A graphene-containing coating for transformers and its preparation method

Abstract

This invention discloses a graphene-containing coating for transformers and its preparation method. The coating comprises graphene oxide, a grafting agent, a leveling agent, a thickener, a defoamer, a solvent, a curing agent, and a modified epoxy resin. The invention first reacts the amino groups in the pigment with the epoxy groups of the epoxy resin to prepare a modified epoxy resin, then crosslinks the modified epoxy resin with graphene oxide; simultaneously, the phenolic hydroxyl groups of the grafting agent modify the graphene oxide; finally, other substances are added to prepare the coating. Compared with existing technologies, the coating prepared by this invention has the advantages of good corrosion resistance and good mechanical properties.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coatings, in particular to a graphene-containing coating for transformers and a preparation method thereof. BACKGROUND

[0002] Graphene is a two-dimensional material formed by a single layer of carbon atoms arranged in a hexagonal honeycomb structure. It has excellent electrical conductivity, thermal conductivity, strength, and flexibility. These unique properties make graphene have wide application potential in many fields, including coatings used in transformers.

[0003] In transformers, coatings are mainly used to improve insulation performance and heat dissipation performance, while also having certain mechanical strength and chemical resistance. Traditionally, transformer coatings mainly use materials such as epoxy resin and polyurethane, but these materials may have certain limitations in some aspects, such as insufficient thermal conductivity and insulation performance that needs to be improved. The introduction of graphene coatings can greatly improve these properties. The high thermal conductivity of graphene can improve the heat dissipation performance of the coating, thereby reducing the temperature of the transformer and improving its working efficiency and stability. At the same time, the high strength and flexibility of graphene also help to improve the mechanical properties of the coating and enhance the durability of the transformer.

[0004] CN109880488A discloses a diamine salicylaldehyde Schiff base modified graphene or graphene oxide metal anticorrosive coating, which comprises: epoxy resin 16-20 parts, pigment 1-2 parts, leveling agent 1-3 parts, zinc powder 13-23 parts, diamine salicylaldehyde Schiff base modified graphene or graphene oxide pre-dispersed slurry 1-9 parts, curing agent 3-20 parts. The invention utilizes the interaction between the modified graphene or graphene oxide surface functional groups and the polymer matrix molecules, forming effective interfacial bonding between them and achieving uniform dispersion in the matrix; at the same time, the modified graphene or graphene oxide is more easily combined with zinc powder through coordination bonds and more stably attached to the graphene network structure, reducing the amount of zinc powder used; the modified graphene or graphene oxide is more easily adsorbed on the metal surface, increasing the adhesion of the coating, and the amount of zinc powder used is less. However, the diamine salicylaldehyde Schiff base in the coating prepared by this method may be sensitive to ultraviolet light, and long-term exposure to sunlight may cause changes in its chemical structure, thereby reducing the performance of the coating.

[0005] CN116042039A discloses a graphene heat dissipation damping coating and a preparation method thereof, comprising: 20-50 parts of graphene modified water-based acrylic emulsion, 9-23 parts of modified graphene oxide, 20-38 parts of damping filler, 1-3 parts of film forming aid, 1-2 parts of functional aid, and 10-15 parts of deionized water. The graphene heat dissipation damping coating uses graphene modified water-based acrylic emulsion as the main film forming component, and cooperates with the synergistic effect of modified graphene oxide, thereby significantly improving the thermal conductivity coefficient and the complex loss factor, and significantly reducing the wear rate. However, the graphene coating prepared by the method has poor mechanical properties, and cracks or damage may occur after long-term use.

[0006] The transformer coating in the transformer station located on the seaside gradually appears damage and peeling phenomenon due to the corrosion of sea wind and seawater evaporation for a long time, which seriously affects the service life of the transformer. SUMMARY

[0007] In view of the above defects of the prior art, the technical problem to be solved by the present application is to improve the mechanical properties and corrosion resistance of the coating for transformers and prolong the service life of the coating.

