Preparation method and application of powder coating for super weather-resistant and highly flexible coiled materials

Abstract

The invention discloses a preparation method and application of a powder coating for super weather-resistant and highly flexible coiled materials, and relates to the technical field of powder coatings. The invention discloses a preparation method of a powder coating for super weather-resistant and highly flexible coiled materials, comprising the following steps: according to the weight percentage of the raw materials, a filler-modified polyester resin, a curing agent, a defoamer, a leveling agent, an adhesion promoter, and polytetrafluoro wax are mixed to obtain a powder coating; the filler-modified polyester resin of the present application is obtained by reacting amino-terminated hydroxyl polyester, phosphorous acid, and epoxy-modified graphene oxide, and then carboxylating with succinic anhydride; the filler-modified polyester resin prepared in the present application is added to the coating as a base material of the powder coating, giving the coating the characteristics of high weather resistance and high flexibility.

Description

Technical Field

[0001] The invention relates to the technical field of powder coatings, and in particular to a preparation method and application of a powder coating for super-weather-resistant and highly flexible coiled materials. Background Art

[0002] Color-coated sheet products are mainly used in the construction, home appliance and other industries, in addition to the transportation (automobile) industry, and are developing in the direction of thin specifications (less than 0.5mm), high strength (greater than 500MPa), corrosion resistance, and excellent processing and forming properties. The color-coated sheet industry is still dominated by solvent-based coatings. However, the coating thickness of solvent-based coatings is generally around 20um. In order to achieve the decorative and protective properties of the coating, solvent-based coatings often require multiple coatings, such as three layers of bottom, middle and top coatings. After each coating, heating and curing are required, which not only consumes a lot of energy, but also the volatilization of solvents into the atmosphere during drying can easily cause serious environmental pollution. At present, powder coatings are gradually replacing liquid oil-based coatings with their advantages of environmental protection, economy, high efficiency and excellent performance.

[0003] Powder coating is a new material based on petrochemicals. It is composed of low molecular weight resin, supplemented by additives, pigments and fillers, etc. It has a certain appearance, gloss and color after curing under certain conditions. When the powder coating coated board is placed in the outdoor natural environment, its coating film is invaded by various factors, such as sunlight, acid rain erosion, etc. The aging phenomenon of the coating film is mainly caused by photo-oxidation degradation caused by sunlight and air (oxygen), especially the 295-350nm ultraviolet radiation in sunlight has the greatest damage to the degradation of the coating film polymer. When the coating film contains benzene rings, carbonyl groups, ketones, unsaturated bonds, tertiary carbons and other groups that are very easy to absorb ultraviolet rays, the damage to the coating is even greater, and the presence of oxygen further accelerates the process of photo-oxidation degradation. In addition to sunlight, rain and acidic gases in the atmosphere (nitrogen dioxide, sulfur dioxide, etc.) are also important aging factors. Polyester resins contain ester bonds and are easily hydrolyzed. Acidic gases dissolved in water will catalyze the hydrolysis and breakage of the ester bonds in the resin more quickly. In addition, the pigments and fillers commonly used in carboxyl-terminated polyester powder coatings react chemically with the coating film, accelerating the vibration of molecules in the polyester structure, causing it to break and undergo thermal degradation. In the presence of oxygen, the damage is even more serious. The coating film shows a loss of gloss, darkening of color, the appearance of rust spots or cracks, and the beginning of slight powdering. Moreover, color-coated panels almost always involve post-molding processes. Outdoor application scenarios must ensure that the coating has excellent weather resistance and excellent flexibility. Traditional weather-resistant products cannot have both due to the influence of the resin synthetic structure. Summary of the invention

[0004] The purpose of the present invention is to provide a preparation method and application of a powder coating for super weather-resistant and highly flexible coiled materials, and to solve the following technical problems:

[0005] The existing weather-resistant products are affected by the resin synthesis structure, so the coating cannot have both excellent weather resistance and excellent flexibility.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for preparing a powder coating for a super-weather-resistant and highly flexible coiled material comprises the following steps:

[0008] The filler-modified polyester resin, the curing agent, the defoaming agent, the leveling agent, the adhesion promoter, and the polytetrafluoroethylene wax are mixed according to the weight percentage of the raw materials to obtain a powder coating;

[0009] The preparation method of filler-modified polyester resin comprises the following steps:

[0010] S1: Add amino-terminated hydroxyl polyester, phosphorous acid, epoxy-modified graphene oxide, and N,N-dimethylformamide into a reaction kettle and disperse them evenly, control the temperature to 80-90°C, keep the temperature for reaction for 1-3h, cool to room temperature, filter, wash, and dry to obtain component 1;

[0011] S2: Add component 1, succinic anhydride and N,N-dimethylformamide into a reaction kettle and disperse them evenly. Control the temperature to 80-90°C and keep the reaction warm for 1-3 hours. Add ether to terminate the reaction. Filter with suction, wash with ethanol and dry to obtain filler-modified polyester resin.

