Ammonium zinc phosphate pigment for waterborne epoxy coating and synthesis method of ammonium zinc phosphate pigment

Abstract

The synthesis method comprises the following steps: preparing a zinc ion solution with the pH value of 1-5, preparing an ammonium ion solution with the pH value of 1-5, preparing a phosphate ion solution with the pH value of 7-14, mixing the ammonium ion solution with the zinc ion solution to obtain a mixed solution, adding the mixed solution into the zinc ion solution, and uniformly stirring to obtain the ammonium zinc phosphate pigment for the waterborne epoxy coating. Atomizing and spraying the phosphate ion solution into the mixed solution to obtain an ammonium zinc phosphate solution, putting the ammonium zinc phosphate solution into an ultrasonic oscillation and microwave heating auxiliary device for ultrasonic refining, heating, preserving heat, filtering precipitates in the ammonium zinc phosphate solution, and drying to obtain the ammonium zinc phosphate pigment. The invention aims to solve the problems of large particle size, low solubility, weak hydrolytic ability and poor compatibility between an inorganic pigment and an organic resin interface in the curing process of the ammonium zinc phosphate pigment prepared by the existing method, so that the corrosion protection capability of a new generation of zinc phosphate salt-based inorganic pigment in a waterborne epoxy coating is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of anticorrosive inorganic pigment synthesis, and particularly relates to an ammonium zinc phosphate pigment for waterborne epoxy coatings and a synthesis method thereof. Background Art

[0002] In the field of coatings, waterborne epoxy coatings have attracted much attention due to their environmental advantages, and anti-rust pigments are crucial to improving the anti-corrosion performance of coatings. As a type of material with anti-rust potential, zinc ammonium phosphate inorganic pigments have been tried to be used in waterborne epoxy coatings. However, there are many defects in their current application: First, from the perspective of solubility, the solubility of zinc phosphate inorganic pigment in aqueous solution is low (solubility product Ksp = 9.1×10 -33 ), which makes it difficult to quickly and fully release the active ingredient Zn in the waterborne epoxy coating system. 2+ and (PO4) 3- , and thus cannot fully react with the metal substrate in time to form an effective protective film, resulting in insufficient initial protection for the metal.

[0003] Secondly, from the perspective of compatibility, it is difficult to construct a strong coordination bond between the crystals of zinc phosphate pigment and water-based epoxy coating, which makes it difficult to form a good interface bond between zinc phosphate inorganic pigment and water-based epoxy resin. The chemical structures of the two are quite different, which makes it easy for pigment particles to agglomerate or distribute unevenly in the coating during the film-forming process of the coating. This unevenness not only affects the appearance quality of the coating, but more importantly, it will form weak areas inside the coating, such as a large number of pinholes, holes and other structural defects, which greatly reduces the overall protective performance of the coating.

[0004] Furthermore, from the perspective of the pigment's own characteristics, the crystal structure of zinc phosphate inorganic pigment is not regular enough, and its particle size distribution is often wide and difficult to accurately control. This makes it impossible to guarantee that each addition can achieve the ideal anti-rust effect in the coating application. Larger particles may not be able to be finely filled into the coating microstructure, affecting the density of the coating. In view of these problems, how to effectively improve the solubility and hydrolysis ability of zinc phosphate pigments in aqueous solution, further refine the grain size of zinc phosphate pigments, and properly improve the compatibility between inorganic pigments and organic epoxy resin interfaces has become the key to further expanding the application of new generation zinc phosphate-based pigments in new water-based epoxy coatings. Summary of the invention

[0005] The purpose of the present invention is to provide an ammonium zinc phosphate pigment for waterborne epoxy coatings and a synthesis method thereof, aiming to solve the problems of zinc phosphate pigments prepared by existing methods, such as large particle size, low solubility, weak hydrolysis ability, and poor compatibility between the inorganic pigment and the organic resin interface during the curing process, thereby improving the corrosion protection ability of a new generation of zinc phosphate-based inorganic pigments in waterborne epoxy coatings.

