A high-toughness hybrid powder coating and a method for preparing the same

Abstract

The application discloses a kind of high toughness mixed type powder coating and preparation method thereof, belong to powder coating production technical field, first, high toughness mixed type powder coating includes the following mass parts raw materials: epoxy resin 55 parts, hydroxyl polyester resin 42~45 parts, core-shell acrylic copolymer 22~30 parts, nano silicon dioxide 5 parts, titanium white 20 parts, leveling agent 1.0~1.2 parts, melamine crosslinking agent 1.4~1.5 parts.The application is toughened by core-shell acrylic copolymer synergistic design of copolymerization agent and custom hydroxyl polyester resin, under the premise of not adding component, break through the traditional powder coating "high toughness-high surface quality-heat resistance" incompatible technical contradiction at one stroke, meet the stringent requirements of automobile chassis, outdoor electric box and other scenes to coating comprehensive performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of powder coating production, and particularly relates to a high-toughness mixed powder coating and a preparation method thereof. BACKGROUND

[0002] As an environmentally friendly coating material, powder coating is widely used in metal surface protection and decoration. In recent years, with the demand for lightweight vehicles, fine appearance of household appliances and weather resistance of outdoor facilities, the mechanical properties (such as toughness and impact resistance) of the coating have become the core indicators. However, the existing powder coating system is prone to cracking and peeling due to insufficient toughness under high-low temperature alternation, mechanical vibration or long-term outdoor exposure, which seriously affects the service life of the product.

[0003] Traditional polyester / epoxy mixed powder coating improves toughness by adding rubber elastomer (such as nitrile rubber), but such toughening agent can cause the following problems: ① poor compatibility with the resin matrix, increasing the surface roughness of the coating (Ra>1.5μm), affecting the appearance; ② decreased heat resistance, yellowing index ΔYI>3.0 after 200℃ baking; ③ easy migration of elastomer to the coating interface during curing, reducing the adhesion (crosshatch method) from 0 to 2.

[0004] Automobile chassis parts, outdoor high-voltage electrical boxes and other scenarios require high toughness (impact resistance≥70 cm·kg), moisture and heat resistance (1000h salt spray test without blistering) and high adhesion (crosshatch method 0 level) of the coating at the same time, and the existing technology cannot meet all the requirements. Simply increasing the amount of toughening agent or introducing new components can easily cause phase separation problems, and it is urgent to achieve performance breakthrough through component synergy and process optimization. SUMMARY

[0005] The purpose of the present application is to provide a high-toughness mixed powder coating and a preparation method thereof to improve the high toughness, moisture and heat resistance and high adhesion of the coating.

[0006] The purpose of the present application can be achieved by the following technical solutions:

[0007] A high-toughness mixed powder coating, comprising the following raw materials by mass:

[0008] epoxy resin 55 parts;

[0009] hydroxyl polyester resin 42-45 parts;

[0010] core-shell acrylic copolymer 22-30 parts;

[0011] nanosilica 5 parts;

[0012] titanium dioxide 20 parts;

[0013] leveling agent 1.0-1.2 parts;

[0014] Melamine crosslinking agent 1.4-1.5 parts.

[0015] Further, the hydroxyl polyester resin comprises the following raw materials by mass fraction:

[0016] Terephthalic acid 35 parts;

[0017] Isophthalic acid 15 parts;

[0018] Adipic acid 8-10 parts;

[0019] Trimellitic anhydride 4-5 parts;

[0020] Neopentyl glycol 25 parts;

[0021] Trimethylolpropane 7-8 parts;

[0022] Monobutyl tin oxide 0.3-0.5 parts.

[0023] Further, the preparation method of the hydroxyl polyester resin comprises the following steps:

[0024] A1, according to the mass fraction, the raw materials are weighed, terephthalic acid, isophthalic acid, adipic acid, neopentyl glycol, trimethylolpropane are added into the reaction kettle, and the temperature is raised to 180℃ under nitrogen protection Esterification 2-3h, obtain the mixture;

[0025] A2, trimellitic anhydride and monobutyl tin oxide are added to the mixture in A1, after completion, the reaction kettle is heated to 200-210℃, and the reaction is carried out under constant temperature and stirring until the acid value reaches 15±1mg KOH / g, after completion, dehydration under reduced pressure until the acid value is ≤5mg KOH / g, after completion, the material is cooled and discharged, and the hydroxyl polyester resin is obtained.

