A super weather-resistant powder coating for heavy machinery

Abstract

The present invention relates to the field of solid coatings, and in particular to a super-weather-resistant powder coating for heavy machinery. The raw materials include a modified super-weather-resistant polyester resin, triglycidyl isocyanurate, a modified titanium dioxide / shell powder composite material, and a nano-silicon dioxide-acrylate emulsion. The present invention prepares an organosilicon-modified acrylate by solution polymerization, introduces a modified acrylate prepolymer into a polyester molecule, and grafts the modified acrylate prepolymer onto the polyester molecular chain through the reaction of an epoxy group and a carboxyl group of the modified acrylate prepolymer. The main chain of the acrylate resin molecule does not contain an ester bond and a benzene ring, has strong light aging resistance, and significantly improves the weather resistance of the modified polyester. At the same time, the epoxy value of the modified acrylate prepolymer affects the branching degree of the modified polyester, thereby improving the impact resistance of the cured coating.

Description

Technical Field

[0001] This invention relates to the field of solid coatings, and more specifically to an ultra-weather-resistant powder coating for heavy machinery. Background Technology

[0002] Based on the high requirements for environmental friendliness, a solution was proposed to use ultra-weather-resistant powder coatings with 100% solid content and zero volatility to solve the protection and coating problems of heavy engineering machinery.

[0003] Currently, ultra-weather-resistant polyester powder coatings are widely used. However, polyester resin molecules contain a large number of ester bonds and benzene rings in their main chain, which are prone to main chain hydrolysis and photo-aging during polyester aging, thus limiting their weather resistance. Furthermore, existing ultra-weather-resistant polyester resins are mainly synthesized from weather-resistant monomers such as isophthalic acid. Due to the high rigidity of isophthalic acid, the paint film is very brittle, has poor impact resistance, and has a high curing temperature, which limits the application of the coating. Therefore, there is a need for an ultra-weather-resistant powder coating for heavy machinery to solve the above problems. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide an ultra-weather-resistant powder coating for heavy machinery.

[0005] S1: Synthesis of modified acrylate prepolymer

[0006] Butanone, acrylate monomer, organosilicon, n-dodecyl mercaptan and initiator AIBN are mixed and heated in a nitrogen atmosphere. The mixture is then cooled, neutralized, nitrogen is turned off, most of the solvent is evaporated by heating, vacuum is applied, and the mixture is discharged to obtain the modified acrylate prepolymer.

[0007] S2: Synthesis of Modified Ultra-Weather-Resistant Polyester Resin

[0008] Polyol, polyacid and monobutyltin oxide are mixed and heated in a nitrogen atmosphere. Modified acrylate prepolymer, triphenyl phosphite and acid hydrolysate are added in batches and heated to react. After vacuuming and cooling, triphenylethyl phosphorus bromide is added, stirred evenly, and discharged to obtain modified ultra-weather resistant polyester resin.

[0009] S3: Preparation of modified titanium dioxide / shell powder composite materials

[0010] Titanium oxysulfate solution and modified shell powder were mixed, pH was adjusted, reaction was carried out by water bath heating, and the mixture was allowed to stand. The precipitate was collected, filtered, washed, dried, ground, calcined, and cooled to obtain modified titanium dioxide / shell powder composite material.

[0011] S4: Preparation of Nano-Silica-Acrylic Emulsion

[0012] Mix 120-140 parts of n-hexadecane, 0.3-0.5 parts of azobisisobutyronitrile, 15-30 parts of methyl methacrylate and 15-30 parts of butyl acrylate, stir to dissolve, add 0.9-1.8 parts of nano silica, ultrasonically disperse for 10-15 min, add a deionized aqueous solution containing 1-3% sodium dodecyl sulfate by mass, ultrasonically emulsify for 5-10 min, cool in an ice-water bath to obtain a monomer fine emulsion, transfer to a reactor, purge with nitrogen gas for 10-15 min with stirring, react at 70-80℃ for 2-3 h to obtain a nano silica-acrylate emulsion;

[0013] S5: Preparation of Ultra-Weather-Resistant Powder Coatings

[0014] Modified ultra-weather-resistant polyester resin, triglycidyl isocyanurate, modified titanium dioxide / shell powder composite material, and nano-silica-acrylate emulsion are mixed and stirred, poured into a twin-screw extruder for melt extrusion, cooled, ground, and sieved to obtain ultra-weather-resistant powder coating.

[0015] Furthermore, the synthesis of the modified acrylate prepolymer in step S1 specifically includes the following steps:

[0016] S1.1: Add acrylic acid monomer, 20-25 parts of organosilicon and 0.5-0.7 parts of n-dodecyl mercaptan to the first storage bin, mix evenly to obtain mixed monomers, add 1-3 parts of initiator AIBN and 30-40 parts of butanone to the second storage bin to obtain a mixture;

[0017] S1.2: Add 10-20 parts of methyl ethyl ketone to the reactor. The gravity sensor detects that the gravity exceeds the set threshold and sends a signal to the controller to start the heating chamber and turn off the gravity sensor. The first temperature detector detects that the material temperature has reached the set threshold. The controller opens the stirring valve, nitrogen valve, first storage bin valve and second storage bin valve, and slowly adds the mixed monomer and mixture to carry out a constant temperature reaction.

[0018] S1.3: When the first timer reaches the set duration, the controller shuts off the heating chamber and allows it to cool naturally to room temperature. When the second temperature detector detects that the material temperature has dropped to the set threshold, the controller opens the neutralization valve and adds 1-3 parts of triethylamine to stir and neutralize the material. When the flow meter reaches the set threshold, the controller closes the neutralization valve and opens the short-time timer to perform neutralization and stirring. When the short-time timer reaches the set duration, the controller closes the nitrogen valve and starts the heating chamber to heat and evaporate most of the solvent. The vacuum pump is manually turned on to create a vacuum, and the material is discharged to obtain the modified acrylate prepolymer.

