A water-based two-component polyurethane coating

Abstract

The present invention provides a water-based two-component polyurethane coating, wherein (Cd-Fe)O x @SiO2 filler is suspendable in water and is highly dispersed in the polyurethane coating. It has good coating compatibility and significantly improves the physical and chemical properties of polyurethane, such as tensile strength. The filler also improves the corrosion resistance of the coating and increases the service life of the magnetic coating.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings, and in particular relates to a two-component water-based coating filler, a polyurethane composite coating and a preparation method thereof. Background Art

[0002] Waterborne polyurethane refers to a polyurethane emulsion containing polyurethane dispersed in water as a solvent. Solvent-based polyurethanes are widely used, but the use of organic solvents can cause air pollution and be toxic. In recent years, increasing concern for environmental issues has driven the development and research of waterborne polyurethanes. Waterborne polyurethanes are widely used in adhesives, coatings, and other fields, attracting attention for their environmental friendliness and safety. Polyurethanes are characterized by excellent wear resistance, high load-bearing capacity, high tear strength, and resistance to low temperatures, oils, and ozone. Combined with their diverse raw materials and adjustable molecular structure, these advantages have further expanded their application in industries such as elastomers, foams, coatings, and adhesives. However, polyurethanes do have their own drawbacks, such as poor solvent resistance, weather resistance, and heat resistance, which significantly limit their application in coatings. Currently, waterborne polyurethane modification methods can be categorized by the type of modifier: acrylic acid modification, epoxy resin modification, polysiloxane modification, and natural product modification. Recently, polymer composites have attracted great attention. Inorganic nanoparticles can improve the mechanical properties, optical properties, thermal properties, corrosion resistance, magnetic properties, etc. of polymer materials.

[0003] Magnetic nanoparticles have potential applications in biomedicine, industry, and the military due to their inherent magnetic properties, microstructure, large surface area, surface charge, and low toxicity. Due to its biocompatibility and chemical stability, ferroferric oxide has attracted considerable attention for use in targeted drug delivery systems. Various approaches have been employed to develop this material. Due to its hydrophobic nature, magnetic materials can readily aggregate. Surface modification can improve nanoparticle stability and provide additional functional groups that may be useful in other applications. One approach to preventing nanoparticle agglomeration is to coat the surface with a water-soluble material. This material typically consists of a core of ferroferric oxide coated with a shell of another material. Common coating materials include metal oxides or other inorganic materials, such as titanium dioxide, silicon dioxide, aluminum oxide, and zirconium dioxide. The use of silicon dioxide and its derivatives on the surface of magnetic nanoparticles may improve their surface properties. Because silicon dioxide is an inert compound, it offers excellent acid and alkali resistance and high-temperature stability. At the same time, silicon dioxide has high transmittance in the ultraviolet region, so it can be used in anti-reflection materials, and compounding with ferrosoferric oxide can achieve stronger electromagnetic loss performance.

[0004] For example, CN102807775B discloses a method for preparing waterproof and oil-proof magnetic SiO2 / Fe3O4 composite particles, comprising: dissolving FeCl2·4H2O, Na2SO3, polyvinyl pyrrolidone, and NaOH in deionized water, reacting at 100°C to 180°C for 8 to 16 hours, separating, washing, and drying to obtain Fe3O4 particles; uniformly dispersing the Fe3O4 particles in ethanol, adding ammonia water, adding ethyl orthosilicate while stirring, continuing stirring at 5°C to 50°C for 8 to 16 hours, separating, washing, and drying to obtain waterproof and oil-proof magnetic SiO2 / Fe3O4 composite particles. The product is prepared by coating with fluorosilane to improve performance. The production process is simple, highly feasible, and has a high yield. The waterproof and oil-proof magnetic SiO2 / Fe3O4 composite particles or products of the present invention have good waterproof and oil-proof properties and can be widely used in coatings, medical machinery, steel corrosion protection, and other fields.

[0005] Such as CN109627906B a kind of super-hydrophobic graphene anticorrosion coating of double-layer intermingled structure and preparation method thereof, belong to super-hydrophobic anticorrosion coating technical field, can solve current super-hydrophobic coating structure and performance instability, super-hydrophobic coating anticorrosion performance is poor, and can not be prepared on a large scale and other problems. The present invention comprises the following steps: first, synthesize a kind of nanoparticle oily dispersion with low surface energy, and the graphene / resin composite oily dispersion with good dispersibility;Secondly, graphene / resin composite oily dispersion and nanoparticle oily dispersion are sprayed on metal substrate successively, prepare the coating of double-layer intermingled structure.Relative traditional super-hydrophobic anticorrosion coating, hydrophobicity and anticorrosion performance are more excellent, surface structure and performance are more stable, and can be prepared in a large area, accelerate the engineering application of super-hydrophobic coating in anticorrosion field. Summary of the Invention

[0006] The present invention provides a water-based two-component polyurethane coating. Corrosion-resistant cadmium-doped Fe3O4 nanosphere particles are prepared under harsh (extremely high temperature) hydrothermal conditions. High-purity magnetic particles are then obtained by acid washing, activation, and impurity removal. The magnetic nanospheres are used as cores, and silica shells are directionally adsorbed on their surfaces to obtain a highly suspended, highly compatible, and stable magnetic suspension. When used as a filler in a water-based coating, the filler is highly dispersed in the coating, and the coating has good physical and chemical properties, such as tensile strength and corrosion resistance.

