Polyurethane powder coating with good heat preservation and preparation method thereof

Abstract

The present application relates to the technical field of paint, in particular to a polyurethane powder coating with good heat preservation and insulation performance, which is configured according to the mass fraction of each raw material: 25-40 parts of hydroxyl acrylic acid resin; 10-20 parts of hexamethylene diisocyanate trimer; 8-18 parts of rice husk ash derived porous silica microspheres; 5-15 parts of waste tire rubber powder modified carbonized particles; 3-8 parts of functional filler; 0.5-1.5 parts of polyethylene wax leveling agent; and 0.2-0.8 parts of polyether modified silicone defoaming agent. In the present application, the thermal bridge effect caused by interface defects can be reduced, the porous structure can significantly reduce the overall thermal conductivity of the coating through the synergistic effect of scattering thermal radiation, inhibiting gas molecular convection and conduction and prolonging the solid heat conduction path, and this structural characteristic makes it an ideal insulation functional unit, thereby greatly improving the heat preservation performance of the coating.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a polyurethane powder coating with good thermal insulation properties and its preparation method. Background Technology

[0002] Polyurethane powder coating is a high-performance, environmentally friendly coating based on polyurethane resin. It forms a film through thermosetting and has excellent mechanical properties, weather resistance, and decorative properties. This coating does not contain organic solvents, meets environmental protection requirements, and is suitable for surface protection and decoration of metals, buildings, and industrial equipment. It is widely used in automobiles, home appliances, and outdoor facilities, making it an ideal choice that combines functionality and aesthetics.

[0003] Existing polyurethane powder coatings have unobstructed heat conduction paths, making them unable to effectively block heat transfer. Their internal interface bonding is also weak, easily forming thermal bridges, which further weakens the insulation effect. As a result, the thermal insulation performance of polyurethane powder coatings needs to be improved.

[0004] Based on this, the present invention provides a polyurethane powder coating with good thermal insulation performance and its preparation method. Summary of the Invention

[0005] The purpose of this invention is to provide a polyurethane powder coating with good thermal insulation performance and its preparation method, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a polyurethane powder coating with good thermal insulation performance, wherein the coating is prepared according to the mass proportions of each raw material:

[0007] 25-40 parts of hydroxyl acrylic resin;

[0008] 10-20 parts of hexamethylene diisocyanate trimer;

[0009] 8–18 parts of porous silica microspheres derived from rice husk ash;

[0010] 5-15 parts of modified carbonized particles from waste tire rubber powder;

[0011] 3-8 parts of functional filler;

[0012] 0.5–1.5 parts of polyethylene wax leveling agent;

[0013] 0.2 to 0.8 parts of polyether-modified silicone defoamer.

[0014] Preferably, the preparation method of the rice husk ash-derived porous silica microspheres includes the following steps:

[0015] Step 1: Select rice husk ash as raw material, and after being separated by a vibrating sieve with a screen size of 120-150 mesh, put it into an acid-resistant reaction vessel, add 5wt% hydrochloric acid solution, and pickle for 4-5 hours at a temperature of 70-80℃ and a stirring speed of 250-300r / min to obtain the pickled material.

[0016] Step 2: Dehydrate the pickled material by passing it through a plate and frame filter press under a filtration pressure of 0.4-0.6 MPa, then transfer it to a rotary kiln, set the rotation speed to 1-3 r / min, the heating rate to 10℃ / min, heat it to 600-700℃, and keep it at that temperature for 2-3 hours to obtain amorphous silica.

[0017] Step 3: Weigh out the required amount of silica and ammonium bicarbonate in a mass ratio of 1:0.3 and mix them. Then transfer the mixture to a tube sintering furnace, set the nitrogen flow rate to 1.5 L / min, the heating rate to (10-15) °C / min, heat to 700-800 °C, and hold for 1-2 hours to obtain porous microspheres, which are rice husk ash derived porous silica microspheres, for later use.

[0018] Preferably, the liquid-to-solid ratio of the rice husk ash and hydrochloric acid solution separated in step 1 is 5:1.

[0019] Preferably, the method for preparing modified carbonized particles of waste tire rubber powder includes the following steps:

[0020] Step 1: Select waste tires as raw materials, crush and grind them to obtain 70-80 mesh tire rubber powder, put them into an ozone reactor, and treat them for 30-50 minutes at a temperature of 40-50℃ and a stirring speed of 180-200 r / min to obtain the first powder.

