A powder coating with a wide range of applications and its preparation method

Abstract

The present application discloses a powder coating with a wide application range and a preparation method thereof, relating to the field of coatings. Among them, the powder coating with a wide application range includes 80 parts by weight of epoxy resin, 40 - 60 parts by weight of maleic anhydride modified hydroxyl-terminated polyester resin, 13 - 22 parts by weight of hydroxyl-terminated methyl vinyl silicone oil, 4 - 8 parts by weight of curing agent, 0.4 - 0.8 parts by weight of curing accelerator, and 0.5 - 4 parts by weight of pigment; the maleic anhydride modified hydroxyl-terminated polyester resin includes maleic anhydride, hydroxyl-terminated polyester resin, p-toluenesulfonic acid and solvent in a weight ratio of (2 - 6):1:(0.1 - 0.2):(10 - 20). The powder coating of the present application can be cured at a lower temperature, broadens the selection of substrates applicable to the powder coating, and the adhesion fastness of the powder coating to glass substrates, metal substrates and wooden substrates is excellent, and it also has excellent weather resistance, alkali resistance and toughness performance.

Description

Technical Field

[0001] The present invention relates to the field of coatings, and particularly to a powder coating with a wide application range and a preparation method thereof. Background Art

[0002] Powder coatings are powder-shaped coatings with 100% solid content, using resin base materials and curing agents as film-forming substances, supplemented with fillers, pigments, and functional additives.

[0003] In the current related technologies, most powder coatings use polyurethane, polyester, or acrylic resin as matrix resins and need to be cured into films under high-temperature baking at 200°C. Such harsh curing conditions greatly limit the selection range of substrates, especially restricting the application of powder coatings on substrates mainly made of wood such as furniture and building templates. In addition, with the continuous development of the economy, people's performance requirements for powder coatings are also getting higher and higher. Based on this, it is of great research significance to develop a powder coating that can be cured at a lower temperature, has a wide application range, and good physical and chemical properties. Summary of the Invention

[0004] In order to improve the problem of limited application of powder coatings in related technologies, the present application provides a powder coating with a wide application range and a preparation method thereof.

[0005] In a first aspect, a powder coating with a wide application range provided by the present application adopts the following technical solution:

[0006] A powder coating with a wide application range, comprising the following raw materials in parts by weight:

[0007] Epoxy resin: 80 parts

[0008] Maleic anhydride-modified hydroxyl-terminated polyester resin: 40 - 60 parts

[0009] Hydroxyl-terminated methyl vinyl silicone oil: 13 - 22 parts

[0010] Curing agent: 4 - 8 parts

[0011] Curing accelerator: 0.4 - 0.8 parts

[0012] Pigment: 0.5 - 4 parts;

[0013] Calculated based on the maleic anhydride-modified hydroxyl-terminated polyester resin, the maleic anhydride-modified hydroxyl-terminated polyester resin comprises raw materials maleic anhydride, hydroxyl-terminated polyester resin, p-toluenesulfonic acid, and a solvent; the weight ratio of maleic anhydride, hydroxyl-terminated polyester resin, p-toluenesulfonic acid, and the solvent is (2 - 6):1:(0.1 - 0.2):(10 - 20);

[0014] Among them, the number-average molecular weight of the hydroxyl-terminated polyester resin is 1000 - 2000 g / mol, and the hydroxyl value is 500 - 600 mg KOH / g.

[0015] In this application, the product obtained by the reaction of epoxy resin, maleic anhydride-modified hydroxyl-terminated polyester resin, and hydroxyl-terminated methyl vinyl silicone oil is used as the film-forming substance. Compared with the conventional polyester resin powder coatings that need to be cured at temperatures above 200°C, due to the lower activation energy of the film-forming substance in this application, the powder coatings of this application can be cured at 140 - 160°C. It is not only applicable to high-temperature-resistant substrates (such as glass, metal substrates, etc.), but also applicable to substrates that are not heat-resistant (such as wood, etc.), effectively broadening the scope of application of powder coatings. At the same time, the coating formed after curing of this powder coating has excellent adhesion fastness to glass substrates, metal substrates, and wooden substrates, and also has excellent weather resistance, alkali resistance, and toughness properties.

