Polyester powder coating, preparation method thereof and polyester powder coating

Abstract

The invention provides a polyester powder coating, a preparation method thereof and a polyester powder coating, and belongs to the technical field of coatings. According to the invention, a polyphenol compound modified graphene oxide composite material loaded with nano-zinc oxide is used as a functional filler, and graphene oxide (GO) is used as a main body of the composite material, so that the corrosion resistance of the coating can be enhanced; the GO is modified by using the polyphenol compound, so that the dispersity of the GO in the coating can be effectively improved, and the barrier effect of the GO is enhanced; moreover, the GO and the polyphenol compound can chemically react with the surface of the coating substrate to form chemical bonds, so that the bonding strength of the coating is enhanced, and the protection effect of the coating on the substrate is synergistically improved; according to the invention, the nano ZnO is loaded on the TGO, so that the small-size effect of the TGO can be exerted, small gaps in the coating can be effectively filled, and a certain physical shielding effect on a corrosive medium is achieved; in addition, the functional filler can enable the composite coatings to be combined more tightly, and the wear resistance of the coatings is improved.

Description

Technical Field

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

[0002] Powder coating is a green coating without volatile solvents. It has the characteristics of being solvent-free, pollution-free, recyclable, environmentally friendly, saving energy and resources, reducing labor intensity and having high mechanical strength of the coating film.

[0003] Polyester powder coating is a common powder coating with excellent weather resistance. It is generally used in the fields of automobiles, industrial machinery, shipbuilding anti-corrosion and civil public facilities. However, most of these equipment need to be exposed to the outside for a long time and will be in contact with sewage and rainwater. Due to the presence of ester groups in the polyester structure, it is easy to hydrolyze in a humid environment. When the equipment coated with polyester powder coating is in contact with sewage and rainwater, it is easy to be corroded by acid rain, corroded by sewage, softened or fallen off due to long-term contact with water. In addition, these equipment need to have strong wear resistance, but the coating formed by the existing polyester powder coating has the problem of poor wear resistance.

[0004] Therefore, there is an urgent need to provide a polyester powder coating with corrosion resistance and wear resistance. Summary of the invention

[0005] The object of the present invention is to provide a polyester powder coating and a preparation method thereof and a polyester powder coating. The coating obtained by the polyester powder coating provided by the present invention has corrosion resistance and wear resistance.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a polyester powder coating, which comprises the following components by weight: 1000 parts of polyester resin, 70-80 parts of curing agent, 7.5-12.5 parts of leveling agent, 2-5 parts of benzoin, 2-3 parts of brightener and 5-20 parts of functional filler;

[0008] The functional filler is a polyphenol compound-modified graphene oxide composite material loaded with nano zinc oxide.

[0009] Preferably, the method for preparing the functional filler comprises the following steps:

[0010] (1) mixing a polyphenol compound, water and graphene oxide, and performing a reduction reaction to obtain polyphenol-modified graphene oxide;

[0011] (2) mixing the polyphenol-modified graphene oxide obtained in step (1) with a solvent to obtain a polyphenol-modified graphene oxide suspension;

[0012] (3) The polyphenol-modified graphene oxide suspension obtained in step (2) and the zinc salt solution are mixed to obtain a mixed solution, the pH value of the mixed solution is adjusted to 6.5-7.5, and then double decomposition and decomposition reactions are performed to obtain a polyphenol compound-modified graphene oxide composite material loaded with nano zinc oxide.

[0013] Preferably, the polyphenol compounds in step (1) include tea polyphenols and / or proanthocyanidins.

[0014] Preferably, in step (1), the mass ratio of the polyphenol compound to graphene oxide is 2 to 8:1.

[0015] Preferably, the temperature of the reduction reaction in step (1) is 68-72° C., and the time of the reduction reaction is 7-10 h.

[0016] Preferably, in the step (3), the mass ratio of the zinc salt in the zinc salt solution to the polyphenol-modified graphene oxide in the polyphenol-modified graphene oxide suspension is 2 to 6:1.

[0017] Preferably, the temperature of the metathesis and decomposition reaction in step (3) is 79-82° C., and the time of the metathesis and decomposition reaction is 20-40 min.

[0018] Preferably, the curing agent includes TGIC or MT239.

[0019] The present invention also provides a method for preparing the polyester powder coating described in the above technical solution, comprising: mixing polyester resin, curing agent, leveling agent, benzoin, brightener and functional filler, and then sequentially performing melt extrusion, tableting, crushing and screening to obtain the polyester powder coating.

[0020] The present invention also provides a polyester powder coating, which is obtained by spraying and curing the polyester powder coating described in the above technical solution or the polyester powder prepared by the preparation method described in the above technical solution.

