An environment-friendly powder coating, its preparation method and application

Abstract

The present invention discloses an environment-friendly powder coating, its preparation method and application, belonging to the technical field of powder coating processing, and is used to solve the technical problem that the wear resistance, impact resistance and ultraviolet aging resistance of powder coatings in the prior art need to be further improved. The present invention comprises the following components by weight: 70-80 parts of polyolefin resin, 15-25 parts of epoxy resin, 5-6 parts of curing agent and 3-5 parts of auxiliary additive. The polyolefin resin is prepared by activating fillers and enhancing unsaturated monomers with olefin-terminated polysiloxane, and then the polyolefin resin is enhanced with epoxy resin, which not only effectively improves the wear resistance and impact resistance of the paint film layer sample, but also improves the adhesion and anti-ultraviolet performance of the paint film, and the production process has little harm to the environment and human health and is relatively friendly to the environment.

Description

Technical Field

[0001] The present invention relates to the technical field of powder coating processing, and specifically relates to an environmentally friendly powder coating and its preparation method and application. Background Art

[0002] Powder coatings are solid powder synthetic resin coatings composed of solid resins, pigments, fillers, and additives. Different from ordinary solvent-based coatings and water-based coatings, their dispersion medium is air rather than solvents and water. With the tightening of global environmental protection policies and the promotion of the "dual carbon" goal, traditional solvent-based coatings have been gradually replaced by environmentally friendly coatings due to their high emissions of volatile organic compounds (VOCs) and serious pollution.

[0003] The coating hardness and impact resistance of the powder coatings in the prior art are poor, and scratches are easily generated under mechanical friction, resulting in a decrease in the durability of mechanical equipment and making it difficult to meet the requirements of high-wear scenarios such as outdoor equipment and heavy-duty machinery. To improve the wear resistance of the material, fillers such as nano-silica and alumina are usually added to the powder coatings, but the nano-fillers are prone to agglomeration, resulting in poor coating leveling and insufficient compatibility with the resin matrix, and are prone to falling off after long-term use. Moreover, the existing powder coatings formed have poor aging resistance, and when used outdoors, they are easily affected by ultraviolet radiation, resulting in coating aging, coating discoloration or powdering.

[0004] In view of the technical defects in this regard, a solution is now proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide an environmentally friendly powder coating and its preparation method and application, which are used to solve the technical problems that the wear resistance, impact resistance and ultraviolet aging resistance of the powder coatings in the prior art need to be further improved.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] An environmentally friendly powder coating, comprising the following components by weight: 70-80 parts of polyolefin resin, 15-25 parts of epoxy resin, 5-6 parts of curing agent, and 3-5 parts of auxiliary additive;

[0008] The preparation method of the polyolefin resin is as follows: under the protection of an inert gas, a solvent and an emulsifier are mixed and stirred, an activated filler, an olefin-terminated polysiloxane, glycidyl methacrylate, styrene and butyl acrylate are added to the reaction system, stirred and dispersed for 30-50 min, the temperature of the reaction system is raised to 70-80 °C, an initiator solution is added dropwise to the reaction system, after the addition is completed, keep the temperature for reaction for 4-6 h, and then perform post-treatment to obtain the polyolefin resin.

[0009] The synthesis reaction formula of the polyolefin resin is:

[0010] Wherein:

[0011] 。

[0012] The synthesis reaction mechanism of the polyolefin resin is as follows:

[0013] During the reaction process, the initiator decomposes to generate active free radicals, and the active free radicals catalyze and activate the opening of the unsaturated double bonds on the filler, olefin-terminated polysiloxane, glycidyl methacrylate, styrene, and butyl acrylate molecules to form macromolecular free radicals, and then through random copolymerization to form a multi-block copolymer sequence, and the polyolefin resin is prepared.

[0014] Furthermore, the epoxy resin is bisphenol A type epoxy resin E-12, the curing agent is polyetheramine, and the auxiliary additive is composed of pigment, leveling agent, curing accelerator, and slip agent in a weight ratio of 5:1.5:0.6:2. Among them, the pigment is phthalocyanine pigment, the leveling agent is acrylate leveling agent, the curing accelerator is 2-methylimidazole, and the slip agent is polypropylene wax.

[0015] Furthermore, the dosage ratio of the solvent, emulsifier, activated filler, olefin-terminated polysiloxane, glycidyl methacrylate, styrene, butyl acrylate, and initiator solution is 150 mL:4 g:5 - 7 g:10 - 15 g:4 - 6 g:2 - 3 g:5 - 6 g:10 mL. The solvent is composed of deionized water and absolute ethanol in a volume ratio of 2:1. The emulsifier is composed of sodium dodecylbenzenesulfonate, sodium oleate, and Tween-80 in a weight ratio of 5:3:2. The initiator solution is composed of azobisisobutyronitrile and deionized water in a ratio of 1 g:20 mL. The post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, suction filtration is carried out, the filter cake is washed 3 - 5 times with purified water and then dried by suction, the filter cake is transferred to a drying oven at a temperature of 60 - 70 °C, and dried to constant weight to obtain the polyolefin resin.

