A powder coating for plastic flower pots and a process for its preparation

Abstract

The application provides a powder coating for plastic flowerpots and a preparation process thereof, and relates to the technical field of coatings.The preparation process steps include: uniformly mixing raw materials, i.e., polyester resin, polypropylene resin, a curing agent, an antioxidant, modified fillers, pigments, aluminum powder and a coupling agent, then adding the mixture into a double-screw extruder for melt extrusion, then tabletting, cooling, and crushing to a particle size of 10-60 mu m, wherein the weight content of the powder with a particle size of 10-30 mu m is 30-40%.The application optimizes the formula of the coating, reduces the curing temperature and time of the powder coating, enables the powder coating to be quickly cured at a lower temperature, avoids deformation or scorching of the plastic flowerpots during the baking process, and effectively improves the adhesion of the coating.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a powder coating for use on plastic flower pots and its preparation process. Background Technology

[0002] With the rise of modern horticulture, plastic flower pots have become the first choice for many families and gardening enthusiasts due to their lightweight, durability, and affordability. However, ordinary plastic flower pots often appear monotonous in appearance and texture, failing to meet the needs of modern home decoration. Therefore, applying powder coating technology to the surface of plastic flower pots to enhance their aesthetics and durability has significant market application value.

[0003] Powder coating is a solid powder composed of resin, curing agent, filler, pigment, and additives. It is applied to the surface of the object through electrostatic spraying or other methods, and then baked to melt, level, and cure into a film. This type of coating does not contain any organic solvents, has a high utilization rate, and is simple and feasible to operate. It has now become a widely recognized environmentally friendly coating in the industry.

[0004] Although powder coatings have been widely used in many fields, there are still some shortcomings in the surface treatment of plastic flower pots: these include high curing temperatures, insufficient coating performance, and complex processes. Conventional powder coatings typically require curing at 180–200°C for 10–20 minutes to form a film. High curing temperatures can easily cause deformation or scorching of plastic flower pots, limiting the application of powder coatings on them. Furthermore, traditional powder coatings often suffer from poor adhesion after application, or fail to achieve ideal coating performance, such as weather resistance and corrosion resistance, thus affecting the lifespan and aesthetics of the plastic flower pots. Traditional powder coating processes are cumbersome, requiring multiple spraying and baking steps, which not only increases production costs but also reduces production efficiency.

[0005] Based on this, the present invention provides a process and a coating for powder coating on plastic flower pots. Summary of the Invention

[0006] The purpose of this invention is to provide a powder coating for plastic flower pots and its preparation process, which can be rapidly cured at a lower temperature, thereby improving the coating's adhesion and weather resistance.

[0007] On one hand, the present invention provides a process for preparing powder coatings for plastic flower pots, the steps of which include: mixing raw materials polyester resin, polypropylene resin, curing agent, antioxidant, modified filler, pigment, aluminum powder, and coupling agent evenly, and then adding them to a twin-screw extruder for melt extrusion, setting the temperature as follows: Zone 1: 80-90℃, Zone 2: 105-115℃, Zone 3: 110-120℃, Zone 4: 100-110℃, feeding screw speed 20-30 r / min, extrusion twin-screw speed 300-340 r / min, and then pressing, cooling, and pulverizing to a particle size of 10-60 μm, wherein the powder with a particle size of 10-30 μm accounts for 30-40% by weight.

[0008] Further, the raw materials include the following parts by weight: 50-60 parts polyester resin, 20-30 parts polypropylene resin, 8-12 parts curing agent, 6-10 parts antioxidant, 15-20 parts modified filler, 0-10 parts pigment, 3-5 parts aluminum powder, and 1-2 parts coupling agent.

[0009] Further, the polyester resin comprises a carboxyl-terminated polyester resin with a weight ratio of (2-3):(6-10) parts and an acid value of 40-60 mgKOH / g and an acid value of 100-140 mgKOH / g.

[0010] Furthermore, the curing agent is triglycidyl isocyanurate.

[0011] Furthermore, the antioxidants include hindered phenolic antioxidants and phosphite antioxidants in a weight ratio of (1-2):(2-3).

[0012] Furthermore, the hindered phenolic antioxidant includes antioxidant 1010 or antioxidant 1076.

