An ethylene-tetrafluoroethylene powder coating for anticorrosive lining and a method for preparing the same

Abstract

The application belongs to the technical field of fluorine-containing polymer powder coating, and discloses an ethylene-tetrafluoroethylene powder coating for corrosion-proof lining and a preparation method thereof, the ethylene-tetrafluoroethylene powder coating for corrosion-proof lining comprises the following components in mass fraction: ethylene-tetrafluoroethylene copolymer 100 parts, heat stabilizer 0.01-5 parts, flow aid 0.1-10 parts, photoinitiator 0.5-5 parts, pigment 0-5 parts, and auxiliary crosslinking agent 0.5-3 parts. The ethylene-tetrafluoroethylene powder coating for corrosion-proof lining is prepared by adding the photoinitiator and the auxiliary crosslinking agent in the ethylene-tetrafluoroethylene copolymer, so that the ethylene-tetrafluoroethylene powder coating for corrosion-proof lining can improve the temperature resistance and wear resistance of the corrosion-proof lining through ultraviolet curing crosslinking without affecting the molding of the traditional powder coating, and the application prospect of the ETFE powder coating is expanded.

Description

Technical Field

[0001] This invention belongs to the field of fluoropolymer powder coating technology, specifically relating to an ethylene-tetrafluoroethylene powder coating for anti-corrosion linings and its preparation method. Background Technology

[0002] Ethylene-tetrafluoroethylene copolymer (ETFE), also known as F40, is a transparent crystalline material and is the strongest and lightest fluoroplastic. ETFE possesses excellent dielectric, insulating, and mechanical properties; it is resistant to radiation, cracking, aging, various chemical solvents, and high and low temperatures. Compared to other anti-corrosion lining materials such as PTFE coatings and FEP coatings, ETFE has better toughness, superior mechanical properties, better processability, and better adhesion to substrates. Anti-corrosion containers made from ETFE can withstand negative pressure. ETFE coatings hold an irreplaceable position in the anti-corrosion field because they can be made into seamless, chemical-resistant, high-temperature-resistant, and weather-resistant films. ETFE powder coatings can be easily made into seamless anti-corrosion films of any shape using electrostatic spraying, rotational molding, and fluidized bed impregnation methods. ETFE powder coatings for corrosion protection are widely used both domestically and internationally, such as in exhaust gas treatment towers, distillation towers, waste liquid treatment towers, chemical raw material storage tanks, and air ducts in the semiconductor manufacturing industry.

[0003] With advancements in industrial technology, the demand for heat resistance in corrosion-resistant lining materials is increasing. ETFE, being a partially fluorinated fluoropolymer with an ethylene structure in its molecular chain, has a lower temperature resistance compared to other perfluoropolymers such as FEP, PTFE, and PFA, with long-term operating temperatures generally below 150°C. However, for specific applications with higher requirements, existing ethylene-tetrafluoroethylene (ETFE) copolymers exhibit poor temperature resistance, prone to high-temperature cracking, yellowing, and melt dripping, limiting their application in areas with higher temperature resistance requirements. Furthermore, corrosion-resistant applications also place higher demands on the abrasion resistance of lining materials. When existing ETFE materials are used in corrosion-resistant lining environments with high abrasion resistance requirements, their poor scratch and abrasion resistance can easily lead to scratches and subsequent failure of the corrosion-resistant lining. Summary of the Invention

[0004] To address the shortcomings of the prior art, this invention discloses an ethylene-tetrafluoroethylene powder coating for anti-corrosion linings. Anti-corrosion linings prepared using this ethylene-tetrafluoroethylene powder coating exhibit superior temperature resistance and abrasion resistance.

[0005] The specific technical solution is as follows:

[0006] An ethylene-tetrafluoroethylene powder coating for corrosion-resistant lining comprises, by weight parts: 100 parts of ethylene-tetrafluoroethylene copolymer, 0.01-5 parts of heat stabilizer, 0.1-10 parts of flow aid, 0.5-5 parts of photoinitiator, 0-5 parts of pigment, and 0.5-3 parts of crosslinking agent.

