High-temperature-resistant anti-corrosion powder coating and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant anticorrosive powder coating and a preparation method thereof, and relates to the technical field of powder coatings, the high-temperature-resistant anticorrosive powder coating comprises the following components by mass: 20-30 parts of epoxy resin, 30-45 parts of modified polyester resin, 15-25 parts of a high-temperature-resistant filler, 8-15 parts of an anticorrosive filler, 3-8 parts of a curing agent, 0.5-2 parts of a leveling agent, 0.3-1 part of a degassing agent, and 1-3 parts of a coupling agent. The high-temperature-resistant filler is a composite filler composed of nano silicon dioxide and silicon carbide according to the mass ratio of 1: (2-3), and the anticorrosive filler is a compound filler composed of zinc phosphate and aluminum triphosphate according to the mass ratio of 1: (1-1.5). The powder coating disclosed by the invention can still keep good physical and mechanical properties in a high-temperature environment of 300-400 DEG C, the adhesive force reaches grade 1, the impact strength is greater than or equal to 50kgcm, the bending property is less than or equal to 2mm, the protection requirement of a metal component under a high-temperature working condition can be met, the problem that corrosion resistance and heat resistance of a traditional coating cannot be achieved at the same time under the high-temperature working condition is solved, and the powder coating has a wide market application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of powder coating, in particular to a high-temperature-resistant and corrosion-resistant powder coating and a preparation method thereof. BACKGROUND

[0002] As a solvent-free and environmentally friendly coating, powder coating has the advantages of uniform coating thickness, good decorative effect, high utilization rate, and low pollution, and has been widely used in the surface protection and decoration of metal components. With the continuous development of the industrial field, such as petroleum chemical industry, aerospace, automobile manufacturing, and power industry, many metal components need to work in high-temperature environments for a long time, and at the same time, they also face the erosion of corrosive media, which puts higher requirements on the high-temperature resistance and corrosion resistance of powder coating.

[0003] The existing powder coating mainly includes epoxy resin powder coating, polyester resin powder coating, and epoxy-polyester hybrid powder coating. Among them, the epoxy resin powder coating has excellent adhesion, chemical corrosion resistance, and mechanical properties, but the high-temperature resistance is poor, and it is usually used below 120℃, and the coating will discolor, crack, and fall off when the temperature exceeds 150℃. The high-temperature resistance of polyester resin powder coating is slightly better than that of epoxy resin powder coating, but its physical and mechanical properties and corrosion resistance will also decrease significantly at high temperatures above 200℃.

[0004] For example, a high-voltage insulation powder coating with the publication number CN112625540A includes various component raw materials in mass parts: epoxy resin 60-80 parts, quartz powder 20-30 parts, titanium dioxide 3-6 parts, natural camphor 1-5 parts, coupling agent 0.2-1.2 parts, nano filler 12-18 parts, solvent 30-45 parts, curing agent 0.4-0.8 parts, and additives 3.5-10 parts. The additives include leveling agent 1-3 parts, anti-settling agent 2-4 parts, dispersant 0.2-2 parts, preservative 0.1-0.5 parts, and defoamer 0.2-0.5 parts. Although the patent adds nano silicon nitride and nano magnesium hydroxide fillers, and the nano silicon nitride has certain high-temperature resistance (melting point about 1900℃), the base resin selected in the patent is epoxy resin (60-80 parts), and the resin is not heat-resistant modified. The shortcoming of the heat resistance of the epoxy resin itself has not been solved. At the same time, nano magnesium hydroxide will dehydrate at temperatures above 200℃, releasing water and causing volume shrinkage, which will lead to pores in the coating, not only failing to improve the heat resistance, but also damaging the coating density. The long-term use temperature of the coating described in the patent cannot break through 150℃, which cannot meet the protection requirements under medium-high temperature working conditions. Therefore, it is necessary to invent a high-temperature-resistant and corrosion-resistant powder coating and a preparation method thereof to solve the above problems. SUMMARY

[0005] The application aims to provide a high-temperature-resistant and anticorrosive powder coating and a preparation method thereof, so as to solve the problem of poor high-temperature-resistant and anticorrosive performance of powder coatings in the prior art.