[0021] The present invention provides a polyester powder coating, which comprises the following components by weight: 1000 parts of polyester resin, 70-80 parts of curing agent, 7.5-12.5 parts of leveling agent, 2-5 parts of benzoin, 2-3 parts of brightener and 5-20 parts of functional filler; the functional filler is a polyphenol compound-modified graphene oxide composite material loaded with nano zinc oxide. The present invention uses a polyphenol compound-modified graphene oxide composite material loaded with nano zinc oxide as a functional filler, wherein graphene oxide (GO) is the main body of the composite material, and its unique two-dimensional sheet structure can form a "maze effect" in the coating, prolong the permeation path of oxygen, water, ions and electrolytes, and enhance the corrosion resistance of the coating; the present invention uses polyphenol compounds as natural green modifiers to modify GO, which can effectively improve the dispersibility of GO in the coating to enhance the barrier effect of GO; and there are a large number of -OH functional groups on the surface of GO, and the surface of the polyphenol compound contains a variety of functional functional groups (such as -OH and -NH2, etc.), both of which can The surface of the coating substrate reacts chemically to form a chemical bond, enhancing the adhesion strength of the coating, thereby synergistically improving the protective effect of the coating on the substrate; the present invention loads nano ZnO on tea polyphenol-modified graphene oxide (TGO), which can exert its small size effect, effectively fill the small gaps in the coating, and play a physical shielding role on the corrosive medium; and when ZnO is loaded on the surface of TGO, since the surface of this functional filler has rich chemical functional groups, it can be closely combined with the polyester coating, so that when the coating is subjected to external friction, TGO and ZnO play a synergistic role, so that the composite coatings are more tightly combined, and the composite coatings are more difficult to separate, so that the wear resistance is better. The results of the embodiment show that the coating formed after the polyester powder coating provided by the present invention is cured has excellent corrosion resistance and wear resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of preparing polyester powder coating and polyester powder coating for the implementation of the present invention;

[0023] Figure 2 This is a Bode impedance modulus diagram of the polyester powder coating prepared in Comparative Example 3 of the present invention;

[0024] Figure 3 This is a Bode impedance modulus diagram of the polyester powder coating prepared in Example 4 of the present invention;

[0025] Figure 4 This is a Bode impedance modulus diagram of the polyester powder coating prepared in Example 5 of the present invention;

[0026] Figure 5 This is a Bode impedance modulus diagram of the polyester powder coating prepared in Example 6 of the present invention;

[0027] Figure 6This is a Bode impedance modulus diagram of the polyester powder coating prepared in Comparative Example 4 of the present invention;

[0028] Figure 7 The anti-corrosion performance test results of the polyester powder coatings prepared in Examples 4 to 6 of the present invention and Comparative Examples 3 to 4 after being immersed in a 5.0% NaCl solution for 0 hours and 168 hours;

[0029] Figure 8 The corrosion resistance test results of the polyester coatings prepared in Examples 4 to 6 of the present invention and Comparative Examples 3 to 4 are shown in FIG.

[0030] Fig. 9 This is a graph showing the wear resistance test results of the polyester powder coating prepared in Example 6 of the present invention and Comparative Example 3. DETAILED DESCRIPTION

[0031] The invention provides a polyester powder coating, which comprises the following components by weight: 1000 parts of polyester resin, 70-80 parts of curing agent, 7.5-12.5 parts of leveling agent, 2-5 parts of benzoin, 2-3 parts of brightener and 5-20 parts of functional filler; the functional filler is a polyphenol compound modified graphene oxide composite material loaded with nano zinc oxide.

[0032] In the present invention, unless otherwise specified, the raw materials used in the present invention are all commercially available products well known in the art.

[0033] The polyester powder coating provided by the present invention comprises 1000 parts of polyester resin by weight. In the present invention, the polyester resin preferably comprises SJ4868, SJ4866 or SJ4801. The present invention uses polyester resin as the resin component of the polyester powder coating.

[0034] The polyester powder coating provided by the present invention comprises 70 to 80 parts, preferably 75 to 80 parts, of a curing agent based on 1000 parts by weight of the polyester resin. In the present invention, the curing agent preferably comprises TGIC or MT239. The curing agent used in the present invention can cure the polyester powder coating to form a coating.

[0035] The polyester powder coating provided by the present invention comprises 7.5 to 12.5 parts, preferably 10 to 12 parts, of a leveling agent based on 1000 parts by weight of the polyester resin. In the present invention, the leveling agent is preferably PV88. By adding a leveling agent, the present invention can reduce the surface tension of the coating, improve the leveling and uniformity of the coating, and promote the coating to form a flat, smooth, and uniform coating film during the film forming process.

[0036] The polyester powder coating provided by the present invention comprises 2 to 5 parts, preferably 3 to 5 parts, of benzoin based on 1000 parts by weight of the polyester resin. The present invention can effectively remove bubbles in the molten powder coating, prevent pinhole defects from appearing on the surface of the paint film, and eliminate the pinhole phenomenon generated during the spraying process by adding benzoin as a defoamer.

[0037] Based on 1000 parts by weight of the polyester resin, the polyester powder coating provided by the present invention includes 2 to 3 parts of a brightener, preferably 3 parts. In the present invention, the brightener is preferably 701B. In the present invention, the brightener can increase the gloss of the polyester coating and improve the appearance quality of the coating.