[0019] Furthermore, the synthesis of the modified ultra-weather-resistant polyester resin in step S2 specifically includes the following steps:

[0020] S2.1: Add the polyol and 0.03-0.06 parts of monobutyltin oxide into a 5-7L reactor, start stirring, introduce nitrogen gas, heat to 130-150℃, add the polyacid into the reactor, slowly raise the temperature to 240-260℃, set the column top temperature to 96-102℃, and react at a constant temperature for 4-5 hours;

[0021] S2.2: Control the acid value to 4-12 mg KOH / g, add modified acrylate prepolymer, and react at a constant temperature for 1-3 hours;

[0022] S2.3: Add 0.15-0.3 parts of triphenyl phosphite and acid hydrolysate, react at a constant temperature for 3-4 hours, control the acid value to 45-50 mgKOH / g, and apply vacuum at -0.095-(-0.0121) MPa until the resin acid value drops to 30-35 mgKOH / g, then release the vacuum.

[0023] S2.4: Cool to 200-210℃, add 0.15-0.3 parts of triphenylethyl phosphorus bromide, stir for 5-10 minutes, and discharge at 180-200℃ to obtain modified ultra-weather resistant polyester resin.

[0024] Furthermore, the preparation of the modified titanium dioxide and shell powder composite material in step S3 specifically includes the following steps:

[0025] S3.1: Wash the shells with deionized water, soak them in 0.15-0.25 mol / L sodium hydroxide solution for 1-2 hours, wash them with deionized water, dry them, crush them, and pass them through a 100-150 mesh sieve to obtain shell powder;

[0026] S3.2: Mix shell powder with distilled water and diethyl maleate, disperse by ultrasonic vibration for 10-15 min, add sodium stearate at 2-4% of the mass of shell powder, react at 70-90℃ for 2-3 h, filter with anhydrous ethanol, wash, dry, grind to obtain modified shell powder.

[0027] S3.3: Take 250-300 mL of 25-28 g / L titanium oxysulfate solution, add 25-30% of modified shell powder (by mass of titanium oxysulfate), add ammonia water under stirring in a water bath at 60-70℃, adjust the pH to neutral, stir in a constant temperature water bath for 30-50 min, let stand at room temperature for 2-3 h, take the precipitate, filter and wash, dry at 90-110℃ for 6-8 h, grind in a pulverizer for 5-10 min, calcine in a muffle furnace at 300-450℃ for 3-4 h, and cool naturally to obtain the modified titanium dioxide and shell powder composite material.

[0028] Furthermore, the preparation of the ultra-weather-resistant powder coating in step S5 specifically includes the following steps:

[0029] S5: Preparation of Ultra-Weather-Resistant Powder Coatings

[0030] S5.1: Add 300-320 parts of modified ultra-weather-resistant polyester resin, 22-25 parts of triglycidyl isocyanurate, 140-150 parts of modified titanium dioxide / shell powder composite material, 3-5 parts of nano-silica-acrylate emulsion, 1-3 parts of benzoin and 1-3 parts of brightening agent 701B into a mixing tank and stir at a speed of 400-500 r / min for 4-8 min;

[0031] S5.2: After mixing evenly, pour into a twin-screw extruder for melt extrusion. Set the heating conditions as follows: Zone I temperature 110-130℃, Zone II temperature 125-140℃.

[0032] S5.3: After extrusion and cooling to room temperature, the powder is fed into a grinding mill for grinding. The main mill speed is set to 8500-9500 r / min, the auxiliary mill speed is set to 6500-7500 r / min, and the sieve is set to 180-220 mesh. After extensive grinding and sieving, an ultra-weather-resistant powder coating is obtained.

[0033] Further, in step S1.1, the acrylate monomers are specifically 13-15 parts of methyl methacrylate, 4-6 parts of methyl methacrylate, 4-6 parts of n-butyl acrylate, 3-5 parts of n-butyl methacrylate and 4-6 parts of glycidyl methacrylate, and the organosilicon is vinyl-terminated polydimethylsiloxane.

[0034] Furthermore, the polyol in step S2.1 is specifically 38-43 parts neopentyl glycol and 0.7-1.2 parts trimethylolpropane, and the polyacid is 69-74 parts isophthalic acid.

[0035] Furthermore, the epoxy value of the modified acrylate prepolymer added in step S2.2 is 0.4-0.6 mol / kg, the amount of modified acrylate prepolymer added is 130-40% of the mass of the polybasic acid, and the acid hydrolysate added in step S2.3 is cyclohexanedicarboxylic acid.

[0036] The beneficial effects are:

[0037] 1. This invention prepares silicone-modified acrylates through solution polymerization, which reduces the viscous resistance between resin molecules, thereby reducing the viscosity of the acrylate prepolymer. The modified acrylate prepolymer is then introduced into the polyester molecule to prepare a modified ultra-weather-resistant polyester resin. The modified acrylate prepolymer is grafted into the polyester molecular chain through the reaction of epoxy groups and carboxyl groups. The main chain of the acrylate resin molecule does not contain ester bonds and benzene rings, and has strong resistance to photoaging, which significantly improves the weather resistance of the modified polyester. At the same time, the epoxy value of the modified acrylate prepolymer directly affects the branching degree of the modified polyester, which increases the crosslinking density of the cured coating, thereby improving the impact resistance of the coating.