[0012] As a further solution of the present invention: the addition ratio of the amino-terminated hydroxyl polyester, phosphorous acid, epoxy-modified graphene oxide, and N,N-dimethylformamide in S1 is 10 g: 1-1.5 g: 1-4 g: 100-200 mL.

[0013] As a further solution of the present invention: the addition ratio of component 1, succinic anhydride and N,N-dimethylformamide in S2 is 10g:10-12g:500-1000mL.

[0014] As a further embodiment of the present invention: the preparation method of the amino-terminated hydroxyl polyester comprises the following steps:

[0015] A1: neopentyl glycol, trimethylolpropane, terephthalic acid, isophthalic acid, adipic acid, Fmoc-aspartic acid and a catalyst are introduced with nitrogen, heated to 170-180°C, and then further heated to 230-240°C, and kept for reaction for 9-12 hours. After vacuum pressure treatment, the pressure is released to obtain a hydroxyl-terminated polyester;

[0016] A2: Add terminal hydroxyl polyester, potassium carbonate and anhydrous ethanol into a reaction kettle and disperse them evenly, stir at room temperature for 3-6 hours, filter with suction, take the filtrate and blend it with hydrochloric acid ethanol solution, wash, separate, take the lower layer liquid and dry it to obtain amino terminal hydroxyl polyester.

[0017] As a further embodiment of the present invention: the terminal hydroxyl polyester comprises the following raw materials in parts by weight: 20-23 parts by weight of neopentyl glycol, 1-3 parts by weight of trimethylolpropane, 28-36 parts by weight of terephthalic acid, 6-11.5 parts by weight of isophthalic acid, 0.5-1.5 parts by weight of adipic acid, 5-15 parts by weight of Fmoc-aspartic acid, and 0.05-0.08 parts by weight of a catalyst.

[0018] As a further embodiment of the present invention, the addition ratio of the hydroxyl-terminated polyester, potassium carbonate and anhydrous ethanol is 10 g: 0.5-1 g: 100-200 mL.

[0019] As a further solution of the present invention: the specific steps of the vacuuming and pressure-maintaining treatment are: vacuuming to 0.05-0.09 MPa and maintaining the pressure for 0.5-1 h.

[0020] As a further embodiment of the present invention: the catalyst is any one of monobutyltin oxide and stannous oxalate.

[0021] As a further scheme of the present invention: the preparation method of Fmoc-aspartic acid comprises the following steps: adding L-aspartic acid and dioxane to a reactor and dispersing them uniformly, controlling the temperature at 0-5°C, adding concentrated sulfuric acid, introducing isobutylene, reacting for a period of time, adding 20wt% sodium hydroxide aqueous solution to adjust the pH to 7, and then adding sodium carbonate buffer to adjust the pH to 9-10, blending Fmoc-Osu and dioxane solution and adding them to the reactor, reacting at room temperature for 3-6h, filtering, washing the filtrate with ether, adjusting the pH of the inorganic phase to 5.5 with hydrochloric acid aqueous solution, adding ethyl acetate for extraction, taking the organic phase, concentrating, and recrystallizing to obtain Fmoc-aspartic acid.

[0022] As a further embodiment of the present invention: the preparation method of epoxy-modified graphene oxide comprises the following steps:

[0023] Graphene oxide and N,N-dimethylformamide were added to a reaction bottle and dispersed evenly, γ-(2,3-epoxypropoxy)propyltrimethoxysilane was added, the temperature was controlled at 70-80°C, the reaction was kept warm for 0.5-1h, and the epoxy-modified graphene oxide was obtained by suction filtration, washing and drying.

[0024] As a further solution of the present invention: the addition ratio of graphene oxide (purchased from Inner Mongolia Ruisheng New Material Technology Co., Ltd.), N,N-dimethylformamide, and γ-(2,3-epoxypropoxy)propyltrimethoxysilane is 10g:100-500mL:0.1-0.5g.