[0013] Furthermore, the phosphite antioxidant includes at least one of Irganox 168, PEP-36, and S-9228.

[0014] Furthermore, the preparation method of the modified filler includes: adding calcium sulfate and basalt fiber to an ethanol aqueous solution for ultrasonic mixing, heating to 55-65℃, adding a silane coupling agent at a stirring speed of 400-500 r / min, and then continuing to stir for 2-3 hours. After filtration, washing, and drying, the modified filler is obtained.

[0015] Further, the mass concentration of the ethanol aqueous solution is 35-45%, and the weight ratio of the calcium sulfate and basalt fiber, the ethanol aqueous solution and the silane coupling agent is (2-4):(4-5):(20-24):(0.4-0.8).

[0016] Calcium sulfate (gypsum) is a common inorganic compound with good stability and thermal stability. When used as a filler in coatings, it can improve the hardness and abrasion resistance of the coating. Basalt fiber is a new type of inorganic, environmentally friendly, high-performance fiber material with excellent properties such as high strength, high modulus, acid and alkali resistance, and corrosion resistance. When used as a reinforcing material in coatings, it can significantly improve the mechanical properties and weather resistance of the coating. The combined use of calcium sulfate and basalt fiber can leverage their complementary advantages to further improve the overall performance of the coating. Simultaneously, due to the modification effect of silane coupling agents, the dispersibility and compatibility of both in the coating are improved, which helps to accelerate the curing and improve the adhesion of the coating.

[0017] Furthermore, the pigment includes at least one of carbon black and titanium dioxide.

[0018] Furthermore, the coupling agent is a silane coupling agent and an aluminate coupling agent in a weight ratio of 1:(3-4).

[0019] On the other hand, the present invention also provides a coating material prepared using the aforementioned process for powder coatings used on plastic flower pots.

[0020] The beneficial effects of this invention are as follows:

[0021] The powder coating prepared by this invention can achieve rapid curing at low temperature. By optimizing the coating formula, the curing temperature and time of the powder coating are reduced, enabling it to cure rapidly at a lower temperature and preventing plastic flower pots from deforming or scorching during baking.

[0022] This invention utilizes polyester resin and polypropylene resin as the matrix resin materials. These two resins possess excellent melt flowability and film-forming properties, enabling them to soften and fuse rapidly at lower temperatures, thus providing a foundation for the rapid curing of the coating. Triglycidyl isocyanurate is used as the curing agent. This curing agent has highly efficient cross-linking reaction capabilities, allowing it to chemically react with the resin at lower temperatures to form a stable network structure, thereby achieving rapid curing.

[0023] This invention, by selecting carboxyl-terminated polyester resins with different acid values ​​in the formulation, can adjust the crosslinking density and flexibility of the coating, thereby optimizing the coating's adhesion and weather resistance.

[0024] This invention uses treated calcium sulfate and basalt fiber as modified fillers to enhance the mechanical properties and weather resistance of the coating. The addition of a silane coupling agent further improves the interfacial bonding between the filler and the resin, thereby improving the coating's adhesion. Furthermore, calcium sulfate and basalt fiber themselves possess excellent weather resistance, resisting erosion from natural factors such as ultraviolet radiation and oxidation. The addition of these inorganic fillers enhances the coating's weather resistance, enabling it to maintain excellent performance for extended periods in outdoor environments. In addition, the modified filler undergoes ultrasonic mixing and stirring during preparation, resulting in more uniform dispersion of filler particles in the resin. This uniform dispersion facilitates the formation of a uniform cured layer during the curing process, thereby improving the coating's curing speed and quality.

[0025] Building upon this, the present invention further utilizes aluminum powder and modified fillers in a compound formulation. Aluminum powder possesses a metallic luster, enabling it to reflect light and increase the gloss and shine of the coating. The aluminum powder interacts with the polymers in the coating to form a protective coating that prevents erosion from external factors (such as oxygen and water), thereby improving the coating's adhesion and weather resistance, and promoting rapid curing of the coating.

[0026] This invention utilizes the synergistic effect of hindered phenolic antioxidants and phosphite antioxidants to effectively capture free radicals generated during the curing and use of coatings, preventing coating aging and thus improving their weather resistance.

