Powder coating for plastic flowerpot and preparation process of powder coating

Abstract

The invention provides a powder coating for a plastic flowerpot and a preparation process of the powder coating, and relates to the technical field of coatings. The preparation process comprises the following steps: uniformly mixing the raw materials including the polyester resin, the polypropylene resin, the curing agent, the antioxidant, the modified filler, the pigment, the aluminum powder and the coupling agent, adding the mixture into a double-screw extruder for melt extrusion, tabletting, cooling, and crushing until the particle size is 10-60 [mu] m, and the weight part content of the powder with the particle size of 10-30 [mu] m is 30-40%. According to the invention, the formula of the coating is optimized, and the curing temperature and time of the powder coating are reduced, so that the powder coating can be rapidly cured at a lower temperature, the plastic flowerpot is prevented from being deformed or scorched in the baking process, and the adhesive force of the coating is also effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of coatings, and in particular to a powder coating used on a plastic flower pot and a preparation process thereof. Background Art

[0002] With the rise of modern gardening, plastic flower pots have become the first choice for many families and gardening enthusiasts due to their lightness, durability and affordable price. However, ordinary plastic flower pots are often monotonous in appearance and texture, and it is difficult to meet the needs of modern home decoration. Therefore, it is of great market application value to use powder coating technology to surface treat plastic flower pots to improve their beauty and durability.

[0003] Powder coating is a solid powder mixed with resin, curing agent, filler, pigment, additives, etc. It is applied to the surface of the object by electrostatic spraying and then baked to make it melt, level and solidify into a film. This kind of coating does not contain any organic solvents, has a high utilization rate, and has a simple operation process and high feasibility. It has become an environmentally friendly coating generally recognized 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: high curing temperature, insufficient coating performance and complex process. The curing conditions of conventional powder coatings usually require 10 to 20 minutes of curing at a temperature of 180 to 200 ° C to form a film. The high curing temperature can easily cause the plastic flower pot to deform or burn, limiting the application of powder coatings on plastic flower pots. In addition, after coating, traditional powder coatings have poor adhesion, or it is difficult to achieve ideal coating properties, such as weather resistance and corrosion resistance, which affects the service life and aesthetics of plastic flower pots. The traditional powder coating process is cumbersome and requires multiple spraying and baking, which not only increases production costs, but also reduces production efficiency.

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

[0006] The purpose of the present invention is to provide a powder coating for plastic flower pots and a preparation process thereof, which can be quickly cured at a relatively low temperature and improve the adhesion and weather resistance of the coating.

[0007] On the one hand, the present invention provides a preparation process of powder coating for plastic flower pots, comprising the following steps: uniformly mixing raw materials polyester resin, polypropylene resin, curing agent, antioxidant, modified filler, pigment, aluminum powder and coupling agent, adding the raw materials into a twin-screw extruder for melt extrusion, setting the temperature as follows: zone 1: 80-90°C, zone 2: 105-115°C, zone 3: 110-120°C, zone 4: 100-110°C, feeding screw speed 20-30r / min, extrusion twin screw speed 300-340r / min, then tableting, cooling and crushing to a particle size of 10-60μm, wherein the powder with a particle size of 10-30μm has a weight content of 30-40%.

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

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

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

[0011] Furthermore, the antioxidant comprises a hindered phenol antioxidant and a phosphite antioxidant in a weight ratio of (1-2):(2-3).

[0012] Furthermore, the hindered phenol 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°C, adding a silane coupling agent at a stirring speed of 400-500r / min, then continuing stirring for 2-3h, filtering, washing, and drying to obtain the modified filler.

[0015] Furthermore, 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 wear resistance of coatings. Basalt fiber is a new type of inorganic environmentally friendly green 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 coatings. The compound use of calcium sulfate and basalt fiber can give play to the complementary advantages of the two and further improve the comprehensive performance of the coating. At the same time, due to the modification effect of silane coupling agent, the dispersibility and compatibility of the two in the coating are improved, which helps to quickly solidify the coating and improve its adhesion performance.

[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, which is prepared by using the above-mentioned process for powder coating on plastic flower pots.

