Preparation method of high-extinction double-component powder coating

Abstract

The invention relates to the technical field of coatings, in particular to a preparation method of a high-matting double-component powder coating which comprises the following raw materials in parts by mass: 17-25 parts of a powder coating component A, 15-20 parts of a powder coating component B, 18-22 parts of a curing agent, 0.3-0.6 part of pigment, 12-15 parts of filler, 0.1-0.6 part of a degassing agent, 0.4-1.5 parts of a flatting agent and 3-6 parts of a matting agent. The preparation method comprises the following steps: mixing the raw materials, extruding into sheets, grinding and sieving to obtain the high-extinction double-component powder coating. By mixing the high-hydroxyl-value polyester resin and the low-hydroxyl-value polyester resin with different acid values, the powder coating has a good matting effect and also has excellent mechanical properties; and after being modified, the matting agent has good compatibility with the polyester resin, and the dispersity of the matting agent is further improved, so that a better matting effect can be achieved, and compared with the prior art, the matting agent has a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and particularly relates to a preparation method of a high flatting two-component powder coating. Background Art

[0002] In recent years, society has paid increasing attention to issues such as the environment, safety, and energy. To cooperate with the energy conservation and emission reduction of the automotive industry, the development of environmentally friendly automotive coatings and the promotion of clean production of automotive painting processes have become the focus of attention for automotive coating manufacturers and painting enterprises.

[0003] Specifically, automotive decorative parts, especially the exterior parts of high-end automobiles, are currently basically painted with powder coatings. Powder coatings are 100% solid powders that do not contain organic solvents. Different from oil-based coatings and water-based coatings, when painting, they do not use solvents or water as the dispersion medium, but use air as the dispersion medium, and are evenly coated on the surface of the workpiece. After heating, a new type of environmentally friendly coating with special uses is formed. It exists in the form of fine powder and is applied to the surface of the heated substrate by electrostatic spraying technology and melted into a film. Compared with traditional solvent-based coatings, powder coatings have no solvent pollution, are easy to apply, have a fast curing speed, and excellent film properties. It is a high-tech developed since the 1960s.

[0004] Powder coatings have the advantages of being solvent-free, VOC-free, recyclable, environmentally friendly, energy-saving, high construction efficiency, high mechanical strength of the film, and wide application range. With its economic, environmentally friendly, efficient, and excellent performance, it is gradually replacing organic solvent-based coatings and becoming an important development direction in the coating industry, maintaining a relatively fast growth rate, especially being more widely used in the field of metal surface coating. Polyester powder coatings are more widely used in the coating field due to their excellent durability, decorative properties, and processing formability.

[0005] Polyurethane powder coatings are cured with hydroxyl polyester as the main raw material and a curing agent containing -NCO groups. Currently, the most commonly used curing agent for polyurethane powder coatings is the B1530 curing system of Degussa. Although the powder coatings of this system have excellent hardness, leveling property, and scratch resistance, the flatting of this system of powder coatings is relatively difficult, and it is difficult to obtain a low gloss film such as 10% - 20%, which also becomes a problem restricting the wide application of polyurethane powder coatings.

[0006] In order to effectively solve the extinction problem of the compounds in this system, the patent technical literature CN103131308A discloses a high and low acid value two-component polyester resin composition for super weather-resistant dry-mixed extinction powder coatings, which includes a polyester resin for super weather-resistant powder coatings and a low acid value polyester resin for super weather-resistant powder coatings, and also discloses the application of the polyester resin composition; however, the glossiness that can usually be achieved by the extinction system using polyesters with different acid values is in the range of 18-45°, and due to the limitations of the system itself, its glossiness still needs to be further improved.

[0007] Therefore, according to the relevant technologies described above, it is urgent to develop a preparation method for high extinction two-component powder coatings. Summary of the Invention

[0008] In view of this, the purpose of the present invention is to propose a preparation method for high extinction two-component powder coatings to solve the problem of poor extinction in polyester resin powder coatings in the prior art.

[0009] Based on the above purpose, the present invention provides a preparation method for high extinction two-component powder coatings.