[0007] Existing technologies for modifying ethylene-tetrafluoroethylene (ETF) copolymers primarily improve their permeability resistance through filler modification. However, filler modification does not improve the temperature resistance of ETF copolymers, and the addition of fillers is detrimental to the material's wear resistance. If ETF powder coatings are modified using traditional thermal crosslinking methods for use in anti-corrosion linings, the ETF powder coating undergoes crosslinking before the lining is formed, leading to uneven leveling and inconsistent thickness. Therefore, in existing anti-corrosion lining technologies, unmodified ETF powder coatings are mostly used directly.

[0008] This invention modifies ethylene-tetrafluoroethylene (ETF) powder coatings for anti-corrosion linings using photoinitiators and co-crosslinking agents. During the molding process of the anti-corrosion lining, the ethylene-tetrafluoroethylene powder does not undergo crosslinking, avoiding the impact on the molding effect caused by premature crosslinking and curing of the ethylene-tetrafluoroethylene powder coating before lining molding. After the anti-corrosion lining is molded, it can be crosslinked and cured using ultraviolet light irradiation, improving the temperature resistance and wear resistance of the anti-corrosion lining.

[0009] The amount of the crosslinking agent added in this invention is 0.5 to 3 parts. If the amount added is too low, an effective crosslinking structure cannot be formed, and it does not contribute to the temperature resistance and wear resistance of the anti-corrosion lining. If the amount added is too high, small molecule substances will be introduced because the crosslinking agent itself is not stable enough. After the crosslinking reaction, the remaining crosslinking agent will play a role in promoting decomposition, which will affect the color and thermal stability of the coating. Moreover, excessive crosslinking will also affect the molding performance of the coating.

[0010] Furthermore, the photoinitiator is one or a combination of benzoin and its derivatives, benzoyl groups, alkyl phenyl ketones, α-hydroxyalkyl phenyl ketones, α-aminealkyl phenyl ketones, acylphosphine oxides, and benzophenones. Preferably, the photoinitiator is one or a combination of acylphosphine oxides and benzophenones; more preferably, the photoinitiator is trimethylbenzoyl-diphenylphosphine oxide.

[0011] When using ethylene-tetrafluoroethylene powder coating to prepare anti-corrosion linings, the processing temperature is relatively high. Processes such as spraying and roller coating require long-term high temperatures. Acylphosphine oxides and benzophenone photoinitiators have better high-temperature resistance and will not introduce impurities or other defects during the molding of anti-corrosion linings.

[0012] Further, the co-crosslinking agent is one or a combination of allyl acyl groups, allyl imides, allyl triazine groups, or allyl isocyanates. Preferably, the co-crosslinking agent is one or a combination of allyl imides and allyl isocyanates; more preferably, the co-crosslinking agent is one or a combination of triallyl isocyanate, trimethylallyl isocyanate, triallyl cyanate, and trimethylallyl cyanate.

[0013] Allylimide and allyl isocyanate crosslinking agents have high reactivity and good thermal stability. They can exist stably in the coating system during the high-temperature molding process of anti-corrosion linings without affecting the molding of the anti-corrosion linings.

[0014] Furthermore, the ethylene-tetrafluoroethylene copolymer comprises 30-55 mol% ethylene repeating units, 40-65 mol% tetrafluoroethylene repeating units, and 0.1-10 mol% functional monomer repeating units. The melt index of the ethylene-tetrafluoroethylene copolymer is 5-40 g / 10 min, preferably 10-30 g / 10 min.

[0015] The functional monomer is one or a combination of perfluoroalkenyl ether monomers, perfluoroalkyl vinyl monomers, and fluoroacrylate vinyl ester monomers. Perfluoroalkenyl ether monomers are preferably perfluoromethyl vinyl ether, perfluoron-propyl vinyl ether, and perfluorobutyl vinyl ether. Perfluoroalkyl vinyl monomers are preferably perfluoropropylethylene, perfluorobutylethylene, and perfluorohexylethylene. Fluoroacrylate vinyl ester monomers are preferably fluorobutenoic acid vinyl ester, fluorohexenoic acid vinyl ester, and fluoroacrylate vinyl ester.

[0016] Furthermore, the heat stabilizer is one or a combination of copper compounds, tin compounds, iron compounds, titanium compounds, and magnesium compounds, such as copper oxide, tin oxide, copper iodide, cuprous iodide, tin sulfate, tin pyrophosphate, and barium sulfate. Preferably, the heat stabilizer is barium sulfate, tin pyrophosphate, tin sulfite, or copper iodide. More preferably, the heat stabilizer is copper iodide or tin pyrophosphate.