[0008] To achieve the above-mentioned purpose, the present application provides a coating containing graphene for transformers, comprising the following components by weight: 0.1-2 parts of graphene oxide, 2-8 parts of a grafting agent, 0.1-3 parts of a leveling agent, 0.1-2 parts of a thickening agent, 0.1-2 parts of a defoaming agent, 10-150 parts of a solvent, 10-15 parts of a curing agent, and 80-120 parts of a modified epoxy resin prepared from a pigment and an epoxy resin.

[0009] Preferably, the preparation method of the modified epoxy resin comprises the following steps:

[0010] The pigment and the epoxy resin are added in anhydrous ethanol, a catalyst is added, and stirring is carried out at 200-350 rpm in an oil bath for 1-3 h. After stirring, the mixture is vacuum evaporated for 5-40 min to remove the solvent, and the modified epoxy resin is obtained.

[0011] More preferably, the preparation method of the modified epoxy resin comprises the following steps, in terms of weight parts:

[0012] 2-10 parts of the pigment and 6-30 parts of the epoxy resin are added in 10-40 parts of anhydrous ethanol, 0.01-1 parts of a catalyst is added, and stirring is carried out at 200-350 rpm in an oil bath for 1-3 h. After stirring, the mixture is vacuum evaporated for 5-40 min to remove the solvent, and the modified epoxy resin is obtained.

[0013] Preferably, the curing agent is any one of N-aminoethyl-3-aminopropyl methyl dimethoxy silane, diethylene triamine propyl trimethoxy silane, 3-aminopropyl triethoxy silane.

[0014] Preferably, the pigment is any one of pigment red 209, pigment red 122, 4, 11-dichloroquinacridone quinone.

[0015] Preferably, the grafting agent is any one of tea polyphenol, quercetin, lignin and 3, 5, 7-trihydroxy-2- (4- (trifluoromethyl) phenyl) -4H-chromen-4-one.

[0016] Preferably, the temperature of the oil bath is 80-100℃.

[0017] Preferably, the catalyst is dioctyltin dilaurate.

[0018] A preparation method of a graphene-containing paint for transformer, comprising the following steps, in parts by weight:

[0019] Step one, 80-120 parts of modified epoxy resin is added to 0.1-2 parts of graphene oxide, preheated at 60-80℃ for 10-15min to obtain a mixture;

[0020] Step two, 2-8 parts of grafting agent is added to 10-150 parts of solvent, ultrasonic dispersion for 20-40min; the mixture in step one and the grafting agent suspension are mixed at 70-90℃, 0.1-3 parts of leveling agent, 0.1-2 parts of thickening agent, 0.1-2 parts of defoaming agent are added, stirred at 200-300rpm, ultrasonic for 1-3h to obtain a mixture;

[0021] Step three, the mixture in step two is added to 10-15 parts of curing agent, stirred at 100-150rpm for 5-15min, vacuum degassing for 2-10min, to obtain the graphene-containing paint for transformer.

[0022] In this formula, the roles of each raw material are as follows:

[0023] Graphene oxide: as an important derivative of graphene, graphene oxide retains most of the excellent properties of graphene. Graphene oxide sheet contains a large number of hydroxyl, carboxyl, epoxy and other functional groups, resulting in excellent hydrophilicity. At the same time, these functional groups have good reactivity, so that graphene oxide and modified epoxy resin polymer molecules can form stable chemical bonds.

[0024] Grafting agent: The grafting agent contains phenolic hydroxyl functional groups. By reacting the phenolic hydroxyl groups on the grafting agent molecules with the carboxyl and epoxy groups on the graphene oxide layers, the purpose of grafting and modifying the graphene oxide is achieved. The steric hindrance of the rigid aromatic ring of the grafting agent molecule can effectively solve the problem of graphene oxide aggregation. In addition, the large number of phenolic hydroxyl groups and epoxy groups in the grafting agent can form good interfacial forces with the modified epoxy resin matrix, greatly improving the mechanical properties of the prepared coating.

[0025] Leveling agent: The leveling agent can effectively reduce the surface tension of the finishing liquid, improve the leveling and uniformity of the coating, and promote the formation of a flat, smooth, and uniform coating during the drying and film-forming process.

