Powder coating as well as preparation method and application thereof

Abstract

The invention provides a powder coating as well as a preparation method and application thereof. The powder coating comprises the following components in parts by weight: 50-70 parts of polyester resin, 2-10 parts of functionalized silicon dioxide, 5-10 parts of a curing agent, 5-20 parts of titanium dioxide, 0.2-0.5 part of benzoin, 15-30 parts of barium sulfate and 0.2-0.5 part of a flatting agent, the functionalized silicon dioxide comprises silicon dioxide, polydopamine and a silane coupling agent, and the surface of the silicon dioxide is coated with the polydopamine and the silane coupling agent. The powder coating provided by the invention has the characteristics of high adhesive force and excellent aging resistance, boiling resistance and corrosion resistance.

Description

Technical Field

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

[0002] Industrialization has deepened the pollution of the environment. Pollutants such as sulfur dioxide, dust, acid and alkali, and organic pollutants have posed a great threat to the safety of power transmission and transformation equipment. Power transmission and transformation equipment is prone to corrosion in the atmospheric environment, and reasonable anti-corrosion measures are crucial to the life of power transmission and transformation equipment. Therefore, it is of great significance to study high-performance anti-corrosion measures.

[0003] At present, anti-corrosion technology is mainly concentrated in coating, cathodic protection and corrosion-resistant material technology. Traditional solvent-based anti-corrosion coatings have problems such as low adhesion, easy to fall off, short service life, and are not environmentally friendly. The VOC emissions of solvent-based anti-corrosion coatings are an important factor restricting their development. Therefore, there is an urgent need to develop new coatings with long service life and green environmental protection.

[0004] Powder coating is a solid powder coating that does not contain any organic solvent. It is usually applied by electrostatic spraying and has gradually developed in the fields of metal substrate coating, wood coating and other substrate coatings. CN103965744A discloses a household appliance powder coating with super-leveling properties and a production method thereof. The powder coating with super-leveling properties for household appliances contains the following components by mass: 1 to 33 parts of epoxy resin E-123, 30 to 32 parts of polyester resin, 1 to 3 parts of Huangshan leveling agent, 1 to 3 parts of brightener, 25 to 28 parts of titanium dioxide, 3 to 5 parts of barium sulfate, 1 to 3 parts of precipitant, 0.2 to 1 part of flow promoter, 0.1 to 0.5 parts of benzoin, 0.1 to 0.6 parts of antioxidant AT-626, 0.05 to 0.3 parts of EP-19 ultramarine, 0.001 to 0.005 parts of carbon black AS-52 and 0.1 to 0.3 parts of loosening agent. The household appliance powder coating with super leveling property provided by the technical solution can meet the protective properties such as water resistance and boiling water immersion resistance.

[0005] In the prior art, powder coatings are mostly made of nanomaterials mixed with resins, but nanomaterials are not easy to disperse in resins. During the manufacturing process, nanomaterials often aggregate into clumps, which affects the adhesion and corrosion resistance of the powder coating after film formation. This greatly shortens its service life and fails to provide good protection.

[0006] Therefore, it is necessary to develop a powder coating with high adhesion, long service life and excellent corrosion resistance. Summary of the invention

[0007] In view of the shortcomings of the prior art, the present invention aims to provide a powder coating and a preparation method and application thereof. The powder coating has the characteristics of good impact resistance, high adhesion, excellent aging resistance, water boiling resistance and corrosion resistance.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a powder coating, which comprises the following components in parts by weight: 50 to 70 parts (e.g., 52 parts, 54 parts, 56 parts, 58 parts, 60 parts, 62 parts, 64 parts, 66 parts, 68 parts, etc.) of polyester resin, 2 to 10 parts (e.g., 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts or 9 parts, etc.) of functionalized silica, 5 to 10 parts (e.g., 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 8.5 parts, 9 parts or 9.5 parts) of curing agent, 5 to 20 parts (e.g., 7 parts, 9.5 parts) of titanium dioxide. The present invention relates to a method for preparing the present invention wherein the present invention comprises: a first step of preparing the present invention and a second step of preparing the present invention; a second step of preparing the present invention and a third step of preparing the present invention; a first step of preparing the present invention and a second ...

