Preparation method and equipment of metal texture colored powder coating

Abstract

The invention relates to the technical field of powder coatings, and provides a preparation method and equipment of a metal-texture colored powder coating, and the method comprises the following steps: carrying out dispersion treatment on flaky aluminum powder through an alcohol solvent, and then adding a silicon source for hydrolysis reaction, so that the surface of the flaky aluminum powder is coated with a silicon dioxide layer; dispersing the flaky aluminum powder coated with the silicon dioxide layer into water, and adding composite metal salt for co-deposition treatment, so that the surface of the flaky aluminum powder is coated with a composite metal oxide layer; and dispersing the flaky aluminum powder coated with the silicon dioxide layer and the composite metal oxide layer into an organic solvent for polymerization reaction, so that the surface of the composite metal oxide layer is coated to form a polymer resin layer, and the modified aluminum pigment is obtained. The composite metal salt is added for co-deposition treatment, so that the surface of the flaky aluminum powder is coated with the composite metal oxide layer, and the color transition effect can be realized and the color richness can be improved by adjusting the proportional gradient change of various metal salts in the composite metal salt.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of powder coating, in particular to a preparation method and equipment of metal texture color powder coating. BACKGROUND

[0002] The powder coating is a solid powder synthetic resin coating composed of solid resin and pigment, filler and additive. In some prior art color powder coating, flaky aluminum powder is dissolved in a solvent and hydrolyzed in a silicon source to form a silicon dioxide layer, then the flaky aluminum powder with the silicon dioxide coating layer is dispersed in water, a metal salt is added to perform a deposition reaction, and a metal oxide layer coating is formed on the surface of the silicon dioxide layer.

[0003] Although such color powder coating has certain metal texture and color, the metal oxide layer is often coated with only a single metal salt, which limits the color richness and makes it difficult to achieve color transition effect. SUMMARY

[0004] Therefore, in order to improve the color richness of the color powder coating, the present application provides a preparation method and equipment of metal texture color powder coating, and the specific technical solutions are as follows: A preparation method of metal texture color powder coating, comprising the following steps: S1, dispersing the flaky aluminum powder by alcohol solvent, and adding a silicon source to perform a hydrolysis reaction to coat the surface of the flaky aluminum powder with a silicon dioxide layer; S2, dispersing the flaky aluminum powder coated with the silicon dioxide layer in water, and adding a composite metal salt to perform a co-deposition treatment to coat the surface of the flaky aluminum powder with a composite metal oxide layer; S3, dispersing the flaky aluminum powder coated with the silicon dioxide layer and the composite metal oxide layer in an organic solvent, and adding an acrylic monomer, a styrene monomer and an initiator to perform a polymerization reaction to coat the surface of the composite metal oxide layer with a polymer resin layer, thereby obtaining modified aluminum pigment.

[0005] The preparation method of the metal texture color powder coating coats the surface of the flaky aluminum powder with a composite metal oxide layer by adding a composite metal salt to perform a co-deposition treatment, and can realize color transition effect and improve color richness by adjusting the proportion gradient of various metal salts in the composite metal salt.

[0006] Preferably, the preparation method further comprises: S4, mixing the obtained modified aluminum pigment with a powder base material to obtain a mixture; S5, extruding the mixture by a double screw extruder to obtain a coating in a molten state; S6, cooling the coating in a molten state and crushing the cooled coating to obtain a powder coating with a certain particle size.

[0007] Preferably, the specific method of adding a composite metal salt for co-deposition treatment comprises: obtaining the number of metal salt types of the composite metal salt to be added; obtaining the initial concentration and deposition rate coefficient of each metal ion; constructing a color gradient model according to the number of metal salt types, the initial concentration and the deposition rate coefficient; obtaining the instantaneous concentration value of each metal ion according to the color gradient model.

[0008] Preferably, the preparation method further comprises: based on the color gradient model, realizing color gradient by adjusting the flow rate of the metal salt solution.

[0009] Preferably, the composite metal salt is composed of ferric chloride and tin tetrachloride, and the mass ratio of ferric chloride to tin tetrachloride is 3:1, the pH value of the deposition treatment is 4, the temperature is 85 , and the time is 20 min.

[0010] Preferably, the composite metal salt is composed of cobalt dichloride and chromium trichloride, and the mass ratio of cobalt dichloride to chromium trichloride is 2:1, the pH value of the deposition treatment is 4.5, the temperature is 82 , and the time is 25 min.

[0011] Preferably, the powder substrate comprises epoxy-polyester resin and leveling agent.

[0012] A preparation device for metal texture color powder coating is used to realize the preparation method, which comprises: A flaky aluminum powder pretreatment device is used to disperse the flaky aluminum powder by an alcohol solvent, add a silicon source to perform a hydrolysis reaction, so that the flaky aluminum powder is coated with a silicon dioxide layer on the surface; A metal oxide deposition device is used to disperse the flaky aluminum powder coated with the silicon dioxide layer into water, add a composite metal salt to perform co-deposition treatment, so that the flaky aluminum powder is coated with a composite metal oxide layer on the surface; A resin polymerization treatment device is used to disperse the flaky aluminum powder coated with the silicon dioxide layer and the composite metal oxide layer into an organic solvent, and add acrylic monomer, styrene monomer and initiator to perform polymerization reaction, so that the composite metal oxide layer is coated with a polymer resin layer on the surface to obtain a modified aluminum pigment.

