Waterproof and anticorrosive insulating powder coating and preparation method thereof

Abstract

The application provides a waterproof and anticorrosive insulating powder coating and a preparation method thereof, and belongs to the technical field of powder coating preparation.The waterproof and anticorrosive insulating powder coating disclosed by the application is prepared from the following raw materials in parts by mass: modified epoxy resin 60-70 parts, phenolic curing agent 9-15 parts, ceramic microbead 8-15 parts, catalyst 1-5 parts, organic modified barium sulfate 6-12 parts and adhesion improver 1-5 parts; the modified epoxy resin is prepared by using epoxy resin as a matrix, modifying the epoxy resin by using carboxyl-terminated polyester resin first, and then introducing hydroxyl-terminated silicon propyl ester to react.The powder coating provided by the application has good adhesion to metal substrates, ceramic substrates, plastic substrates and other substrates, and has excellent mechanical strength, flexibility, corrosion resistance, weather resistance, insulation and water resistance; after being boiled in high-temperature water for a long time, the powder coating still has good adhesion, corrosion resistance and insulation, and can be applied to new energy fields such as outdoor electrical equipment and high-voltage systems.

Description

Technical Field

[0001] This invention belongs to the technical field of powder coating preparation, specifically relating to a waterproof, anti-corrosion, and insulating powder coating and its preparation method. Background Technology

[0002] Powder coatings are 100% solid, green powder coatings composed of resin, curing agent, pigments, and fillers through melt mixing. They conform to the contemporary environmental protection principles of "4E" (environmentally friendly, highly efficient, ecological, and economical) and are widely used as surface coatings for substrates in construction, industry, automotive, and home appliances. Currently, the most commonly used powder coatings (i.e., thermosetting powder coatings) on the market are: epoxy resin powder coatings, epoxy-polyester powder coatings, and polyester powder coatings. Epoxy resin powder coatings have excellent corrosion resistance, adhesion, water resistance, and insulation, producing a hard and dense film. However, their weather resistance is poor, they are not resistant to prolonged high-temperature boiling, and their flexibility is average. Epoxy-polyester powder coatings have lower costs and good leveling, adhesion, and corrosion resistance. However, their yellowing resistance, alkali resistance, and weather resistance are average, their boiling resistance is poor, and their insulation is average. Polyester powder coatings have excellent weather resistance, corrosion resistance, and decorative properties. However, different types of curing agents can cause some problems with the coating. Additionally, polyester powder coatings have average insulation and voltage resistance, and their boiling resistance is poor. However, thermoplastic powder coatings have a market share of less than 10% due to their relatively poor adhesion, difficult construction, and poor heat resistance, and are not commonly used powder coatings.

[0003] In the new energy field, the surface coatings for structural components made of metal, ceramic, or plastic substrates in outdoor electrical equipment, high-voltage systems, and other applications must not only meet the requirements for long-term weather resistance and corrosion prevention, but also ensure electrical insulation safety and stability under long-term humid and hot environments. However, the existing technologies for several commonly used thermosetting powder coatings (i.e., epoxy resin, epoxy-polyester, polyester, polyurethane, etc.) do not have ideal water resistance / insulation performance, water resistance / adhesion, and neutral salt spray performance. It is difficult to simultaneously achieve various comprehensive properties, and these properties pose safety hazards in the application scenarios of new energy products.

[0004] Invention patent CN201611252875.6 discloses a highly water-resistant mixed powder coating, which is a mixed powder coating of epoxy resin and polyester. The water-resistant agent introduced is a polymer compound containing cyano and ester functional groups, and the adhesion promoter is a polymer compound containing hydroxyl functional groups. It has good water resistance, weather resistance, insulation, and film-forming properties, as well as good mechanical properties and leveling properties. However, the water resistance time of this mixed powder coating is limited, with a maximum of only 40 hours, and the insulation, weather resistance, and corrosion resistance after high-temperature water boiling have not been studied, meaning the performance is yet to be determined.

[0005] Invention patent CN202311655316.X discloses a water-resistant waterborne acrylic resin and its water-resistant acrylic coating. The water-resistant waterborne acrylic resin includes ethylene glycol butyl ether, acrylate monomers, polyalkyl vinyl ethers, fluorinated acrylic monomers, initiators, molecular weight regulators, and silicon-containing double-bond monomers, giving the resin high heat resistance, cold resistance, corrosion resistance, electrical insulation properties, water resistance, and adhesion. The water-resistant acrylic coating includes the water-resistant waterborne acrylic resin, amino resin, N,N-dimethylethanolamine, propylene glycol methyl ether, defoamer, alcohol-soluble colorant, and water. However, this coating is water-based, contains solvents during use, is not environmentally friendly, and its insulation, adhesion, corrosion resistance, and abrasion resistance are generally poor. Furthermore, its water resistance only reaches a little over 300 minutes.

[0006] Invention patent CN202011312920.9 discloses an electrical insulating coating for power battery packs of new energy vehicles. It uses methyl phenyl polysiloxane resin as the main resin and amino silane coupling agent as the curing agent. By adding xylene, hydrophobic fumed silica, high molecular weight carbon black, etc., it has good adhesion, flexibility and is not easy to scratch. It has certain anti-corrosion properties and excellent resistance to damp heat. It also has excellent insulation and voltage resistance after high and low temperature impact. However, the polysiloxane resin coating has poor heat resistance, low hardness, and general chemical resistance. It is also relatively expensive. The water boiling resistance has not been studied.