[0026] Further, the core-shell acrylic copolymer comprises the following raw materials by mass fraction:

[0027] Butyl acrylate 70 parts;

[0028] Methyl methacrylate 20 parts;

[0029] Diacetone acrylamide 8 parts;

[0030] Glycidyl methacrylate 30 parts;

[0031] Styrene 60 parts;

[0032] Acrylonitrile 10 parts;

[0033] Sodium dodecyl sulfate 2 parts;

[0034] Alkylphenol polyoxyethylene ether 1 part;

[0035] Potassium persulfate 1 part;

[0036] Deionized water 150 parts.

[0037] Further, the preparation method of the core-shell acrylic copolymer comprises the following steps:

[0038] B1, according to the mass parts, add 1.0 parts of sodium dodecyl sulfate, 0.5 parts of alkylphenol polyoxyethylene ether, butyl acrylate, methyl methacrylate and diacetone acrylamide to 50 parts of deionized water, high-speed shearing emulsification for 15-20 min, to obtain a core layer pre-emulsion;

[0039] B2, mix the remaining 100 parts of deionized water, 0.5 parts of sodium dodecyl sulfate, 0.4 parts of potassium persulfate, and heat to 80-85°C under nitrogen protection, drop the core layer pre-emulsion, drop in 2h, keep the reaction for 2-3h, after completion, get the core layer emulsion;

[0040] B3, mix glycidyl methacrylate, styrene, acrylonitrile, 0.5 parts of sodium dodecyl sulfate and 0.5 parts of alkylphenol polyoxyethylene ether, emulsify at 1000 rpm for 10-15 min, to obtain a shell layer pre-emulsion;

[0041] B4, add the remaining 0.6 parts of potassium persulfate to the core layer emulsion, heat the system to 85-90°C, then add the shell layer pre-emulsion dropwise, drop in 2h, keep the reaction for 3-4h, after completion, cool to 35-40°C, get the emulsion, then add calcium chloride dropwise to the emulsion, which is 5% of the mass of the emulsion, to break the emulsion, after completion, filter, wash 3 times, finally collect the solid components by filtration, and dry the solid components at 60-80°C under vacuum for 24h, to obtain the core-shell acrylic copolymer.

[0042] Further, the preparation method of the high-toughness hybrid powder coating comprises the following steps:

[0043] S1, premix: according to the mass parts, then mix the epoxy resin, hydroxyl polyester resin and core-shell acrylic copolymer in a high-speed mixer for 5-10 min, after completion, get the premix;

[0044] S2, dispersion: add nano-silicon dioxide, titanium dioxide, leveling agent and melamine crosslinking agent to the premix in S1, melt and extrude through a twin-screw extruder, to obtain an extruded material;

[0045] S3, crushing: crush the extruded material in S2 to a particle size D 50 =40μm by liquid nitrogen cryogenic crushing, after completion, get the high-toughness hybrid powder coating.

[0046] Further, the model of the epoxy resin is E-12; the particle size of the nano-silica is 30 nm; the model of the titanium white powder is R-706; the model of the leveling agent is BYK-361N; and the model of the melamine crosslinking agent is CYMEL 303LF.

[0047] Further, the temperature setting of the twin-screw extruder is as follows: 85-90 DEG C in region I and 105-110 DEG C in region II.

[0048] The present application has the following advantages:

[0049] The present application provides a high-toughness hybrid powder coating and a preparation method thereof.

[0050] I. Coating toughness improvement:

[0051] (1) Core data comparison: The impact resistance of Examples 5-6 is 78 cm·kg and 80 cm·kg, respectively, far exceeding that of Comparative Example 1 (68 cm·kg) and Comparative Example 3 (30 cm·kg), and significantly higher than the industry demand threshold (≥70 cm·kg) in the background technology.

[0052] (2) Key factor analysis:

[0053] a. Toughening effect of core-shell acrylic copolymer: The impact resistance of Comparative Example 3 (without core-shell copolymer) drops to 30 cm·kg, proving that the core-shell structure (soft core is butyl acrylate / diacetone acrylamide, and hard shell contains epoxy groups) significantly improves toughness through stress dispersion mechanism.