[0020] The beneficial effects of the present invention are:

[0021] The powder coating prepared by the present invention can realize low-temperature rapid curing. By optimizing the formula of the coating, the curing temperature and time of the powder coating are reduced, so that the powder coating can be rapidly cured at a relatively low temperature, thereby preventing the plastic flower pot from being deformed or burned during the baking process.

[0022] The present invention uses polyester resin and polypropylene resin as base resin materials. These two resins have good melt fluidity and film-forming properties, can be quickly softened and fused at a relatively low temperature, and provide a basis for the rapid curing of the coating. Triglycidyl isocyanurate is used as a curing agent. This curing agent has efficient cross-linking reaction ability, can chemically react with the resin at a relatively low temperature, form a stable network structure, and thus achieve rapid curing.

[0023] The present invention can adjust the crosslinking density and flexibility of the coating by selecting carboxyl-terminated polyester resins with different acid values ​​for mixing, thereby optimizing the adhesion and weather resistance of the coating.

[0024] The present invention uses calcium sulfate and basalt fiber as modified fillers after treatment, which can enhance the mechanical properties and weather resistance of the coating, and the addition of silane coupling agent further improves the interfacial bonding force between the filler and the resin, thereby improving the adhesion performance of the coating. Calcium sulfate and basalt fiber themselves have good weather resistance and can resist the erosion of natural factors such as ultraviolet rays and oxidation. The addition of these inorganic fillers can enhance the weather resistance of the coating, so that the coating can maintain excellent performance for a long time in an outdoor environment. In addition, the modified filler is subjected to ultrasonic mixing and stirring treatment during the preparation process, so that the filler particles are more evenly dispersed in the resin. Uniform dispersibility is conducive to the coating forming a uniform solidified layer during the curing process, thereby improving the curing speed and curing quality of the coating.

[0025] On this basis, the present invention also uses aluminum powder and modified fillers for compounding. Aluminum powder has a metallic luster and can reflect light, increasing the gloss and brightness of the coating. Aluminum powder interacts with the polymer in the coating to form a protective coating that can prevent erosion by external factors (such as oxygen, water, etc.), thereby improving the adhesion and weather resistance of the coating and promoting the rapid curing of the coating.

[0026] The present invention utilizes the synergistic effect of hindered phenol antioxidants and phosphite antioxidants to effectively capture free radicals generated during the curing and use of the coating, prevent the coating from aging, and thus improve its weather resistance.

[0027] The raw materials of the present invention also use a coupling agent, which is a compound of a silane coupling agent and an aluminate coupling agent. The coupling agent can not only chemically react with the functional groups on the surface of the filler to form a chemical bond, 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 DESCRIPTION

[0028] The technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The present invention is further explained below with examples. In the specific embodiments of the present invention, the model of the polypropylene resin is PP-H GD040, the model of the silane coupling agent is KH560, and the model of the aluminate coupling agent is DL-430. The hindered phenol antioxidant selected in the examples 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 on plastic flower pots, the steps comprising:

[0032] The raw materials polyester resin, polypropylene resin, curing agent, antioxidant, modified filler, pigment, aluminum powder and coupling agent are mixed evenly, added into a twin-screw extruder for melt extrusion, and the temperature is set as follows: zone 1: 85°C, zone 2: 110°C, zone 3: 115°C, zone 4: 105°C, feeding screw speed 25r / min, extrusion twin screw speed 320r / min, and then tableted, cooled, and crushed to a particle size of 10-60μm, wherein the powder weight content of the particle size of 10-30μm is 35%;

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

[0034] The polyester resin includes a carboxyl-terminated polyester resin with an acid value of 50 mgKOH / g and a carboxyl-terminated polyester resin with an acid value of 120 mgKOH / g in a weight ratio of 2.5:8; the curing agent is triglycidyl isocyanurate; the antioxidant includes a hindered phenol antioxidant and a phosphite antioxidant in a weight ratio of 3:5; the pigment is titanium dioxide; the coupling agent includes a silane coupling agent and an aluminate coupling agent in a weight ratio of 1:3.5;

[0035] The preparation method of the modified filler comprises: 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, then continuing stirring for 2.5 hours, filtering, rinsing with deionized water, and drying to obtain the modified filler; the mass concentration of the ethanol aqueous solution is 40%, and the weight ratio of the calcium sulfate and basalt fiber, the ethanol aqueous solution and the silane coupling agent is 3:4.5:22:0.6.