[0006] To achieve the above objectives, the present technical solution provides a method for synthesizing zinc ammonium phosphate pigment for water-based epoxy coatings, comprising the following steps: Preparing a zinc ion solution: mixing deionized water, a soluble zinc salt and a cationic surfactant to obtain a zinc ion solution, wherein the pH value of the zinc ion solution is 1-5; Prepare an ammonium ion solution: mix deionized water, a soluble ammonium salt and ammonia water to obtain an ammonium ion solution, wherein the pH value of the ammonium ion solution is 1-5; Preparing a phosphate ion solution: mixing deionized water, phosphoric acid, a soluble phosphate and an organic solvent to obtain a phosphate solution, wherein the pH value of the phosphate ion solution is 7-10; preparing the ammonium zinc phosphate solution: mixing the ammonium ion solution with the zinc ion solution to obtain a mixed solution, spraying the phosphate ion solution into the mixed solution to obtain the ammonium zinc phosphate solution, and placing the ammonium zinc phosphate solution in an ultrasonic oscillation and microwave heating auxiliary device for ultrasonic refinement, heating and heat preservation; Precipitating zinc ammonium phosphate pigment: filtering the precipitate in the zinc ammonium phosphate solution and drying it to obtain the zinc ammonium phosphate pigment.

[0007] The synthesized zinc ammonium phosphate pigment for waterborne epoxy coatings provided in the present invention has a stable three-dimensional spatial structure, high solubility in aqueous solution, strong hydrolysis ability, and the ability to improve the compatibility between interfaces by forming hydrogen bonds between ammonium radicals and organic resins. Meanwhile, a large amount of phosphate ions generated by hydrolysis can form a complete passivation film on the surface of the metal substrate, thereby significantly improving the corrosion protection effect of the waterborne epoxy coating.

[0008] In the step of “preparing the zinc ion solution”, a first pH adjuster is added to the zinc ion solution to control the pH value of the zinc ion solution to be 1-5, so as to effectively inhibit the hydrolysis of zinc ions to form zinc hydroxide precipitation.

[0009] Specifically, zinc ions exist in a hydrolysis equilibrium in a zinc ion solution. When the pH value of the zinc ion solution increases, zinc ions are easily combined with hydroxide ions to undergo a hydrolysis reaction to form zinc hydroxide precipitation. In the zinc ammonium phosphate pigment synthesis scheme involved in this scheme, in order to ensure that there is a sufficient and stable zinc ion concentration in the zinc ion solution to participate in the subsequent reaction with ammonium ions, phosphate ions, etc., the pH value of the zinc ion solution is controlled to be a relatively acidic environment of 1 to 5. In this way, zinc ions can exist in a relatively stable ionic state in the solution, ensuring that when they are subsequently mixed with other ions, they can react according to the expected stoichiometric ratio, avoiding problems such as inaccurate composition or reduced yield of the synthesized zinc ammonium phosphate pigment due to the reduction of zinc ion concentration due to hydrolysis, and in this pH range, the activity of zinc ions is in a relatively suitable state, and the reaction will not be difficult to control due to excessive acidity and excessive activity, nor will unnecessary hydrolysis and other side reactions occur due to being close to neutral or alkaline.

[0010] In some embodiments, the first pH adjuster is selected from one or more of nitric acid, sulfuric acid, hydrochloric acid, acetic acid, citric acid, tartaric acid, malic acid, succinic acid, and lactic acid.

[0011] In the "preparation of zinc ion solution", the soluble zinc salt is selected from one or both of inorganic soluble zinc salt and organic soluble zinc salt.

[0012] In addition, when the soluble zinc salt is an inorganic soluble zinc salt, the soluble zinc salt, the complexing agent and the surfactant are mixed to obtain a zinc ion solution, and the complexing agent is a complexing agent with weak acid properties and does not contain sodium ions. This has the advantage of maintaining the zinc ion Zn in the solution. 2+ and ammonium ion NH4 + It exists stably and effectively inhibits the agglomeration of nano-ammonium zinc phosphate crystals during their growth, making it easier to prepare micro-nano-grade ammonium zinc phosphate pigments with three-dimensional structures.

[0013] Specifically, the weakly acidic complexing agent can form a specific complex structure with zinc ions and ammonium ions, just like creating a "stabilizer" for them, allowing them to exist stably in the solution and ensuring sufficient and stable ion supply for subsequent reactions. At the same time, when the nano zinc ammonium phosphate crystals grow, the complexing agent can change the ion distribution and crystal surface properties, reduce the possibility of mutual attraction and aggregation between crystal nuclei due to uneven local ion concentrations, and form a similar "protective film" on the crystal surface, effectively inhibiting agglomeration, which is conducive to the preparation of micro-nano zinc ammonium phosphate pigments with three-dimensional structures.