[0026] Thickening agent: The thickening agent can help the coating form a more stable system, improve the construction performance and coating effect of the coating.

[0027] Defoaming agent: The defoaming agent in the coating mainly plays the role of eliminating foam and suppressing bubbles, reducing the problems of uneven coating thickness and poor coating effect caused by excessive foam.

[0028] Epoxy resin: First, as a film-forming material, epoxy resin provides mechanical strength and toughness to the coating, allowing it to better adhere to the surface of the transformer and form a continuous and uniform protective layer. Second, epoxy resin has good insulating properties, effectively preventing the flow of electric charge and improving the insulating properties of the coating, thereby protecting the transformer from electric arcs and electrical leakage. In addition, epoxy resin also has good chemical resistance and weather resistance, which can resist various environmental factors such as moisture, ultraviolet light, chemicals, etc., prolonging the service life of the transformer. Finally, through modification, the adhesion, wear resistance, and corrosion resistance of epoxy resin are further improved, enhancing the protective effect of the coating on the transformer. The epoxy groups of epoxy resin can react with the amino functional groups contained in the pigment to prepare modified epoxy resin.

[0029] Curing agent: The curing agent plays a role in promoting the curing reaction of the coating. In addition to containing siloxane, the curing agent also contains amine functional groups, which can cross-link with the hydroxyl functional groups contained in the modified epoxy resin prepared, forming a three-dimensional network structure, thereby allowing the coating to cure into a hard coating.

[0030] Anhydrous ethanol: First, in the preparation process of modified epoxy resin, anhydrous ethanol acts as a solvent to help the pigment and epoxy resin mix uniformly and promote the ultrasonic dispersion of modified epoxy resin and graphene oxide, ensuring the uniformity and stability of the modified epoxy resin. Second, in the process of preparing the graphene-containing coating for transformers, anhydrous ethanol also acts as a solvent to help disperse the grafting agent and mix with the modified epoxy resin, forming a uniform mixture.

[0031] Pigment: the pigment is a quinacridone derivative, the amino functional group contained in the pigment can react with the hydroxyl functional group in the epoxy resin, so that the modified epoxy resin is prepared. Then bridged with graphene oxide, using the phosphorus flake crystal structure possessed by the pigment, the pigment can impart high dispersibility and flat morphology to graphene oxide, and the adverse effects of non-covalent adsorption and covalent bridging of the pigment after grafting modification with graphene oxide are avoided, in addition, the interface bonding between graphene oxide and epoxy resin is also improved, so that the corrosion resistance and mechanical properties of the prepared coating are further improved.

[0032] Dioctyltin dilaurate: it is a commonly used organotin catalyst, which has good catalytic effect and stability.

[0033] The beneficial effects of the present application are:

[0034] 1. Compared with the prior art, the amino functional group contained in the pigment reacts with the epoxy group in the epoxy resin to prepare a modified epoxy resin, which improves the interface bonding between graphene oxide and epoxy resin and improves the corrosion resistance, thermal stability and mechanical properties of the coating.

[0035] 2. Compared with the prior art, the phenolic hydroxyl functional group contained in the grafting agent reacts with the carboxyl and epoxy groups on the graphene oxide layer to form a bond, which modifies the graphene oxide. At the same time, the steric hindrance effect of the rigid aromatic ring of the grafting agent molecule can effectively alleviate the agglomeration problem of graphene oxide, so as to be more conducive to forming good interfacial force with the epoxy resin matrix, so that the mechanical properties of the coating are greatly improved. DETAILED DESCRIPTION

[0036] Parameters for using specific chemicals, sources.

[0037] 3,5,7-trihydroxy-2-(4-(trifluoromethyl)phenyl)-4H-chromen-4-one, CAS No.: 1254040-46-4.

[0038] 4,11-dichloroquinacridonequinone, CAS No.: 2389-75-5.

[0039] Graphene oxide, particle size: 35000 mesh, brand: 66333, Hebei Ruichuang Metal Material Co., Ltd.