[0025] As a further embodiment of the present invention, the filler-modified polyester resin accounts for 87-92% of the total weight of the powder coating.

[0026] As a further solution of the present invention: the curing agent is triglycidyl isocyanurate, and the curing agent accounts for 4-6% of the total mass of the powder coating.

[0027] As a further solution of the present invention: the polytetrafluoro wax accounts for 0.5-1% of the total mass of the powder coating.

[0028] As a further solution of the present invention: the defoamer is at least one of an amide wax defoamer, a polypropylene / polyethylene wax defoamer, and a polyoxyethylene defoamer; the defoamer accounts for 1-2% of the total mass of the powder coating.

[0029] As a further solution of the present invention: the leveling agent is at least one of acrylate homopolymer, silicone-modified acrylate polymer, polysiloxane, hydrogenated castor oil, and polyvinyl butyral; the leveling agent accounts for 0.8-1.2% of the total mass of the powder coating.

[0030] As a further solution of the present invention: the adhesion promoter is at least one of a resin adhesion promoter, a silane coupling agent adhesion promoter, and an organic metal adhesion promoter; the adhesion promoter accounts for 1-3% of the total mass of the powder coating.

[0031] The ultra-weather-resistant and highly flexible powder coating for coiled materials prepared by any of the above preparation methods is applied in the field of color-coated plates.

[0032] Beneficial effects of the present invention:

[0033] (1) The present application firstly uses Fmoc-Osu (fluorenylmethoxycarbonyl succinimide) to protect the amino group of aspartic acid to obtain Fmoc-aspartic acid; the present application uses neopentyl glycol, trimethylolpropane, terephthalic acid, isophthalic acid, and adipic acid as raw materials to prepare the raw materials of terminal hydroxyl polyester through high-temperature melt dehydration condensation polymerization, and additionally adds Fmoc-aspartic acid to be grafted on the main chain of the terminal hydroxyl polyester to obtain the terminal hydroxyl polyester; finally, potassium carbonate is used to deprotect the amino group grafted on the side chain of the terminal hydroxyl polyester to obtain the amino-terminated hydroxyl polyester. The present application firstly uses an epoxy silane coupling agent to carry out epoxidation modification on graphene oxide by a one-step hydrothermal method to obtain graphene oxide with epoxy groups grafted on the surface, i.e., epoxy-modified graphene oxide; the present application then uses the epoxy groups on the surface of the epoxy-modified graphene oxide, the amino groups of the amino-terminated hydroxyl polyester and phosphorous acid to carry out a ring-opening reaction to obtain component one; component one prepared in the present application is a hydroxyl-terminated polyester resin with phosphite groups, silicone molecular chains and graphene oxide grafted on the hydroxyl-terminated polyester molecular chain; the present application finally uses succinic anhydride to terminally carboxylate the hydroxyl-terminated polyester resin to obtain a filler-modified polyester resin.

[0034] The filler-modified polyester resin prepared in the present application has the characteristics of hyperbranching, and the surface of the filler-modified polyester resin contains a large number of functional groups, which affect the crystallization of scale-forming substances through lattice distortion, so that the material has good scale inhibition ability. The present application prepares the filler-modified polyester resin side chain grafted with longer silicon-containing molecular chains and graphene oxide, which increases the hydrophobicity of the resin, thereby improving the hydrolysis stability of the powder coating. Moreover, the addition of epoxy-modified graphene oxide can improve the ultraviolet light resistance of the powder coating by utilizing the π-π conjugated structure and free radical quenching characteristics of graphene oxide, and effectively blocks the aging and degradation of the coating by utilizing the free radical capture effect of graphene oxide and the barrier effect of the lamellar structure; and the present application introduces Si-O bonds with higher bond energy on the surface of graphene oxide, which ensures that the synthesized polyester resin has good ultraviolet resistance and further improves the weather resistance of the powder coating. The coating obtained by the present invention has excellent weather resistance and flexibility, and has a wide range of application prospects.

[0035] (2) This application uses a silane coupling agent to organically modify graphene oxide to obtain epoxy-modified graphene oxide; epoxy-modified graphene oxide and polyester resin are molecularly linked and grafted to obtain a network structure with graphene oxide as a crosslinking point. Under stress, the interface between graphene oxide and polyester resin debonds, and the holes generated by debonding change the stress state of the substrate, causing the coating to yield and absorb energy, showing excellent toughness. In addition, organic silicon is enriched on the surface of graphene oxide, which greatly reduces the surface tension of polyester and improves the weather resistance of the powder coating.