[0021] Step 2: Weigh out the first powder and sodium lignosulfonate in a mass ratio of 10:1 as needed and put them into a high-speed mixer for premixing for 5 to 10 minutes. Then transfer them to a horizontal carbonization furnace and heat them to 400 to 500°C at a heating rate of 20°C / min. Keep them at this temperature for 2 to 3 hours to obtain carbonized particles.

[0022] Step 3: The carbonized particles are separated from the incompletely carbonized impurities by an eddy air separator, and then the particles with a diameter of 10-50μm are collected by sieving. These are the modified carbonized particles of waste tire rubber powder, which are ready for use.

[0023] Preferably, the functional filler raw material is mica powder with a particle size of 30-50 μm. It is added to a reaction vessel to prepare a solution containing 0.5 mol / L zinc ions and 0.3 mol / L phosphate ions. The pH of the solution is adjusted to 4.5. The solution is stirred and dispersed at a stirring speed of 200 r / min with ultrasonic assistance. The temperature of the reaction vessel is controlled at 70-80℃. Then, ammonia water is added dropwise to adjust the pH to 6.8. The reaction is continued for 2-3 hours to generate a zinc-based composite deposition layer. After centrifugation, dehydration, and spray drying, the functional filler is obtained and ready for use.

[0024] Preferably, the preparation method of the polyurethane powder coating with good thermal insulation performance includes the following steps:

[0025] S1: Weigh out the hydroxyl acrylic resin and hexamethylene diisocyanate trimer as needed and add them to the internal mixer for premixing to obtain the base material;

[0026] S2: Add rice husk ash-derived porous silica microspheres to the internal mixer of S1 and preheat to 60°C. Then add waste tire rubber powder modified carbonized particles and functional fillers in sequence. Raise the temperature to 90-95°C and switch to a high-speed dispersion disc. Continue mixing for 10-15 minutes to obtain fine material.

[0027] S3: Weigh out polyethylene wax leveling agent as needed, preheat to 65-75℃, then add polyether modified silicone defoamer for premixing, then add fine materials and stir through a double planetary mixer to form a homogeneous mixture;

[0028] S4: Transfer the mixture to a co-rotating twin-screw extruder, set the temperature to 90℃ in zone 1, 115℃ in zone 2, and 100℃ in zone 3, and after melt blending, granulate it into particles with a particle size of 2-3mm using a water ring pelletizer.

[0029] S5: Feed the particulate matter into a cryogenic airflow pulverizer, set the classifier speed to 4000-4500 r / min and the pulverizing pressure to 0.9-1 MPa, and obtain a polyurethane powder coating with good thermal insulation properties.

[0030] Preferably, in S1, the mixing machine is set to a mixing temperature of 80-90℃, a rotation speed of 40-50 r / min, and a mixing time of 20-30 min.

[0031] Preferably, the dual planetary mixer in S3 is set to a speed of 200-300 r / min, a vacuum degree of -0.08 MPa, and a mixing time of 5-10 min.

[0032] Preferably, in S4, the screw diameter of the co-rotating twin-screw extruder is 45mm, the length-to-diameter ratio is 48:1, the screw speed is 120-150r / min, and the die head pressure is 14-15MPa.

[0033] Preferably, the viscosity of the polyethylene wax leveling agent is 200-400 mPa·s.

[0034] Compared with the prior art, the beneficial effects of the present invention are:

[0035] 1. In this preparation method, the rice husk ash-derived porous silica microspheres have a highly developed porous structure. The abundant pores inside can effectively block the heat transfer path. The surface of the microspheres is rich in active groups, which can form a stable interface bond with the resin matrix, reducing the thermal bridging effect caused by interface defects. The porous structure significantly reduces the overall thermal conductivity of the coating through the synergistic effect of scattering thermal radiation, inhibiting gas molecule convection and conduction, and extending the solid heat conduction path. This structural characteristic makes it an ideal heat insulation functional unit, thereby greatly improving the thermal insulation performance of the coating.

[0036] 2. In this preparation method, after ozone oxidation and carbonization modification, waste tire rubber powder generates abundant polar functional groups on its surface, which can form strong chemical bonds with the reactive groups in the resin matrix. The elastic modulus of the carbonized particles matches that of the resin matrix, which can effectively buffer the internal stress generated during the coating curing process and avoid interfacial peeling caused by stress concentration. At the same time, the lamellar structure of the carbonized particles forms a physical anchoring effect in the coating, further enhancing the mechanical interlocking force between the coating and the substrate. This dual mechanism significantly improves the adhesion of the coating, enabling it to maintain stable bonding under complex working conditions.