[0027] The raw materials of this invention also use a coupling agent, which is a combination of silane coupling agent and aluminate coupling agent. It can not only react chemically with the functional groups on the surface of the filler to form chemical bonds, but also interact with the functional groups in the resin. This interaction can form a protective layer between the filler and the resin to prevent external factors (such as ultraviolet rays, oxidants, etc.) from corroding the coating, thereby improving the weather resistance of the coating. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, 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.

[0029] The present invention will be further illustrated by the following embodiments. In the specific embodiments of the present invention, the polypropylene resin is PP-H GD040, the silane coupling agent is KH560, and the aluminate coupling agent is DL-430. The hindered phenolic antioxidant selected in the embodiments and comparative examples of the present invention is antioxidant 1010, and the phosphite antioxidant is Irganox 168.

[0030] Example 1

[0031] This embodiment provides a process for applying powder coating to plastic flower pots, the steps of which include:

[0032] The raw materials, polyester resin, polypropylene resin, curing agent, antioxidant, modified filler, pigment, aluminum powder, and coupling agent, are mixed evenly and then added to a twin-screw extruder for melt extrusion. The set temperatures are: Zone 1: 85℃, Zone 2: 110℃, Zone 3: 115℃, Zone 4: 105℃. The feed screw speed is 25r / min, and the extrusion twin-screw speed is 320r / min. Then, the mixture is tableted, cooled, and pulverized to a particle size of 10-60μm, of which the powder with a particle size of 10-30μm accounts for 35% by weight.

[0033] The raw materials include the following parts by weight: 55 parts polyester resin, 25 parts polypropylene resin, 10 parts curing agent, 8 parts antioxidant, 17.5 parts modified filler, 5 parts pigment, 4 parts aluminum powder, and 1.5 parts coupling agent.

[0034] The polyester resin includes a carboxyl-terminated polyester resin with a weight ratio of 2.5:8 parts and an acid value of 50 mg KOH / g, and a carboxyl-terminated polyester resin with an acid value of 120 mg KOH / g; the curing agent is triglycidyl isocyanurate; the antioxidants include hindered phenolic antioxidants and phosphite antioxidants with a weight ratio of 3:5; the pigment is titanium dioxide; and the coupling agent is a silane coupling agent and an aluminate coupling agent with a weight ratio of 1:3.5.

[0035] The preparation method of the modified filler includes: adding calcium sulfate and basalt fiber to an ethanol aqueous solution for ultrasonic mixing, heating to 60°C, adding a silane coupling agent at a stirring speed of 450 r / min, and then continuing to stir for 2.5 h. After filtration, rinsing with deionized water, and drying, the modified filler is obtained. The mass concentration of the ethanol aqueous solution is 40%, and the weight ratio of calcium sulfate and basalt fiber, ethanol aqueous solution and silane coupling agent is 3:4.5:22:0.6.

[0036] Example 1: First, a 30μm thick layer of WEPE-03 electrostatic paint was sprayed onto the surface of a plastic sheet. This made the product surface conductive, allowing it to absorb the electrostatically sprayed powder coating while increasing the adhesion of the powder coating to the product. Then, the powder prepared in Example 1 was sprayed onto the plastic sheet using high-voltage electrostatic spraying. The sprayed plastic sheet was placed in a curing oven, and the curing temperature was adjusted. The film thickness and hardness were tested. When the curing time was 15 minutes and the curing temperature was adjusted to 130℃, 135℃, and 140℃, the film thickness was 140-150μm, the pencil hardness was 3H, and the adhesion was grade 0. Therefore, the coating formulation and process provided in Example 1 of this invention can effectively reduce the curing temperature compared to the common curing temperature of 180-200℃ for powder coatings.

[0037] Example 2

[0038] This embodiment provides a process for applying powder coating to plastic flower pots, the steps of which include:

[0039] The raw materials, polyester resin, polypropylene resin, curing agent, antioxidant, modified filler, pigment, aluminum powder, and coupling agent, are mixed evenly and then added to a twin-screw extruder for melt extrusion. The set temperatures are: Zone 1: 80℃, Zone 2: 105℃, Zone 3: 110℃, Zone 4: 100℃. The feed screw speed is 20r / min, and the extrusion twin-screw speed is 300r / min. Then, the mixture is tableted, cooled, and pulverized to a particle size of 10-60μm, of which the powder with a particle size of 10-30μm accounts for 30% by weight.