[0013] Preferably, the preparation device further comprises: The mixing device is used for mixing the obtained modified aluminum pigment with the powder base material to obtain a mixture. The double screw extruder is used for extruding the mixture to obtain a coating in a molten state. The cooling device is used for cooling the coating in the molten state. The crushing device is used for crushing the coating after the cooling to obtain a powder coating with a certain particle size. BRIEF DESCRIPTION OF DRAWINGS

[0014] The present application can be further understood from the following description in conjunction with the drawings. The components in the drawings are not necessarily drawn to scale, but emphasis is instead placed upon illustrating the principles of the embodiments. In different views, the same reference numerals designate corresponding parts.

[0015] Figure 1 is a schematic diagram of the overall process of a preparation method of a metal texture color powder coating according to an embodiment of the present application; Figure 2 is a schematic diagram of a specific method of adding a composite metal salt for co-deposition treatment according to an embodiment of the present application; Figure 3 is a schematic diagram of the overall process of a preparation method of a metal texture color powder coating according to another embodiment of the present application; Figure 4 is a schematic diagram of the overall structure framework of a preparation device of a metal texture color powder coating according to an embodiment of the present application. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and do not limit the protection scope of the present application.

[0017] It should be noted that when an element is referred to as being "fixed" to another element, it can be directly on the other element or there can be an intervening element. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or there can be an intervening element. The terms "vertical", "horizontal", "left", "right", and similar expressions used herein are only for the purpose of illustration and are not the only embodiments.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0019] The "first", "second" in the present application do not represent the specific number and order, but only for the name of the distinction.

[0020] Before the detailed description of the embodiments of the present application, a brief introduction of the prior art is given.

[0021] Powder coating is a solid powder synthetic resin coating composed of solid resin and pigments, fillers and additives, etc. Unlike ordinary solvent-based coatings and water-based coatings, its dispersion medium is not solvent and water, but air. It has the characteristics of no solvent pollution, 100% film forming and low energy consumption. Powder coating has thermoplastic and thermosetting two categories. The appearance of thermoplastic powder coating (gloss and leveling) is poor, and the adhesion between the metal is also poor, so it is rarely used in the field of automobile coating. Automobile coating generally uses thermosetting powder coating. Thermosetting powder coating is a thermosetting synthetic resin as a film-forming material. In the drying process, the resin is first melted, and then cured into a smooth and hard coating after chemical crosslinking.

[0022] In terms of decoration, in addition to ordinary types of different gloss, smooth surface powder coating varieties, orange peel, wrinkle, sand, pattern, hammer, metal powder coating varieties and usage are also increasing, gradually penetrating into the fields of solvent-based coating applications. Among these varieties, metal powder coating is a major decorative powder coating variety, which includes metal flash, metal plating, metal pattern, hammer and metal gloss texture type powder coating. With the large use of metal powder coating, the quality requirements are becoming higher and higher.

[0023] Currently, in the preparation of metal powder coating, the following steps are mainly included, raw material weighing → premixing → melting and extrusion → tabletting → coarse crushing → fine crushing → grading → packaging. The premixing process is to mix the powder base material, filler and pigment by stirring. The melting and extrusion process is to melt and extrude the mixed raw materials.

[0024] For some color powder coatings with metallic texture, the flaky aluminum powder is usually first dispersed and treated, and a silicon source is added for hydrolysis reaction to coat a silica layer on the surface of the flaky aluminum powder. Then the aluminum powder is dispersed in water, and according to the color required to be presented, the corresponding monolayer metal salt such as ferric chloride, cobalt chloride and tin chloride is added to coat a metal oxide layer on the surface of the flaky aluminum powder.

[0025] This type of colored powder coating has significant limitations; its metallic hue is rather monotonous and it lacks color transition effects, leaving room for improvement and optimization.

[0026] To achieve color transition effects in colored powder coatings and enhance their color richness, such as Figure 1 As shown, a method for preparing a metallic-textured colored powder coating according to an embodiment of the present invention includes the following steps: S1, after dispersing the flake aluminum powder with an alcohol solvent, a silicon source is added to carry out a hydrolysis reaction so that the surface of the flake aluminum powder is coated with a silicon dioxide layer.

[0027] Specifically, the aspect ratio of the flake aluminum powder is between 40 and 200, and the particle size is between 10 μm and 50 μm. The silicon source is tetraethyl orthosilicate and 3-aminopropylmethyltriethoxysilane in a mass ratio of 4:1. The catalyst for the hydrolysis reaction is ammonia or ethylenediamine, the temperature is 40℃-60℃, and the time is 4h-8h.