[0007] Currently, for powder coatings operating in harsh electrical and outdoor environments, in addition to ensuring high adhesion under long-term high-temperature boiling conditions, they also need to guarantee superior comprehensive properties such as insulation, corrosion resistance, and weather resistance. However, there is limited research in this area by those skilled in the art, which is also the focus of this invention's research. Summary of the Invention

[0008] The purpose of this invention is to provide a waterproof, corrosion-resistant, and insulating powder coating and its preparation method. The sprayed paint film of this powder coating has good adhesion to substrates such as metal substrates, ceramic substrates, and plastic substrates, and has excellent mechanical strength, flexibility, corrosion resistance, weather resistance, insulation, and waterproofness. Moreover, after prolonged high-temperature boiling, it still has good adhesion, corrosion resistance, and insulation. It can be applied to outdoor electrical equipment, high-voltage systems, and other new energy fields.

[0009] To achieve the purpose of this invention, this invention provides a waterproof, anti-corrosion, and insulating powder coating, which is made from the following raw materials in parts by weight: 60-70 parts modified epoxy resin, 9-15 parts phenolic curing agent, 8-15 parts ceramic microspheres, 1-5 parts catalyst, 6-12 parts organically modified barium sulfate, and 1-5 parts adhesion promoter. The modified epoxy resin is prepared by first modifying the epoxy resin matrix with a carboxyl-terminated polyester resin, and then introducing a hydroxyl-terminated silicone propylene ester for reaction.

[0010] Furthermore, the preparation method of the modified epoxy resin includes the following steps: S1. Place the molten epoxy resin in a reactor, heat it to 80±5℃, add an appropriate amount of dipropylene glycol dimethyl ether, stir for 15-30 min, then add the molten carboxyl-terminated polyester resin and triphenylphosphine, introduce an inert gas, heat it to 110-140℃, stir and react for 3-5 h, when the epoxy value reaches 0.015-0.03 eq / 100g, stop the reaction to obtain the polyester-epoxy resin prepolymer; S2. Under an inert atmosphere, add an appropriate amount of solvent to a reactor at 70-80℃, then slowly add a well-mixed mixture of methyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, hydroxypropyl acrylate and γ-aminopropyltriethoxysilane reactants to the reactor, raise the temperature to 120-140℃, add an initiator and chain transfer agent, reflux for 3-5 hours, distill under reduced pressure, and dry under vacuum to obtain the hydroxyl-terminated silanyl propyl ester prepolymer; S3. Add hydroxyl-terminated silicone propylene ester prepolymer and organotin catalyst to the above molten polyester-epoxy resin prepolymer, introduce inert gas, heat to 120-140℃, stir and react for 1-2 hours, then heat to 150-180℃, stir and react for 1-2 hours, remove water and solvent after the reaction is completed to obtain modified epoxy resin.

[0011] Further, in step S1, the mass ratio of the carboxyl-terminated polyester resin to the epoxy resin is 100:(130-145). The amount of triphenylphosphine added is 0.6-1.0% of the mass of the epoxy resin; The carboxyl-terminated polyester resin has an acid value of 28-39 mgKOH / g, a Tg of 62-67℃, and a viscosity of 3300-5500 mPa.s. The epoxy resin is a bisphenol A type epoxy resin with an epoxy equivalent of 850-2000 g / eq.

[0012] Further, in step S2, the mass ratio of methyl methacrylate, butyl methacrylate, cyclohexyl methacrylate and hydroxypropyl acrylate is 16:8:1:2; The amount of γ-aminopropyltriethoxysilane added is 1.2-2.0% of the total mass of the acrylic monomers (i.e., the total mass of methyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, and hydroxypropyl acrylate). The amount of the initiator added is 2.0-2.5% of the total mass of the acrylic monomer; The amount of chain transfer agent added is 0.8-1.3% of the total mass of the acrylic monomer.

[0013] Further, in step S3, the mass ratio of the polyester-epoxy resin prepolymer to the hydroxyl-terminated silicone propylene prepolymer is (9-12):1; The amount of the organotin catalyst added is 0.12-0.18% of the total mass of the polyester-epoxy resin prepolymer and the hydroxyl-terminated silicone propylene ester prepolymer.

[0014] This invention uses modified epoxy resin as the main resin. First, epoxy resin and carboxyl-terminated polyester resin undergo a ring-opening addition esterification reaction under catalytic heating to obtain a polyester-epoxy prepolymer. Then, acrylate monomers and aminosiloxanes are used as raw materials to synthesize a hydroxyl-terminated silanyl propylene ester prepolymer. The hydroxyl-terminated silanyl propylene ester prepolymer is then introduced into the self-made polyester-epoxy prepolymer for modification reaction.

[0015] The epoxy value in the polyester-epoxy prepolymer needs to be controlled within the range of 0.015-0.03 eq / 100g, and the acid value should be maintained at 5-12 mgKOH / g. This not only provides precise active reaction sites for subsequent reactions and controls the molecular weight to prevent excessively high resin viscosity, but also improves the flexibility and crosslinking density of the modified epoxy resin. This, in turn, results in the powder coating of this invention exhibiting superior comprehensive properties such as water resistance, adhesion, corrosion resistance, and insulation. If the epoxy value is too low, the water resistance of the powder coating will decrease significantly, while also reducing its substrate adhesion, insulation, water resistance, corrosion resistance, and weather resistance. If the epoxy value is too high, the material's stability will be poor, and the reaction during curing may be too fast or excessive, affecting the leveling and appearance of the coating. Furthermore, the comprehensive properties of the coating, such as mechanical strength, adhesion, corrosion resistance, insulation, and water resistance, will all decrease significantly. If the acid value is too high, it will affect the subsequent reaction or curing, thereby affecting the coating's waterproofness, insulation, water resistance, and corrosion resistance. If the acid value is too low, it will lead to reaction inertness, weaken the interfacial bonding, make the coating less dense and have poor adhesion, and affect the coating's water resistance and long-term performance.

