An ultra-weatherable powder coating, its preparation method and use

Abstract

This invention discloses an ultra-weather-resistant powder coating, its preparation method, and its application, relating to the technical field of powder coatings. An ultra-weather-resistant powder coating comprises a matrix resin, a curing agent, a leveling agent, a degassing agent, an antioxidant, and pigments and fillers. The matrix resin is a mixture of polyester resin and fluorocarbon resin in a mass ratio of (57-65):(5-8), and the polyester resin is a mixture of ultra-weather-resistant polyester and crystalline polyester in a mass ratio of (50-53):(7-12). By utilizing crystalline polyester in combination with ultra-weather-resistant polyester and fluorocarbon resin as the matrix resin, it is beneficial to balance the relationship between ultra-durability and mechanical properties in the powder coating, thereby enabling the powder coating to possess excellent weather resistance and flexural strength after coating formation.

Description

Technical Field

[0001] This invention relates to the technical field of powder coatings, and in particular to an ultra-weather-resistant powder coating, its preparation method, and its application. Background Technology

[0002] Unlike traditional solvent-based coatings, powder coatings are solid powders that contain neither organic solvents nor water, and are widely used in home appliances, automobiles, office supplies, steel, and construction. Powder coatings are gradually replacing traditional solvent-based coatings due to their advantages such as high inorganic content, no pollution, and energy savings.

[0003] With the advancement of technology and the development of the market, the application of powder coatings has received increasing attention. Powder coatings are divided into two main categories based on their resin base: thermosetting and thermoplastic, with thermosetting powder coatings being the dominant type. Currently, more than half of the thermosetting powder coatings on the market utilize polyester resin as a key component of the base material. Due to the excellent decorative and processability properties of polyester resin, it also dominates the weather-resistant powder coating market and is widely used in outdoor coating applications for buildings and metal components.

[0004] However, with societal development, people are increasingly dissatisfied with the weather resistance of traditional polyester powder coatings. This stems from the fact that the ester bonds in the polyester molecular chain are easily hydrolyzed and gradually powdered under humid and hot conditions. As the overall coating powders, the contained weather-resistant substances are easily lost or decomposed, leading to a decline or even loss of the coating's weather resistance. This further exacerbates the powdering and degradation of the polyester molecular chain, creating a vicious cycle. Traditional weather-resistant polyester powder coatings struggle to cope with increasingly severe environmental challenges, especially failing to meet the stringent requirements of over 20 years of weather resistance for applications such as roofing metal tiles and photovoltaic support components. Furthermore, traditional weather-resistant polyester powder coatings are generally brittle and lack mechanical resilience. When applied to the surface of roofing or factory metal tiles, the coating is prone to whitening and cracking at the bending points during on-site bending, affecting the weather resistance of these areas. Therefore, improving the overall performance of polyester powder coatings is of great significance in order to meet market demands. Summary of the Invention

[0005] To improve the weather resistance and flexural strength of powder coatings, this application provides an ultra-weather-resistant powder coating, its preparation method, and its application.

[0006] Firstly, the ultra-weather-resistant powder coating provided in this application adopts the following technical solution:

[0007] An ultra-weather-resistant powder coating comprises the following raw materials in parts by weight:

[0008] Matrix resin: 65-70 parts;

[0009] 3-3.5 parts of curing agent;

[0010] Leveling agent: 1-1.2 parts;

[0011] Degassing agent: 0.3-0.4 parts;

[0012] Antioxidant: 0.5-0.8 parts;

[0013] Pigments and fillers: 24.5-29.7 parts;

[0014] The matrix resin is a mixture of polyester resin and fluorocarbon resin, and the mass ratio of polyester resin to fluorocarbon resin is (57-65):(5-8). The polyester resin includes ultra-weather-resistant polyester and crystalline polyester, and the mass ratio of ultra-weather-resistant polyester to crystalline polyester is (50-53):(7-12).

[0015] By adopting the above technical solution, using crystalline polyester combined with ultra-weather-resistant polyester and fluorocarbon resin as the matrix resin, more flexible substances can be effectively introduced into the powder coating. This not only retains the excellent weather resistance improvement effect brought about by the introduction of fluorocarbon resin, but also reduces the inhibition of chain segment elongation by fluorocarbon resin. This is conducive to balancing the relationship between ultra-durability and mechanical properties in the powder coating, thereby enabling the powder coating to have excellent weather resistance and bending resistance after the coating is formed.

[0016] Optionally, the ultra-weather-resistant polyester comprises raw materials prepared from the following parts by weight:

[0017] Mixed polyols: 35-40;

[0018] Mixed polyacids: 52-58;

[0019] Branching agent: 4.5-5;

[0020] Esterification catalyst: 0.2-0.3;

[0021] Acidic end-capping agent: 1.8-2.2;

[0022] The mixed polyol is a mixture of ethyl butyl propylene glycol, neopentyl glycol and isosorbide, and the mass ratio of ethyl butyl propylene glycol, neopentyl glycol and isosorbide is 1:(0.5-2):(0.2-0.7);

[0023] The mixed polybasic acid is a mixture of 1,4-cyclohexanedicarboxylic acid, methylene succinic acid and isophthalic acid, and the mass ratio of the 1,4-cyclohexanedicarboxylic acid, the methylene succinic acid and the isophthalic acid is 1:(1-1.5):(4-8);

[0024] The branching agent may be at least one of trihydroxymethyl alkane or lightly branched polyester polyol.