[0038] Based on 1000 parts by weight of polyester resin, the polyester powder coating provided by the present invention includes 5 to 20 parts of functional fillers, preferably 10 to 20 parts. In an embodiment of the present invention, the functional filler can be 5 parts, 10 parts, 15 parts or 20 parts. In the present invention, the functional filler is a polyphenol compound-modified graphene oxide composite material loaded with nano zinc oxide. The present invention modifies GO by adding functional fillers and using polyphenol compounds to improve the dispersibility of GO in the coating and enhance the corrosion resistance and wear resistance of the coating; the present invention loads nano ZnO on TGO, which can give play to its small size effect, can effectively fill small gaps in the coating, and play a certain physical shielding role against corrosive media; and, the composite coatings are more tightly bonded to improve the wear resistance of the coating.

[0039] In the present invention, the diameter of the nano zinc oxide in the polyphenol compound modified graphene oxide composite material loaded with nano zinc oxide is preferably 50±10 nm. The diameter of the nano zinc oxide in the functional filler provided by the present invention is within the above range, which has a better nano effect.

[0040] In the present invention, the mass ratio of nano zinc oxide to polyphenol modified graphene oxide in the polyphenol compound modified graphene oxide composite material loaded with nano zinc oxide is preferably 2 to 6: 1. The present invention controls the mass ratio of the two within the above range, which is more conducive to uniform distribution of zinc oxide in polyphenol modified graphene oxide.

[0041] In the present invention, the method for preparing the functional filler preferably comprises the following steps:

[0042] (1) mixing a polyphenol compound, water and graphene oxide, and performing a reduction reaction to obtain polyphenol-modified graphene oxide;

[0043] (2) mixing the polyphenol-modified graphene oxide obtained in step (1) with a solvent to obtain a polyphenol-modified graphene oxide suspension;

[0044] (3) The polyphenol-modified graphene oxide suspension obtained in step (2) and the zinc salt solution are mixed to obtain a mixed solution, the pH value of the mixed solution is adjusted to 6.5-7.5, and then double decomposition and decomposition reactions are sequentially performed to obtain a polyphenol compound-modified graphene oxide composite material loaded with nano zinc oxide.

[0045] The present invention preferably mixes a polyphenol compound, water and graphene oxide, and performs a reduction reaction to obtain polyphenol-modified graphene oxide.

[0046] In the present invention, the polyphenol compound preferably includes tea polyphenol and / or proanthocyanidin. The present invention adopts the above polyphenol compound, which has more functional groups and can modify graphene oxide and improve the dispersibility of graphene oxide in the coating.

[0047] The present invention has no special limitation on the source and size of the graphene oxide, and conventional commercially available graphene oxide or graphene oxide prepared by conventional methods may be used.

[0048] In the present invention, the mass ratio of the polyphenol compound to graphene oxide is preferably 2 to 8: 1, more preferably 5: 1. The present invention controls the usage of the two within the above range, which can fully improve the dispersibility of graphene oxide in the coating.

[0049] In the present invention, the water is used as a dispersion medium. The present invention does not impose any particular limitation on the amount of the water, which can be adjusted according to the amounts of the polyphenol compound and graphene oxide used, as long as the two are able to react fully.

[0050] The present invention has no particular limitation on the method for mixing the polyphenol compound, water and graphene oxide, as long as the polyphenol compound and graphene oxide can be fully dispersed in water. In the present invention, the method for mixing the polyphenol compound, water and graphene oxide is preferably ultrasound.

[0051] In an embodiment of the present invention, the method for mixing the polyphenol compound, water and graphene oxide is preferably: subjecting the polyphenol compound and water to a first ultrasonic dispersion to obtain a polyphenol compound solution; and adding graphene oxide to the polyphenol compound solution to a second ultrasonic dispersion.

[0052] In the present invention, the ultrasonic power of the first ultrasonic dispersion is preferably 35-45 kHz, more preferably 40-45 kHz; the ultrasonic time of the first ultrasonic dispersion can be 30 min; and the temperature of the first ultrasonic dispersion is preferably 25±5°C.

[0053] In the present invention, the ultrasonic power of the second ultrasonic dispersion is preferably 35-45 kHz, more preferably 40-45 kHz; the ultrasonic time of the second ultrasonic dispersion can be 30 min; and the temperature of the second ultrasonic dispersion is preferably 25±5°C.

[0054] In the present invention, the temperature of the reduction reaction is preferably 68-72° C., more preferably 70° C.; the time of the reduction reaction is preferably 7-10 hours, more preferably 8 hours. In the present invention, polyphenols modify graphene oxide through a reduction reaction.

[0055] In the present invention, after the reduction reaction, the suspension obtained by the reduction reaction is preferably filtered, washed and dried in sequence to obtain polyphenol-modified graphene oxide. The present invention has no special restrictions on the operation methods of the filtration, washing and drying, and conventional filtration, washing and drying methods can be used. In an embodiment of the present invention, the washing agent can be deionized water; the drying temperature can be 60° C., and the drying time can be 48 hours.

[0056] After obtaining the polyphenol-modified graphene oxide, the present invention preferably mixes the polyphenol-modified graphene oxide with a solvent to obtain a polyphenol-modified graphene oxide suspension.

[0057] The present invention has no particular limitation on the type of the solvent, and any solvent that can fully disperse the polyphenol-modified graphene oxide and dissolve the zinc salt can be used. In an embodiment of the present invention, the solvent can be anhydrous ethanol.

