A powder coating, its preparation method and application

Abstract

The present invention relates to a powder coating and its preparation method and application. The powder coating comprises the following components in parts by weight: 50 - 100 parts by weight of a matrix resin, 2 - 25 parts by weight of a curing agent, 0.5 - 8 parts by weight of a composite curing accelerator, and 0.1 - 5 parts by weight of a nano filler; the composite curing accelerator comprises nano rubber particles and a liquid tertiary amine catalyst loaded on the nano rubber particles. The powder coating provided by the present invention applies a more efficient liquid tertiary amine catalyst to a solid powder coating system, expanding the selection range of curing accelerators for powder coatings; and the powder coating has a shorter curing time, a lower curing temperature, and the coating formed after curing has good impact strength, adhesion, solvent resistance, acid resistance, alkali resistance, damp heat resistance, and neutral salt spray resistance, and is suitable for coating heat-sensitive substrates such as wood, engineering plastics, glass, and paper.

Description

Technical Field

[0001] The present invention belongs to the technical field of coating compositions, and particularly relates to a powder coating, a preparation method thereof, and an application thereof. Background Art

[0002] Powder coatings are environmentally friendly solid powder coatings that do not contain any organic solvents. However, powder coatings have the problem of relatively high curing temperatures. Therefore, in recent years, low-temperature curing powder coatings have become a research hotspot in the coating industry. However, under low-temperature curing conditions, the coatings formed after curing of powder coatings have problems such as impact strength, bending strength, and adhesion that cannot meet the performance requirements, which hinders their further application. Therefore, it is of great significance to prepare powder coatings with low curing temperatures and excellent comprehensive properties.

[0003] When preparing low-temperature curing powder coatings in the prior art, the main method is to add highly active resins or curing accelerators. CN116041676A discloses a polyester resin for low-temperature curing powder coatings cured at 160°C and a preparation method thereof. CN115109259A discloses a polyester resin that can be cured at low temperature and a preparation method thereof. However, such highly active low-temperature curing resins are all multi-functional group systems, and the physical and chemical properties such as flexibility of the coatings after low-temperature curing are poor. CN106398482A discloses a low-temperature curing powder coating prepared with 2-phenylimidazoline as a curing accelerator. In order to adapt to the processing method of the low-temperature curing powder coating, the invention uses a solid-state accelerator, and the amount of the curing accelerator added is relatively large and the catalytic efficiency is low.

[0004] In existing low-temperature curing powder coatings, there is generally a low catalytic efficiency of the curing accelerator in the powder coating, and the physical and chemical properties such as impact strength and adhesion of the coatings after curing of the low-temperature curing powder coatings are poor. It is necessary to develop a powder coating with a short curing time, a low curing temperature, and good physical and chemical properties such as impact strength and adhesion of the coating after low-temperature curing. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a powder coating, a preparation method thereof, and an application thereof. By selecting the components of the powder coating and regulating the dosage thereof, the powder coating has a relatively low curing temperature, a short curing time, and excellent physical and chemical properties such as impact strength and adhesion of the coating after low-temperature curing.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a powder coating, which comprises the following components by weight: 50-100 parts by weight of a matrix resin, 2-25 parts by weight of a curing agent, 0.5-8 parts by weight of a composite curing accelerator, and 0.1-5 parts by weight of a nano filler; the composite curing accelerator comprises nano rubber particles and a liquid tertiary amine catalyst supported on the nano rubber particles.

[0008] The powder coating provided by the present invention can fully absorb medium-wave infrared, and the composite curing accelerator in the powder coating can promote the curing of the powder coating, reduce the curing temperature of the powder coating, shorten the curing time, and at the same time improve the flexibility and adhesion of the coating formed after the powder coating is cured; the nano filler can improve the adhesion of the coating formed after the powder coating is cured, and can also regulate the rheology of the powder coating. By adsorbing the liquid tertiary amine catalyst in the composite curing accelerator on the nano rubber particles, the present invention can apply a more efficient liquid tertiary amine catalyst to a solid powder coating system. Through the cooperation of the composite curing accelerator and other components of the powder coating in a specific ratio, the coating formed after the powder coating is cured has good impact strength, adhesion, solvent resistance, acid resistance, alkali resistance, damp heat resistance, and neutral salt spray resistance.

[0009] The matrix resin is 50-100 parts by weight, for example, it can be 50 parts by weight, 55 parts by weight, 60 parts by weight, 65 parts by weight, 70 parts by weight, 75 parts by weight, 80 parts by weight, 85 parts by weight, 90 parts by weight, 95 parts by weight or 100 parts by weight, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0010] The curing agent is 2-25 parts by weight, for example, it can be 2 parts by weight, 4 parts by weight, 6 parts by weight, 8 parts by weight, 10 parts by weight, 12 parts by weight, 14 parts by weight, 16 parts by weight, 18 parts by weight, 20 parts by weight, 22 parts by weight, 24 parts by weight or 25 parts by weight, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0011] The composite curing accelerator is 0.5-8 parts by weight, for example, it can be 0.5 parts by weight, 1 part by weight, 1.5 parts by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight or 8 parts by weight, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0012] The nano filler is 0.1 - 5 parts by weight, for example, it can be 0.1 part by weight, 0.5 part by weight, 1 part by weight, 1.5 parts by weight, 2 parts by weight, 2.5 parts by weight, 3 parts by weight, 3.5 parts by weight, 4 parts by weight, 4.5 parts by weight or 5 parts by weight, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the specific point values included in the scope of the present invention are not exhaustively listed herein.