[0036] Test Example 1: First, a layer of WEPE-03 electrostatic paint with a thickness of 30 μm was sprayed on the surface of the plastic sheet to make the product surface conductive, which can absorb the electrostatically sprayed powder coating and increase the adhesion of the powder coating on the product. Then, the powder prepared in Example 1 was sprayed on the plastic sheet by high-voltage electrostatic spraying, and the sprayed plastic sheet was placed in a curing furnace, the curing temperature was adjusted, and the film thickness and hardness were tested. When the curing time was 15 minutes and the curing temperature was adjusted to 130°C, 135°C and 140°C, the film thickness was 140-150 μm, the pencil hardness was 3H, and the adhesion was level 0. Therefore, the coating formula and process provided in Example 1 of the present invention can effectively reduce the curing temperature compared to the common curing temperature of powder coatings such as 180-200°C.

[0037] Example 2

[0038] This embodiment provides a process for applying powder coating on plastic flower pots, the steps comprising:

[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 into a twin-screw extruder for melt extrusion, and the temperature is set as follows: zone 1: 80°C, zone 2: 105°C, zone 3: 110°C, zone 4: 100°C, feeding screw speed 20r / min, extrusion twin screw speed 300r / min, and then tableting, cooling, and crushing to a particle size of 10-60μm, wherein the powder weight content of the particle size of 10-30μm is 30%;

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

[0041] The polyester resin includes a carboxyl-terminated polyester resin with an acid value of 40 mgKOH / g and a carboxyl-terminated polyester resin with an acid value of 100 mgKOH / g in a weight ratio of 1:3; the curing agent is triglycidyl isocyanurate; the antioxidant includes a hindered phenol antioxidant and a phosphite antioxidant in a weight ratio of 1:2; the pigment is titanium dioxide; the coupling agent includes a silane coupling agent and an aluminate coupling agent in a weight ratio of 1:3;

[0042] The preparation method of the modified filler comprises: 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, then continuing stirring for 2 hours, filtering, rinsing with deionized water, and drying to obtain the modified filler; the mass concentration of the ethanol aqueous solution is 35%, and the weight ratio of the calcium sulfate and basalt fiber, the ethanol aqueous solution and the silane coupling agent is 2:4:20:0.4.

[0043] Example 3

[0044] This embodiment provides a process for applying powder coating on plastic flower pots, the steps comprising:

[0045] The raw materials polyester resin, polypropylene resin, curing agent, antioxidant, modified filler, pigment, aluminum powder and coupling agent are mixed evenly, added into a twin-screw extruder for melt extrusion, and the temperature is set as follows: zone 1: 90°C, zone 2: 115°C, zone 3: 120°C, zone 4: 110°C, feeding screw speed 30r / min, extrusion twin screw speed 340r / min, and then tableted, cooled, and crushed to a particle size of 10-60μm, wherein the powder weight content of the particle size of 10-30μm is 40%;

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

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

[0048] The preparation method of the modified filler comprises: 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, then continuing stirring for 3 hours, filtering, rinsing with deionized water, and drying to obtain the modified filler; the mass concentration of the ethanol aqueous solution is 45%, and the weight ratio of the calcium sulfate and basalt fiber, the ethanol aqueous solution and the silane coupling agent is 4:5:24:0.8.

[0049] Example 4

[0050] This embodiment provides a process for applying powder coating on plastic flower pots, the steps comprising:

[0051] The raw materials polyester resin, polypropylene resin, curing agent, antioxidant, modified filler, pigment, aluminum powder and coupling agent are mixed evenly, added into a twin-screw extruder for melt extrusion, and the temperature is set as follows: zone 1: 84°C, zone 2: 108°C, zone 3: 116°C, zone 4: 103°C, feeding screw speed 23r / min, extrusion twin screw speed 310r / min, and then tableted, cooled, and crushed to a particle size of 10-60μm, wherein the powder weight content of the particle size of 10-30μm is 32%;