[0036] (3) The raw materials for preparing the powder coating of the present application include filler-modified polyester resin, triglycidyl isocyanurate, defoamer, leveling agent, adhesion promoter, and polytetrafluoro wax additive; wherein, phosphite is introduced into the filler-modified polyester resin during the preparation process to have an antioxidant effect; and the present application uses triglycidyl isocyanurate as a curing agent in combination with the filler-modified polyester resin prepared in the present application, and the glycidyl group of triglycidyl isocyanurate undergoes a ring-opening addition reaction with the carboxyl group in the filler-modified polyester resin to achieve cross-linking and curing to form a thick film coating without pores; the trifunctional group of triglycidyl isocyanurate provides sufficient activity, and the stable triazine ring ensures good heat resistance and weathering stability. DETAILED DESCRIPTION

[0037] The following will be described clearly and completely in conjunction with the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Example 1 The preparation method of the amino-terminated hydroxyl polyester comprises the following steps:

[0039] A1: 130 g L-aspartic acid and 1000 mL dioxane were added to a reactor and dispersed evenly. The temperature was controlled at 0-5°C. 80 mL 98 wt% concentrated sulfuric acid was added. Isobutylene was introduced and reacted for 72 h. A 20 wt% sodium hydroxide aqueous solution was added to adjust the pH to 7. Then, a sodium carbonate buffer solution was added to adjust the pH to 9. 320 g Fmoc-Osu and 500 mL dioxane solution were mixed and added to the reactor. The mixture was reacted at room temperature for 3 h. The mixture was filtered, the filtrate was washed with ether, the inorganic phase was adjusted to pH 5.5 with a 2 mol / L hydrochloric acid aqueous solution, ethyl acetate was added for extraction, the organic phase was concentrated, and recrystallized to obtain Fmoc-aspartic acid.

[0040] A2: 200 g of neopentyl glycol, 30 g of trimethylolpropane, 320 g of terephthalic acid, 76 g of isophthalic acid, 8 g of adipic acid, 100 g of Fmoc-aspartic acid, and 0.8 g of monobutyltin oxide were purged with nitrogen, heated to 180°C, and then continued to heat to 240°C, and kept reacting for 12 h. The mixture was evacuated to 0.09 MPa, maintained under pressure for 1 h, and then released to obtain a hydroxyl-terminated polyester.

[0041] A3: 100g of hydroxyl-terminated polyester, 10g of potassium carbonate and 2000mL of anhydrous ethanol were added into a reaction kettle and dispersed evenly. The mixture was stirred at room temperature for 6h and filtered. The filtrate was mixed with 2mol / L hydrochloric acid ethanol solution, washed, separated and the lower layer was dried to obtain amino-terminated hydroxyl-terminated polyester.

[0042] Embodiment 2 The preparation method of filler-modified polyester resin comprises the following steps:

[0043] S1: 50 g of graphene oxide (purchased from Inner Mongolia Ruisheng New Material Technology Co., Ltd.) and 500 mL of N,N-dimethylformamide were added to a reaction bottle and dispersed evenly, 0.5 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane was added, the temperature was controlled at 70 ° C, the reaction was kept warm for 0.5 h, and then filtered, washed, and dried to obtain epoxy-modified graphene oxide;

[0044] S2: 100 g of the amino-terminated hydroxyl polyester prepared in Example 1, 10 g of phosphorous acid, 20 g of epoxy-modified graphene oxide, and 1000 mL of N,N-dimethylformamide were added to a reaction kettle and dispersed evenly. The temperature was controlled at 80° C. and the reaction was kept warm for 1 h. The mixture was cooled to room temperature, filtered, washed, and dried to obtain component 1.

[0045] S3: Add 100g of component 1, 100g of succinic anhydride and 5000mL of N,N-dimethylformamide into a reaction kettle and disperse them evenly. Control the temperature to 80°C and keep the reaction for 1h. Add ether to terminate the reaction. Filter by suction, wash with ethanol and dry to obtain a filler-modified polyester resin.