[0040] The raw materials include the following parts by weight: 50 parts polyester resin, 20 parts polypropylene resin, 8 parts curing agent, 6 parts antioxidant, 15 parts modified filler, 2 parts pigment, 3 parts aluminum powder, and 1 part coupling agent.

[0041] The polyester resin includes a carboxyl-terminated polyester resin with an acid value of 40 mg KOH / g and an acid value of 100 mg KOH / g, with a weight ratio of 1:3; the curing agent is triglycidyl isocyanurate; the antioxidants include hindered phenolic antioxidants and phosphite antioxidants with a weight ratio of 1:2; the pigment is titanium dioxide; and the coupling agent is a silane coupling agent and an aluminate coupling agent with a weight ratio of 1:3.

[0042] The preparation method of the modified filler includes: adding calcium sulfate and basalt fiber to an ethanol aqueous solution for ultrasonic mixing, heating to 55°C, adding a silane coupling agent at a stirring speed of 400 r / min, and then continuing to stir for 2 hours. After filtration, rinsing with deionized water, and drying, the modified filler is obtained. The mass concentration of the ethanol aqueous solution is 35%, and the weight ratio of calcium sulfate and basalt fiber, ethanol aqueous solution and silane coupling agent is 2:4:20:0.4.

[0043] Example 3

[0044] This embodiment provides a process for applying powder coating to plastic flower pots, the steps of which include:

[0045] The raw materials, polyester resin, polypropylene resin, curing agent, antioxidant, modified filler, pigment, aluminum powder, and coupling agent, are mixed evenly and then added to a twin-screw extruder for melt extrusion. The set temperatures are: Zone 1: 90℃, Zone 2: 115℃, Zone 3: 120℃, Zone 4: 110℃. The feed screw speed is 30r / min, and the extrusion twin-screw speed is 340r / min. Then, the mixture is tableted, cooled, and pulverized to a particle size of 10-60μm, of which the powder with a particle size of 10-30μm accounts for 40% by weight.

[0046] The raw materials include the following parts by weight: 60 parts polyester resin, 30 parts polypropylene resin, 12 parts curing agent, 10 parts antioxidant, 20 parts modified filler, 10 parts pigment, 5 parts aluminum powder, and 2 parts coupling agent.

[0047] The polyester resin includes a carboxyl-terminated polyester resin with a weight ratio of 3:10 and an acid value of 60 mg KOH / g, and a carboxyl-terminated polyester resin with an acid value of 140 mg KOH / g; the curing agent is triglycidyl isocyanurate; the antioxidants include hindered phenolic antioxidants and phosphite antioxidants with a weight ratio of 2:3; the pigment is titanium dioxide; and the coupling agent is a silane coupling agent and an aluminate coupling agent with a weight ratio of 1:4.

[0048] The preparation method of the modified filler includes: adding calcium sulfate and basalt fiber to an ethanol aqueous solution for ultrasonic mixing, heating to 65°C, adding a silane coupling agent at a stirring speed of 500 r / min, and then continuing to stir for 3 hours. After filtration, rinsing with deionized water, and drying, the modified filler is obtained. The mass concentration of the ethanol aqueous solution is 45%, and the weight ratio of calcium sulfate and basalt fiber, ethanol aqueous solution and silane coupling agent is 4:5:24:0.8.

[0049] Example 4

[0050] This embodiment provides a process for applying powder coating to plastic flower pots, the steps of which include:

[0051] The raw materials, polyester resin, polypropylene resin, curing agent, antioxidant, modified filler, pigment, aluminum powder, and coupling agent, are mixed evenly and then added to a twin-screw extruder for melt extrusion. The set temperatures are: Zone 1: 84℃, Zone 2: 108℃, Zone 3: 116℃, Zone 4: 103℃. The feed screw speed is 23r / min, and the extrusion twin-screw speed is 310r / min. The product is then tableted, cooled, and pulverized to a particle size of 10-60μm, of which the powder with a particle size of 10-30μm accounts for 32% by weight.

[0052] The raw materials include the following parts by weight: 54 parts polyester resin, 26 parts polypropylene resin, 10 parts curing agent, 7 parts antioxidant, 18 parts modified filler, 3 parts pigment, 4 parts aluminum powder, and 2 parts coupling agent.