[0037] 3. In this preparation method, the functional filler forms a continuous and dense passivation barrier in the coating through the zinc-based composite layer deposited on the surface, which effectively inhibits the penetration and corrosion of the substrate by the environmental medium. The three-dimensional interpenetrating network structure formed by the functional filler, rice husk ash microspheres and carbonized particles can fill the micro-defects inside the coating, reduce the crack propagation path, and thus improve the overall density. In addition, the ultraviolet absorption characteristics and chemical stability of the functional filler work synergistically to significantly enhance the coating's resistance to photothermal aging and chemical erosion, so that the coating can still maintain its performance integrity under long-term exposure. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1

[0040] This embodiment provides a polyurethane powder coating with good thermal insulation performance, which is formulated according to the mass parts of each raw material:

[0041] 25 parts of hydroxyl acrylic resin;

[0042] 10 parts of hexamethylene diisocyanate trimer;

[0043] Eight portions of porous silica microspheres derived from rice husk ash;

[0044] Five parts of modified carbonized particles from waste tire rubber powder;

[0045] 3 parts of functional filler;

[0046] 0.5 parts of polyethylene wax leveling agent;

[0047] 0.2 parts of polyether-modified silicone defoamer.

[0048] The preparation method of rice husk ash-derived porous silica microspheres includes the following steps:

[0049] Step 1: Select rice husk ash as raw material, and after it is separated by a vibrating sieve with a screen size of 120 mesh, put it into an acid-resistant reaction vessel, add 5wt% hydrochloric acid solution, and pickle for 4 hours at a temperature of 70℃ and a stirring speed of 250r / min to obtain the pickled material.

[0050] Step 2: Dehydrate the pickled material through a plate and frame filter press under a filtration pressure of 0.4 MPa, then transfer it to a rotary kiln, set the rotation speed to 1 r / min, the heating rate to 10℃ / min, heat to 600℃, and calcine for 2 hours to obtain amorphous silica.

[0051] Step 3: Weigh out the required amount of silica and ammonium bicarbonate in a mass ratio of 1:0.3 and mix them. Then transfer the mixture to a tube sintering furnace, set the nitrogen flow rate to 1.5 L / min, the heating rate to 10 °C / min, heat to 700 °C, and hold for 1 hour to obtain porous microspheres, which are rice husk ash derived porous silica microspheres, for later use.

[0052] In step 1, the ratio of the rice husk ash and hydrochloric acid solution separated is 5:1.

[0053] The method for preparing modified carbonized particles from waste tire rubber powder includes the following steps:

[0054] Step 1: Select waste tires as raw materials, crush and grind them to obtain 70-mesh tire rubber powder, put them into an ozone reactor, and process them at a temperature of 40℃ and a stirring speed of 180r / min for 30 minutes to obtain the first powder.

[0055] Step 2: Weigh out the first powder and sodium lignosulfonate in a mass ratio of 10:1 as needed and put them into a high-speed mixer for premixing for 5 minutes. Then transfer them to a horizontal carbonization furnace and heat them to 400°C at a heating rate of 20°C / min. Hold the temperature for 2 hours to obtain carbonized particles.

[0056] Step 3: The carbonized particles are separated from the incompletely carbonized impurities by an eddy air separator, and then the particles with a diameter of 10μm are collected by sieving. These are the modified carbonized particles of waste tire rubber powder, which are ready for use.

[0057] The functional filler raw material is mica powder with a particle size of 30 μm. It is added to a reaction vessel to prepare a solution containing 0.5 mol / L zinc ions and 0.3 mol / L phosphate ions. The pH of the solution is adjusted to 4.5. The solution is stirred and dispersed at a stirring speed of 200 r / min with ultrasonic assistance. The temperature of the reaction vessel is controlled at 70℃. Then, ammonia water is added dropwise to adjust the pH to 6.8. The reaction is continued for 2 hours to generate a zinc-based composite deposition layer. After centrifugation, dehydration and spray drying, the functional filler is obtained and ready for use.

[0058] The preparation method of polyurethane powder coating with good thermal insulation performance includes the following steps:

[0059] S1: Weigh out the hydroxyl acrylic resin and hexamethylene diisocyanate trimer as needed and add them to the internal mixer for premixing to obtain the base material;

[0060] S2: Add rice husk ash-derived porous silica microspheres to the internal mixer of S1 and preheat to 60°C. Then add waste tire rubber powder modified carbonized particles and functional fillers in sequence, raise the temperature to 90°C and switch the high-speed dispersion disc, and continue mixing for 10 minutes to obtain fine material.