[0058] The present invention does not impose any particular limitation on the amount of the solvent, and the amount can be adjusted to sufficiently disperse the polyphenol-modified graphene oxide. In an embodiment of the present invention, when the mass of the polyphenol-modified graphene oxide is 0.5 to 2 g, the volume of the solvent can be 50 mL.

[0059] The present invention has no particular limitation on the method for mixing the polyphenol-modified graphene oxide and the solvent, as long as the polyphenol-modified graphene oxide can be fully dispersed in the solvent. In an embodiment of the present invention, the method for mixing the polyphenol-modified graphene oxide and the solvent is preferably ultrasound; the power of the ultrasound is preferably 35 to 45 kHz, more preferably 40 to 45 kHz; the time of the ultrasound can be 30 minutes; the temperature of the ultrasound is preferably 25±5°C.

[0060] After obtaining the polyphenol-modified graphene oxide suspension, the present invention mixes the polyphenol-modified graphene oxide suspension and a zinc salt solution to obtain a mixed solution, adjusts the pH value of the mixed solution to 7, and then performs double decomposition and decomposition reactions to obtain a polyphenol compound-modified graphene oxide composite material loaded with nano zinc oxide.

[0061] In the present invention, the zinc salt in the zinc salt solution preferably includes anhydrous zinc acetate, zinc sulfate dihydrate or zinc sulfate pentahydrate, and more preferably anhydrous zinc acetate.

[0062] In the present invention, the solvent in the zinc salt solution is preferably anhydrous ethanol.

[0063] The present invention does not specifically limit the amount of the solvent, as long as it can dissolve the zinc salt. In an embodiment of the present invention, when the mass of the zinc salt is 4.0 g, the volume of the solvent can be 100 mL.

[0064] In the present invention, the mass ratio of the zinc salt in the zinc salt solution to the polyphenol-modified graphene oxide in the polyphenol-modified graphene oxide suspension is preferably 2 to 6: 1, more preferably 4 to 5: 1. The present invention controls the amount of the two within the above range, which is more conducive to uniformly distributing the formed zinc oxide in the polyphenol-modified graphene oxide.

[0065] The present invention has no particular limitation on the method of mixing the polyphenol-modified graphene oxide suspension and the zinc salt solution, as long as the two can be mixed evenly. In an embodiment of the present invention, the mixing method can be stirring.

[0066] In the present invention, the reagent for adjusting the pH value of the mixed solution is preferably a sodium hydroxide solution. In an embodiment of the present invention, the concentration of the sodium hydroxide solution can be 1 mol / L. The present invention can promote the double decomposition reaction of zinc salt to obtain zinc oxide by adjusting the pH value of the mixed solution to 7.

[0067] In the present invention, the temperature of the double decomposition and decomposition reaction is preferably 79-82°C, more preferably 80°C; the time of the double decomposition and decomposition reaction is preferably 20-40min, more preferably 30min. In the present invention, the time of the double decomposition and decomposition reaction is preferably the time after the pH value of the mixed solution is adjusted to 6.5-7.5. In the present invention, the double decomposition reaction is preferably carried out under stirring. The present invention is more conducive to promoting the double decomposition reaction more fully by controlling the temperature and time within the above range.

[0068] In the present invention, the system is preferably left to stand for 24 hours after the double decomposition and decomposition reactions. The present invention can promote the complete formation of zinc oxide precipitation and the growth of crystals by standing still.

[0069] The present invention preferably performs suction filtration, washing and drying on the suspension obtained by standing still in sequence after standing still, so as to obtain a polyphenol compound-modified graphene oxide composite material loaded with nano zinc oxide. The present invention has no special restrictions on the operation methods of the suction filtration, washing and drying, and conventional suction filtration, washing and drying methods can be adopted. In an embodiment of the present invention, the washing agent can be deionized water; the drying temperature can be 60° C.; and the drying time can be 48 hours.

[0070] The present invention can enhance the corrosion resistance of the coating and improve the protective effect of the coating on the substrate by improving the functional filler; the present invention loads nano ZnO on TGO, which can exert its small size effect, effectively fill small gaps in the coating, and play a certain physical shielding role on the corrosive medium; and when ZnO is loaded on the surface of TGO, it can be tightly combined with the polyester coating, so that when the coating is subjected to external friction, TGO and ZnO play a synergistic role, so that the composite coatings are more tightly combined, the composite coatings are more difficult to separate, and the wear resistance of the coating is improved.

[0071] The present invention also provides a method for preparing the polyester powder coating described in the above technical solution, comprising: mixing polyester resin, curing agent, leveling agent, benzoin, brightener and functional filler, and then sequentially performing melt extrusion, tableting, crushing and screening to obtain the polyester powder coating.

[0072] In the present invention, the polyester resin, curing agent, leveling agent, benzoin, brightener and functional filler are preferably dried first and then mixed. The present invention can prevent the moisture in each raw material from affecting the performance of the coating by drying. The present invention has no special limitation on the drying method, and a conventional drying method can be used to fully remove the moisture in each raw material.

[0073] The present invention has no particular limitation on the method of mixing the polyester resin, curing agent, leveling agent, benzoin, brightener and functional filler, as long as the components can be mixed evenly. In an embodiment of the present invention, the mixing method can be stirring, and the stirring device can be a stirrer.