[0006] To achieve the above-mentioned object, the application provides the following technical scheme: a high-temperature-resistant and anticorrosive powder coating, comprising the following components in parts by mass: 20-30 parts of epoxy resin, 30-45 parts of modified polyester resin, 15-25 parts of high-temperature-resistant filler, 8-15 parts of anticorrosive filler, 3-8 parts of curing agent, 0.5-2 parts of leveling agent, 0.3-1 part of degassing agent, and 1-3 parts of coupling agent, wherein the modified polyester resin is prepared by copolymerization of terephthalic acid, neopentyl glycol, dimethyl dichlorosilane and bisphenol A, the mass of dimethyl dichlorosilane accounts for 8-15% of the total mass of monomers, and the mass of bisphenol A accounts for 5-12% of the total mass of monomers, the high-temperature-resistant filler is a composite filler composed of nano-silicon dioxide and silicon carbide at a mass ratio of 1:2-3, and the anticorrosive filler is a compounded filler composed of zinc phosphate and aluminum tripolyphosphate at a mass ratio of 1:1-1.5.

[0007] Preferably, the epoxy resin is bisphenol A type epoxy resin with an epoxy value of 0.51-0.54 eq / 100 g.

[0008] Preferably, the curing agent is a phenolic amine curing agent or a latent curing agent, and the latent curing agent is a dicyandiamide curing agent with a particle size of 1-5 μm.

[0009] Preferably, the leveling agent is an acrylate leveling agent, the degassing agent is benzoin, and the coupling agent is γ-aminopropyl triethoxysilane or γ-glycidyl ether propyl trimethoxysilane.

[0010] Preferably, the application comprises the following steps: S1: pre-mixing: the epoxy resin, the modified polyester resin, the high-temperature-resistant filler, the anticorrosive filler, the curing agent, the leveling agent, the degassing agent and the coupling agent are weighed in parts by mass and added into a high-speed mixer, and then mixed at a rotation speed of 800-1200 r / min and a temperature of 40-60 ℃ for 15-30 min to obtain a pre-mixed material; S2: melt extrusion: the pre-mixed material is added into a double-screw extruder, and the temperature of each section of the extruder is controlled as follows: the temperature of the first section is 80-100 ℃, the temperature of the second section is 110-130 ℃, the temperature of the third section is 130-150 ℃, and the temperature of the fourth section is 120-140 ℃, and the rotation speed of the screw is 150-250 r / min, so that the extruded material strip is obtained after melt extrusion; S3: cooling and tabletting: the extruded material strip is immediately sent into a cooling water tank to cool to room temperature, and then tabletted into a thin sheet by a tablet press; S4: crushing and grinding: the flakes are sent into a crusher to be crushed into particles with a particle size of 5-10 mm, and then the particles are added into an air flow pulverizer to be ground under the conditions of a pulverizing pressure of 0.6-0.8 MPa and a classification wheel rotating speed of 2000-3000 r / min; S5: screening: the ground material is screened through a vibrating screen to screen out powder with a particle size of 30-80 μm, which is a high-temperature-resistant and corrosion-resistant powder coating.

[0011] Preferably, the stirring paddle of the high-speed mixer in step S1 is a paddle stirring paddle, and pulse stirring is adopted during stirring, that is, after stirring for 30 s, pausing for 10 s, and repeating until the mixing is completed.

[0012] Preferably, the length-diameter ratio of the screw of the double-screw extruder in step S2 is 25-30:1, and a wear-resistant coating is arranged on the inner wall of the barrel, the wear-resistant coating is a tungsten carbide coating, and the thickness of the tungsten carbide coating is 0.1-0.3 mm.

[0013] Preferably, the water temperature of the cooling water tank in step S3 is controlled to be 15-25℃, the water flow speed is 0.5-1 m / s, and the residence time of the material strip in the cooling water tank is 10-20 s.