[0061] S3: Weigh out polyethylene wax leveling agent as needed, preheat to 65°C, then add polyether modified silicone defoamer and premix, then add fine materials and stir through a double planetary mixer to form a homogeneous mixture;

[0062] S4: Transfer the mixture to a co-rotating twin-screw extruder, set the temperature to 90℃ in zone 1, 115℃ in zone 2, and 100℃ in zone 3, and after melt blending, granulate it into particles with a particle size of 2mm using a water ring pelletizer.

[0063] S5: Feed the particulate matter into a cryogenic airflow pulverizer, set the classifier speed to 4000 r / min and the pulverizing pressure to 0.9 MPa, and obtain a polyurethane powder coating with good thermal insulation properties.

[0064] In S1, the mixing temperature of the internal mixer is set to 80℃, the speed to 40r / min, and the mixing time to 20min.

[0065] The S3 dual planetary mixer is set to a speed of 200 r / min, a vacuum of -0.08 MPa, and a mixing time of 5 min.

[0066] Among them, the S4 co-rotating twin-screw extruder has a screw diameter of 45mm, a length-to-diameter ratio of 48:1, a screw speed of 120r / min, and a die head pressure of 14MPa.

[0067] The viscosity of the polyethylene wax leveling agent is 200 mPa·s.

[0068] Example 2

[0069] A polyurethane powder coating with good thermal insulation properties is formulated according to the mass proportions of each raw material:

[0070] 40 parts of hydroxyl acrylic resin;

[0071] 20 parts of hexamethylene diisocyanate trimer;

[0072] 18 portions of porous silica microspheres derived from rice husk ash;

[0073] 15 parts of modified carbonized particles from waste tire rubber powder;

[0074] 8 parts of functional filler;

[0075] 1.5 parts of polyethylene wax leveling agent;

[0076] 0.8 parts of polyether-modified silicone defoamer.

[0077] The preparation method of rice husk ash-derived porous silica microspheres includes the following steps:

[0078] Step 1: Select rice husk ash as raw material, and after it is separated by a vibrating screen with a mesh size of 150, put it into an acid-resistant reaction vessel, add 5wt% hydrochloric acid solution, and pickle for 5 hours at a temperature of 80℃ and a stirring speed of 300r / min to obtain the pickled material.

[0079] Step 2: Dehydrate the pickled material through a plate and frame filter press under a filtration pressure of 0.6 MPa, then transfer it to a rotary kiln, set the rotation speed to 3 r / min, the heating rate to 10℃ / min, heat to 700℃, and calcine for 3 hours to obtain amorphous silica.

[0080] Step 3: Weigh out the required amount of silica and ammonium bicarbonate in a mass ratio of 1:0.3 and mix them. Then transfer the mixture to a tube sintering furnace, set the nitrogen flow rate to 1.5 L / min, the heating rate to 15 °C / min, heat to 800 °C, and hold for 2 hours to obtain porous microspheres, which are rice husk ash derived porous silica microspheres, for later use.

[0081] In step 1, the ratio of the rice husk ash and hydrochloric acid solution separated is 5:1.

[0082] The method for preparing modified carbonized particles from waste tire rubber powder includes the following steps:

[0083] Step 1: Select waste tires as raw materials, crush and grind them to obtain 80-mesh tire rubber powder, put them into an ozone reactor, and treat them for 50 minutes at a temperature of 50℃ and a stirring speed of 200r / min to obtain the first powder.

[0084] Step 2: Weigh out the first powder and sodium lignosulfonate in a mass ratio of 10:1 as needed and put them into a high-speed mixer for premixing for 10 minutes. Then transfer them to a horizontal carbonization furnace and heat them to 500°C at a heating rate of 20°C / min. Hold the temperature for 3 hours to obtain carbonized particles.

[0085] Step 3: The carbonized particles are separated from the incompletely carbonized impurities by an eddy air separator, and then the particles with a diameter of 50μm are collected by sieving. These are the modified carbonized particles of waste tire rubber powder, which are ready for use.