[0040] Epoxy resin, model: SILIKOPON EF, Guangzhou Haoyi New Material Technology Co., Ltd.

[0041] Leveling agent, model number: RF-7613, Tianjin Ruikai Chemical Trade Co., Ltd.

[0042] Thickening agent, model number: QSC-935, Wuhan Runxingyuan Technology Co., Ltd.

[0043] Defoaming agent, model number: GP330, Nantong Lianli New Material Co., Ltd.

[0044] Example 1

[0045] A preparation method of a graphene-containing paint for a transformer, comprising the following steps:

[0046] Step one, 100g of modified epoxy resin is added to 0.5g of graphene oxide and heated at 80℃ for 15min to obtain a mixture;

[0047] Step two, 5g of 3,5,7-trihydroxy-2-(4-(trifluoromethyl)phenyl)-4H-chromen-4-one is added to 80mL of anhydrous ethanol, and ultrasonic treatment is performed at 400W for 35min to obtain a 3,5,7-trihydroxy-2-(4-(trifluoromethyl)phenyl)-4H-chromen-4-one suspension; then the mixture in step one is added to the 3,5,7-trihydroxy-2-(4-(trifluoromethyl)phenyl)-4H-chromen-4-one suspension at 72℃, and the two are mixed, 0.2g of RF-7613 leveling agent, 0.1g of QSC-935 thickening agent, and 0.1g of GP330 defoaming agent are added, and stirring is performed at 200rpm and ultrasonic treatment is performed at 400W for 3h to obtain a mixture;

[0048] Step three, the mixture in step two is added to 10g of 3-aminopropyltriethoxysilane and stirred at 150rpm for 15min, and then dried in a vacuum drying oven at 60℃ for 3min to obtain the graphene-containing paint for a transformer.

[0049] The preparation method of the modified epoxy resin comprises the following steps:

[0050] 3g of 4,11-dichloroquinacridone and 10g of epoxy resin are added to 20mL of anhydrous ethanol, 0.2g of dioctyltin dilaurate is added, stirring is performed at 200rpm in an 85℃ oil bath for 2h, and after the stirring is completed, the mixture is evaporated at 0.5KPa and 50℃ for 5min to remove the anhydrous ethanol, thereby obtaining the modified epoxy resin.

[0051] Example 2

[0052] The difference between the example 2 and the example 1 of the present application is that the 3,5,7-trihydroxy-2-(4-(trifluoromethyl)phenyl)-4H-chromen-4-one in the example 1 is replaced by tea polyphenol.

[0053] Example 3

[0054] Example 3 of the present application differs from Example 1 in that 3,5,7- trihydroxy-2-(4-(trifluoromethyl)phenyl)-4H-chromen-4-one in Example 1 is replaced by quercetin.

[0055] Example 4

[0056] Example 4 of the present application differs from Example 1 in that 3,5,7- trihydroxy-2-(4-(trifluoromethyl)phenyl)-4H-chromen-4-one in Example 1 is replaced by lignin.

[0057] Example 5

[0058] Example 5 of the present application differs from Example 1 in that 4,11- dichloroquinacridone quinone in Example 1 is replaced by Pigment Red 209.

[0059] Example 6

[0060] Example 6 of the present application differs from Example 1 in that 4,11- dichloroquinacridone quinone in Example 1 is replaced by Pigment Red 122.

[0061] Comparative Example 1

[0062] Comparative Example 1 of the present application differs from Example 1 in that 3,5,7-trihydroxy-2-(4-(trifluoromethyl)phenyl)-4H-chromen-4-one in Example 1 is replaced by tannic acid.

[0063] Comparative Example 2

[0064] Comparative Example 2 of the present application differs from Example 1 in that 4,11-dichloroquinacridone quinone in Example 1 is replaced by quinacridone.

[0065] Test Example 1

[0066] The coating wear resistance (reciprocating type), wear resistance (rotary type) were tested respectively according to the test standard of ASTM G99-05. Reciprocating wear: load 5N, counter electrode: ZrO2 ball, Φ=4.5mm, frequency 5Hz, single stroke 5mm, wear time 33min; rotary wear: load 5N, counter electrode: ZrO2 ball, Φ=4.5mm, rotary speed 300r / min, rotary radius 8mm, wear time 33min.