[0016] The introduction of hydroxyl silicone propylene ester prepolymer not only improves the flexibility, heat resistance, weather resistance, water resistance and interfacial compatibility of modified epoxy resin, but also ensures that modified epoxy resin has high strength and hardness, further improving the water resistance, weather resistance, corrosion resistance and insulation of the powder coating of the present invention.

[0017] This invention modifies epoxy resin with polyester and hydroxyl silicone propylene ester, which not only improves the flexibility and weather resistance of epoxy resin, but also enhances its resistance to damp heat, corrosion resistance, and insulation. The modified epoxy resin can improve the leveling properties of powder coatings, making the coating surface smooth, free of orange peel, and with high gloss. It also gives the powder coating higher hardness, flexibility, impact resistance, and abrasion resistance, and significantly improves the powder coating's resistance to boiling water, corrosion resistance, weather resistance, and adhesion.

[0018] Furthermore, the phenolic hydroxyl equivalent of the phenolic curing agent is 230-290 g / eq, and preferably, the phenolic curing agent is selected from KD407A or KD-410A of Guodu.

[0019] Furthermore, the ceramic microspheres are surface-modified with γ-aminopropyltriethoxysilane. Preferably, the amount of γ-aminopropyltriethoxysilane used is 0.8-1.6% of the mass of the ceramic microspheres. Modifying the ceramic microspheres with aminosiloxane not only improves their dispersibility in the powder coating and prevents agglomeration, but also improves the interfacial compatibility with other components in the powder coating, making the coating denser, smoother, and with uniform mechanical properties, and enhancing the adhesion of the coating; the introduction of long silane chains on the surface of the ceramic microspheres makes them oleophilic and hydrophobic, enhancing the coating's resistance to boiling water and ensuring the stability of the coating's insulation.

[0020] Furthermore, the catalyst is tetraphenylphosphine bromide or butyltriphenylphosphine bromide.

[0021] Further, the preparation method of the organically modified barium sulfate is as follows: Dry barium sulfate is dissolved in an ethanol solution, then γ-aminopropyltriethoxysilane is added, ultrasonicated for 15-30 min, the pH value is adjusted to 4.5, the temperature is raised to 70-80℃, and stirred for 2-5 h. After washing and filtration, silane-modified barium sulfate is obtained. Then, silane-modified barium sulfate is added to an appropriate amount of ethanol solution and mixed evenly, then polyvinylpyrrolidone solution is added and stirred evenly, then 3-glycidyl etheroxypropyltrimethoxysilane is added, ultrasonicated for 5 min, the temperature is raised to 50-60℃, stirred for 1-3 h, and spray-dried to obtain organically modified barium sulfate.

[0022] Furthermore, the amount of γ-aminopropyltriethoxysilane added is 0.6-1.2% of the mass of barium sulfate; The amount of polyvinylpyrrolidone used in the polyvinylpyrrolidone solution is 0.3-0.8% of the mass of barium sulfate; The mass ratio of the 3-glycidyl etheroxypropyltrimethoxysilane to the polyvinylpyrrolidone is 1:(4-6).

[0023] The organically modified barium sulfate of this invention is obtained by first surface modification of barium sulfate with aminosiloxane to obtain silane-modified barium sulfate, and then adding appropriate proportions of polyvinylpyrrolidone and 3-glycidyl etheroxypropyltrimethoxysilane for further modification. The use of this organically modified barium sulfate not only solves the problems of barium sulfate's easy agglomeration and water absorption, and improves the water resistance and interfacial compatibility of barium sulfate in powder coatings, but also gives the powder coating superior resistance to boiling water, corrosion resistance, wear resistance, and insulation, and appropriately improves the adhesion between the coating and the substrate.

[0024] Furthermore, the adhesion enhancer is selected from Partner's PTN107 or ChangFu. ® CAP32 (i.e., N-[5-(trimethoxysilylpropyl)-2-aza-1-oxopentyl]caprolactam).

[0025] Furthermore, the waterproof, anti-corrosion, and insulating powder coating of the present invention also includes any one or more additives selected from dispersants, leveling agents, stabilizers, defoamers, flame retardants, or pigments, which can be added according to the actual needs of the product.

[0026] This invention also provides a method for preparing a waterproof, corrosion-resistant, and insulating powder coating, specifically including the following steps: P1. Weigh the modified epoxy resin, phenolic curing agent, ceramic microspheres, catalyst, organic modified barium sulfate and adhesion promoter according to the mass fractions, and place them in a high-speed mixing pot for physical premixing to obtain mixture A; P2. Place mixture A in a twin-screw extruder for melt extrusion at an extrusion temperature of 100-120℃, then cool and crush to obtain mixture B; P3. Grind mixture B to obtain powder particles with a particle size D50=50±3μm, which is the waterproof, anti-corrosion and insulating powder coating.