[0016] Furthermore, the olefin-terminated polysiloxane is processed by the following steps:

[0017] A1. Under the protection of inert gas, stir 3,5-di-tert-butyl-4-hydroxybenzyl alcohol and tetrahydrofuran, raise the temperature of the reaction system to 40 - 50 °C, add 3-isocyanatopropylmethyldiethoxysilane to the reaction system, keep the temperature for reaction for 60 - 70 min, and perform post-treatment to obtain diethoxysilane-modified butylated hydroxytoluene;

[0018] A2. Mix D4, diethoxysilane-modified butylated hydroxytoluene, diphenyldiethoxysilane and a catalyst and stir. After the reaction system is sealed, raise the temperature of the reaction system to 120 - 130 °C, keep the temperature for reaction for 3 - 4 h, add diallyltetramethyldisiloxane to the reaction system, keep the temperature for reaction for 2 - 3 h, and perform post-treatment to obtain olefin-terminated polysiloxane.

[0019] The synthesis reaction formula of olefin-terminated polysiloxane is:

[0020] In the formula:

[0021] .

[0022] The synthesis reaction mechanism of olefin-terminated polysiloxane is:

[0023] During the reaction, the hydroxyl group of 3,5-di-tert-butyl-4-hydroxybenzyl alcohol molecule reacts with the isocyanate group on the 3-isocyanatopropylmethyldiethoxysilane molecule to carry out a condensation reaction, and diethoxysilane is modified on the 3,5-di-tert-butyl-4-hydroxybenzyl alcohol molecule to prepare diethoxysilane-modified butylated hydroxytoluene.

[0024] Under the action of the catalyst, while D4 opens the ring to form a siloxane chain, the siloxane bonds on the molecules of diethoxysilane-modified butylated hydroxytoluene and diphenyldiethoxysilane are hydrolyzed to form silanol groups, and dehydration condensation occurs between the silanol groups to form a long polysiloxane chain. Diallyltetramethyldisiloxane is hydrolyzed under the action of the catalyst to form allylsilane modified with monosilanol group, which acts as a capping agent to condense with the silanols at both ends of the long polysiloxane chain to form an olefin double bond modification, and olefin-terminated polysiloxane is prepared.

[0025] Furthermore, in step A1, the dosage ratio of 3,5-di-tert-butyl-4-hydroxybenzyl alcohol to 3-isocyanatopropylmethyldiethoxysilane is 1 mol:1 mol, and the dosage ratio of 3,5-di-tert-butyl-4-hydroxybenzyl alcohol to tetrahydrofuran is 1 g:7 mL. The post-treatment includes: after the reaction is completed, distill off the low-boiling substances under reduced pressure to obtain diethoxysilane-modified butylated hydroxytoluene.

[0026] Further, in step A2, the dosage ratio of D4, diethoxysilane-modified butylated hydroxytoluene, diphenyldiethoxysilane, catalyst, and diallyltetramethyldisiloxane is 10 g: 2 g: 3 g: 0.2 g: 0.8 g. The catalyst is a 60-75 wt% sulfuric acid solution. The post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, purified water is added to the reaction system, and it is stirred for 20-30 min. Then, a 0.5 mol / L aqueous sodium carbonate solution is added to the reaction system to adjust the pH of the system to 7. After standing for liquid separation, the upper layer liquid is washed 3 times with purified water and then transferred to a rotary evaporator at 80-90 °C to remove low-boiling substances under reduced pressure, obtaining an olefin-terminated polysiloxane.

[0027] Further, the preparation method of the activated filler is as follows: mix nano-titanium dioxide, nano-silicon dioxide, absolute ethanol, and KH-570, ultrasonically disperse for 80-120 min, raise the temperature of the reaction system to 50-60 °C, add a catalyst to the reaction system, keep the temperature for reaction for 40-60 min, and perform post-treatment to obtain the activated filler.

[0028] The synthesis reaction formula of the activated filler is:

[0029]

[0030] In the formula: is nano-titanium dioxide or nano-silicon dioxide particles.

[0031] The synthesis reaction mechanism of the activated filler is:

[0032] During the reaction, the catalyst catalyzes the hydrolysis of the siloxane bond on the KH-570 molecule to form silanol, and the silanol bonds with the siloxane bond on the surface of nano-silicon dioxide or nano-titanium dioxide particles to form an unsaturated double bond modification, thereby obtaining the activated filler.