[0074] In the present invention, the melt extrusion device is preferably an extruder. In an embodiment of the present invention, the temperature of the first zone of the extruder is preferably 95±5°C, the temperature of the second zone of the extruder is preferably 120±5°C, the temperature of the third zone of the extruder is preferably 110±5°C, and the screw speed of the extruder is preferably 40±5r / min. The present invention adopts the above parameters as the basis, which is more conducive to ensuring the stability of the coating.

[0075] The present invention has no special limitation on the tableting operation, and the melt-extruded material can be pressed into tablets. The tableting of the present invention is more conducive to subsequent crushing.

[0076] The present invention has no special limitation on the crushing method, and a conventional crushing method can be used to crush the flakes. In an embodiment of the present invention, the crushing device is preferably a high-speed universal crusher.

[0077] In the present invention, the sieve hole diameter of the sieving is preferably 200 meshes. The present invention uses the above-mentioned sieve hole size for sieving, which can make the coating have a lower and more uniform particle size, which is more conducive to obtaining a coating with uniform thickness when the coating is used.

[0078] The preparation method provided by the invention is simple to operate and can obtain polyester powder coating with uniform particle size distribution.

[0079] The present invention also provides a polyester powder coating, which is obtained by spraying and curing the polyester powder coating described in the above technical solution or the polyester powder prepared by the preparation method described in the above technical solution.

[0080] The present invention has no special limitation on the spraying parameters, and conventional spraying methods can be used to adjust the parameters so that the polyester powder coating can form a coating layer with uniform thickness on the substrate. In an embodiment of the present invention, the spraying method can be electrostatic spraying.

[0081] In the present invention, the curing temperature is preferably 195-210° C., more preferably 200° C.; the curing time is preferably 8-12 min, more preferably 10-12 min. Under the above parameters, the present invention can fully cure the polyester powder coating to form a polyester powder coating.

[0082] In the present invention, the schematic diagram of preparing the polyester powder coating and the polyester powder coating is as shown in Figure 1 As shown. Figure 1 It can be seen that GO is modified by TP to obtain TGO, TGO is reacted with anhydrous zinc acetate and sodium hydroxide as raw materials to obtain a polyphenol compound modified graphene oxide composite material loaded with nano zinc oxide (TGO@ZnO), TGO@ZnO is used as a functional filler, mixed with polyester resin, curing agent, leveling agent, brightening agent and benzoin, melt blended and extruded, crushed and sieved, and then electrostatically sprayed, and then cured at high temperature to obtain a polyester powder coating. The present invention can improve the wear resistance and corrosion resistance of the polyester powder coating by improving the functional filler.

[0083] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. 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.

[0084] Example 1

[0085] A polyester powder coating, comprising the following components by weight: 1000 parts of carboxyl-terminated saturated polyester (SJ4868), 75 parts of triglycidyl isocyanurate (TGIC) as a curing agent, 10 parts of a leveling agent PV88, 3 parts of benzoin, 3 parts of a brightener 701B, and 5 parts of a functional filler; the functional filler is a polyphenol compound-modified graphene oxide composite material loaded with nano zinc oxide (TGO@ZnO);

[0086] The preparation method of the TGO@ZnO is:

[0087] (1) Take 2.5g of tea polyphenols (TP), add it to 100mL of deionized water, and ultrasonically disperse it at 40kHz and 25℃ for 30min to obtain a TP solution; then weigh TP and graphene oxide (GO) at a mass ratio of 5:1, add it to the TP solution, and ultrasonically disperse it at 40kHz and 25℃ for 30min to obtain a uniformly dispersed TP / GO suspension; reflux the TP / GO suspension at 70℃ for 8h. After the reaction is completed, filter and wash the sample with deionized water for 5 times, and finally dry the filtered product at 60℃ for 48h to obtain tea polyphenol modified graphene oxide powder (TGO);

[0088] (2) adding 1 g of the TGO obtained in step (1) to 50 mL of anhydrous ethanol, and ultrasonically dispersing the mixture at 40 kHz and 25° C. for 30 min to obtain a TGO suspension;

[0089] (3) mixing the polyphenol-modified graphene oxide suspension obtained in step (2) and the zinc salt solution under magnetic stirring at 80° C., then titrating with 1 mol / L NaOH solution to pH=7, and continuing stirring for 30 min. After the stirring is completed, standing for 24 h, filtering and washing the sample with deionized water for 5 times, and finally drying the product at 60° C. for 48 h to obtain TGO@ZnO; the preparation method of the zinc salt solution is as follows: weighing 4.0 g of anhydrous zinc acetate, adding it to 100 mL of anhydrous ethanol, and ultrasonically dispersing it at 40 kHz and 25° C. for 30 min to obtain a zinc salt solution;

[0090] The preparation method of the polyester powder coating comprises the following steps: drying polyester resin, curing agent, leveling agent, benzoin, brightener and functional filler, and then mixing them in a stirrer; melting, extruding, tabletting and crushing the mixed raw materials through a twin-screw extruder, wherein the temperature of the first zone of the extruder is 95° C., the temperature of the second zone is 120° C., the temperature of the third zone is 110° C., and the screw speed is 40 r / min; crushing the crushed flakes through a high-speed universal pulverizer, and then sieving through a 200-mesh sieve to obtain the polyester powder coating.