[0016] Optionally, the weight ratio of maleic anhydride, hydroxyl-terminated polyester resin, p-toluenesulfonic acid, and solvent is (3.5 - 4.5):1:(0.1 - 0.2):(10 - 20).

[0017] When the weight ratio of maleic anhydride, hydroxyl-terminated polyester resin, p-toluenesulfonic acid, and solvent is in the range of (3.5 - 4.5):1:(0.1 - 0.2):(10 - 20), the weather resistance and alkali resistance of the coating formed by the powder coating can be further improved. And when this powder coating is applied to building aluminum formwork, the powder coating has a good protective effect and demoulding effect on the aluminum formwork. The building aluminum formwork can be recycled more than 50 times, and the coating formed by the powder coating will not fall off.

[0018] Among them, the solvent can be selected as long as it can dissolve the hydroxyl-terminated polyester resin, and N,N-dimethylformamide is preferred.

[0019] Optionally, the epoxy resin includes bisphenol A epoxy resin with an epoxy equivalent of 185 - 195 g / mol and linear aliphatic epoxy resin with an epoxy equivalent of 310 - 330 g / mol, and the weight ratio of the bisphenol A epoxy resin and the linear aliphatic epoxy resin is (3 - 4):1.

[0020] When the epoxy resin is selected as a composition with a specific ratio of bisphenol A epoxy resin with an epoxy equivalent of 185 - 195 g / mol and linear aliphatic epoxy resin with an epoxy equivalent of 310 - 330 g / mol, the powder coating can not only be cured in the range of 140 - 160°C, but also further improve the flexibility of the coating formed by the powder coating.

[0021] Optionally, the linear aliphatic epoxy resin is selected from any one of polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether resin, and polyglycerol diglycidyl ether.

[0022] Optionally, the viscosity of the hydroxyl-terminated methyl vinyl silicone oil is 10 - 20 mm 2 / s, the hydroxyl content is 5.5 - 6.5 wt%, and the vinyl content is 5.5 - 6.5 wt%.

[0023] Controlling the viscosity, hydroxyl content, and vinyl content of the hydroxyl-terminated methyl vinyl silicone oil within the above ranges can not only improve the weather resistance and alkali resistance of the powder coating but also promote the leveling and dispersion performance of the powder coating, which is beneficial to reducing the generation of orange peel problems.

[0024] Optionally, the curing agent includes diisocyanate and isocyanuric acid triglycidyl ester, and the weight ratio of diisocyanate to isocyanuric acid triglycidyl ester is 1:(3 - 4).

[0025] Among them, the diisocyanate is preferably any one of isophorone diisocyanate, tetramethylxylylene diisocyanate, and trimethylhexamethylene diisocyanate.

[0026] Selecting the composition of diisocyanate and isocyanuric acid triglycidyl ester as the curing agent is beneficial to improving the curing efficiency of the powder coating.

[0027] Optionally, the curing accelerator is selected from imidazoles or imidazole derivatives, preferably 2-methylimidazole.

[0028] The addition of the curing accelerator can further improve the curing efficiency of the powder coating.

[0029] Optionally, the pigment is selected from any one or a combination of several of inorganic pigments and organic pigments.

[0030] In the actual application process, different pigments can be added according to requirements to obtain decorative coatings of different colors.

[0031] Among them, the pigment is preferably an inorganic pigment, and the inorganic pigment is preferably any one or a combination of several of aluminum powder, copper powder, carbon black, zinc white, and titanium white.

[0032] Optionally, the powder coating further includes any one or a combination of several of a leveling agent, a weather resistance agent, and an antioxidant agent.

[0033] Second, a preparation method of a powder coating with a wide application range provided by the present application adopts the following technical solution:

[0034] A preparation method of a powder coating with a wide application range includes the following steps:

[0035] Add the hydroxyl-terminated polyester resin into a solvent. After the hydroxyl-terminated polyester resin is dissolved, add maleic anhydride and p-toluenesulfonic acid. Control the reaction temperature at 100 - 120 °C, and heat under reflux until the acid value remains constant. Then cool to obtain the maleic anhydride-modified hydroxyl-terminated polyester resin;

[0036] After uniformly mixing the epoxy resin, maleic anhydride-modified hydroxyl-terminated polyester resin, hydroxyl-terminated methyl vinyl silicone oil and pigment, add a curing agent and a curing accelerator, and continue to mix uniformly to obtain a premix;

[0037] Put the premix into an extruder and extrude and press into sheets at 125 - 150 °C to obtain sheets;

[0038] Crush the sheets, and then pass through a 180-mesh sieve to obtain a powder coating.