[0010] In the present invention, the powder coating has the characteristics of good impact resistance, high adhesion, excellent aging resistance, water boiling resistance and corrosion resistance through the design of the powder coating components, wherein the functionalized silica comprises silica and polydopamine and a silane coupling agent coated on the surface of the silica, the polydopamine forms a π-π effect with the silica to realize non-covalent modification of the silica, and the silane coupling agent is assembled on the silica through the electrostatic effect of the polydopamine and the silane coupling agent to obtain the functionalized silica; the functionalized silica retains the characteristics of silica and has the functions of the polydopamine and the silane coupling agent, the silica has excellent aging resistance, the polydopamine has excellent adhesion performance, and can improve the corrosion resistance of the powder coating, and the silane coupling agent, as an intermediate medium, can improve the dispersibility and interface affinity of the functionalized silica in the powder coating, so that the functionalized silica can be evenly dispersed in the polyester resin. The powder coating has excellent performance and long service life. In addition, the powder coating is solvent-free and conforms to the concept of green environmental protection.

[0011] Preferably, the silane coupling agent comprises a vinyl silane coupling agent.

[0012] Preferably, the vinyl silane coupling agent includes vinyl tris(β-methoxyethoxy)silane.

[0013] Preferably, the functionalized silica is prepared by the following method:

[0014] (1) Silicon dioxide, an ethanol aqueous solution and an ammonia aqueous solution are mixed to obtain a premixed solution.

[0015] (2) The premixed solution obtained in step (1) and dopamine hydrochloride are mixed and reacted to obtain polydopamine-modified silica.

[0016] (3) Mixing the polydopamine-modified silica obtained in step (2), ethanol and a silane coupling agent to obtain the functionalized silica.

[0017] Preferably, the volume ratio of ethanol to water in the ethanol-water solution in step (1) is 6:(3.5-4.5), for example, 6:3.6, 6:3.7, 6:3.8, 6:3.9, 6:4, 6:4.1, 6:4.2, 6:4.3 or 6:4.4, etc.

[0018] Preferably, in the step (1), the total mass of silicon dioxide and ethanol aqueous solution is 100%, and the mass of silicon dioxide is 1% to 2%, for example, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8% or 1.9%, etc.

[0019] Preferably, in step (1), the total volume of the ethanol aqueous solution and the ammonia aqueous solution is 100%, and the volume of the ammonia aqueous solution is 2% to 5%, for example, 2.5%, 3%, 3.5%, 4% or 4.5%.

[0020] Preferably, the mass percentage concentration of the ammonia solution in step (1) is 20% to 30%, for example, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28% or 29%, etc.

[0021] Preferably, in step (2), the total mass of the premixed solution and dopamine hydrochloride is 100%, and the mass of the dopamine hydrochloride is 0.2% to 1%, for example, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8% or 0.9%.

[0022] Preferably, the reaction temperature in step (2) is 20-30°C (e.g., 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C or 29°C, etc.), and the reaction time is 16-24h (e.g., 17h, 18h, 19h, 20h, 21h, 22h or 23h, etc.).

[0023] Preferably, the reaction in step (2) is carried out under stirring, and the stirring speed is 400-700 rpm, such as 450 rpm, 500 rpm, 550 rpm, 600 rpm or 650 rpm.

[0024] Preferably, the mixing in step (2) further includes the steps of centrifugation, washing and freeze-drying.

[0025] Preferably, the mixing in step (3) specifically comprises ultrasonically dispersing the polydopamine-modified silica in ethanol, then adding a silane coupling agent for ultrasonic dispersion, and then stirring for 4 to 6 hours (e.g., 4.2 hours, 4.4 hours, 4.6 hours, 4.8 hours, 5.0 hours, 5.2 hours, 5.4 hours, 5.6 hours or 5.8 hours, etc.) at a temperature of 80 to 90°C (81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C or 89°C, etc.) and a rotation speed of 400 to 800 rpm (e.g., 450 rpm, 500 rpm, 550 rpm, 600 rpm, 650 rpm, 700 rpm or 750 rpm, etc.).

[0026] Preferably, the mixing in step (3) further includes the steps of centrifugation, washing and freeze-drying.

[0027] Preferably, in the step (3), the total mass of the silica modified with polydopamine, ethanol and the silane coupling agent is 100%, the mass of the silica modified with polydopamine is 0.2% to 1% (for example, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8% or 0.9%, etc.), and the mass of the silane coupling agent is 0.2% to 0.5% (for example, 0.25%, 0.3%, 0.35%, 4% or 0.45%, etc.).