[0025] By adopting the above technical solution, using a specific ratio of ethyl butyl propylene glycol, neopentyl glycol, and isosorbide as mixed polyols, and a specific ratio of 1,4-cyclohexanedicarboxylic acid, methylene succinic acid, and isophthalic acid as mixed polyacids, and adding an appropriate amount of branching agent, it is possible to produce ultra-weather-resistant polyesters with significantly better heat resistance than commercially available products, while other properties are not significantly different. This not only makes powder coatings suitable for prolonged high-temperature environments, expanding their application range, but also helps control the raw material costs of ultra-weather-resistant powder coatings. Furthermore, since the ultra-weather-resistant polyester used is independently developed, it also facilitates subsequent targeted modification of any defects in the powder coating.

[0026] Optionally, the branching agent is specifically a lightly branched polyester polyol, and the hydroxyl content of the lightly branched polyester polyol is 4.3%-5.8%.

[0027] By adopting the above technical solution, when using lightly branched polyester polyols with a hydroxyl content of 4.3%-5.8% as branching agents, compared with traditional trihydroxymethyl alkanes, lightly branched polyester polyols not only have long-chain flexibility, but also dispersed branching points, forming a more uniform crosslinking network. This is beneficial for further balancing the rigidity and flexibility of powder coatings through ultra-weather-resistant polyester, as well as improving the weather resistance and heat resistance of powder coatings.

[0028] Optionally, the preparation method of the ultra-weather-resistant polyester includes the following steps:

[0029] A1. By mass, first add the mixed polyol, branching agent and esterification catalyst into the reaction apparatus, heat to 110-130℃ and stir thoroughly, add the mixed polyacid, and simultaneously introduce inert gas, continue stirring in the inert atmosphere and heat to 180-200℃, wait for the esterification water to start to be generated and stabilized and distilled out, then heat to 225-235℃ and keep the reaction at this temperature for 30-45 minutes;

[0030] A2. When the distilled esterified water reaches 95% of the theoretical value, add an acidic capping agent, then heat to 240-245℃ and continue the reaction for 40-60 minutes.

[0031] A3. When the acid value in the reaction system reaches 35-38 mgKOH / g, vacuum is applied and the reaction is continued for 20-30 minutes. After the reaction is completed, the material is cooled and discharged to obtain an ultra-weather-resistant polyester.

[0032] By adopting the above technical solution, the preparation method is simple and not much different from the traditional polyester synthesis process. Manufacturers can produce directly without adding additional equipment, which helps to reduce the cost of raw material preparation.

[0033] Optionally, the curing agent is β-hydroxyalkylamide, the leveling agent is a silica-adsorbed polyacrylic acid leveling agent, and the degassing agent is benzoin.

[0034] By adopting the above technical solutions, when β-hydroxyalkylamide is used as a curing agent, it can form a dense and stable cross-linked network with the base resin. Moreover, its curing reaction is low-temperature and mild and uniform, which is beneficial to enhancing the weather resistance and chemical stability of the coating film, while avoiding coating defects caused by violent curing reactions and high temperatures. Silica adsorbs polyacrylic acid leveling agents, which can not only improve the dispersibility of the coating, but also effectively reduce the surface tension of the coating film, reduce appearance problems such as orange peel and pinholes, and give the coating film a smooth and even surface. When benzoin is used as a degassing agent, it can promptly eliminate bubbles and pinholes caused by the introduction of fluorocarbon resin during the coating curing process, which helps to ensure the density of the coating film and improve the surface properties of the coating film.

[0035] Optionally, the antioxidant is a mixture of antioxidant 3114 and antioxidant 168, and the mixing ratio of antioxidant 3114 and antioxidant 168 is 1:(0.25-0.6).

[0036] By adopting the above technical solution, antioxidant 3114, as a highly efficient hindered phenolic primary antioxidant, can capture free radicals and terminate the oxidation chain reaction, while antioxidant 168, as a phosphite auxiliary antioxidant, can decompose hydroperoxides and protect the primary antioxidant from oxidation. The combination of the two in a specific ratio exhibits a certain synergistic effect, significantly improving the coating's resistance to thermal and UV oxidation in long-term outdoor environments, delaying gloss loss, discoloration, and chalking caused by oxidation. Furthermore, at this ratio, it does not negatively affect the coating's curing reaction, leveling properties, or compatibility with other additives. This is beneficial for further enhancing the long-term weather resistance stability of ultra-weather-resistant powder coatings while ensuring the mechanical properties and appearance quality of the coating film.

[0037] Optionally, the pigment is a mixture of sericite powder, rutile titanium dioxide and inorganic pigment, and the mass ratio of the sericite powder, the rutile titanium dioxide and the inorganic pigment is (20-24):(3-4):(0.5-1.7).

[0038] By adopting the above technical solutions, the sheet-like structure of sericite can not only extend the penetration path of water vapor, oxygen and corrosive media, but also reflect or scatter ultraviolet rays through the sheet structure, which is conducive to synergistically improving the weather resistance and corrosion resistance of powder coatings; rutile titanium dioxide can improve the hiding power of the paint film and improve the color retention rate of inorganic pigments; inorganic pigments have the characteristics of being sun-resistant, heat-resistant, weather-resistant and having strong hiding power. When the weight ratio of sericite powder, rutile titanium dioxide and inorganic pigments is (20-24):(3-4):(0.5-1.7), it is conducive to forming a paint film with uniform color and high color retention rate in powder coatings.