[0033] Further, the dosage ratio of the nano-titanium dioxide, nano-silicon dioxide, absolute ethanol, KH-570, and catalyst is 2 g: 3 g: 30 mL: 1 g: 8 mL. The catalyst is a 2 mol / L sodium hydroxide solution. The post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, suction filtration is performed, the filter cake is washed with purified water until neutral and then dried by suction, and the filter cake is transferred to a drying oven at 65-75 °C and dried to a constant weight to obtain the activated filler.

[0034] A preparation method of an environment-friendly powder coating, wherein the preparation method of the environment-friendly powder coating is as follows: add a polyolefin resin, an epoxy resin, a curing agent, and an auxiliary additive to a high-speed grinder, crush and pass through a 200-300 mesh sieve to obtain the powder coating.

[0035] Application of an environment-friendly powder coating: The powder coating prepared according to a preparation method of an environment-friendly powder coating is applied to the surface coating of metal products.

[0036] The present invention has the following beneficial effects:

[0037] For the environment-friendly powder coating of the present invention, in a water-emulsified environment, through free radical polymerization reaction, it promotes the polymerization of activated filler, olefin-terminated polysiloxane, glycidyl methacrylate, styrene and butyl acrylate to form polyolefin resin, and then bisphenol A epoxy resin is used to enhance it and cooperate with curing agent and auxiliary additives to prepare the powder coating. During the preparation process, raw materials containing primary flammable solvents such as benzene, toluene, and ethylbenzene that can release a large amount of volatile organic compounds are avoided, reducing the harm to the environment and human health. The benzene ring and ether bond in the molecular structure of bisphenol A epoxy resin can effectively absorb the energy of ultraviolet rays and form a chemical bonding effect with the surface of the substrate, enhancing the adhesion and anti-ultraviolet performance between the coating and the substrate. The saturated single bond structure in the molecular chain of polyolefin resin endows it with high chemical stability and mechanical strength. Polysiloxane enhances the flexibility of the powder coating. After the powder coating is cured, the polar groups in its coating can form intermolecular forces such as hydrogen bonds and van der Waals forces with the surface of the substrate, significantly enhancing the adhesion grade of the coating film. The flexibility of the powder coating helps the coating film to form a continuous and uniform coating on the surface of the substrate, increasing the contact area between the coating film and the substrate, thereby enhancing the adhesion grade. Moreover, the filler particles cooperate with polyolefin to construct a good wear-resistant reinforcement system, improving the wear resistance of the powder coating film.

[0038] For the environment-friendly powder coating of the present invention, by modifying olefin double bonds on the polysiloxane molecular chain, the olefin-terminated polysiloxane undergoes free radical copolymerization with the double bonds in the polyolefin resin through the terminal olefin groups, forming an organic-inorganic hybrid crosslinked network, thereby significantly improving the hardness and anti-deformation ability of the coating. The polysiloxane chain segments are evenly dispersed in the resin matrix, dispersing the external force impact through the Si-O bond, reducing local stress concentration, and lowering the wear rate. The bond energy of the Si-O bond in the main chain of polysiloxane is much higher than that of the C-C bond, and the Si-O bond has low sensitivity to UV radiation. By introducing butylated hydroxytoluene as an ultraviolet absorber on the polysiloxane chain, it can effectively resist the chain-breaking reaction induced by ultraviolet rays and delay the aging of the coating. By introducing a benzene ring structure on the polysiloxane chain, the energy is dispersed and absorbed through the π-electron conjugate system, reducing the influence of ultraviolet rays on the coating. Moreover, the benzene ring increases the rigidity of the polysiloxane chain, forming a rigid support on the polysiloxane chain, enabling it to better absorb and disperse energy when subjected to impact force, thereby improving the impact resistance.

[0039] The environmentally friendly powder coating of the present invention modifies and activates the surfaces of nano-silica and nano-titanium dioxide particles, modifies olefin double bonds on their surfaces, can increase the dispersibility of the activated filler during the synthesis of polyolefin resin, improve its surface activity at the same time, and uses the olefin double bonds modified on the activated filler particles as active reaction sites to increase the crosslinking degree of the polyolefin resin. The three-dimensional network structure formed by the crosslinking bonding can effectively dissipate impact energy. When the material is impacted, the crosslinking points can prevent the expansion of cracks. At the same time, the bridging effect of the nano-filler can further absorb energy, improving the wear resistance and impact resistance of the powder coating specimen. Nano-titanium dioxide in the activated filler has excellent light shielding performance, can effectively absorb and reflect ultraviolet rays, reduce the direct irradiation of ultraviolet rays on the polyolefin resin, thereby reducing the photo-oxidative degradation rate, and cooperating with the olefin-capped polysiloxane, improving the anti-ultraviolet aging performance of the material. Detailed implementation mode

[0040] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

[0041] In this application, D4 is octamethylcyclotetrasiloxane, and its CAS number is 556-67-2;