[0046] Example 3 The preparation method of filler-modified polyester resin comprises the following steps:

[0047] S1: 50 g of graphene oxide (purchased from Inner Mongolia Ruisheng New Material Technology Co., Ltd.) and 500 mL of N,N-dimethylformamide were added to a reaction bottle and dispersed evenly, 1.5 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane was added, the temperature was controlled at 75 ° C, the reaction was kept warm for 0.5 h, and then filtered, washed, and dried to obtain epoxy-modified graphene oxide;

[0048] S2: 100 g of the amino-terminated hydroxyl polyester prepared in Example 1, 12 g of phosphorous acid, 20 g of epoxy-modified graphene oxide, and 2000 mL of N,N-dimethylformamide were added to a reaction kettle and dispersed evenly. The temperature was controlled at 85° C. and the reaction was kept warm for 2 h. The mixture was cooled to room temperature, filtered, washed, and dried to obtain component 1.

[0049] S3: Add 100g of component 1, 110g of succinic anhydride and 5000mL of N,N-dimethylformamide into a reaction kettle and disperse them evenly. Control the temperature to 85°C and keep the reaction for 2h. Add ether to terminate the reaction. Filter, wash with ethanol and dry to obtain a filler-modified polyester resin.

[0050] Example 4 The preparation method of filler-modified polyester resin comprises the following steps:

[0051] S1: 50 g of graphene oxide (purchased from Inner Mongolia Ruisheng New Material Technology Co., Ltd.) and 500 mL of N,N-dimethylformamide were added to a reaction bottle and dispersed evenly, 2.5 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane was added, the temperature was controlled at 80 ° C, the reaction was kept warm for 1 h, and then filtered, washed, and dried to obtain epoxy-modified graphene oxide;

[0052] S2: 100 g of the amino-terminated hydroxyl polyester prepared in Example 1, 15 g of phosphorous acid, 20 g of epoxy-modified graphene oxide, and 2000 mL of N,N-dimethylformamide were added to a reaction kettle and dispersed evenly. The temperature was controlled at 90° C. and the reaction was kept warm for 3 h. The mixture was cooled to room temperature, filtered, washed, and dried to obtain component 1.

[0053] S3: Add 100g of component 1, 120g of succinic anhydride and 5000mL of N,N-dimethylformamide into a reaction kettle and disperse them evenly. Control the temperature at 90°C and keep the reaction for 3h. Add ether to terminate the reaction. Filter, wash with ethanol and dry to obtain a filler-modified polyester resin.

[0054] Embodiment 5 A method for preparing a powder coating for ultra-weather-resistant and highly flexible coiled material comprises the following steps:

[0055] 89 g of the filler-modified polyester resin prepared in Example 2, 5% of the curing agent triglycidyl isocyanurate, 1.5 g of the polyoxyethylene defoamer 961A, 1 g of the leveling agent GLP588 (purchased from Ningbo Nanhai Chemical Co., Ltd.), 2.5 g of the adhesion promoter 306 (purchased from Hubei Laisi Chemical New Materials Co., Ltd.), and 1 g of polytetrafluoroethylene wax (purchased from Micro Powders, with a particle size of 10-15 μm) were mixed to obtain a powder coating.

[0056] Embodiment 6 A method for preparing a powder coating for a super-weather-resistant and highly flexible coil material comprises the following steps:

[0057] 89 g of the filler-modified polyester resin prepared in Example 3, 5% of the curing agent triglycidyl isocyanurate, 1.5 g of the polyoxyethylene defoamer 961A, 1 g of the leveling agent GLP588 (purchased from Ningbo Nanhai Chemical Co., Ltd.), 2.5 g of the adhesion promoter 306 (purchased from Hubei Laisi Chemical New Materials Co., Ltd.), and 1 g of polytetrafluoroethylene wax (purchased from Micro Powders, with a particle size of 10-15 μm) were mixed to obtain a powder coating.

[0058] Embodiment 7 A method for preparing a powder coating for ultra-weather-resistant and highly flexible coiled material comprises the following steps:

[0059] 89 g of the filler-modified polyester resin prepared in Example 4, 5% of the curing agent triglycidyl isocyanurate, 1.5 g of the polyoxyethylene defoamer 961A, 1 g of the leveling agent GLP588 (purchased from Ningbo Nanhai Chemical Co., Ltd.), 2.5 g of the adhesion promoter 306 (purchased from Hubei Laisi Chemical New Materials Co., Ltd.), and 1 g of polytetrafluoroethylene wax (purchased from Micro Powders, with a particle size of 10-15 μm) were mixed to obtain a powder coating.

[0060] Comparative Example 1 The preparation method of the modified polyester resin comprises the following steps:

[0061] S1: 100 g of the amino-terminated hydroxyl polyester prepared in Example 1, 10 g of phosphorous acid, 20 g of epichlorohydrin, and 1000 mL of N,N-dimethylformamide were added to a reaction kettle and dispersed evenly. The temperature was controlled at 80° C. and the reaction was kept warm for 1 h. The mixture was cooled to room temperature, filtered, washed, and dried to obtain component 1.