[0014] Preferably, the pulverizing cavity of the air flow pulverizer in step S4 is made of stainless steel, and the inner wall is polished to have a surface roughness Ra≤0.8 μm.

[0015] Preferably, the screen of the vibrating screen in step S5 is a stainless steel woven screen with a mesh number of 200-500 meshes, and ultrasonic wave is used to assist the screening during the screening, the frequency of the ultrasonic wave is 20-40 kHz, and the amplitude is 5-10 μm.

[0016] In the above technical solution, the present application has the following technical effects and advantages: 1. The present application uses bisphenol A type epoxy resin and modified polyester resin as the matrix, and solves the performance short board of single resin through molecular structure design, wherein the modified polyester resin introduces dimethyl dichlorosilane (containing silicon-oxygen bond) and bisphenol A (containing aromatic ring), the bond energy of the silicon-oxygen bond is much higher than that of carbon-carbon bond, and the molecular chain thermal degradation can be inhibited at a high temperature of 300-400℃, the aromatic ring structure improves the rigidity of the resin, avoids the deformation of the coating at high temperature, and at the same time, the bisphenol A type epoxy resin with an epoxy value of 0.51-0.54 eq / 100 g and the modified polyester resin form an interpenetrating crosslinking network, which not only retains the high adhesion of the epoxy resin, but also makes the coating have a weight loss rate of less than 5% after aging at 400℃ for 1000 h, which is much better than the traditional epoxy powder coating (cracking occurs at 150℃); 2. The application discards the limitation of single filler, realizes performance superposition through two kinds of composite fillers, selects nano silicon dioxide and silicon carbide as high temperature resistant filler, the synergistic effect of the two can improve the high temperature resistance of the coating while ensuring the density and wear resistance of the coating, and zinc phosphate and aluminum tripolyphosphate are used as corrosion resistant fillers, which can form a double corrosion resistant barrier and significantly improve the corrosion resistance of the coating, and the salt spray resistance time is more than 1000h; 3. The powder coating of the application can still maintain good physical and mechanical properties in a high temperature environment of 300-400 DEG C, the adhesion reaches level 1, the impact strength is greater than or equal to 50kg cm, the bending performance is less than or equal to 2mm, which can meet the protection requirements of metal components under high temperature working conditions, solve the problem that traditional coatings cannot be both corrosion resistant and heat resistant under high temperature working conditions, and have wide market application prospects. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the specific embodiments of the application or the technical solutions in the prior art, the drawings needed in the specific embodiments or the prior art description will be briefly introduced below. Obviously, the drawings described below are some embodiments of the application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0018] Figure 1 The flowchart of the preparation method of the high temperature resistant and corrosion resistant powder coating of the application is shown. DETAILED DESCRIPTION

[0019] The technical solutions of the application will be described below in conjunction with the drawings, and obviously, the described embodiments are part of the embodiments of the application, not all the embodiments.

[0020] The components of the embodiments of the application described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the application provided in the drawings is not intended to limit the scope of the claimed application, but only represents selected embodiments of the application.

[0021] Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0022] The application provides a high temperature resistant and corrosion resistant powder coating, which comprises the following components: Figure 1The high-temperature-resistant and corrosion-resistant powder coating shown comprises the following components in parts by mass: 20-30 parts of epoxy resin, 30-45 parts of modified polyester resin, 15-25 parts of high-temperature-resistant filler, 8-15 parts of corrosion-resistant filler, 3-8 parts of curing agent, 0.5-2 parts of leveling agent, 0.3-1 part of degassing agent, and 1-3 parts of coupling agent. The modified polyester resin is prepared by copolymerization of terephthalic acid, neopentyl glycol, dimethyl dichlorosilane, and bisphenol A, wherein the mass of dimethyl dichlorosilane accounts for 8-15% of the total mass of monomers, and the mass of bisphenol A accounts for 5-12% of the total mass of monomers. The high-temperature-resistant filler is a composite filler composed of nano-silicon dioxide and silicon carbide at a mass ratio of 1:2-3. The corrosion-resistant filler is a compounded filler composed of zinc phosphate and aluminum tripolyphosphate at a mass ratio of 1:1-1.5.