[0053] The polyester resin includes a carboxyl-terminated polyester resin with a weight ratio of 3:8 parts and an acid value of 50 mg KOH / g, and a carboxyl-terminated polyester resin with an acid value of 110 mg KOH / g; the curing agent is triglycidyl isocyanurate; the antioxidants include hindered phenolic antioxidants and phosphite antioxidants with a weight ratio of 1:3; the pigment is titanium dioxide; the coupling agent is a silane coupling agent and an aluminate coupling agent with a weight ratio of 1:3.

[0054] The preparation method of the modified filler includes: adding calcium sulfate and basalt fiber to an ethanol aqueous solution for ultrasonic mixing, heating to 58°C, adding a silane coupling agent at a stirring speed of 460 r / min, and then continuing to stir for 2.5 h. After filtration, rinsing with deionized water, and drying, the modified filler is obtained. The mass concentration of the ethanol aqueous solution is 42%, and the weight ratio of calcium sulfate and basalt fiber, ethanol aqueous solution and silane coupling agent is 3:4:21:0.5.

[0055] Comparative Example 1

[0056] This comparative example provides a process for powder coating on plastic flower pots. The raw materials—polyester resin, polypropylene resin, curing agent, antioxidant, modified filler, pigment, zinc powder, and coupling agent—are mixed evenly and then melt-extruded in a twin-screw extruder. The set temperatures are: Zone 1: 85℃, Zone 2: 110℃, Zone 3: 115℃, Zone 4: 105℃. The feed screw speed is 25 r / min, and the extrusion twin-screw speed is 320 r / min. The mixture is then tableted, cooled, and pulverized to a particle size of 10-60 μm, with the powder containing 10-30 μm particles comprising 35% by weight.

[0057] The raw materials include the following parts by weight: 55 parts polyester resin, 25 parts polypropylene resin, 10 parts curing agent, 8 parts antioxidant, 17.5 parts modified filler, 5 parts pigment, 4 parts zinc powder, and 1.5 parts coupling agent.

[0058] The polyester resin includes a carboxyl-terminated polyester resin with a weight ratio of 2.5:8 parts and an acid value of 50 mg KOH / g, and a carboxyl-terminated polyester resin with an acid value of 120 mg KOH / g; the curing agent is triglycidyl isocyanurate; the antioxidants include hindered phenolic antioxidants and phosphite antioxidants with a weight ratio of 3:5; the pigment is titanium dioxide; the coupling agent is a silane coupling agent and an aluminate coupling agent with a weight ratio of 1:3.5.

[0059] The preparation method of the modified filler includes: adding calcium sulfate and basalt fiber to an ethanol aqueous solution for ultrasonic mixing, heating to 60°C, adding a silane coupling agent at a stirring speed of 450 r / min, and then continuing to stir for 2.5 h. After filtration, rinsing with deionized water, and drying, the modified filler is obtained. The mass concentration of the ethanol aqueous solution is 40%, and the weight ratio of calcium sulfate and basalt fiber, ethanol aqueous solution and silane coupling agent is 3:4.5:22:0.6.

[0060] Comparative Example 2

[0061] This comparative example provides a process for powder coating on plastic flower pots. The raw materials—polyester resin, polypropylene resin, curing agent, antioxidant, modified filler, pigment, and coupling agent—are mixed evenly and then melt-extruded in a twin-screw extruder. The set temperatures are: Zone 1: 85℃, Zone 2: 110℃, Zone 3: 115℃, Zone 4: 105℃. The feed screw speed is 25 r / min, and the extrusion twin-screw speed is 320 r / min. The mixture is then tableted, cooled, and pulverized to a particle size of 10-60 μm, with the powder containing 10-30 μm particles comprising 35% by weight.

[0062] The raw materials include the following parts by weight: 55 parts polyester resin, 25 parts polypropylene resin, 10 parts curing agent, 8 parts antioxidant, 17.5 parts modified filler, 5 parts pigment, and 1.5 parts coupling agent;

[0063] The polyester resin includes a carboxyl-terminated polyester resin with a weight ratio of 2.5:8 parts and an acid value of 50 mg KOH / g, and a carboxyl-terminated polyester resin with an acid value of 120 mg KOH / g; the curing agent is triglycidyl isocyanurate; the antioxidants include hindered phenolic antioxidants and phosphite antioxidants with a weight ratio of 3:5; the pigment is titanium dioxide; the coupling agent is a silane coupling agent and an aluminate coupling agent with a weight ratio of 1:3.5.

