-hydroxyalkylamide to the dicyandiamide is 1:(0.08-0.12).

[0016] By adopting the above technical solution, not only can the boiling water resistance of the powder coating be improved, but also the powder coating can have good weather resistance, which is beneficial to prolonging the service life of the powder coating when used outdoors.

[0017] Optionally, the dispersant is a mixture of silane coupling agent KH550 and silane coupling agent KH570, and the mixing weight ratio of the silane coupling agent KH550 to the silane coupling agent KH570 is (0.22-0.3):1.

[0018] By adopting the above technical scheme, since the binder includes not only terminal carboxyl polyester resin but also glycidyl methacrylate and carboxyl acrylic resin, the silane coupling agent KH550 as aminosilane and the silane coupling agent KH570 as acyloxysilane are mixed with each other and mixed in a weight ratio of (0.22-0.3):1, which is beneficial to improve the dispersion performance of the pigment and filler in the binder, so that the pigment and filler can be evenly dispersed in the coating.

[0019] Optionally, the color filler includes bentonite, barium sulfate, rutile titanium dioxide and inorganic pigments, and the mixing weight ratio of the bentonite, the barium sulfate, the rutile titanium dioxide and the inorganic pigment is 1: (22.5-35): (1.5-3.5): (0.5-0.8).

[0020] By adopting the above technical scheme, bentonite has good heat resistance and is also beneficial to improving the smoothness and fineness of the powder coating; barium sulfate can increase the water resistance and leveling property of the coating, which is not only beneficial to improving the water boiling resistance of the coating, but also beneficial to the powder coating to form a coating with a smooth surface; rutile titanium dioxide can improve the covering power and weather resistance of the coating, and can also improve the color retention rate of the inorganic pigment; the inorganic pigment has the characteristics of sun resistance, heat resistance, weather resistance and strong covering power. When the mixed weight ratio of bentonite, barium sulfate, rutile titanium dioxide and inorganic pigment is within the range of 1: (22.5-35): (1.5-3.5): (0.5-0.8), it is beneficial for the powder coating to form a powder coating with good water boiling resistance and weather resistance, uniform color, high gloss and color retention rate.

[0021] Optionally, the leveling agent is a polyether-modified organic silicon compound.

[0022] By adopting the above technical scheme, the polyether-modified silicone compound can be fully mixed in the binder system of terminal carboxyl polyester resin-glycidyl methacrylate-carboxyl acrylic resin, which can effectively improve the melt fluidity of the powder coating, thereby facilitating the powder coating to form a uniform and smooth coating.

[0023] In the second aspect, the present application provides a method for preparing a boiling-resistant aluminum powder coating, which adopts the following technical scheme: A method for preparing a boiling-resistant aluminum powder coating, comprising the following steps: S1, stirring and mixing the carboxyl-terminated polyester resin and the glycidyl methacrylate in proportion at 130-150° C., after the mixture is uniformly mixed, after the temperature is raised to the range of 160-175° C., adding the carboxyl acrylic resin, and continuing to stir and mix at the same temperature, after the mixture is uniformly mixed, extruding and granulating to obtain a binder; S2. After uniformly mixing the binder, curing agent, benzoin, leveling agent, dispersant, pigment and filler, etc., the mixture is melt-extruded, tableted, crushed, and sieved to obtain a powder coating.

[0024] By adopting the above technical solution, the preparation of powder coating has the characteristics of simple steps and convenient operation, and is also conducive to the full mixing of the binder so that the coating formed by the powder coating can be uniformly cured.

[0025] In summary, the technical solution of this application has at least one of the following beneficial effects: 1. By mixing glycidyl methacrylate and a small amount of carboxyl acrylic resin into the carboxyl-terminated polyester resin, it is not only beneficial to improve the water boiling resistance of the powder coating, but also to keep the powder coating in good weather resistance. At the same time, it is beneficial to improve the surface hardness of the coating, further improve the wear and scratch resistance of the coating, and help to increase the service life of the powder coating when used outdoors.