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

[0053] The polyester resin includes a carboxyl-terminated polyester resin with an acid value of 50 mgKOH / g and a carboxyl-terminated polyester resin with an acid value of 110 mgKOH / g in a weight ratio of 3:8; the curing agent is triglycidyl isocyanurate; the antioxidant includes a hindered phenol antioxidant and a phosphite antioxidant in a weight ratio of 1:3; the pigment is titanium dioxide; the coupling agent includes a silane coupling agent and an aluminate coupling agent in a weight ratio of 1:3;

[0054] The preparation method of the modified filler comprises: 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, then continuing stirring for 2.5 hours, filtering, rinsing with deionized water, and drying to obtain the modified filler; the mass concentration of the ethanol aqueous solution is 42%, and the weight ratio of the calcium sulfate and basalt fiber, the ethanol aqueous solution and the silane coupling agent is 3:4:21:0.5.

[0055] Comparative Example 1

[0056] The comparative example provides a process for powder coating on plastic flower pots, wherein the raw materials polyester resin, polypropylene resin, curing agent, antioxidant, modified filler, pigment, zinc powder and coupling agent are mixed evenly, added into a twin-screw extruder for melt extrusion, and the temperature is set as follows: zone 1: 85°C, zone 2: 110°C, zone 3: 115°C, zone 4: 105°C, feeding screw speed 25r / min, extrusion twin screw speed 320r / min, and then tableting, cooling and crushing to a particle size of 10-60μm, wherein the weight content of the powder with a particle size of 10-30μm is 35%;

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

[0058] The polyester resin includes a carboxyl-terminated polyester resin with an acid value of 50 mgKOH / g and a carboxyl-terminated polyester resin with an acid value of 120 mgKOH / g in a weight ratio of 2.5:8; the curing agent is triglycidyl isocyanurate; the antioxidant includes a hindered phenol antioxidant and a phosphite antioxidant in a weight ratio of 3:5; the pigment is titanium dioxide; the coupling agent includes a silane coupling agent and an aluminate coupling agent in a weight ratio of 1:3.5;

[0059] The preparation method of the modified filler comprises: 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, then continuing stirring for 2.5 hours, filtering, rinsing with deionized water, and drying to obtain the modified filler; the mass concentration of the ethanol aqueous solution is 40%, and the weight ratio of the calcium sulfate and basalt fiber, the ethanol aqueous solution and the silane coupling agent is 3:4.5:22:0.6.

[0060] Comparative Example 2

[0061] The comparative example provides a process for powder coating on plastic flower pots, wherein the raw materials polyester resin, polypropylene resin, curing agent, antioxidant, modified filler, pigment and coupling agent are mixed evenly, added into a twin-screw extruder for melt extrusion, and the temperature is set as follows: zone 1: 85°C, zone 2: 110°C, zone 3: 115°C, zone 4: 105°C, the feeding screw speed is 25r / min, the extrusion twin screw speed is 320r / min, and then the powder is tableted, cooled and crushed to a particle size of 10-60μm, wherein the powder weight content of the particle size of 10-30μm is 35%;

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

[0063] The polyester resin includes a carboxyl-terminated polyester resin with an acid value of 50 mgKOH / g and a carboxyl-terminated polyester resin with an acid value of 120 mgKOH / g in a weight ratio of 2.5:8; the curing agent is triglycidyl isocyanurate; the antioxidant includes a hindered phenol antioxidant and a phosphite antioxidant in a weight ratio of 3:5; the pigment is titanium dioxide; the coupling agent includes a silane coupling agent and an aluminate coupling agent in a weight ratio of 1:3.5;

[0064] The preparation method of the modified filler comprises: 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, then continuing stirring for 2.5 hours, filtering, rinsing with deionized water, and drying to obtain the modified filler; the mass concentration of the ethanol aqueous solution is 40%, and the weight ratio of the calcium sulfate and basalt fiber, the ethanol aqueous solution and the silane coupling agent is 3:4.5:22:0.6.