[0010] A preparation method for high extinction two-component powder coatings includes the following raw materials in parts by mass:

[0011] 17-25 parts of powder coating component A, 15-20 parts of powder coating component B, 18-22 parts of curing agent, 0.3-0.6 parts of pigment, 12-15 parts of filler, 0.1-0.6 parts of degassing agent, 0.4-1.5 parts of leveling agent, 3-6 parts of extinction agent;

[0012] The powder coating component A is obtained by mixing a high hydroxyl value polyester resin and a modified resin in a mass ratio of 13-15:4-7;

[0013] The powder coating component B is a low hydroxyl value polyester resin;

[0014] The modified resin is prepared from bisphenol A epoxy resin and a silane coupling agent.

[0015] Preferably, the preparation method of the extinction agent is as follows:

[0016] Step A1. Dissolve sodium silicate and hydrochloric acid in deionized water respectively to obtain a sodium silicate solution and a hydrochloric acid solution, dissolve γ-(2,3-epoxypropoxy)propyltrimethoxysilane in absolute ethanol to obtain mixture A, and then dropwise add mixture A and the hydrochloric acid solution into the sodium silicate solution, heat and stir, filter, and spray dry at 130-140 °C to obtain compound A;

[0017] Step A2. Dissolve aminopropyldiethoxysilane in toluene, then add Compound A, stir evenly and centrifuge, wash with toluene three times, and then cure in vacuum to obtain Compound B;

[0018] Step A3. Mix Compound B with bisphenol A epoxy resin to obtain a matting agent.

[0019] Preferably, the dosage ratio of sodium silicate, hydrochloric acid and deionized water in Step A1 is 0.75 - 0.8 g : 0.55 - 0.6 g : 20 - 25 mL;

[0020] The dosage ratio of γ-(2,3-epoxypropoxy)propyltrimethoxysilane to absolute ethanol is 0.1 - 0.2 g : 10 - 15 mL.

[0021] Preferably, the volume ratio of the sodium silicate solution, hydrochloric acid solution to Mixture A in Step A1 is 20 : 20 - 25 : 10 - 15;

[0022] The temperature during heating and stirring is 50 - 60 °C and the time is 4 - 4.5 h.

[0023] Preferably, the dosage ratio of aminopropyldiethoxysilane, toluene and Compound A in Step A2 is 15 - 22 g : 110 - 120 mL : 8 - 10 g;

[0024] The temperature during curing is 140 - 150 °C and the time is 6 - 7 h.

[0025] Preferably, the mass ratio of Compound B to bisphenol A epoxy resin in Step A3 is 25 - 33 : 7 - 12.

[0026] Preferably, the preparation method of the modified resin is as follows:

[0027] Put bisphenol A epoxy resin and dibutyltin dilaurate into a flask equipped with a stirrer, stir evenly at room temperature, then dropwise add isopropenyloxytris(trimethylsilyl)silane, stir for 24 h and then heat to reflux to obtain the modified resin.

[0028] Preferably, the mass ratio of bisphenol A epoxy resin, dibutyltin dilaurate and isopropenyloxytris(trimethylsilyl)silane is 17 - 20 : 1 - 2 : 3.5 - 5;

[0029] The temperature during heating to reflux is 70 - 80 °C and the time is 2 - 2.5 h.

[0030] Preferably, the grade of the high hydroxyl value polyester resin is SJ1800;

[0031] The grade of the low hydroxyl value polyester resin is SJ1100;

[0032] The pigment is carbon black;

[0033] The filler is aluminum hydroxide;

[0034] The degassing agent is benzoin degassing agent;

[0035] The leveling agent is leveling agent GLP588;

[0036] The curing agent is curing agent B1530.

[0037] Preferably, it includes the following steps:

[0038] Add the A component of the powder coating, the B component of the powder coating, the curing agent, the pigment, the filler, the degassing agent, the leveling agent and the matting agent into a mixer and mix evenly, melt and extrude into sheets through a twin-screw extruder, then grind into powder with a grinder, and finally sieve through a 200-mesh sieve to prepare a high-matt two-component powder coating.

[0039] Advantages of the present invention:

[0040] The present invention provides a preparation method of a high-matt two-component powder coating. Through mixing the A component and B component of the powder coating with other additives, extruding into sheets, grinding and sieving, a high-matt two-component powder coating is obtained; through mixing high-hydroxyl-value polyester resin with different acid values and low-hydroxyl-value polyester resin, the powder coating not only has good matt effect but also excellent mechanical properties; and after modification, the matting agent in the powder coating has good compatibility with the polyester resin and its dispersibility is further improved, thus achieving a better matt effect. Compared with the prior art, it has a wide application prospect. Specific embodiments

[0041] To make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments.