[0042] In this application, the nano-titanium dioxide is selected from Qinghe County Chaotai Metal Materials Co., Ltd., the effective ingredient content is 99%, and the particle size is 2000 mesh;

[0043] In this application, the nano-silica is selected from Qinghe County Chaotai Metal Materials Co., Ltd., the silicon content ≥ 99.9%, the particle size is 2000 mesh, and the purity is 99.9%;

[0044] In this application, the acrylate leveling agent is octadecyl acrylate, and the effective ingredient content is 99%;

[0045] In this application, the polypropylene wax is selected from Shanghai Hongzhuang Chemical Technology Co., Ltd., the effective ingredient content is 99%, and the model is CS-52NC;

[0046] In this application, the polyetheramine is selected from Shanghai Yushicheng Chemical Technology Co., Ltd., the product name is BASF polyetheramine D230, and the model is BASGU EC301.

[0047] Example 1. This example provides a preparation method of an environmentally friendly powder coating, including the following steps:

[0048] S1. Prepare diethoxysilane-modified butylated hydroxytoluene;

[0049] Weigh: 23.6 g of 3,5 - di - tert - butyl - 4 - hydroxybenzyl alcohol and 165.2 mL of tetrahydrofuran are added to a 500 - mL reaction flask under nitrogen protection and stirred. The temperature of the reaction flask is raised to 40 °C, and 21.7 g of 3 - isocyanatopropylmethyldiethoxysilane is added to the reaction flask. Keep the temperature for reaction for 60 min, evacuate the reaction flask to a negative pressure of 0.1 MPa, and remove the low - boiling substances under reduced pressure to obtain diethoxysilane - modified butylated hydroxytoluene.

[0050] S2. Prepare olefin - terminated polysiloxane;

[0051] Weigh: 200 g of D4, 40 g of diethoxysilane - modified butylated hydroxytoluene, 60 g of diphenyldiethoxysilane, and 4 g of 60 wt% sulfuric acid solution are added to a 500 - mL reaction flask and stirred. After the reaction flask is sealed, the temperature of the reaction flask is raised to 120 °C, and keep the temperature for reaction for 3 h. Then 16 g of diallyltetramethyldisiloxane is added to the reaction flask, and keep the temperature for reaction for 2 h. The temperature of the reaction flask is lowered to room temperature, 200 mL of purified water is added to the reaction flask, and stirred for 20 min. 0.5 mol / L sodium carbonate aqueous solution is added to the reaction system to adjust the pH of the system to 7. Let it stand and separate the liquid. The upper - layer liquid is washed 3 times with purified water and then transferred to a rotary evaporator at 80 °C to remove the low - boiling substances under reduced pressure to obtain olefin - terminated polysiloxane.

[0052] S3. Prepare activated filler;

[0053] Weigh: 10 g of nano - titanium dioxide, 15 g of nano - silicon dioxide, 150 mL of absolute ethanol, and 5 g of KH - 570 are added to a 500 - mL reaction flask, and ultrasonically dispersed for 80 min. The reaction flask is fixed in a water - bath with mechanical stirring and stirred. The temperature of the reaction flask is raised to 50 °C, and 40 mL of 2 mol / L sodium hydroxide solution is added to the reaction flask. Keep the temperature for reaction for 40 min. The temperature of the reaction flask is lowered to room temperature, filtered by suction. The filter cake is washed with purified water until neutral and then dried by suction. The filter cake is transferred to a drying oven at 65 °C and dried to constant weight to obtain activated filler.

[0054] S4. Prepare polyolefin resin;

[0055] Mix deionized water and absolute ethanol evenly according to a volume ratio of 2:1 to obtain a solvent;

[0056] Mix sodium dodecylbenzenesulfonate, sodium oleate, and Tween - 80 evenly according to a weight ratio of 5:3:2 to obtain an emulsifier;

[0057] Mix azobisisobutyronitrile and deionized water at 1 g:20 mL and stir until the system is dissolved to obtain an initiator solution;

[0058] Under the protection of inert gas,

[0059] Weigh: 1500 mL of solvent and 40 g of emulsifier are added to a 3 L reaction flask and stirred. Set the stirring speed to 600 r / min. Then, 50 g of activated filler, 100 g of olefin-terminated polysiloxane, 40 g of glycidyl methacrylate, 20 g of styrene, and 50 g of butyl acrylate are successively added to the reaction flask. Stir and disperse for 30 min. Raise the temperature of the reaction flask to 70 °C. Dropwise add 100 mL of initiator solution to the reaction flask. After the addition is complete, keep the reaction at a constant temperature for 4 h. Lower the temperature of the reaction flask to room temperature. Filter by suction. Wash the filter cake with purified water 3 times and then drain it by suction. Transfer the filter cake to a drying oven at 60 °C and dry to a constant weight to obtain polyolefin resin.