[0013] The following are the preferred technical solutions of the present invention, but do not limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the objectives and beneficial effects of the present invention can be better achieved and realized.

[0014] As a preferred technical solution, the matrix resin comprises a combination of a first resin and a second resin.

[0015] Preferably, based on the mass of the matrix resin being 100%, the mass of the second resin ≤ 50%, for example, it can be 0, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50%, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the specific point values included in the scope of the present invention are not exhaustively listed herein.

[0016] Preferably, the first resin comprises a combination of a low-viscosity epoxy resin and a high-viscosity epoxy resin.

[0017] In the present invention, the high-viscosity epoxy resin is beneficial to the dispersion of nano rubber particles, and can improve the physical and chemical properties of the coating formed after curing of the powder coating. At the same time, the good dispersion of nano rubber particles can also promote the dispersion of liquid tertiary amine catalysts; the low-viscosity epoxy resin has more reactive functional groups, which can improve the activity of the powder coating and promote the curing of the powder coating.

[0018] Preferably, based on the mass of the first resin being 100%, the mass of the low-viscosity epoxy resin is 10 - 30%, for example, it can be 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28% or 30%, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the specific point values included in the scope of the present invention are not exhaustively listed herein.

[0019] Preferably, the low-viscosity epoxy resin comprises any one or a combination of at least two of a first bisphenol A epoxy resin, a bisphenol F epoxy resin or a linear phenolic epoxy resin.

[0020] Preferably, the high-viscosity epoxy resin comprises a second bisphenol A epoxy resin.

[0021] Preferably, the melt viscosities of the first bisphenol A epoxy resin and the linear phenolic epoxy resin at 150 °C are each independently 300 - 4000 mPa·s, for example, they can be 300 mPa·s, 500 mPa·s, 800 mPa·s, 1000 mPa·s, 1300 mPa·s, 1500 mPa·s, 2000 mPa·s, 2200 mPa·s, 2600 mPa·s, 2800 mPa·s, 3000 mPa·s, 3200 mPa·s, 3400 mPa·s, 3600 mPa·s, 3800 mPa·s or 4000 mPa·s, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0022] Preferably, the melt viscosity of the high-viscosity epoxy resin at 150 °C is 6000 - 13000 mPa·s, for example, it can be 6000 mPa·s, 7000 mPa·s, 8000 mPa·s, 9000 mPa·s, 10000 mPa·s, 11000 mPa·s, 12000 mPa·s or 13000 mPa·s, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0023] Preferably, the second resin includes any one or a combination of at least two of carboxyl polyester resin, hydroxyl polyester resin or carboxyl acrylic resin.

[0024] In the powder coating provided by the present invention, the second resin has a high functional group content, which can play a role in promoting the curing of the powder coating and increasing the crosslinking density.

[0025] Preferably, the acid value of the carboxyl polyester resin is 50 - 70 mg KOH / g, for example, it can be 50 mg KOH / g, 52 mg KOH / g, 54 mg KOH / g, 56 mg KOH / g, 58 mg KOH / g, 60 mg KOH / g, 62 mg KOH / g, 64 mg KOH / g, 66 mg KOH / g, 68 mg KOH / g or 70 mg KOH / g, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0026] Preferably, the hydroxyl value of the hydroxyl polyester resin is 100 - 220 mg KOH / g. For example, it can be 100 mg KOH / g, 110 mg KOH / g, 120 mg KOH / g, 130 mg KOH / g, 140 mg KOH / g, 150 mg KOH / g, 160 mg KOH / g, 170 mg KOH / g, 180 mg KOH / g, 190 mg KOH / g, 200 mg KOH / g, 210 mg KOH / g or 220 mg KOH / g, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0027] Preferably, the acid value of the carboxyl acrylic resin is 140 - 200 mg KOH / g. For example, it can be 140 mg KOH / g, 150 mg KOH / g, 160 mg KOH / g, 170 mg KOH / g, 180 mg KOH / g, 190 mg KOH / g or 200 mg KOH / g, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0028] Preferably, the curing agent includes any one or a combination of at least two of triglycidyl isocyanurate, substituted dicyandiamide, blocked polyisocyanate, dodecanedioic acid, dicarboxylic dihydrazide, acid anhydride, linear phenolic resin, phenolic hydroxyl resin or hydroxyalkylamide.

[0029] Preferably, the nano rubber particles include any one or a combination of at least two of nano acrylonitrile - butadiene powder rubber particles, nano carboxylated acrylonitrile - butadiene powder rubber particles, nano styrene - butadiene - pyridine powder rubber particles or core - shell type nano rubber particles. Further preferably, nano acrylonitrile - butadiene powder rubber particles.