[0064] The preparation method of the modified filler includes: adding calcium sulfate and basalt fiber to an ethanol aqueous solution for ultrasonic mixing, heating to 60°C, adding a silane coupling agent at a stirring speed of 450 r / min, and then continuing to stir for 2.5 h. After filtration, rinsing with deionized water, and drying, the modified filler is obtained. The mass concentration of the ethanol aqueous solution is 40%, and the weight ratio of calcium sulfate and basalt fiber, ethanol aqueous solution and silane coupling agent is 3:4.5:22:0.6.

[0065] Comparative Example 3

[0066] This comparative example provides a process for powder coating on plastic flower pots. The raw materials—polyester resin, polypropylene resin, curing agent, antioxidant, modified filler, pigment, aluminum powder, and coupling agent—are mixed evenly and then melt-extruded in a twin-screw extruder. The set temperatures are: Zone 1: 85℃, Zone 2: 110℃, Zone 3: 115℃, Zone 4: 105℃. The feed screw speed is 25 r / min, and the extrusion twin-screw speed is 320 r / min. The mixture is then tableted, cooled, and pulverized to a particle size of 10-60 μm, with the powder containing 10-30 μm particles comprising 35% by weight.

[0067] The raw materials include the following parts by weight: 55 parts polyester resin, 25 parts polypropylene resin, 10 parts curing agent, 8 parts antioxidant, 17.5 parts modified filler, 5 parts pigment, 4 parts aluminum powder, and 1.5 parts coupling agent.

[0068] The polyester resin includes a carboxyl-terminated polyester resin with a weight ratio of 2.5:8 parts and an acid value of 50 mg KOH / g, and a carboxyl-terminated polyester resin with an acid value of 120 mg KOH / g; the curing agent is triglycidyl isocyanurate; the antioxidants include hindered phenolic antioxidants and phosphite antioxidants with a weight ratio of 3:5; the pigment is titanium dioxide; the coupling agent is a silane coupling agent and an aluminate coupling agent with a weight ratio of 1:3.5.

[0069] The preparation method of the modified filler includes: adding calcium sulfate and carbon fiber to an ethanol aqueous solution for ultrasonic mixing, heating to 60°C, adding a silane coupling agent at a stirring speed of 450 r / min, and then continuing to stir for 2.5 h. After filtration, rinsing with deionized water, and drying, the modified filler is obtained. The mass concentration of the ethanol aqueous solution is 40%, and the weight ratio of calcium sulfate, carbon fiber, ethanol aqueous solution, and silane coupling agent is 3:4.5:22:0.6.

[0070] Comparative Example 4

[0071] This comparative example provides a process for powder coating on plastic flower pots. The raw materials—polyester resin, polypropylene resin, curing agent, antioxidant, modified filler, pigment, aluminum powder, and coupling agent—are mixed evenly and then melt-extruded in a twin-screw extruder. The set temperatures are: Zone 1: 85℃, Zone 2: 110℃, Zone 3: 115℃, Zone 4: 105℃. The feed screw speed is 25 r / min, and the extrusion twin-screw speed is 320 r / min. The mixture is then tableted, cooled, and pulverized to a particle size of 10-60 μm, with the powder containing 10-30 μm particles comprising 35% by weight.

[0072] The raw materials include the following parts by weight: 55 parts polyester resin, 25 parts polypropylene resin, 10 parts curing agent, 8 parts antioxidant, 17.5 parts modified filler, 5 parts pigment, 4 parts aluminum powder, and 1.5 parts coupling agent.

[0073] The polyester resin includes a carboxyl-terminated polyester resin with a weight ratio of 2.5:8 parts and an acid value of 50 mg KOH / g, and a carboxyl-terminated polyester resin with an acid value of 120 mg KOH / g; the curing agent is triglycidyl isocyanurate; the antioxidants include hindered phenolic antioxidants and phosphite antioxidants with a weight ratio of 3:5; the pigment is titanium dioxide; the coupling agent is a silane coupling agent and an aluminate coupling agent with a weight ratio of 1:3.5.