[0039] Secondly, the preparation method of the ultra-weather-resistant powder coating provided in this application adopts the following technical solution:

[0040] A method for preparing an ultra-weather-resistant powder coating includes the following steps:

[0041] By weight, the base resin is heated to 120-130℃ and stirred and mixed. After the mixture is uniform, the curing agent, leveling agent, degassing agent, antioxidant and pigments and fillers are added. After the raw materials are mixed evenly, the mixture is transferred to a screw extruder and melt-extruded, pressed, crushed and screened at 145-160℃ to obtain an ultra-weather-resistant powder coating.

[0042] By adopting the above technical solution, the preparation of powder coatings has the characteristics of simple steps and convenient operation, and at the same time, it is conducive to the full mixing of the matrix resin, so that the coating formed by the powder coating can be cured uniformly.

[0043] Thirdly, the application of the ultra-weather-resistant powder coating provided in this application adopts the following technical solution:

[0044] An application of an ultra-weather-resistant powder coating, suitable for surface protection coating of metal tiles or outdoor metal components for roofing or factory use.

[0045] By adopting the above technical solution, a weather-resistant protective layer can be effectively formed on the surface of metal tiles or outdoor metal components, which helps prevent aging or repair of metal tiles or outdoor metal components due to external environmental factors, and helps to improve the service life of metal tiles or outdoor metal components. Secondly, when the powder coating prepared above is applied to metal tile panels, the coating at the bending part is not prone to whitening and cracking during the bending process of the metal plate, and can completely maintain the weather resistance of the bending part.

[0046] In summary, the technical solution of this application has at least one of the following beneficial effects:

[0047] 1. By using crystalline polyester in combination with ultra-weather-resistant polyester and fluorocarbon resin as the matrix resin, it is beneficial to balance the relationship between ultra-durability and mechanical properties in powder coatings, thereby enabling the powder coating to have excellent weather resistance and bending resistance after coating formation.

[0048] 2. By utilizing a specific ratio of mixed polyols, a specific ratio of mixed polyacids, and an appropriate amount of branching agent, it is possible to produce ultra-weather-resistant polyester with significantly better heat resistance and other properties close to those of existing products. This makes the resulting powder coating suitable for long-term high-temperature environments, thus expanding the application scenarios of powder coatings.

[0049] 3. When using self-made ultra-weather-resistant polyester to prepare powder coatings, it is not only beneficial to control the raw material cost of ultra-weather-resistant powder coatings, but also beneficial to subsequently modify the defects of powder coatings.

[0050] 4. When using a lightly branched polyester polyol with a hydroxyl content of 4.3%-5.8% as a branching agent for ultra-weather-resistant polyester, it is beneficial to further balance the relationship between the rigidity and flexibility of the powder coating through ultra-weather-resistant polyester, and improve the weather resistance and heat resistance of the powder coating. Detailed Implementation

[0051] The present application will be further described in detail below with reference to preparation examples, embodiments and comparative examples.

[0052] The lightly branched polyester polyols were purchased from Zhanxin Resin, specifically the grades SETAL 168 and SETAL 166, with SETAL 168 having a hydroxyl content of 4.3% and SETAL 166 having a hydroxyl content of 5.8%.

[0053] The ultra-weather-resistant polyester resin was purchased from Qingtian Materials, specifically grade NH6585.

[0054] The fluorocarbon resin was purchased from Shandong Huafu Chemical Co., Ltd., specifically the FEVE powder resin, brand name HLR-P, with a hydroxyl value of 50-70 mg KOH / g.

[0055] The crystalline polyester was selected from Covestro's weather-resistant crystalline polyester, specifically the brand name Uralac P9000.

[0056] The leveling agent was selected from Changming New Materials' silica-adsorbed polyacrylic acid leveling agent, specifically brand CM506.

[0057] All antioxidants were purchased from Tianjin Lialong.

[0058] Preparation Example

[0059]

Preparation Example 1

[0060] An ultra-weather-resistant polyester comprises the following raw materials: 35 kg of mixed polyols, 58 kg of mixed polyacids, 5 kg of branching agent, 0.2 kg of esterification catalyst, and 1.8 kg of acidic end-capping agent.

[0061] The mixed polyols are a mixture of ethyl butyl propylene glycol, neopentyl glycol, and isosorbide in a mass ratio of 1:1:0.5, comprising 14 kg of ethyl butyl propylene glycol, 14 kg of neopentyl glycol, and 7 kg of isosorbide. The mixed polyacids are a mixture of 1,4-cyclohexanedicarboxylic acid, methylene succinic acid, and isophthalic acid in a mass ratio of 1:1.5:2.5, comprising 11.6 kg of 1,4-cyclohexanedicarboxylic acid, 17.4 kg of methylene succinic acid, and 29 kg of isophthalic acid.

[0062] Specifically, the branching agent is a lightly branched polyester polyol of brand name SETAL 168; the esterification catalyst is monobutyltin oxide; and the acidic end-capping agent is a long-chain fatty acid, specifically sebacic acid.