[0060] S5. Prepare powder coating;

[0061] Mix phthalocyanine pigment, acrylate leveling agent, curing accelerator 2-methylimidazole, and slip agent polypropylene wax evenly according to the weight ratio of 5:1.5:0.6:2 to obtain auxiliary additive;

[0062] Weigh by weight: 70 parts of polyolefin resin, 15 parts of bisphenol A epoxy resin E-12, 5 parts of curing agent polyetheramine, and 3 parts of auxiliary additive are added to a high-speed grinder, crushed through a 200-mesh sieve to obtain powder coating.

[0063] Example 2. This example provides a preparation method of an environment-friendly powder coating, including the following steps:

[0064] S1. Prepare diethoxysilane-modified butylated hydroxytoluene;

[0065] Weigh: 23.6 g of 3,5-di-tert-butyl-4-hydroxybenzyl alcohol and 165.2 mL of tetrahydrofuran are added to a 500 mL reaction flask under nitrogen protection and stirred. Raise the temperature of the reaction flask to 45 °C. Add 21.7 g of 3-isocyanatopropylmethyldiethoxysilane to the reaction flask. Keep the reaction at a constant temperature for 65 min. Draw a negative pressure in the reaction flask to 0.1 MPa and reduce the pressure to remove low-boiling substances to obtain diethoxysilane-modified butylated hydroxytoluene.

[0066] S2. Prepare olefin-terminated polysiloxane;

[0067] Weigh: 200 g of D4, 40 g of diethoxysilane-modified butylated hydroxytoluene, 60 g of diphenyldiethoxysilane and 4 g of 68 wt% sulfuric acid solution and add them to a 500 mL reaction flask and stir. After the reaction flask is sealed, the temperature of the reaction flask is raised to 125 °C and the reaction is carried out under insulation for 3.5 h. Then add 16 g of diallyltetramethyldisiloxane to the reaction flask and carry out the reaction under insulation for 2.5 h. Then lower the temperature of the reaction flask to room temperature, add 200 mL of purified water to the reaction flask and stir for 25 min. Add 0.5 mol / L sodium carbonate aqueous solution to the reaction system to adjust the pH of the system to 7, let it stand and separate the liquid. The upper layer liquid is washed 3 times with purified water and then transferred to a rotary evaporator at 85 °C to remove low-boiling substances under reduced pressure to obtain an olefin-terminated polysiloxane.

[0068] S3. Prepare activated filler;

[0069] Weigh: 10 g of nano-titanium dioxide, 15 g of nano-silica, 150 mL of anhydrous ethanol and 5 g of KH-570 and add them to a 500 mL reaction flask, and perform ultrasonic dispersion for 100 min. Fix the reaction flask in a water bath with mechanical stirring and stir. Raise the temperature of the reaction flask to 55 °C, add 40 mL of 2 mol / L sodium hydroxide solution to the reaction flask, and carry out the reaction under insulation for 50 min. Then lower the temperature of the reaction flask to room temperature, carry out suction filtration, wash the filter cake with purified water until neutral and then dry it by suction. Transfer the filter cake to a drying oven at 70 °C and dry it to constant weight to obtain the activated filler.

[0070] S4. Prepare polyolefin resin;

[0071] Mix deionized water and anhydrous ethanol evenly according to a volume ratio of 2:1 to obtain a solvent;

[0072] Mix sodium dodecylbenzenesulfonate, sodium oleate and Tween-80 evenly according to a weight ratio of 5:3:2 to obtain an emulsifier;

[0073] Mix azobisisobutyronitrile and deionized water at 1 g:20 mL and stir until the system is dissolved to obtain an initiator solution;

[0074] Under the protection of inert gas,

[0075] Weigh: Add 1500 mL of solvent and 40 g of emulsifier to a 3 L reaction flask and stir. Set the stirring speed to 700 r / min. Add 60 g of activated filler, 130 g of olefin-terminated polysiloxane, 50 g of glycidyl methacrylate, 25 g of styrene and 55 g of butyl acrylate to the reaction flask in sequence, stir and disperse for 40 min. Raise the temperature of the reaction flask to 75 °C, add 100 mL of the initiator solution dropwise to the reaction flask. After the dropwise addition is completed, carry out the reaction under insulation for 5 h. Then lower the temperature of the reaction flask to room temperature, carry out suction filtration, wash the filter cake 4 times with purified water and then dry it by suction. Transfer the filter cake to a drying oven at 65 °C and dry it to constant weight to obtain the polyolefin resin.