[0054] b. Synergistic effect of self-made hydroxyl polyester resin: The impact resistance of Comparative Example 1 (replaced by commercially available polyester) drops to 68 cm·kg, while that of Comparative Example 2 (completely removes polyester) is only 32 cm·kg, indicating that the combination of flexible chain segment (adipic acid) and heat-resistant monomer (trimellitic anhydride) in the self-made resin is the basis for maintaining high toughness.

[0055] II. Surface smoothness and heat resistance:

[0056] (1) Surface roughness optimization: The Ra value of Examples 5-6 is only 0.72-0.75 μm, far lower than that of Comparative Example 1 (0.95 μm), Comparative Example 2 (1.85 μm), and the Ra value of the traditional toughening system in the background technology (>1.5 μm). Reason: The shell layer of the core-shell copolymer (Examples 3-4) contains glycidyl methacrylate (GMA), and the epoxy group reacts with the resin matrix to enhance compatibility, avoiding surface defects caused by elastomer migration.

[0057] (2) Breakthrough of yellowing resistance: ΔYI of 1.8-2.0 after baking at 200℃ for Examples 5-6, better than Comparative Example 1 (2.5), Comparative Example 2 (4.5) and the defects in the background art with ΔYI > 3.0. Key: trimellitic anhydride in self-made polyester resin improves heat resistance, and core-shell structure inhibits molecular chain degradation at high temperature.

[0058] Three, synergistic enhancement of adhesion and corrosion resistance:

[0059] (1) Adhesion stability: the adhesion of Examples 5-6 is all 0 grade (crosshatch method), while Comparative Examples 2-3 deteriorate to 3 and 4 grades respectively. Mechanism: the shell layer of core-shell copolymer forms chemical bonding with the substrate through epoxy groups (GMA), and the trimethylolpropane crosslinking monomer of self-made polyester enhances the interfacial bonding force.

[0060] (2) Improved salt spray resistance: the salt spray resistance time of Example 6 is 1480 hours (no blistering), which is increased by 45% compared with Comparative Example 1 (1020 hours), and is much higher than Comparative Example 3 (350 hours). Reason: nano-silicon dioxide (5 parts) is uniformly dispersed under the support of core-shell structure, forming a dense shielding layer; at the same time, the hydrolytic stability of the ester bond of self-made polyester is better than that of commercially available resin (Comparative Example 1).

[0061] Conclusion: through the synergistic design of core-shell acrylic copolymer toughener and custom hydroxyl polyester resin, the technical contradiction that traditional powder coatings cannot have high toughness, high surface quality and heat resistance at the same time is broken through without adding new components, which meets the stringent requirements of automobile chassis, outdoor electrical box and other scenes for the comprehensive performance of the coating. DETAILED DESCRIPTION

[0062] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application. Meanwhile, the raw materials, reagents or devices used in the following embodiments are commercially available or can be obtained by known methods if not otherwise specified.

[0063] Example 1

[0064] Preparation of hydroxyl polyester resin:

[0065] First, the hydroxyl polyester resin includes the following raw materials by mass:

[0066] terephthalic acid (industrial grade, purity ≥ 99%) 35 parts;

[0067] Isophthalic acid (industrial grade, purity ≥ 98%) 15 parts;

[0068] Adipic acid (flexible chain segment, purity ≥ 99%) 8 parts;

[0069] Trimellitic anhydride (heat-resistant monomer, purity ≥ 98%) 4 parts;

[0070] Neopentyl glycol (industrial grade) 25 parts;

[0071] Trimethylolpropane (crosslinking monomer) 7 parts;

[0072] Monobutyl tin oxide (catalyst) 0.3 parts.

[0073] Then, the preparation method of the hydroxyl polyester resin comprises the following steps:

[0074] A1, according to the above mass parts, the raw materials are weighed, terephthalic acid, isophthalic acid, adipic acid, neopentyl glycol, trimethylolpropane are added into the reaction kettle, and esterification is carried out under nitrogen protection at 180℃ for 2h, and the mixed material is obtained;

[0075] A2, trimellitic anhydride and catalyst monobutyl tin oxide are added into the mixed material in A1, after completion, the reaction kettle is heated to 200℃ again, and constant temperature stirring reaction is carried out until the acid value reaches 15±1mg KOH / g, after completion, dehydration under reduced pressure (-0.09MPa) is carried out until the acid value is ≤5mg KOH / g, and detection shows that in this embodiment, the acid value reaches 5mg KOH / g after dehydration under reduced pressure, after completion, the material is cooled and discharged, and the hydroxyl polyester resin is obtained.