[0062] S2: Add 100g of component 1, 100g of succinic anhydride and 5000mL of N,N-dimethylformamide into a reaction kettle and disperse them evenly. Control the temperature to 80°C and keep the reaction for 1h. Add ether to terminate the reaction. Filter with suction, wash with ethanol and dry to obtain a modified polyester resin.

[0063] Comparative Example 2 The preparation method of filler-modified polyester resin comprises the following steps:

[0064] S1: 50 g of graphene oxide (purchased from Inner Mongolia Ruisheng New Material Technology Co., Ltd.) and 500 mL of N,N-dimethylformamide were added to a reaction bottle and dispersed evenly, 1.5 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane was added, the temperature was controlled at 75 ° C, the reaction was kept warm for 0.5 h, and then filtered, washed, and dried to obtain epoxy-modified graphene oxide;

[0065] S2: 100 g of the amino-terminated hydroxyl polyester prepared in Example 1, 20 g of epoxy-modified graphene oxide, and 2000 mL of N,N-dimethylformamide were added to a reaction kettle and dispersed evenly. The temperature was controlled at 85° C. and the reaction was kept warm for 2 h. The mixture was cooled to room temperature, filtered, washed, and dried to obtain component 1.

[0066] S3: Add 100g of component 1, 110g of succinic anhydride and 5000mL of N,N-dimethylformamide into a reaction kettle and disperse them evenly. Control the temperature to 85°C and keep the reaction for 2h. Add ether to terminate the reaction. Filter, wash with ethanol and dry to obtain a filler-modified polyester resin.

[0067] Comparative Example 3 The preparation method of filler-modified polyester resin comprises the following steps:

[0068] S1: 50 g of graphene oxide (purchased from Inner Mongolia Ruisheng New Material Technology Co., Ltd.) and 500 mL of N,N-dimethylformamide were added to a reaction bottle and dispersed evenly, 0.5 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane was added, the temperature was controlled at 70 ° C, the reaction was kept warm for 0.5 h, and then filtered, washed, and dried to obtain epoxy-modified graphene oxide;

[0069] S2: 200g of neopentyl glycol, 30g of trimethylolpropane, 310g of terephthalic acid, 76g of isophthalic acid, 8g of adipic acid, and 0.8g of monobutyltin oxide were purged with nitrogen, heated to 180°C, and then continued to heat to 240°C, and kept warm for 9h, 10g of terephthalic acid was added and reacted for 3h, and then vacuumed to 0.09MPa, maintained for 1h, and then released to obtain a carboxyl-terminated polyester;

[0070] S3: 100 g of carboxyl-terminated polyester, 10 g of phosphorous acid, and 20 g of epoxy-modified graphene oxide are blended to obtain a filler-modified polyester resin.

[0071] Comparative Example 4 The preparation method of filler-modified polyester resin comprises the following steps:

[0072] S1: Add 50g of nano-silica and 500mL of N,N-dimethylformamide into a reaction bottle and disperse them evenly, add 1.5g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, control the temperature to 75°C, keep the reaction for 0.5h, filter, wash and dry to obtain epoxy-modified silica;

[0073] S2: 100 g of the amino-terminated hydroxyl polyester prepared in Example 1, 12 g of phosphorous acid, 20 g of epoxy-modified silica, and 2000 mL of N,N-dimethylformamide were added to a reaction kettle and dispersed evenly. The temperature was controlled at 85° C. and the reaction was kept warm for 2 h. The mixture was cooled to room temperature, filtered, washed, and dried to obtain component 1.

[0074] S3: Add 100g of component 1, 110g of succinic anhydride and 5000mL of N,N-dimethylformamide into a reaction kettle and disperse them evenly. Control the temperature to 85°C and keep the reaction for 2h. Add ether to terminate the reaction. Filter, wash with ethanol and dry to obtain a filler-modified polyester resin.

[0075] Compared with Example 5, Comparative Example 5 is that only the filler-modified polyester resin prepared in Example 2 added in Example 5 is replaced by an equal amount of the modified polyester resin prepared in Comparative Example 1. The other components and preparation method of Comparative Example 5 are completely consistent with those of Example 5.