[0086] The functional filler raw material is mica powder with a particle size of 50 μm. It is added to a reaction vessel to prepare a solution containing 0.5 mol / L zinc ions and 0.3 mol / L phosphate ions. The pH of the solution is adjusted to 4.5. The solution is stirred and dispersed at a stirring speed of 200 r / min with ultrasonic assistance. The temperature of the reaction vessel is controlled at 80℃. Then, ammonia water is added dropwise to adjust the pH to 6.8. The reaction is continued for 3 hours to generate a zinc-based composite deposition layer. After centrifugation, dehydration and spray drying, the functional filler is obtained and ready for use.

[0087] The preparation method of polyurethane powder coating with good thermal insulation performance includes the following steps:

[0088] S1: Weigh out the hydroxyl acrylic resin and hexamethylene diisocyanate trimer as needed and add them to the internal mixer for premixing to obtain the base material;

[0089] S2: Add rice husk ash-derived porous silica microspheres to the internal mixer of S1 and preheat to 60°C. Then add waste tire rubber powder modified carbonized particles and functional fillers in sequence, raise the temperature to 95°C and switch the high-speed dispersion disc, and continue mixing for 15 minutes to obtain fine material.

[0090] S3: Weigh out polyethylene wax leveling agent as needed, preheat to 75°C, then add polyether modified silicone defoamer for premixing, then add fine materials and stir through a double planetary mixer to form a homogeneous mixture;

[0091] S4: Transfer the mixture to a co-rotating twin-screw extruder, set the temperature to 90℃ in zone 1, 115℃ in zone 2, and 100℃ in zone 3, and after melt blending, granulate it into particles with a particle size of 3mm using a water ring pelletizer.

[0092] S5: Feed the particulate matter into a cryogenic airflow pulverizer, set the classifier speed to 4500 r / min and the pulverizing pressure to 1 MPa, and obtain a polyurethane powder coating with good thermal insulation properties.

[0093] In S1, the mixing temperature of the internal mixer is set to 90℃, the rotation speed to 50r / min, and the mixing time to 30min.

[0094] The S3 dual planetary mixer is set to a speed of 300 r / min, a vacuum of -0.08 MPa, and a mixing time of 10 min.

[0095] Among them, the S4 co-rotating twin-screw extruder has a screw diameter of 45mm, a length-to-diameter ratio of 48:1, a screw speed of 150r / min, and a die head pressure of 15MPa.

[0096] The viscosity of the polyethylene wax leveling agent is 400 mPa·s.

[0097] Example 3

[0098] A polyurethane powder coating with good thermal insulation properties is formulated according to the mass proportions of each raw material:

[0099] 32 parts of hydroxyl acrylic resin;

[0100] 15 parts of hexamethylene diisocyanate trimer;

[0101] 14 portions of porous silica microspheres derived from rice husk ash;

[0102] 10 parts of modified carbonized particles from waste tire rubber powder;

[0103] 5 parts of functional filler;

[0104] 1 part polyethylene wax leveling agent;

[0105] 0.5 parts of polyether-modified silicone defoamer.

[0106] The preparation method of rice husk ash-derived porous silica microspheres includes the following steps:

[0107] Step 1: Select rice husk ash as raw material, and after being separated by a vibrating sieve with a screen size of 130 mesh, put it into an acid-resistant reaction vessel, add 5wt% hydrochloric acid solution, and pickle for 4.5 hours at a temperature of 75℃ and a stirring speed of 270r / min to obtain the pickled material.

[0108] Step 2: Dehydrate the pickled material through a plate and frame filter press under a filtration pressure of 0.5 MPa, then transfer it to a rotary kiln, set the rotation speed to 2 r / min, the heating rate to 10℃ / min, heat to 650℃, and calcine for 2.5 h to obtain amorphous silica.

[0109] Step 3: Weigh out the required amount of silica and ammonium bicarbonate in a mass ratio of 1:0.3 and mix them. Then transfer the mixture to a tube sintering furnace, set the nitrogen flow rate to 1.5 L / min, the heating rate to 13 °C / min, heat to 750 °C, and hold for 1.5 h to obtain porous microspheres, which are rice husk ash derived porous silica microspheres, for later use.

[0110] In step 1, the ratio of the rice husk ash and hydrochloric acid solution separated is 5:1.

[0111] The method for preparing modified carbonized particles from waste tire rubber powder includes the following steps:

[0112] Step 1: Select waste tires as raw materials, crush and grind them to obtain 75-mesh tire rubber powder, put them into an ozone reactor, and process them at a temperature of 45℃ and a stirring speed of 190r / min for 40 minutes to obtain the first powder.