[0038] 2. This invention prepares modified titanium dioxide / shell powder composite material by co-precipitation-calcination method, which can improve the light resistance of coating. Using waste shells as raw material, the porous characteristics of the shells are utilized to combine them with titanium dioxide. The prepared material has the characteristic of reflecting solar radiation, with more obvious effects in the visible and near-infrared bands, which is conducive to extending the service life of the coating and improving the utilization rate of natural resources.

[0039] 3. This invention uses a fine emulsion polymerization method to prepare nano-silica-acrylate emulsion. Nano-silica is uniformly dispersed in acrylate monomers by ultrasonic dispersion and mixed with water containing emulsifier. The emulsion prepared after ultrasonic emulsification is not prone to agglomeration and forms an encapsulated structure, thereby improving the leveling effect of powder coating.

[0040] 4. This invention uses a gravity sensor to automatically control the opening of the heating chamber, a first temperature detector to control the addition of reactants, a second temperature detector to add neutralizing agents, and a short-timer to adjust the heating temperature of the heating chamber, thereby reducing manual labor and improving the level of automation in production.

[0041] 5. This invention modifies shell powder by wet process using stearate. The carboxyl group of sodium stearate reacts with the calcium carbonate component in the shell powder to generate a precipitate that covers the surface of the shell powder, thereby improving its oleophilic properties and enhancing the dispersibility and flowability of the shell powder particles in coatings. Attached Figure Description

[0042] Figure 1 This is a flowchart of the ultra-weather-resistant powder coating for heavy machinery used in embodiments of the present invention.

[0043] Figure 2 The table shows the experimental results of artificial aging test and impact resistance test of powder coatings in Examples 1-3 and Comparative Example 1 of this invention.

[0044] Figure 3 The table shows the experimental results of the solar reflectance test of the powder coatings in Examples 1-3 and Comparative Example 2 of this invention. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0046] Example 1

[0047] An ultra-weather-resistant powder coating for heavy machinery, such as Figure 1As shown, the specific steps include:

[0048] S1: Synthesis of modified acrylate prepolymer

[0049] 13 parts of methyl methacrylate, 4 parts of methyl acrylate, 4 parts of n-butyl acrylate, 3 parts of n-butyl methacrylate, 4 parts of glycidyl methacrylate, 25 parts of vinyl-terminated polydimethylsiloxane sold by Wuhan Huaxiang Kejie Biotechnology Co., Ltd., and 0.5 parts of n-dodecyl mercaptan were added to the first storage bin and mixed evenly to obtain a mixed monomer. 1 part of initiator AIBN and 30 parts of butanone were added to the second storage bin to obtain a mixture.

[0050] Add 10 parts of methyl ethyl ketone to the reactor. The gravity sensor detects that the gravity exceeds the set threshold and sends a signal to the controller to start the heating chamber and turn off the gravity sensor. The temperature is raised to 80°C. The first temperature detector detects that the material temperature has reached the set threshold. The controller opens the stirring valve, nitrogen valve, first storage bin valve and second storage bin valve. The mixed monomer and mixture are slowly added simultaneously within 3 hours. The reaction is carried out at a constant temperature for 4 hours.

[0051] When the first timer reaches the set duration, the controller shuts off the heating chamber and allows it to cool naturally to room temperature. When the second temperature detector detects that the material temperature has dropped to the set threshold, the controller opens the neutralization valve, adds 1 part of triethylamine, and stirs to neutralize the material. When the flow meter reaches the set threshold, the controller closes the neutralization valve and opens the short-time timer, stirring for 1 hour. When the short-time timer reaches the set duration, the controller closes the nitrogen valve and starts the heating chamber to heat to 60°C, evaporating most of the solvent. The vacuum pump is then manually turned on to create a vacuum, which is maintained at -0.099 MPa for 3 hours. The material is then discharged, yielding the modified acrylate prepolymer.

[0052] S2: Synthesis of Modified Ultra-Weather-Resistant Polyester Resin

[0053] Add 38 parts of neopentyl glycol, 0.7 parts of trimethylolpropane and 0.03 parts of monobutyltin oxide to a 5L reactor, start stirring, introduce nitrogen gas, heat to 130°C, add 69 parts of isophthalic acid to the reactor, slowly raise the temperature to 240°C, set the column top temperature to 96°C, and react at a constant temperature for 4 hours.

[0054] The acid value was controlled at 4 mg KOH / g, and a modified acrylate prepolymer with an epoxy value of 0.4 mol / kg (30% of the mass of isophthalic acid) was added. The mixture was reacted at a constant temperature for 1 hour.

[0055] Add 0.15 parts of triphenyl phosphite and cyclohexanedicarboxylic acid, react at a constant temperature for 3 hours, control the acid value at 45 mg KOH / g, and then apply a vacuum at -0.095 MPa until the resin acid value drops to 30 mg KOH / g. Remove the vacuum.

[0056] Cool to 200℃, add 0.15 parts of triphenylethyl phosphorus bromide, stir for 5 minutes, and discharge at 180℃ to obtain modified ultra-weather resistant polyester resin;

[0057] S3: Preparation of modified titanium dioxide and shell powder composite materials

[0058] The shells were washed with deionized water, soaked in 0.15 mol / L sodium hydroxide solution for 1 hour, washed with deionized water, dried, crushed, and passed through a 100-mesh sieve to obtain shell powder.

[0059] Shell powder was mixed with distilled water and diethyl maleate, and ultrasonically dispersed for 10 min. Sodium stearate of 2% by weight of shell powder was added, and the mixture was reacted at 70℃ for 3 h. The mixture was then filtered with anhydrous ethanol, washed, dried, and ground to obtain modified shell powder.