[0042] The sources and properties of some raw materials used in the present invention are as follows:

[0043] The curing agent B1530 is purchased from Bayer of Germany; the leveling agent GLP588 is purchased from Ningbo Nanhai Fenghua Co., Ltd.; bisphenol A epoxy resin is purchased from Nan Ya Epoxy Resin Co., Ltd.; carbon black is purchased from Guizhou Qiantu Supply Chain Management Co., Ltd.; aluminum hydroxide is purchased from Luoyang Zhongchao New Materials Co., Ltd.; benzoin degassing agent is purchased from Ningbo Huiwangcheng Plastic Co., Ltd.; low-hydroxyl-value polyester resin SJ1100 is purchased from Anhui Shenjian Co., Ltd.; high-hydroxyl-value polyester resin SJ1800 is purchased from Anhui Shenjian Co., Ltd.

[0044] Example 1: A preparation method of a high-matt two-component powder coating, including the following steps:

[0045] S1. Dissolve 0.75 g of sodium silicate and 0.55 g of hydrochloric acid in 20 mL of deionized water respectively to obtain a sodium silicate solution and a hydrochloric acid solution. Dissolve 0.1 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane in 10 mL of absolute ethanol to obtain mixture A. Then, dropwise add 10 mL of mixture A and 20 mL of hydrochloric acid solution into 20 mL of sodium silicate solution. Heat and stir at 50 °C for 4 h, filter, and then spray-dry at 130 °C to obtain compound A;

[0046] S2. Dissolve 15 g of aminopropyldiethoxysilane in 110 mL of toluene, add 8 g of compound A, stir evenly, centrifuge, and wash with toluene three times. Then cure at 140 °C in vacuum for 6 h to obtain compound B;

[0047] S3. Mix 25 g of compound B with 7 g of bisphenol A epoxy resin to obtain a matting agent;

[0048] S4. Put 20 g of bisphenol A epoxy resin and 2 g of dibutyltin dilaurate into a flask equipped with a stirrer, stir evenly at room temperature, then dropwise add 5 g of isopropenyloxytris(trimethylsilyl)silane, stir for 24 h, and then heat and reflux at 80 °C for 2.5 h to obtain a modified resin. Then mix 7 g of the modified resin with 15 g of a high hydroxyl value polyester resin to obtain component A of the powder coating;

[0049] S5. Add 25 g of component A of the powder coating, 20 g of component B of the powder coating, 22 g of curing agent B1530, 0.6 g of carbon black, 15 g of aluminum hydroxide, 0.6 g of benzoin degassing agent, 1.5 g of leveling agent GLP588, and 6 g of the matting agent into a mixer and mix evenly. Melt and extrude into a sheet through a twin-screw extruder, then grind into powder with a grinder, and finally sieve through a 200-mesh sieve to prepare a high-matting two-component powder coating.

[0050] Example 2: A preparation method of a high-matting two-component powder coating, comprising the following steps:

[0051] S1. Dissolve 0.76 g of sodium silicate and 0.56 g of hydrochloric acid in 21 mL of deionized water respectively to obtain a sodium silicate solution and a hydrochloric acid solution. Dissolve 0.12 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane in 12 mL of absolute ethanol to obtain mixture A. Then, dropwise add 11 mL of mixture A and 21 mL of hydrochloric acid solution into 20 mL of sodium silicate solution. Heat and stir at 52 °C for 4 h, filter, and then spray-dry at 132 °C to obtain compound A;

[0052] S2. Dissolve 17 g of aminopropyldiethoxysilane in 112 mL of toluene, then add 8.5 g of compound A, stir evenly and centrifuge, wash with toluene three times, and then cure at 142 °C in vacuum for 6.5 h to obtain compound B;

[0053] S3. Mix 27 g of compound B with 8 g of bisphenol A epoxy resin to obtain a matting agent;

[0054] S4. Put 17.5 g of bisphenol A epoxy resin and 1.2 g of dibutyltin dilaurate into a flask equipped with a stirrer, stir evenly at room temperature, then dropwise add 3.8 g of isopropenyloxytris(trimethylsilyl)silane, stir for 24 h and then heat reflux at 72 °C for 2 h to obtain a modified resin. Then mix 4.5 g of the modified resin with 13.5 g of a high hydroxyl value polyester resin to obtain component A of the powder coating;

[0055] S5. Add 18 g of component A of the powder coating, 16 g of component B of the powder coating, 19 g of curing agent B1530, 0.35 g of carbon black, 12.55 g of aluminum hydroxide, 0.2 g of benzoin degassing agent, 0.6 g of leveling agent GLP588 and 3.5 g of the matting agent into a mixer and mix evenly. Melt and extrude into sheets through a twin-screw extruder, then grind into powder with a grinder, and finally sieve through a 200-mesh sieve to prepare a high-matting two-component powder coating.