[0017] Furthermore, the heat stabilizer powder has an average particle size of 0.3–5 μm and an oil absorption value of 60–200 ml / 100 g.

[0018] Furthermore, the flow aid is one or a combination of polysiloxane, fluorosilicone-modified acrylate, and silica. Preferably, the flow aid is a composition of fluorosilicone-modified acrylate and silica.

[0019] Fluorosilicone-modified acrylates are preferably copolymers of trifluoroethyl methacrylate (TFEMA), vinyltriethoxysilane (A-151), methyl methacrylate (MMA), and butyl acrylate (BMA).

[0020] Silica is preferably fumed silica, and more preferably one or a combination of Cabot's M-5 and EH-5; DEGUSSA's Aerosil 200 and Aerosil 972; and WACKER's H-15 and N-20.

[0021] Furthermore, the pigment is any one of copper chrome black, carbon black, organic yellow, chrome green, chrome black, and titanium dioxide. All of the above pigments possess high-temperature resistance, and those skilled in the art can select the specific pigment type and dosage according to application requirements.

[0022] This invention also discloses a method for preparing ethylene-tetrafluoroethylene powder coating for anti-corrosion linings, comprising the following steps:

[0023] Ethylene tetrafluoroethylene copolymer, heat stabilizer, flow aid, photoinitiator, pigment, and crosslinking agent are added to a mixing device according to the above-mentioned mass proportions, and the mixture is rotated at high speed to obtain a uniform raw material.

[0024] The mixing time is 5-10 minutes, and the stirring speed of the mixing equipment is 20-500 r / min. Suitable mixing equipment includes V-type mixers, double cone mixers, bucket mixers, drum mixers, screw mixers, horizontal cylindrical mixers, paddle mixers, and screw mixers.

[0025] The raw material is fed into a twin-screw extruder at a uniform speed for melt extrusion, and then cooled by a cooling roller to obtain a sheet; wherein the melt extrusion temperature is 150-300℃.

[0026] The material is crushed, ground, and sieved to obtain ethylene-tetrafluoroethylene powder coating with the target particle size; wherein the crusher can be a hammer mill, turbine mill, jet mill, etc.

[0027] The particle size of the ethylene-tetrafluoroethylene powder coating is selected according to the forming method of the anti-corrosion lining. For example, when electrostatic spraying is used, the average particle size of the ethylene-tetrafluoroethylene powder coating is 0.5-300 μm, preferably 5-200 μm; when roller coating is used, the average particle size of the ethylene-tetrafluoroethylene powder coating is 2-700 μm, preferably 50-400 μm; when fluidized bed dip coating is used, the average particle size of the ethylene-tetrafluoroethylene powder coating is 0.5-500 μm, preferably 20-300 μm.

[0028] The present invention also discloses a method for preparing an anti-corrosion lining, which is prepared using any of the ethylene-tetrafluoroethylene powder coatings described above.

[0029] Furthermore, the method for preparing the anti-corrosion lining includes the following steps:

[0030] The ethylene-tetrafluoroethylene powder coating is processed and shaped using any one of the following methods: electrostatic spraying, fluidized bed impregnation, and roller coating. The shaped workpiece is then subjected to cross-linking and curing by ultraviolet (UV) irradiation for 2–60 min at a temperature of 50–200 °C and an intensity of 5–100 mW / cm². 2 .

[0031] The specific steps of electrostatic spraying are as follows:

[0032] (1) Apply a layer of powder primer or liquid primer to the substrate and dry it at 260-330℃ to melt and level it into a film;

[0033] (2) Apply ethylene-tetrafluoroethylene powder coating onto the baked high-temperature substrate;

[0034] (3) Heat the substrate coated with primer and powder coating to 260-330℃ to melt and level it;

[0035] (4) Repeat steps (2) and (3) until the target coating is obtained, with a coating thickness of 300-1000 μm.

[0036] The specific steps of fluidized bed impregnation are as follows:

[0037] (1) Heating the substrate to a high temperature of 300-360℃;

[0038] (2) It comes into contact with the ethylene-tetrafluoroethylene powder coating suspended in the fluidized bed. The ethylene-tetrafluoroethylene powder melts and adheres to the surface of the substrate to form a coating film.