[0026] 2. By using β-hydroxyalkylamide as a curing agent and mixing it with dicyandiamide, not only can the boiling water resistance of the powder coating be improved, but also the powder coating has good weather resistance, which is beneficial to increase the service life of the powder coating when used outdoors. DETAILED DESCRIPTION

[0027] The present application is further described in detail below with reference to embodiments and comparative examples. Example

[0028] [Example 1] A boiling-resistant aluminum powder coating, comprising the following raw materials: 140kg of adhesive, 16kg of curing agent, 0.5kg of benzoin, 1kg of leveling agent, 2.2kg of dispersant and 63.2kg of pigments and fillers.

[0029] Specifically, the binder includes a mixture of carboxyl-terminated polyester resin, glycidyl methacrylate and carboxyl acrylic resin. The weight ratio of carboxyl-terminated polyester resin, glycidyl methacrylate and carboxyl acrylic resin is 10:3:1, that is, the amount of carboxyl-terminated polyester resin added is 100kg, the amount of glycidyl methacrylate added is 30kg, and the amount of carboxyl acrylic resin added is 10kg. Specifically, the carboxyl-terminated polyester resin is purchased from Huachang Chemical, and the acid value is 58.1mgKOH / mg; the acid value of the carboxyl acrylic resin is 44.2mgKOH / mg.

[0030] Specifically, the curing agent is triglycidyl isocyanurate; the leveling agent is a polyether modified silicone compound, the specific brand is BYK-320; the dispersant is a mixture of silane coupling agent KH550 and silane coupling agent KH570, wherein the mixing weight ratio of silane coupling agent KH550 to silane coupling agent KH570 is 0.22:1, that is, the addition amount of silane coupling agent KH550 is 0.4kg, and the addition amount of silane coupling agent KH570 is 1.8kg; the color filler includes 2kg of bentonite, 54kg of barium sulfate, 6kg of titanium dioxide and 1.2kg of inorganic pigment, wherein the inorganic pigment is specifically cobalt blue with a particle size range of 20-30nm.

[0031] The preparation method of a boiling-resistant aluminum powder coating in this embodiment comprises the following steps: S1. Put the carboxyl-terminated polyester resin and glycidyl methacrylate into a reactor, heat the temperature to 140°C, stir at a speed of 200 r / min for 20 min, then raise the temperature of the reactor to 170°C, add the carboxyl acrylic resin, continue stirring and reacting at a speed of 400 r / min for 30 min, and finally transfer the mixed material to a screw extruder for extrusion granulation to obtain a binder; S2. Various raw materials such as binder, curing agent, benzoin, leveling agent, dispersant and pigment filler are put into a reactor, stirred for 30 minutes at a temperature of 120°C and a stirring speed of 400r / min, and then the evenly mixed materials are transferred to a screw extruder, the screw speed is controlled at 15r / min, and the extrusion temperature is controlled at 145°C for melt extrusion, tableting, crushing, screening, and powder coating is obtained.

[0032] [Example 2] A boiling-resistant aluminum powder coating, comprising the following raw materials: 160kg of adhesive, 6.8kg of curing agent, 0.6kg of benzoin, 1.2kg of leveling agent, 2.6kg of dispersant and 80kg of pigments and fillers.

[0033] Specifically, the binder includes a mixture of carboxyl-terminated polyester resin, glycidyl methacrylate and carboxyl acrylic resin. Among them, the weight ratio of carboxyl-terminated polyester resin, glycidyl methacrylate and carboxyl acrylic resin is 10:2.5:0.3, that is, the addition amount of carboxyl-terminated polyester resin is 125kg, the addition amount of glycidyl methacrylate is 31.25kg, and the addition amount of carboxyl acrylic resin is 3.75kg. Specifically, the carboxyl-terminated polyester resin is purchased from Huachang Chemical, and the acid value is 58.1mgKOH / mg; the acid value of the carboxyl acrylic resin is 44.2mgKOH / mg.