[0056] Example 3: A preparation method of a high-matting two-component powder coating, comprising the following steps:

[0057] S1. Dissolve 0.77 g of sodium silicate and 0.57 g of hydrochloric acid in 22 mL of deionized water respectively to obtain a sodium silicate solution and a hydrochloric acid solution, and dissolve 0.14 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane in 12 mL of absolute ethanol to obtain mixture A. Then dropwise add 12 mL of mixture A and 22 mL of the hydrochloric acid solution into 20 mL of the sodium silicate solution, heat and stir at 54 °C for 4 h, filter, and then spray-dry at 134 °C to obtain compound A;

[0058] S2. Dissolve 17 g of aminopropyldiethoxysilane in 114 mL of toluene, then add 9 g of compound A, stir evenly and centrifuge, wash with toluene three times, and then cure at 144 °C in vacuum for 6 h to obtain compound B;

[0059] S3. Mix 28 g of compound B with 9 g of bisphenol A epoxy resin to obtain a matting agent;

[0060] S4. Put 18 g of bisphenol A epoxy resin and 1.4 g of dibutyltin dilaurate into a flask equipped with a stirrer, stir evenly at room temperature, then add 4.2 g of isopropenyloxytris(trimethylsilyl)silane drop by drop. After stirring for 24 h, heat under reflux at 74 °C for 2 h to obtain a modified resin. Then mix 5 g of the modified resin with 14 g of a high hydroxyl value polyester resin to obtain the A component of the powder coating;

[0061] S5. Put 20 g of the A component of the powder coating, 17 g of the B component of the powder coating, 19.5 g of curing agent B1530, 0.4 g of carbon black, 13 g of aluminum hydroxide, 0.3 g of benzoin degassing agent, 0.8 g of leveling agent GLP588 and 4 g of matting agent into a mixer and mix evenly. Extrude and form into sheets through a twin-screw extruder, then grind into powder with a grinder, and finally sieve through a 200-mesh sieve to prepare a high-matting two-component powder coating.

[0062] Example 4: A preparation method of a high-matting two-component powder coating, comprising the following steps:

[0063] S1. Dissolve 0.78 g of sodium silicate and 0.58 g of hydrochloric acid in 233 mL of deionized water respectively to obtain a sodium silicate solution and a hydrochloric acid solution. Dissolve 0.16 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane in 13 mL of absolute ethanol to obtain mixture A. Then add 13 mL of mixture A and 23 mL of the hydrochloric acid solution drop by drop into 20 mL of the sodium silicate solution. Heat and stir at 56 °C for 4 h, filter, and then spray-dry at 136 °C to obtain compound A;

[0064] S2. Dissolve 19 g of aminopropyldiethoxysilane in 116 mL of toluene, then add 9.5 g of compound A, stir evenly, centrifuge, wash with toluene 3 times, and then cure at 146 °C in vacuo for 6.5 h to obtain compound B;

[0065] S3. Mix 30 g of compound B with 10 g of bisphenol A epoxy resin to obtain a matting agent;

[0066] S4. Put 18.5 g of bisphenol A epoxy resin and 1.6 g of dibutyltin dilaurate into a flask equipped with a stirrer, stir evenly at room temperature, then add 4.5 g of isopropenyloxytris(trimethylsilyl)silane drop by drop. After stirring for 24 h, heat under reflux at 76 °C for 2.5 h to obtain a modified resin. Then mix 5.5 g of the modified resin with 14.5 g of a high hydroxyl value polyester resin to obtain the A component of the powder coating;

[0067] S5. Add 22 g of component A of the powder coating, 18 g of component B of the powder coating, 20 g of curing agent B1530, 0.45 g of carbon black, 13.5 g of aluminum hydroxide, 0.4 g of benzoin degassing agent, 1 g of leveling agent GLP588, and 4.5 g of matting agent into a mixer and mix evenly. Then, melt and extrude into sheets through a twin-screw extruder, grind into powder with a grinder, and finally sieve through a 200-mesh sieve to prepare a high-matting two-component powder coating.