[0074] The preparation method of the modified filler includes: adding calcium sulfate to an ethanol aqueous solution for ultrasonic mixing, heating to 60°C, adding a silane coupling agent at a stirring speed of 450 r / min, and then continuing to stir for 2.5 h. After filtration, rinsing with deionized water, and drying, the modified filler is obtained. The mass concentration of the ethanol aqueous solution is 40%, and the weight ratio of calcium sulfate, ethanol aqueous solution, and silane coupling agent is 3:4.5:22:0.6.

[0075] Comparative Example 5

[0076] This comparative example provides a process for powder coating on plastic flower pots. The raw materials—polyester resin, polypropylene resin, curing agent, antioxidant, modified filler, pigment, aluminum powder, and coupling agent—are mixed evenly and then melt-extruded in a twin-screw extruder. The set temperatures are: Zone 1: 85℃, Zone 2: 110℃, Zone 3: 115℃, Zone 4: 105℃. The feed screw speed is 25 r / min, and the extrusion twin-screw speed is 320 r / min. The mixture is then tableted, cooled, and pulverized to a particle size of 10-60 μm, with the powder containing 10-30 μm particles comprising 35% by weight.

[0077] The raw materials include the following parts by weight: 55 parts polyester resin, 25 parts polypropylene resin, 10 parts curing agent, 8 parts antioxidant, 17.5 parts modified filler, 5 parts pigment, 4 parts aluminum powder, and 1.5 parts coupling agent.

[0078] The polyester resin includes a carboxyl-terminated polyester resin with a weight ratio of 2.5:8 parts and an acid value of 50 mg KOH / g, and a carboxyl-terminated polyester resin with an acid value of 120 mg KOH / g; the curing agent is triglycidyl isocyanurate; the antioxidants include hindered phenolic antioxidants and phosphite antioxidants with a weight ratio of 3:5; the pigment is titanium dioxide; the coupling agent is a silane coupling agent and an aluminate coupling agent with a weight ratio of 1:3.5.

[0079] The preparation method of the modified filler includes: adding basalt fiber to an ethanol aqueous solution for ultrasonic mixing, heating to 60℃, adding a silane coupling agent at a stirring speed of 450 r / min, and then continuing to stir for 2.5 h. After filtration, rinsing with deionized water, and drying, the modified filler is obtained. The mass concentration of the ethanol aqueous solution is 40%, and the weight ratio of the basalt fiber, the ethanol aqueous solution, and the silane coupling agent is 3:4.5:22:0.6.

[0080] Comparative Example 6

[0081] This comparative example provides a process for powder coating on plastic flower pots. The raw materials—polyester resin, polypropylene resin, curing agent, antioxidant, pigment, aluminum powder, and coupling agent—are mixed evenly and then melt-extruded in a twin-screw extruder. The set temperatures are: Zone 1: 85℃, Zone 2: 110℃, Zone 3: 115℃, Zone 4: 105℃. The feed screw speed is 25 r / min, and the extrusion twin-screw speed is 320 r / min. The mixture is then tableted, cooled, and pulverized to a particle size of 10-60 μm, with the powder having a particle size of 10-30 μm comprising 35% by weight.

[0082] The raw materials include the following parts by weight: 55 parts polyester resin, 25 parts polypropylene resin, 10 parts curing agent, 8 parts antioxidant, 5 parts pigment, 4 parts aluminum powder, and 1.5 parts coupling agent;

[0083] The polyester resin includes a carboxyl-terminated polyester resin with a weight ratio of 2.5:8 parts and an acid value of 50 mg KOH / g, and a carboxyl-terminated polyester resin with an acid value of 120 mg KOH / g; the curing agent is triglycidyl isocyanurate; the antioxidants include hindered phenolic antioxidants and phosphite antioxidants with a weight ratio of 3:5; the pigment is titanium dioxide; and the coupling agent is a silane coupling agent and an aluminate coupling agent with a weight ratio of 1:3.5.