[0034] Specifically, the curing agent is β-hydroxyalkylamide; the leveling agent is a polyether modified silicone compound, the specific brand is BYK-320; the dispersant is a mixture of silane coupling agent KH550 and silane coupling agent KH570, wherein the mixing weight ratio of silane coupling agent KH550 to silane coupling agent KH570 is 0.3:1, that is, the addition amount of silane coupling agent KH550 is 0.6kg, and the addition amount of silane coupling agent KH570 is 2kg; the color filler includes 2kg of bentonite, 70kg of barium sulfate, 7kg of titanium dioxide and 1kg of inorganic pigment, wherein the inorganic pigment is specifically cobalt blue with a particle size range of 20-30nm.

[0035] In addition, a method for preparing a boiling-resistant aluminum powder coating in this embodiment includes the following steps: S1, put the carboxyl-terminated polyester resin and glycidyl methacrylate into a reactor, heat the temperature to 130°C, stir at a speed of 200r / min for 30min, then raise the temperature of the reactor to 175°C, add the carboxyl acrylic resin, continue stirring and reacting at a speed of 400r / min for 20min, and finally transfer the mixed material to a screw extruder for extrusion granulation to obtain a binder; S2. Various raw materials such as binder, curing agent, benzoin, leveling agent, dispersant and pigment filler are put into a reactor, stirred for 30 minutes at a temperature of 120°C and a stirring speed of 400r / min, and then the evenly mixed materials are transferred to a screw extruder, the screw speed is controlled at 15r / min, and the extrusion temperature is controlled at 140°C for melt extrusion, tableting, crushing, screening, and obtaining powder coating.

[0036] [Example 3] A boiling-resistant aluminum powder coating, comprising the following raw materials: 135kg of adhesive, 5.6kg of curing agent, 0.3kg of benzoin, 0.8kg of leveling agent, 2kg of dispersant and 51.6kg of pigments and fillers.

[0037] Specifically, the binder includes a mixture of carboxyl-terminated polyester resin, glycidyl methacrylate and carboxyl acrylic resin. Among them, the weight ratio of carboxyl-terminated polyester resin, glycidyl methacrylate and carboxyl acrylic resin is 10:4:1, that is, the addition amount of carboxyl-terminated polyester resin is 90kg, the addition amount of glycidyl methacrylate is 36kg, and the addition amount of carboxyl acrylic resin is 9kg. Specifically, the carboxyl-terminated polyester resin is purchased from Huachang Chemical, and the acid value is 58.1mgKOH / mg; the acid value of the carboxyl acrylic resin is 53.5mgKOH / mg.

[0038] Specifically, the curing agent is a mixed curing agent of β-hydroxyalkylamide and dicyandiamide, and the mixing weight ratio of β-hydroxyalkylamide to dicyandiamide is 1:0.24, that is, the added amount of β-hydroxyalkylamide is 4.52 kg, and the added amount of dicyandiamide is 1.08 kg.

[0039] Specifically, the leveling agent is a polyether modified organic silicon compound, and the specific brand is BYK-320; the dispersant is a mixture of silane coupling agent KH550 and silane coupling agent KH570, wherein the mixing weight ratio of silane coupling agent KH550 to silane coupling agent KH570 is 0.25:1, that is, the addition amount of silane coupling agent KH550 is 0.4kg, and the addition amount of silane coupling agent KH570 is 1.6kg; the color filler includes 2kg of bentonite, 45kg of barium sulfate, 3kg of titanium dioxide and 1.6kg of inorganic pigment, wherein the inorganic pigment is specifically cobalt blue with a particle size range of 20-30nm.

[0040] In addition, a method for preparing a boiling-resistant aluminum powder coating in this embodiment includes the following steps: S1. Put the carboxyl-terminated polyester resin and glycidyl methacrylate into a reactor, heat the temperature to 150° C., stir at a speed of 200 r / min for 20 min, then raise the temperature of the reactor to 160° C., add the carboxyl acrylic resin, continue stirring and reacting at a speed of 400 r / min for 25 min, and finally transfer the mixed material to a screw extruder for extrusion granulation to obtain a binder; S2. Various raw materials such as binder, curing agent, benzoin, leveling agent, dispersant and pigment filler are put into a reactor, stirred for 30 minutes at a temperature of 120°C and a stirring speed of 400r / min, and then the evenly mixed materials are transferred to a screw extruder, the screw speed is controlled at 15r / min, and the extrusion temperature is controlled at 140°C for melt extrusion, tableting, crushing, screening, and obtaining powder coating.