[0060] Take 250 mL of 25 g / L titanium oxysulfate solution, add 25% of modified shell powder (by mass of titanium oxysulfate), add ammonia water under stirring in a 60℃ water bath, adjust the pH to neutral, stir in a constant temperature water bath for 30 min, let stand at room temperature for 2 h, take the precipitate, filter and wash, dry at 90℃ for 8 h, grind in a pulverizer for 5 min, calcine in a muffle furnace at 300℃ for 4 h, and cool naturally to obtain a composite material of modified titanium dioxide and shell powder.

[0061] S4: Preparation of Nano-Silica-Acrylic Emulsion

[0062] 120 parts of n-hexadecane, 0.3 parts of azobisisobutyronitrile, 15 parts of methyl methacrylate and 15 parts of butyl acrylate were mixed and stirred to dissolve. 0.9 parts of nano-silica were added and ultrasonically dispersed for 10 min. A deionized aqueous solution containing 1% sodium dodecyl sulfate was added and ultrasonically emulsified for 5 min. The mixture was cooled in an ice-water bath to obtain a monomer fine emulsion. The emulsion was transferred to a reactor and nitrogen gas was introduced under stirring for 10 min. The mixture was reacted at 70 °C for 3 h to obtain a nano-silica-acrylate emulsion.

[0063] S5: Preparation of Ultra-Weather-Resistant Powder Coatings

[0064] 300 parts of modified ultra-weather-resistant polyester resin, 22 parts of triglycidyl isocyanurate, 140 parts of modified titanium dioxide and shell powder composite material, 3 parts of nano-silica-acrylate emulsion, 1 part of benzoin and 701B brightening agent were added to a mixing tank and stirred at 400 r / min for 8 min.

[0065] After mixing evenly, pour into a twin-screw extruder for melt extrusion. Set the heating conditions as follows: Zone I temperature 110℃, Zone II temperature 125℃.

[0066] After extrusion and cooling to room temperature, the powder is fed into a grinding mill for grinding. The main mill speed is set to 8500 r / min, the auxiliary mill speed is set to 6500 r / min, and the sieve is set to 180 mesh. After extensive grinding and sieving, an ultra-weather-resistant powder coating is obtained.

[0067] Example 2

[0068] An ultra-weather-resistant powder coating for heavy machinery, such as Figures 1-2 As shown, the specific steps include:

[0069] S1: Synthesis of modified acrylate prepolymer

[0070] 14 parts of methyl methacrylate, 5 parts of methyl acrylate, 5 parts of n-butyl acrylate, 4 parts of n-butyl methacrylate and 5 parts of glycidyl methacrylate, 20 parts of vinyl-terminated polydimethylsiloxane sold by Wuhan Huaxiang Kejie Biotechnology Co., Ltd. and 0.55 parts of n-dodecyl mercaptan were added to the first storage bin and mixed evenly to obtain a mixed monomer. 2 parts of initiator AIBN and 37 parts of butanone were added to the second storage bin to obtain a mixture.

[0071] Add 13 parts of methyl ethyl ketone to the reactor. The gravity sensor detects that the gravity exceeds the set threshold and sends a signal to the controller to start the heating chamber and turn off the gravity sensor. The temperature is raised to 80°C. The first temperature detector detects that the material temperature has reached the set threshold. The controller opens the stirring valve, the nitrogen valve, the valve of the first storage hopper and the valve of the second storage hopper. The mixed monomer and the mixture are slowly added dropwise simultaneously within 3 hours. The reaction is carried out at a constant temperature for 4 hours.

[0072] When the first timer reaches the set duration, the controller shuts off the heating chamber, allowing it to cool naturally to room temperature. When the second temperature detector detects that the material temperature has dropped to the set threshold, the controller opens the neutralization valve, adds 2 parts of triethylamine, and stirs to neutralize the material. When the flow meter reaches the set threshold, the controller closes the neutralization valve and opens the short-time timer, stirring for 1 hour. When the short-time timer reaches the set duration, the controller closes the nitrogen valve and starts the heating chamber to heat to 60°C, evaporating most of the solvent. The vacuum pump is then manually turned on to create a vacuum, which is maintained at -0.099 MPa for 3 hours. The material is then discharged, yielding the modified acrylate prepolymer.

[0073] S2: Synthesis of Modified Ultra-Weather-Resistant Polyester Resin

[0074] 43 parts of neopentyl glycol, 1.2 parts of trimethylolpropane and 0.06 parts of monobutyltin oxide were added to a 7L reactor, stirring was started, nitrogen gas was introduced, and the mixture was heated to 150°C. 74 parts of isophthalic acid were added to the reactor, and the temperature was slowly increased to 260°C. The column top temperature was set to 102°C, and the reaction was carried out at a constant temperature for 4 hours.

[0075] The acid value was controlled at 12 mg KOH / g, and a modified acrylate prepolymer with an epoxy value of 0.6 mol / kg (35% of the mass of isophthalic acid) was added. The mixture was reacted at a constant temperature for 1 hour.

[0076] Add 0.3 parts of triphenyl phosphite and cyclohexanedicarboxylic acid, react at a constant temperature for 3 hours, control the acid value to be 50 mg KOH / g, and then apply a vacuum at -0.0121 MPa. The resin acid value drops to 35 mg KOH / g, and the vacuum is released.

[0077] Cool to 210℃, add 0.3 parts of triphenylethyl phosphorus bromide, stir for 10 min, and discharge at 200℃ to obtain modified ultra-weather resistant polyester resin;

[0078] S3: Preparation of modified titanium dioxide and shell powder composite materials

[0079] The shells were washed with deionized water, soaked in 0.25 mol / L sodium hydroxide solution for 2 hours, washed with deionized water, dried, crushed, and passed through a 150-mesh sieve to obtain shell powder.