[0027] The present invention has achieved the following beneficial effects: 1. The powder coating of this invention uses modified epoxy resin as the main resin, ensuring that the coating has excellent mechanical strength, hardness, flexibility, and adhesion. Even after 7 days of high-temperature boiling, it still maintains superior adhesion, corrosion resistance, electrical insulation, and weather resistance. The addition of ceramic microspheres allows for uniform dispersion in the powder coating and acts as a fulcrum, reinforcing, toughening, and hardening within the coating, thus enhancing the density of the powder coating film. The addition of organically modified barium sulfate provides the powder coating with flame-retardant properties. The paint film is not easily decomposed when heated, thus solving the problem of paint film aging caused by prolonged heating. This improves the overall performance of the paint film after high-temperature boiling, including insulation, mechanical strength, wear resistance, corrosion resistance, and flexibility. The addition of specific adhesion promoters, through their own surface activity, can significantly improve the adhesion of the paint film to metal, ceramic, and plastic substrates, enhance interlayer adhesion, flexibility, and corrosion resistance, and also improve adhesion after high-temperature boiling, ensuring that the paint film still has excellent overall performance of corrosion resistance, insulation, and weather resistance after high-temperature boiling.

[0028] 2. This invention is prepared using a conventional melt extrusion method, which is easy to operate, has low energy consumption, readily available raw materials, and low cost. It does not contain solvents or volatile toxic substances, and meets the requirements of the national environmental protection law.

[0029] 3. The powder coating film of the present invention is dense, smooth, and has high gloss, with good adhesion. It can be applied to the surface of different types of substrates such as metal, ceramics, and plastics, and has excellent mechanical strength, flexibility, wear resistance, corrosion resistance, weather resistance, water resistance, and electrical insulation.

[0030] 4. The powder coating of the present invention has excellent water resistance. After being boiled in high temperature water for more than 7 days, it still has good adhesion, weather resistance, wear resistance, corrosion resistance and insulation, thereby extending the durability of the coating and increasing the service life of outdoor workpieces. It can be applied to new energy fields such as outdoor electrical equipment and high voltage systems. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] The raw materials used in the embodiments of this invention represent only the samples used in the experiment and are not limited to the raw materials of this manufacturer. Raw materials of the same type and performance available on the market can also be used in the formulation of this application.

[0033] The ceramic microspheres used in the embodiments of this invention were all treated with γ-aminopropyltriethoxysilane (i.e., the ceramic microspheres in Examples 1-3). The specific treatment method is as follows: the dried ceramic microspheres were placed in a silane hydrolysate diluted 5 times with 30wt% ethanol solution (the mass ratio of γ-aminopropyltriethoxysilane: ethanol: water was 1:8:2), and stirred evenly. Then, acetic acid was added dropwise to adjust the pH value to 5, the temperature was raised to 70℃ and stirred for 6 hours, the temperature was further raised to 90℃ and stirred for 30 minutes, and then filtered to obtain the modified ceramic microsphere filter cake. The cake was then washed 3 times with ethanol and dried at 120℃ under vacuum for 5 hours to obtain silane-modified ceramic microspheres. The amount of γ-aminopropyltriethoxysilane used was 1.2% of the mass of the ceramic microspheres.

[0034] The ceramic microspheres have a particle size of 0.4-40 μm. In specific embodiments of the present invention, the ceramic microspheres are selected from 3M's ceramic microspheres W-410 and W-610 or from Greenia Nanomaterials' ceramic microspheres (the main components of which are silicon dioxide and aluminum oxide).

[0035] The waterproof, anti-corrosion, and insulating powder coating of the present invention and its preparation method are described below with reference to specific embodiments.

[0036] Example 1 The preparation method of the waterproof, anti-corrosion, and insulating powder coating in Example 1, by weight, is as follows: Weigh 60 parts of modified epoxy resin, 9 parts of phenolic curing agent KD-410A, 15 parts of ceramic microspheres (selected from Greenia Nanomaterials Co., Ltd.), 2.2 parts of tetraphenylphosphine bromide, 12 parts of organic modified barium sulfate, and 1.8 parts of adhesion promoter PTN107 and put them into a high-speed mixing pot for premixing to obtain mixture A. Then, pour mixture A into the hopper of a twin-screw extruder for melt extrusion at an extrusion temperature of 100-120℃, a screw speed (i.e., frequency) of 35Hz, and a feed rate (i.e., frequency) of 25Hz, so that the substances undergoing cross-linking reaction (epoxy, phenolic curing agent, etc.) are uniformly coated on the surface of other materials. Then, cool and crush to obtain a homogeneous mixture B. Then, grind mixture B to make powder particles with a particle size D50=50±3μm, which is a waterproof, anti-corrosion and insulating powder coating.

[0037] The specific preparation method of the above-mentioned modified epoxy resin is as follows: S1. Place 1.33 kg of molten epoxy resin (selected from Guodu YD-017) in a reactor. After heating the reactor to 80°C, add 220 g of dipropylene glycol dimethyl ether and stir for 30 min. Then add 1.0 kg of molten carboxyl-terminated polyester resin (selected from Guanghua Technology GH-2239) and 10.5 g of triphenylphosphine. Purge with nitrogen and heat to 130°C. Stir and react for 3-5 h. When the epoxy value reaches 0.018 eq / 100 g, stop the reaction to obtain the polyester-epoxy resin prepolymer. S2. Under a nitrogen atmosphere, 100g of xylene was added to a reactor at 80°C. Then, a mixture of 160g of methyl methacrylate, 80g of butyl methacrylate, 10g of cyclohexyl methacrylate, 20g of hydroxypropyl acrylate and 4g of γ-aminopropyltriethoxysilane reactants was slowly added to the reactor. The temperature was raised to 130°C, and then 6.2g of di-tert-butyl peroxide and 2.9g of dodecyl mercaptan were added. The mixture was refluxed for 4 hours, distilled under reduced pressure, and dried under vacuum at 140°C for 2 hours to obtain the hydroxyl-terminated propyl methacrylate prepolymer. S3. Add 100g of hydroxyl-terminated silicone propylene prepolymer and 1.6g of dibutyltin dilaurate to the above-mentioned molten 1kg polyester-epoxy resin prepolymer, purge with nitrogen, heat to 130℃, stir and react for 2h, then heat to 170℃, stir and react for 1.5h, remove water and solvent after the reaction is completed to obtain modified epoxy resin.