[0028] Ethanol is used as the solvent, and the amount of silicon source added can be 0.3 times the mass of aluminum powder. Aluminum powder is dispersed in ethanol (20% solids content), and a mixture of silicon source and ammonia is added dropwise at 40°C. Hydrolysis is then carried out at 55°C for 6 hours at 500 rpm. The resulting silica layer increases chemical stability and enhances the bonding force with subsequent metal oxides.

[0029] S2, disperse the flake aluminum powder coated with a silicon dioxide layer after step S2 into water, add a composite metal salt for co-deposition treatment, so that the surface of the flake aluminum powder is coated with a composite metal oxide layer.

[0030] The pH environment and time for co-deposition treatment can be set according to the composite metal oxide layer. For example, to achieve a red-gold gradient transition effect, the mass ratio of composite metal salts can be set to Fe2O3:SnCl4=3:1, and the deposition conditions are: pH=4, 85℃×20min; to achieve a blue-purple gradient, the mass ratio of composite metal salts can be set to CoCl2:CrCl3=2:1, and the deposition conditions are: pH=4.5, 82℃×25min.

[0031] As a preferred technical solution, such as Figure 2 As shown, the specific method for co-deposition treatment with composite metal salts in step S2 includes: S21, obtain the number of metal salt types to be added to the composite metal salt.

[0032] S22, obtain the initial concentration and deposition rate coefficient of each metal ion.

[0033] S23, constructing a color gradient model according to the number of metal salt types, initial concentrations and deposition rate coefficients.

[0034] S24, obtaining the instantaneous concentration value of each metal ion according to the color gradient model.

[0035] After obtaining the instantaneous concentration value of each metal ion, the preparation method further comprises: realizing the color gradient transition by adjusting the flow rate of the metal salt solution based on the color gradient model.

[0036] Exemplarily, the color gradient model is expressed as . Wherein, represents the deposition rate coefficient of the th metal salt, represents the metal salt ion concentration of the th at time t, represents the initial concentration of the th metal salt ion, and exp() represents the natural exponential function.

[0037] Specifically, the initial concentration is used to control the starting color development intensity, and the primary color phase is controlled by adjusting the initial concentration ratio of different metal salts. The deposition rate coefficient determines the color transition speed, which can be used to control the color transition rate and the sharpness of the gradient effect. For example, a high deposition rate coefficient can realize fast color development and present a sharp boundary effect, while a low deposition rate coefficient can realize slow color development and present a soft gradient effect. Generally, the deposition rate coefficient is a constant value set according to experience. For example, for red gold gradient color, the deposition rate coefficient corresponding to the metal salt FeCl3 can be set to 0.5 / min, and the deposition rate coefficient corresponding to the metal salt SnCl4 can be set to 0.2 / min.

[0038] The time variable t corresponds to the precipitation time in the process. In actual application, two independently controlled metal salt storage tanks (such as Fe 3+ tank and Sn 4+The color gradient model is used to obtain the different metal salt ion concentrations at time t, and then a peristaltic pump is used to adjust the flow rate of the corresponding metal salt solution by cooperating with a proportional regulating valve to mix and spray the flaky aluminum powder suspension in a stirring container, such as a stirred tank. The metal salt ion concentration and the corresponding metal salt solution flow rate can be determined based on experimental calibration, specifically including: under the condition of determining the reaction kettle volume, a plurality of metal salt ion concentrations and corresponding metal salt solution flow rates are obtained by experimental measurement, a metal salt ion concentration-solution flow rate function curve is determined based on the plurality of metal salt ion concentrations and corresponding metal salt solution flow rates, and a plurality of corresponding metal salt solution flow rates of different metal salt ion concentrations are obtained according to the determined metal salt ion concentration-solution flow rate function curve; or a plurality of metal salt solution flow rates corresponding to a plurality of metal salt ion concentrations are determined by mapping based on actual experience, and then a metal salt ion concentration-solution flow rate function curve is determined based on the plurality of metal salt ion concentrations and corresponding metal salt solution flow rates.

[0039] For example, when F 3+ The corresponding deposition rate coefficient is set to 0.3 / min, and Sn 4+ The corresponding deposition rate coefficient is set to 0.1 / min, and since the color gradient model is an exponential decay model, at the beginning of the reaction, F 3+ Fast deposition, dominated by the red layer, Sn 4+ Slow deposition, with the gold layer slowly superimposed, the iron red dominates in the early stage, and the tin yellow gradually appears in the later stage, which can form a sunset-like gradient effect.

[0040] For traditional color powder coatings, which are coated with a single metal salt oxide layer on aluminum powder, only a single gold color can be achieved. However, through the color gradient model, the present embodiment can adjust multiple metal gradient colors such as red gold / blue purple, and the color development can be dynamically controlled by the deposition rate coefficient, achieving precise gradient and effectively reducing the hue control error.

[0041] S3, disperse the flaky aluminum powder coated with a silica layer and a composite metal oxide layer treated in step S2 into an organic solvent, and add acrylic monomers, styrene monomers and initiators for polymerization reaction to form a polymer resin layer on the surface of the composite metal oxide layer, thereby obtaining a modified aluminum pigment.