[0076] S5. Prepare powder coatings;

[0077] Mix phthalocyanine pigments, acrylate leveling agents, curing accelerator 2-methylimidazole, and slip agent polypropylene wax evenly according to a weight ratio of 5:1.5:0.6:2 to obtain auxiliary additives;

[0078] Weigh by parts: 75 parts of polyolefin resin, 20 parts of bisphenol A epoxy resin E-12, 5.5 parts of curing agent polyetheramine, and 4 parts of auxiliary additives, add them to a high-speed grinder, pulverize through a 250-mesh sieve to obtain powder coatings.

[0079] Example 3. This example provides a preparation method of an environment-friendly powder coating, including the following steps:

[0080] S1. Prepare diethoxysilane-modified butylated hydroxytoluene;

[0081] Weigh: 23.6 g of 3,5-di-tert-butyl-4-hydroxybenzyl alcohol and 165.2 mL of tetrahydrofuran, add them to a 500 mL reaction flask under nitrogen protection and stir. Raise the temperature of the reaction flask to 50 °C, add 21.7 g of 3-isocyanatopropylmethyldiethoxysilane to the reaction flask, keep the temperature for reaction for 70 min, evacuate the reaction flask to a negative pressure of 0.1 MPa, and remove low-boiling substances under reduced pressure to obtain diethoxysilane-modified butylated hydroxytoluene.

[0082] S2. Prepare olefin-terminated polysiloxane;

[0083] Weigh: 200 g of D4, 40 g of diethoxysilane-modified butylated hydroxytoluene, 60 g of diphenyldiethoxysilane, and 4 g of 75 wt% sulfuric acid solution, add them to a 500 mL reaction flask and stir. After sealing the reaction flask, raise the temperature of the reaction flask to 130 °C, keep the temperature for reaction for 4 h, add 16 g of diallyltetramethyldisiloxane to the reaction flask, keep the temperature for reaction for 3 h, lower the temperature of the reaction flask to room temperature, add 200 mL of purified water to the reaction flask, stir for 30 min, add 0.5 mol / L sodium carbonate aqueous solution to the reaction system to adjust the pH of the system to 7, let it stand for liquid separation, wash the upper layer liquid with purified water 3 times and then transfer it to a rotary evaporator at 90 °C, and remove low-boiling substances under reduced pressure to obtain olefin-terminated polysiloxane.

[0084] S3. Prepare activated fillers;

[0085] Weigh: 10 g of nano-titanium dioxide, 15 g of nano-silica, 150 mL of absolute ethanol, and 5 g of KH-570 into a 500 mL reaction flask, ultrasonically disperse for 120 min, fix the reaction flask in a water bath with mechanical stirring and stir. Raise the temperature of the reaction flask to 60 °C, add 40 mL of 2 mol / L sodium hydroxide solution to the reaction flask, keep the temperature for reaction for 60 min, lower the temperature of the reaction flask to room temperature, filter by suction, wash the filter cake with purified water until neutral and then drain it by suction. Transfer the filter cake to a drying oven at 75 °C and dry to constant weight to obtain the activated filler.

[0086] S4. Prepare polyolefin resin;

[0087] Mix deionized water and absolute ethanol evenly according to the volume ratio of 2:1 to obtain a solvent;

[0088] Mix sodium dodecylbenzenesulfonate, sodium oleate, and Tween-80 evenly according to the weight ratio of 5:3:2 to obtain an emulsifier;

[0089] Mix azobisisobutyronitrile and deionized water at 1 g:20 mL and stir until the system is dissolved to obtain an initiator solution;

[0090] Under the protection of inert gas,

[0091] Weigh: 1500 mL of solvent and 40 g of emulsifier into a 3 L reaction flask and stir. Set the stirring speed to 800 r / min. Add 70 g of activated filler, 150 g of olefin-terminated polysiloxane, 60 g of glycidyl methacrylate, 30 g of styrene, and 60 g of butyl acrylate to the reaction flask in sequence, stir and disperse for 50 min, raise the temperature of the reaction flask to 80 °C, add 100 mL of the initiator solution dropwise to the reaction flask. After the dropping is completed, keep the temperature for reaction for 6 h, lower the temperature of the reaction flask to room temperature, filter by suction, wash the filter cake with purified water 5 times and then drain it by suction. Transfer the filter cake to a drying oven at 70 °C and dry to constant weight to obtain the polyolefin resin.

[0092] S5. Prepare powder coatings;

[0093] Mix phthalocyanine pigments, acrylate leveling agents, curing accelerator 2-methylimidazole, and slip agent polypropylene wax evenly according to the weight ratio of 5:1.5:0.6:2 to obtain auxiliary additives;

[0094] Weigh by weight: 80 parts of polyolefin resin, 25 parts of bisphenol A epoxy resin E-12, 6 parts of curing agent polyetheramine, and 5 parts of auxiliary additives into a high-speed grinder, crush and pass through a 300-mesh sieve to obtain powder coatings.