[0039] Using the above method to prepare the powder coating not only has the characteristics of simple process and simple equipment requirements, but also is conducive to improving the product stability of the powder coating.

[0040] In summary, the technical solution of this application has at least the following beneficial effects:

[0041] (1) The product obtained by the reaction of the epoxy resin, maleic anhydride-modified hydroxyl-terminated polyester resin and hydroxyl-terminated methyl vinyl silicone oil in this application is used as the film-forming substance. Compared with the conventional polyester resin powder coating that needs to be cured at above 200 °C, since the film-forming substance of this application has a lower activation energy, the powder coating of this application can be cured at 140 - 160 °C. It is not only applicable to high-temperature resistant substrates (such as glass, metal substrates, etc.), but also applicable to substrates that are not resistant to high temperatures (such as wood, etc.), effectively broadening the application range of the powder coating. At the same time, the coating formed after curing of this powder coating has excellent adhesion fastness to glass substrates, metal substrates and wooden substrates, and also has excellent weather resistance, alkali resistance and toughness properties.

[0042] (2) When the weight ratio of maleic anhydride, hydroxyl-terminated polyester resin, p-toluenesulfonic acid and solvent is in the range of (3.5 - 4.5):1:(0.1 - 0.2):(10 - 20), it can further improve the weather resistance and alkali resistance of the coating formed by the powder coating. And when this powder coating is applied to building aluminum formwork, the powder coating has good protection and demoulding effects on the aluminum formwork. The building aluminum formwork can be recycled more than 50 times, and the coating formed by the powder coating will not fall off. Detailed Embodiments

[0043] The following further elaborates on this application in detail with specific experiments.

[0044] Examples

[0045]

Example 1

[0046] A powder coating with a wide range of applications, comprising the following raw materials:

[0047] Epoxy resin: 80 kg, specifically bisphenol A epoxy resin with an epoxy equivalent of 190 g / mol is selected;

[0048] Maleic anhydride modified hydroxyl-terminated polyester resin: 40 kg. Calculated based on the maleic anhydride modified hydroxyl-terminated polyester resin, it includes 2 kg of maleic anhydride, 1 kg of hydroxyl-terminated polyester resin, 0.15 kg of p-toluenesulfonic acid, and 15 kg of N,N-dimethylformamide; the number average molecular weight of the hydroxyl-terminated polyester resin is 1100 g / mol, and the hydroxyl value is 580 mgKOH / g;

[0049] Hydroxyl-terminated methyl vinyl silicone oil: 13 kg. Among them, the viscosity of the hydroxyl-terminated methyl vinyl silicone oil is 18 mm 2 / s, the hydroxyl content is 6.2 wt%, and the vinyl content is 6.4 wt%;

[0050] Curing agent: 4 kg. Calculated based on the curing agent, the curing agent includes isophorone diisocyanate and tris(2,3-epoxypropyl) isocyanurate, and the weight ratio of isophorone diisocyanate to tris(2,3-epoxypropyl) isocyanurate is 1:3;

[0051] Curing accelerator: 0.4 kg, specifically 2-methylimidazole is selected;

[0052] Pigment: 0.5 kg, specifically titanium dioxide is selected.

[0053] In this example, the preparation method of a powder coating with a wide range of applications includes the following steps:

[0054] Add the hydroxyl-terminated polyester resin into N,N-dimethylformamide. After the hydroxyl-terminated polyester resin is dissolved, add maleic anhydride and p-toluenesulfonic acid, control the reaction temperature at 110 °C, heat and reflux until the acid value remains constant, then cool to obtain maleic anhydride modified hydroxyl-terminated polyester resin;

[0055] After uniformly mixing the epoxy resin, maleic anhydride modified hydroxyl-terminated polyester resin, hydroxyl-terminated methyl vinyl silicone oil and pigment, add the curing agent and curing accelerator, and continue to mix uniformly to obtain a premix;

[0056] Put the premix into an extruder, control the temperature of the feeding section at 125 °C, the melting section at 135 °C, the plasticizing section at 140 °C, and the extrusion section at 150 °C, extrude and press into sheets to obtain sheets;

[0057] Crush the sheets, and then pass through a 180-mesh sieve to obtain the powder coating.