[0076] Compared with Example 5, Comparative Example 6 is the case in which only the filler-modified polyester resin prepared in Example 2 added in Example 5 is replaced by an equal amount of the filler-modified polyester resin prepared in Comparative Example 2. The other components and preparation method of Comparative Example 6 are completely consistent with those of Example 5.

[0077] Compared with Example 5, Comparative Example 7 is that only the filler-modified polyester resin prepared in Example 2 added in Example 5 is replaced by an equal amount of the filler-modified polyester resin prepared in Comparative Example 3. The other components and preparation method of Comparative Example 7 are completely consistent with those of Example 5.

[0078] Compared with Example 5, Comparative Example 8 is that only the filler-modified polyester resin prepared in Example 2 added in Example 5 is replaced by an equal amount of the filler-modified polyester resin prepared in Comparative Example 4. The other components and preparation method of Comparative Example 8 are completely consistent with those of Example 5.

[0079] Performance Testing

[0080] (1) T-bend test: According to Section 7.5.1 of GB / T 13448-2019 Test Methods for Color Coated Steel Sheets and Strips, the plates sprayed with the powder coatings prepared in Examples 5-7 and Comparative Examples 5-8 were placed in two test environments for testing: ① placed in an environment with a temperature of (23±2)°C and a humidity of (50±5)%RH for 24 hours; ② placed in an environment with a temperature of -30°C for 42 days. The test results are shown in Table 3.

[0081] (2) Organic solvent resistance test: According to Section 10.5 of GB / T 13448-2019 Test methods for color coated steel sheets and strips, cotton cloth was dipped in methyl ethyl ketone and rubbed 100 times at a pressure of (0.1±0.02) MPa and a test speed of 60 cpm; the test environment: temperature (23±2) °C, ambient humidity (50±5)% RH; the test results are shown in Table 3;

[0082] (3) Neutral salt spray resistance test: The test was conducted in accordance with Section 21 of GB / T 13448-2019 Test methods for color coated steel sheets and strips, using pH 6.5-7.2, (50±5) g / L NaCl as the precipitation salt solution, test environment: temperature (35±2)°C, salt spray precipitation rate 1.5 mL / (80 cm 2 h), exposure for 1000 h; determine the blister density and blister size based on the data in Table 1-2; the test results are shown in Table 3;

[0083] Table 1: Foam density grades

[0084]

[0085] Table 2: Blister size ratings

[0086]

[0087] Table 3: Statistical table of performance test data of Examples 5-7 and Comparative Examples 5-8

[0088]

[0089] As shown in Table 3, the powder coating prepared in the present application has excellent toughness, and the paint surface remains intact after bending. In addition, the paint surface prepared by the powder coating in the present application has the characteristics of resistance to organic solvents and salt spray, and has long-lasting effect in actual use.

[0090] (4) Light aging test: Test according to cycle A of GB / T 1865-2009 "Artificial weathering and artificial radiation exposure of paints and varnishes to filtered xenon arc radiation", test environment: irradiance 0.51W (m 2 ˙nm) @340nm, illumination: 102min, black mark temperature (65±2)℃, ambient humidity (50±10)%RH; illumination and spraying: 18min; xenon lamp radiation exposure for 1500h, powdering grade determined according to Section 4.3.2 of GB / T 1766-2008 and various grades determined according to the data in Table 1-2 and Table 4-9; the test results are shown in Table 10;

[0091] Table 4: Gloss loss levels

[0092]

[0093] Table 5: Discoloration Grades

[0094]

[0095] Table 6: Crack size grades

[0096]

[0097] Table 7: Crack quantity level

[0098]

[0099] Table 8: Rust quantity level

[0100]

[0101] Table 9: Rust spot size grades

[0102]

[0103] Table 10: Statistical table of performance test data of Examples 5-7 and Comparative Examples 5-8

[0104]

[0105] It can be seen from Table 10 that the powder coating prepared in this application has excellent weather resistance.