[0095] Comparative Example 1. The difference between this comparative example and Example 3 is that diphenyldiethoxysilane was not added in step S2.

[0096] Comparative Example 2. The difference between this comparative example and Example 3 is that step S3 is cancelled, and the mixture composed of nano-titanium dioxide and nano-silica in a weight ratio of 2:3 in step S3 is used to replace the activated filler in step S4.

[0097] Comparative Example 3. The difference between this comparative example and Example 3 is that styrene is not added in step S4.

[0098] Comparative Example 4. The difference between this comparative example and Example 3 is that bisphenol A epoxy resin E-12 in step S5 is replaced by diglycidyl ether with equal epoxy equivalent.

[0099] Performance test:

[0100] The powder coatings prepared in Examples 1-3 and Comparative Examples 1-4 were evenly sprayed on the polished and degreased tinplate to form a sprayed coating with a thickness of 100 μm on the tinplate, and then thermally cured at 200 °C for 15 min to obtain the test specimens to be tested;

[0101] Refer to the standard GB / T 23988-2009 "Determination of abrasion resistance of coatings - Falling sand method" to determine the abrasion resistance of the test specimens to be tested;

[0102] Refer to the standard GB / T 9286-2021 "Paints and varnishes - Cross-cut test" to determine the adhesion of the test specimens to be tested;

[0103] Refer to the standard GB / T 23987-2009 "Paints and varnishes - Exposure of coatings to artificial weathering - Exposure to fluorescent ultraviolet light and water" to expose the test specimens to ultraviolet light with a wavelength of 300-320 nm for cyclic irradiation for 360 h. The cyclic irradiation conditions are: set the blackboard temperature to 50 °C, relative humidity to 15%, dry irradiation for 5 h, and then water spray at a black and white temperature of 25 °C and wet irradiation for 1 h. Refer to the standard GB / T 1766-2008 "Paints and varnishes - Rating method for degradation of coatings" to evaluate the loss of gloss rate of the test specimens to be tested;

[0104] Refer to the standard GB / T 1732-2020 "Method for determination of impact resistance of paint films" to determine the maximum height of film breakage of the test specimens to be tested;

[0105] The specific test results are shown in Table 1 below.

[0106] Table 1 - Data table of performance detection of specimens

[0107]

[0108] Data analysis:

[0109] Comparing and analyzing the data in Table 1 above, after the powder coating prepared by the present invention is thermally cured, the abrasion resistance of the paint film reaches 5.4 L / μm, the loss of gloss rate is reduced to 1.5%, the adhesion grade reaches level 0, and the maximum height of the paint film breakage reaches 45 cm. All the performance test data are better than those of the comparative example, indicating that the present invention enhances unsaturated monomers through activated fillers and olefin-terminated polysiloxanes to prepare polyolefin resins, and then enhances the polyolefin resins with epoxy resins, which not only effectively improves the abrasion resistance and impact resistance of the paint film layer specimens, but also improves the adhesion and anti-ultraviolet performance of the paint film, and the production process has little harm to the environment and human health and is relatively friendly to the environment.

[0110] The above content is only an example and explanation of the structure of the present invention. Those skilled in the art of the present technology can make various modifications or supplements to the described specific embodiments or use similar methods for substitution, as long as they do not deviate from the structure of the invention or exceed the scope defined by this claim book, they should fall within the protection scope of the present invention.

[0111] In the description of this specification, the descriptions with reference to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0112] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not elaborate all the details, nor limit the present invention to only the specific implementation manners. Obviously, according to the content of this specification, many modifications and changes can be made. This specification selects and specifically describes these embodiments to better explain the principle and practical application of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claim book and its full scope and equivalents.

Claims

1. An environmentally friendly powder coating, characterized in that, It comprises the following components by weight parts: 70 - 80 parts of polyolefin resin, 15 - 25 parts of epoxy resin, 5 - 6 parts of curing agent, and 3 - 5 parts of auxiliary additive; The preparation method of the polyolefin resin is as follows: Under the protection of inert gas, mix and stir the solvent and emulsifier, add activated filler, olefin - terminated polysiloxane, glycidyl methacrylate, styrene, and butyl acrylate into the reaction system, stir and disperse for 30 - 50 min, raise the temperature of the reaction system to 70 - 80 °C, dropwise add the initiator solution into the reaction system. After the dropping is completed, keep the temperature for reaction for 4 - 6 h, and perform post - treatment to obtain the polyolefin resin; The olefin - terminated polysiloxane is obtained by the following processing steps: A1. Under the protection of inert gas, mix and stir 3,5 - di - tert - butyl - 4 - hydroxybenzyl alcohol and tetrahydrofuran, raise the temperature of the reaction system to 40 - 50 °C, add 3 - isocyanatopropylmethyldiethoxysilane into the reaction system, keep the temperature for reaction for 60 - 70 min, and perform post - treatment to obtain diethoxysilane - modified butylated hydroxytoluene; A2. Mix and stir D4, diethoxysilane - modified butylated hydroxytoluene, diphenyldiethoxysilane, and catalyst. After the reaction system is sealed, raise the temperature of the reaction system to 120 - 130 °C, keep the temperature for reaction for 3 - 4 h, add diallyltetramethyldisiloxane into the reaction system, keep the temperature for reaction for 2 - 3 h, and perform post - treatment to obtain the olefin - terminated polysiloxane; The preparation method of the activated filler is as follows: Mix nano - titanium dioxide, nano - silicon dioxide, absolute ethanol, and KH - 570, ultrasonically disperse for 80 - 120 min, raise the temperature of the reaction system to 50 - 60 °C, add a catalyst into the reaction system, keep the temperature for reaction for 40 - 60 min, and perform post - treatment to obtain the activated filler.