[0030] Preferably, the core - shell type nano rubber particles include butadiene core - shell type rubber particles and / or acrylic core - shell type rubber particles. In the present invention, the core - shell type nano rubber particles are all commercially available products. Exemplarily, the butadiene core - shell type rubber particles can be purchased from Kanena MZ120 of Kaneka Chemical.

[0031] Preferably, the particle size of the nano rubber particles is 50 - 500 nm. For example, it can be 50 nm, 60 nm, 70 nm, 80 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm or 500 nm, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0032] Preferably, the liquid tertiary amine catalyst includes any one or a combination of at least two of straight-chain alkyl tertiary amine, triethanolamine, triethylenediamine, dimethylaminomethylphenol, or tris(dimethylaminomethyl)phenol.

[0033] Preferably, the straight-chain alkyl tertiary amine includes any one or a combination of at least two of dodecyl dimethyl tertiary amine, cetyl dimethyl tertiary amine, tetradecyl dimethyl tertiary amine, or octadecyl dimethyl tertiary amine.

[0034] Preferably, the mass ratio of the nano rubber particles to the liquid tertiary amine catalyst is (4 - 15):1, for example, it can be 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, or 15:1, etc.

[0035] Preferably, the nano filler includes any one or a combination of at least two of nano boehmite, nano cellulose, or nano silica.

[0036] Preferably, the composite curing accelerator is prepared by the following method, which includes: mixing the nano rubber particles and the liquid tertiary amine catalyst, and the liquid tertiary amine catalyst is adsorbed on the nano rubber particles to obtain the composite curing accelerator.

[0037] Preferably, the mixing time is 20 - 60 s, for example, it can be 20 s, 22 s, 24 s, 26 s, 28 s, 30 s, 32 s, 34 s, 36 s, 38 s, 40 s, 44 s, 48 s, 50 s, 52 s, 54 s, 56 s, 58 s, or 60 s, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0038] Preferably, the mixing temperature is 20 - 35 °C, for example, it can be 20 °C, 22 °C, 24 °C, 26 °C, 28 °C, 30 °C, 32 °C, 34 °C, or 35 °C, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0039] Preferably, the powder coating further includes 0.1 - 0.5 parts by weight of a degassing agent, for example, it can be 0.1 part by weight, 0.2 part by weight, 0.3 part by weight, 0.4 part by weight, or 0.5 part by weight, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0040] Preferably, the degassing agent includes benzoin.

[0041] Preferably, the powder coating further comprises 0.2-1 part by weight of a leveling agent, such as 0.2 part by weight, 0.3 part by weight, 0.4 part by weight, 0.5 part by weight, 0.6 part by weight, 0.7 part by weight, 0.8 part by weight, 0.9 part by weight or 1 part by weight, and specific point values between the above point values. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the range.

[0042] Preferably, the leveling agent comprises any one or a combination of at least two of acrylate polymer leveling agents.

[0043] Preferably, the powder coating further comprises 0.1-0.5 part by weight of a pigment, such as 0.1 part by weight, 0.2 part by weight, 0.3 part by weight, 0.4 part by weight or 0.5 part by weight, and specific point values between the above point values. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the range.

[0044] Preferably, the pigment comprises any one or a combination of at least two of rutile titanium dioxide, iron yellow, phthalocyanine blue, phthalocyanine green, iron oxide red or ultramarine blue.

[0045] Preferably, the curing temperature of the powder coating is 125-135 °C.

[0046] Preferably, the curing method of the powder coating comprises infrared curing.

[0047] Preferably, the power of the infrared curing is 5-20 kW / m 2 , such as 5 kW / m 2 , 8 kW / m 2 , 10 kW / m 2 , 12 kW / m 2 , 14 kW / m 2 , 16 kW / m 2 , 18 kW / m 2 or 20 kW / m 2 , and specific point values between the above point values. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the range.

[0048] Preferably, the time of the infrared curing is 3-8 min, such as 3 min, 4 min, 5 min, 6 min, 7 min or 8 min, and specific point values between the above point values. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the range.

[0049] In a second aspect, the present invention provides a method for preparing a powder coating as described in the first aspect, the preparation method comprising: mixing a matrix resin, a curing agent, a composite curing accelerator, and a nano filler, followed by melt extrusion, and then successively performing tablet pressing, cooling, pulverizing, and sieving to obtain the powder coating.

[0050] Preferably, the mixed materials further include a degassing agent, a leveling agent, and a pigment.

[0051] Preferably, the temperature of the melt extrusion is 80 - 110 °C, for example, it can be 80 °C, 85 °C, 88 °C, 90 °C, 95 °C, 98 °C, 100 °C, 102 °C, 105 °C, 108 °C, or 110 °C, as well as specific point values between the above point values. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the range.

[0052] Preferably, by pulverizing to a particle size of 10 - 100 μm (such as 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, or 100 μm, etc.), more preferably 20 - 80 μm (such as 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, or 80 μm, etc.).

[0053] Preferably, the mesh number of the sieve used for sieving is 140 - 200 meshes, for example, it can be 140 meshes, 170 meshes, 180 meshes, or 200 meshes.