[0091] Example 2

[0092] A polyester powder coating, composed of the following components by weight: 1000 parts of carboxyl-terminated saturated polyester (SJ4868), 75 parts of curing agent TGIC, 10 parts of leveling agent PV88, 3 parts of benzoin, 3 parts of brightener 701B and 10 parts of functional filler TGO@ZnO;

[0093] Among them, the preparation method of TGO@ZnO and the preparation method of polyester powder coating are the same as those in Example 1.

[0094] Example 3

[0095] A polyester powder coating, composed of the following components by weight: 1000 parts of carboxyl-terminated saturated polyester (SJ4868), 75 parts of curing agent TGIC, 10 parts of leveling agent PV88, 3 parts of benzoin, 3 parts of brightener 701B and 20 parts of functional filler TGO@ZnO;

[0096] Among them, the preparation method of TGO@ZnO and the preparation method of polyester powder coating are the same as those in Example 1.

[0097] Comparative Example 1

[0098] A polyester powder coating, composed of the following components by weight: 1000 parts of carboxyl-terminated saturated polyester (SJ4868), 75 parts of curing agent TGIC, 10 parts of leveling agent PV88, 3 parts of benzoin, 3 parts of brightener 701B and 1 part of functional filler TGO@ZnO;

[0099] Among them, the preparation method of TGO@ZnO and the preparation method of polyester powder coating are the same as those in Example 1.

[0100] Comparative Example 2

[0101] A polyester powder coating, composed of the following components by weight: 1000 parts of carboxyl-terminated saturated polyester (SJ4868), 75 parts of curing agent TGIC, 10 parts of leveling agent PV88, 3 parts of benzoin, 3 parts of brightener 701B and 0 parts of functional filler TGO@ZnO;

[0102] The preparation method of the polyester powder coating is the same as that in Example 1.

[0103] Example 4

[0104] A polyester powder coating: The polyester powder coating prepared in Example 1 was prepared into a powder coating by electrostatic spraying and cured at 200° C. for 10 min.

[0105] Example 5

[0106] A polyester powder coating: The polyester powder coating prepared in Example 2 was prepared into a powder coating by an electrostatic spraying method, and cured at 200° C. for 10 minutes to obtain a polyester powder coating.

[0107] Example 6

[0108] A polyester powder coating: The polyester powder coating prepared in Example 3 was prepared into a powder coating by an electrostatic spraying method, and cured at 200° C. for 10 min to obtain a polyester powder coating.

[0109] Comparative Example 3

[0110] A polyester powder coating: The polyester powder coating prepared in Comparative Example 2 was prepared into a powder coating by an electrostatic spraying method, and cured at 200° C. for 10 minutes to obtain a polyester powder coating.

[0111] Comparative Example 4

[0112] A polyester powder coating: The polyester powder coating prepared in Comparative Example 1 was prepared into a powder coating by an electrostatic spraying method, and cured at 200° C. for 10 minutes to obtain a polyester powder coating.

[0113] Test Case

[0114] The polyester powder coatings prepared in Examples 4 to 6 and Comparative Examples 3 to 4 were tested respectively, and the test methods were as follows:

[0115] Impact resistance: tested in accordance with GB / T 1732-2020;

[0116] Hardness: Tested in accordance with GB / T 6739-2022;

[0117] Adhesion: According to GB / T 1733-1993 and GB / T 9286-2021, the adhesion and changes of the paint surface before and after boiling in water for 2 hours are tested;

[0118] Bending resistance: tested according to GB / T 6742-2007;

[0119] Acid and alkali corrosion resistance: According to GB / T 1733-1993 test, soak in 5.0% hydrochloric acid and sodium hydroxide solution at 25±5℃ for 72h, and observe whether the paint surface is normal;

[0120] Salt solution corrosion resistance: Place the coated painted surface plate in a 5.0% NaCl solution and immerse it at 40℃±1℃. Use electrochemical testing methods to measure the impedance change of the paint surface after immersion for 0d, 1d, 3d, and 7d, which further reflects the corrosion resistance of the paint surface in a neutral salt environment.

[0121] Electrochemical corrosion measurement: The CHI670E electrochemical workstation used in the test adopts a three-electrode system: the substrate of the test sample is used as the working electrode, and the coating surface is sealed with silicone to ensure that the effective exposed area of ​​each sample is 1cm 2 , silver-silver chloride as the reference electrode and platinum electrode as the auxiliary electrode. The following are the measurement parameter settings for the electrochemical experiment: the amplitude of the external sinusoidal wave perturbation is set to 10mV / s, the frequency scanning range of the electrochemical impedance is set to 10 -2 ~10 5 Hz. Each test sample was measured three times to ensure the accuracy of the test data.