[0113] Step 2: Weigh out the first powder and sodium lignosulfonate in a mass ratio of 10:1 as needed and put them into a high-speed mixer for premixing for 8 minutes. Then transfer them to a horizontal carbonization furnace and heat them to 450°C at a heating rate of 20°C / min. Hold the temperature for 2.5 hours to obtain carbonized particles.

[0114] Step 3: The carbonized particles are separated from the incompletely carbonized impurities by an eddy air separator, and then the particles with a diameter of 30μm are collected by sieving. These are the modified carbonized particles of waste tire rubber powder, which are ready for use.

[0115] The functional filler raw material is mica powder with a particle size of 40 μm. It is added to a reaction vessel to prepare a solution containing 0.5 mol / L zinc ions and 0.3 mol / L phosphate ions. The pH of the solution is adjusted to 4.5. The solution is stirred and dispersed at a stirring speed of 200 r / min with ultrasonic assistance. The temperature of the reaction vessel is controlled at 75℃. Then, ammonia water is added dropwise to adjust the pH to 6.8. The reaction is continued for 2.5 h to generate a zinc-based composite deposition layer. After centrifugation, dehydration and spray drying, the functional filler is obtained and ready for use.

[0116] The preparation method of polyurethane powder coating with good thermal insulation performance includes the following steps:

[0117] S1: Weigh out the hydroxyl acrylic resin and hexamethylene diisocyanate trimer as needed and add them to the internal mixer for premixing to obtain the base material;

[0118] S2: Add rice husk ash-derived porous silica microspheres to the internal mixer of S1 and preheat to 60°C. Then add waste tire rubber powder modified carbonized particles and functional fillers in sequence. Raise the temperature to 93°C and switch to a high-speed dispersion disc. Continue mixing for 12 minutes to obtain fine material.

[0119] S3: Weigh out polyethylene wax leveling agent as needed, preheat to 70°C, then add polyether modified silicone defoamer for premixing, then add fine materials and stir through a double planetary mixer to form a homogeneous mixture;

[0120] S4: Transfer the mixture to a co-rotating twin-screw extruder, set the temperature to 90℃ in zone 1, 115℃ in zone 2, and 100℃ in zone 3, and after melt blending, granulate it into particles with a particle size of 2.5mm using a water ring pelletizer.

[0121] S5: Feed the particulate matter into a cryogenic airflow pulverizer, set the classifier speed to 4300 r / min and the pulverizing pressure to 0.95 MPa, and obtain a polyurethane powder coating with good thermal insulation properties.

[0122] In S1, the mixing temperature of the internal mixer is set to 85℃, the rotation speed to 45r / min, and the mixing time to 25min.

[0123] The S3 dual planetary mixer is set to a speed of 250 r / min, a vacuum of -0.08 MPa, and a mixing time of 8 min.

[0124] Among them, the S4 co-rotating twin-screw extruder has a screw diameter of 45mm, a length-to-diameter ratio of 48:1, a screw speed of 135r / min, and a die head pressure of 14.5MPa.

[0125] The viscosity of the polyethylene wax leveling agent is 300 mPa·s.

[0126] Comparative Example 1: The difference between this comparative example and Examples 1-3 is that no rice husk ash-derived porous silica microspheres are added during the preparation of the polyurethane powder coating with good thermal insulation performance in this comparative example.

[0127] Comparative Example 2 differs from Examples 1-3 in that: no waste tire rubber powder modified carbonized particles are added during the preparation of polyurethane powder coating with good thermal insulation performance in this comparative example.

[0128] Comparative Example 3 differs from Examples 1-3 in that no functional fillers are added during the preparation of the polyurethane powder coating with good thermal insulation performance in this comparative example.

[0129] Test methods and test items:

[0130] Thermal conductivity: Tested using a heat flow thermal conductivity meter according to GB / T 10297-2015 (temperature difference 20℃).

[0131] Adhesion: The residual peeling rate of the tape was tested according to the cross-cut test in GB / T 9286-1998.

[0132] Impact resistance: According to GB / T 1732-93, the coating surface is subjected to free fall impact by a 1kg weight.