[0054] In a third aspect, the present invention provides the use of a powder coating as described in the first aspect for coating a thermosensitive substrate.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] (1) The powder coating provided by the present invention can apply the liquid tertiary amine catalyst of traditional epoxy resin to solid powder coatings, promoting the dispersion of the liquid tertiary amine catalyst and improving the catalytic efficiency of the liquid tertiary amine catalyst, expanding the selection range of curing accelerators for powder coatings;

[0057] (2) The powder coating provided by the present invention has a low curing temperature, a short curing time, and a high surface flatness of the coating after low-temperature curing, without pinholes and shrinkage holes. The curing temperature is 125 - 135 °C. The coating formed after curing has good impact strength, with an impact performance of 100 - 120 cm, an adhesion of grade 0, no loss of gloss and softening phenomenon after 100 times of solvent resistance testing, no blistering and peeling phenomenon after 240 h of acid resistance testing, no blistering and peeling phenomenon after 240 h of alkali resistance testing, no loss of gloss and blistering phenomenon after 1000 h of damp heat resistance testing, and no rust spots and blistering phenomenon after 1000 h of neutral salt spray testing. Detailed Embodiments

[0058] For the convenience of understanding the present invention, the following embodiments are listed. Those skilled in the art should understand that the said embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0059] The sources of some components in the examples and comparative examples are as follows:

[0060] (1) Low-viscosity epoxy resin:

[0061] a. Bisphenol A epoxy resin: HY902 purchased from Anhui Hengyuan, with a melting viscosity of 2000 mPa·s at 150 °C;

[0062] KD-211E purchased from Guodu Chemical Industry, with a melting viscosity of 300 mPa·s at 150 °C;

[0063] b. Linear phenolic epoxy resin: KD-211D and KD-211H purchased from Guodu Chemical Industry, with melting viscosities of 2000 mPa·s and 4000 mPa·s at 150 °C respectively;

[0064] (2) High-viscosity bisphenol A epoxy resin: NPES-904H, NPES-904F and NPES-904HP purchased from Nan Ya, with melting viscosities of 6000 mPa·s, 9000 mPa·s and 13000 mPa·s at 150 °C respectively;

[0065] (3) Carboxyl polyester resin: 1545 purchased from Axalta Coating Systems, with an acid value of 70 mg KOH / g;

[0066] (4) Carboxyl acrylic resin: G152 purchased from, with an acid value of 155 mg KOH / g;

[0067] (5) Hydroxyl polyester resin: P1413 purchased from, with a hydroxyl value of 100 mg KOH / g;

[0068] (6) Nano acrylonitrile-butadiene powder rubber particles: VP401 purchased from Yanshan Petrochemical, with a particle size of 80 - 120 nm;

[0069] (7) Nano carboxyl acrylonitrile-butadiene powder rubber particles: VP501 purchased from Yanshan Petrochemical, with a particle size of 80 - 120 nm;

[0070] (8) Butadiene core-shell rubber particles: kanena MZ120 purchased from Kaneka Corporation, with a particle size of 100 - 200 nm;

[0071] (9) Nano boehmite: purchased from Xuancheng Chengjingrui New Materials Co., Ltd., with a particle size of 10 - 15 nm;

[0072] (10) Nano-silica: Purchased from Xuancheng Jingrui New Materials Co., Ltd., with D50 being 30 nm;

[0073] (11) Leveling agent: GLP588 purchased from Ningbo Nanhai Chemical Co., Ltd.;

[0074] (12) Substituted dicyandiamide: XB2632 purchased from Ciba;

[0075] (13) Blocked polyisocyanate: Degussa EP - BF 1320.

[0076] Preparation Example 1

[0077] A composite curing accelerator A, comprising nano - nitrile powder rubber particles VP401 and cetyl dimethyl tertiary amine loaded thereon. The preparation method of the composite curing accelerator A includes: mixing 7.5 parts by weight of nano - nitrile powder rubber particles VP401 and 0.5 part by weight of cetyl dimethyl tertiary amine in a high - speed mixer at a rotation speed of 24000 r / min for 30 s. Then, the cetyl dimethyl tertiary amine is adsorbed on the nano - nitrile powder rubber particles VP401 to obtain the composite curing accelerator A.

[0078] Preparation Example 2

[0079] A composite curing accelerator B, comprising nano - carboxylated nitrile powder rubber particles VP501 and octadecyl dimethyl tertiary amine loaded thereon. The preparation method of the composite curing accelerator B includes: mixing 4 parts by weight of nano - carboxylated nitrile powder rubber particles VP501 and 1 part by weight of octadecyl dimethyl tertiary amine in a high - speed mixer at a rotation speed of 24000 r / min for 30 s. Then, the octadecyl dimethyl tertiary amine is adsorbed on the nano - carboxylated nitrile powder rubber particles VP501 to obtain the composite curing accelerator B.