[0080] Shell powder was mixed with distilled water and diethyl maleate, and ultrasonically dispersed for 15 min. Sodium stearate of 4% by weight of shell powder was added, and the mixture was reacted at 90℃ for 2 h. The mixture was then filtered with anhydrous ethanol, washed, dried, and ground to obtain modified shell powder.

[0081] Take 300 mL of 28 g / L titanium oxysulfate solution, add 30% of the modified shell powder (by mass of titanium oxysulfate), add ammonia water under stirring in a 70℃ water bath, adjust the pH to neutral, stir in a constant temperature water bath for 50 min, let stand at room temperature for 3 h, take the precipitate, filter and wash, dry at 110℃ for 6 h, grind in a pulverizer for 10 min, calcine in a muffle furnace at 450℃ for 3 h, and cool naturally to obtain the modified titanium dioxide and shell powder composite material;

[0082] S4: Preparation of Nano-Silica-Acrylic Emulsion

[0083] 130 parts of n-hexadecane, 0.4 parts of azobisisobutyronitrile, 20 parts of methyl methacrylate and 20 parts of butyl acrylate were mixed and stirred to dissolve. 1.2 parts of nano-silica were added and ultrasonically dispersed for 10 min. A deionized aqueous solution containing 2% sodium dodecyl sulfate was added and ultrasonically emulsified for 5 min. The mixture was cooled in an ice-water bath to obtain a monomer fine emulsion. The emulsion was transferred to a reactor and nitrogen gas was introduced under stirring for 15 min. The mixture was then reacted at 80 °C for 3 h to obtain a nano-silica-acrylate emulsion.

[0084] S5: Preparation of Ultra-Weather-Resistant Powder Coatings

[0085] 3250 parts of modified ultra-weather-resistant polyester resin, 25 parts of triglycidyl isocyanurate, 150 parts of modified titanium dioxide / shell powder composite material, 5 parts of nano-silica-acrylate emulsion, 3 parts of benzoin and 3 parts of brightener 701B were added to a mixing tank and stirred at 500 r / min for 4 min.

[0086] Modified ultra-weather resistant polyester resin, TGIC, modified titanium dioxide / shell powder composite material and nano-silica-acrylate emulsion were added to a mixing tank and stirred at 500 r / min for 4 min.

[0087] After mixing evenly, pour into a twin-screw extruder for melt extrusion. Set the heating conditions as follows: Zone I temperature 130℃, Zone II temperature 140℃.

[0088] After extrusion and cooling to room temperature, the powder is fed into a grinding mill for grinding. The main mill speed is set to 9500 r / min, the auxiliary mill speed is set to 7500 r / min, and the sieve is set to 220 mesh. After extensive grinding and sieving, an ultra-weather-resistant powder coating is obtained.

[0089] Example 3

[0090] An ultra-weather-resistant powder coating for heavy machinery, such as Figures 1-2 As shown, the specific steps include:

[0091] S1: Synthesis of modified acrylate prepolymer

[0092] 15 parts of methyl methacrylate, 6 parts of methyl acrylate, 6 parts of n-butyl acrylate, 5 parts of n-butyl methacrylate, 6 parts of glycidyl methacrylate, 20 parts of vinyl-terminated polydimethylsiloxane sold by Wuhan Huaxiang Kejie Biotechnology Co., Ltd., and 0.7 parts of n-dodecyl mercaptan were added to the first storage bin and mixed evenly to obtain a mixed monomer. 3 parts of initiator AIBN and 40 parts of butanone were added to the second storage bin to obtain a mixture.

[0093] Add 20 parts of methyl ethyl ketone to the reactor. The gravity sensor detects that the gravity exceeds the set threshold and sends a signal to the controller to start the heating chamber and turn off the gravity sensor. The temperature is raised to 85°C. The first temperature detector detects that the material temperature has reached the set threshold. The controller opens the stirring valve, nitrogen valve, first storage bin valve and second storage bin valve. The mixed monomer and mixture are slowly added dropwise simultaneously within 3 hours. The reaction is kept at a constant temperature for 5 hours.

[0094] When the first timer reaches the set duration, the controller shuts off the heating chamber, allowing it to cool naturally to room temperature. When the second temperature detector detects that the material temperature has dropped to the set threshold, the controller opens the neutralization valve, adds 1 part of triethylamine, and stirs to neutralize the material. When the flow meter reaches the set threshold, the controller closes the neutralization valve and opens the short-time timer, stirring for 1.5 hours. When the short-time timer reaches the set duration, the controller closes the nitrogen valve and starts the heating chamber to heat to 67°C, evaporating most of the solvent. The vacuum pump is then manually turned on to create a vacuum, which is maintained at -0.111 MPa for 2.5 hours. The material is then discharged, yielding the modified acrylate prepolymer.

[0095] S2: Synthesis of Modified Ultra-Weather-Resistant Polyester Resin

[0096] 38 parts of neopentyl glycol, 0.7 parts of trimethylolpropane and 0.03 parts of monobutyltin oxide were added to a 5.5L reactor, stirred, and nitrogen gas was introduced. The mixture was heated to 145°C. 69 parts of isophthalic acid were added to the reactor, and the temperature was slowly increased to 250°C. The column top temperature was set to 102°C, and the reaction was carried out at a constant temperature for 4.5 hours.

[0097] With the acid value controlled at 6 mg KOH / g, a modified acrylate prepolymer with an epoxy value of 0.4 mol / kg, accounting for 40% of the mass of isophthalic acid, was added and reacted at a constant temperature for 2 hours.