[0084] Example 2: First, a layer of WEPE-03 electrostatic paint with a thickness of 30 μm was sprayed onto the surface of the plastic sheet. This made the product surface conductive, which could adsorb the electrostatically sprayed powder coating and increase the adhesion of the powder coating to the product. Then, the powder coatings prepared in Examples 1-4 and Comparative Examples 1-6 were sprayed onto the plastic sheet by high-voltage electrostatic spraying. The sprayed plastic sheet was placed in a curing oven, and the curing time was 15 min, the curing temperature was 135℃, and the film thickness was 150 μm. The coated plastic sheet samples were tested as follows.

[0085] 1. Adhesion: Tested according to GB / T 9286-2021 standard. The results are judged in 5 levels: 0: The cut edge is completely smooth, with no cells peeling off; 1: A small amount of coating peels off at the intersection of the cuts, but the affected area of ​​the cross-cut cannot be significantly greater than 5%; 2: The coating peels off at the intersection of the cuts or the cut edge, and the affected area of ​​the cross-cut is significantly greater than 5% but less than 15%; 3: The coating peels off in large fragments along the cut edge, and on different parts of the cells, it peels off partially or completely, and the affected area of ​​the cross-cut is significantly greater than 15% but less than 35%; 4: The coating peels off in large fragments along the cut edge, and some cells peel off partially or completely, and the affected area of ​​the cross-cut is significantly greater than 35% but less than 65%; 5: The affected area of ​​the cross-cut is significantly greater than 65%.

[0086] 2. Aging resistance test: Refer to GB / T16422.3 to test the gloss retention rate and color difference of the sample after 300h of UV aging;

[0087] 3. Neutral salt spray resistance test: The test shall be conducted in accordance with the GB / T 1771 test standard;

[0088] 4. Resistance to nail scratching: The coating was scratched with a nail, and the condition of the coating after scratching was visually inspected. The test results are shown in Table 1:

[0089] Table 1: Effect Test

[0090]

[0091]

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention; those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention; and all technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A process for preparing powder coating for plastic flower pots, characterized in that the steps include... include: The raw materials, including polyester resin, polypropylene resin, curing agent, antioxidant, modified filler, pigment, aluminum powder, and coupling agent, are mixed evenly and then melt-extruded in a twin-screw extruder. The set temperatures are: Zone 1: 80-90℃, Zone 2: 105-115℃, Zone 3: 110-120℃, Zone 4: 100-110℃. The feed screw speed is 20-30 r / min, and the extrusion twin-screw speed is 300-340 r / min. The mixture is then tableted, cooled, and pulverized to a particle size of 10-60 μm, with the 10-30 μm particle size powder comprising 30-40% by weight. The raw materials include the following components by weight: 50-60 parts polyester resin, 20-30 parts polypropylene resin, 8-12 parts curing agent, and antioxidant. The mixture comprises 6-10 parts of oxidant, 15-20 parts of modified filler, 0-10 parts of pigment, 3-5 parts of aluminum powder, and 1-2 parts of coupling agent. The curing agent is triglycidyl isocyanurate. The preparation method of the modified filler includes: adding calcium sulfate and basalt fiber to an ethanol aqueous solution for ultrasonic mixing, heating to 55-65℃, adding a silane coupling agent at a stirring speed of 400-500 r / min, and then continuing to stir for 2-3 hours. After filtration, washing, and drying, the mixture is obtained. The mass concentration of the ethanol aqueous solution is 35-45%, and the weight ratio of calcium sulfate, basalt fiber, ethanol aqueous solution, and silane coupling agent is (2-4):(4-5):(20-24):(0.4-0.8).

2. The preparation process of a powder coating for plastic flower pots according to claim 1, characterized in that, The polyester resin includes a carboxyl-terminated polyester resin with an acid value of 40-60 mgKOH / g and an acid value of 100-140 mgKOH / g, in a weight ratio of (2-3):(6-10).

3. The preparation process of a powder coating for plastic flower pots according to claim 1, characterized in that, The antioxidants include hindered phenolic antioxidants and phosphite antioxidants in a weight ratio of (1-2):(2-3).

4. The preparation process of a powder coating for plastic flower pots according to claim 1, characterized in that, The pigment includes at least one of carbon black and titanium dioxide.

5. The preparation process of a powder coating for plastic flower pots according to claim 1, characterized in that, The coupling agent is a silane coupling agent and an aluminate coupling agent with a weight ratio of 1:(3-4).

6. A powder coating for use on plastic flower pots, prepared using the preparation process described in any one of claims 1-5.

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