[0007] A method for preparing a two-component water-based paint filler comprises the following steps:

[0008] (1) Add 5-8mM FeCl3 . 6H2O, 0.5-1 mM CdCl2 .6H2O metal salt is added to an ethanol-deionized water solution, stirred evenly, and then 3-4 g / L tetrahydroxypropylethylenediamine and 1-2 g / L ethylenediaminetetraacetic acid composite complexing agent are added in sequence. Then, 0.02-0.04 g / L 2,2'-bipyridine is added as a stabilizer and 10-15 mL NaBH4 is added as a reducing agent. After stirring evenly, sodium acetate is used as an alkaline source and the pH is adjusted to 7.5-8.5 to obtain a precursor solution.

[0009] (2) Place the above-mentioned precursor solution in an unlined stainless steel hydrothermal reactor, use nitrogen to expel the air in the reactor, then seal the reactor, heat it to 300-310℃ at 5-10℃ / min, keep it warm for 24-48h, and cool it naturally to room temperature.

[0010] (3) Magnetic separation of hydrothermal products and activation and acid washing purification: The activation and acid washing purification is to place the magnetic separation hydrothermal products in a mixed solution of 98wt.% H2SO4 and 30wt.% H2O2 with a volume ratio of 1-2:1 for 2-3 minutes at a temperature of 30°C and stirring with a motor. After activation and acid washing purification, the products are repeatedly washed with deionized water and ethanol in sequence until neutral, and a 10-20wt.% magnetic particle suspension is prepared. The solvent of the suspension consists of a polyether-modified silicone wetting agent, ethanol and deionized water.

[0011] (4) Add ammonia water to the magnetic particle suspension prepared in step (3), stir for 10-20 minutes, add ethyl silicate, stir with a motor for 12-14 hours at a temperature of 10-14°C, then filter, wash, and vacuum dry the product to obtain (Cd-Fe)O x @SiO2 filler.

[0012] In certain embodiments, the content of the polyether-modified silicone wetting agent is 4-5 wt.%.

[0013] In certain embodiments, the volume ratio of ethanol to deionized water in step (1) and step (3) is 1:7-9.

[0014] In some embodiments, the saturation magnetic intensity of the magnetic particles after activation and acid washing purification in step (3) is 62.7emu / g, the remanence is 4.23emu / g, and the coercive force is Hc=41.8G.

[0015] In certain embodiments, (Cd-Fe)O x The saturation magnetic intensity of SiO2 filler is 25.3 emu / g.

[0016] In certain embodiments, the amount of ethyl silicate used is 3-4 g, and the amount of ammonia water used is 5-8 mL.

[0017] In certain embodiments, (Cd-Fe)O x The core size is 20-70 nm, and the thickness of the SiO2 shell is 10-30 nm.

[0018] In certain embodiments, the (Cd-Fe)O x @SiO2 filler is ultrasonically dispersed in deionized water containing a wetting agent, (Cd-Fe)O x @The mass concentration of SiO2 is 40-50wt%, and the mass concentration of the wetting agent is 1-2wt.%.

[0019] A method for preparing a two-component water-based coating comprises the following steps:

[0020] (A) Preparation of Component A: After uniformly mixing the water-based hydroxylated acrylic resin, wetting and dispersing agent, defoaming agent, leveling agent, and deionized water according to the formula, add the filler suspension and mix at a high speed of 800-1200 rpm. Then, add the cosolvent and thixotropic thickener and mix at a medium speed of 600-800 rpm.

[0021] (B) Preparation method of component B: fully mix the hydrophilic modified isocyanate curing agent and propylene glycol diacetate to prepare the same.

[0022] (C) When using, mix component A and component B in a mass ratio of (5.5-10):1, and then spray it on the surface of the substrate.

[0023] The filler suspension is prepared by the following steps.

[0024] (1) Add 5-8mM FeCl3 . 6H2O, 0.5-1 mM CdCl2 . 6H2O metal salt is added to an ethanol-deionized water solution, stirred evenly, and then 3-4 g / L tetrahydroxypropylethylenediamine and 1-2 g / L ethylenediaminetetraacetic acid composite complexing agent are added in sequence. Then, 0.02-0.04 g / L 2,2'-bipyridine is added as a stabilizer and 10-15 mL NaBH4 is added as a reducing agent. After stirring evenly, sodium acetate is used as an alkaline source and the pH is adjusted to 7.5-8.5 to obtain a precursor solution.