[0063] A method for preparing an ultra-weather-resistant polyester includes the following steps:

[0064] A1. By mass, first put the mixed polyol, branching agent and esterification catalyst into the reaction device, heat to 110°C and stir and mix thoroughly, add the mixed polyacid, and simultaneously introduce nitrogen gas, continue stirring in the nitrogen atmosphere and heat to 200°C, wait for the esterification water to start to be generated and stabilized and distilled out, then heat to 235°C and keep the reaction at this temperature for 30 min.

[0065] A2. When the distilled esterified water reaches 95% of the theoretical value, add an acidic capping agent, then heat to 245℃ and continue the reaction for 40 minutes;

[0066] A3. When the acid value in the reaction system reaches the range of 35-38 mgKOH / g, evacuate to a vacuum degree of less than 20 mmHg, and continue to keep the reaction at the temperature for 20 min. After the reaction is completed, cool and discharge the material to obtain an ultra-weather-resistant polyester.

[0067]

Preparation Example 2

[0068] An ultra-weather-resistant polyester comprises the following raw materials: 40 kg of mixed polyols, 54 kg of mixed polyacids, 3.5 kg of branching agent, 0.3 kg of esterification catalyst, and 2.2 kg of acidic end-capping agent.

[0069] The mixed polyols are a mixture of ethyl butyl propylene glycol, neopentyl glycol, and isosorbide in a mass ratio of 1:2:0.2, comprising 12.5 kg of ethyl butyl propylene glycol, 25 kg of neopentyl glycol, and 2.5 kg of isosorbide. The mixed polyacids are a mixture of 1,4-cyclohexanedicarboxylic acid, methylene succinic acid, and isophthalic acid in a mass ratio of 1:1:7, comprising 6 kg of 1,4-cyclohexanedicarboxylic acid, 6 kg of methylene succinic acid, and 42 kg of isophthalic acid.

[0070] Specifically, the branching agent is trihydroxymethylpropane; the esterification catalyst is monobutyltin oxide; and the acidic end-capping agent is a long-chain fatty acid, specifically sebacic acid.

[0071] A method for preparing an ultra-weather-resistant polyester includes the following steps:

[0072] A1. By mass, first put the mixed polyol, branching agent and esterification catalyst into the reaction device, heat to 120°C and stir thoroughly, add the mixed polyacid, and simultaneously introduce nitrogen gas, continue stirring in the nitrogen atmosphere and heat to 180°C, wait for the esterification water to start to be generated and stabilized and distilled out, then heat to 225°C and keep the reaction at this temperature for 45 minutes.

[0073] A2. When the distilled esterified water reaches 95% of the theoretical value, add an acidic capping agent, then heat to 240℃ and continue the reaction for 60 minutes;

[0074] A3. When the acid value in the reaction system reaches the range of 35-38 mgKOH / g, evacuate to a vacuum degree of less than 20 mmHg, and continue to keep the reaction at a constant temperature for 30 minutes. After the reaction is completed, cool and discharge the material to obtain an ultra-weather-resistant polyester.

[0075]

Preparation Example 3

[0076] An ultra-weather-resistant polyester differs from [Preparation Example 2] in that it uses a different blend of polyols.

[0077] In this preparation example, the mixed polyol is a mixture of ethyl butyl propylene glycol, neopentyl glycol and isosorbide in a mass ratio of 1:1.5:0.7, that is, including 12.5 kg of ethyl butyl propylene glycol, 18.75 kg of neopentyl glycol and 8.75 kg of isosorbide.

[0078]

Preparation Example 4

[0079] An ultra-weather-resistant polyester differs from [Preparation Example 2] in that it uses a different blend of polyols.

[0080] In this preparation example, the mixed polyol is a mixture of ethyl butyl propylene glycol, neopentyl glycol and isosorbide in a mass ratio of 1:1.2:1, that is, including 12.5 kg of ethyl butyl propylene glycol, 15 kg of neopentyl glycol and 12.5 kg of isosorbide.

[0081]

Preparation Example 5

[0082] An ultra-weather-resistant polyester, which differs from [Preparation Example 2] in that isosorbide is not added to the mixed polyol.

[0083] In this preparation example, isosorbide is replaced by an equal amount of ethyl butyl propylene glycol. Specifically, the mixed polyols include 15 kg of ethyl butyl propylene glycol and 25 kg of neopentyl glycol.

[0084]

Preparation Example 6

[0085] A super weather-resistant polyester, which differs from [Preparation Example 3] in that it contains different mixed polybasic acids.

[0086] In this preparation example, the mixed polybasic acid is 1,4-cyclohexanedicarboxylic acid, methylene succinic acid and isophthalic acid mixed in a mass ratio of 1:1:4, that is, including 9 kg of 1,4-cyclohexanedicarboxylic acid, 9 kg of methylene succinic acid and 36 kg of isophthalic acid.

[0087]

Preparation Example 7

[0088] A super weather-resistant polyester, which differs from [Preparation Example 3] in that it uses a different branching agent.

[0089] In this preparation example, the branching agent is specifically selected as a lightly branched polyester polyol with the brand name SETAL 168.

[0090]

Preparation Example 8

[0091] A super weather-resistant polyester, which differs from [Preparation Example 3] in that it uses a different branching agent.