[0023] The epoxy resin is bisphenol A type epoxy resin with an epoxy value of 0.51-0.54 eq / 100g. The curing agent is a phenolic amine curing agent or a latent curing agent, which is a dicyandiamide type curing agent with a particle size of 1-5 μm. The leveling agent is an acrylate leveling agent. The degassing agent is benzoin. The coupling agent is γ-aminopropyl triethoxysilane or γ-glycidyl ether oxypropyl trimethoxysilane.

[0024] The method comprises the following steps: Step one: premixing: take epoxy resin, modified polyester resin, high-temperature-resistant filler, corrosion-resistant filler, curing agent, leveling agent, degassing agent, and coupling agent in parts by mass, add them into a high-speed mixer, and mix them at a speed of 800-1200 r / min and a temperature of 40-60℃ for 15-30 min to obtain a premixed material; Step two: melt extrusion: add the premixed material into a double-screw extruder, control the temperature of each section of the extruder as follows: zone one temperature 80-100℃, zone two temperature 110-130℃, zone three temperature 130-150℃, and zone four temperature 120-140℃, and control the screw speed at 150-250 r / min. After melt extrusion, an extruded strip is obtained; Step three: cooling and tabletting: immediately send the extruded strip into a cooling water tank to cool it to room temperature, and then press it into a thin sheet through a tablet press; Step four: crushing and grinding: send the thin sheet into a crusher to crush it into particles with a particle size of 5-10 mm, and then add the particles into an airflow pulverizer to grind them under the conditions of a pulverizing pressure of 0.6-0.8 MPa and a classification wheel speed of 2000-3000 r / min; Step five: screening: screen the ground material through a vibrating screen to screen out powder with a particle size of 30-80 μm, which is the high-temperature-resistant and corrosion-resistant powder coating.

[0025] The stirring paddle of the high-speed mixer in step S1 is a paddle stirring paddle, and pulse stirring is adopted in the stirring process, that is, stirring for 30 s and pausing for 10 s, and the process is repeated until the mixing is completed; the length-diameter ratio of the screw of the twin-screw extruder in step S2 is 25-30:1, the inner wall of the barrel is provided with a wear-resistant coating, the wear-resistant coating is a tungsten carbide coating, and the thickness of the wear-resistant coating is 0.1-0.3 mm; the water temperature of the cooling water tank in step S3 is controlled to be 15-25 ℃, the water flow speed is 0.5-1 m / s, and the residence time of the material strip in the cooling water tank is 10-20 s; the crushing cavity of the jet mill in step S4 is made of stainless steel, the inner wall is polished, and the surface roughness Ra is ≤0.8 μm; and the screen of the vibrating screen in step S5 is a stainless steel woven screen with a mesh number of 200-500 meshes, and ultrasonic assisted screening is adopted in the screening process, the ultrasonic frequency is 20-40 kHz, and the amplitude is 5-10 μm.

[0026] Example One Raw material components (by mass fraction): bisphenol A type epoxy resin 25 parts, modified polyester resin (copolymerized from terephthalic acid, neopentyl glycol, dimethyl dichlorosilane and bisphenol A, dimethyl dichlorosilane accounting for 12% of the total mass of monomers, and bisphenol A accounting for 8% of the total mass of monomers) 38 parts, high-temperature-resistant filler (nanometer silicon dioxide and silicon carbide in a mass ratio of 1:2.5) 20 parts, corrosion-resistant filler (zinc phosphate and aluminum tripolyphosphate in a mass ratio of 1:1.2) 12 parts, phenolic amine curing agent 5 parts, acrylate leveling agent 1.2 parts, benzoin (degassing agent) 0.6 parts, and γ-aminopropyl triethoxysilane (coupling agent) 2 parts.