[0076] Example 2

[0077] Preparation of hydroxyl polyester resin:

[0078] Firstly, the hydroxyl polyester resin comprises the following mass parts of raw materials:

[0079] Terephthalic acid (industrial grade, purity ≥ 99%) 35 parts;

[0080] Isophthalic acid (industrial grade, purity ≥ 98%) 15 parts;

[0081] Adipic acid (flexible chain segment, purity ≥ 99%) 10 parts;

[0082] Trimellitic anhydride (heat-resistant monomer, purity ≥ 98%) 5 parts;

[0083] Neopentyl glycol (industrial grade) 25 parts;

[0084] Trimethylolpropane (crosslinking monomer) 8 parts;

[0085] Monobutyl tin oxide (catalyst) 0.5 parts.

[0086] Then, the preparation method of the hydroxy polyester resin comprises the following steps:

[0087] A1. Weigh the raw materials according to the above parts by mass, add terephthalic acid, isophthalic acid, adipic acid, neopentyl glycol, and trimethylolpropane into a reaction kettle, and heat to 180° C. under nitrogen protection for esterification for 3 hours to obtain a mixture;

[0088] A2. Trimellitic anhydride and catalyst monobutyl tin oxide were added to the mixture in A1. After completion, the reactor was heated to 210° C. and stirred at constant temperature until the acid value reached 15±1 mg KOH / g. After completion, the mixture was dehydrated under reduced pressure (-0.09 MPa) to an acid value of ≤5 mg KOH / g. After testing, the dehydration under reduced pressure in this embodiment was performed to an acid value of 4 mg KOH / g. After completion, the mixture was cooled and discharged to obtain a hydroxy polyester resin.

[0089] Example 3

[0090] Preparation of core-shell acrylic copolymer:

[0091] First, the core-shell acrylic copolymer includes the following raw materials in parts by weight:

[0092] Nuclear lamina monomers:

[0093] 70 parts of butyl acrylate;

[0094] 20 parts of methyl methacrylate;

[0095] 8 parts of diacetone acrylamide;

[0096] Shell monomer:

[0097] 30 parts of glycidyl methacrylate;

[0098] 60 parts of styrene;

[0099] 10 parts of acrylonitrile;

[0100] Emulsifier:

[0101] 2 parts of sodium lauryl sulfate;

[0102] 1 part of alkylphenol polyoxyethylene ether;

[0103] Initiator:

[0104] 1 part potassium persulfate;

[0105] 150 parts of deionized water.

[0106] Then, the preparation method of the core-shell acrylic copolymer comprises the following steps:

[0107] B1, pre-emulsified core layer monomer: the raw materials were weighed according to the mass fraction, 1.0 parts of sodium dodecyl sulfate (SDS), 0.5 parts of alkylphenol polyoxyethylene ether (OP-10), butyl acrylate (BA), methyl methacrylate (MMA) and diacetone acrylamide (DAAM) were added to 50 parts of deionized water, and high-speed shearing emulsification was carried out at 1000 rpm for 15 min to obtain a core layer pre-emulsion;

[0108] B2, core layer polymerization: 100 parts of remaining deionized water, 0.5 parts of sodium dodecyl sulfate (SDS) and 0.4 parts of potassium persulfate (KPS) were mixed, and the temperature was raised to 80°C under nitrogen protection. The core layer pre-emulsion was added dropwise (dropped in 2h), and the reaction was kept for 2h. After completion, the core layer emulsion was obtained.

[0109] B3, pre-emulsified shell monomer: glycidyl methacrylate (GMA), styrene (St), acrylonitrile (AN), 0.5 parts of sodium dodecyl sulfate (SDS) and 0.5 parts of alkylphenol polyoxyethylene ether (OP-10) were mixed, and emulsified at 1000 rpm for 10 min to obtain a shell pre-emulsion.

[0110] B4, shell coating: 0.6 parts of remaining potassium persulfate (KPS) was added to the core layer emulsion, the system was heated to 85°C, and then the shell pre-emulsion was added dropwise (dropped in 2h), and the reaction was kept for 3h. After cooling to 35°C, the emulsion was obtained. Then, 5% of calcium chloride was added to the emulsion to break the emulsion. After completion, the solid components were collected by filtration, washed with water for 3 times, and finally dried at 60°C under vacuum for 24h to obtain a white powder of core-shell acrylic copolymer.