[0080] Preparation Example 3

[0081] A composite curing accelerator C, comprising nano - carboxylated nitrile powder rubber particles VP501 and tetradecyl dimethyl tertiary amine loaded thereon. The preparation method of the composite curing accelerator C includes: mixing 12 parts by weight of nano - carboxylated nitrile powder rubber particles VP501 and 1 part by weight of tetradecyl dimethyl tertiary amine in a high - speed mixer at a rotation speed of 24000 r / min for 30 s. Then, the tetradecyl dimethyl tertiary amine is adsorbed on the nano - carboxylated nitrile powder rubber particles VP501 to obtain the composite curing accelerator C.

[0082] Preparation Example 4

[0083] A composite curing accelerator D, comprising nano carboxy nitrile powder rubber particles VP501 and triethanolamine loaded thereon, and the preparation method of the composite curing accelerator D includes: after 10 parts by weight of nano carboxy nitrile powder rubber particles VP501 and 1 part by weight of triethanolamine are mixed at a high speed by a high-speed mixer at a rotation speed of 24000 r / min for 30 s, the triethanolamine is adsorbed on the nano carboxy nitrile powder rubber particles VP501 to obtain the composite curing accelerator D.

[0084] Preparation Example 5

[0085] A composite curing accelerator E, comprising butadiene core-shell rubber particles and cetyl dimethyl tertiary amine loaded thereon, and the preparation method of the composite curing accelerator E includes: after 9 parts by weight of butadiene core-shell rubber particles and 1 part by weight of cetyl dimethyl tertiary amine are mixed at a high speed by a high-speed mixer at a rotation speed of 24000 r / min for 30 s, the cetyl dimethyl tertiary amine is adsorbed on the butadiene core-shell rubber particles to obtain the composite curing accelerator E.

[0086] Preparation Example 6

[0087] A composite curing accelerator F, comprising nano nitrile powder rubber particles VP401 and cetyl dimethyl tertiary amine loaded thereon, and the preparation method of the composite curing accelerator F includes: after 3 parts by weight of nano nitrile powder rubber particles VP401 and 1 part by weight of cetyl dimethyl tertiary amine are mixed at a high speed by a high-speed mixer at a rotation speed of 24000 r / min for 30 s, the cetyl dimethyl tertiary amine is adsorbed on the nano nitrile powder rubber particles VP401 to obtain the composite curing accelerator F.

[0088] Preparation Comparative Example 1

[0089] A composite curing accelerator G, comprising nano carboxy nitrile powder rubber particles VP501 and 2-isopropylimidazole loaded thereon, and the preparation method of the composite curing accelerator G includes: after 12 parts by weight of nano carboxy nitrile powder rubber particles VP501 and 1 part by weight of 2-isopropylimidazole are mixed at a high speed by a high-speed mixer at a rotation speed of 24000 r / min for 30 s, the 2-isopropylimidazole is adsorbed on the nano carboxy nitrile powder rubber particles VP501 to obtain the composite curing accelerator G.

[0090] Preparation Comparative Example 2

[0091] A composite curing accelerator H, and the preparation method of the composite curing accelerator H includes: after 12 parts by weight of nano titanium dioxide and 1 part by weight of tetradecyl dimethyl tertiary amine are mixed at a high speed by a high-speed mixer at a rotation speed of 24000 r / min for 30 s, the composite curing accelerator H is obtained.

[0092] Example 1

[0093] A powder coating, the powder coating comprises the following components by weight: 35 parts by weight of bisphenol A epoxy resin NPES-904HP, 15 parts by weight of bisphenol A epoxy resin HY902, 2 parts by weight of substituted dicyandiamide, 8 parts by weight of composite curing accelerator A, 0.1 part by weight of nano-boehmite, 0.1 part by weight of benzoin, 0.2 part by weight of leveling agent GLP588, and 0.1 part by weight of iron oxide yellow.

[0094] The preparation method of the powder coating includes: mixing the above components, performing twin-screw melt extrusion at 90 °C, followed by pressing, cooling, pulverizing to a particle size of 10-100 μm, and passing through a 180-mesh sieve to obtain the powder coating.

[0095] Example 2

[0096] A powder coating, the powder coating comprises the following components by weight: 35 parts by weight of bisphenol A epoxy resin NPES-904HP, 15 parts by weight of bisphenol A epoxy resin HY902, 30 parts by weight of carboxyl polyester resin, 3 parts by weight of triglycidyl isocyanurate, 0.5 part by weight of composite curing accelerator B, 1 part by weight of nano-boehmite, 0.2 part by weight of benzoin, 0.5 part by weight of leveling agent GLP588, and 0.2 part by weight of iron oxide yellow.

[0097] The difference between the preparation method of the powder coating and that of Example 1 is only that the components of the powder coating are those provided in this example, and other process parameters and steps are the same as those in Example 1.

[0098] Example 3

[0099] A powder coating, the powder coating comprises the following components by weight: 40 parts by weight of bisphenol A epoxy resin NPES-904F, 10 parts by weight of bisphenol A epoxy resin HY902, 50 parts by weight of carboxyl acrylic resin, 1 part by weight of substituted dicyandiamide, 2 parts by weight of triglycidyl isocyanurate, 8 parts by weight of composite curing accelerator C, 3 parts by weight of nano-boehmite, 0.2 part by weight of benzoin, 0.5 part by weight of leveling agent GLP588, and 0.2 part by weight of iron oxide yellow.