[0025] (2) Place the above-mentioned precursor solution in an unlined stainless steel hydrothermal reactor, use nitrogen to expel the air in the reactor, then seal the reactor, heat it to 300-310℃ at 5-10℃ / min, keep it warm for 24-48h, and cool it naturally to room temperature.

[0026] (3) Magnetic separation of hydrothermal products and activation and acid washing purification: The activation and acid washing purification is to place the magnetic separation hydrothermal products in a mixed solution of 98wt.% H2SO4 and 30wt.% H2O2 with a volume ratio of 1-2:1 for 2-3 minutes at a temperature of 30°C and stirring with a motor. After activation and acid washing purification, the products are repeatedly washed with deionized water and ethanol in sequence until neutral, and a 10-20wt.% magnetic particle suspension is prepared. The solvent of the suspension consists of a polyether-modified silicone wetting agent, ethanol and deionized water.

[0027] (4) Add ammonia water to the magnetic particle suspension prepared in step (3), stir for 10-20 minutes, add ethyl silicate, stir with a motor for 12-14 hours at a temperature of 10-14°C, then filter, wash, and vacuum dry the product to obtain (Cd-Fe)O x @SiO2 filler, the (Cd-Fe)O x @SiO2 filler is ultrasonically dispersed in deionized water containing a wetting agent to obtain a filler suspension, (Cd-Fe)O x @The mass concentration of SiO2 is 40-50wt%, and the mass concentration of the wetting agent is 1-2wt.%.

[0028] A water-based two-component polyurethane coating comprises a component A and a component B; the mass ratio of the component A to the component B is (5.5-10):1.

[0029] The component A comprises the following components in parts by weight: 40-65 parts of water-based hydroxy acrylic resin, 0.5-3 parts of wetting and dispersing agent, 0.5-3 parts of defoaming agent, 5-10 parts of cosolvent, 10-25 parts of filler suspension, 0.5-3 parts of leveling agent, 0.5-5 parts of thixotropic thickener, and 15-25 parts of deionized water;

[0030] The B component includes the following components in parts by mass: 60-80 parts of a hydrophilic modified isocyanate curing agent and 10-15 parts of propylene glycol diacetate.

[0031] The wetting and dispersing agent is selected from at least one of TEGO 4100, TEGO 755W, and BYK-190; and the defoaming agent is selected from at least one of BYK022, BYK093, TEGO Airex 901W, and TEGO Foamex 810.

[0032] The cosolvent is selected from at least one of propylene glycol methyl ether, ethylene glycol butyl ether, and dipropylene glycol methyl ether.

[0033] The leveling agent is selected from at least one of TEGO-450, BYK-381, TEGO Glide 410, and TEGO Glide 4100; and the thixotropic thickener is selected from at least one of Borchi 0620 and RHEOLATE 299.

[0034] The present invention adopts the hydrothermal method to prepare magnetic nano-Fe3O4, which refers to using water and ethanol as hydrothermal reaction medium, in a closed inert atmosphere reactor, at a high temperature of 300-310 ° C, about equal to 20-40 MPa high pressure conditions for the reaction, the hydrothermal filling degree here is 40-80%, preferably 75%, at 310 ° C, the pressure inside the reactor is about 32 MPa, and during the reaction process, FeCl3 . 6H2O and CdCl2 . 6H2O is used as the metal source, and the composite complexing agent with tetrahydroxypropylethylenediamine and ethylenediaminetetraacetic acid (EDTA) as the two components can effectively complex iron and cadmium ions, shorten the distance between the two, and facilitate the formation of an alloy structure. Then 2,2'-bipyridine is added as a stabilizer to stabilize the metal ion state, and NaBH4 is used as a reducing agent to reduce part of Fe 3+ Fe 2+ , and Cd 2+ Cd is reduced, sodium acetate is used as an alkali source, and after dehydration, cadmium-doped Fe3O4 magnetic particles are generated. Under extremely high hydrothermal temperature and pressure conditions, the saturation magnetic intensity of the cadmium-doped Fe3O4 magnetic particles obtained is reduced, but compared with Fe3O4 or other FeO X Or CdO has extremely high corrosion resistance. Based on the above properties, Fe3O4, FeO X Or CdO is used for impurity removal, and the magnetic particles obtained after purification are high-purity cadmium-doped Fe3O4 magnetic particles. At the same time, in order to prepare a magnetic core-shell structure, it is necessary to introduce active groups on the surface of the above-mentioned cadmium-doped Fe3O4 magnetic nanoparticles. The active groups are mainly hydroxyl groups. Sulfuric acid will react with excess and easily corroded FeOx and CdO. The obtained purified high-purity cadmium-doped Fe3O4 magnetic particles undergo the following reaction in sulfuric acid and hydrogen peroxide: H2SO4+H2O2→H3O + +HSO4 - +O, to achieve hydroxylation on the surface of cadmium-doped Fe3O4 magnetic particles. During the purification and activation process, it should be noted that the acquisition time should not be longer than 4 minutes to avoid excessive corrosion.