[0092] In this preparation example, the branching agent is specifically selected as a lightly branched polyester polyol with the brand name SETAL 166.

[0093]

Preparation Example 9

[0094] An ultra-weather-resistant polyester, which differs from [Preparation Example 3] in that it does not contain a branching agent.

[0095] In this preparation example, ethyl butyl propylene glycol is used to replace the branching agent in equal amounts. The specific mixed polyols include 16 kg of ethyl butyl propylene glycol, 25 kg of neopentyl glycol, and 2.5 kg of isosorbide.

[0096] Example

[0097]

Example 1

[0098] An ultra-weather-resistant powder coating comprises the following raw materials: 70 kg of matrix resin, 3.6 kg of curing agent, 1 kg of leveling agent, 0.4 kg of degassing agent, 0.5 kg of antioxidant, and 24.5 kg of pigments and fillers.

[0099] In this embodiment, the matrix resin is a mixture of polyester resin and fluorocarbon resin in a mass ratio of 65:5. The polyester resin includes ultra-weather-resistant polyester and crystalline polyester, with a mass ratio of ultra-weather-resistant polyester to crystalline polyester of 53:12. That is, the matrix resin comprises 53 kg of ultra-weather-resistant polyester, 12 kg of crystalline polyester, and 5 kg of fluorocarbon resin. Specifically, the ultra-weather-resistant polyester is commercially available NH6585, the crystalline polyester is commercially available Uralac P9000, and the fluorocarbon resin is commercially available HLR-1.

[0100] In this embodiment, the curing agent is specifically β-hydroxyalkylamide; the leveling agent is specifically a silica-adsorbed polyacrylic acid leveling agent, brand name CM506; the degassing agent is specifically benzoin; and the antioxidant is specifically a mixture of 0.4 kg antioxidant 3114 and 0.1 kg antioxidant 168.

[0101] In this embodiment, the pigment is a mixture of sericite powder, rutile titanium dioxide, and silica-coated inorganic pigment, wherein the mass ratio of sericite powder, rutile titanium dioxide, and silica-coated inorganic pigment is 20:3:1.5, i.e., it includes 20 kg of sericite powder, 3 kg of rutile titanium dioxide, and 1.5 kg of inorganic pigment. Specifically, the inorganic pigment selected is Neobilite silica-coated ultramarine.

[0102] A method for preparing an ultra-weather-resistant powder coating includes the following steps:

[0103] By weight, the base resin is heated to 120°C and stirred until homogeneous. Then, curing agent, leveling agent, degassing agent, antioxidant and pigments are added. The temperature is maintained and the mixture is stirred at 400 r / min for 30 min until homogeneous. The mixture is then transferred to a screw extruder, and the screw speed is controlled at 15 r / min. The extrusion temperature is 145°C for melt extrusion, tableting, crushing and sieving to obtain an ultra-weather-resistant powder coating.

[0104] An application of an ultra-weather-resistant powder coating, which can be used for surface protection coating of metal roofing or factory roofing sheets or outdoor metal components.

[0105]

Example 2

[0106] An ultra-weather-resistant powder coating comprises the following raw materials: 65kg matrix resin, 3kg curing agent, 1.2kg leveling agent, 0.3kg degassing agent, 0.8kg antioxidant, and 29.7kg pigments and fillers.

[0107] In this embodiment, the matrix resin is a mixture of polyester resin and fluorocarbon resin in a mass ratio of 57:8. The polyester resin includes ultra-weather-resistant polyester and crystalline polyester, with a mass ratio of ultra-weather-resistant polyester to crystalline polyester of 50:7. That is, the matrix resin comprises 50 kg of ultra-weather-resistant polyester, 7 kg of crystalline polyester, and 8 kg of fluorocarbon resin. Specifically, the ultra-weather-resistant polyester is the one prepared in [Preparation Example 1], the crystalline polyester is commercially available Uralac P9000, and the fluorocarbon resin is commercially available HLR-1.

[0108] In this embodiment, the curing agent is specifically β-hydroxyalkylamide; the leveling agent is specifically silica-adsorbed polyacrylic acid leveling agent, brand name CM506; the degassing agent is specifically benzoin; and the antioxidant is specifically a mixture of 0.5 kg antioxidant 3114 and 0.3 kg antioxidant 168.

[0109] In this embodiment, the pigment is a mixture of sericite powder, rutile titanium dioxide, and silicon-coated inorganic pigment, wherein the mass ratio of sericite powder, rutile titanium dioxide, and silicon-coated inorganic pigment is 24:4:1.7, that is, it includes 24 kg of sericite powder, 4 kg of rutile titanium dioxide, and 1.7 kg of inorganic pigment. Specifically, the inorganic pigment selected is Neobilite's silicon-coated ultramarine.

[0110] A method for preparing an ultra-weather-resistant powder coating includes the following steps:

[0111] By weight, the base resin is heated to 130°C and stirred until homogeneous. Then, curing agent, leveling agent, degassing agent, antioxidant and pigments are added. The temperature is maintained and the mixture is stirred at 400 r / min for 30 min until homogeneous. The mixture is then transferred to a screw extruder, and the screw speed is controlled at 15 r / min. The extrusion temperature is 150°C for melt extrusion, tableting, crushing and sieving to obtain an ultra-weather-resistant powder coating.