[0041] [Example 4] A water-boiling resistant aluminum powder coating, which differs from [Example 1] in that the weight ratios of the terminal carboxyl polyester resin, glycidyl methacrylate and carboxyl acrylic resin in the binder are different.

[0042] In this embodiment, the weight ratio of the terminal carboxyl polyester resin, glycidyl methacrylate and carboxyl acrylic resin is 10:3.5:0.5, that is, the added amount of the terminal carboxyl polyester resin is 100 kg, the added amount of glycidyl methacrylate is 35 kg, and the added amount of the carboxyl acrylic resin is 5 kg.

[0043] [Example 5] A water-boiling resistant aluminum powder coating, which differs from [Example 1] in that the weight ratios of the terminal carboxyl polyester resin, glycidyl methacrylate and carboxyl acrylic resin in the binder are different.

[0044] In this embodiment, the weight ratio of the terminal carboxyl polyester resin, glycidyl methacrylate and carboxyl acrylic resin is 10:3.7:0.3, that is, the added amount of the terminal carboxyl polyester resin is 100 kg, the added amount of glycidyl methacrylate is 37 kg, and the added amount of the carboxyl acrylic resin is 3 kg.

[0045] [Example 6] A water-boiling resistant aluminum powder coating, which differs from [Example 1] in that the weight ratios of the terminal carboxyl polyester resin, glycidyl methacrylate and carboxyl acrylic resin in the binder are different.

[0046] In this embodiment, the weight ratio of the terminal carboxyl polyester resin, glycidyl methacrylate and carboxyl acrylic resin is 10:39:0.1, that is, the added amount of the terminal carboxyl polyester resin is 100 kg, the added amount of glycidyl methacrylate is 39 kg, and the added amount of the carboxyl acrylic resin is 1 kg.

[0047] [Example 7] A water-boiling-resistant aluminum powder coating, which differs from [Example 5] in that the acid value of the carboxyl acrylic resin in the binder is different.

[0048] In this embodiment, the acid value of the carboxyl acrylic resin in the binder is 53.5 mgKOH / mg.

[0049] [Example 8] A water-boiling-resistant aluminum powder coating, which differs from [Example 5] in that the acid value of the carboxyl acrylic resin in the binder is different.

[0050] In this embodiment, the acid value of the carboxyl acrylic resin in the binder is 68.9 mgKOH / mg.

[0051] [Example 9] A boiling-resistant aluminum powder coating, which differs from [Example 7] in that the carboxyl-terminated polyester resin is a stearic acid-modified carboxyl-terminated polyester resin.

[0052] Specifically, the preparation of stearic acid modified carboxyl-terminated polyester comprises the following steps: The carboxyl-terminated polyester resin and stearic acid are mixed and dissolved with excess N,N-dimethylformamide, and then 0.5% p-toluenesulfonic acid is added, heated to 135°C for reaction for 3 hours, and then vacuumed to continue the reaction for 12 hours. After cooling to room temperature, the pH value is adjusted to 5.5 with a dilute sodium hydroxide solution, precipitated and filtered with anhydrous ethanol, and then the filter residue is vacuum dried and high-speed crushed to obtain a stearic acid-modified carboxyl-terminated polyester resin.

[0053] [Example 10] A water-boiling resistant aluminum powder coating, which differs from [Example 8] in that the type and amount of curing agent are different.

[0054] In this embodiment, the curing agent is replaced with β-hydroxyalkylamide, and the added amount is 6 kg.

[0055] [Example 11] A boiling-resistant aluminum powder coating, which differs from [Example 10] in that: the curing agent is replaced with a mixed curing agent of β-hydroxyalkylamide and dicyandiamide in equal amounts, and the mixing weight ratio of β-hydroxyalkylamide to dicyandiamide is 1:0.35.