[0014] When the soluble zinc salt is an organic soluble zinc salt, the zinc ion solution does not contain a complexing agent or contains only a small amount of a complexing agent. This is because the organic soluble zinc salt itself carries various organic groups, which will produce specific interactions with zinc ions in the solution, so that the existence state and reaction activity of zinc ions have been regulated to a certain extent, and there is no need to add a large amount of complexing agents to maintain the stability of related ions and inhibit crystal agglomeration as when using inorganic soluble zinc salts.

[0015] In addition, the inorganic soluble zinc salt includes one of zinc chloride, zinc sulfate, zinc nitrate, zinc bromide, zinc perchlorate, or a combination of several of them in a compatible condition. The organic soluble zinc salt includes one of zinc acetate, zinc gluconate, zinc lactate, zinc propionate, zinc citrate, zinc formate dihydrate, zinc hexafluorosilicate, zinc salicylate, or a combination of several of them in a compatible condition.

[0016] In some embodiments, the complexing agent is selected from one or more of acetic acid, gluconic acid, lactic acid, citric acid, salicylic acid, propionic acid, and tartaric acid.

[0017] In the step of "preparing zinc ion solution", the cationic surfactant is selected as one or more of dodecylquinolinium bromide, fatty amine salt, hexadecyltrimethylammonium chloride, and polyquaternary ammonium salt. It should be noted that since the pH value of the zinc ion solution is acidic, the present scheme selects a cationic surfactant that can be stably present in an acidic solution, and the addition of the cationic surfactant can effectively inhibit the growth of ammonium zinc phosphate crystals, thereby forming ammonium zinc phosphate nanocrystals with a smaller size, and at the same time effectively inhibiting the occurrence of nanocrystal agglomeration.

[0018] Specifically, cationic surfactants can effectively inhibit the growth of crystals through a variety of mechanisms. On the one hand, it will adsorb on the surface of the ammonium zinc phosphate crystal nucleus being formed, occupying part of the space on the surface of the crystal nucleus, so that the subsequent zinc ions, ammonium ions and phosphate ions are hindered when they are deposited and grown on the crystal nucleus, thereby limiting the growth rate of the crystal; on the other hand, the presence of cationic surfactants in the solution changes the diffusion rate and distribution of ions in the solution, causing the concentration gradient of ions to change when they are close to the crystal nucleus, further slowing down the growth process of the crystal. Through these effects, the goal of forming smaller ammonium zinc phosphate nanocrystals was successfully achieved. This small crystal size has many advantages, such as increasing the specific surface area of ​​the pigment, enabling it to interact more fully with other ingredients in water-based epoxy coatings, improving the dispersibility and reactivity of the pigment, and thus enhancing the anti-rust and anti-corrosion properties of the coating.

[0019] In addition to inhibiting crystal growth, cationic surfactants can reduce the surface energy of the crystal nucleus and weaken the mutual attraction between nanocrystals by adsorbing on the surface of the crystal nucleus. At the same time, its presence in the solution will also change the electrostatic field distribution in the solution, causing a certain electrostatic repulsion between the nanocrystals. This mechanism of increase and decrease allows the nanocrystals to maintain a relatively independent state in the solution, effectively inhibiting the occurrence of nanocrystal agglomeration, thereby ensuring that the prepared ammonium zinc phosphate nanocrystals have good uniformity and dispersibility, which is more conducive to improving their performance in applications such as water-based epoxy coatings.

[0020] In the "preparation of zinc ion solution", the zinc ion solution is placed in an auxiliary device with ultrasonic oscillation and microwave heating functions, and the temperature of the zinc ion solution is controlled to be 25°C to 50°C. This scheme adopts ultrasonic oscillation and microwave heating technology, and breaks the possible agglomeration phenomenon between solute particles through ultrasonic oscillation, so that solutes such as soluble zinc salts, complexing agents, and surfactants are more evenly dispersed in the solution. The temperature is adjusted to 25°C to 50°C by microwave heating, which can effectively prevent excessive hydrolysis of zinc ions. If the temperature is too high, exceeding 50°C, the possibility of zinc ions hydrolyzing to form zinc hydroxide precipitation will be greatly increased. This will not only lead to a decrease in the concentration of zinc ions in the solution, affecting subsequent reactions with ammonium ions, phosphate ions, etc., but may also introduce zinc hydroxide precipitation during the growth of ammonium zinc phosphate crystals, destroying the regularity and purity of the crystals. In the temperature range of 25°C to 50°C, the hydrolysis reaction can be effectively controlled to ensure that zinc ions exist in the solution in a stable ionic state, providing a sufficient and pure source of zinc ions for the synthesis of ammonium zinc phosphate pigments.