[0112] An application of an ultra-weather-resistant powder coating, which can be used for surface protection coating of metal roofing or factory roofing sheets or outdoor metal components.

[0113]

Example 3

[0114] An ultra-weather-resistant powder coating differs from [Example 1] in that it uses a different base resin.

[0115] In this embodiment, the polyester resin in the matrix resin is specifically selected from the ultra-weather-resistant polyester prepared in [Preparation Example 2].

[0116]

Example 4

[0117] An ultra-weather-resistant powder coating differs from [Example 1] in that it uses a different base resin.

[0118] In this embodiment, the polyester resin in the matrix resin is specifically selected from the ultra-weather-resistant polyester prepared in [Preparation Example 3].

[0119]

Example 5

[0120] An ultra-weather-resistant powder coating differs from [Example 1] in that it uses a different base resin.

[0121] In this embodiment, the polyester resin in the matrix resin is specifically selected from the ultra-weather-resistant polyester prepared in [Preparation Example 4].

[0122]

Example 6

[0123] An ultra-weather-resistant powder coating differs from [Example 4] in that it uses a different base resin.

[0124] In this embodiment, the polyester resin in the matrix resin is specifically selected from the ultra-weather-resistant polyester prepared in [Preparation Example 5].

[0125]

Example 7

[0126] An ultra-weather-resistant powder coating differs from [Example 4] in that it uses a different base resin.

[0127] In this embodiment, the polyester resin in the matrix resin is specifically selected from the ultra-weather-resistant polyester prepared in [Preparation Example 6].

[0128]

Example 8

[0129] An ultra-weather-resistant powder coating differs from [Example 4] in that it uses a different base resin.

[0130] In this embodiment, the polyester resin in the matrix resin is specifically selected from the ultra-weather-resistant polyester prepared in [Preparation Example 7].

[0131]

Example 9

[0132] An ultra-weather-resistant powder coating differs from [Example 4] in that it uses a different base resin.

[0133] In this embodiment, the polyester resin in the matrix resin is specifically selected from the ultra-weather-resistant polyester prepared in [Preparation Example 8].

[0134]

Example 10

[0135] An ultra-weather-resistant powder coating differs from [Example 4] in that it uses a different base resin.

[0136] In this embodiment, the polyester resin in the matrix resin is specifically selected from the ultra-weather-resistant polyester prepared in [Preparation Example 9].

[0137] Comparative Example

[0138] Comparative Example 1

[0139] A powder coating, which differs from [Example 1] in that it uses a different base resin.

[0140] In this comparative example, no crystalline polyester was added to the matrix resin, and commercially available ultra-weather-resistant polyester was used to replace the crystalline polyester in an equal amount. That is, the matrix resin included 65 kg of ultra-weather-resistant polyester and 5 kg of fluorocarbon resin.

[0141] Comparative Example 2

[0142] A powder coating, which differs from [Example 1] in that it uses a different base resin.

[0143] In this comparative example, no fluorocarbon resin was added to the matrix resin, and commercially available ultra-weather-resistant polyester was used to replace the fluorocarbon resin in equal amounts. That is, the matrix resin included 58 kg of ultra-weather-resistant polyester and 12 kg of crystalline polyester.

[0144] Comparative Example 3

[0145] A powder coating, which differs from [Example 3] in that it uses a different base resin.

[0146] In this comparative example, no crystalline polyester was added to the matrix resin, and the crystalline polyester was replaced in equal amounts with an ultra-weather-resistant polyester prepared in [Preparation Example 2]. That is, the matrix resin contained 65 kg of ultra-weather-resistant polyester and 5 kg of fluorocarbon resin.

[0147] Performance test data

[0148] Sample preparation: Under the same spraying pressure, the powder coatings prepared in Examples 1-10 and Comparative Examples 1-2 were sprayed onto standard metal test plates preheated in an oven at 1800℃ using high-voltage electrostatic spraying. The test plates were galvanized tinplate with a thickness of 0.2 mm and a coating thickness of approximately 60 μm. The curing temperature was 200℃, and the curing time was 5 min, thus obtaining the test samples. The standard test plates used for testing were pretreated according to GB / T 9271-2008 Standard Test Plates for Paints and Varnishes.

[0149] Aging treatment: The test samples were subjected to an automatic cyclic exposure test according to the provisions of Method A, Cycle No. 1 in Table 3 of GB / T 16422.2-2014 Laboratory Light Source Exposure Test Method for Plastics, with an exposure time of 2000h.

[0150] 1. Weather resistance: The samples were tested before and after aging according to GB / T 9754 "Determination of specular gloss at 20°, 60° and 85° for paints and varnishes without metallic pigments". The test geometry was 60°±0.1°, and the gloss loss rate was calculated. The higher the gloss loss rate, the lower the gloss retention rate.

[0151] 2. Bending resistance: The test shall be conducted in accordance with GB / T 30791-2014 Paints and Varnishes T-bend Test, and the test results of each sample shall be recorded.

[0152] 3. Surface hardness: The test shall be conducted in accordance with GB / T 6739-2006 Determination of hardness of paint film by pencil method, and the test results of each sample shall be recorded.

[0153] 4. Impact resistance: The test shall be conducted in accordance with GB / T 1732-2020 Test Method for Impact Resistance of Coating Film. A 4x magnifying glass shall be used to observe whether there are cracks, wrinkles and peeling. The maximum height (cm) of the hammer when no cracks, wrinkles and peeling are observed in three tests shall be recorded. If the maximum height of the hammer reaches or exceeds 80cm, then 80cm shall be recorded directly.