[0056] In this embodiment, the added amount of β-hydroxyalkylamide is 4.44 kg, and the added amount of dicyandiamide is 1.56 kg.

[0057] Comparative Example [Comparative Example 1] A powder coating, which differs from [Example 1] in that: glycidyl methacrylate and carboxyl acrylic resin are not added, and glycidyl methacrylate and carboxyl acrylic resin are replaced by carboxyl-terminated polyester resin in equal amounts.

[0058] Specifically, in this comparative example, the binder includes 140 kg of carboxyl-terminated polyester resin.

[0059] [Comparative Example 2] A powder coating, which differs from [Example 1] in that no glycidyl methacrylate is added, and an equal amount of glycidyl methacrylate is replaced by a carboxyl-terminated polyester resin.

[0060] Specifically, in this comparative example, the binder includes 130 kg of carboxyl-terminated polyester resin and 10 kg of carboxyl acrylic resin.

[0061] [Comparative Example 3] A powder coating, which differs from [Example 1] in that no carboxyl acrylic resin is added, and an equal amount of the carboxyl acrylic resin is replaced by a carboxyl-terminated polyester resin.

[0062] Specifically, in this comparative example, the binder includes 110 kg of carboxyl-terminated polyester resin and 30 kg of glycidyl methacrylate.

[0063] Performance test data Preparation of samples to be tested: Under the same spraying pressure, the powder coatings prepared in the above Examples 1-11 and Comparative Examples 1-3 were sprayed on standard test plates preheated in an oven at 180°C by high-voltage electrostatic spraying, with a coating thickness of about 200 μm, a curing temperature of 200°C, and a curing time of 5 minutes to prepare the samples to be tested. Among them, the standard test plate used for the test was an aluminum plate, and was pretreated according to "GB / T 9271-2008 Standard Test Plate for Paints and Varnishes".

[0064] Aging treatment: The samples to be tested are subjected to automatic cycle exposure test according to the provisions of Table 3 Method A Cycle No. 1 in "GB / T 16422.2-2014 Plastic Laboratory Light Source Exposure Test Method", and the exposure time is 1000h.

[0065] 1. Boiling water resistance test: According to 6.14.1 of GB 5237.4-2004 Aluminum Alloy Building Profiles Part 4: Powder Spraying Profiles, the boiling water test was carried out, and the surface state of each embodiment and comparative example after boiling for 12 hours and the gloss loss rate of the coating were recorded respectively. Among them, the gloss loss rate was tested on the samples to be tested before and after boiling with reference to GB / T 9754 Determination of 20°, 60° and 85° specular gloss of paints and varnishes without metallic pigments, and the test geometric conditions were 60°±0.1° gloss loss rate =, the higher the gloss loss rate, the lower the gloss retention rate.

[0066] 2. Color difference value: Refer to "GB / T 11186.2 Measurement method of coating color Part 2 Color measurement" to test the samples before and after aging with a colorimeter, and refer to "GB / T 11186.3 Measurement method of coating color Part 3 Color difference calculation" to calculate the color difference value of the samples before and after aging. Among them, the larger the color difference value, the lower the color retention rate and the worse the weather resistance performance.

[0067] 3. Pencil hardness: Refer to "GB / T 6739-2006 Determination of paint film hardness by pencil method for paints and varnishes" for testing, and record the results in Table 1 below. The test object is the sample to be tested. Among them, the higher the hardness of the paint film, the better the wear resistance of the paint film.

[0068] Table 1 Performance test data Combining Example 1 and Comparative Examples 1-3 with the data in Table 1, it can be seen that mixing glycidyl methacrylate with the carboxyl-terminated polyester resin can effectively improve the water boiling resistance of the powder coating. After being immersed in boiling water for a long time, the coating surface still does not completely lose its gloss and has a certain gloss retention rate, but the weather resistance of the powder coating will be reduced. This may be because glycidyl methacrylate contains epoxy groups. When the carboxyl-terminated polyester resin is cured, the epoxy groups in the glycidyl methacrylate open the ring and cross-link with the carboxyl-terminated polyester resin, further improving the curing cross-linking density, so that the density of the formed coating is improved, which is beneficial to improving the water boiling resistance of the powder coating.