[0111] Example 4

[0112] Preparation of core-shell acrylic copolymer:

[0113] Firstly, the core-shell acrylic copolymer includes the following mass fraction of raw materials:

[0114] Core layer monomer:

[0115] Butyl acrylate 70 parts;

[0116] Methyl methacrylate 20 parts;

[0117] Diacetone acrylamide 8 parts;

[0118] Shell monomer:

[0119] Glycidyl methacrylate 30 parts;

[0120] Styrene 60 parts;

[0121] Acrylonitrile 10 parts;

[0122] Emulsifiers:

[0123] Sodium dodecyl sulfate 2 parts;

[0124] Alkylphenol polyoxyethylene ether 1 part;

[0125] Initiator:

[0126] Potassium persulfate 1 part;

[0127] Deionized water 150 parts.

[0128] Then, the preparation method of the core-shell acrylic copolymer comprises the following steps:

[0129] B1, pre-emulsified core layer monomer: according to the mass parts, add 1.0 parts of sodium dodecyl sulfate (SDS), 0.5 parts of alkylphenol polyoxyethylene ether (OP-10), butyl acrylate (BA), methyl methacrylate (MMA) and diacetone acrylamide (DAAM) to 50 parts of deionized water, and emulsify at 1000 rpm for 20 minutes to obtain a core layer pre-emulsion;

[0130] B2, core layer polymerization: mix the remaining 100 parts of deionized water, 0.5 parts of sodium dodecyl sulfate (SDS), and 0.4 parts of potassium persulfate (KPS), and heat to 85°C under nitrogen protection, then add the core layer pre-emulsion dropwise (within 2 hours), and react for 3 hours, then cool to 40°C, and add 5% of calcium chloride based on the mass of the emulsion to break the emulsion, then filter, wash with water for 3 times, and finally collect the solid components by filtration, and dry the solid components at 80°C under vacuum for 24 hours to obtain a white powder of core-shell acrylic copolymer.

[0131] B3, pre-emulsified shell monomer: mix glycidyl methacrylate (GMA), styrene (St), acrylonitrile (AN), 0.5 parts of sodium dodecyl sulfate (SDS), and 0.5 parts of alkylphenol polyoxyethylene ether (OP-10), and emulsify at 1000 rpm for 15 minutes to obtain a shell pre-emulsion;

[0132] B4, shell coating: add the remaining 0.6 parts of potassium persulfate (KPS) to the core layer emulsion, heat the system to 90°C, then add the shell pre-emulsion dropwise (within 2 hours), and react for 4 hours, then cool to 40°C, and add 5% of calcium chloride based on the mass of the emulsion to break the emulsion, then filter, wash with water for 3 times, and finally collect the solid components by filtration, and dry the solid components at 80°C under vacuum for 24 hours to obtain a white powder of core-shell acrylic copolymer.

[0133] Example 5

[0134] Preparation of high-toughness hybrid powder coating:

[0135] First, the high-toughness hybrid powder coating comprises the following mass parts of raw materials:

[0136] Epoxy resin 55 parts;

[0137] hydroxyl polyester resin prepared in Example 1 42 parts;

[0138] core-shell acrylic copolymer prepared in Example 3 22 parts;

[0139] nano-silica 5 parts;

[0140] titanium dioxide 20 parts;

[0141] leveling agent 1.0 part;

[0142] melamine crosslinking agent 1.4 parts.

[0143] Then, the preparation method of the high-toughness hybrid powder coating includes the following steps:

[0144] S1, premixing: weighing each raw material by mass parts, then mixing the epoxy resin (E-12, epoxy equivalent weight 450-500), the hydroxyl polyester resin prepared in Example 1, and the core-shell acrylic copolymer prepared in Example 3 in a high-speed mixer (rotating speed 2000 rpm) for 5 min, and then obtaining a premixing material;

[0145] S2, dispersion: adding nano-silica (particle size 30 nm), titanium dioxide (R-706, rutile type), leveling agent (BYK-361N), and melamine crosslinking agent (CYMEL 303LF) into the premixing material in S1, and then melt-extruding through a twin-screw extruder (I zone 85°C, II zone 105°C) to obtain an extruded material;

[0146] S3, crushing: crushing the extruded material in S2 to a particle size D 50 =40μm through liquid nitrogen cryogenic crushing, and then obtaining a high-toughness hybrid powder coating.