[0027] Preparation steps: Step one: premixing: all raw materials are weighed according to the above mass fraction, and are added to a high-speed mixer equipped with a paddle stirring paddle. The rotation speed is set to 1000 r / min, and the temperature is 50 ℃. Pulse stirring (stirring for 30 s and pausing for 10 s) is adopted, and the mixing is continuously performed for 22 min to obtain a premixed material; Step two: melt extrusion: the premixed material is added to a twin-screw extruder with a screw length-diameter ratio of 28:1 (the inner wall of the barrel is provided with a 0.2 mm thick tungsten carbide wear-resistant coating), and the temperature of each section is controlled to be 90 ℃, 120 ℃, 140 ℃, and 130 ℃, respectively. The rotation speed of the screw is 200 r / min, and the melt extrusion is performed to obtain an extruded strip; Step three: cooling and tabletting: the extruded strip is immediately sent to a cooling water tank (water temperature 20 ℃, water flow speed 0.8 m / s) for 15 s of residence time for cooling to room temperature, and then is pressed into a sheet by a tablet press; Step four: crushing and grinding: the sheet is sent to a crusher to be crushed into particles with a particle size of 8 mm, and then is added to a jet mill with a stainless steel crushing cavity (the inner wall is polished, and the surface roughness Ra is 0.6 μm) for grinding, and the grinding pressure is set to 0.7 MPa, and the rotation speed of the grading wheel is set to 2500 r / min. Step five: screening: after grinding, the material is screened through a 200-500 mesh stainless steel woven mesh vibrating screen, ultrasonic assisted screening is used with a frequency of 28 kHz and an amplitude of 8 μm, and powders with a particle size of 30-80 μm are screened out, thereby obtaining a high-temperature-resistant and corrosion-resistant powder coating.

[0028] In this embodiment, the core indicators such as high-temperature resistance (no cracking and discoloration at 200℃×1000h), salt spray resistance (scratch corrosion width ≤1.5mm), and adhesion (1 level) are all better than the industry standards, proving that the basic formula and process of the present application can stably produce powder coatings that meet the needs of general scenarios, and at the same time provide "baseline data" for the performance optimization direction (such as improving high-temperature resistance and strengthening corrosion resistance) of subsequent embodiments, facilitating intuitive comparison of the performance changes brought by differential adjustments.

[0029] Example two: Raw material components (by mass fraction): bisphenol A type epoxy resin 30 parts, modified polyester resin (prepared by copolymerization of terephthalic acid, neopentyl glycol, dimethyl dichlorosilane and bisphenol A, dimethyl dichlorosilane accounting for 15% of the total mass of monomers, bisphenol A accounting for 12% of the total mass of monomers) 45 parts, high-temperature-resistant filler (nanometer silicon dioxide and silicon carbide in a mass ratio of 1:3) 25 parts, corrosion-resistant filler (zinc phosphate and aluminum tripolyphosphate in a mass ratio of 1:1.5) 15 parts, dicyandiamide latent curing agent (particle size 3 μm) 8 parts, acrylate leveling agent 2 parts, benzoin (degassing agent) 1 part, γ-glycidyl ether oxypropyl trimethoxysilane (coupling agent) 3 parts.

[0030] Preparation steps: step one: premixing: the raw materials are weighed by mass fraction and added to a paddle type stirring paddle high-speed mixer, the speed is set to 1200 r / min and the temperature is set to 60℃, pulse stirring (stirring for 30 s and pausing for 10 s), and mixing for 30 min to obtain a premixed material; Step two: melt extrusion: the premixed material is added to a twin-screw extruder with a screw length-diameter ratio of 30:1 (0.3 mm thick tungsten carbide coating on the inner wall of the barrel), the temperature of each section is controlled as follows: zone one 100℃, zone two 130℃, zone three 150℃, zone four 140℃, the screw speed is 250 r / min, and an extruded strip is obtained; Step three: cooling and tabletting: the strip is sent to a cooling water tank (water temperature 25℃, water flow speed 1 m / s), stays for 20 s to cool to room temperature, and is tabletted into a sheet; Step four: crushing and grinding: the sheet is crushed into 10 mm particles and added to a stainless steel powdering chamber (Ra=0.5 μm) air jet pulverizer, the pulverizing pressure is 0.8 MPa and the grading wheel speed is 3000 r / min for grinding; Step five: sieving: sieving through 200-500 mesh stainless steel screen, 40 kHz frequency, 10 μm amplitude ultrasonic-assisted sieving, screening 30-80 μm powder, to obtain the product.