[0154] 5. Heat resistance: Place each sample to be tested in an oven, heat to 230℃ and bake for 2 hours. Then use a colorimeter to compare the surface color difference ΔE before and after baking.

[0155] Table 1. Partial Performance Test Data of Powder Coatings

[0156] Loss of light (%) Bending resistance hardness Drop weight height (cm) Baking color difference Example 1 23 0T 2H 70 3.2 Example 2 30 1T 3H 65 2.1 Example 3 29 1T 3H 65 2.6 Example 4 27 1T 3H 70 2.3 Example 5 26 2T 4H 70 2.2 Example 6 30 0T 2H 60 3.8 Example 7 31 0T 1H 80 2.5 Example 8 25 0T 2H 75 2.1 Example 9 24 0T 2H 75 2 Example 10 32 0T H 55 4.3 Comparative Example 1 25 3T 3H 55 3.3 Comparative Example 2 38 0T H 60 3.2 Comparative Example 3 32 4T 4H 50 2.2

[0157] Based on Examples 1 and Comparative Examples 1-2, and the data in Table 1, it can be seen that the powder coating prepared by using crystalline polyester in combination with ultra-weather-resistant polyester and fluorocarbon resin as the matrix resin exhibits excellent weather resistance and flexural strength after coating formation, while its impact resistance is also slightly improved. This may be because although fluorocarbon resin can significantly improve the weather resistance of powder coating, its highly polar fluorocarbon bonds and the resulting dense cross-linked protective network both hinder the movement of polyester chain segments, resulting in a significant increase in coating hardness and rigidity. However, crystalline polyester can introduce more flexible substances through phase transformation during the reaction, reducing the inhibition of polymer chain extensibility caused by the introduction of fluorocarbon resin, thereby improving the overall flexibility of the coating and balancing the ultra-durability and mechanical properties of the powder coating.

[0158] Combining Examples 1 and 3 with the data in Table 1, it can be seen that the ultra-weather-resistant polyester prepared by using polyols including ethyl butyl propylene glycol, neopentyl glycol, and isosorbide in combination with polyacids, although its weather resistance and flexural strength are not as good as those of commercially available ultra-weather-resistant polyesters, its overall performance is not significantly different. This is beneficial for controlling raw material costs when preparing ultra-weather-resistant powder coatings. Moreover, the powder coating prepared from the self-made ultra-weather-resistant polyester has lower color difference at short-term high temperatures, indicating that it has higher heat resistance than commercially available ultra-weather-resistant polyesters and is more suitable for applications in scenarios requiring prolonged high temperatures. In addition, combining Examples 3 and Comparative Example 3 with the data in Table 1, it can be seen that crystalline polyesters are also suitable for improving powder coating systems using self-made ultra-weather-resistant polyester as the matrix resin.

[0159] Based on Examples 3-6 and the data in Table 1, it can be seen that when the mass ratio of ethyl butyl propylene glycol, neopentyl glycol, and isosorbide is 1:(1.5-2):(0.2-0.7), the weather resistance, bending resistance, and heat resistance of the powder coating are significantly improved as isosorbide gradually replaces neopentyl glycol in equal amounts and its proportion in the mixed polyols increases. However, as the content of isosorbide further increases, not only is the improvement in the weather resistance, bending resistance, and heat resistance of the powder coating not significant, but it also leads to a further increase in the hardness of the coating formed by the powder coating and a decrease in its bending resistance. This may be due to the synergistic threshold between rigid isosorbide and flexible ethyl butyl propylene glycol and neopentyl glycol. When the amount of isosorbide added is within the threshold range, the rigid domains formed by the rigid furan ring of isosorbide are uniformly dispersed in the flexible mechanism. While increasing the molecular chain packing density, it can capture photon energy and block photodegradation reactions, without affecting the active deformation of the flexible chains in the system, thus showing a significant improvement in overall performance. However, when the amount of isosorbide added exceeds the threshold, the proportion of rigid segments in the system is too high. Not only is it difficult for stress to be dispersed through the flexible segments, but the movement of the segments is also significantly restricted, resulting in brittleness. At the same time, the light absorption performance of isosorbide also approaches saturation, and the weather resistance improvement effect of excessive addition is not good.

[0160] Combining Examples 4 and 7 with the data in Table 1, it can be seen that as the proportion of isophthalic acid in the mixed polybasic acid gradually decreases, the weather resistance, hardness, and heat resistance of the prepared powder coating significantly decrease, while its bending resistance and impact resistance improve. This may be because as the proportion of isophthalic acid decreases, the benzene ring density of the system chain segments decreases, which not only weakens the ultraviolet shielding effect but also affects the packing density of the molecular chains, leading to a decrease in the weather resistance, hardness, and heat resistance of the powder coating. At the same time, due to the increase in the proportion of flexible chain segments, the space for free movement of the molecular chains increases, and stress can be dispersed through the movement of chain segments, making it less prone to bending and cracking, and its impact resistance is also improved.