[0028] Preferably, the polyester resin includes any one of polyethylene terephthalate, polybutylene terephthalate or polyarylate, or a combination of at least two of them.

[0029] Preferably, the curing agent includes any one of methyl ethyl ketone peroxide, cyclohexanone peroxide or benzoyl peroxide, or a combination of at least two thereof.

[0030] In a second aspect, the present invention provides a method for preparing the powder coating according to the first aspect, the preparation method comprising the following steps:

[0031] (I) mixing polyester resin, functionalized silica, curing agent, titanium dioxide, benzoin, barium sulfate and leveling agent, and melt-extruding to obtain composite polyester;

[0032] (II) The composite polyester prepared in step (I) is crushed and sieved to obtain the powder coating.

[0033] Preferably, the melt extrusion includes melt extrusion using a twin-screw extruder, the temperature of zone one of the twin-screw extruder is 80-95°C (for example, 82°C, 84°C, 86°C, 88°C, 90°C, 92°C or 94°C, etc.), and the temperature of zone two is 100-110°C (for example, 101°C, 102°C, 103°C, 104°C, 105°C, 106°C, 107°C, 108°C or 109°C, etc.).

[0034] Preferably, the mesh size of the sieve is 200-300 meshes, for example, 210 mesh, 220 mesh, 230 mesh, 240 mesh, 250 mesh, 260 mesh, 270 mesh, 280 mesh or 290 mesh.

[0035] In a third aspect, the present invention provides a use of the powder coating as described in the first aspect in anti-corrosion coating of power transmission and transformation equipment.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] In the present invention, the powder coating prepared by adding functionalized silica and compounding with polyester resin, curing agent, titanium dioxide, benzoin, barium sulfate and leveling agent has excellent aging resistance, boiling resistance, corrosion resistance, impact resistance and adhesion, greatly prolongs the service life of the powder coating, is solvent-free, and is green and environmentally friendly. DETAILED DESCRIPTION

[0038] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0039] Preparation Example 1

[0040] This preparation example provides a functionalized silica, specifically functionalized silica A, which is prepared by the following method:

[0041] (1) ultrasonically dispersing silicon dioxide in an ethanol aqueous solution (composed of ethanol and deionized water in a volume ratio of 6:4), with the total mass of silicon dioxide and the ethanol aqueous solution being 100% and the mass of the silicon dioxide being 2%, and then adding an ammonia aqueous solution (with a mass percentage concentration of the ammonia aqueous solution being 25%) and mixing, with the total volume of the ethanol aqueous solution and the ammonia aqueous solution being 100% and the volume of the ammonia aqueous solution being 2%, to obtain a premixed solution;

[0042] (2) adding dopamine hydrochloride to the premixed solution prepared in step (1), stirring and dissolving the mixture thoroughly, with the total mass of the premixed solution and dopamine hydrochloride being 100%, and the mass of the dopamine hydrochloride being 1%, stirring the mixture with magnetic force at medium speed (600 rpm) for 24 hours at room temperature (25° C.), centrifuging the mixture after the reaction, washing the mixture with ethanol and deionized water three times respectively, and freeze-drying the mixture to obtain polydopamine-modified silica;

[0043] (3) ultrasonically dispersing the polydopamine-modified silica obtained in step (2) in ethanol, and then adding vinyl tri(β-methoxyethoxy) silane for ultrasonic dispersion for 30 min, wherein the total mass of polydopamine-modified silica, ethanol and vinyl tri(β-methoxyethoxy) silane is 100%, the mass of the polydopamine-modified silica is 1%, and the mass of vinyl tri(β-methoxyethoxy) silane is 0.2%. The temperature is raised and magnetically stirred at 80° C. and 600 rpm for 6 h. After the reaction is completed, the mixture is centrifuged and washed three times with ethanol and deionized water respectively, and freeze-dried to obtain the functionalized silica A.