[0042] The acrylic monomer is methyl methacrylate (MMA) and hydroxyethyl methacrylate (HEMA) with a mass ratio of 7:3. The initiator is azobisisobutyronitrile (AIBN) with a dosage of 1.2wt%-2.0wt%. The double-coated (silica layer and composite metal oxide layer) aluminum powder is dispersed in toluene, and allyl chloroformate is added for pre-reaction for 30 min to enhance monomer grafting, and the monomer and AIBN mixture is added dropwise at 85℃ for 3h of polymerization. The polymer resin protective layer improves processability. Here, the introduction of HEMA provides hydroxyl groups, which can enhance the compatibility with the powder coating resin.

[0043] The preparation method of the metal texture color powder coating is to add composite metal salts for co-deposition treatment to coat the surface of the flaky aluminum powder with a composite metal oxide layer. By adjusting the proportion gradient of various types of metal salts in the composite metal salt, the color transition effect can be achieved to improve the color richness.

[0044] In one embodiment, as shown in Figure 3 The preparation method further includes the following steps: S4, the obtained modified aluminum pigment is mixed with a powder base material to obtain a mixture.

[0045] S5, the mixture is extruded by a double-screw extruder to obtain a coating in a molten state.

[0046] S6, the coating in the molten state is cooled and the cooled coating is crushed to obtain a powder coating with a certain particle size.

[0047] The powder base material includes an epoxy-polyester resin and a leveling agent. In the mixture, the content of the modified aluminum pigment is 30wt%, the content of the epoxy-polyester resin is 65wt%, and the content of the leveling agent is 5wt%. When the mixture is extruded by the double-screw extruder, the temperature is set to be between 110℃ and 120℃. The particle size of the finally obtained powder coating can be set to be 35μm.

[0048] Before step S4, when the polymerization reaction is performed, the content of the acrylic monomer, the styrene monomer and the initiator can be set to be 60wt%, 30wt% and 1.5wt% respectively. A gradient curing program is adopted, in the pre-polymerization stage, the temperature is set to be between 80℃ and 85℃, and the time can be set to be 2h; in the final curing stage, the temperature is set to be 130℃, and the time is set to be 15min. In this way, by using the low-temperature-high-temperature gradient composite curing program, the epoxy-modified acrylic monomer is introduced into the resin layer, so that the pre-polymer is formed at 80℃-85℃, which is beneficial to the subsequent spraying and curing at a temperature of 200℃.

[0049] The color gradient transition model Although it can be used as a basis for adjusting the flow rate of the metal salt solution to achieve color gradient, and the model is relatively simple, it is only related to the deposition rate coefficient, reaction time and initial concentration, and the deposition rate coefficient is often an empirical constant, which ignores the reaction temperature, pH value and solvent compatibility, and cannot respond to process fluctuations, and needs to be improved. In order to solve the above technical problems, in one embodiment, the preparation method further comprises the following steps: During the process of co-deposition of composite metal salt, ultrasonic treatment is assisted to promote ion diffusion by ultrasonic cavitation effect to reduce boundary layer thickness, ultrasonic field effect term is obtained based on ultrasonic angular frequency, pH response term is obtained and acquired according to the acidity and alkalinity of the reaction system, and temperature activation term is obtained according to ion solvation energy and reaction temperature, and finally dynamic deposition rate coefficient is obtained based on ultrasonic field effect term, pH response term and temperature activation term, and the original color gradient model is corrected according to the dynamic deposition rate coefficient The corrected color gradient model is represented as .

[0050] The deposition rate coefficient is . The ultrasonic energy coupling coefficient is The ultrasonic angular frequency is generally set between 20-40 kHz. The pH response coefficient is pH, which is the acidity and alkalinity of the reaction system, The temperature effect pre-factor is The metal ion solvation energy is The Boltzmann constant is T, which is the real-time temperature, generally expressed in absolute temperature. The ultrasonic field effect term, the pH response term and the temperature activation term are represented by

[0051] For the ultrasonic field effect term, it promotes ion diffusion through ultrasonic cavitation effect, accelerates ion migration to the surface of aluminum powder, and can reduce the thickness of boundary layer. For the temperature activation term, the ion solvation energy determines the ion activity, and the solvation energy is the energy barrier of ion out of the solvent cage, and the temperature T can provide activation energy, and the reaction rate is proportional to When the temperature rises unexpectedly, the temperature activation term is automatically activated, and the ultrasonic power is increased to dynamically compensate for process disturbances.

[0052] Generally speaking, an acidic environment can promote the hydrolysis of metal salts. The lower the pH, the faster the deposition rate. When the pH value is reduced to 2-3, stable deposition can be achieved by increasing the β value. When the pH value is increased to 6-7, the β value can be appropriately reduced to compensate for the hydrolysis rate. In addition, through the regulation of ion solvation energy, the water-based / non-aqueous system can be compatible. For the water-based system, the ion solvation energy is high, and the temperature needs to be increased for appropriate compensation. For the alcohol system, the ion solvation energy is low, and at this time, it can be operated at room temperature to achieve the purpose of energy conservation.