[0035] Then, silicon oxide is directional adsorbed on the surface of Fe3O4 magnetic particles doped with cadmium hydroxylate. The directional adsorption mechanism is: alkaline conditions are selected, and ammonia water is used to provide hydroxide. TEOS is first hydrolyzed under alkaline conditions. The mechanism is OH -First, a nucleophilic reaction occurs with the silicon nucleus to generate silanol, and hydrogen bonds are formed between the hydroxyl groups of the silanol and the hydroxyl groups on the surface of the cadmium-doped Fe3O4 magnetic particles. Then, further condensation occurs on the basis of hydrogen bond bridging. At the same time, the silanol is dehydrogenated under alkaline conditions to form a Lewis base, which continues to react with other silicon nuclei and dehydrates (or dealcoholizes) to polymerize, slowly generating a network structure, and finally forming a SiO2 film on the surface of the cadmium-doped Fe3O4 magnetic particles.

[0036] See attached Figure 1 The energy spectrum diagram shows that the upper right 2, lower left, and lower right of the energy spectrum correspond to Si, Fe, and Cd respectively. It can be seen that the cadmium-doped Fe3O4 magnetic particles-SiO2 exist in a core-shell form, wherein the cadmium-doped Fe3O4 is the core with a size of 54nm and the silicon oxide is the shell with a size of 26nm. The magnetic nanoparticles are highly uniformly dispersed in the coating without obvious agglomeration. See the attached Figure 2 .

[0037] Beneficial technical effects

[0038] (1) The present invention first prepares relatively corrosion-resistant cadmium-doped Fe3O4 magnetic particles, and then effectively purifies the components of the magnetic particles through an acid washing and activation step, while simultaneously introducing hydroxyl groups on their surface.

[0039] (2) By introducing hydroxyl groups in a targeted manner, a slightly spiny silicon oxide coating is coated on the surface of the magnetic particle filler, which can significantly increase the (Cd-Fe)O x @SiO2 filler is soluble in water and is highly dispersed in the polyurethane coating. It has good coating compatibility and significantly improves the physical and chemical properties of polyurethane, such as tensile strength.

[0040] (3) By introducing hydroxyl groups in a targeted manner, a slightly spiny silicon oxide coating is coated on the surface of the magnetic particle filler, which improves the (Cd-Fe)O x The chemical stability of the coating is improved, especially the corrosion resistance of the coating is improved, and the service life of the magnetic coating is increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Attachment Figure 1 (Cd-Fe)O x @Energy spectrum of SiO2 filler.

[0042] Attachment Figure 2 (Cd-Fe)O x @Dispersion diagram of SiO2 filler in polyurethane. DETAILED DESCRIPTION Example 1

[0043] A method for preparing a two-component water-based paint filler comprises the following steps:

[0044] (1) Add 6.5mM FeCl3 . 6H2O, 0.75 mM CdCl2 . 6H2O metal salt was added to an ethanol-deionized water solution with a volume ratio of ethanol to deionized water of 1:8. After stirring evenly, 3.5 g / L tetrahydroxypropylethylenediamine and 1.5 g / L ethylenediaminetetraacetic acid complexing agent were added in sequence. 0.03 g / L 2,2'-bipyridine was then added as a stabilizer and 12.5 mL NaBH4 was added as a reducing agent. After stirring evenly, sodium acetate was used as an alkaline source and the pH was adjusted to 8 to obtain a precursor solution.

[0045] (2) Place the above precursor solution in an unlined stainless steel hydrothermal reactor, use nitrogen to expel the air in the reactor, then seal the reactor, heat it to 305°C at 7.5°C / min, keep it at that temperature for 36 hours, and cool it naturally to room temperature;

[0046] (3) Magnetic separation of hydrothermal products and activation and acid washing purification: the activation and acid washing purification is to place the magnetic separation hydrothermal products in a mixed solution of 98wt.% H2SO4 and 30wt.% H2O2 with a volume ratio of 1.5:1 for 2.5 minutes at a temperature of 30°C and stirring with a motor. After activation and acid washing purification, the magnetic particles are repeatedly washed with deionized water and ethanol in sequence until neutral. The saturation magnetic intensity of the magnetic particles after activation and acid washing purification is 62.7 emu / g, the remanence is 4.23emu / g, and the coercive force is Hc=41.8G. A 15wt.% magnetic particle suspension is prepared. The solvent of the suspension is composed of 4.5wt.% polyether modified silicone wetting agent, ethanol and deionized water, and the volume ratio of ethanol to deionized water is 1:8.