[0065] Comparative Example 3

[0066] The comparative example provides a process for powder coating on plastic flower pots, wherein the raw materials polyester resin, polypropylene resin, curing agent, antioxidant, modified filler, pigment, aluminum powder and coupling agent are mixed evenly, added into a twin-screw extruder for melt extrusion, and the temperature is set as follows: zone 1: 85°C, zone 2: 110°C, zone 3: 115°C, zone 4: 105°C, feeding screw speed 25r / min, extrusion twin screw speed 320r / min, and then tableting, cooling and crushing to a particle size of 10-60μm, wherein the weight content of the powder with a particle size of 10-30μm is 35%;

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

[0068] The polyester resin includes a carboxyl-terminated polyester resin with an acid value of 50 mgKOH / g and a carboxyl-terminated polyester resin with an acid value of 120 mgKOH / g in a weight ratio of 2.5:8; the curing agent is triglycidyl isocyanurate; the antioxidant includes a hindered phenol antioxidant and a phosphite antioxidant in a weight ratio of 3:5; the pigment is titanium dioxide; the coupling agent includes a silane coupling agent and an aluminate coupling agent in a weight ratio of 1:3.5;

[0069] The preparation method of the modified filler comprises: 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, then continuing stirring for 2.5 hours, filtering, rinsing with deionized water, and drying to obtain the modified filler; the mass concentration of the ethanol aqueous solution is 40%, and the weight ratio of the calcium sulfate and carbon fiber, the ethanol aqueous solution and the silane coupling agent is 3:4.5:22:0.6.

[0070] Comparative Example 4

[0071] The comparative example provides a process for powder coating on plastic flower pots, wherein the raw materials polyester resin, polypropylene resin, curing agent, antioxidant, modified filler, pigment, aluminum powder and coupling agent are mixed evenly, added into a twin-screw extruder for melt extrusion, and the temperature is set as follows: zone 1: 85°C, zone 2: 110°C, zone 3: 115°C, zone 4: 105°C, feeding screw speed 25r / min, extrusion twin screw speed 320r / min, and then tableting, cooling and crushing to a particle size of 10-60μm, wherein the weight content of the powder with a particle size of 10-30μm is 35%;

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

[0073] The polyester resin includes a carboxyl-terminated polyester resin with an acid value of 50 mgKOH / g and a carboxyl-terminated polyester resin with an acid value of 120 mgKOH / g in a weight ratio of 2.5:8; the curing agent is triglycidyl isocyanurate; the antioxidant includes a hindered phenol antioxidant and a phosphite antioxidant in a weight ratio of 3:5; the pigment is titanium dioxide; the coupling agent includes a silane coupling agent and an aluminate coupling agent in a weight ratio of 1:3.5;

[0074] The preparation method of the modified filler comprises: 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, then continuing stirring for 2.5 hours, filtering, rinsing with deionized water, and drying to obtain the modified filler; the mass concentration of the ethanol aqueous solution is 40%, and the weight ratio of the calcium sulfate, the ethanol aqueous solution and the silane coupling agent is 3:4.5:22:0.6.

[0075] Comparative Example 5

[0076] The comparative example provides a process for powder coating on plastic flower pots, wherein the raw materials polyester resin, polypropylene resin, curing agent, antioxidant, modified filler, pigment, aluminum powder and coupling agent are mixed evenly, added into a twin-screw extruder for melt extrusion, and the temperature is set as follows: zone 1: 85°C, zone 2: 110°C, zone 3: 115°C, zone 4: 105°C, feeding screw speed 25r / min, extrusion twin screw speed 320r / min, and then tableting, cooling and crushing to a particle size of 10-60μm, wherein the weight content of the powder with a particle size of 10-30μm is 35%;

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

[0078] The polyester resin includes a carboxyl-terminated polyester resin with an acid value of 50 mgKOH / g and a carboxyl-terminated polyester resin with an acid value of 120 mgKOH / g in a weight ratio of 2.5:8; the curing agent is triglycidyl isocyanurate; the antioxidant includes a hindered phenol antioxidant and a phosphite antioxidant in a weight ratio of 3:5; the pigment is titanium dioxide; the coupling agent includes a silane coupling agent and an aluminate coupling agent in a weight ratio of 1:3.5;

[0079] The preparation method of the modified filler comprises: adding 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, then continuing stirring for 2.5 hours, filtering, rinsing with deionized water, and drying to obtain the modified filler; 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] The comparative example provides a process for powder coating on plastic flower pots, wherein the raw materials polyester resin, polypropylene resin, curing agent, antioxidant, pigment, aluminum powder and coupling agent are mixed evenly, added into a twin-screw extruder for melt extrusion, and the temperature is set as follows: zone 1: 85°C, zone 2: 110°C, zone 3: 115°C, zone 4: 105°C, the feeding screw speed is 25r / min, the extrusion twin screw speed is 320r / min, and then the powder is pressed, cooled and crushed to a particle size of 10-60μm, wherein the powder weight content of the particle size of 10-30μm is 35%;