[0100] The difference between the preparation method of the powder coating and that of Example 1 is only that the components of the powder coating are those provided in this example, and other process parameters and steps are the same as those in Example 1.

[0101] Example 4

[0102] A powder coating, the powder coating comprises the following components by weight: 45 parts by weight of bisphenol A epoxy resin NPES-904F, 5 parts by weight of linear phenolic epoxy resin KD-211D, 40 parts by weight of hydroxyl polyester resin, 13 parts by weight of phenolic hydroxyl resin, 12 parts by weight of blocked polyisocyanate, 6 parts by weight of composite curing accelerator D, 5 parts by weight of nano-silica, 0.5 part by weight of benzoin, 1 part by weight of leveling agent GLP588, and 0.5 part by weight of iron oxide yellow.

[0103] The preparation method of the powder coating is only different from that of Example 1 in that the components of the powder coating are the components provided in this example, and other process parameters and steps are the same as those in Example 1.

[0104] Example 5

[0105] A powder coating, the powder coating comprises the following components by weight: 40 parts by weight of bisphenol A epoxy resin NPES-904H, 10 parts by weight of linear phenolic epoxy resin KD-211H, 40 parts by weight of hydroxyl polyester resin, 1.5 parts by weight of substituted dicyandiamide, 12 parts by weight of blocked polyisocyanate, 5 parts by weight of composite curing accelerator E, 3 parts by weight of nano-silica, 0.3 part by weight of benzoin, 0.5 part by weight of leveling agent GLP588, and 0.3 part by weight of iron oxide yellow.

[0106] The preparation method of the powder coating is only different from that of Example 1 in that the components of the powder coating are the components provided in this example, and other process parameters and steps are the same as those in Example 1.

[0107] Example 6

[0108] A powder coating and its preparation method, which are only different from Example 3 in that the composite curing accelerator C in this example is 12 parts by weight, and other raw materials, process parameters and steps are the same as those in Example 3.

[0109] Example 7

[0110] A powder coating and its preparation method, which are only different from Example 3 in that bisphenol A epoxy resin NPES-904F in this example is 50 parts by weight and bisphenol A epoxy resin HY902 is not added, and other raw materials, process parameters and steps are the same as those in Example 3.

[0111] Example 8

[0112] A powder coating and its preparation method, which are only different from Example 3 in that the composite curing accelerator C is replaced with the composite curing accelerator F in equal amounts, and other raw materials, process parameters and steps are the same as those in Example 3.

[0113] Comparative Example 1

[0114] A powder coating and its preparation method, the difference from Example 2 is only that the composite curing accelerator B is replaced with the composite curing accelerator G in equal amount, and other raw materials, process parameters and steps are the same as those in Example 2.

[0115] Comparative Example 2

[0116] A powder coating and its preparation method, the difference from Example 3 is only that the composite curing accelerator C is replaced with the composite curing accelerator H in equal amount, and other raw materials, process parameters and steps are the same as those in Example 3.

[0117] Comparative Example 3

[0118] A powder coating, the powder coating comprises the following components by weight: 40 parts by weight of bisphenol A epoxy resin NPES-904F, 10 parts by weight of bisphenol A epoxy resin HY902, 50 parts by weight of carboxyl acrylic resin, 1 part by weight of substituted dicyandiamide, 2 parts by weight of isocyanuric acid trisglycidyl ester, 7.4 parts by weight of nano carboxyl nitrile powder rubber particles VP501, 0.6 part by weight of tetradecyl dimethyl tertiary amine, 3 parts by weight of nano boehmite, 0.2 part by weight of benzoin, 0.5 part by weight of leveling agent GLP588 and 0.2 part by weight of iron oxide yellow.

[0119] The difference between the preparation method of the powder coating and Example 3 is only that the components of the powder coating are the components provided in this comparative example, and other process parameters and steps are the same as those in Example 3.

[0120] The powder coatings provided in Examples 1-8 and Comparative Examples 1-3 were applied to the glass fiber reinforced composite substrate by means of high voltage electrostatic method, and infrared cured and formed, and the curing power was 20 kW / m 2 ; The curing time was 5 min to obtain a coating, and the performance of the coating was tested according to the following method, and the test results are shown in Table 1:

[0121] (1) Use DSC (manufacturer: TA Instruments, model: Q1000) to measure the curing degree and curing temperature of the coating. The specific operation is as follows:

[0122] a. Coating curing degree test: The total heat released when the uncured powder coating is completely cured is ΔH0 (J / g) and the remaining reaction heat when it is not completely cured is ΔH R (J / g) were respectively tested by DSC, and the coating curing degree a = (ΔH0 - ΔH R ) / ΔH0;

[0123] b. Curing temperature: The curing temperature of the powder coating was obtained by non-isothermal heating test of the uncured powder coating by DSC;

[0124] (2) Coating thickness: Tested according to GB / T 1764;