[0031] In this embodiment, the high temperature resistance is strengthened by three adjustments: first, the proportion of functional monomers in the modified polyester resin is increased (dimethyl dichlorosilane 15%, bisphenol A 12%, both are upper limit of the limited range), the silicon element and bisphenol A structure are used to improve the stability of the high temperature resistant skeleton of the resin; second, the amount of high temperature resistant filler is increased to 25 parts (upper limit of the limited range), and the ratio of nano silicon dioxide to silicon carbide is 1:3 (the high temperature resistance of silicon carbide is better than that of nano silicon dioxide); third, a high epoxy value epoxy resin (0.54 eq / 100g) is selected to enhance the crosslinking density with the curing agent and improve the high temperature stability of the coating.

[0032] Example three: Raw material components (by mass fraction): bisphenol A type epoxy resin 20 parts, modified polyester resin (prepared by copolymerization of terephthalic acid, neopentyl glycol, dimethyl dichlorosilane and bisphenol A, dimethyl dichlorosilane accounts for 8% of the total mass of monomers, bisphenol A accounts for 5% of the total mass of monomers) 30 parts, high temperature resistant filler (nano silicon dioxide and silicon carbide in a mass ratio of 1:2) 15 parts, corrosion resistant filler (zinc phosphate and aluminum tripolyphosphate in a mass ratio of 1:1) 8 parts, dicyandiamide latent curing agent (particle size 1 μm) 3 parts, acrylate leveling agent 0.5 parts, benzoin (degassing agent) 0.3 parts, γ-aminopropyl triethoxysilane (coupling agent) 1 part.

[0033] Preparation steps: step one: pre-mixing: weigh the raw materials and add them into a high-speed mixer (paddle type stirring paddle), rotate at 800 r / min, temperature 40℃, pulse type stirring and mixing for 15 min, to obtain the pre-mixed material; Step two: melt extrusion: add the material into a twin-screw extruder with a screw length-diameter ratio of 25:1 (0.1 mm thick tungsten carbide coating on the inner wall of the barrel), the temperature of each section is: zone one 80℃, zone two 110℃, zone three 130℃, zone four 120℃, the screw rotation speed is 150 r / min, and the extruded material is a strip; Step three: cooling and tabletting: the strip is sent into a cooling water tank (water temperature 15℃, water flow speed 0.5 m / s), stays for 10 s for cooling, and is tabletted into flakes; Step four: crushing and grinding: the flakes are crushed into 5 mm particles, and are added into a stainless steel powdering chamber (Ra=0.8 μm) air flow pulverizer, and are ground under a pulverizing pressure of 0.6 MPa and a grading wheel rotation speed of 2000 r / min; Step five: sieving: sieving through 200-500 mesh stainless steel screen, 20 kHz frequency, 5 μm amplitude ultrasonic-assisted sieving, screening 30-80 μm powder, to obtain the product.

[0034] In this embodiment, the formulation design is focused on "improving the efficiency of corrosion protection": first, optimize the ratio of corrosion protection fillers, use zinc phosphate and aluminum tripolyphosphate 1:1 low aluminum tripolyphosphate ratio (zinc phosphate passivation of metal substrate more direct, low proportion of aluminum tripolyphosphate can reduce the coating porosity), while controlling the total amount of filler at 8 parts (to avoid excessive filler leading to a decrease in coating density); second, select low particle size latent curing agent (1 μm, lower limit of the specified range), to ensure uniform distribution of the curing agent in the coating, reduce the blind area of curing, and improve the overall density of the coating; third, use low epoxy value epoxy resin (0.51 eq / 100g), to reduce the internal stress of the coating caused by too fast crosslinking density, and reduce the generation of microcracks.