[0039] Among them, the substrates for electrostatic spraying and fluidized bed impregnation refer to chemical containers, reactors, or parts that require corrosion protection.

[0040] The specific steps for roller coating are as follows:

[0041] Ethylene-tetrafluoroethylene powder coating is poured into the container and heated to 250-330℃ while rotating, so that the ethylene-tetrafluoroethylene powder melts onto the inner wall of the container to form an anti-corrosion lining.

[0042] By adopting the above technical solution, the beneficial effects of the present invention are as follows:

[0043] This invention, by adding photoinitiators and crosslinking agents to ethylene-tetrafluoroethylene copolymer, prepares an ethylene-tetrafluoroethylene powder coating for corrosion-resistant linings. This coating not only improves the temperature resistance and wear resistance of corrosion-resistant linings through UV curing crosslinking without affecting the molding of traditional powder coatings, but also expands the application prospects of ETFE powder coatings.

[0044] Since the ETFE powder coating of the present invention does not undergo cross-linking at high temperatures, the ETFE powder coating prepared by the present invention can be applied to various forming and processing methods such as electrostatic spraying, fluidized bed impregnation, and roller coating.

[0045] The preparation method of this invention is simple, low-cost, easy to operate, and suitable for large-scale production. Moreover, no organic solvents are used in the preparation process, making it green and environmentally friendly. Detailed Implementation

[0046] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not serve to limit it in any way.

[0047] The raw materials used in the embodiments and comparative examples of this invention are as follows. Unless otherwise stated, the raw materials used in the embodiments and comparative examples of this invention are all commercially available products.

[0048] Ethylene-tetrafluoroethylene copolymer: 47 mol% ethylene, 49 mol% tetrafluoroethylene, and 4 mol% functional monomers;

[0049] Heat stabilizer: tin pyrophosphate, average particle size 1.5μm, oil absorption value 100ml / 100g;

[0050] Flow aid: Aerosil 972 (Degussa, Germany);

[0051] Pigment: Cabot carbon black.

[0052] The photoinitiator and crosslinking agent are detailed in the respective embodiments.

[0053] In the embodiments and comparative examples of this invention, various performance parameters were tested according to the following methods:

[0054] 1. Tensile strength and elongation at break: The UV-cured samples were tested according to GB / T 2918-2018. The curing time was 20 min, the test environment temperature was 23℃±2℃, the tensile speed was 50 mm / min±5 mm / min, the lengths of the two ends of the sample were equal, and the spacing between the clamps was 24 mm.

[0055] 2. ETFE copolymer composition (mol%): determined by NMR and fluorine content testing.

[0056] 3. Heat resistance test, air heat aging tensile properties conditions: 260℃, 12h;

[0057] 4. Dynamic friction coefficient: The coefficient of friction of the UV-cured samples shall be determined in accordance with the provisions of GB 10006-1988.

[0058] 5. Evaluation of Electrostatic Spraying Formability: The test panel substrate was carbon steel, which was treated using traditional roughening methods, such as 60-mesh alumina sandblasting. A Gemma spray gun with a voltage of 50kV was used for electrostatic spraying of the primer at room temperature. The substrate was then placed in an oven and baked at 295-300℃ for approximately 20 minutes. Baking at a temperature above the melting point of ETFE allowed the ETFE to melt and level into a film. Each coat was approximately 100μm thick. This spray-baking process was repeated three times to obtain a laminated coating. The coating was observed to ensure it was smooth, glossy, and free of bubbles.

[0059] 6. Yellowing resistance: Weigh 2.5±0.2g of the material without added pigment, place it in a container made of 5cm*5cm aluminum foil, sinter it in a sintering furnace at 315℃ for 40min, and visually observe the color change.

[0060] In the embodiments and comparative examples of the present invention, the ultraviolet light crosslinking curing temperature was 100°C, the light intensity was 25mW / cm2, and the time was 20 minutes.