[0044] Preparation Example 2

[0045] This preparation example provides a functionalized silica, specifically functionalized silica B, which is prepared by the following method:

[0046] (1) ultrasonically dispersing silicon dioxide in an ethanol aqueous solution (composed of ethanol and deionized water in a volume ratio of 6:4), with the total mass of silicon dioxide and the ethanol aqueous solution being 100% and the mass of the silicon dioxide being 1.5%, and then adding an ammonia aqueous solution (the mass percentage concentration of the ammonia aqueous solution being 25%) and mixing, with the total volume of the ethanol aqueous solution and the ammonia aqueous solution being 100% and the volume of the ammonia aqueous solution being 2%, to obtain a premixed solution;

[0047] (2) adding dopamine hydrochloride to the premixed solution prepared in step (1), stirring and dissolving the mixture thoroughly, with the total mass of the premixed solution and dopamine hydrochloride being 100%, and the mass of the dopamine hydrochloride being 1%, stirring the mixture with magnetic force at medium speed (600 rpm) for 20 h at room temperature (25° C.), centrifuging the mixture after the reaction, washing it three times with ethanol and deionized water respectively, and freeze-drying the mixture to obtain polydopamine-modified silica;

[0048] (3) ultrasonically dispersing the polydopamine-modified silica obtained in step (2) in ethanol, and then adding vinyl tri(β-methoxyethoxy) silane for ultrasonic dispersion for 30 min, wherein the total mass of polydopamine-modified silica, ethanol and vinyl tri(β-methoxyethoxy) silane is 100%, the mass of the polydopamine-modified silica is 1%, and the mass of vinyl tri(β-methoxyethoxy) silane is 0.3%. The temperature is raised and magnetically stirred at 80° C. and 600 rpm for 6 h. After the reaction is completed, the mixture is centrifuged and washed three times with ethanol and deionized water respectively, and freeze-dried to obtain the functionalized silica B.

[0049] Preparation Example 3

[0050] This preparation example provides a functionalized silica, specifically functionalized silica C, which is prepared by the following method:

[0051] (1) ultrasonically dispersing silicon dioxide in an ethanol aqueous solution (composed of ethanol and deionized water in a volume ratio of 6:4), with the total mass of silicon dioxide and the ethanol aqueous solution being 100% and the mass of the silicon dioxide being 1%, and then adding an ammonia aqueous solution (with a mass percentage concentration of the ammonia aqueous solution being 25%) and mixing, with the total volume of the ethanol aqueous solution and the ammonia aqueous solution being 100% and the volume of the ammonia aqueous solution being 2%, to obtain a premixed solution;

[0052] (2) adding dopamine hydrochloride to the premixed solution prepared in step (1), stirring and dissolving the mixture thoroughly, with the total mass of the premixed solution and dopamine hydrochloride being 100%, and the mass of the dopamine hydrochloride being 1%, stirring the mixture with magnetic force at medium speed (600 rpm) for 16 h at room temperature (25° C.), centrifuging the mixture after the reaction, washing the mixture with ethanol and deionized water three times respectively, and freeze-drying the mixture to obtain polydopamine-modified silica;

[0053] (3) ultrasonically dispersing the polydopamine-modified silica obtained in step (2) in ethanol, and then adding vinyl tri(β-methoxyethoxy) silane for ultrasonic dispersion for 30 min, wherein the total mass of polydopamine-modified silica, ethanol and vinyl tri(β-methoxyethoxy) silane is 100%, the mass of the polydopamine-modified silica is 1%, and the mass of vinyl tri(β-methoxyethoxy) silane is 0.5%. The temperature is raised and magnetically stirred at 80° C. and 600 rpm for 6 h. After the reaction is completed, the mixture is centrifuged and washed three times with ethanol and deionized water respectively, and freeze-dried to obtain the functionalized silica C.

[0054] Preparation Example 4

[0055] This preparation example provides a functionalized silica, specifically functionalized silica D, which differs from Preparation Example 1 only in that the mass of dopamine hydrochloride in step (2) is adjusted to 0.5%, and other conditions are the same as those in Preparation Example 1.

[0056] Preparation Example 5

[0057] This preparation example provides a functionalized silica, specifically functionalized silica E, which differs from Preparation Example 1 only in that the mass of dopamine hydrochloride in step (2) is adjusted to 0.2%, and other conditions are the same as those in Preparation Example 1.

[0058] Preparation Example 6

[0059] This preparation example provides a polydopamine-modified silica, which differs from Preparation Example 1 only in that step (3) is not included, and other conditions are the same as those of Preparation Example 1.