[0098] Add 0.15 parts of triphenyl phosphite and cyclohexanedicarboxylic acid, react at a constant temperature for 3 hours, control the acid value at 45 mg KOH / g, and then apply a vacuum at -0.102 MPa. The resin acid value drops to 32 mg KOH / g, and the vacuum is released.

[0099] Cool to 200℃, add 0.15 parts of triphenylethyl phosphorus bromide, stir for 10 min, and discharge at 180℃ to obtain modified ultra-weather resistant polyester resin;

[0100] S3: Preparation of modified titanium dioxide and shell powder composite materials

[0101] The shells were washed with deionized water, soaked in 0.15 mol / L sodium hydroxide solution for 1.5 h, washed with deionized water, dried, crushed, and passed through a 150-mesh sieve to obtain shell powder.

[0102] Shell powder was mixed with distilled water and diethyl maleate, and ultrasonically dispersed for 12 min. Sodium stearate of 2% by weight of shell powder was added, and the mixture was reacted at 80℃ for 2.5 h. The mixture was then filtered with anhydrous ethanol, washed, dried, and ground to obtain modified shell powder.

[0103] S3.3: Take 250 mL of 25 g / L titanium oxysulfate solution, add 25% of modified shell powder (by mass of titanium oxysulfate), add ammonia water under stirring in a 65℃ water bath, adjust the pH to neutral, stir in a constant temperature water bath for 40 min, let stand at room temperature for 3 h, take the precipitate, filter and wash, dry at 100℃ for 7 h, grind in a pulverizer for 8 min, calcine in a muffle furnace at 350℃ for 3.5 h, and cool naturally to obtain a composite material of modified titanium dioxide and shell powder;

[0104] S4: Preparation of Nano-Silica-Acrylic Emulsion

[0105] 140 parts of n-hexadecane, 0.5 parts of azobisisobutyronitrile, 30 parts of methyl methacrylate and 30 parts of butyl acrylate were mixed and stirred to dissolve. 1.8 parts of nano-silica were added and ultrasonically dispersed for 12 min. A deionized aqueous solution containing 1% sodium dodecyl sulfate was added and ultrasonically emulsified for 8 min. The mixture was cooled in an ice-water bath to obtain a monomer fine emulsion. The emulsion was transferred to a reactor and nitrogen gas was introduced under stirring for 12 min. The mixture was reacted at 75°C for 2.5 h to obtain a nano-silica-acrylate emulsion.

[0106] S5: Preparation of Ultra-Weather-Resistant Powder Coatings

[0107] 300 parts of modified ultra-weather-resistant polyester resin, 22 parts of triglycidyl isocyanurate, 145 parts of modified titanium dioxide / shell powder composite material, 3.6 parts of nano-silica-acrylate emulsion, 1.8 parts of benzoin and 1.8 parts of brightening agent 701B were added to a mixing tank and stirred at 450 r / min for 6 min.

[0108] After mixing evenly, pour into a twin-screw extruder for melt extrusion. Set the heating conditions as follows: Zone I temperature 120℃, Zone II temperature 130℃.

[0109] After extrusion and cooling to room temperature, the powder is fed into a grinding mill for grinding. The main mill speed is set to 9500 r / min, the auxiliary mill speed is set to 7500 r / min, and the sieve is set to 210 mesh. After extensive grinding and sieving, an ultra-weather-resistant powder coating is obtained.

[0110] Comparative Example 1

[0111] Compared to Example 1, in Comparative Example 1, the modified acrylate prepolymer was replaced with an equal amount of acrylate prepolymer in the preparation of the ultra-weather-resistant powder coating; otherwise, it was the same as in Example 1. Comparative Example 2

[0112] Compared with Example 1, the difference in this comparative example lies in the preparation method of the modified titanium dioxide and shell powder composite material;

[0113] The preparation method of the modified titanium dioxide / shell powder composite material in Comparative Example 2 is as follows: Take 250 mL of 25 g / L titanium oxysulfate solution, add 2% of the total mass of modified shell powder, add ammonia water under stirring in a 60℃ water bath, adjust the pH to neutral, stir in a constant temperature water bath for 30 min, let stand at room temperature for 2 h, take the precipitate, filter and wash, dry at 90℃ for 6 h, grind in a pulverizer for 5 min, calcine in a muffle furnace at 300℃ for 3 h, and cool naturally to obtain the modified titanium dioxide / shell powder composite material. Mix and stir the modified ultra-weather-resistant polyester resin and the modified titanium dioxide / shell powder composite material, and pour into a twin-screw screw press. The mixture was melt-extruded in a twin-screw extruder, cooled, ground, and sieved to obtain an ultra-weather-resistant powder coating, referred to as Example 1. Deionized water and methanol were mixed, cooled in an ice-water bath, and titanium tetrachloride was slowly added. The ratio of deionized water:methanol:titanium tetrachloride was 66:5:5. 2% of modified shell powder by mass was added, the pH was adjusted to neutral, and the mixture was hydrolyzed and aged. After filtration, washing, calcination, grinding, and sieving, a modified titanium dioxide / shell powder composite material was obtained. The modified ultra-weather-resistant polyester resin and the modified titanium dioxide / shell powder composite material were mixed and stirred, poured into a twin-screw extruder, melt-extruded, cooled, ground, and sieved to obtain an ultra-weather-resistant powder coating.

[0114] Test case

[0115] (1) The aging resistance and impact resistance of Examples 1-3 and Comparative Example 1 were determined.