[0021] In some embodiments, the ultrasonic oscillation frequency is 20kHz to 130kHz; the microwave radiation heater power is 100W to 2000W.

[0022] In the "preparation of zinc ion solution", the mass ratio of soluble zinc salt, anionic surfactant and complexing agent is set between 3:1:1 and 5:1:1, and the content of the first pH value adjuster is to adjust the pH value to the specified range. This has the advantage of promoting the dissolution of zinc salt and Zn 2+ The ions are stable in the solution, reducing the Zn 2+ Ion concentration is used to prevent zinc phosphate crystals from agglomerating after they are generated. Specifically, in each liter of deionized water, the soluble zinc salt is 5g to 30g, the cationic surfactant is 1g to 10g or 5mL to 20mL, the complexing agent is 1g to 10g, and the first pH value adjuster is 1g to 10g or 1mL to 20mL.

[0023] In the step of "preparing the ammonium ion solution", a second pH adjuster is added to the ammonium ion solution so that the pH value of the ammonium ion solution is 1-5. This has the advantage of ensuring that the ammonium ions NH4 + Stable existence. This solution can effectively inhibit the hydrolysis reaction of ammonium ions by controlling the pH value of the ammonium ion solution within the acidic range of 1 to 5 by adding a second pH adjuster, so that the ammonium ions can exist in the solution in a relatively stable ionic state, ensuring that in the subsequent mixed reaction with zinc ion solution, etc., there are sufficient and stable ammonium ions to participate in the reaction of synthesizing zinc ammonium phosphate pigment, avoiding problems such as the reaction failing to proceed as expected or the product yield being reduced due to the escape of a large amount of ammonium ions hydrolyzed.

[0024] In some embodiments, the second pH adjuster is one or more of hydrochloric acid, sulfuric acid, and nitric acid.

[0025] In the step of "configuring ammonium ion solution", soluble ammonium salts include soluble inorganic ammonium salts and soluble organic ammonium salts, wherein the soluble inorganic ammonium salts are one of ammonium carbonate, ammonium bicarbonate, ammonium nitrate, ammonium sulfate, ammonium chloride, ammonium fluoride or a combination of several under compatible conditions, and the soluble organic ammonium salts are one of ammonium tartrate, ammonium oxalate, ammonium formate, ammonium citrate or a combination of several under compatible conditions. Soluble inorganic ammonium salts usually have good solubility and faster dissociation rate, and can quickly provide a large amount of ammonium ions in the initial stage of solution preparation, and although the dissociation rate of soluble organic ammonium salts may be relatively slow, they can continuously and stably release ammonium ions in the solution, thereby ensuring the provision of ammonium ions in the whole reaction process. And using soluble inorganic ammonium salts and soluble organic ammonium salts simultaneously, the growth process of crystals can be affected from different angles, making crystal growth more uniform and regular, reducing the appearance of crystal defects, and improving the crystal quality of zinc ammonium phosphate pigment.

[0026] In "preparing ammonium ion solution", the mass ratio of soluble inorganic ammonium salt or soluble organic ammonium salt and ammonia water is set between 1:1 and 5:1, and the role of this is mainly to provide ammonium ions. Specifically, in each liter of deionized water, 10g to 60g of soluble inorganic ammonium salt, 10g to 60g of soluble organic ammonium salt, 10mL to 100mL of ammonia water and 1g to 10g or 1mL to 20mL of the second pH adjuster are used.

[0027] In the step of "preparing phosphate ion solution", a third pH adjuster is added to the phosphate ion solution to make the pH value of the phosphate ion solution between 7 and 14. This has the advantage of effectively promoting the subsequent phosphate ion (PO4) 3- 、Ammonium ion NH4 + and zinc ion Zn 2+The reaction rate between them is increased, and a large amount of heat is released during the acid-base neutralization reaction, which increases the number of nucleation sites for ammonium zinc phosphate crystals and inhibits the growth of crystal nuclei, thereby forming nano-scale ammonium zinc phosphate crystals.

[0028] In some embodiments, the third pH adjuster is one or more of sodium hydroxide, potassium hydroxide, disodium hydrogen phosphate, dipotassium hydrogen phosphate, and ammonia water.