[0060] Preparation Example 7

[0061] The present preparation example provides a silane coupling agent modified silica, which is prepared by the following method: ultrasonically dispersing silica in ethanol, then adding vinyl tri(β-methoxyethoxy) silane for ultrasonic dispersion for 30 minutes, with the total mass of silica, ethanol and vinyl tri(β-methoxyethoxy) silane being 100%, the mass of the silica being 1%, and the mass of the vinyl tri(β-methoxyethoxy) silane being 0.2%, heating, and magnetically stirring at 80° C. and 600 rpm for 6 hours. After the reaction is completed, centrifuging, washing with ethanol and deionized water three times respectively, and freeze-drying to obtain the silane coupling agent modified silica.

[0062] Example 1

[0063] This embodiment provides a powder coating and a preparation method thereof, wherein the powder coating includes the following components in parts by weight: 60 parts of a polyester resin (P6600, DSM Coatings Resins Company), 8 parts of functionalized silica (functionalized silica A provided in Preparation Example 1), 6 parts of a curing agent (methyl ethyl ketone peroxide), 10 parts of titanium dioxide, 0.5 parts of benzoin, 15 parts of barium sulfate, and 0.5 parts of a leveling agent (GLP503, Ningbo Nanhai Chemical Co., Ltd.).

[0064] The preparation method of the powder coating is as follows:

[0065] (I) a polyester resin, functionalized silica, titanium dioxide, barium sulfate, a curing agent, benzoin and a leveling agent are mixed, and then a composite polyester is extruded and pressed into a sheet shape by a twin-screw extruder melt extrusion method;

[0066] The temperature settings of the twin-screw extruder are: 90°C in zone I and 100°C in zone II.

[0067] (II) The sheet-shaped composite polyester obtained in step (I) is crushed in a crusher, and then sieved using a 200-mesh filter to obtain the powder coating.

[0068] Example 2

[0069] This embodiment provides a powder coating and a preparation method thereof, which differs from Example 1 only in that the powder coating comprises the following components in parts by weight: 65 parts of polyester resin (P6600, DSM Coatings Resins Company), 4 parts of functionalized silica (functionalized silica B provided in Preparation Example 2), 10 parts of curing agent (methyl ethyl ketone peroxide), 5 parts of titanium dioxide, 0.5 parts of benzoin, 15 parts of barium sulfate and 0.5 parts of leveling agent (GLP503, Ningbo Nanhai Chemical Co., Ltd.), and other conditions are the same as in Example 1.

[0070] Example 3

[0071] This embodiment provides a powder coating and a preparation method thereof, which differs from Example 1 only in that the powder coating comprises the following components in parts by weight: 70 parts of polyester resin (P6600, DSM Coating Resins Company), 10 parts of functionalized silica (functionalized silica C provided in Preparation Example 3), 8 parts of curing agent (methyl ethyl ketone peroxide), 20 parts of titanium dioxide, 0.2 parts of benzoin, 30 parts of barium sulfate and 0.5 parts of leveling agent (GLP503, Ningbo Nanhai Chemical Co., Ltd.), and other conditions are the same as in Example 1.

[0072] Example 4

[0073] This embodiment provides a powder coating and a preparation method thereof, which differs from Example 1 only in that the functionalized silica A provided in Preparation Example 1 is replaced with the functionalized silica D provided in Preparation Example 4 of the same mass, and other conditions are the same as in Example 1.

[0074] Example 5

[0075] This embodiment provides a powder coating and a preparation method thereof, which differs from Example 1 only in that the functionalized silica A provided in Preparation Example 1 is replaced with the functionalized silica E provided in Preparation Example 5 of the same mass, and other conditions are the same as in Example 1.

[0076] Comparative Example 1

[0077] This comparative example provides a powder coating and a preparation method thereof, which differs from Example 1 only in that the weight portion of the functionalized silica (functionalized silica A provided in Preparation Example 1) is adjusted to 1 part, and other conditions are the same as those in Example 1.

[0078] Comparative Example 2

[0079] This comparative example provides a powder coating and a preparation method thereof, which differs from Example 1 only in that the weight fraction of the functionalized silica (functionalized silica A provided in Preparation Example 1) is adjusted to 12 parts, and other conditions are the same as those in Example 1.

[0080] Comparative Example 3

[0081] This comparative example provides a powder coating and a preparation method thereof, which differs from Example 1 only in that no functionalized silica is added, titanium dioxide and barium sulfate are increased in proportion, a total of 8 parts by weight, and other conditions are the same as Example 1.

[0082] Comparative Example 4

[0083] This comparative example provides a powder coating and a preparation method thereof, which differs from Example 1 only in that the functionalized silica (functionalized silica A provided in Preparation Example 1) is replaced with silica of the same mass, and other conditions are the same as those in Example 1.