[0035] Example Four: Raw material components (by mass fraction): bisphenol A type epoxy resin (epoxy value 0.53 eq / 100g) 28 parts, modified polyester resin (prepared from terephthalic acid, neopentyl glycol, dimethyl dichlorosilane, bisphenol A, dimethyl dichlorosilane accounting for 10% of the total monomer mass, bisphenol A accounting for 7% of the total monomer mass) 42 parts, high-temperature resistant filler (nano-silicon dioxide and silicon carbide in a mass ratio of 1:2.2) 22 parts, corrosion protection filler (zinc phosphate and aluminum tripolyphosphate in a mass ratio of 1:1.3) 10 parts, dicyandiamide latent curing agent (particle size 2 μm) 6 parts, acrylic ester leveling agent 1.5 parts, benzoin (degassing agent) 0.8 parts, γ-glycidyl ether oxypropyl trimethoxysilane (coupling agent) 2.5 parts.

[0036] Preparation steps: Step one: premixing: take all raw materials by mass fraction, add to a high-speed mixer equipped with a paddle stirrer. Set the speed to 1100 r / min and the temperature to 55°C. Use pulse stirring (stir for 30 s, then pause for 10 s). Continue mixing for 25 min to obtain the premixed material; Step two: melt extrusion: add the premixed material to a twin-screw extruder with a screw length-diameter ratio of 27:1 (the inner wall of the barrel is coated with a 0.25 mm thick tungsten carbide wear-resistant coating). Control the temperature of each section: zone one 95°C, zone two 125°C, zone three 145°C, zone four 135°C. The screw speed is 220 r / min. Melt extrusion produces an extruded strip; Step three: cooling and tabletting: immediately send the extruded strip to a cooling water tank (water temperature 22°C, water flow speed 0.7 m / s). Stay for 18 s to cool to room temperature. Then press into a sheet using a tablet press; Step four: crushing and grinding: send the sheet to a crusher to break it into 7 mm particles. Then add it to an air jet mill with a stainless steel grinding chamber (inner wall polished, surface roughness Ra=0.7 μm). Set the grinding pressure to 0.75 MPa and the classification wheel speed to 2800 r / min for grinding; Step five: screening: the ground material is screened through a 200-500 mesh stainless steel woven mesh vibrating screen, ultrasonic assisted screening is used with a frequency of 35 kHz and an amplitude of 7 μm, and a powder with a particle size of 30-80 μm is screened, that is, a high-temperature-resistant and corrosion-resistant powder coating is obtained.

[0037] In this embodiment, the parameters of each component are in the "intermediate to superior" range: the proportion of functional monomers in the modified polyester resin is 10% / 7% (between the conventional type and the high-temperature-resistant type), the high-temperature-resistant filler is 22 parts (the ratio is 1:2.2), and the corrosion-resistant filler is 10 parts (the ratio is 1:1.3), which not only avoids the high cost of the high-temperature-resistant formula, but also solves the problem of weak high-temperature resistance of the high-corrosion-resistant formula.

[0038] The raw material component summary table of each embodiment (unit: mass parts) is shown in the following table: The product performance test result table of each embodiment is shown as follows: In each embodiment, the ratio of epoxy resin and modified polyester resin is within the protection range of 20-30 parts and 30-45 parts, and the proportion of functional monomers (dimethyl dichlorosilane and bisphenol A) in the modified polyester resin meets the limit of 8-15% and 5-12%, ensuring the balance of high-temperature resistance and mechanical properties; the compounding ratio of high-temperature-resistant filler and corrosion-resistant filler is within the range required by the technical scheme, which can improve the corresponding performance.

[0039] It should be noted that, in this text, relational terms such as first and second are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment.