[0068] Example 5: A preparation method of a high-matting two-component powder coating, comprising the following steps:

[0069] S1. Dissolve 0.79 g of sodium silicate and 0.59 g of hydrochloric acid in 24 mL of deionized water respectively to obtain a sodium silicate solution and a hydrochloric acid solution. Dissolve 0.18 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane in 14 mL of absolute ethanol to obtain mixture A. Then, dropwise add 14 mL of mixture A and 24 mL of hydrochloric acid solution into 20 mL of sodium silicate solution, heat and stir at 58 °C for 4.5 h, filter, and then spray-dry at 138 °C to obtain compound A;

[0070] S2. Dissolve 20 g of aminopropyldiethoxysilane in 118 mL of toluene, add 10 g of compound A, stir evenly, centrifuge, wash with toluene three times, and then cure at 148 °C in vacuum for 6.5 h to obtain compound B;

[0071] S3. Mix 31 g of compound B with 11 g of bisphenol A epoxy resin to obtain a matting agent;

[0072] S4. Put 19.5 g of bisphenol A epoxy resin and 1.8 g of dibutyltin dilaurate into a flask equipped with a stirrer, stir evenly at room temperature, then dropwise add 4.8 g of isopropenyloxytris(trimethylsilyl)silane, stir for 24 h, heat and reflux at 78 °C for 2.5 h to obtain a modified resin. Then, mix 6 g of the modified resin with 14.5 g of high-hydroxyl-value polyester resin to obtain component A of the powder coating;

[0073] S5. Add 24 g of component A of the powder coating, 19 g of component B of the powder coating, 21 g of curing agent B1530, 0.5 g of carbon black, 14 g of aluminum hydroxide, 0.5 g of benzoin degassing agent, 1.3 g of leveling agent GLP588, and 5 g of matting agent into a mixer and mix evenly. Then, melt and extrude into sheets through a twin-screw extruder, grind into powder with a grinder, and finally sieve through a 200-mesh sieve to prepare a high-matting two-component powder coating.

[0074] Example 6: A preparation method of a high-matting two-component powder coating, comprising the following steps:

[0075] S1. Dissolve 0.8 g of sodium silicate and 0.6 g of hydrochloric acid in 25 mL of deionized water respectively to obtain a sodium silicate solution and a hydrochloric acid solution. Dissolve 0.2 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane in 15 mL of absolute ethanol to obtain mixture A. Then, dropwise add 115 mL of mixture A and 25 mL of hydrochloric acid solution into 20 mL of sodium silicate solution, heat and stir at 60 °C for 4.5 h, filter, and then spray-dry at 140 °C to obtain compound A;

[0076] S2. Dissolve 22 g of aminopropyldiethoxysilane in 120 mL of toluene, add 10 g of compound A, stir evenly, centrifuge, wash with toluene three times, and then cure at 150 °C in vacuum for 7 h to obtain compound B;

[0077] S3. Mix 33 g of compound B with 12 g of bisphenol A epoxy resin to obtain a matting agent;

[0078] S4. Put 20 g of bisphenol A epoxy resin and 2 g of dibutyltin dilaurate into a flask equipped with a stirrer, stir evenly at room temperature, then dropwise add 5 g of isopropenyloxytris(trimethylsilyl)silane, stir for 24 h, and then heat and reflux at 80 °C for 2.5 h to obtain a modified resin. Then, mix 7 g of the modified resin with 15 g of a high hydroxyl value polyester resin to obtain component A of the powder coating;

[0079] S5. Add 25 g of component A of the powder coating, 20 g of component B of the powder coating, 22 g of curing agent B1530, 0.6 g of carbon black, 15 g of aluminum hydroxide, 0.6 g of benzoin degassing agent, 1.5 g of leveling agent GLP588, and 6 g of matting agent into a mixer and mix evenly. Melt and extrude into a sheet through a twin-screw extruder, then grind into powder with a grinder, and finally sieve through a 200-mesh sieve to prepare a high-matting two-component powder coating.