[0125] (3) Adhesion: Tested according to GB / T 9286-2021. A grid pattern is formed by cutting on the coating surface with a cutting tool. The coating cutting edge is completely smooth at level 0; there is a little coating peeling off at the intersection of the cuts, and the affected cross-cutting area is less than 5% at level 1; there is coating peeling off at the intersection of the cuts or along the cutting edge, and the affected cross-cutting area is greater than 5% and less than 15% at level 2;

[0126] (4) Impact resistance: Tested according to GB / T 1732. Record the height at which the heavy hammer falls on the test panel and observe whether there are cracks, peeling, etc. on the coating;

[0127] (5) Solvent resistance: Tested according to GB / T 23989-2009. Wipe with methyl ethyl ketone 100 times and observe whether there is loss of gloss and softening of the coating;

[0128] (6) Acid resistance: Tested according to GB / T 9274-1988. Immerse in 3wt% HCl for 240h and observe whether there are blisters and peeling on the coating;

[0129] (7) Alkali resistance: Tested according to GB / T 9274-1988. Immerse in 5wt% NaOH for 240h and observe whether there are blisters and peeling on the coating;

[0130] (8) Damp heat resistance: Tested according to GB / T 1740-2007. Treat at a temperature of 47°C and a relative humidity of 96% for 1000h and observe whether there is loss of gloss and blistering on the coating;

[0131] (9) Neutral salt spray resistance: Tested according to GB / T 1771-2007. Treat with a sodium chloride aqueous solution with a mass concentration of 50g / L for 1000h and observe whether there are rust spots and blisters on the coating.

[0132] Table 1

[0133]

[0134]

[0135] As can be seen from the test data in Table 1, the powder coating provided by the present invention has a fast curing speed, a relatively low curing temperature, and the cured coating has good impact strength, adhesion, solvent resistance, acid resistance, alkali resistance, damp heat resistance, and neutral salt spray resistance. From the comparison between Example 6 and Example 3, it can be seen that if the addition amount of the composite curing accelerator is too large, the nano-rubber particles will agglomerate, and their dispersibility in the powder coating will deteriorate. Consequently, the dispersibility of the liquid tertiary amine catalyst in the powder coating will also deteriorate, resulting in an increase in the curing temperature of the powder coating, a slowdown in the curing speed, and a deterioration in the impact strength and adhesion of the coating. From the comparison between Example 7 and Example 3, it can be seen that the low-viscosity epoxy resin can improve the activity of the powder coating and promote its curing. Removing the low-viscosity epoxy resin will lead to an increase in the curing temperature of the powder coating, a decrease in the degree of curing, and a deterioration in the solvent resistance, acid resistance, alkali resistance, damp heat resistance, and salt spray resistance of the coating. From the comparison between Example 8 and Example 3, it can be seen that if the mass ratio of the nano-rubber particles to the liquid tertiary amine catalyst is too small, the nano-rubber particles cannot fully adsorb and disperse the liquid tertiary amine catalyst, resulting in an increase in the curing temperature of the powder coating, a slowdown in the curing speed, and a deterioration in the adhesion of the coating.

[0136] From the comparison between Example 2 and Comparative Example 1, it can be seen that the liquid tertiary amine catalyst has a higher catalytic efficiency compared to 2-isopropylimidazole, can effectively shorten the curing time of the powder coating, reduce the curing temperature, and enable the coating formed after curing the powder coating to have excellent physical and chemical properties.

[0137] From the comparison between Example 3 and Comparative Example 2, it can be seen that using nano-rubber particles can adsorb the liquid tertiary amine catalyst on the surface without affecting its performance in the powder coating. However, after replacing it with nano-titanium dioxide, the nano-titanium dioxide has poor adsorption performance for the liquid tertiary amine catalyst, and the liquid tertiary amine catalyst cannot be fully adsorbed and dispersed, resulting in agglomeration of the nano-titanium dioxide and the liquid tertiary amine catalyst with each other, and the catalytic effect cannot be effectively exerted, leading to a deterioration in the coating performance, an increase in the curing temperature of the powder coating, and a slowdown in the curing speed.

[0138] From the comparison between Example 3 and Comparative Example 3, it can be seen that when the nano-rubber particles and the liquid tertiary amine catalyst are directly added and used, the liquid tertiary amine catalyst cannot be evenly dispersed in the powder coating, resulting in an increase in the curing temperature of the powder coating, a slowdown in the curing speed, and a deterioration in the coating performance.