[0029] In the step of "preparing phosphate ion solution", the phosphoric acid is orthophosphoric acid, or a combination of orthophosphoric acid and metaphosphoric acid. Orthophosphoric acid can stably provide phosphate ions PO4 3- , ensuring the subsequent reaction with ammonium ions and zinc ions. Metaphosphoric acid can undergo polymerization in the solution to form metaphosphoric acid molecular chains with different polymerization degrees, which can decompose and release phosphate ions, enriching the supply of phosphate ions. When the two are combined, they can not only ensure a continuous and stable source of phosphate ions, but also flexibly adjust the concentration of phosphate ions through the special effect of metaphosphoric acid, which is conducive to the formation of high-quality zinc ammonium phosphate crystals.

[0030] In the step of "preparing the phosphate ion solution", the soluble phosphate is one of sodium phosphate, ammonium phosphate, potassium phosphate, sodium hydrogen phosphate, ammonium hydrogen phosphate, potassium hydrogen phosphate, sodium dihydrogen phosphate, ammonium dihydrogen phosphate, potassium dihydrogen phosphate, or a combination of several of them under compatible conditions.

[0031] In the step of "preparing phosphate ion solution", the organic solvent is one or more of ethanol, polyethylene glycol, glycerol, and ethyl acetate. The addition of organic solvent can dilute the phosphate ions (PO4) in the phosphate ion solution. 3- concentration, slowing down phosphate ions (PO4) 3- 、Ammonium ion NH4 + and zinc ion Zn 2+ The reaction rate between them is increased, and it is beneficial for the zinc ammonium phosphate grains to grow along the (101), (011) and (200) crystal planes, presenting a three-dimensional structure of zinc ammonium phosphate pigment formed by lamellar stacking.

[0032] In the step of "preparing phosphate ion solution", phosphate ions are placed in a magnetically stirred water bath, and the concentration of the phosphate ion solution is controlled to be between 25°C and 50°C. Within this temperature range, the degree of ionization of phosphate ions is relatively moderate. It will not ionize too slowly due to too low a temperature, resulting in insufficient concentration of phosphate ions in the solution for subsequent reactions; nor will it ionize too quickly due to too high a temperature, causing drastic changes in properties such as the pH of the solution, affecting the existence form and reaction activity of other ions. The activity of ammonium ions and zinc ions is also in a suitable state, and the interaction between them and phosphate ions can proceed more smoothly.

[0033] In some embodiments, the stirring speed of the magnetically stirred water bath is 50 r·min -1 Up to 1000 r·min -1 , heating power is 100W to 2000W.

[0034] In the step of "preparing phosphate ion solution", the mass ratio of phosphoric acid, soluble phosphate, and organic solvent is set between 3:1:1 and 5:1:1, and the content of the third pH value adjuster is to adjust the pH value to the specified range. This is to increase the phosphate concentration in the solution and promote the reaction of phosphate with Zn 2+ and NH4 + The reaction speed between ions; improve the pH value of the phosphate solution, maintain alkalinity, promote the generation of heat during the reaction, and provide energy for the nucleation of zinc ammonium phosphate grains. Specifically, in each liter of deionized water, the phosphoric acid is 0.01L~0.1L, the soluble phosphate is 5g~30g, the organic solvent is 5mL~50mL, and the third pH value adjuster is 1g~20g or 1mL~20mL.

[0035] In the step of "preparing ammonium zinc phosphate solution", the ammonium zinc phosphate solution is placed in an ultrasonic oscillation and microwave heating auxiliary device for ultrasonic refinement, heating and heat preservation, and the temperature of the zinc phosphate solution is controlled to be 25°C~50°C, and the heat preservation time is 0.1h~24h. This scheme reduces the temperature of the zinc phosphate solution to prevent the volatilization of ammonium ions, inhibit the formation of zinc phosphate crystals, and improve the purity of ammonium zinc phosphate. In the step of "preparing the zinc ammonium phosphate solution", an air compressor spray device is used to atomize the phosphate ion solution and spray it into the mixed solution to obtain the zinc ammonium phosphate solution.

[0036] In the step of "precipitating zinc ammonium phosphate pigment", the precipitate in the zinc ammonium phosphate solution is filtered, and the precipitate is placed in a drying oven for drying, wherein the temperature of the drying oven is 50°C to 200°C.