[0069] Adding a small amount of carboxyl acrylic resin can not only further improve the boiling resistance of the polyester resin, so that the coating can maintain a uniform color after long-term boiling, but also improve the weather resistance of the powder coating, making up for the reduced weather resistance due to the addition of glycidyl methacrylate. At the same time, it can also improve the surface strength of the coating, so that the powder coating can form a powder coating with higher mechanical strength.

[0070] Combining Example 1 and Example 4-6 with the data in Table 1, it can be seen that when the mixed weight ratio of the terminal carboxyl polyester resin, glycidyl methacrylate and carboxyl acrylic resin in the binder is within the range of 10:(3.5-3.7):(0.3-0.5), the powder coating has better comprehensive performance, not only has higher water boiling resistance and weather resistance, but also has higher surface hardness. This may be because when the amount of polyester resin added remains unchanged, as the amount of glycidyl methacrylate added increases and the amount of carboxyl acrylic resin added decreases, although the water boiling resistance of the powder coating is improved, the excessive amount of glycidyl methacrylate will also cause the weather resistance of the powder coating to decrease, and the color retention rate of the coating is low and the hardness decreases, which is not conducive to the long-term outdoor application of the powder coating.

[0071] In conjunction with Example 5 and Example 7-8 and the data in Table 1, it can be seen that as the acid value of the carboxylic acrylic resin increases, the coating formed by the powder coating has good weather resistance and surface hardness. This may be because as the acid value of the carboxylic acrylic resin is higher, the carboxylic acrylic resin provides more crosslinking reaction sites in the system, which can fully entangle and crosslink with the carboxyl-terminated polyester resin and glycidyl methacrylate, so that glycidyl methacrylate and the carboxylic acrylic resin can fully play their role and improve the various properties of the coating. However, when the acid value of the carboxylic acrylic resin exceeds a certain range, the boiling resistance of the coating obviously decreases, which may be because the carboxylic acrylic resin with an excessively high acid value may affect the reaction between the curing agent and the carboxyl-terminated polyester resin, and directly affect the degree of curing of the coating.

[0072] Combining Example 7 and Example 9 and considering the data in Table 1, it can be seen that by modifying the carboxyl-terminated polyester resin with stearic acid, the water-boiling resistance of the powder coating is further improved. This may be because there are still some hydroxyl groups in the carboxyl-terminated polyester resin. After modification with stearic acid, an esterification reaction occurs between stearic acid and the residual hydroxyl groups in the carboxyl-terminated polyester resin, which not only eliminates the residual hydroxyl groups in the carboxyl-terminated polyester resin, reduces the reaction sites available for water molecule adsorption, and decreases the water molecule penetration ability, but also introduces long-chain stearic acid groups into the carboxyl-terminated polyester resin, which is beneficial to reducing the melt viscosity of the coating and improving its leveling property during melting and curing, enabling the coating to maintain uniform flatness.

[0073] Combining Example 9 and Examples 10 - 11 and considering the data in Table 1, it can be seen that when the curing agent is β-hydroxyalkylamide, not only is the addition amount less than that when isocyanuric acid triglycidyl ester is used as the curing agent, but also β-hydroxyalkylamide does not contain epoxy groups, and the weather resistance of the powder coating can be improved to a certain extent. However, the water-boiling resistance of the powder coating is not as good as that when isocyanuric acid triglycidyl ester is used, and the gloss loss rate is relatively high. When the curing agent is a mixture of β-hydroxyalkylamide and dicyandiamide, the comprehensive performance of the powder coating is improved. It can not only make the water-boiling resistance of the powder coating close to that when isocyanuric acid triglycidyl ester is used alone for curing, but also has good weather resistance when β-hydroxyalkylamide is used alone for curing.