[0038] The above-mentioned method for preparing organically modified barium sulfate is as follows: 100g of dried barium sulfate (particle size 1250 mesh) is placed in 100mL of 20wt% ethanol solution, and 1.0g of γ-aminopropyltriethoxysilane is added. The mixture is sonicated for 20min, and acetic acid is added to adjust the pH value to 4.5. The temperature is raised to 80℃ and stirred for 4h. The mixture is washed with deionized water and filtered to obtain silane-modified barium sulfate. The silane-modified barium sulfate is added to 80mL of 20wt% ethanol solution and stirred evenly. Then, 25g of 2wt% polyvinylpyrrolidone solution (PVP K90) is added and mixed evenly. Then, 0.1g of 3-glycidyl etheroxypropyltrimethoxysilane is added, and the mixture is sonicated for 5min. The temperature is raised to 50℃ and stirred for 2h. The mixture is then spray-dried to obtain organically modified barium sulfate.

[0039] Example 2 The preparation method of the waterproof, anti-corrosion, and insulating powder coating in Example 2, based on parts by weight, is as follows: Weigh out 68 parts of modified epoxy resin, 12 parts of phenolic curing agent KD-407A, 8 parts of ceramic microspheres (select W-410), 3.5 parts of butyltriphenylphosphine bromide, 6 parts of organically modified barium sulfate, and 2.5 parts of adhesion promoter ChangFu. ®CAP32 is placed together in a high-speed mixing pot for premixing to obtain mixture A; then mixture A is poured into the hopper of a twin-screw extruder for melt extrusion at an extrusion temperature of 100-120℃, a screw speed (i.e., frequency) of 35Hz, and a feed rate (i.e., frequency) of 25Hz. After cooling and crushing, a homogeneous mixture B is obtained; then mixture B is ground to produce powder particles with a particle size D50=50±3μm, which is a waterproof, anti-corrosion and insulating powder coating.

[0040] The specific preparation method of the above-mentioned modified epoxy resin is as follows: S1. Place 1.42 kg of molten epoxy resin (KD-214C from Guodu) in a reactor. After heating the reactor to 80°C, add 250 g of dipropylene glycol dimethyl ether and stir for 30 min. Then add 1.0 kg of molten carboxyl-terminated polyester resin (GH-2239 from Guanghua Technology) and 10.5 g of triphenylphosphine. Purge with nitrogen and heat to 130°C. Stir and react for 3-5 h. When the epoxy value reaches 0.022 eq / 100 g, stop the reaction to obtain the polyester-epoxy resin prepolymer. S2. Under a nitrogen atmosphere, 100g of xylene was added to a reactor at 80°C. Then, a mixture of 160g of methyl methacrylate, 80g of butyl methacrylate, 10g of cyclohexyl methacrylate, 20g of hydroxypropyl acrylate and 4g of γ-aminopropyltriethoxysilane reactants was slowly added to the reactor. The temperature was raised to 130°C, and then 6.2g of di-tert-butyl peroxide and 2.9g of dodecyl mercaptan were added. The mixture was refluxed for 4 hours, distilled under reduced pressure, and dried under vacuum at 140°C for 2 hours to obtain the hydroxyl-terminated propyl methacrylate prepolymer. S3. Add 100g of hydroxyl-terminated silicone propylene ester prepolymer and 1.3g of dibutyltin dilaurate to the above-mentioned molten 0.9kg polyester-epoxy resin prepolymer, purge with nitrogen, heat to 130℃, stir and react for 2h, then heat to 170℃, stir and react for 1.5h, remove water and solvent after the reaction is completed to obtain modified epoxy resin.

[0041] The preparation method of the above-mentioned organically modified barium sulfate is the same as that in Example 1, and the specific steps are as described in Example 1.

[0042] Example 3 The preparation method of the waterproof, anti-corrosion, and insulating powder coating in Example 3, by weight, is as follows: Weigh 65 parts of modified epoxy resin, 12 parts of phenolic curing agent KD-410A, 10 parts of ceramic microspheres (W-610 selected), 3 parts of butyltriphenylphosphine bromide, 8 parts of organic modified barium sulfate, and 2 parts of adhesion promoter PTN107 and put them into a high-speed mixing pot for premixing to obtain mixture A; then pour mixture A into the hopper of a twin-screw extruder for melt extrusion at an extrusion temperature of 100-120℃, a screw speed (i.e., frequency) of 35Hz, and a feeding rate (i.e., frequency) of 25Hz. Then cool and crush to obtain a homogeneous mixture B; then grind mixture B to make powder particles with a particle size D50=50±3μm, which is a waterproof, anti-corrosion, and insulating powder coating.