[0053] The optimized color gradient model allows for a wider pH / temperature fluctuation range, improves process robustness, and is applicable to water-based / solvent-based systems by introducing a multi-physical field coupling mechanism including ultrasonic fields, acid-base chemistry, and thermodynamics, thus expanding solvent compatibility. Overall, it can significantly improve the accuracy and adaptability of the deposition process.

[0054] Sometimes, as the deposition progresses, the coating layer on the surface of aluminum powder thickens. The deposition rate can be maintained by adjusting the ultrasonic energy, that is, different ultrasonic angular frequencies are used at different stages of deposition. For example, assuming the total deposition time is t2, in stage 1 (0 < t ≤ t1), high ultrasonic energy can be used for rapid deposition; in stage 2 (t1 < t ≤ t2), the ultrasonic energy can be appropriately reduced to avoid overreaction; in stage 3 (t > t2), low energy is maintained to complete the deposition.

[0055] In some actual situations and application scenarios, there are certain ion interferences when co-depositing composite metal salts. For example, when designing a blue-violet gradient layer, there is a problem of competitive deposition between Co 2+ and Cr 3+ . Another example is that when depositing a metal oxide layer with chloride metal salts under the condition of pH 3-5, the hydrolysis rates of different ions vary greatly. In addition, when designing a red-gold gradient, Sn 4+ has a certain inhibitory effect on Fe 3+ . When designing a blue-violet gradient, there is an electron transfer synergistic effect between Cr 3+ and Co 2+ . During the co-deposition process of composite metal salts, if the interference between metal ions is not considered, the calculated instantaneous concentration of metal ions at a certain moment t is prone to error, which may lead to problems such as color deviation from the design, out-of-control proportion of metal oxides, and uneven gradient effect.

[0056] To solve the above problems, an ion interference compensation mechanism is introduced to correct the metal salt concentration at a certain moment t in the color gradient model. The corrected color gradient model is expressed as . Among them, represents the concentration of the interference ion in the co-deposition system, that is, the real-time concentration of other metal ions j present simultaneously. For the cross-coupling coefficient, it can be understood as the interference intensity of ion j on the deposition rate of ion i.

[0057] When , ion j inhibits the deposition of ion i, for example: Sn 4+ competes with Fe 3+ for hydrolysis sites, which reduces the generation rate of Fe2O3; when , ion j promotes the deposition of ion i, for example: Cr 3+ induces Co 2+ oxidation to Co 3+ , accelerating the generation of Co3O4; when , ion j has no interference on ion i.

[0058] For the cross-coupling coefficient, it can be calibrated by experiment, specifically, under the condition of fixing parameters such as pH value and reaction temperature, first, the first deposition amount of ion i alone is obtained by experiment, then the second deposition amount when ion i and j coexist is obtained by experiment, and the cross-coupling coefficient is calculated according to the second deposition amount, the first deposition amount and the initial concentration of the interfering ion j. Exemplarily, the cross-coupling coefficient = (second deposition amount-first deposition amount) / initial concentration of interfering ion j. Exemplarily, some typical reaction system measured data is given here, such as ion combination (i-j) Fe 3+ -Sn 4+ , the cross-coupling coefficient is +2.3×10 -3 L / mol·s, such as ion combination (i-j) Co 2+ -Cr 3+ , the cross-coupling coefficient is -1.7×10 -3 L / mol·s. Wherein, the test conditions specifically include: pH=4.0, reaction temperature is 85 degrees Celsius, the concentration of interfering ion is 0.1 mol / L, and the concentration of main ion is 0.1 mol / L.

[0059] In summary, the corrected color gradient transition model solves the color deviation problem caused by ion competition during the deposition of composite metal salt, which is beneficial to improve the quantitative control accuracy and obtain uniform color gradient effect.

[0060] An embodiment of the present application also provides a preparation equipment of metal texture color powder coating for realizing the preparation method, as shown in Figure 4 , which comprises a sheet-shaped aluminum powder pretreatment device, a metal oxide deposition device and a resin polymerization treatment device.

[0061] The flaky aluminum powder pretreatment device is used for dispersing and treating the flaky aluminum powder by an alcohol solvent, adding a silicon source to perform a hydrolysis reaction, so as to coat a silicon dioxide layer on the surface of the flaky aluminum powder; the metal oxide deposition device is used for dispersing the flaky aluminum powder coated with the silicon dioxide layer into water, adding a composite metal salt to perform a co-deposition treatment, so as to coat a composite metal oxide layer on the surface of the flaky aluminum powder; and the resin polymerization treatment device is used for dispersing the flaky aluminum powder coated with the silicon dioxide layer and the composite metal oxide layer into an organic solvent, and adding an acrylic monomer, a styrene monomer and an initiator to perform a polymerization reaction, so as to coat a polymer resin layer on the surface of the composite metal oxide layer, thereby obtaining a modified aluminum pigment.