[0047] (4) Add 6.5 mL of ammonia water to the magnetic particle suspension prepared in step (3), stir for 15 min, add 3.5 g of ethyl silicate, stir for 13 h with a motor at 12 °C, then filter, wash, and vacuum dry the product to obtain (Cd-Fe)O x @SiO2 filler,(Cd-Fe)O x The saturation magnetic intensity of SiO2 filler is 25.3 emu / g.

[0048] The (Cd-Fe)O x @SiO2 filler is ultrasonically dispersed in deionized water containing a wetting agent, (Cd-Fe)O x @The mass concentration of SiO2 is 45wt%, the mass concentration of the wetting agent is 1.5wt.%, and the filler suspension obtained.

[0049] Comparative Example 1

[0050] A method for preparing a two-component water-based paint filler comprises the following steps:

[0051] (1) Add 6.5mM FeCl3 . 6H2O, 0.75 mM CdCl2 . 6H2O metal salt was added to an ethanol-deionized water solution with a volume ratio of ethanol to deionized water of 1:8. After stirring evenly, 5 g / L tetrahydroxypropylethylenediamine and 12.5 mL NaBH4 as a reducing agent were added in sequence and stirred evenly. Then, sodium acetate was used as an alkaline source and the pH was adjusted to 8 to obtain a precursor solution.

[0052] (2) The precursor solution was placed in an unlined stainless steel hydrothermal reactor, and the air in the reactor was exhausted with nitrogen. The reactor was then sealed and heated to 230°C at a rate of 7.5°C / min, kept at this temperature for 36 h, and then cooled naturally to room temperature.

[0053] (3) Magnetic separation of hydrothermal products and activation pickling purification: The activation pickling purification is to place the magnetic separation hydrothermal products in a mixed solution of 98wt.% H2SO4 and 30wt.% H2O2 with a volume ratio of 1.5:1 for 2.5 minutes at a temperature of 30°C and stirring with a motor. After activation pickling purification, the products are repeatedly washed with deionized water and ethanol in sequence until neutrality is achieved, and a 15wt.% magnetic particle suspension is prepared. The solvent of the suspension is composed of 4.5wt.% polyether-modified silicone wetting agent, ethanol and deionized water, and the volume ratio of ethanol to deionized water is 1:8.

[0054] (4) Add 6.5 mL of ammonia water to the magnetic particle suspension prepared in step (3), stir for 15 min, add 3.5 g of ethyl silicate, stir for 13 h with a motor at 12 °C, then filter, wash, and vacuum dry the product to obtain (Cd-Fe)O x @SiO2 filler.

[0055] The (Cd-Fe)O x @SiO2 filler is ultrasonically dispersed in deionized water containing a wetting agent, (Cd-Fe)O x @The mass concentration of SiO2 is 45wt%, and the mass concentration of wetting agent is 1.5wt.%.

[0056] Comparative Example 2

[0057] A method for preparing a two-component water-based paint filler comprises the following steps:

[0058] (1) Add 6.5mM FeCl3 .6H2O and metal salts were added to an ethanol-deionized water solution with a volume ratio of ethanol to deionized water of 1:8. After stirring evenly, 3.5 g / L tetrahydroxypropylethylenediamine and 1.5 g / L ethylenediaminetetraacetic acid composite complexing agent were added in sequence. Then, 0.03 g / L 2,2'-bipyridine was added as a stabilizer and 12.5 mL NaBH4 was added as a reducing agent. After stirring evenly, sodium acetate was used as an alkali source to adjust the pH to 8 to obtain a precursor solution.

[0059] (2) The precursor solution was placed in an unlined stainless steel hydrothermal reactor. The air in the reactor was expelled with nitrogen. The reactor was then sealed and heated to 305°C at a rate of 7.5°C / min. The temperature was kept at this temperature for 36 hours and then cooled naturally to room temperature.

[0060] (3) Magnetic separation of hydrothermal products and activation pickling purification: The activation pickling purification is to place the magnetic separation hydrothermal products in a mixed solution of 98wt.% H2SO4 and 30wt.% H2O2 with a volume ratio of 1.5:1 for 2.5 minutes at a temperature of 30°C and stirring with a motor. After activation pickling purification, the products are repeatedly washed with deionized water and ethanol in sequence until neutrality is achieved, and a 15wt.% magnetic particle suspension is prepared. The solvent of the suspension is composed of 4.5wt.% polyether-modified silicone wetting agent, ethanol and deionized water, and the volume ratio of ethanol to deionized water is 1:8.

[0061] (4) Add 6.5 mL of ammonia water to the magnetic particle suspension prepared in step (3), stir for 15 min, add 3.5 g of ethyl silicate, stir for 13 h with a motor at 12 °C, then filter, wash, and vacuum dry the product to obtain (Cd-Fe)O x @SiO2 filler.