[0080] Comparative Example 1:

[0081] Compared with Example 1, this comparative example did not add a matting agent during the preparation process of the high-matting two-component powder coating, and the remaining steps and parameters were the same. This comparative example will not be repeated here. Finally, a high-matting two-component powder coating was obtained.

[0082] Comparative Example 2:

[0083] Compared with Example 1, this comparative example did not add bisphenol A epoxy resin during the preparation process of the high-matting two-component powder coating, and the remaining steps and parameters were the same. This comparative example will not be repeated here. Finally, a high-matting two-component powder coating was obtained.

[0084] Comparative Example 3:

[0085] In this comparative example, compared with Example 1, only the "matting agent" was replaced with "silica", and the remaining steps and parameters were the same. This comparative example will not be repeated here, and finally a high-matting two-component powder coating was obtained.

[0086] Comparative Example 4:

[0087] In this comparative example, compared with Example 1, only the "modified resin" was replaced with "bisphenol A epoxy resin", and the remaining steps and parameters were the same. This comparative example will not be repeated here, and finally a high-matting two-component powder coating was obtained.

[0088] Performance test:

[0089] Using an electrostatic spray gun, the high-matting two-component powder coatings prepared in Examples 1 - 6 and Comparative Examples 1 - 4 were respectively sprayed onto the test panels, and then cured and formed in an oven at a temperature of 200°C for 15 minutes, obtaining 10 samples of Examples 1 - 6 and Comparative Examples 1 - 4 respectively;

[0090] Glossiness test:

[0091] Referring to the GB / T9754 measurement standard, using an HP-380 multi-angle glossiness meter, the glossiness of the coating materials of the 10 samples of Examples 1 - 6 and Comparative Examples 1 - 4 was measured at 60° respectively;

[0092] Pencil hardness:

[0093] Referring to the GB / T6739-2006 test standard, the 10 samples of Examples 1 - 6 and Comparative Examples 1 - 4 were respectively placed on a horizontal tabletop. Starting from the hardest pencil (such as 6H), draw lines on the coating at a speed of about 1 cm / s. Each time a line is drawn, the pencil tip needs to be sharpened again. The lines are drawn 5 times for each hardness of the pencil, and observe whether there are scratches or abrasions; if scratches appear two or more times in the five lines, then change to a softer pencil and continue the test until a pencil that cannot scratch the coating at least four times is found, and record the pencil hardness grade;

[0094] Weather resistance:

[0095] Referring to the GB / T1865-2009 test standard, the irradiance settings of the 10 samples of Examples 1 - 6 and Comparative Examples 1 - 4 were set to 1077 W / m 2 ±50 W / m 2 , and the spectral irradiance of the xenon lamp at 300 - 340 nm was 0.35 - 0.4 W / m 2 , and irradiated for 1500 h to obtain the light retention rate of the high-matting two-component powder coating.

[0096] Table 1

[0097] Project Glossiness / ° Pencil hardness Light retention rate / % Example 1 10 3H 93.5 Example 2 8 3H 95.2 Example 3 11 3H 88.9 Example 4 10 3H 89.3 Example 5 8 3H 91.6 Example 6 9 3H 93.4 Comparative Example 1 32 2H 30.6 Comparative Example 2 25 2H 26.5 Comparative Example 3 28 2H 27.8 Comparative Example 4 27 2H 29.2

[0098] Data analysis:

[0099] As can be seen from Table 1, the high-contrast two-component powder coating prepared by the present invention has a better matting effect. This may be because component A of the powder coating is obtained by mixing a high hydroxyl value polyester resin and a modified resin, wherein the modified resin is prepared from bisphenol A epoxy resin and a silane coupling agent. The modified bisphenol A epoxy resin will hydrolyze in the presence of humidity, converting water molecules into alcohol molecules, which can improve the problem that the high hydroxyl value polyester resin is prone to moisture absorption and agglomeration due to too high hydroxyl content, and further improve the mechanical properties of the powder coating; the silica in the matting agent is surface-modified to make it have better dispersibility and compatibility, and the amino groups on the surface can form chemical bonds with the epoxy groups of bisphenol A epoxy resin, which can not only effectively matt the powder coating but also improve the overall mechanical properties of the coating.

[0100] Those of ordinary skill in the art should understand that the discussion of any embodiment above is only exemplary and is not intended to imply that the scope of the present invention is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above, which are not provided in detail for the sake of brevity.