[0062] Specifically, the flaky aluminum powder pretreatment device includes but is not limited to a stirring container, the flaky aluminum powder to be treated is first put into the stirring container, then a certain amount of alcohol solvent is added and stirred uniformly for a certain time, the solvent oil and additives on the surface of the aluminum pigment are cleaned by the alcohol solvent such as ethanol, and after solid-liquid separation, the pretreated flaky aluminum powder is obtained; then, the flaky aluminum powder suspension is prepared by using the pretreated flaky aluminum powder, and the silicon source is added to perform a stirring reaction, after aging, washing and filtering, a silicon dioxide coating layer is formed on the surface of the flaky aluminum powder, thereby obtaining the flaky aluminum powder with the silicon dioxide coating layer.

[0063] The metal oxide deposition device includes but is not limited to a reaction kettle, the flaky aluminum powder with the silicon dioxide coating layer and the composite metal salt are added into the reaction kettle to perform a co-deposition treatment, so as to coat a composite metal oxide layer on the surface of the flaky aluminum powder. The resin polymerization treatment device includes but is not limited to a stirring container. Since the specific structure of the stirring container or the stirring and heating container belongs to the conventional technical means in the art, it is not described herein.

[0064] In the pretreatment process, the ultrasonic field can be used to disperse the aluminum powder agglomerates, and the frequency is set to 20 kHz.

[0065] As a preferred technical solution, based on the theory of turbulent pulsation, the relationship model of the standard deviation σ of the coating layer thickness and the stirring speed N of the reactor . Wherein, K represents a device constant, a constant determined by the inherent characteristics of the reaction system, including the reactor geometry, the type of stirring paddle, the material properties, etc., such as a kettle reactor which can be generally set to 1.2. represents the average coating layer thickness. represents the fluid dynamic viscosity, which can be understood as the viscosity of the reaction liquid, reflecting the ability of the fluid to resist shear deformation, the higher the viscosity, the weaker the mixing effect of the turbulent pulsation on the particles.

[0066] Specifically, small-scale vortices increase at high rotation speed, promoting micro-mixing and reducing the difference in particle concentration distribution. The smaller the minimum vortex scale, the more complete the mixing. The turbulence has an impact on the coating layer, and the vortex motion can make the concentration distribution of metal ions on the surface of aluminum powder uniform, and the deposition rate consistent, thereby reducing the thickness fluctuation. The relationship model establishes a quantitative relationship between the stirring speed N and the fluid dynamic viscosity and the uniformity of the coating layer , which can be used to predict and optimize the uniformity of the coating process. respectively represent the turbulence intensity and the viscosity damping. The turbulence intensity generally increases super-linearly with the rotation speed, and the viscosity reduction can enhance the dispersion of turbulence on the particles, which reflects the competitive effect of turbulence intensity and viscosity damping.

[0067] By calibrating the equipment constant and the fluid dynamic viscosity, if the thickness fluctuation is required to be less than 10%, that is, the uniformity of the coating layer , the minimum stirring speed can be solved based on the relationship model.

[0068] In the prior art, when carrying out multi-layer coating of flaky aluminum powder, a fixed stirring speed is usually used. However, in actual application, if the stirring speed is too low, it is easy to cause the standard deviation of the coating layer thickness to be too large, thereby causing uneven coating. If the stirring speed is too high, the structure of the aluminum powder is easily damaged. The relationship model of the embodiment can quantitatively correlate N and σ, so that the stirring speed can be accurately controlled. On the premise of ensuring the integrity of the aluminum powder, the thickness fluctuation is minimized, which is beneficial to improve the uniformity of the color transition of the color powder coating prepared finally.

[0069] In the process of composite metal salt co-deposition, insufficient stirring intensity may cause uneven deposition, and too strong stirring may damage the formed coating. Specifically, in the early stage of the reaction, the concentration of the reactant metal salt ions is high, and the reaction rate is fast, which may produce a large amount of gas or precipitate. Moderate stirring is needed to ensure uniform mixing, but too high stirring may cause particle breakage (such as flaky aluminum powder) or energy waste. In the later stage of the reaction, the concentration of the reactant metal salt decreases, and the reaction rate slows down, but at this time the system may become viscous or the particles may be easily settled, so stronger stirring is needed to maintain uniform dispersion and reaction conditions.

[0070] Therefore, the stirring intensity can be automatically adjusted according to the progress of the composite metal salt co-deposition to avoid manual intervention. Lower stirring intensity is used when the metal salt concentration is high to reduce the deformation or breakage of flaky aluminum powder caused by strong shear force, and in the later stage of the reaction, the stirring is appropriately strengthened to overcome the mass transfer limitation caused by the increase in viscosity and ensure complete reaction.