[0062] The (Cd-Fe)O x @SiO2 filler is ultrasonically dispersed in deionized water containing a wetting agent, (Cd-Fe)O x @The mass concentration of SiO2 is 45wt%, and the mass concentration of wetting agent is 1.5wt.%.

[0063] Comparative Example 3

[0064] A method for preparing a two-component water-based paint filler comprises the following steps:

[0065] (1) Add 6.5mM FeCl3 . 6H2O, 0.75 mM CdCl2 .6H2O metal salt was added to an ethanol-deionized water solution with a volume ratio of ethanol to deionized water of 1:8. After stirring evenly, 3.5 g / L tetrahydroxypropylethylenediamine and 1.5 g / L ethylenediaminetetraacetic acid composite complexing agent were added in sequence. Then, 0.03 g / L 2,2'-bipyridine was added as a stabilizer and 12.5 mL NaBH4 was added as a reducing agent. After stirring evenly, sodium acetate was used as an alkali source to adjust the pH to 8 to obtain a precursor solution.

[0066] (2) The precursor solution was placed in an unlined stainless steel hydrothermal reactor. The air in the reactor was expelled with nitrogen. The reactor was then sealed and heated to 305°C at a rate of 7.5°C / min. The temperature was kept at this temperature for 36 hours and then cooled naturally to room temperature.

[0067] (3) Magnetic separation of hydrothermal products: preparing a 15 wt.% magnetic particle suspension, wherein the solvent of the suspension consists of 4.5 wt.% polyether-modified silicone wetting agent, ethanol, and deionized water, with the volume ratio of ethanol to deionized water being 1:8.

[0068] (4) Add 6.5 mL of ammonia water to the magnetic particle suspension prepared in step (3), stir for 15 min, add 3.5 g of ethyl silicate, stir for 13 h with a motor at 12 °C, then filter, wash, and vacuum dry the product to obtain (Cd-Fe)O x @SiO2 filler.

[0069] The (Cd-Fe)O x @SiO2 filler is ultrasonically dispersed in deionized water containing a wetting agent, (Cd-Fe)O x @The mass concentration of SiO2 is 45wt%, the mass concentration of the wetting agent is 1.5wt.%, and the filler suspension obtained.

[0070] There is no substantial difference between the preparation processes of Example 1 and Comparative Examples 1-3. The main difference is that there is no complexing agent and stabilizer in Comparative Document 1, no cadmium salt in Comparative Document 2, and no activation step in Comparative Document 3. After the hydrothermal products of step (3) of magnetic separation in Example 1 and Comparative Examples 1-3 are vacuum dried, a corrosion test is performed. Samples of equal mass are immersed in a 5wt.% saline solution for 15 minutes. The corrosion rates of Example 1 and Comparative Examples 1-3 are 93.5wt.%, 78.5wt.%, 80.2wt.%, and 93.4wt.%, respectively. The corrosion efficiency is further tested for 30 minutes. The corrosion rates of Example 1 and Comparative Examples 1-3 are 91.2wt.%, 65.5wt.%, 66.2wt.%, and 91.3wt.%, respectively. There is no essential difference in the corrosion rate of Example 1 at 15min and 30min, which clearly proves that the product is a corrosion-resistant magnetic particle. The corrosion resistance of the magnetic material comes from cadmium doping under high temperature and high pressure hydrothermal conditions. Under the same conditions, no complexing agent and stabilizer are added in Comparative Example 1, and the hydrothermal temperature is low, which has a higher corrosion efficiency. This is attributed to the fact that no alloy is formed, and the corrosive substances are iron oxides and cadmium oxides. The effect is similar to that of Comparative Example 2 in which no cadmium salt is added. In addition, Comparative Example 3 is no different from Example 1 in essence because the treatment steps before activation are similar. Example 2

[0071] The suspensions prepared in Example 1 and Comparative Example 3 were used as fillers for polyurethane.

[0072] A method for preparing a two-component water-based coating.

[0073] (A) Preparation of Component A: After uniformly mixing the water-based hydroxylated acrylic resin, wetting and dispersing agent, defoaming agent, leveling agent, and deionized water according to the formula, the filler suspension was added and stirred at 1000 rpm to uniformly mix. Then, the cosolvent and thixotropic thickener were added and mixed at a medium speed of 700 rpm to uniformly mix.

[0074] (B) Preparation method of component B: fully mix the hydrophilic modified isocyanate curing agent and propylene glycol diacetate to prepare the same.

[0075] (C) When using, mix component A and component B in a mass ratio of (7.5):1, and then spray it on the surface of the substrate. Example 3

[0076] A water-based two-component polyurethane coating comprises a component A and a component B; the mass ratio of the component A to the component B is 7.5:1.