2. The environmentally friendly powder coating according to claim 1, wherein The epoxy resin is bisphenol A epoxy resin E - 12, the curing agent is polyetheramine, and the auxiliary additive is composed of pigment, leveling agent, curing accelerator, and slip agent according to the weight ratio of 5:1.5:0.6:

2. Among them, the pigment is phthalocyanine pigment, the leveling agent is acrylate leveling agent, the curing accelerator is 2 - methylimidazole, and the slip agent is polypropylene wax.

3. An environment-friendly powder coating according to claim 1, characterized in that, The dosage ratio of the solvent, emulsifier, activated filler, olefin - terminated polysiloxane, glycidyl methacrylate, styrene, butyl acrylate, and initiator solution is 150 mL:4 g:5 - 7 g:10 - 15 g:4 - 6 g:2 - 3 g:5 - 6 g:10 mL. The solvent is composed of deionized water and absolute ethanol according to the volume ratio of 2:

1. The emulsifier is composed of sodium dodecylbenzenesulfonate, sodium oleate, and Tween - 80 according to the weight ratio of 5:3:

2. The initiator solution is composed of azobisisobutyronitrile and deionized water according to 1 g:20 mL. The post - treatment includes: After the reaction is completed, lower the temperature of the reaction system to room temperature, perform suction filtration. The filter cake is washed with purified water 3 - 5 times and then dried by suction. The filter cake is transferred to an oven at 60 - 70 °C and dried to constant weight to obtain the polyolefin resin.

4. An environment-friendly powder coating according to claim 1, characterized in that In step A1, the dosage ratio of 3,5-di-tert-butyl-4-hydroxybenzyl alcohol to 3-isocyanatopropylmethyldiethoxysilane is 1 mol:1 mol, and the dosage ratio of 3,5-di-tert-butyl-4-hydroxybenzyl alcohol to tetrahydrofuran is 1 g:7 mL. The post-treatment includes: after the reaction is completed, low-boiling substances are removed under reduced pressure to obtain diethoxysilane-modified butylated hydroxytoluene. In step A2, the dosage ratio of D4, diethoxysilane-modified butylated hydroxytoluene, diphenyldiethoxysilane, catalyst, and diallyltetramethyldisiloxane is 10 g:2 g:3 g:0.2 g:0.8 g. The catalyst is a 60-75 wt% sulfuric acid solution. The post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, purified water is added to the reaction system, and it is stirred for 20-30 min. An aqueous sodium carbonate solution with a concentration of 0.5 mol / L is added to the reaction system to adjust the pH of the system to 7. It is left to stand for liquid separation. The upper layer liquid is washed 3 times with purified water and then transferred to a rotary evaporator at a temperature of 80-90 °C, and low-boiling substances are removed under reduced pressure to obtain olefin-terminated polysiloxane.

5. An environment-friendly powder coating according to claim 1, characterized in that, The dosage ratio of the nano-titanium dioxide, nano-silicon dioxide, absolute ethanol, KH-570, and catalyst is 2 g:3 g:30 mL:1 g:8 mL. The catalyst is a 2 mol / L sodium hydroxide solution. The post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, suction filtration is carried out, the filter cake is washed with purified water until neutral and then dried by suction. The filter cake is transferred to a drying oven at a temperature of 65-75 °C and dried to a constant weight to obtain activated filler.

6. A preparation method of an environment-friendly powder coating as described in any one of claims 1-5, characterized in that, The preparation method of the environment-friendly powder coating is as follows: polyolefin resin, epoxy resin, curing agent, and auxiliary additives are added to a high-speed grinder, pulverized, and passed through a 200-300 mesh sieve to obtain powder coating.

7. Application of an environment-friendly powder coating, characterized in that, The powder coating prepared by the preparation method of an environment-friendly powder coating according to claim 6 is applied to the surface coating of metal products.

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