[0133] The polyurethane powder coatings with good thermal insulation properties prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests, and the test data are recorded in the table below:

[0134]

[0135] By comparing the data in Examples 1-3 and Comparative Example 1 in the table, it can be seen that the polyurethane powder coating prepared by the preparation method of Comparative Example 1 has a significantly higher thermal conductivity (0.062 W / (m·K), a lower adhesion residue rate (85.3%), and a lower impact resistance (30 cm) compared to the polyurethane powder coating prepared by Examples 1-3. This indicates that the absence of rice husk ash-derived porous silica microspheres results in a lack of porous thermal insulation structure in the coating, an increase in the heat conduction path, a decrease in interfacial bonding strength, and a significant reduction in mechanical properties. This demonstrates that rice husk ash-derived porous silica microspheres have a highly developed porous structure. The abundant pores inside can effectively block the heat transfer path. The surface of the microspheres is rich in active groups, which can form a stable interfacial bond with the resin matrix, reducing the thermal bridging effect caused by interfacial defects. The porous structure significantly reduces the overall thermal conductivity of the coating through the synergistic effect of scattering thermal radiation, inhibiting gas molecule convection and conduction, and extending the solid heat conduction path. This structural characteristic makes it an ideal thermal insulation functional unit, thereby greatly improving the thermal insulation performance of the coating.

[0136] By comparing the data in Examples 1-3 and Comparative Example 2 in the table, it can be seen that the polyurethane powder coating prepared by the method of Comparative Example 2 has a higher thermal conductivity (0.055 W / (m·K), a lower adhesion residue rate (90.1%), and a lower impact resistance (35 cm) compared to the polyurethane powder coating prepared by Examples 1-3. This indicates that the absence of carbonized particles results in a lack of lamellar barrier structures in the coating, leading to increased thermal conductivity. At the same time, the interfacial chemical bonding weakens, resulting in decreased mechanical properties. This suggests that after ozone oxidation and carbonization modification, waste tire rubber powder generates abundant polar functional groups on its surface, which can form strong chemical bonds with the reactive groups in the resin matrix. The elastic modulus of the carbonized particles matches that of the resin matrix, effectively buffering the internal stress generated during coating curing and preventing interfacial peeling caused by stress concentration. Simultaneously, the lamellar structure of the carbonized particles forms a physical anchoring effect in the coating, further enhancing the mechanical interlocking force between the coating and the substrate. This dual mechanism significantly improves the adhesion of the coating, enabling it to maintain stable bonding even under complex working conditions.

[0137] By comparing the data in Examples 1-3 and Comparative Example 3 in the table, it can be seen that the polyurethane powder coating prepared by the method of Comparative Example 3 has a higher thermal conductivity (0.050 W / (m·K), a lower adhesion residue rate (92.5%), and a lower impact resistance (40 cm) compared to the polyurethane powder coating prepared by Examples 1-3. This indicates that the absence of functional fillers leads to a decrease in coating density, an increase in thermal conductivity, a weakening of interfacial bonding strength, and a reduction in mechanical properties. This suggests that the functional fillers, through the zinc-based composite layer deposited on the surface, form a continuous and dense passivation barrier in the coating, effectively inhibiting the penetration and corrosion of the substrate by environmental media. The three-dimensional interpenetrating network structure formed by the functional fillers, rice husk ash microspheres, and carbonized particles can fill microscopic defects inside the coating, reduce crack propagation paths, and thus improve overall density. In addition, the synergistic effect of the ultraviolet absorption characteristics and chemical stability of the functional fillers significantly enhances the coating's resistance to photothermal aging and chemical erosion, enabling the coating to maintain its performance integrity even under long-term exposure.