[0116] Artificial aging test: An ultra-weather-resistant powder coating was applied to a substrate with a thickness of 0.15 mm. The coating was dried at 30℃ for 12 hours, baked at 60℃ for 30 minutes, and then baked at 140℃ for 30 minutes. The substrate was then mounted on a sample holder in an accelerated UV aging chamber. Half of the coating was covered, and the other half was subjected to UV exposure. The wavelength was set at 313 nm, the irradiation temperature at 60℃, the condensation temperature at 50℃, and the irradiation intensity at 0.71 W / (m²). 2 The gloss of the masking coating and the exposed coating was measured using a gloss meter for 500 hours (·nm), and recorded as Z and B respectively. The gloss retention rate was calculated as B / Z*100.

[0117] Impact resistance test: Apply the ultra-weather-resistant powder coating to a tinplate with a thickness of 0.2 mm. Dry the coating at 30℃ for 12 h, bake at 60℃ for 30 min, bake at 140℃ for 30 min, and acclimatize the coating at room temperature and 50% relative humidity for 16 h. Place the test plate face up on an anvil, fix the weight on the slide, adjust the height, press the control button to release the weight, and let the weight fall freely onto the coating. Lift the weight, remove the test plate, and observe the coating for cracks, wrinkles, peeling, etc. with a 4x magnifying glass. Record the height from which the weight falls onto the test plate, and take the maximum height from which the coating still maintains good condition after impact.

[0118] like Figure 2As shown, it can be seen that the gloss retention rate obtained by the artificial aging test of Example 1 is higher than that of the comparative example. It can be concluded that the light resistance of the coating formed by the ultra-weather-resistant powder coating prepared in Example 1 is better than that of the comparative example 1, that is, the weather resistance of Example 1 is superior. From the impact resistance test results, it can be seen that the impact resistance of the coating formed by the ultra-weather-resistant powder coating prepared in Example 1 is better than that of the comparative example 1.

[0119] (2) Measurement of solar reflection in Examples 1-3 and Comparative Example 2

[0120] Solar reflectance test: The ultra-weather-resistant powder coating was applied to the substrate and dried at 30℃ for 12 hours, baked at 60℃ for 30 minutes, and baked at 140℃ for 30 minutes. A 50 mm square of the coating was scraped off and placed on the sample holder. A pressed barium sulfate plate was used as the standard white plate and installed at the sample hole of the integrating sphere. The spectrophotometer operating parameters were set, and baseline scanning was performed in the wavelength range of 300-2500 nm. The sample holder was installed at the sample hole of the integrating sphere, and the spectral reflectance of the sample relative to the standard white plate was scanned in the same wavelength range. The spectral reflectance curve of the sample relative to the standard white plate was obtained. The data acquisition and data processing functions of the instrument were used to process and correct the data. The spectral reflectance of the standard white plate was recorded as ρ0, the spectral reflectance of the coating sample was recorded as T, the relative spectral distribution of solar radiation was recorded as S, and the wavelength interval was recorded as Δλ.

[0121] Solar reflectance of the coated sample .

[0122] like Figure 3 As shown, the solar reflectance of Example 1 after the solar reflectance test is greater than that of Comparative Example 2, that is, the solar radiation reflection performance of the coating formed by the ultra-weather-resistant powder coating prepared in Example 1 is better than that of Comparative Example 2.

[0123] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A super weather-resistant powder coating for heavy machinery, characterized in that, The raw materials include modified ultra-weather-resistant polyester resin, triglycidyl isocyanurate, modified titanium dioxide / shell powder composite material, and nano-silica-acrylate emulsion; The preparation method of the ultra-weather-resistant powder coating includes the following steps: Modified ultra-weather-resistant polyester resin, triglycidyl isocyanurate, modified titanium dioxide and shell powder composite material and nano-silica-acrylate emulsion are mixed and stirred, poured into a twin-screw extruder for melt extrusion, cooled, ground and sieved to obtain ultra-weather-resistant powder coating. The preparation method of the modified ultra-weather-resistant polyester resin is as follows: S2.1: Add the polyol and 0.03-0.06 parts of monobutyltin oxide into a 5-7L reactor, start stirring, introduce nitrogen gas, heat to 130-150℃, add the polyacid into the reactor, slowly raise the temperature to 240-260℃, set the column top temperature to 96-102℃, and react at a constant temperature for 4-5 hours; S2.2: Control the acid value to 4-12 mg KOH / g, add modified acrylate prepolymer, and react at a constant temperature for 1-3 hours; S2.3: Add 0.15-0.3 parts of triphenyl phosphite and acid hydrolysate, react at a constant temperature for 3-4 hours, control the acid value to 45-50 mgKOH / g, and apply vacuum at -0.095-(-0.0121) MPa until the resin acid value drops to 30-35 mgKOH / g, then release the vacuum. S2.4: Cool to 200-210℃, add 0.15-0.3 parts of triphenylethyl phosphorus bromide, stir for 5-10 minutes, and discharge at 180-200℃ to obtain modified ultra-weather resistant polyester resin; The method for preparing the modified acrylate prepolymer is as follows: Butanone, acrylate monomer, organosilicon, n-dodecyl mercaptan and initiator AIBN are mixed and heated in a nitrogen atmosphere. The mixture is then cooled, neutralized, the nitrogen atmosphere is turned off, most of the solvent is evaporated by heating, vacuum is applied, and the mixture is discharged to obtain the modified acrylate prepolymer. The preparation method of the modified titanium dioxide and shell powder composite material is as follows: S3.1: Wash the shells with deionized water, soak them in 0.15-0.25 mol / L sodium hydroxide solution for 1-2 hours, wash them with deionized water, dry them, crush them, and pass them through a 100-150 mesh sieve to obtain shell powder; S3.2: Mix shell powder with distilled water and diethyl maleate, disperse by ultrasonic vibration for 10-15 min, add sodium stearate at 2-4% of the mass of shell powder, react at 70-90℃ for 2-3 h, filter with anhydrous ethanol, wash, dry, grind to obtain modified shell powder. S3.3: Take 250-300 mL of 25-28 g / L titanium oxysulfate solution, add 25-30% of modified shell powder (by mass of titanium oxysulfate), add ammonia water under stirring in a water bath at 60-70℃, adjust the pH to neutral, stir in a constant temperature water bath for 30-50 min, let stand at room temperature for 2-3 h, take the precipitate, filter and wash, dry at 90-110℃ for 6-8 h, grind in a pulverizer for 5-10 min, calcine in a muffle furnace at 300-450℃ for 3-4 h, and cool naturally to obtain the modified titanium dioxide and shell powder composite material; The preparation method of the nano-silica-acrylate emulsion is as follows: Mix 120-140 parts of n-hexadecane, 0.3-0.5 parts of azobisisobutyronitrile, 15-30 parts of methyl methacrylate and 15-30 parts of butyl acrylate, stir to dissolve, add 0.9-1.8 parts of nano silica, ultrasonically disperse for 10-15 min, add a deionized aqueous solution containing 1-3% sodium dodecyl sulfate by mass, ultrasonically emulsify for 5-10 min, cool in an ice-water bath to obtain a monomer fine emulsion, transfer to a reactor, purge with nitrogen gas for 10-15 min with stirring, react at 70-80℃ for 2-3 h to obtain a nano silica-acrylate emulsion; The modified shell powder is obtained by modifying shell powder with sodium stearate.