[0043] The preparation method of the modified epoxy resin is the same as that in Example 1, and the specific steps are as described in Example 1.

[0044] The preparation method of the above-mentioned organically modified barium sulfate is the same as that in Example 1, and the specific steps are as described in Example 1.

[0045] Comparative Example 1 The powder coating composition and preparation method of this comparative example are the same as those of Example 3. The difference is that the modified epoxy resin in this comparative example 1 was not modified with hydroxyl-terminated silicone propylene ester. That is, the polyester-epoxy resin prepolymer was prepared by step S1 of the modified epoxy resin preparation method of Example 3, and then the solvent was removed.

[0046] Comparative Example 2 The powder coating of this comparative example has the same composition and preparation method as in Example 3. The difference is that in step S1 of the modified epoxy resin preparation method of this comparative example 2, the reaction termination condition of the epoxy resin and the carboxyl-terminated polyester resin is: when the epoxy value reaches 0.035 eq / 100g, the reaction is stopped to obtain the polyester-epoxy resin prepolymer; then, 0.9 kg of the obtained polyester-epoxy resin prepolymer is melted, and then 120 g of hydroxyl-terminated silicone propylene ester prepolymer and 1.4 g of dibutyltin dilaurate are added. Nitrogen gas is introduced, the temperature is raised to 130°C, and the reaction is stirred for 2 h. Then the temperature is raised to 170°C, and the reaction is stirred for 1.5 h. After the reaction is completed, water and solvent are removed to obtain the modified epoxy resin.

[0047] Comparative Example 3 The powder coating of this comparative example has the same composition and preparation method as that of Example 3. The difference is that in step S1 of the modified epoxy resin preparation method of this comparative example 3, the reaction termination condition of the epoxy resin and the carboxyl-terminated polyester resin is: when the epoxy value reaches 0.012 eq / 100g, the reaction is stopped to obtain the polyester-epoxy resin prepolymer; then, 0.9 kg of the obtained polyester-epoxy resin prepolymer is melted, and then 90 g of hydroxyl-terminated silicone propylene ester prepolymer and 1.2 g of dibutyltin dilaurate are added. Nitrogen gas is introduced, the temperature is raised to 130°C, and the reaction is stirred for 2 h. Then the temperature is raised to 170°C, and the reaction is stirred for 1.5 h. After the reaction is completed, water and solvent are removed to obtain the modified epoxy resin.

[0048] Comparative Example 4 The powder coating composition and preparation method of this comparative example are the same as those of Example 3. The difference is that ceramic microspheres were not added in this comparative example 4. Instead, hollow microspheres (2500 mesh hollow microspheres selected from orchids) were used instead. The hollow microspheres were also treated with γ-aminopropyltriethoxysilane, and the treatment method was the same as that in Example 3.

[0049] Comparative Example 5 The powder coating composition and preparation method of this comparative example are the same as those of Example 3. The difference is that the preparation method of the organic modified barium sulfate in this comparative example 5 is as follows: 100g of dried barium sulfate (particle size 1250 mesh) is placed in 100mL of 20wt% ethanol solution, and then 1.0g of γ-aminopropyltriethoxysilane is added. The mixture is sonicated for 20min, acetic acid is added to adjust the pH value to 4.5, the temperature is raised to 80℃, and the mixture is stirred for 4h. The mixture is then washed with deionized water and filtered to obtain silane modified barium sulfate (i.e., organic modified barium sulfate).

[0050] Comparative Example 6 The powder coating composition and preparation method of this comparative example are the same as those of Example 3. The difference is that the preparation method of the organic modified barium sulfate in this comparative example 6 is as follows: 100g of dried barium sulfate (particle size 1250 mesh) is placed in 100mL of 20wt% ethanol solution, and then 1.1g of γ-aminopropyltriethoxysilane is added. The mixture is sonicated for 20min, acetic acid is added to adjust the pH value to 4.5, the temperature is raised to 80℃, and the mixture is stirred for 4h. The mixture is washed with deionized water and filtered to obtain silane-modified barium sulfate. The silane-modified barium sulfate is added to 80mL of 20wt% ethanol solution and stirred evenly. Then, 25g of 2wt% polyvinylpyrrolidone solution (PVP K90) is added and mixed evenly. The mixture is sonicated for 5min, the temperature is raised to 50℃, and the mixture is stirred for 2h. The mixture is then spray-dried to obtain organic modified barium sulfate.

[0051] Comparative Example 7 The powder coating of this comparative example has the same composition and preparation method as in Example 3. The difference is that the adhesion promoter in this comparative example 7 is BYK-4511 from BYK Chemicals.

[0052] The powder coatings of Examples 1-3 and Comparative Examples 1-7 were used to prepare paint films (i.e., Application Examples 1-3 and Application Comparative Examples 1-7, respectively). The film preparation process was as follows: the powder coatings prepared above were uniformly sprayed onto a pretreated 1mm thick aluminum workpiece using an electrostatic device, and then placed in an oven and kept at 200℃ for 10 minutes. After removal, the workpiece was allowed to cool naturally to room temperature to obtain the paint film. The spraying process parameters were: atomization pressure 0.25MPa, electrostatic current 25µA, spraying voltage 80kV, and spraying distance 200mm.

[0053] The pretreatment process for the aluminum workpieces is as follows: after degreasing with acetone and removing rust with chemical solution, the aluminum workpieces are immersed in a silane coupling agent treatment solution for 20 minutes, then removed and dried at room temperature for 24 hours. The silane coupling agent treatment solution is a mixture of KH550, water, and ethanol in a mass ratio of 1:2:8, and the pH value is adjusted to 4.5 using acetic acid.