[0077] The A component includes the following components by mass: 52 parts of water-based hydroxy acrylic resin, 1.5 parts of wetting and dispersing agent, 1.5 parts of defoaming agent, 7.5 parts of cosolvent, 20 parts of filler suspension, 1.5 parts of leveling agent, 2.5 parts of thixotropic thickener, and 20 parts of deionized water;

[0078] The B component includes the following components in parts by mass: 70 parts of a hydrophilic modified isocyanate curing agent and 12.5 parts of propylene glycol diacetate.

[0079] The wetting and dispersing agent is selected from BYK-190.

[0080] The defoaming agent is selected from BYK093.

[0081] The cosolvent is selected from ethylene glycol butyl ether.

[0082] The leveling agent is selected from TEGO Glide 4100.

[0083] The thixotropic thickener is selected from RHEOLATE 299.

[0084] The suspension prepared in Example 1 was used as the filler of polyurethane.

[0085] Comparative Example 4

[0086] A water-based two-component polyurethane coating comprises a component A and a component B; the mass ratio of the component A to the component B is 7.5:1.

[0087] The A component includes the following components by mass: 52 parts of water-based hydroxy acrylic resin, 1.5 parts of wetting and dispersing agent, 1.5 parts of defoaming agent, 7.5 parts of cosolvent, 20 parts of filler suspension, 1.5 parts of leveling agent, 2.5 parts of thixotropic thickener, and 20 parts of deionized water;

[0088] The B component includes the following components in parts by mass: 70 parts of a hydrophilic modified isocyanate curing agent and 12.5 parts of propylene glycol diacetate.

[0089] The wetting and dispersing agent is selected from BYK-190.

[0090] The defoaming agent is selected from BYK093.

[0091] The cosolvent is selected from ethylene glycol butyl ether.

[0092] The leveling agent is selected from TEGO Glide 4100.

[0093] The thixotropic thickener is selected from RHEOLATE 299.

[0094] The suspension prepared in Comparative Example 3 was used as the filler of polyurethane.

[0095] Comparative Example 5

[0096] A water-based two-component polyurethane coating comprises a component A and a component B; the mass ratio of the component A to the component B is (7.5):1.

[0097] The A component includes the following components by mass: 52 parts of water-based hydroxy acrylic resin, 1.5 parts of wetting and dispersing agent, 1.5 parts of defoaming agent, 7.5 parts of cosolvent, 20 parts of filler suspension, 1.5 parts of leveling agent, 2.5 parts of thixotropic thickener, and 20 parts of deionized water;

[0098] The B component includes the following components in parts by mass: 70 parts of a hydrophilic modified isocyanate curing agent and 12.5 parts of propylene glycol diacetate.

[0099] The wetting and dispersing agent is selected from BYK-190.

[0100] The defoaming agent is selected from BYK093.

[0101] The cosolvent is selected from ethylene glycol butyl ether.

[0102] The leveling agent is selected from TEGO Glide 4100.

[0103] The thixotropic thickener is selected from RHEOLATE 299.

[0104] The filler suspension preparation process is as follows: It includes the following steps:

[0105] (1) Add 6.5mM FeCl3 . 6H2O, 0.75 mM CdCl2 . 6H2O metal salt was added to an ethanol-deionized water solution with a volume ratio of ethanol to deionized water of 1:8. After stirring evenly, 3.5 g / L tetrahydroxypropylethylenediamine and 1.5 g / L ethylenediaminetetraacetic acid complexing agent were added in sequence. 0.03 g / L 2,2'-bipyridine was then added as a stabilizer and 12.5 mL NaBH4 was added as a reducing agent. After stirring evenly, sodium acetate was used as an alkaline source and the pH was adjusted to 8 to obtain a precursor solution.

[0106] (2) Place the above precursor solution in an unlined stainless steel hydrothermal reactor, use nitrogen to expel the air in the reactor, then seal the reactor, heat it to 305°C at 7.5°C / min, keep it at that temperature for 36 hours, and cool it naturally to room temperature;

[0107] (3) Magnetic separation of hydrothermal products and activation and acid washing purification: The activation and acid washing purification is to place the magnetic separation hydrothermal products in a mixed solution of 98wt.% H2SO4 and 30wt.% H2O2 with a volume ratio of 1.5:1 for 2.5 minutes at a temperature of 30°C and stirring with a motor. After activation and acid washing purification, the products are repeatedly washed with deionized water and ethanol in sequence until they are neutral.

[0108] The (Cd-Fe)O x The filler was ultrasonically dispersed in deionized water containing a wetting agent, wherein the mass concentration of (Cd-Fe)O was 45 wt % and the mass concentration of the wetting agent was 1.5 wt %, to obtain a filler suspension.