[0040] Although embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A high temperature resistant anticorrosive type powder paint, characterized by, The components include the following by mass fraction: 20-30 parts of epoxy resin, 30-45 parts of modified polyester resin, 15-25 parts of high-temperature-resistant filler, 8-15 parts of anticorrosive filler, 3-8 parts of curing agent, 0.5-2 parts of leveling agent, 0.3-1 part of degassing agent, and 1-3 parts of coupling agent, wherein the modified polyester resin is prepared by copolymerization of terephthalic acid, neopentyl glycol, dimethyl dichlorosilane, and bisphenol A, the mass fraction of dimethyl dichlorosilane in the total mass of monomers is 8-15%, and the mass fraction of bisphenol A in the total mass of monomers is 5-12%; the high-temperature-resistant filler is a composite filler composed of nano silicon dioxide and silicon carbide at a mass ratio of 1:2-3; and the anticorrosive filler is a compounded filler composed of zinc phosphate and aluminum tripolyphosphate at a mass ratio of 1:1-1.

5.

2. A high temperature resistant anticorrosive powder coating according to claim 1, characterized in that: The epoxy resin is bisphenol A type epoxy resin with an epoxy value of 0.51-0.54 eq / 100 g.

3. The high temperature resistant anticorrosive powder coating according to claim 1, characterized in that: The curing agent is a phenolic amine curing agent or a latent curing agent, and the latent curing agent is a dicyandiamide type curing agent with a particle size of 1-5 μm.

4. The high temperature resistant anticorrosive powder coating according to claim 1, characterized in that: The leveling agent is an acrylate leveling agent, the degassing agent is benzoin, and the coupling agent is γ-aminopropyl triethoxysilane or γ-glycidyl ether propyl trimethoxysilane.

5. A process for the preparation of a high temperature resistant anticorrosive powder coating according to any one of claims 1 to 4, characterized in that The method comprises the following steps: S1: premixing: the epoxy resin, modified polyester resin, high temperature resistant filler, anticorrosive filler, curing agent, leveling agent, degassing agent and coupling agent are weighed by mass fraction, added into a high-speed mixer, mixed at a speed of 800-1200r / min and a temperature of 40-60℃ for 15-30min to obtain a premixed material; S2: melt extrusion: the premixed material is added into a double screw extruder, the temperature of each section of the extruder is controlled as follows: the temperature of the first section is 80-100℃, the temperature of the second section is 110-130℃, the temperature of the third section is 130-150℃, and the temperature of the fourth section is 120-140℃, the screw rotation speed is 150-250r / min, and the extruded strip is obtained after melt extrusion; S3: cooling and tabletting: the extruded strip is immediately sent into a cooling water tank to cool to room temperature, and then pressed into a sheet by a tablet press; S4: crushing and grinding: the flakes are sent into a crusher to be crushed into particles with a particle size of 5-10 mm, and then the particles are added into an air flow pulverizer to be ground under the conditions of a pulverizing pressure of 0.6-0.8 MPa and a rotating speed of a classifying wheel of 2000-3000 r / min; S5: screening: screening the ground material through a vibrating screen to obtain powder with a particle size of 30-80 μm, i.e., a high-temperature-resistant and anticorrosive powder coating.

6. The method of claim 5, wherein: In the step S1, the stirring paddle of the high-speed mixer is a paddle stirring paddle, and pulse stirring is adopted during stirring, i.e., stirring for 30 s, pausing for 10 s, and repeating until the mixing is completed.

7. The method of claim 5, wherein: In the step S2, the length-diameter ratio of the screw of the double-screw extruder is 25-30:1, and the inner wall of the barrel is provided with a wear-resistant coating, which is a tungsten carbide coating with a thickness of 0.1-0.3 mm.

8. The method of claim 5, wherein: In the step S3, the water temperature of the cooling water tank is controlled at 15-25℃, the water flow speed is 0.5-1 m / s, and the residence time of the material strip in the cooling water tank is 10-20 s.

9. The method of claim 5, wherein: In the step S4, the crushing cavity of the jet mill is made of stainless steel and the inner wall is polished to have a surface roughness Ra≤0.8 μm.

10. The method of claim 5, wherein: In the step S5, the screen of the vibrating screen is a stainless steel woven mesh with a mesh number of 200-500, and ultrasonic wave assisted screening is adopted during screening, the ultrasonic wave frequency is 20-40 kHz, and the amplitude is 5-10 μm.

Images