[0147] Example 6

[0148] Preparation of a high-toughness hybrid powder coating:

[0149] First, the high-toughness hybrid powder coating includes the following raw materials by mass parts:

[0150] epoxy resin 55 parts;

[0151] hydroxyl polyester resin prepared in Example 2 45 parts;

[0152] core-shell acrylic copolymer prepared in Example 4 30 parts;

[0153] nano-silica 5 parts;

[0154] titanium dioxide 20 parts;

[0155] leveling agent 1.2 parts;

[0156] 1.5 parts of melamine crosslinking agent.

[0157] Then, the preparation method of the high-toughness hybrid powder coating comprises the following steps:

[0158] S1, premixing: weighing each raw material according to mass parts, and then mixing epoxy resin (E-12, epoxy equivalent 450-500), hydroxy polyester resin prepared in Example 2, and core-shell acrylic copolymer prepared in Example 4 in a high-speed mixer (speed 2000 rpm) for 10 minutes to obtain a premix;

[0159] S2, dispersion: nano-silica (particle size 30 nm), titanium dioxide (R-706, rutile type), leveling agent (BYK-361N) and melamine cross-linking agent (CYMEL 303LF) were added to the premix in S1, and melt-extruded through a twin-screw extruder (90°C in zone I and 110°C in zone II) to obtain an extrudate;

[0160] S3, crushing: the extrudate in S2 is crushed to a particle size of D by deep cooling with liquid nitrogen. 50 =40μm, after completion, a high-toughness hybrid powder coating is obtained.

[0161] Comparative Example 1

[0162] Comparative Example 1 is the control group of Example 6, except that the hydroxy polyester resin prepared in Example 2 of the raw material in Example 6 is replaced by a commercially available polyester resin (model SJ4ET, purchased from Anhui Shenjian New Materials Co., Ltd.), and the remaining raw materials, raw material amounts and preparation steps remain the same as in Example 6, and finally a high-toughness hybrid powder coating is obtained.

[0163] Comparative Example 2

[0164] Comparative Example 2 is the control group of Example 6. The hydroxy polyester resin prepared in Example 2 of the raw material in Example 6 is removed, and the remaining raw materials, raw material amounts and preparation steps are kept consistent with those in Example 6, and finally a high-toughness hybrid powder coating is obtained.

[0165] Comparative Example 3

[0166] Comparative Example 3 is the control group of Example 6. The core-shell acrylic copolymer prepared in Example 4 is removed from the raw materials in Example 6, and the remaining raw materials, raw material amounts and preparation steps are kept consistent with those in Example 6, and finally a high-toughness hybrid powder coating is obtained.

[0167] Test Example 1

[0168] The high-toughness hybrid powder coatings prepared in Example 5 to Example 6 and Comparative Example 1 to Comparative Example 3 were subjected to performance tests. The high-toughness hybrid powder coatings were electrostatically sprayed onto the surface of phosphatized steel plates to form test samples which were cured at 130℃ / 15min+180℃ / 10min in stages. The performance test process of the test samples was as follows, and the test results are shown in Table 1.

[0169] (1) Impact resistance (GB / T 1732-1993): 1kg ball impact on the back of the coating, and the maximum height (cm·kg) without cracking was recorded;

[0170] (2) Adhesion (GB / T 9286-1998): crosshatch method (1mm x 1mm), and the peeling grade (0 is the best) was observed after the tape was torn;

[0171] (3) Surface roughness Ra (GB / T 3505-2009): measured by a surface profilometer;

[0172] (4) Salt spray resistance (GB / T 1771-2007): 5% NaCl solution was sprayed, and the blistering time of the coating (h) was recorded;

[0173] (5) Yellowing resistance: color difference ΔYI (standard white plate comparison) was measured after 200℃ baking for 30min.

[0174] Table 1 Test results

[0175] Item Example 5 Example 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 Impact resistance (cm-kg) 78 80 68 32 30 Adhesion (crosshatch) 0 level 0 level 0 level 3 level 4 level Surface roughness Ra (pm) 0.75 0.72 0.95 1.85 2.10 Salt spray resistance time (h) 1450 1480 1020 480 350 Baking at 200°C ΔYI 2.0 1.8 2.5 4.5 5.0

[0176] It should be noted that in this document, such as the term "comprise, include" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or includes elements inherent to such process, method, article or equipment.