[0074] This specific implementation manner is only an interpretation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications without creative contributions to this specific implementation manner as needed, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A boiling-resistant aluminum powder coating, characterized in that: It includes the following raw materials in parts by weight: Binder: 135-160 parts; Curing agent: 5-16 parts; Benzoin: 0.3-0.6 parts; Leveling agent: 0.8-1.2 parts; Dispersant: 1.6-2.6 parts; Pigments and fillers: 50-80 parts; The binder comprises a carboxyl-terminated polyester resin, glycidyl methacrylate and a carboxyl acrylic resin, wherein the weight ratio of the carboxyl-terminated polyester resin, the glycidyl methacrylate and the carboxyl acrylic resin is 10:(2.5-4):(0.1-1), and the acid value of the carboxyl-terminated polyester resin is 40-60 mgKOH / g; The curing agent includes one of triglycidyl isocyanurate or β-hydroxyalkylamide.

2. The boiling-resistant aluminum powder coating according to claim 1, characterized in that: The mixing weight ratio of the carboxyl-terminated polyester resin, the glycidyl methacrylate and the carboxyl acrylic resin is 10: (3.5-3.7): (0.3-0.5).

3. The boiling-resistant aluminum powder coating according to claim 2, characterized in that: The acid value of the carboxyl acrylic resin is 50-53.5 mgKOH / g.

4. The boiling-resistant aluminum powder coating according to claim 1, characterized in that: The carboxyl-terminated polyester resin is a stearic acid-modified carboxyl-terminated polyester resin, and the modification step of the stearic acid-modified carboxyl-terminated resin comprises: The carboxyl-terminated polyester resin and stearic acid are mixed and dissolved by N,N-dimethylformamide, and then p-toluenesulfonic acid is added, and the mixture is heated to 125-135°C for reaction for 3-4 hours, and then vacuumed to continue the reaction for 12-18 hours. After cooling to room temperature, the pH value is adjusted to 4.5-7, and ethanol is used for precipitation and filtration. The filter residue is vacuum dried and then high-speed crushed to obtain a stearic acid-modified carboxyl-terminated polyester resin.

5. The boiling-resistant aluminum powder coating according to claim 1, characterized in that: The curing agent includes β-hydroxyalkylamide.

6. The boiling-resistant aluminum powder coating according to claim 5, characterized in that: The curing agent also includes dicyandiamide, and the mixing weight ratio of the beta-hydroxyalkylamide to the dicyandiamide is 1:(0.08-0.12).

7. The boiling-resistant aluminum powder coating according to claim 1, characterized in that: The dispersant is a mixture of silane coupling agent KH550 and silane coupling agent KH570, and the mixing weight ratio of the silane coupling agent KH550 to the silane coupling agent KH570 is (0.22-0.3):

1.

8. The boiling-resistant aluminum powder coating according to claim 1, characterized in that: The pigment filler includes bentonite, barium sulfate, rutile titanium dioxide and organic pigments, and the mixing weight ratio of the bentonite, the barium sulfate, the rutile titanium dioxide and the inorganic pigment is 1: (22.5-35): (1.5-3.5): (0.5-0.8).

9. The boiling-resistant aluminum powder coating according to claim 1, characterized in that: The leveling agent is a polyether-modified organic silicon compound.

10. A method for preparing a boiling-resistant aluminum powder coating, characterized in that: The method for preparing a boiling-resistant aluminum powder coating according to any one of claims 1 to 9 comprises the following steps: S1, stirring and mixing the carboxyl-terminated polyester resin and the glycidyl methacrylate in proportion at 130-150° C., after the mixture is uniformly mixed, after the temperature is raised to the range of 160-175° C., adding the carboxyl acrylic resin, and continuing to stir and mix at the same temperature, after the mixture is uniformly mixed, extruding and granulating to obtain a binder; S2. After uniformly mixing the binder, curing agent, benzoin, leveling agent, dispersant, pigment and filler, etc., the mixture is melt-extruded, tableted, crushed, and sieved to obtain a powder coating.

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