[0054] Application Example 4 The powder coating from Example 3 was sprayed onto a pretreated 1mm thick plastic workpiece (PBT workpiece) using an electrostatic spraying device. The workpiece was then placed in an oven and kept at 200℃ for 10 minutes. After removal, it was allowed to cool naturally to room temperature to obtain a paint film. The spraying process parameters were: atomization pressure 0.2MPa, electrostatic current 20µA, spraying voltage 70kV, and spraying distance 250mm.

[0055] The pretreatment process for PBT workpieces is as follows: The ABS workpiece is surface-cleaned, then chemically degreased, dried, de-energized, and dust-removed. Next, a silane coupling agent treatment solution is sprayed onto the surface of the ABS workpiece. It is then removed and dried at room temperature for 24 hours. The silane coupling agent treatment solution is a mixture of KH550, water, and ethanol in a mass ratio of 1:2:8, with the pH adjusted to 4.5 using acetic acid.

[0056] Application Example 5 The powder coating from Example 3 was sprayed onto a pretreated 1mm thick ceramic workpiece (alumina ceramic workpiece) using an electrostatic spraying device. The workpiece was then placed in an oven and kept at 200℃ for 10 minutes. After removal, it was allowed to cool naturally to room temperature to obtain a paint film. The spraying process parameters were: atomization pressure 0.25MPa, electrostatic current 25µA, spraying voltage 70kV, and spraying distance 200mm.

[0057] The pretreatment process for alumina ceramic workpieces is as follows: The alumina ceramic workpieces are ultrasonically cleaned to remove dust and oil, then roughened (light sandblasting). Next, a silane coupling agent treatment solution is sprayed onto the surface of the alumina ceramic workpieces. After removal, the workpieces are dried at room temperature for 24 hours. The silane coupling agent treatment solution is a mixture of KH550, water, and ethanol in a mass ratio of 1:2:8, with the pH adjusted to 4.5 using acetic acid.

[0058] The coatings obtained from Application Examples 1-5 and Comparative Application Examples 1-7 were subjected to performance tests. The coating thickness was 200±50µm. The coatings were tested for appearance, adhesion, impact resistance, electrical insulation, weather resistance, and water resistance. The test results are shown in Tables 1 and 2 below.

[0059] Adhesion test: The test was conducted according to GB / T 9286-1998 "Cross-cut test for paint and varnish films"; Impact resistance: Tested according to GB / T 1732-2020 "Test Method for Impact Resistance of Coating Films"; Corrosion resistance: Tested according to GB / T 1771-2007 "Determination of resistance to neutral salt spray of paints and varnishes". The coating sample was sprayed with salt spray for 15 minutes every 45 minutes in a salt spray test chamber at 40±2℃ and salt concentration (3.5%). After 24 hours of testing, the degree of damage to the appearance of the sample was observed and the grade was evaluated according to the provisions of GB / T 1740-2007.

[0060] Weather resistance: According to GB / T 14522-2008 testing standard, QUV-B artificial accelerated aging test (gloss retention rate 50%) / h; Electrical insulation: withstand voltage test, 3-hour withstand voltage test; Water resistance: The sample was boiled in water for 7 days (168 hours) and its adhesion, insulation (1 minute voltage resistance test) and corrosion resistance were tested.

[0061] Table 1 Performance test results of powder coating film under normal conditions As can be seen from the test results in Table 1, the powder coating film of the present invention is smooth, even, and free of pinholes, exhibiting excellent adhesion, impact resistance, electrical insulation, corrosion resistance, and weather resistance. Using the modified epoxy resin of the present invention as the matrix significantly improves the impact resistance, corrosion resistance, and weather resistance of the film, while also providing excellent adhesion and electrical insulation. The addition of ceramic microspheres enhances the impact resistance, adhesion, electrical insulation, and corrosion resistance of the present invention. Organic modification of barium sulfate can improve the impact resistance, adhesion, electrical insulation, and corrosion resistance of the film.

[0062] Table 2 Performance test results of powder coating film after high-temperature boiling in water As can be seen from the test results in Table 2, after being boiled in high-temperature water, the coating film of the powder coating of the present invention is smooth, even, and free of pinholes, and exhibits excellent adhesion, impact resistance, electrical insulation, corrosion resistance, and weather resistance. Using the modified epoxy resin of the present invention as the matrix significantly improves the water resistance of the coating film, maintaining its excellent adhesion, impact resistance, corrosion resistance, weather resistance, and electrical insulation. Organic modification of barium sulfate can improve the water resistance of the coating film, maintaining its excellent overall performance. The preferred adhesion promoter of the present invention can further improve the water resistance of the coating film.

[0063] It is worth noting that in the embodiments of the present invention, only one specific component of each component is selected for analysis. In fact, other components or types not mentioned in the present invention can also be selected.

[0064] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0065] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A waterproof, corrosion-resistant, and insulating powder coating, characterized in that, It is made from the following raw materials in parts by weight: 60-70 parts modified epoxy resin, 9-15 parts phenolic curing agent, 8-15 parts ceramic microspheres, 1-5 parts catalyst, 6-12 parts organic modified barium sulfate and 1-5 parts adhesion promoter. The modified epoxy resin is prepared by first modifying the epoxy resin matrix with a carboxyl-terminated polyester resin, and then introducing a hydroxyl-terminated silicone propylene ester for reaction.