[0161] Combining Examples 4 and 8-10 with the data in Table 1, it can be seen that adding a branching agent in the preparation of ultra-weather-resistant polyester can effectively improve the coating rigidity and weather resistance of the subsequent powder coating. Furthermore, when a lightly branched polyester polyol is used as the branching agent, compared to using trimethylolpropane as the branching agent, the weather resistance, flexural strength, and impact resistance of the resulting powder coating are significantly improved, while its heat resistance is also slightly improved. This may be because the branching agent can form network nodes in the polyester chain segments and enhance the intermolecular forces. On the one hand, it can crosslink and restrict chain segment movement, improving the coating hardness and heat resistance; on the other hand, the formed dense network can effectively block oxygen or moisture penetration, delaying photo-oxidative aging and improving the coating's weather resistance. Secondly, lightly branched polyester polyols are macromolecular branching agents. The active hydroxyl groups are linked by long-chain polyesters, which not only have long-chain flexibility, but also dispersed branching points, forming a more uniform cross-linked network. This is more conducive to further balancing the rigidity and flexibility of powder coatings. At the same time, long-chain polyesters can also reduce oxidation sites, which is beneficial to further improving the weather resistance and heat resistance of powder coatings.

[0162] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this specific embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A super weather-resistant powder coating, characterized in that, Includes the following quantities of raw materials: Matrix resin: 65-70 parts; 3-3.6 parts of curing agent; Leveling agent: 1-1.2 parts; Degassing agent: 0.3-0.4 parts; Antioxidant: 0.5-0.8 parts; Pigments and fillers: 24.5-29.7 parts; The matrix resin is a mixture of polyester resin and fluorocarbon resin, and the mass ratio of the polyester resin to the fluorocarbon resin is (57-65):(5-8). The polyester resin includes ultra-weather-resistant polyester and crystalline polyester, and the mass ratio of the ultra-weather-resistant polyester to the crystalline polyester is (50-53):(7-12). The ultra-weather-resistant polyester is prepared from the following raw materials in parts by weight: Mixed polyols: 35-40; Mixed polyacids: 52-58; Branching agent: 4.5-5; Esterification catalyst: 0.2-0.3; Acidic end-capping agent: 1.8-2.2; The mixed polyol is a mixture of ethyl butyl propylene glycol, neopentyl glycol and isosorbide, the mixed polyacid is a mixture of 1,4-cyclohexanedicarboxylic acid, methylene succinic acid and isophthalic acid, the branching agent is a lightly branched polyester polyol, and the hydroxyl content of the lightly branched polyester polyol is 4.3%-5.8%.

2. The ultra-weather-resistant powder coating according to claim 1, characterized in that: The mass ratio of the ethyl butyl propylene glycol, the neopentyl glycol and the isosorbide is 1:(0.5-2):(0.2-0.7); the mass ratio of the 1,4-cyclohexanedicarboxylic acid, the methylene succinic acid and the isophthalic acid is 1:(1-1.5):(2.5-7).

3. The ultra-weather-resistant powder coating according to claim 2, characterized in that: The preparation method of the weather-resistant polyester includes the following steps: A1. By mass, first add the mixed polyol, branching agent and esterification catalyst into the reaction apparatus, heat to 110-130℃ and stir thoroughly, add the mixed polyacid, and simultaneously introduce inert gas, continue stirring in the inert atmosphere and heat to 180-200℃, wait for the esterification water to start to be generated and stabilized and distilled out, then heat to 225-235℃ and keep the reaction at this temperature for 30-45 minutes; A2. When the distilled esterified water reaches 95% of the theoretical value, add an acidic capping agent, then heat to 240-245℃ and continue the reaction for 40-60 minutes. A3. When the acid value in the reaction system reaches 35-38 mgKOH / g, vacuum is applied and the reaction is continued for 20-30 minutes. After the reaction is completed, the material is cooled and discharged to obtain an ultra-weather-resistant polyester.

4. The ultra-weather-resistant powder coating according to claim 1, characterized in that: The curing agent is β-hydroxyalkylamide, the leveling agent is a silica-adsorbed polyacrylic acid leveling agent, and the degassing agent is benzoin.

5. The ultra-weather-resistant powder coating according to claim 1, characterized in that: The antioxidant is a mixture of antioxidant 3114 and antioxidant 168, and the mixing ratio of antioxidant 3114 to antioxidant 168 is 1:(0.25-0.6).

6. The ultra-weather-resistant powder coating according to claim 1, characterized in that: The pigment is a mixture of sericite powder, rutile titanium dioxide and inorganic pigment, and the mass ratio of the sericite powder, the rutile titanium dioxide and the inorganic pigment is (20-24):(3-4):(1.5-1.7).

7. A method for preparing an ultra-weather-resistant powder coating, used to prepare an ultra-weather-resistant powder coating as described in any one of claims 1-6, characterized in that, Includes the following steps: By weight, the base resin is heated to 120-130℃ and stirred and mixed. After the mixture is uniform, the curing agent, leveling agent, degassing agent, antioxidant and pigments and fillers are added. After the raw materials are mixed evenly, the mixture is transferred to a screw extruder and melt-extruded, pressed, crushed and screened at 145-160℃ to obtain an ultra-weather-resistant powder coating.

8. An application of an ultra-weather-resistant powder coating, applicable to an ultra-weather-resistant powder coating as described in any one of claims 1-6, characterized in that: Surface protective coating for metal roofing or factory roofing sheets or outdoor metal components.