[0071] For example, the stirring speed is automatically adjusted according to the formula . Wherein, represents the adjusted stirring speed, represents the basic stirring speed, i.e. the minimum stirring intensity preventing particle sedimentation at the lower limit of the safe speed. represents the intensity adjustment amplitude, i.e. the maximum speed range allowed to increase. represents the average value of the mixed concentration of metal ions at time t, which can be obtained by real-time monitoring or based on a color gradient model. represents the average value of the initial concentration, i.e. the average value of the initial concentration of multiple metal ions at the beginning of the reaction.

[0072] Preferably, the basic stirring speed is obtained based on a relationship model between the standard deviation σ of the coating layer thickness and the reactor stirring speed N, i.e. the basic stirring speed is the minimum stirring speed that can be solved based on the relationship model. In this way, based on the adjusted stirring speed, the thickness fluctuation can be minimized under the premise of ensuring the integrity of the aluminum powder, the uniformity of the color transition of the finally prepared color powder coating is improved, and the particle sedimentation is prevented, realizing the concentration-dependent dynamic speed regulation and balancing the reaction efficiency and structural protection.

[0073] As a preferred technical solution, the preparation device further comprises a mixing treatment device, a twin-screw extruder, a cooling treatment device, and a crushing treatment device.

[0074] The mixing treatment device is used to mix the obtained modified aluminum pigment with the powder substrate to obtain a mixture; the twin-screw extruder is used to extrude the mixture to obtain a coating in a molten state; the cooling treatment device is used to cool the coating in the molten state; and the crushing treatment device is used to crush the cooled coating to obtain a powder coating with a certain particle size.

[0075] The powder substrate includes but is not limited to epoxy-polyester resin and leveling agent. In the mixture, the content of the modified aluminum pigment is 30wt%, the content of the epoxy-polyester resin is 65wt%, and the content of the leveling agent is 5wt%. When the mixture is extruded by the twin-screw extruder, the temperature is set to be between 110°C and 120°C. Finally, the particle size of the obtained powder coating can be set to be 35μm.

[0076] The preparation device of the metal texture color powder coating performs co-deposition treatment by adding composite metal salt to coat the surface of the flaky aluminum powder with a composite metal oxide layer. By adjusting the gradient change of the proportion of various types of metal salts in the composite metal salt, the color transition effect can be achieved, and the color richness can be improved.

[0077] By the mixing treatment device, the twin-screw extruder, the cooling treatment device, and the crushing treatment device, the color powder coating with metal texture and meeting the particle size requirements can be prepared.

[0078] The specific structure of the mixing device, the twin-screw extruder, the cooling device and the crushing device are all conventional technical means in the field, and thus will not be described here.

[0079] In one embodiment, the preparation device further comprises a cyclone separator for separating the crushed color powder coating. Assuming that the target particle size of the powder coating obtained by crushing the coating after the cooling treatment by the crushing device is , the target particle size function can be expressed as , wherein the target particle size is generally between 15-50 microns. represents the dynamic viscosity of air, which is a fluid property parameter, representing the viscosity of air, and under standard conditions (20°C), the dynamic viscosity of air is about 1.8×10-5 Pa·s. represents the radial wind speed (unit: m / s, ), which can be understood as the radial flow rate of the fluid, i.e. the radial velocity component of the airflow from to . represents the density of aluminum powder particles, represents the angular velocity of rotation. represents the inner radius of the separator cylinder, represents the radius of the central outlet pipe, represents the square difference of the effective radial distance of the separation area.

[0080] Specifically, for every 10 degrees Celsius increase in temperature, the dynamic viscosity of air increases by 3%, at which point the angular velocity of rotation needs to be reduced to compensate. For the density of aluminum powder particles, since the aluminum powder has a silica layer, a composite metal salt layer, and a polymer resin layer, the density of the aluminum powder particles can be obtained by calculating the weighted values of the aluminum density, the silica layer density, the composite metal salt density, and the polymer resin layer density. In this way, the separation accuracy and quality of the cyclone separator can be improved. The weight coefficients corresponding to the aluminum density, the silica layer density, the composite metal salt layer density, and the polymer resin layer density can be determined according to their thickness proportions, i.e. the weight coefficients corresponding to the aluminum density, the silica layer density, the composite metal salt layer density, and the polymer resin layer density are equal to their corresponding thickness proportions.

[0081] The target particle size function is used to calculate the cutting particle size of the cyclone separator under given operating conditions (angular velocity of rotation and radial wind speed) and fluid properties (dynamic viscosity of air and density of aluminum powder particles) and device sizes (inner radius of the separator cylinder and radius of the central outlet pipe), which helps to adjust parameters such as angular velocity of rotation or radial wind speed according to the target cutting particle size (e.g. 20 microns).

[0082] Based on the target particle size function, the theoretical angular velocity of rotation The centrifugal force and the aerodynamic resistance are balanced at the target particle size. Considering that there is a certain deviation between the actual monitoring particle size and the target particle size The real-time particle size deviation can be compensated to quickly respond to the change trend of the particle size deviation, so that when the actual particle size deviates positively from the target, the centrifugal separation is strengthened by increasing ω, and when the actual particle size deviates negatively from the target, the centrifugal separation is weakened by reducing ω.