[0084] Comparative Example 5

[0085] This comparative example provides a powder coating and a preparation method thereof, which differs from Example 1 only in that the functionalized silica (functionalized silica A provided in Preparation Example 1) is replaced with the same mass of polydopamine-modified silica provided in Preparation Example 6, and other conditions are the same as in Example 1.

[0086] Comparative Example 6

[0087] This comparative example provides a powder coating and a preparation method thereof, which differs from Example 1 only in that the functionalized silica (functionalized silica A provided in Preparation Example 1) is replaced with silica modified with a silane coupling agent provided in Preparation Example 7 of the same mass, and other conditions are the same as in Example 1.

[0088] The powder coatings provided in the above Examples 1 to 5 and Comparative Examples 1 to 6 were electrostatically sprayed on Q235 steel sheets that had been sandblasted, and the paint film thickness was controlled to be 60 μm. The curing temperature was 200° C. and the curing time was 15 min to form a fully cured powder coating, and then the following performance tests were performed.

[0089] (1) Impact resistance: Tested in accordance with GB / T 1732-2020.

[0090] (2) Adhesion: Tested in accordance with GB / T 9286-1998.

[0091] (3) Salt spray resistance: Test according to GB / T 1771-2007 and observe whether the powder coating has abnormal phenomena such as blistering, shedding or discoloration after the test.

[0092] (4) Aging resistance: Test using a UV accelerated aging tester in accordance with GB / T 14522-2008 to observe whether the powder coating has abnormal phenomena such as blistering, shedding or discoloration after the test.

[0093] (5) Boiling water resistance: Test in accordance with GB / T 5237.4-2017 to observe whether the powder coating has abnormal phenomena such as blistering, shedding or discoloration after the test.

[0094] The test results are shown in Table 1 below.

[0095] Table 1

[0096] Impact resistance(cm) Adhesion Salt spray resistance Aging resistance Boiling resistance Example 1 60 Level 0 No abnormality No abnormality No abnormality Example 2 60 Level 0 No abnormality No abnormality No abnormality Example 3 60 Level 0 No abnormality No abnormality No abnormality Example 4 60 Level 0 No abnormality No abnormality No abnormality Example 5 60 Level 0 No abnormality No abnormality No abnormality Comparative Example 1 55 Level 1 Bubbling, discoloration Discoloration Bubbling, discoloration Comparative Example 2 60 Level 1 Foaming Discoloration Foaming Comparative Example 3 55 Level 1 Bubbling, discoloration Discoloration, partial peeling Foaming Comparative Example 4 55 Level 1 Bubbling, discoloration Discoloration, partial peeling Foaming Comparative Example 5 55 Level 1 No abnormality No abnormality No abnormality Comparative Example 6 60 Level 1 Foaming No abnormality Foaming

[0097] It can be seen from the contents of Table 1 that the powder coatings formed by curing the powder coatings provided in Examples 1-5 have excellent impact resistance, adhesion, corrosion resistance, aging resistance and water boiling resistance.

[0098] Compared with Example 1, if the weight fraction of functionalized silica in the powder coating is too low (Comparative Example 1), the impact resistance, adhesion, salt spray resistance, aging resistance and boiling water resistance of the powder coating formed by curing the powder coating are all reduced.

[0099] Compared with Example 1, if the weight percentage of functionalized silica in the powder coating is too high (Comparative Example 2), the functionalized silica is unevenly dispersed, resulting in performance degradation, and the adhesion, salt spray resistance, aging resistance and boiling water resistance of the powder coating formed by curing the powder coating are all reduced.

[0100] Compared with Example 1, if the powder coating does not contain functionalized silica (Comparative Example 3), the impact resistance, adhesion, salt spray resistance, aging resistance and boiling water resistance of the powder coating formed by curing the prepared powder coating are all reduced.

[0101] Compared with Example 1, if the functionalized silica is replaced with silica (Comparative Example 4), the impact resistance, adhesion, salt spray resistance, aging resistance and boiling water resistance of the powder coating formed by curing the prepared powder coating are all reduced.

[0102] Compared with Example 1, if the functionalized silica is replaced with polydopamine-modified silica (Comparative Example 5), the dispersibility of silica in the matrix will be affected, the dispersion effect will be worse, the mechanical properties of the powder coating formed by curing the prepared powder coating will deteriorate, and the impact resistance and adhesion will be reduced.