[0037] In addition, the present invention provides a zinc ammonium phosphate pigment for waterborne epoxy coatings, which is synthesized according to the above-mentioned synthesis method of zinc ammonium phosphate pigment for waterborne epoxy coatings, has a three-dimensional spatial structure, and a specific surface area of ​​50m 2 ·g -1 ~ 220 m 2 ·g -1 , length and width are 0.1μm ~ 5.0μm, thickness is 10 nm ~ 200nm. The common micron-grade zinc phosphate on the market has a small specific surface area, generally between 1.5-10 m² / g, and the specific surface area of ​​the two-dimensional sheet-like micro-nano-grade zinc phosphate on the market is between 8.7-39 m² / g.

[0038] Compared with the prior art, this technical solution has the following characteristics and beneficial effects: The synthesis method of the zinc ammonium phosphate pigment for waterborne epoxy coatings optimizes crystal growth, refines grains and increases specific surface area by precisely controlling reaction conditions. In this scheme, the pH value is precisely adjusted in each ion solution configuration and appropriate component reagents are selected to inhibit the growth of zinc ammonium phosphate crystals, form fine nanocrystals, increase specific surface area, and improve dispersibility and reactivity in waterborne epoxy coatings. The prepared zinc ammonium phosphate pigment has high solubility in aqueous solution and strong hydrolysis ability. The phosphate ions produced by hydrolysis can form a complete passivation film on the surface of the base metal, effectively block corrosive ions, and significantly improve the corrosion protection effect of organic coatings. At the same time, the ammonium phosphate can form hydrogen bonds with organic resins to improve interfacial compatibility, ensure uniform dispersion and close combination in waterborne epoxy coatings, avoid compatibility problems, and ensure coating performance. When the zinc ammonium phosphate pigment of this scheme is applied to waterborne epoxy coatings, it can significantly improve its corrosion protection effect, resist external erosion, extend the service life of metal products, and have a good physical barrier effect on corrosive ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 3. It is a scanning electron microscope image of the micro-nano three-dimensional flower-like structure ammonium zinc phosphate pigment according to Example 1 of the present invention.

[0040] Figure 2 1 is the XRD spectrum of the micro-nano three-dimensional flower-like structure ammonium zinc phosphate pigment according to Example 1 of the present invention.

[0041] Figure 3 This is a scanning electron microscope image of the micro-nano three-dimensional spherical structure ammonium zinc phosphate pigment of Example 2 of the present invention. DETAILED DESCRIPTION

[0042] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0043] It is to be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the element may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0044] Example 1 Prepare zinc ion solution: take a clean beaker with a capacity of 10L, add 1L of deionized water into the beaker, and then add 10g of zinc chloride, 10mL of polyethylene glycol, and 2g of sodium acetate in sequence. Use acetic acid to adjust the pH value of the solution to 2, which is recorded as zinc ion solution. Use ultrasonic oscillation and microwave heating auxiliary equipment to ultrasonically refine and heat the zinc ion solution and maintain the temperature at 50°C.

[0045] Prepare ammonium ion solution: take a clean beaker with a capacity of 10L, add 1L of deionized water into the beaker, then add 20g of ammonium carbonate and 30mL of ammonia water in sequence, and adjust the pH value of the solution to 2 with dilute hydrochloric acid. This is recorded as ammonium ion solution.

[0046] Prepare phosphate ion solution: take a clean beaker with a capacity of 10L, add 1L of deionized water to the beaker, then add 5mL of phosphoric acid, 20g of diammonium phosphate, 20mL of ethanol, and adjust the pH value of the solution to 11 with sodium hydroxide, record it as phosphate ion solution, and heat the phosphate ion solution in a magnetic stirring water bath, maintain the temperature at 50℃, and stir at a speed of 500 r·min -1 ; Preparation of ammonium zinc phosphate solution: introduce ammonium ion solution into zinc ion solution to form a mixed solution, use air compressor spray device to atomize phosphate ion solution and spray it into the mixed solution to form ammonium zinc phosphate solution, continue to use ultrasonic oscillation and microwave heating auxiliary device to ultrasonically refine and heat the ammonium zinc phosphate solution and maintain the temperature at 50°C.

[0047] Obtaining ammonium zinc phosphate: Filter the precipitate in the ammonium zinc phosphate solution using a vacuum filtration device, and dry the precipitate in a drying oven, with the temperature of the drying oven set to 100°C.