[0109]

[0110] As shown in the table above, the main difference between Example 3 and Comparative Example 4 is whether the fillers are different, and the further difference is whether the fillers have been purified and activated. The difference between Example 3 and Comparative Example 5 is whether the coating treatment is performed. The coating is applied to the surface of the metal substrate, and then the polarization potential is tested, and the corrosion current density is converted. The corrosion current density of Example 3 is significantly higher than that of Comparative Example 4 and Comparative Example 5. The difference between Comparative Example 5 mainly lies in whether it has been purified and activated. Without purification and activation, the hydrothermal product composition is more complex, and more importantly, there is no functional group on the surface, which affects the subsequent directional coating of silicon oxide. In addition, as shown in Comparative Example 5, without silicon oxide coating, the single (Cd-Fe)O x The filler has poor corrosion resistance and (Cd-Fe)O x Poor dispersion in the coating and filler agglomeration will affect the corrosion resistance of the coating. The most direct manifestation of agglomeration is the reduction of tensile strength, as shown above.

[0111] The embodiments described above provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications and improvements made within the scope of the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A water-based two-component polyurethane coating, characterized in that: The invention comprises a component A and a component B; the mass ratio of the component A to the component B is (5.5-10):1; The component A comprises the following components in parts by weight: 40-65 parts of water-based hydroxy acrylic resin, 0.5-3 parts of wetting and dispersing agent, 0.5-3 parts of defoaming agent, 5-10 parts of cosolvent, 10-25 parts of filler suspension, 0.5-3 parts of leveling agent, 0.5-5 parts of thixotropic thickener, and 15-25 parts of deionized water; The B component includes the following components in parts by mass: 60-80 parts of a hydrophilic modified isocyanate curing agent and 10-15 parts of propylene glycol diacetate; The filler suspension is prepared by the following steps: (1) Add 5-8mM FeCl3 . 6H2O, 0.5-1 mM CdCl2 . 6H2O metal salt is added to an ethanol-deionized water solution, stirred evenly, and then 3-4 g / L tetrahydroxypropylethylenediamine and 1-2 g / L ethylenediaminetetraacetic acid composite complexing agent are added in sequence. Then, 0.02-0.04 g / L 2,2'-bipyridine is added as a stabilizer and 10-15 mL NaBH4 is added as a reducing agent. After stirring evenly, sodium acetate is used as an alkaline source and the pH is adjusted to 7.5-8.5 to obtain a precursor solution. (2) Place the above-mentioned precursor solution in an unlined stainless steel hydrothermal reactor, use nitrogen to expel the air in the reactor, then seal the reactor, heat it to 300-310°C at 5-10°C / min, keep it at this temperature for 24-48 hours, and cool it naturally to room temperature; (3) Magnetic separation of hydrothermal products and activation and acid washing purification: the activation and acid washing purification is to place the magnetic separation hydrothermal products in a mixed solution consisting of 98wt.% H2SO4 and 30wt.% H2O2 with a volume ratio of 1-2:1 for 2-3 minutes at a temperature of 30°C and stirring with a motor. After activation and acid washing purification, deionized water and ethanol are used to repeatedly wash the products until they are neutral, and a 10-20wt.% magnetic particle suspension is prepared. The solvent of the suspension consists of a polyether-modified silicone wetting agent, ethanol and deionized water. (4) Add ammonia water to the magnetic particle suspension prepared in step (3), stir for 10-20 minutes, add ethyl silicate, stir with a motor for 12-14 hours at a temperature of 10-14°C, then filter, wash, and vacuum dry the product to obtain (Cd-Fe)O x @SiO2 filler, the (Cd-Fe)O x @SiO2 filler is ultrasonically dispersed in deionized water containing a wetting agent to obtain a filler suspension, (Cd-Fe)O x @SiO2 mass concentration is 40-50wt%, (Cd-Fe)O x The core size is 20-70 nm, the thickness of the SiO2 shell is 10-30 nm, and the mass concentration of the wetting agent is 1-2 wt.%.

2. A water-based two-component polyurethane coating according to claim 1, characterized in that The wetting and dispersing agent is selected from at least one of TEGO 4100, TEGO 755W, and BYK-190; the defoaming agent is selected from at least one of BYK022, BYK093, TEGO Airex901W, and TEGO Foamex 810; The cosolvent is selected from at least one of propylene glycol methyl ether, ethylene glycol butyl ether, and dipropylene glycol methyl ether.

3. A water-based two-component polyurethane coating according to claim 1, characterized in that The leveling agent is selected from at least one of TEGO-450, BYK-381, and TEGO Glide 410; and the thixotropic thickener is selected from at least one of Borchi 0620 and RHEOLATE299.

4. A water-based two-component polyurethane coating according to claim 1, characterized in that The content of the polyether modified silicone wetting agent is 4-5 wt.%.

5. A water-based two-component polyurethane coating according to claim 1, characterized in that The volume ratio of ethanol to deionized water in the solvent of the ethanol-deionized water solution in step (1) and the suspension in step (3) is 1:7-9.

6. A water-based two-component polyurethane coating according to claim 1, characterized in that The amount of the ethyl silicate used is 3-4 g, and the amount of the ammonia water used is 5-8 mL.

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