[0058]

Example 2

[0059] A powder coating with a wide range of applications, comprising the following raw materials:

[0060] Epoxy resin: 80 kg, specifically bisphenol A epoxy resin with an epoxy equivalent of 190 g / mol is selected;

[0061] Maleic anhydride modified hydroxyl-terminated polyester resin: 50 kg. Calculated based on the maleic anhydride modified hydroxyl-terminated polyester resin, it includes 2 kg of maleic anhydride, 1 kg of hydroxyl-terminated polyester resin, 0.15 kg of p-toluenesulfonic acid, and 15 kg of N,N-dimethylformamide; the number average molecular weight of the hydroxyl-terminated polyester resin is 1100 g / mol, and the hydroxyl value is 580 mgKOH / g;

[0062] Hydroxyl-terminated methyl vinyl silicone oil: 18 kg. Among them, the viscosity of the hydroxyl-terminated methyl vinyl silicone oil is 18 mm 2 / s, the hydroxyl content is 6.2 wt%, and the vinyl content is 6.4 wt%;

[0063] Curing agent: 6 kg. Calculated based on the curing agent, the curing agent includes isophorone diisocyanate and isocyanuric acid trisglycidyl ester, and the weight ratio of isophorone diisocyanate to isocyanuric acid trisglycidyl ester is 1:3;

[0064] Curing accelerator: 0.6 kg, specifically 2-methylimidazole is selected;

[0065] Pigment: 2 kg, specifically titanium dioxide is selected.

[0066] In this example, the preparation method of the powder coating is the same as that in

Example 1

[0067]

Example 3

[0068] A powder coating with a wide range of applications, comprising the following raw materials:

[0069] Epoxy resin: 80 kg, specifically bisphenol A epoxy resin with an epoxy equivalent of 190 g / mol is selected;

[0070] Maleic anhydride modified hydroxyl-terminated polyester resin: 60 kg. Calculated based on the maleic anhydride modified hydroxyl-terminated polyester resin, it includes 2 kg of maleic anhydride, 1 kg of hydroxyl-terminated polyester resin, 0.15 kg of p-toluenesulfonic acid, and 15 kg of N,N-dimethylformamide; the number average molecular weight of the hydroxyl-terminated polyester resin is 1100 g / mol, and the hydroxyl value is 580 mgKOH / g;

[0071] Hydroxyl-terminated methyl vinyl silicone oil: 22 kg. Among them, the viscosity of the hydroxyl-terminated methyl vinyl silicone oil is 18 mm 2 / s, the hydroxyl content is 6.2 wt%, and the vinyl content is 6.4 wt%;

[0072] Curing agent: 8 kg. Calculated based on the curing agent, the curing agent includes isophorone diisocyanate and triglycidyl isocyanurate, and the weight ratio of isophorone diisocyanate to triglycidyl isocyanurate is 1:3;

[0073] Curing accelerator: 0.8 kg, specifically 2-methylimidazole is selected;

[0074] Pigment: 4 kg, specifically titanium dioxide is selected.

[0075] In this example, the preparation method of the powder coating is the same as that in [Example 1].

[0076]

Example 4

[0077] A powder coating with a wide range of applications, different from [Example 2] in that the raw material ratio of the maleic anhydride-modified hydroxyl-terminated polyester resin is different.

[0078] In this example, the maleic anhydride-modified hydroxyl-terminated polyester resin includes 3.5 kg of maleic anhydride, 1 kg of hydroxyl-terminated polyester resin, 0.15 kg of p-toluenesulfonic acid, and 15 kg of N,N-dimethylformamide.

[0079]

Example 5

[0080] A powder coating with a wide range of applications, different from [Example 2] in that the raw material ratio of the maleic anhydride-modified hydroxyl-terminated polyester resin is different.

[0081] In this example, the maleic anhydride-modified hydroxyl-terminated polyester resin includes 4.5 kg of maleic anhydride, 1 kg of hydroxyl-terminated polyester resin, 0.15 kg of p-toluenesulfonic acid, and 15 kg of N,N-dimethylformamide.