[0048] Example 1 of the present invention uses an ultrasonic vibration and microwave heating-assisted method to synthesize a zinc ammonium phosphate pigment having a micro-nano three-dimensional flower-like structure, such as Figure 1 As shown, Figure 1 This is a scanning electron microscope image of the micro-nano three-dimensional flower-like structure of ammonium zinc phosphate pigment. Figure 2 This is the XRD spectrum of the micro-nano three-dimensional flower-like structure zinc ammonium phosphate pigment. It can be seen that the grain size of the flower-like structure zinc ammonium phosphate pigment is further refined, with a stable three-dimensional spatial structure, high solubility in aqueous solution, strong hydrolysis ability, and on the one hand, it can improve the compatibility between interfaces by forming hydrogen bonds between ammonium groups and organic resins; on the other hand, a large number of phosphate ions produced by hydrolysis can form a complete passivation film on the surface of the base metal, thereby significantly improving the corrosion protection effect of the organic coating.

[0049] Example 2 Prepare zinc ion solution, take a clean beaker with a capacity of 10L, add 1L of deionized water into the beaker, and then add 10g of zinc citrate, 5g of sodium dodecylbenzene sulfonate, and 3g of sodium citrate in sequence. Adjust the pH value of the solution to 3 with citric acid, and record it as zinc ion solution. Use ultrasonic oscillation and microwave heating auxiliary equipment to ultrasonically refine and heat the zinc ion solution and maintain the temperature at 30°C.

[0050] Prepare the ammonium ion solution, take a clean beaker with a capacity of 10L, add 1L of deionized water into the beaker, then add 20g of ammonium citrate and 50mL of ammonia water in sequence, and adjust the pH value of the solution to 3 with dilute hydrochloric acid. Record it as the ammonium ion solution.

[0051] Prepare phosphate ion solution, take a clean beaker with a capacity of 10L, add 1L of deionized water to the beaker, then add 5mL of phosphoric acid, 20g of diammonium phosphate, 10mL of ethyl acetate, and adjust the pH value of the solution to 8 with sodium hydroxide, which is recorded as phosphate ion solution. Heat the phosphate ion solution in a magnetic stirring water bath, maintain the temperature at 30℃, and stir at a speed of 500 r·min -1 .

[0052] Prepare ammonium zinc phosphate solution, wait until the solid is completely dissolved, introduce ammonium ion solution into zinc ion solution to form a mixed solution, use an air compressor spray device to atomize the phosphate ion solution and spray it into the mixed solution to form ammonium zinc phosphate solution, continue to use ultrasonic oscillation and microwave heating auxiliary devices to ultrasonically refine and heat the ammonium zinc phosphate solution and maintain the temperature at 30°C.

[0053] Obtain ammonium zinc phosphate, filter the precipitate in the ammonium zinc phosphate solution using a vacuum filtration device, and dry the precipitate in a drying oven, where the temperature of the drying oven is set to 100°C.

[0054] Example 2 of the present invention uses an ultrasonic vibration and microwave heating-assisted method to synthesize a zinc ammonium phosphate pigment with a micro-nano three-dimensional spherical structure. The scanning electron microscope image of the spherical zinc ammonium phosphate pigment grains is as follows: Figure 3 As shown, it can be seen that the grain size of the spherical ammonium zinc phosphate pigment is further refined, with a stable three-dimensional spatial structure, high solubility in aqueous solution, strong hydrolysis ability, on the one hand, it can form hydrogen bonds between ammonium radicals and organic resins to improve the compatibility between interfaces; on the other hand, a large number of phosphate ions produced by hydrolysis can form a complete passivation film on the surface of the base metal, thereby significantly improving the corrosion protection effect of the organic coating.

[0055] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, all technical solutions that are the same or similar to those of the present application fall within the protection scope of the present invention.

Claims

1. A method for synthesizing zinc ammonium phosphate pigment for waterborne epoxy coatings, characterized in that: The following steps are involved: Preparing a zinc ion solution: mixing deionized water, a soluble zinc salt and a cationic surfactant to obtain a zinc ion solution, wherein the pH value of the zinc ion solution is 1-5; Prepare an ammonium ion solution: mix deionized water, a soluble ammonium salt and ammonia water to obtain an ammonium ion solution, wherein the pH value of the ammonium ion solution is 1-5; Preparing a phosphate ion solution: mixing deionized water, phosphoric acid, a soluble phosphate and an organic solvent to obtain a phosphate solution, wherein the pH value of the phosphate ion solution is 7-10; preparing the ammonium zinc phosphate solution: mixing the ammonium ion solution with the zinc ion solution to obtain a mixed solution, spraying the phosphate ion solution into the mixed solution to obtain the ammonium zinc phosphate solution, and placing the ammonium zinc phosphate solution in an ultrasonic oscillation and microwave heating auxiliary device for ultrasonic refinement, heating and heat preservation; Precipitating zinc ammonium phosphate pigment: filtering the precipitate in the zinc ammonium phosphate solution and drying it to obtain the zinc ammonium phosphate pigment.