2. The water and rot proof insulating powder paint according to claim 1, characterized in that, The preparation method of the modified epoxy resin includes the following steps: S1. Place the molten epoxy resin in a reactor, heat it to 80±5℃, add an appropriate amount of dipropylene glycol dimethyl ether, stir for 15-30 min, then add the molten carboxyl-terminated polyester resin and triphenylphosphine, introduce an inert gas, heat it to 110-140℃, stir and react for 3-5 h, when the epoxy value reaches 0.015-0.03 eq / 100g, stop the reaction to obtain the polyester-epoxy resin prepolymer; S2. Under an inert atmosphere, add an appropriate amount of solvent to a reactor at 70-80℃, then slowly add a well-mixed mixture of methyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, hydroxypropyl acrylate and γ-aminopropyltriethoxysilane reactants to the reactor, raise the temperature to 120-140℃, add an initiator and chain transfer agent, reflux for 3-5 hours, distill under reduced pressure, and dry under vacuum to obtain the hydroxyl-terminated silanyl propyl ester prepolymer; S3. Add hydroxyl-terminated silicone propylene ester prepolymer and organotin catalyst to the above molten polyester-epoxy resin prepolymer, introduce inert gas, heat to 120-140℃, stir and react for 1-2 hours, then heat to 150-180℃, stir and react for 1-2 hours, remove water and solvent after the reaction is completed to obtain modified epoxy resin.

3. The waterproof, anti-corrosion, and insulating powder coating according to claim 2, characterized in that, In step S1, the mass ratio of the carboxyl-terminated polyester resin to the epoxy resin is 100:(130-145). The amount of triphenylphosphine added is 0.6-1.0% of the mass of the epoxy resin; The carboxyl-terminated polyester resin has an acid value of 28-39 mgKOH / g, a Tg of 62-67℃, and a viscosity of 3300-5500 mPa.s. The epoxy resin is a bisphenol A type epoxy resin with an epoxy equivalent of 850-2000 g / eq.

4. The waterproof, anti-corrosion, and insulating powder coating according to claim 2, characterized in that, In step S2, the mass ratio of methyl methacrylate, butyl methacrylate, cyclohexyl methacrylate and hydroxypropyl acrylate is 16:8:1:

2. The amount of γ-aminopropyltriethoxysilane added is 1.2-2.0% of the total mass of the acrylic acid monomers; The amount of the initiator added is 2.0-2.5% of the total mass of the acrylic monomer; The amount of chain transfer agent added is 0.8-1.3% of the total mass of the acrylic monomer.

5. The waterproof, anti-corrosion, and insulating powder coating according to claim 2, characterized in that, In step S3, the mass ratio of the polyester-epoxy resin prepolymer to the hydroxyl-terminated silicone propylene prepolymer is (9-12):

1. The amount of the organotin catalyst added is 0.12-0.18% of the total mass of the polyester-epoxy resin prepolymer and the hydroxyl-terminated silicone propylene ester prepolymer.

6. The waterproof, anti-corrosion, and insulating powder coating according to claim 1, characterized in that, The ceramic microspheres were surface modified with γ-aminopropyltriethoxysilane.

7. The waterproof, anti-corrosion, and insulating powder coating according to claim 1, characterized in that, The method for preparing the organically modified barium sulfate is as follows: Dry barium sulfate is dissolved in an ethanol solution, then γ-aminopropyltriethoxysilane is added, the mixture is sonicated for 15-30 minutes, the pH is adjusted to 4.5, the temperature is raised to 70-80℃, and the mixture is stirred for 2-5 hours. After washing and filtration, silane-modified barium sulfate is obtained. Then, silane-modified barium sulfate is added to an appropriate amount of ethanol solution and mixed evenly. Polyvinylpyrrolidone solution is then added and stirred evenly. 3-glycidyl etheroxypropyltrimethoxysilane is then added, the mixture is sonicated for 5 minutes, the temperature is raised to 50-60℃, and the mixture is stirred for 1-3 hours. Finally, the mixture is spray-dried to obtain organically modified barium sulfate.

8. The waterproof, anti-corrosion, and insulating powder coating according to claim 7, characterized in that, The amount of γ-aminopropyltriethoxysilane added is 0.6-1.2% of the mass of barium sulfate; The amount of polyvinylpyrrolidone used in the polyvinylpyrrolidone solution is 0.3-0.8% of the mass of barium sulfate; The mass ratio of the 3-glycidyl etheroxypropyltrimethoxysilane to the polyvinylpyrrolidone is 1:(4-6).

9. The waterproof, anti-corrosion, and insulating powder coating according to claim 1, characterized in that, It also includes any one or more additives selected from dispersants, leveling agents, stabilizers, defoamers, flame retardants, or pigments.

10. A method for preparing a waterproof, corrosion-resistant, and insulating powder coating according to any one of claims 1-8, characterized in that, Specifically, the following steps are included: P1. Weigh the modified epoxy resin, phenolic curing agent, ceramic microspheres, catalyst, organic modified barium sulfate and adhesion promoter according to the mass fractions, and place them in a high-speed mixing pot for physical premixing to obtain mixture A; P2. Place mixture A in a twin-screw extruder for melt extrusion at an extrusion temperature of 100-120℃, then cool and crush to obtain mixture B; P3. Grind mixture B to obtain powder particles with a particle size D50=50±3μm, which is the waterproof, anti-corrosion and insulating powder coating.

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