[0082]

Example 6

[0083] A powder coating with a wide range of applications, different from [Example 2] in that the raw material ratio of the maleic anhydride-modified hydroxyl-terminated polyester resin is different.

[0084] In this example, the maleic anhydride-modified hydroxyl-terminated polyester resin includes 6 kg of maleic anhydride, 1 kg of hydroxyl-terminated polyester resin, 0.15 kg of p-toluenesulfonic acid, and 15 kg of N,N-dimethylformamide.

[0085]

Example 7

[0086] A powder coating with a wide range of applications, different from [Example 5] in that the epoxy resin composition is different.

[0087] In this embodiment, the epoxy resin includes bisphenol A epoxy resin and polypropylene glycol diglycidyl ether. The epoxy equivalent of the bisphenol A epoxy resin is 190 g / mol, the epoxy equivalent of the polypropylene glycol diglycidyl ether is 320 g / mol, and the weight ratio of the bisphenol A epoxy resin to the polypropylene glycol diglycidyl ether is 3:1.

[0088]

Example 8

[0089] A powder coating with a wide range of applications, which is different from

Example 5

[0090] In this embodiment, the epoxy resin includes bisphenol A epoxy resin and polypropylene glycol diglycidyl ether. The epoxy equivalent of the bisphenol A epoxy resin is 190 g / mol, the epoxy equivalent of the polypropylene glycol diglycidyl ether is 320 g / mol, and the weight ratio of the bisphenol A epoxy resin to the polypropylene glycol diglycidyl ether is 9:1.

[0091] Comparative example

[0092]

Comparative Example 1

[0093] A powder coating, which is different from

Example 2

[0094]

Comparative Example 2

[0095] A powder coating, which is different from

Example 2

[0096]

Comparative Example 3

[0097] A powder coating, which is different from

Example 2

[0098]

Comparative Example 4

[0099] A powder coating, which is different from

Example 2

[0100] In this comparative example, the raw material ratio of the powder coating is as follows:

[0101] Epoxy resin: 50 kg, specifically bisphenol A epoxy resin with an epoxy equivalent of 190 g / mol is selected;

[0102] Maleic anhydride modified hydroxyl-terminated polyester resin: 80 kg. Calculated based on the maleic anhydride modified hydroxyl-terminated polyester resin, the maleic anhydride modified hydroxyl-terminated polyester resin includes 2 kg of maleic anhydride, 1 kg of hydroxyl-terminated polyester resin, 0.15 kg of p-toluenesulfonic acid, and 15 kg of N,N-dimethylformamide; the number average molecular weight of the hydroxyl-terminated polyester resin is 1100 g / mol, and the hydroxyl value is 580 mg KOH / g;

[0103] Hydroxyl-terminated methyl vinyl silicone oil: 30 kg. Among them, the viscosity of the hydroxyl-terminated methyl vinyl silicone oil is 18 mm 2 / s, the hydroxyl content is 6.2 wt%, and the vinyl content is 6.4 wt%;

[0104] Curing agent: 6 kg. Calculated based on the curing agent, the curing agent includes isophorone diisocyanate and tris(2,3-epoxypropyl) isocyanurate, and the weight ratio of isophorone diisocyanate to tris(2,3-epoxypropyl) isocyanurate is 1:3;

[0105] Curing accelerator: 0.6 kg, specifically 2-methylimidazole is selected;

[0106] Pigment: 2 kg, specifically titanium dioxide is selected.

[0107]

Comparative Example 5

[0108] A powder coating, different from

Example 2

[0109] In this example, the maleic anhydride modified hydroxyl-terminated polyester resin includes 1 kg of maleic anhydride, 3 kg of hydroxyl-terminated polyester resin, 0.15 kg of p-toluenesulfonic acid, and 15 kg of N,N-dimethylformamide.

[0110] Performance detection test

[0111] Specimen preparation:

[0112] Specimen group 1: Using the high-voltage electrostatic method, the powder coatings provided in Examples 1-8 and Comparative Examples 1-5 were respectively coated on the surface-cleaned glass substrates with a coating thickness of 80 μm, and then placed in a medium-wave infrared furnace (TRIAB, Sweden). The curing temperature was set at 150 °C, and a curing temperature fluctuation of ±5 °C was considered normal. After curing for 4 min, it was taken out to obtain the glass substrates with cured coatings.