2. The method for synthesizing the zinc ammonium phosphate pigment for waterborne epoxy coating according to claim 1, characterized in that: A first pH adjuster is added to the zinc ion solution, wherein the first pH adjuster is selected from one or more of nitric acid, sulfuric acid, hydrochloric acid, acetic acid, citric acid, tartaric acid, malic acid, succinic acid, and lactic acid; a second pH adjuster is added to the ammonium ion solution, wherein the second pH adjuster is selected from one or more of hydrochloric acid, sulfuric acid, and nitric acid; and a third pH adjuster is added to the phosphate ion solution, wherein the third pH adjuster is selected from one or more of sodium hydroxide, potassium hydroxide, disodium hydrogen phosphate, dipotassium hydrogen phosphate, and ammonia water.

3. The method for synthesizing zinc ammonium phosphate pigment for waterborne epoxy coating according to claim 1, characterized in that: The soluble zinc salt is selected from one or both of an inorganic soluble zinc salt and an organic soluble zinc salt. When the soluble zinc salt is an inorganic soluble zinc salt, the soluble zinc salt, a complexing agent and a surfactant are mixed to obtain a zinc ion solution, wherein the complexing agent is a weakly acidic complexing agent that does not contain sodium ions.

4. The method for synthesizing zinc ammonium phosphate pigment for waterborne epoxy coating according to claim 1, characterized in that: The cationic surfactant is selected from one or more of dodecylquinolinium bromide, fatty amine salt, hexadecyltrimethylammonium chloride, and polyquaternary ammonium salt.

5. The method for synthesizing zinc ammonium phosphate pigment for waterborne epoxy coating according to claim 1, characterized in that: The zinc ion solution is placed in an auxiliary device with ultrasonic oscillation and microwave heating functions, and the temperature of the zinc ion solution is controlled to be between 25°C and 50°C; the phosphate ions are placed in a magnetically stirred water bath, and the concentration of the phosphate ion solution is controlled to be between 25°C and 50°C.

6. The method for synthesizing zinc ammonium phosphate pigment for waterborne epoxy coating according to claim 1, characterized in that: The soluble ammonium salts include soluble inorganic ammonium salts and soluble organic ammonium salts, wherein the soluble inorganic ammonium salt is one of ammonium carbonate, ammonium bicarbonate, ammonium nitrate, ammonium sulfate, ammonium chloride, and ammonium fluoride, or a combination of several of them under compatible conditions, and the soluble organic ammonium salt is one of ammonium tartrate, ammonium oxalate, ammonium formate, and ammonium citrate, or a combination of several of them under compatible conditions.

7. The method for synthesizing zinc ammonium phosphate pigment for waterborne epoxy coating according to claim 1, characterized in that: The organic solvent is one or more of ethanol, polyethylene glycol, glycerol and ethyl acetate.

8. The method for synthesizing zinc ammonium phosphate pigment for waterborne epoxy coating according to claim 1, characterized in that: The phosphoric acid is orthophosphoric acid, or a combination of orthophosphoric acid and metaphosphoric acid.

9. The method for synthesizing zinc ammonium phosphate pigment for waterborne epoxy coating according to claim 1, characterized in that: In the "preparation of zinc ion solution", the mass ratio of soluble zinc salt and anionic surfactant is set between 3:1:1 and 5:1:1; in the "preparation of ammonium ion solution", the mass ratio of soluble ammonium salt and ammonia water is set between 1:1 and 5:1; in the "preparation of phosphate ion solution" step, the mass ratio of phosphoric acid, soluble phosphate and organic solvent is set between 3:1:1 and 5:1:

1.

10. A zinc ammonium phosphate pigment for waterborne epoxy coatings, characterized in that: The zinc ammonium phosphate pigment for waterborne epoxy coatings is synthesized according to the synthesis method of any one of claims 1 to 9 and has a three-dimensional structure.

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