[0083] Exemplarily, the compensated angular velocity ω is , wherein, PID represents a gain coefficient, which is used to control the system sensitivity parameter and can be calibrated by experiment or set according to experience. The deviation rate represents the rate of change of the particle size deviation with time.

[0084] The particle size deviation is compensated for the angular velocity ω, which can accurately calculate the separation condition according to the material characteristics and quickly respond to the sudden disturbance, and realizes the accurate control of the target particle size in the cyclone separation process.

[0085] The technical features of the embodiments can be combined in any way. In order to make the description simple, all possible combinations of the technical features in the above embodiments are not described, but as long as the combination of the technical features does not exist, it should be considered as the scope of the description.

[0086] The above-described embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as limiting the scope of the patent. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of the present application. Therefore, the scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for producing a metallic color powder coating, characterized by, The preparation method comprises: S1, dispersing the flaky aluminum powder in an alcohol solvent, adding a silicon source to perform a hydrolysis reaction, so as to coat a silicon dioxide layer on the surface of the flaky aluminum powder; S2, dispersing the flaky aluminum powder coated with the silicon dioxide layer after the step S2 treatment into water, adding a composite metal salt to perform a co-deposition treatment, so as to coat a composite metal oxide layer on the surface of the flaky aluminum powder; S3, dispersing the flaky aluminum powder coated with the silicon dioxide layer and the composite metal oxide layer after the step S2 treatment into an organic solvent, and adding an acrylic monomer, a styrene monomer and an initiator to perform a polymerization reaction, so as to coat a polymer resin layer on the surface of the composite metal oxide layer, thereby obtaining a modified aluminum pigment.

2. A method of preparing a metallic color powder paint according to claim 1, characterized in that, The preparation method further comprises: S4, mixing the obtained modified aluminum pigment with a powder base material to obtain a mixture; S5, performing an extrusion treatment on the mixture by using a double screw extruder to obtain a coating in a molten state; S6, performing a cooling treatment on the coating in the molten state and performing a crushing treatment on the cooled coating to obtain a powder coating with a certain particle size.

3. A method of preparing a metallic color powder paint according to claim 2, characterized in that, The specific method for adding the composite metal salt to perform the co-deposition treatment comprises: obtaining the number of metal salt types of the composite metal salt to be added; obtaining the initial concentration and the deposition rate coefficient of each metal ion; constructing a color gradient gradient model according to the number of metal salt types, the initial concentration and the deposition rate coefficient; obtaining the instantaneous concentration value of each metal ion according to the color gradient gradient model.

4. The method of preparing a metallic color powder paint according to claim 3, characterized in that, The preparation method further comprises: based on the color gradient gradient model, realizing the color gradient gradient by adjusting the flow rate of the metal salt solution.

5. A process for the preparation of a metallic color powder paint according to claim 4, characterized in that, The composite metal salt is composed of ferric chloride and tin tetrachloride, the mass ratio of ferric chloride and tin tetrachloride is 3:1, the pH value of the deposition treatment is 4, the temperature is 85 , and the time is 20 min.

6. The method of preparing a metallic color powder paint according to claim 4, wherein the metal powder is prepared by the steps of: The composite metal salt is composed of cobalt dichloride and chromium trichloride, and the mass ratio of cobalt dichloride and chromium trichloride is 2:1, the pH value of the deposition treatment is 4.5, the temperature is 82 , and the time is 25 min. ​ 7. The method for preparing a metallic-textured colored powder coating as described in claim 2, characterized in that, The powder base material comprises an epoxy-polyester resin and a leveling agent.

8. An apparatus for the production of a metallic color powder coating for the realization of the production method according to any one of claims 1 to 7, characterized in that The preparation device comprises: a flaky aluminum powder pretreatment device for dispersing the flaky aluminum powder in an alcohol solvent, adding a silicon source to perform a hydrolysis reaction, so as to coat a silicon dioxide layer on the surface of the flaky aluminum powder; a metal oxide deposition device for dispersing the flaky aluminum powder coated with the silicon dioxide layer after the pretreatment into water, adding a composite metal salt to perform a co-deposition treatment, so as to coat a composite metal oxide layer on the surface of the flaky aluminum powder; a resin polymerization treatment device for dispersing the flaky aluminum powder coated with the silicon dioxide layer and the composite metal oxide layer into an organic solvent, and adding an acrylic monomer, a styrene monomer and an initiator to perform a polymerization reaction, so as to coat a polymer resin layer on the surface of the composite metal oxide layer, thereby obtaining a modified aluminum pigment.

9. A metal texture color powder paint preparation apparatus according to claim 8, characterized in that, The preparation device further comprises: a mixing treatment device for mixing the obtained modified aluminum pigment with a powder base material to obtain a mixture; a double screw extruder for performing an extrusion treatment on the mixture to obtain a coating in a molten state; a cooling treatment device for performing a cooling treatment on the coating in the molten state; a crushing treatment device for performing a crushing treatment on the cooled coating to obtain a powder coating with a certain particle size.

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