[0113] Specimen group 2: Using the high-voltage electrostatic method, the powder coatings provided in Examples 1-8 and Comparative Examples 1-5 were respectively coated on the surface-cleaned aluminum templates with a coating thickness of 80 μm, and then placed in a medium-wave infrared furnace (TRIAB, Sweden). The curing temperature was set at 150 °C, and a curing temperature fluctuation of ±5 °C was considered normal. After curing for 4 min, it was taken out to obtain the aluminum templates with cured coatings.

[0114] Sample Group 3: The powder coatings provided in Examples 1-8 and Comparative Examples 1-5 were respectively applied to the surface-cleaned pine wood boards by a high-voltage electrostatic method with a coating thickness of 80 μm. The boards were then placed in a medium-wave infrared furnace (TRIAB, Sweden) and the curing temperature was set to 150°C. A curing temperature fluctuation of 5°C was considered normal. The boards were taken out after curing for 4 minutes to obtain cured pine wood boards with coatings.

[0115] 1. Coating surface quality: Visually test the coating condition of each sample in sample groups 1, 2, and 3.

[0116] 2. Adhesion: Referring to GB / T 9286-2021 "Scratch Test Method for Paints and Varnishes", use tape to test the adhesion level of the coating of each sample in sample groups 1, 2, and 3. Among them, the adhesion level is divided into 6 levels: 0, 1, 2, 3, 4, and 5. The lower the level, the better the adhesion stability of the coating.

[0117] 3. Weathering resistance: Refer to GB / T 1865-2009 "Paints and varnishes - Artificial weathering and artificial radiation exposure to filtered xenon arc radiation", use method 1 to test the weathering resistance of each test coating in test group 1, the specific operation is: control the wavelength to 360-400nm, and continuously age for 1000h. Then refer to the peeling area rating method in GB / T1766-2008 "Rating method for aging of paints and varnishes" to rate the weathering resistance of the coating.

[0118] 4. Alkali resistance: Refer to GB / T 9265-2009 "Determination of Alkali Resistance of Architectural Paint Coatings" to test the alkali resistance of each coating in test group 1. Saturated calcium hydroxide is used as the alkaline solution. The immersion time is 72h and the test temperature is 25℃. Then refer to the peeling area rating method in GB / T1766-2008 "Rating method for aging of paint and varnish coatings" to rate the alkali resistance of the coating.

[0119] 5. Flexibility: Using tinplate as the substrate, the powder coatings in Examples 1-8 and Comparative Examples 1-5 were coated on the substrate respectively with a coating thickness of 80 μm, and then placed in a medium-wave infrared furnace (TRIAB, Sweden), and the curing temperature was set to 150°C. After curing for 4 minutes, the tinplate was taken out to obtain a tinplate cured with different coatings. After standing for 48 hours, the flexibility of the coating formed on the tinplate was tested with reference to GB / T 1731-2020 “Determination of flexibility of paint film and putty film”, and the minimum shaft rod diameter at which no reticulation, cracks or peeling was observed was recorded.

[0120] 6. Demoulding property: The concrete demoulding test was carried out using Test Group 2, and the average number of cyclic uses of each formwork in Test Group 2 was calculated when the formwork did not stick and the coating did not peel off.

[0121] Table 1

[0122]

[0123] Table 2

[0124]

[0125] Combined with Examples 1-8 and the data in Tables 1-2, it can be seen that the powder coating in this application is cured at about 150 °C, and a smooth and flat coating surface can be obtained. Moreover, the adhesion fastness of this coating to glass substrates, metal substrates, and wooden substrates is excellent, and it also has excellent weather resistance, alkali resistance, and toughness properties.

[0126] Combined with Example 2 and Comparative Examples 1-5 and the data in Tables 1-2, it can be seen that the powder coating in this application that can be cured at about 150 °C, has a smooth and flat coating surface, excellent adhesion fastness to various materials, and also has weather resistance, alkali resistance, and toughness properties depends on the combination of the components and their ratios claimed in this application.