[0101] The present invention aims to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omission, modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a high-contrast two-component powder coating, characterized in that, It includes the following raw materials in parts by mass: 17 - 25 parts of powder coating component A, 15 - 20 parts of powder coating component B, 18 - 22 parts of curing agent, 0.3 - 0.6 parts of pigment, 12 - 15 parts of filler, 0.1 - 0.6 parts of degassing agent, 0.4 - 1.5 parts of leveling agent, 3 - 6 parts of matting agent; The powder coating component A is obtained by mixing high - hydroxyl - value polyester resin and modified resin in a mass ratio of 13 - 15:4 - 7; The powder coating component B is a low - hydroxyl - value polyester resin; The modified resin is prepared from bisphenol A epoxy resin and silane coupling agent; 2. The preparation method of the high matting two-component powder coating according to claim 1, characterized in that, The preparation method of the matting agent is as follows: Step A1. Dissolve sodium silicate and hydrochloric acid in deionized water respectively to obtain a sodium silicate solution and a hydrochloric acid solution, and dissolve γ - (2,3 - epoxypropoxy) propyltrimethoxysilane in absolute ethanol to obtain mixture A. Then, dropwise add mixture A and the hydrochloric acid solution into the sodium silicate solution, heat, stir, filter, and spray - dry at 130 - 140 °C to obtain compound A; Step A2. Dissolve aminopropyldiethoxysilane in toluene, then add compound A, stir evenly, centrifuge, wash with toluene 3 times, and then cure in vacuum to obtain compound B; Step A3. Mix compound B with bisphenol A epoxy resin to obtain the matting agent.

3. The preparation method of the high matting two-component powder coating according to claim 2, characterized in that, In step A1, the dosage ratio of sodium silicate, hydrochloric acid and deionized water is 0.75 - 0.8 g:0.55 - 0.6 g:20 - 25 mL; The dosage ratio of γ - (2,3 - epoxypropoxy) propyltrimethoxysilane to absolute ethanol is 0.1 - 0.2 g:10 - 15 mL.

4. The preparation method of the high-contrast two-component powder coating according to claim 2, characterized in that, In step A1, the volume ratio of the sodium silicate solution, the hydrochloric acid solution and mixture A is 20:20 - 25:10 - 15; The temperature during heating and stirring is 50 - 60 °C and the time is 4 - 4.5 h.

5. The preparation method of the high matting two-component powder coating according to claim 2, characterized in that, In step A2, the dosage ratio of aminopropyldiethoxysilane, toluene and compound A is 15 - 22 g:110 - 120 mL:8 - 10 g; The temperature during curing is 140 - 150 °C and the time is 6 - 7 h.

6. The preparation method of the high matting two-component powder coating according to claim 2, characterized in that, In step A3, the mass ratio of compound B to bisphenol A epoxy resin is 25 - 33:7 - 12.

7. The preparation method of the high-contrast two-component powder coating according to claim 1, characterized in that, The preparation method of the modified resin is as follows: Put bisphenol A epoxy resin and dibutyltin dilaurate into a flask equipped with a stirrer, stir evenly at room temperature, then dropwise add isopropenyloxytris(trimethylsilyl)silane, stir for 24 h, and then heat - reflux to obtain the modified resin.

8. The preparation method of the high matting two-component powder coating according to claim 7, characterized in that, The mass ratio of bisphenol A epoxy resin, dibutyltin dilaurate and isopropenyloxytris(trimethylsilyl)silane is 17 - 20:1 - 2:3.5 - 5; The temperature during heat - reflux is 70 - 80 °C and the time is 2 - 2.5 h.

9. The preparation method of the high matting two-component powder coating according to claim 1, characterized in that, The grade of the high - hydroxyl - value polyester resin is SJ1800; The grade of the low - hydroxyl - value polyester resin is SJ1100; The pigment is carbon black; The filler is aluminum hydroxide; The degassing agent is benzoin degassing agent; The leveling agent is leveling agent GLP588; The curing agent is curing agent B1530.

10. The preparation method of the high matting two-component powder coating according to claim 1, characterized in that, It includes the following steps: Add component A of the powder coating, component B of the powder coating, curing agent, pigment, filler, degassing agent, leveling agent and matting agent into a mixer and mix evenly. Then, melt and extrude into sheets through a twin-screw extruder, and then grind into powder with a grinder. Finally, sieve through a 200-mesh sieve to prepare a high-matting two-component powder coating.