[0061] The components and mass fractions of the ethylene-tetrafluoroethylene powder coatings used for anti-corrosion linings in Examples 1-6 are shown in Table 1:

[0062] Table 1. Composition of ethylene-tetrafluoroethylene powder coating for anti-corrosion linings in Examples 1-6

[0063]

[0064] The preparation methods of ethylene-tetrafluoroethylene powder coatings for anti-corrosion linings in Examples 1-6 are as follows:

[0065] (1) Add the ethylene tetrafluoroethylene copolymer, heat stabilizer, flow aid, photoinitiator, pigment, and crosslinking agent to a V-type mixer according to the mass proportions in Table 1, and stir at a speed of 300 r / min for 8 min to obtain raw material;

[0066] (2) The uniformly mixed raw material is fed into a twin-screw extruder at a constant speed for melt extrusion. The melt extrusion temperature is 250℃. After passing through the cooling roller, the material is rolled and cooled into sheets.

[0067] (3) The obtained material is crushed, ground and sieved to obtain ethylene-tetrafluoroethylene powder coating with target particle size.

[0068] Examples 7-8

[0069] The only difference between Example 7 and Example 3 is that the photoinitiator is replaced with a 1:1 composition of benzoyl-diphenylphosphine oxide and micriton in equal parts by mass. The other components, parts by mass, and preparation methods are exactly the same as in Example 3.

[0070] The only difference between Example 8 and Example 3 is that the photoinitiator is replaced with an equal mass of α-amine alkyl phenyl ketone. The other components, mass fractions, and preparation methods are exactly the same as in Example 3.

[0071] Examples 9-10

[0072] The only difference between Example 9 and Example 3 is that the crosslinking agent is replaced with an equal mass ratio of trimethylallyl isocyanate and triallyl cyanate (trimethylallyl isocyanate to triallyl cyanate mass ratio 1:1). The other components, mass ratios, and preparation methods are exactly the same as in Example 3.

[0073] The only difference between Example 10 and Example 3 is that the crosslinking agent is replaced with an equal mass of 2,4,6-tris(allyloxy)-1,3,5-triazine. The other components, mass fractions, and preparation methods are exactly the same as in Example 3.

[0074] The components and mass fractions of the ethylene-tetrafluoroethylene powder coatings in Comparative Examples 1–6 are shown in Table 2:

[0075] Table 2. Composition of ethylene-tetrafluoroethylene powder coatings (Comparative Examples 1-6)

[0076]

[0077]

[0078] The preparation methods of the ethylene-tetrafluoroethylene powder coatings in Comparative Examples 1-6 are the same as those in Examples 1-10.

[0079] The tensile properties, heat resistance, and abrasion resistance of the ethylene-tetrafluoroethylene powder coatings of the above embodiments and comparative examples were tested, and the test results are shown in Tables 3 and 4 below.

[0080] Table 3. Test results of ethylene-tetrafluoroethylene powder coatings used in anti-corrosion linings of Examples 1-10

[0081]

[0082] Table 4. Test results of ethylene-tetrafluoroethylene powder coatings for comparative examples 1-6

[0083]

[0084]

[0085] As can be seen from Example 1 and Comparative Example 1, the addition of photoinitiator and co-crosslinking agent does not affect the molding and processability of powder coating; UV curing crosslinking improves the rigidity and hardness of the material, giving it a lower coefficient of dynamic friction. The lower the coefficient of dynamic friction, the better the wear resistance; at the same time, it improves the heat resistance of the material, significantly increasing the high-temperature aging retention rate and broadening the application range of ETFE powder coating.

[0086] As can be seen from Example 1 and Comparative Example 6, not all photoinitiators and crosslinking agents can be used in this invention to improve the heat resistance and wear resistance of the material.

[0087] Comparative Examples 3 and 5 show that when the mass ratio of the co-crosslinking agent to the ethylene tetrafluoroethylene copolymer is 0.4:100, an effective crosslinking structure cannot be formed, resulting in poor temperature resistance and abrasion resistance of the material. When the mass ratio of the co-crosslinking agent to the ethylene tetrafluoroethylene copolymer is 4:100, the proportion of the co-crosslinking agent in the system is too high. Excessive crosslinking leads to poor molding performance of the coating, and the remaining co-crosslinking agent after the crosslinking reaction promotes decomposition, resulting in poor heat resistance of the material.

[0088] Comparative Examples 2 and 4 show that when only a photoinitiator or only a crosslinking agent is added, the temperature resistance and wear resistance of the material are both poor.