[0139] The applicant declares that the detailed process equipment and process flow of the present invention are illustrated by the above embodiments, but the present invention is not limited to the above detailed process equipment and process flow, that is, it does not mean that the present invention must rely on the above detailed process equipment and process flow to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc. all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A powder coating, characterized in that, The powder coating comprises the following components by weight parts: 50 - 100 parts by weight of matrix resin, 2 - 25 parts by weight of curing agent, 0.5 - 8 parts by weight of composite curing accelerator, and 0.1 - 5 parts by weight of nano filler; The matrix resin comprises a combination of a first resin and a second resin; The first resin comprises a combination of a low-viscosity epoxy resin and a high-viscosity epoxy resin; The low-viscosity epoxy resin comprises any one or a combination of two of a first bisphenol A epoxy resin or a linear phenolic epoxy resin; The melting viscosities of the first bisphenol A epoxy resin and the linear phenolic epoxy resin at 150 °C are independently 300 - 4000 mPa·s; The melting viscosity of the high-viscosity epoxy resin at 150 °C is 6000 - 13000 mPa·s; The second resin comprises any one or a combination of at least two of a carboxyl polyester resin, a hydroxyl polyester resin, or a carboxyl acrylic resin; The acid value of the carboxyl polyester resin is 50 - 70 mg KOH / g; The hydroxyl value of the hydroxyl polyester resin is 100 - 220 mg KOH / g; The acid value of the carboxyl acrylic resin is 140 - 200 mg KOH / g; The composite curing accelerator comprises nano rubber particles and a liquid tertiary amine catalyst supported on the nano rubber particles; The nano rubber particles comprise any one or a combination of at least two of nano acrylonitrile-butadiene powder rubber particles, nano carboxylated acrylonitrile-butadiene powder rubber particles, nano styrene-butadiene-pyridine powder rubber particles, or core-shell type nano rubber particles; The core-shell type nano rubber particles comprise butadiene core-shell rubber particles and / or acrylic core-shell rubber particles; The mass ratio of the nano rubber particles to the liquid tertiary amine catalyst is (4 - 15):

1.

2. The powder coating according to claim 1, characterized in that, Based on the mass of the matrix resin being 100%, the mass of the second resin ≤ 50%.

3. The powder coating according to claim 1, characterized in that, Based on the mass of the first resin being 100%, the mass of the low-viscosity epoxy resin is 10 - 30%.

4. The powder coating according to claim 1, wherein The high-viscosity epoxy resin comprises a second bisphenol A epoxy resin.

5. The powder coating according to claim 1, characterized in that, The curing agent comprises any one or a combination of at least two of isocyanuric acid triglycidyl ester, substituted dicyandiamide, blocked polyisocyanate, dodecanedioic acid, dicarboxylic dihydrazide, acid anhydride, linear phenolic resin, phenolic hydroxyl resin, or hydroxyalkylamide; 6. The powder coating according to claim 1, wherein The nano rubber particles are nano acrylonitrile-butadiene powder rubber particles.

7. The powder coating according to claim 1, characterized in that, The particle size of the nano rubber particles is 50 - 500 nm.

8. The powder coating according to claim 1, characterized in that The liquid tertiary amine catalyst comprises any one or a combination of at least two of a straight-chain alkyl tertiary amine, triethanolamine, triethylenediamine, dimethylaminomethylphenol, or tris(dimethylaminomethyl)phenol; 9. The powder coating according to claim 8, characterized in that, The straight-chain alkyl tertiary amine comprises any one or a combination of at least two of dodecyl dimethyl tertiary amine, hexadecyl dimethyl tertiary amine, tetradecyl dimethyl tertiary amine, or octadecyl dimethyl tertiary amine; 10. The powder coating according to claim 1, wherein The nano filler comprises any one or a combination of at least two of nano boehmite, nano cellulose, or nano silica; 11. The powder coating according to claim 1, characterized in that, The composite curing accelerator is prepared by the following method, which includes: mixing the nano rubber particles and the liquid tertiary amine catalyst, and the liquid tertiary amine catalyst is adsorbed on the nano rubber particles to obtain the composite curing accelerator.

12. The powder coating according to claim 11, characterized in that, The mixing time is 20 - 60 s.

13. The powder coating according to claim 11, characterized in that, The mixing temperature is 20 - 35 °C.

14. The powder coating according to claim 1, characterized in that, The powder coating further includes 0.1 - 0.5 parts by weight of a degassing agent, 0.2 - 1 part by weight of a leveling agent, and 0.1 - 0.5 parts by weight of a pigment according to parts by weight.

15. The powder coating according to claim 14, characterized in that, The degassing agent includes benzoin.

16. The powder coating according to claim 14, wherein The leveling agent includes any one or a combination of at least two of acrylate polymer leveling agents.

17. The powder coating according to claim 14, characterized in that, The pigment includes any one or a combination of at least two of rutile titanium dioxide, iron yellow, phthalocyanine blue, phthalocyanine green, iron oxide red, or ultramarine blue.

18. A method for preparing a powder coating according to any one of claims 1-13, characterized in that, The preparation method includes: mixing the matrix resin, curing agent, composite curing accelerator, and nano filler, followed by melt extrusion, and then successively performing tablet pressing, cooling, crushing, and screening to obtain the powder coating.

19. The preparation method according to claim 18, wherein, The mixed materials further include a degassing agent, a leveling agent, and a pigment.

20. The preparation method according to claim 18, characterized in that, The temperature of the melt extrusion is 80 - 110 °C.

21. The preparation method according to claim 18, characterized in that, Through the crushing, the particle size is 10 - 100 μm.

22. The preparation method according to claim 21, characterized in that, Through the crushing, the particle size is 20 - 80 μm.

23. The preparation method according to claim 18, characterized in that, The mesh number of the sieve for screening is 140 - 200 meshes.

24. A powder coating according to any one of claims 1 - 17 is used for coating a heat-sensitive substrate.

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