[0067] The cross-hatch experiment was carried out according to GB / T 9286-2021 "Color paint and varnish cross-hatch test". The tool spacing is 1mm, manual operation, soft hair brush to remove loose coating.

[0068] Pencil hardness test was carried out according to GB / T 6739-2022 "Paints and varnishes - Determination of film hardness by pencil test". The observation was carried out under natural sunlight at 25C, 50RH%.

[0069] Adhesion test was carried out according to GB / T 5210-2006 "Paints and varnishes - Pull-off test for adhesion". The adhesive was epoxy resin, and the curing was carried out at 25℃, 50RH% for 3h.

[0070] Impact resistance test was carried out according to GB / T 1732-2020 "Determination of impact resistance of paint films".

[0071] Uniformity test was carried out according to GB / T 4957-2003 "Non-magnetic base metals - Non-conducting coverings - Measurement of the thickness of coverings - Eddy current method".

[0072] The test results are shown in Table 1:

[0073] Table 1: Mechanical property test

[0074]

[0075]

[0076] Test Example 2

[0077] The samples prepared in Examples 1-6 and Comparative Examples 1-2 were subjected to neutral salt spray test according to GB / T 31588.1-2015 "Determination of resistance to cyclic corrosion environments of paints and varnishes - Part 1: Wet (salt spray) / dry / wet". The test results are shown in Table 2:

[0078] Table 2: Corrosion resistance test

[0079] Experimental group Salt mist resistance / h Example 1 1440h No blistering No rusting Example 2 720h No blistering No rusting Example 3 720h No blistering No rusting Example 4 720h No blistering No rusting Example 5 720h No blistering No rusting Example 6 720h No blistering No rusting Comparative Example 1 720h Blistering No rusting Comparative Example 2 720h Blistering No rusting

[0080] From the observation of the data in Table 1 and Table 2, it can be known that the mechanical property and corrosion resistance of the coating prepared in Example 1 is the best compared with Examples 1-6 and Comparative Examples 1-2.

[0081] Compared with the mechanical property test data of Examples 1-4 and Comparative Example 1, it is found that various data are different, and the reason for these data differences is that different grafting agents are used. The role of the grafting agent is to contain a phenolic hydroxyl functional group, which can modify the surface of graphene oxide. Through the reaction of the phenolic hydroxyl functional group with the carboxyl and epoxy groups of the graphene oxide layer, the purpose of grafting and modifying graphene oxide is achieved. At the same time, the grafting agent molecule itself has a rigid aromatic ring, and the steric hindrance effect of the rigid aromatic ring can effectively solve the agglomeration problem of graphene oxide, thereby improving the dispersibility of graphene oxide in the coating, and then affecting the corrosion resistance and mechanical properties of the coating. In addition to containing a phenolic hydroxyl functional group, 3,5,7-trihydroxy-2-(4-(trifluoromethyl)phenyl)-4H-chromen-4-one in Example 1 also contains a phenyl-CF3 bond, and the reaction of the phenyl-CF3 bond with the epoxy resin can increase the thermal stability and mechanical properties of the polymer. The possible reason is that -CF3 is a strong electron-attracting group, which has a strong electron-attracting induction effect and electron-attracting conjugation effect. This electronic effect can reduce the electron density on the benzene ring in the epoxy resin molecule, making it more difficult for the carbon atoms on the benzene ring to be oxidized, thereby improving the thermal stability of the epoxy resin. At the same time, fluorine is the most electronegative element in the periodic table, and its high electronegativity makes the trifluoromethyl group have very high chemical stability. Another possible reason is that the phenyl-CF3 has a large steric volume, which can hinder the close packing of molecular chains and reduce intermolecular forces, which helps to improve the heat resistance and mechanical properties of the epoxy resin. Therefore, the comprehensive performance of the coating prepared in Example 1 is better. At the same time, because the crosslinking density of the polymer is improved, on the other hand, because the graphene oxide and the epoxy resin have better dispersibility and strong binding force, the coating can fully exert its excellent shielding performance, and it is difficult for water molecules to penetrate along the interface between the graphene oxide and the epoxy resin, so the performance of the coating is optimized, and better corrosion resistance is exhibited.