[0177] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A high toughness hybrid powder coating, characterized in that: Including the following raw materials by weight: 55 parts of epoxy resin; 42-45 parts of hydroxy polyester resin; 22-30 parts of core-shell acrylic copolymer; 5 parts of nano silicon dioxide; 20 parts of titanium dioxide; 1.0-1.2 parts of leveling agent; 1.4-1.5 parts of melamine crosslinking agent; The core-shell acrylic copolymer comprises the following raw materials in parts by weight: 70 parts of butyl acrylate; 20 parts of methyl methacrylate; 8 parts of diacetone acrylamide; 30 parts of glycidyl methacrylate; 60 parts of styrene; 10 parts of acrylonitrile; 2 parts of sodium lauryl sulfate; 1 part of alkylphenol polyoxyethylene ether; 1 part potassium persulfate; 150 parts of deionized water; The preparation method of the core-shell acrylic copolymer comprises the following steps: B1. Weigh each raw material in parts by mass, add 1.0 part of sodium lauryl sulfate, 0.5 parts of alkylphenol polyoxyethylene ether, butyl acrylate, methyl methacrylate, and diacetone acrylamide to 50 parts of deionized water, and emulsify at 1000 rpm for 15-20 minutes to obtain a core layer pre-emulsion; B2. Mix the remaining 100 parts of deionized water, 0.5 parts of sodium lauryl sulfate, and 0.4 parts of potassium persulfate, raise the temperature to 80-85° C. under nitrogen protection, add the core layer pre-emulsion dropwise within 2 hours, and keep the temperature for reaction for 2-3 hours to obtain the core layer emulsion; B3, mixing glycidyl methacrylate, styrene, acrylonitrile, 0.5 parts of sodium lauryl sulfate and 0.5 parts of alkylphenol polyoxyethylene ether, and emulsifying at 1000 rpm for 10 to 15 minutes to obtain a shell pre-emulsion; B4. Add the remaining 0.6 parts of potassium persulfate to the core layer emulsion, heat the system to 85-90° C., then dropwise add the shell layer pre-emulsion thereto, complete the dropwise addition within 2 hours, keep the reaction warm for 3-4 hours, and after completion, cool to 35-40° C. to obtain an emulsion, and then dropwise add 5% of the emulsion mass of calcium chloride to the emulsion for demulsification. After completion, filter and wash with water 3 times, and finally collect the solid component by suction filtration. The solid component is placed in a vacuum dryer at 60-80° C. for 24 hours to obtain a core-shell acrylic acid copolymer.

2. A high toughness hybrid powder coating according to claim 1, characterized in that: The preparation method of the hydroxy polyester resin comprises the following steps: A1. Weigh the raw materials according to their mass, add terephthalic acid, isophthalic acid, adipic acid, neopentyl glycol, and trimethylolpropane into a reaction kettle, and heat to 180°C under nitrogen for esterification for 2-3 hours to obtain a mixture; A2. Add trimellitic anhydride and monobutyltin oxide to the mixture in A1. After completion, heat the reactor to 200-210° C. and stir at constant temperature to react until the acid value reaches 15±1 mg KOH / g. After completion, dehydrate under reduced pressure to an acid value of ≤5 mg KOH / g. After completion, cool and discharge the material to obtain a hydroxy polyester resin.

3. The method for preparing a high-toughness hybrid powder coating according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1. Premixing: Weighing each raw material according to parts by mass, and then mixing the epoxy resin, hydroxy polyester resin, and core-shell acrylic copolymer in a high-speed mixer for 5 to 10 minutes to obtain a premix; S2, dispersion: adding nano-silica, titanium dioxide, leveling agent and melamine cross-linking agent to the premix in S1, and melt-extruded through a twin-screw extruder to obtain an extrudate; S3. Crushing: The extrudate in S2 is crushed by deep cooling with liquid nitrogen to a particle size of D50 = 40 μm. After completion, a high-toughness mixed powder coating is obtained.

4. The method for preparing a high-toughness hybrid powder coating according to claim 3, characterized in that: The epoxy resin is of type E-12; the particle size of the nano-silicon dioxide is 30 nm; the titanium dioxide is of type R-706; the leveling agent is of type BYK-361N; and the melamine cross-linking agent is of type CYMEL 303LF.

5. The method for preparing a high-toughness hybrid powder coating according to claim 3, characterized in that: The temperature settings of the twin-screw extruder are: 85-90°C in zone I and 105-110°C in zone II.