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

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

[0084] Test Example 2: First, a layer of WEPE-03 electrostatic paint with a thickness of 30 μm is sprayed on the surface of the plastic sheet to make the product surface conductive, so that it can absorb the electrostatically sprayed powder coating and increase the adhesion of the powder coating on the product. Subsequently, the powder coating prepared in the aforementioned Examples 1-4 and Comparative Examples 1-6 is sprayed on the plastic sheet by high-voltage electrostatic spraying. The sprayed plastic sheet is placed in a curing furnace with a curing time of 15 minutes, a curing temperature of 135°C, and a film thickness of 150 μm. The coated plastic sheet sample is tested as follows.

[0085] 1. Adhesion: The test is carried out in accordance with GB / T 9286-2021 standard. The result judgment method is divided into 5 levels: 0: The cutting edge is completely smooth and no grid falls off; 1: A small amount of coating falls off at the intersection of the cuts, but the affected cross-cut area cannot be significantly greater than 5%; 2: The coating falls off at the intersection of the cuts or the edge of the cuts, and the affected cross-cut area is significantly greater than 5% and less than 15%; 3: The coating falls off partially or completely along the cutting edge in large pieces, and partially or completely falls off on different parts of the grid, and the affected cross-cut area is significantly greater than 15% and less than 35%; 4: The coating falls off in large pieces along the cutting edge, and some squares fall off partially or completely, and the affected cross-cut area is significantly greater than 35% and less than 65%; 5: The affected cross-cut area is significantly greater than 65%;

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

[0087] 3. Neutral salt spray resistance test: Tested in accordance with GB / T 1771 test standard;

[0088] 4. Nail scratch resistance: Scratch the coating with your fingernail and visually inspect the scratched coating. 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 the present invention can still be modified or replaced by equivalents. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A process for preparing a powder coating for a plastic flower pot, characterized in that the steps include: The raw materials polyester resin, polypropylene resin, curing agent, antioxidant, modified filler, pigment, aluminum powder and coupling agent are mixed evenly, and then added into a twin-screw extruder for melt extrusion. The temperature is set as follows: zone 1: 80-90°C, zone 2: 105-115°C, zone 3: 110-120°C, zone 4: 100-110°C, feeding screw speed 20-30r / min, extrusion twin screw speed 300-340r / min, and then tableting, cooling and crushing to a particle size of 10-60μm, wherein the weight content of powder with a particle size of 10-30μm is 30-40%.

2. The process for preparing a powder coating for plastic flower pots according to claim 1, characterized in that: The raw materials include the following materials in parts by weight: 50-60 parts of polyester resin, 20-30 parts of polypropylene resin, 8-12 parts of curing agent, 6-10 parts of antioxidant, 15-20 parts of modified filler, 0-10 parts of pigment, 3-5 parts of aluminum powder, and 1-2 parts of coupling agent.

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

4. The process for preparing a powder coating for plastic flower pots according to claim 1, characterized in that: The curing agent is triglycidyl isocyanurate.

5. The process for preparing a powder coating for plastic flower pots according to claim 1, characterized in that: The antioxidant comprises a hindered phenol antioxidant and a phosphite antioxidant in a weight ratio of (1-2):(2-3).

6. The process for preparing a powder coating for plastic flower pots according to claim 1, characterized in that: The preparation method of the modified filler comprises: adding calcium sulfate and basalt fiber into ethanol aqueous solution for ultrasonic mixing, heating to 55-65° C., adding silane coupling agent at a stirring speed of 400-500 r / min, then continuing stirring for 2-3 hours, filtering, washing and drying to obtain the modified filler.

7. The process for preparing a powder coating for plastic flower pots according to claim 6, characterized in that: 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).

8. The process for preparing 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.

9. The process for preparing 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 in a weight ratio of 1:(3-4).

10. A powder coating for plastic flower pots prepared by the preparation process according to any one of claims 1 to 9.

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