[0089] As can be seen from Examples 3, 7, and 8, when the photoinitiator is trimethylbenzoyl-diphenylphosphine oxide, benzoyl-diphenylphosphine oxide, and michidone, the tensile properties of the material are better, the heat resistance of the material is excellent, and the performance retention rate is high. The photoinitiation efficiency of this system is excellent and it has good stability. Under the same process, the UV curing crosslinking is perfect, and its own thermal stability is good and it does not introduce decomposition promoting products, so that ETFE has higher comprehensive performance.

[0090] As can be seen from Examples 3, 9, and 10, when the crosslinking agent is a combination of triallyl isocyanate, trimethallyl isocyanate, and triallyl cyanate, the material has better heat resistance. The crosslinking agent used has high activity and good stability, and can be cured and crosslinked more completely under the same curing process, thus having better heat resistance.

[0091] Examples 1-10 show that the degree of crosslinking of powder coatings can be controlled by selecting functional monomers and adjusting the proportion of crosslinking agents, thereby balancing the processing and molding properties, heat resistance, and wear resistance of the material.

Claims

1. An ethylene-tetrafluoroethylene powder coating for corrosion-resistant linings, characterized in that, Based on parts by mass, it includes the following components: 100 parts of ethylene-tetrafluoroethylene copolymer, 0.01-5 parts of heat stabilizer, 0.1-10 parts of flow aid, 0.5-5 parts of photoinitiator, 0-5 parts of pigment, and 0.5-3 parts of crosslinking agent; The co-crosslinking agent is one or a combination of allyl acyl, allyl imide, allyl triazine, or allyl isocyanate. The photoinitiator includes trimethylbenzoyl-diphenylphosphine oxide.

2. The ethylene-tetrafluoroethylene powder coating according to claim 1, characterized in that, The co-crosslinking agent is one or a combination of allyl imides and allyl isocyanates.

3. The ethylene-tetrafluoroethylene powder coating according to claim 1, characterized in that, The crosslinking agent is one or a combination of triallyl isocyanate, trimethylallyl isocyanate, triallyl cyanate, and trimethylallyl cyanate.

4. The ethylene-tetrafluoroethylene powder coating according to claim 1, characterized in that, The ethylene-tetrafluoroethylene copolymer comprises 30-55 mol% ethylene repeating units, 40-65 mol% tetrafluoroethylene repeating units, and 0.1-10 mol% functional monomer repeating units.

5. The ethylene-tetrafluoroethylene powder coating according to claim 4, characterized in that, The functional monomer is one or a combination of perfluoroolefin monomers, perfluoroalkyl ethylene and fluoroolefin vinyl ester monomers.

6. The ethylene-tetrafluoroethylene powder coating according to claim 1, characterized in that, The heat stabilizer is one or a combination of copper compounds, tin compounds, iron compounds, titanium compounds and magnesium compounds; And / or, the flow aid is one or a combination of polysiloxane, fluorosilicone-modified acrylate, and silica; And / or, the pigment is any one of copper chrome black, carbon black, organic yellow, chrome green, chrome black and titanium dioxide.

7. A method for preparing an ethylene-tetrafluoroethylene powder coating for anti-corrosion lining as described in any one of claims 1-6, characterized in that, Includes the following steps: Ethylene-tetrafluoroethylene copolymer, heat stabilizer, flow aid, photoinitiator, pigment, and crosslinking agent are added to a mixing device according to the mass ratio and mixed evenly to obtain raw material; The raw material is placed in an extruder for melting and extrusion, and then cooled by a cooling roller to obtain a sheet. The material is crushed, ground, and sieved to obtain ethylene-tetrafluoroethylene powder coating with the target particle size.

8. A method for preparing an anti-corrosion lining, characterized in that, Prepared using the ethylene-tetrafluoroethylene powder coating as described in any one of claims 1 to 6.

9. The preparation method according to claim 8, characterized in that, Includes the following steps: Ethylene-tetrafluoroethylene powder coatings are processed and shaped using any of the following methods: electrostatic spraying, fluidized bed impregnation, and roller coating. The processed workpiece is subjected to ultraviolet light irradiation for 2-60 minutes at a temperature of 50-200℃ and an intensity of 5-100 mW / cm. 2 .

Images