[0138] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0139] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A polyurethane powder coating with good thermal insulation properties, characterized in that, This coating is formulated according to the mass proportions of each raw material: 25-40 parts of hydroxyl acrylic resin; 10-20 parts of hexamethylene diisocyanate trimer; 8–18 parts of porous silica microspheres derived from rice husk ash; 5-15 parts of modified carbonized particles from waste tire rubber powder; 3-8 parts of functional filler; 0.5–1.5 parts of polyethylene wax leveling agent; 0.2–0.8 parts of polyether-modified silicone defoamer; The preparation method of the rice husk ash-derived porous silica microspheres includes the following steps: Step 1: Select rice husk ash as raw material, and after being separated by a vibrating sieve with a screen size of 120-150 mesh, put it into an acid-resistant reaction vessel, add 5wt% hydrochloric acid solution, and pickle for 4-5 hours at a temperature of 70-80℃ and a stirring speed of 250-300r / min to obtain the pickled material. Step 2: Dehydrate the pickled material by passing it through a plate and frame filter press under a filtration pressure of 0.4-0.6 MPa, then transfer it to a rotary kiln, set the rotation speed to 1-3 r / min, the heating rate to 10℃ / min, heat it to 600-700℃, and keep it at that temperature for 2-3 hours to obtain amorphous silica. Step 3: Weigh out the required amount of silica and ammonium bicarbonate in a mass ratio of 1:0.3 and mix them. Then transfer the mixture to a tube sintering furnace, set the nitrogen flow rate to 1.5 L / min, the heating rate to (10-15) ℃ / min, heat to 700-800 ℃, and hold for 1-2 h to obtain porous microspheres, which are rice husk ash derived porous silica microspheres, for later use. The method for preparing modified carbonized particles from waste tire rubber powder includes the following steps: Step 1: Select waste tires as raw materials, crush and grind them to obtain 70-80 mesh tire rubber powder, put them into an ozone reactor, and treat them for 30-50 minutes at a temperature of 40-50℃ and a stirring speed of 180-200 r / min to obtain the first powder. Step 2: Weigh out the first powder and sodium lignosulfonate in a mass ratio of 10:1 as needed and put them into a high-speed mixer for premixing for 5 to 10 minutes. Then transfer them to a horizontal carbonization furnace and heat them to 400 to 500°C at a heating rate of 20°C / min. Keep them at this temperature for 2 to 3 hours to obtain carbonized particles. Step 3: Separate incompletely carbonized impurities from the carbonized particles using an eddy air separator, and then collect particles with a diameter of 10-50μm by sieving. These are the modified carbonized particles of waste tire rubber powder, ready for use. The functional filler raw material is selected from mica powder with a particle size of 30-50 μm. It is added to a reaction vessel to prepare a solution containing 0.5 mol / L zinc ions and 0.3 mol / L phosphate ions. The pH of the solution is adjusted to 4.

5. The solution is stirred and dispersed at a stirring speed of 200 r / min with ultrasonic assistance. The temperature of the reaction vessel is controlled at 70-80℃. Then, ammonia water is added dropwise to adjust the pH to 6.

8. The reaction is continued for 2-3 hours to generate a zinc-based composite deposition layer. After centrifugation, dehydration, and spray drying, the functional filler is obtained and ready for use.

2. A method for preparing a polyurethane powder coating with good thermal insulation performance according to claim 1, characterized in that, Includes the following steps: S1: Weigh out the hydroxyl acrylic resin and hexamethylene diisocyanate trimer as needed and add them to the internal mixer for premixing to obtain the base material; S2: Add rice husk ash-derived porous silica microspheres to the internal mixer of S1 and preheat to 60°C. Then add waste tire rubber powder modified carbonized particles and functional fillers in sequence. Heat to 90-95°C and switch to high-speed dispersion disc. Continue mixing for 10-15 minutes to obtain fine material. S3: Weigh out polyethylene wax leveling agent as needed, preheat to 65-75℃, then add polyether modified silicone defoamer for premixing, then add fine materials and stir through a double planetary mixer to form a homogeneous mixture; S4: Transfer the mixture to a co-rotating twin-screw extruder, set the temperature to 90℃ in zone 1, 115℃ in zone 2, and 100℃ in zone 3, and after melt blending, granulate it into particles with a particle size of 2-3mm using a water ring pelletizer. S5: Feed the particulate matter into a cryogenic airflow pulverizer, set the classifier speed to 4000-4500 r / min and the pulverizing pressure to 0.9-1 MPa, and obtain a polyurethane powder coating with good thermal insulation properties.

3. The method for preparing polyurethane powder coating with good thermal insulation performance according to claim 2, characterized in that, The internal mixer in S1 is set to a mixing temperature of 80-90℃, a rotation speed of 40-50 r / min, and a mixing time of 20-30 min.

4. The method for preparing polyurethane powder coating with good thermal insulation performance according to claim 2, characterized in that, The S3 double planetary mixer is set with a rotation speed of 200-300 r / min, a vacuum degree of -0.08 MPa, and a mixing time of 5-10 min.

5. The method for preparing polyurethane powder coating with good thermal insulation performance according to claim 2, characterized in that, The S4 co-rotating twin-screw extruder has a screw diameter of 45mm, a length-to-diameter ratio of 48:1, a screw speed of 120-150r / min, and a die head pressure of 14-15MPa.

6. The method for preparing polyurethane powder coating with good thermal insulation performance according to claim 2, characterized in that, The viscosity of the polyethylene wax leveling agent is 200-400 mPa·s.

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