[0103] Compared with Example 1, if the functionalized silica is replaced with silica modified with a silane coupling agent (Comparative Example 6), the adhesion, salt spray resistance and water boiling resistance of the powder coating formed by curing the prepared powder coating are reduced.

[0104] The applicant declares that the present invention uses the above-mentioned embodiments to illustrate a powder coating and its preparation method and application, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A powder coating, characterized in that: The powder coating comprises the following components in parts by weight: 50-70 parts of polyester resin, 2-10 parts of functionalized silica, 5-10 parts of curing agent, 5-20 parts of titanium dioxide, 0.2-0.5 parts of benzoin, 15-30 parts of barium sulfate and 0.2-0.5 parts of leveling agent; the functionalized silica comprises silica and polydopamine and silane coupling agent coated on the surface of silica.

2. The powder coating according to claim 1, characterized in that The silane coupling agent includes a vinyl silane coupling agent; Preferably, the vinyl silane coupling agent includes vinyl tris(β-methoxyethoxy)silane.

3. The powder coating according to claim 1 or 2, characterized in that: The functionalized silica is prepared by the following method: (1) mixing silicon dioxide, an ethanol aqueous solution and an ammonia aqueous solution to obtain a premixed solution; (2) mixing the premixed solution obtained in step (1) and dopamine hydrochloride, and reacting them to obtain polydopamine-modified silica; (3) Mixing the polydopamine-modified silica obtained in step (2), ethanol and a silane coupling agent to obtain the functionalized silica.

4. The powder coating according to claim 3, characterized in that The volume ratio of ethanol to water in the ethanol aqueous solution of step (1) is 6:(3.5-4.5); Preferably, in step (1), the total mass of silicon dioxide and ethanol aqueous solution is 100%, and the mass of silicon dioxide is 1% to 2%; Preferably, in step (1), the total volume of the ethanol aqueous solution and the ammonia aqueous solution is 100%, and the volume of the ammonia aqueous solution is 2% to 5%; Preferably, the mass percentage concentration of the ammonia solution in step (1) is 20% to 30%.

5. The powder coating according to claim 3 or 4, characterized in that: In the step (2), the total mass of the premixed solution and dopamine hydrochloride is 100%, and the mass of the dopamine hydrochloride is 0.2% to 1%; Preferably, the reaction temperature in step (2) is 20 to 30° C., and the reaction time is 16 to 24 hours; Preferably, the reaction in step (2) is carried out under stirring, and the stirring speed is 400-700 rpm; Preferably, the mixing in step (2) further includes the steps of centrifugation, washing and freeze-drying.

6. The powder coating according to any one of claims 3 to 5, characterized in that: The mixing in step (3) specifically comprises ultrasonically dispersing the polydopamine-modified silica in ethanol, adding a silane coupling agent for ultrasonic dispersion, and then stirring for 4 to 6 hours at a temperature of 80 to 90° C. and a rotation speed of 400 to 800 rpm; Preferably, the mixing in step (3) further comprises the steps of centrifugation, washing and freeze-drying; Preferably, in step (3), the total mass of the silicon dioxide modified with polydopamine, ethanol and the silane coupling agent is 100%, the mass of the silicon dioxide modified with polydopamine is 0.2% to 1%, and the mass of the silane coupling agent is 0.2% to 0.5%.

7. The powder coating according to any one of claims 1 to 6, characterized in that: The curing agent includes any one of methyl ethyl ketone peroxide, cyclohexanone peroxide or benzoyl peroxide, or a combination of at least two thereof.

8. A method for preparing a powder coating according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: (I) mixing polyester resin, functionalized silica, curing agent, titanium dioxide, benzoin, barium sulfate and leveling agent, and melt-extruding to obtain composite polyester; (II) The composite polyester prepared in step (I) is crushed and sieved to obtain the powder coating.

9. The preparation method according to claim 8, characterized in that: The melt extrusion comprises melt extrusion using a twin-screw extruder, wherein the temperature of the first zone of the twin-screw extruder is 80-95° C., and the temperature of the second zone of the twin-screw extruder is 100-110° C.; Preferably, the mesh size of the sieve is 200-300 meshes.

10. Use of the powder coating according to any one of claims 1 to 7 in anti-corrosion coating of power transmission and transformation equipment.