[0082] Comparing Example 1, Examples 5-6 and Comparative Example 2, various data are found to be different, and the reason for these data differences can be that different pigments are used. The pigment is a quinacridone derivative. The amine group contained in the pigment can react with the epoxy group in the epoxy resin to participate, and then covalently or non-covalently connect with graphene oxide. The 4,11-dichloroquinacridonequinone in Example 1 introduces groups at positions 4 and 11 of quinacridone, which can weaken the hydrogen bonding of itself, thereby improving the dispersibility of the pigment in the paint, and the pigment is covalently connected with the epoxy resin, thereby also improving the compatibility between the pigment and the epoxy. In addition, the modified epoxy resin prepared is also connected with graphene oxide through covalent or non-covalent means, so the crosslinking between the pigment, the epoxy resin and the graphene oxide is more closely, which is convenient to improve the mechanical properties of the paint. For the same reason, because the crosslinking density of the polymer increases, the paint can fully exert its excellent shielding performance, and thus also shows better corrosion resistance.

Claims

1. A graphene-containing paint for a transformer, characterized by, The components include the following weight parts: 0.1-2 parts of graphene oxide, 2-8 parts of grafting agent, 0.1-3 parts of leveling agent, 0.1-2 parts of thickening agent, 0.1-2 parts of defoaming agent, 10-150 parts of solvent, 10-15 parts of curing agent, 80-120 parts of modified epoxy resin; The preparation method of the modified epoxy resin comprises the following steps, in weight parts: In 10-40 parts of anhydrous ethanol, 2-10 parts of pigments and 6-30 parts of epoxy resin are added, and then 0.01-1 parts of catalyst is added, and stirring is carried out in an oil bath at 200-350 rpm for 1-3 h; after stirring, the mixture is vacuum evaporated for 5-40 min to remove the solvent, and the modified epoxy resin is obtained; The pigments are any one of Pigment Red 209, Pigment Red 122, 4,11-dichloroquinacridone quinone; The grafting agent is any one of tea polyphenol, quercetin, lignin and 3,5,7-trihydroxy-2-(4-(trifluoromethyl)phenyl)-4H-chromen-4-one.

2. The graphene-containing paint for a transformer according to claim 1, characterized by, The curing agent is any one of N-aminoethyl-3-aminopropyl methyl dimethoxy silane, diethylene triamine propyl trimethoxy silane, 3-aminopropyl triethoxy silane.

3. The transformer paint containing graphene according to claim 1, wherein The temperature of the oil bath is 80-100℃.

4. The graphene-containing paint for a transformer according to claim 1, wherein The catalyst is dioctyltin dilaurate.

5. The graphene-containing paint for a transformer according to any one of claims 1 to 4, characterized by, The preparation method comprises the following steps, in weight parts: Step one, 80-120 parts of modified epoxy resin is added to 0.1-2 parts of graphene oxide, and preheating is carried out at 60-80℃ for 10-15 min to obtain a mixture; Step two, 2-8 parts of grafting agent is added to 10-150 parts of solvent, and ultrasonic dispersion is carried out for 20-40 min; the mixture in step one and the grafting agent suspension are mixed at 70-90℃, and 0.1-3 parts of leveling agent, 0.1-2 parts of thickening agent, 0.1-2 parts of defoaming agent are added, and stirring and ultrasonic treatment are carried out at 200-300 rpm for 1-3 h to obtain a mixed solution; Step three, the mixed solution in step two is added to 10-15 parts of curing agent, and stirring is carried out at 100-150 rpm for 5-15 min, and vacuum degassing is carried out for 2-10 min, and the graphene-containing coating for transformer is obtained.

6. The graphene-containing coating for transformer in the transformer according to any one of claims 1-5.

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