[0122] The performance test results of the polyester powder coatings prepared in Examples 4 to 6 and Comparative Examples 3 to 4 are shown in Table 1:

[0123] Table 1 Performance test results of polyester powder coatings prepared in Examples 4 to 6 and Comparative Examples 3 to 4

[0124]

[0125] As can be seen from Table 1, the impact resistance and bending resistance of all formulation coatings are expressed as the optimal values ​​of the testable range, indicating that the basic mechanical properties of the polyester coating are excellent, and the addition of fillers does not lead to a decrease in the mechanical properties of the coating. For the hardness of the coating, the blank polyester coating is comparative example 3, and the hardness is HB. After adding TGO@ZnO functional filler, the hardness is HB, F, F and F when the addition amount is 1 part, 5 parts, 10 parts and 20 parts, respectively. As the addition amount increases, the hardness can be increased by one level, which can be attributed to the nanomaterial ZnO loaded on the surface of TGO. Its excellent hardness, accompanied by the uniform dispersion of TGO@ZnO material in the polyester coating, plays a role in improving. Then for the adhesion of the coating, the water boiling method and grid method commonly used in industry were used to characterize its performance. After water boiling and gridding, the adhesion level of Examples 4 to 6 with the addition of TGO@ZnO filler decreased less than that of Comparative Example 3, and the change amount decreased unidirectionally with the increase in the addition amount of TGO@ZnO filler. In Example 6, the adhesion level of the coating did not change before and after the test, indicating that the addition of TGO@ZnO filler effectively improved the adhesion of the polyester coating. This is mainly due to the uniform dispersion of TGO@ZnO in the polyester coating, and the interfacial bonding between the coating and the metal substrate is effectively enhanced due to the chemical bonds formed between the large number of active groups on the TP and GO surfaces and the metal, thus modifying the adhesion level of the coating on the metal substrate and enhancing the protective effect on the substrate.

[0126] The corrosion resistance test results of the polyester powder coatings prepared in Examples 4 to 6 and Comparative Examples 3 to 4 are shown in Table 2:

[0127] Table 2 Corrosion resistance of polyester powder coatings prepared in Examples 4 to 6 and Comparative Examples 3 to 4

[0128] project Acid corrosion Alkali corrosion Example 4 Paint surface is normal Abnormal paint Example 5 Paint surface is normal Paint surface is normal Example 6 Paint surface is normal Paint surface is normal Comparative Example 3 Abnormal paint Abnormal paint Comparative Example 4 Abnormal paint Abnormal paint

[0129] As can be seen from Table 2, whether it is the acid solution corrosion test or the alkali solution corrosion test, the paint surface of Comparative Example 3 without the functional filler TGO@ZnO showed abnormal conditions after immersion for 72 hours, which indirectly reflects the shortcomings of the polyester coating, and its strong acid and alkali resistance is weak. The addition of TGO@ZnO filler has effectively improved this situation to a great extent, especially when the filler addition amount reaches 10 parts or more, the acid and alkali corrosion resistance of the polyester paint surface has been effectively improved.

[0130] The anti-corrosion performance of the polyester powder coatings prepared in Examples 4 to 6 and Comparative Example 3 after being immersed in a 5.0% NaCl solution for different time periods was evaluated by electrochemistry. The bode impedance modulus of the polyester powder coating prepared in Comparative Example 3 is shown in FIG. Figure 2As shown; the bode impedance modulus of the polyester powder coating prepared in Examples 4 to 6 is shown Figures 3 to 5 As shown; the bode impedance modulus of the polyester powder coating prepared in Comparative Example 4 is shown in Figure 6 As shown; the anti-corrosion performance test results of the polyester powder coatings prepared in Examples 4 to 6 and Comparative Examples 3 to 4 were immersed in a 5.0% NaCl solution for 0h and 168h. Figure 7 As shown. Figures 2 to 6 It can be seen that in the Bode impedance diagram, the low frequency (Z f＝0.01Hz ) is usually used as a semi-quantitative parameter to evaluate the barrier properties of coatings. From the bode impedance diagram, it can be seen that the composite coating with TGO@ZnO composite material has an ultra-high low-frequency impedance modulus similar to that of pure polyester coating. Figure 7 It can be seen that as the immersion process progresses, the corrosive medium gradually invades the substrate, and the low-frequency impedance modulus of the coating gradually decreases, that is, the barrier performance of the coating weakens. When the coating is immersed in the sodium salt medium for 168 hours, the low-frequency impedance modulus of the pure polyester coating decreases to 2.61×10 6 Ω.cm 2 , indicating that the shielding effect of the coating is greatly reduced. Compared with the pure polyester coating, the composite coating with TGO@ZnO filler generally has a smaller decrease in low-frequency impedance modulus during the immersion process. Among them, the polyester coating with 20 parts of TGO@ZnO added has the least decrease in low-frequency impedance modulus. After immersion for 168 hours, the low-frequency impedance modulus of the coating remains at 8.63×10 8 Ω.cm 2 , and still has a strong shielding effect on the outside world.