[0127] Combined with Example 2 and Examples 4-6 and the data in Tables 1-2, when the ratio of maleic anhydride, hydroxyl-terminated polyester resin, p-toluenesulfonic acid, and solvent in the maleic anhydride-modified hydroxyl-terminated polyester resin is in the range of (3.5-4.5):1:(0.1-0.2):(10-20), it can not only further improve the weather resistance and alkali resistance of the coating formed by the powder coating, but also when this powder coating is applied to building aluminum formwork, the protective effect and demoulding effect of the powder coating on the aluminum formwork are good. The building aluminum formwork can be recycled more than 50 times, and the coating formed by the powder coating will not fall off.

[0128] This specific implementation manner is only an explanation of this application, and it is not a limitation of this application. After reading this specification, those skilled in the art can make modifications without creative contributions to this specific implementation manner as needed, but as long as it is within the scope of the claims of this application, it is protected by the patent law.

Claims

1. A powder coating, characterized in that: Comprising the following raw materials in parts by weight: Epoxy resin: 80 parts Maleic anhydride modified hydroxyl-terminated polyester resin: 40 - 60 parts Hydroxyl-terminated methyl vinyl silicone oil: 13 - 22 parts Curing agent: 4 - 8 parts Curing accelerator: 0.4 - 0.8 part Pigment: 0.5 - 4 parts; Based on the maleic anhydride modified hydroxyl-terminated polyester resin, the maleic anhydride modified hydroxyl-terminated polyester resin comprises raw materials maleic anhydride, hydroxyl-terminated polyester resin, p-toluenesulfonic acid and a solvent; the weight ratio of maleic anhydride, hydroxyl-terminated polyester resin, p-toluenesulfonic acid and the solvent is (2 - 6):1:(0.1 - 0.2):(10 - 20); Among them, the number average molecular weight of the hydroxyl-terminated polyester resin is 1000 - 2000 g / mol, and the hydroxyl value is 500 - 600 mgKOH / g; The curing agent comprises diisocyanate and isocyanuric acid triglycidyl ester, and the weight ratio of diisocyanate to isocyanuric acid triglycidyl ester is 1:(3 - 4).

2. The powder coating according to claim 1, wherein: The weight ratio of maleic anhydride, hydroxyl-terminated polyester resin, p-toluenesulfonic acid and the solvent is (3.5 - 4.5):1:(0.1 - 0.2):(10 - 20).

3. A powder coating according to claim 1, characterized in that: The epoxy resin comprises bisphenol A epoxy resin with an epoxy equivalent of 185 - 195 g / mol and linear aliphatic epoxy resin with an epoxy equivalent of 310 - 330 g / mol, and the weight ratio of bisphenol A epoxy resin to linear aliphatic epoxy resin is (3 - 4):

1.

4. A powder coating according to claim 3, characterized in that: The linear aliphatic epoxy resin is selected from any one of polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether resin, and glycerol polyglycidyl ether.

5. A powder coating according to any one of claims 1-4, characterized in that: The viscosity of the hydroxyl-terminated methyl vinyl silicone oil is 10-20 mm 2 / s, the hydroxyl content is 5.5-6.5 wt%, and the vinyl content is 5.5-6.5 wt%.

6. A powder coating according to any one of claims 1-4, characterized in that: The curing accelerator is selected from imidazoles or imidazole derivatives.

7. A powder coating according to any one of claims 1 to 4, characterized in that: The pigment is selected from any one or a combination of several of inorganic pigments and organic pigments.

8. A powder coating according to any one of claims 1 to 4, characterized in that: The powder coating further comprises any one or a combination of leveling aids, weather resistance aids, and antioxidant aids.

9. The preparation method of a powder coating according to any one of claims 1-8, characterized in that: Comprising the following steps: Adding the hydroxyl-terminated polyester resin into a solvent, after the hydroxyl-terminated polyester resin is dissolved, adding maleic anhydride and p-toluenesulfonic acid, controlling the reaction temperature at 100 - 120 °C, heating and refluxing until the acid value remains constant, then cooling to obtain the maleic anhydride modified hydroxyl-terminated polyester resin; After uniformly mixing the epoxy resin, maleic anhydride modified hydroxyl-terminated polyester resin, hydroxyl-terminated methyl vinyl silicone oil and the pigment, adding the curing agent and the curing accelerator, and continuing to mix uniformly to obtain a premix; Putting the premix into an extruder, extruding and pressing into sheets at 125 - 150 °C to obtain sheets; Crushing the sheets, and then passing through a 180-mesh sieve to obtain the powder coating.

Images