2. The ultra-weather-resistant powder coating for heavy machinery according to claim 1, characterized in that, The preparation method of the modified acrylate prepolymer specifically includes the following steps: S1.1: Add acrylic acid monomer, 20-25 parts of organosilicon and 0.5-0.7 parts of n-dodecyl mercaptan to the first storage bin, mix evenly to obtain mixed monomers, add 1-3 parts of initiator AIBN and 30-40 parts of butanone to the second storage bin to obtain a mixture; S1.2: Add 10-20 parts of methyl ethyl ketone to the reactor. The gravity sensor detects that the gravity exceeds the set threshold and sends a signal to the controller to start the heating chamber and turn off the gravity sensor. The first temperature detector detects that the material temperature has reached the set threshold. The controller opens the stirring valve, nitrogen valve, first storage bin valve and second storage bin valve, and slowly adds the mixed monomer and mixture to carry out a constant temperature reaction. S1.3: When the first timer reaches the set duration, the controller shuts off the heating chamber and allows it to cool naturally to room temperature. When the second temperature detector detects that the material temperature has dropped to the set threshold, the controller opens the neutralization valve and adds 1-3 parts of triethylamine to stir and neutralize the material. When the flow meter reaches the set threshold, the controller closes the neutralization valve and opens the short-time timer to perform neutralization and stirring. When the short-time timer reaches the set duration, the controller closes the nitrogen valve and starts the heating chamber to heat and evaporate most of the solvent. The vacuum pump is manually turned on to create a vacuum, and the material is discharged to obtain the modified acrylate prepolymer.

3. The ultra-weather-resistant powder coating for heavy machinery according to claim 2, characterized in that, In step S1.1, the acrylate monomers are specifically 13-15 parts of methyl methacrylate, 4-6 parts of methyl acrylate, 4-6 parts of n-butyl acrylate, 3-5 parts of n-butyl methacrylate and 4-6 parts of glycidyl methacrylate, and the organosilicon is vinyl-terminated polydimethylsiloxane.

4. The ultra-weather-resistant powder coating for heavy machinery according to claim 1, characterized in that, The polyol is specifically 38-43 parts neopentyl glycol and 0.7-1.2 parts trimethylolpropane, and the polyacid is 69-74 parts isophthalic acid.

5. The ultra-weather-resistant powder coating for heavy machinery according to claim 1, characterized in that, The preparation of the ultra-weather-resistant powder coating specifically includes the following steps: S5: Preparation of Ultra-Weather-Resistant Powder Coatings S5.1: Add 300-320 parts of modified ultra-weather-resistant polyester resin, 22-25 parts of triglycidyl isocyanurate, 140-150 parts of modified titanium dioxide / shell powder composite material, 3-5 parts of nano-silica-acrylate emulsion, 1-3 parts of benzoin and 1-3 parts of brightening agent 701B into a mixing tank and stir at a speed of 400-500 r / min for 4-8 min; S5.2: After mixing evenly, pour into a twin-screw extruder for melt extrusion. Set the heating conditions as follows: Zone I temperature 110-130℃, Zone II temperature 125-140℃. S5.3: After extrusion and cooling to room temperature, the powder is fed into a grinding mill for grinding. The main mill speed is set to 8500-9500 r / min, the auxiliary mill speed is set to 6500-7500 r / min, and the sieve is set to 180-220 mesh. After extensive grinding and sieving, an ultra-weather-resistant powder coating is obtained.

6. The ultra-weather-resistant powder coating for heavy machinery according to claim 1, characterized in that, The epoxy value of the modified acrylate prepolymer added in step S2.2 is 0.4-0.6 mol / kg, and the amount of modified acrylate prepolymer added is 30-40% of the mass of the polybasic acid.

7. The ultra-weather-resistant powder coating for heavy machinery according to claim 1, characterized in that, The acid hydrolysate added in step S2.3 is cyclohexanedicarboxylic acid.

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