[0131] The corrosion resistance of the polyester coating prepared by adding Examples 4 to 6 and Comparative Examples 3 to 4 was further studied by salt spray test. The test results are as follows: Figure 8 As shown. Figure 8It can be seen that after the 96h salt spray test, the pure polyester coating without TGO@ZnO showed large-area corrosion and coating adhesion failure near the cross scratch. After adding TGO@ZnO, the corrosion and adhesion failure of the coating were effectively improved, especially when the addition amount was 20 parts, the effect was the best. It shows that the addition of TGO@ZnO can also effectively improve the corrosion resistance of the coating in salt solution. These are mainly due to the excellent dispersibility of TGO@ZnO hybrid materials, which is different from GO, so that it is not easy to agglomerate in polyester coatings, so that the unique two-dimensional sheet structure of TGO@ZnO composite materials can be applied to the coating to better produce a maze effect, which can effectively improve the barrier performance of the coating; and the ZnO loaded on the TGO sheet can effectively fill the small gaps in the coating due to the small size effect, and also play a certain physical shielding role against the corrosive medium; in addition, the effective improvement of the adhesion of the coating by a large number of active groups on TP and GO is also an additional factor for improving the corrosion resistance of the coating. Under the synergistic effect of the three, the corrosion resistance of the coating is effectively improved.

[0132] The wear resistance of the polyester powder coating prepared in Example 6 and Comparative Example 3 was compared. The test results are as follows: Fig. 9 As shown. Fig. 9 In the figure, (a-b) are 3D scanning morphologies of the coating wear surface, and (c-d) are cross-sectional views of the coating wear. It can be seen from the 3D scanning morphology of the coating wear surface that the wear depth of the coating is ranked from deep to shallow as follows: polyester coating with 0 parts of filler added (Comparative Example 3) and polyester coating with 20 parts of filler (Example 6). The addition of TGO@ZnO functional filler can reduce the wear depth of the coating. Further calculation of the wear rates of the two coatings shows that the wear rates of the polyester coating with 0 parts of filler added and the polyester coating with 20 parts of filler added are 3.08×10 6 μm 3 / Nm and 2.13×10 5 μm 3 / Nm, the polyester coating with 20 parts of TGO@ZnO functional filler has the best friction resistance, which is consistent with the conclusion of the above friction depth. The reasons can be divided into the following points: (1) ZnO has excellent physical and chemical properties. When added to the coating as a filler, it can improve the hardness and wear resistance of the coating; (2) TGO@ZnO can be evenly distributed in the coating and play its role more effectively; (3) When ZnO is loaded on the TGO surface, due to the rich chemical functional groups on the surface of TGO@ZnO, it will be tightly combined with the polyester coating, so that when the coating is subjected to external friction, TGO and ZnO play a synergistic role, making the composite coating more tightly combined and more difficult to separate, thereby making the coating more wear-resistant.

[0133] It can be seen from the above results that the present invention can significantly improve the corrosion resistance and wear resistance of the polyester powder coating by using TGO@ZnO as a functional filler, thereby solving the problem that the coating formed by the existing polyester powder coating has poor corrosion resistance and wear resistance.

[0134] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A polyester powder coating, comprising the following components by weight: 1000 parts of polyester resin, 70-80 parts of curing agent, 7.5-12.5 parts of leveling agent, 2-5 parts of benzoin, 2-3 parts of brightener and 5-20 parts of functional filler; the functional filler is a polyphenol compound modified graphene oxide composite material loaded with nano zinc oxide.

2. The polyester powder coating according to claim 1, characterized in that: The preparation method of the functional filler comprises the following steps: (1) mixing a polyphenol compound, water and graphene oxide, and performing a reduction reaction to obtain polyphenol-modified graphene oxide; (2) mixing the polyphenol-modified graphene oxide obtained in step (1) with a solvent to obtain a polyphenol-modified graphene oxide suspension; (3) The polyphenol-modified graphene oxide suspension obtained in step (2) and the zinc salt solution are mixed to obtain a mixed solution, the pH value of the mixed solution is adjusted to 6.5-7.5, and then double decomposition and decomposition reactions are performed to obtain a polyphenol compound-modified graphene oxide composite material loaded with nano zinc oxide.

3. The polyester powder coating according to claim 2, characterized in that: The polyphenol compounds in step (1) include tea polyphenols and / or proanthocyanidins.

4. The polyester powder coating according to claim 2, characterized in that: In the step (1), the mass ratio of the polyphenol compound to graphene oxide is 2 to 8:

1.

5. The polyester powder coating according to claim 2, characterized in that: The temperature of the reduction reaction in step (1) is 68-72° C., and the time of the reduction reaction is 7-10 hours.

6. The polyester powder coating according to claim 2, characterized in that: In the step (3), the mass ratio of the zinc salt in the zinc salt solution to the polyphenol-modified graphene oxide in the polyphenol-modified graphene oxide suspension is 2 to 6:

1.

7. The polyester powder coating according to claim 2, characterized in that: The temperature of the double decomposition and decomposition reaction in the step (3) is 79-82° C., and the time of the double decomposition and decomposition reaction is 20-40 minutes.

8. The polyester powder coating according to claim 1, characterized in that: The curing agent includes TGIC or MT239.

9. The method for preparing the polyester powder coating according to any one of claims 1 to 8, comprising: The polyester resin, curing agent, leveling agent, benzoin, brightener and functional filler are mixed, melt-extruded, tableted, crushed and sieved in sequence to obtain a polyester powder coating.

10. A polyester powder coating, which is obtained by spraying and curing the polyester powder coating according to any one of claims 1 to 8 or the polyester powder prepared by the preparation method according to claim 9.

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