[0106] The above is a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A method for preparing a powder coating for super weather-resistant and highly flexible coiled materials, characterized in that: The steps include: The filler-modified polyester resin, the curing agent, the defoaming agent, the leveling agent, the adhesion promoter, and the polytetrafluoroethylene wax are mixed according to the weight percentage of the raw materials to obtain a powder coating; The filler-modified polyester resin accounts for 87-92% of the total mass of the powder coating; the curing agent accounts for 4-6% of the total mass of the powder coating; the polytetrafluoro wax accounts for 0.5-1% of the total mass of the powder coating; the defoamer accounts for 1-2% of the total mass of the powder coating; the leveling agent accounts for 0.8-1.2% of the total mass of the powder coating; the adhesion promoter accounts for 1-3% of the total mass of the powder coating; The preparation method of filler-modified polyester resin comprises the following steps: S1: Add amino-terminated hydroxyl polyester, phosphorous acid, epoxy-modified graphene oxide, and N,N-dimethylformamide into a reaction kettle and disperse them evenly, control the temperature to 80-90°C, keep the temperature for reaction for 1-3h, cool to room temperature, filter, wash, and dry to obtain component 1; S2: Add component 1, succinic anhydride and N,N-dimethylformamide into a reaction kettle and disperse them evenly. Control the temperature to 80-90°C, keep the temperature to react for 1-3 hours, add ether to terminate the reaction, filter, wash with ethanol, and dry to obtain a filler-modified polyester resin. The addition ratio of amino-terminated hydroxyl polyester, phosphorous acid, epoxy-modified graphene oxide, and N,N-dimethylformamide in S1 is 10 g: 1-1.5 g: 1-4 g: 100-200 mL; The addition ratio of component 1, succinic anhydride, and N,N-dimethylformamide in S2 is 10 g: 10-12 g: 500-1000 mL; The preparation method of the amino-terminated hydroxyl polyester comprises the following steps: A1: neopentyl glycol, trimethylolpropane, terephthalic acid, isophthalic acid, adipic acid, Fmoc-aspartic acid and a catalyst are introduced with nitrogen, heated to 170-180°C, and then further heated to 230-240°C, and kept for reaction for 9-12 hours. After vacuum pressure treatment, the pressure is released to obtain a hydroxyl-terminated polyester; A2: Add hydroxyl-terminated polyester, potassium carbonate and anhydrous ethanol into a reaction kettle and disperse them evenly, stir at room temperature for 3-6 hours, filter with suction, take the filtrate and blend it with hydrochloric acid ethanol solution, wash, separate, take the lower layer and dry it to obtain amino-terminated hydroxyl-terminated polyester; The terminal hydroxyl polyester A1 comprises the following raw materials in parts by weight: 20-23 parts by weight of neopentyl glycol, 1-3 parts by weight of trimethylolpropane, 28-36 parts by weight of terephthalic acid, 6-11.5 parts by weight of isophthalic acid, 0.5-1.5 parts by weight of adipic acid, 5-15 parts by weight of Fmoc-aspartic acid, and 0.05-0.08 parts by weight of a catalyst; The addition ratio of terminal hydroxyl polyester, potassium carbonate and anhydrous ethanol in A2 is 10g: 0.5-1g: 100-200mL.

2. The method for preparing a powder coating for super weather-resistant and highly flexible coiled material according to claim 1, characterized in that: The preparation method of epoxy-modified graphene oxide comprises the following steps: Graphene oxide and N,N-dimethylformamide were added to a reaction bottle and dispersed evenly, γ-(2,3-epoxypropoxy)propyltrimethoxysilane was added, the temperature was controlled at 70-80°C, the reaction was kept warm for 0.5-1h, and the epoxy-modified graphene oxide was obtained by suction filtration, washing and drying.

3. The method for preparing a powder coating for super weather-resistant and highly flexible coiled material according to claim 1, characterized in that: The curing agent is triglycidyl isocyanurate, and the curing agent accounts for 4-6% of the total mass of the powder coating.

4. The method for preparing a powder coating for super weather-resistant and highly flexible coiled material according to claim 1, characterized in that: The defoamer is at least one of an amide wax defoamer, a polypropylene / polyethylene wax defoamer, and a polyoxyethylene defoamer; the defoamer accounts for 1-2% of the total mass of the powder coating.

5. The method for preparing a powder coating for super weather-resistant and highly flexible coiled material according to claim 1, characterized in that: The leveling agent is at least one of acrylate homopolymer, silicone-modified acrylate polymer, polysiloxane, hydrogenated castor oil, and polyvinyl butyral; the leveling agent accounts for 0.8-1.2% of the total mass of the powder coating.

6. The method for preparing a powder coating for super weather-resistant and highly flexible coiled material according to claim 1, characterized in that: The adhesion promoter is at least one of a resin adhesion promoter, a silane coupling agent adhesion promoter, and an organic metal adhesion promoter; the adhesion promoter accounts for 1-3% of the total mass of the powder coating.

7. Application of the powder coating for super weather-resistant and highly flexible coiled materials prepared by the preparation method according to any one of claims 1 to 6 in the field of color-coated plates.

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