Zinc ammonium phosphate pigments for waterborne epoxy coatings and methods of synthesizing the same

Abstract

The application discloses a kind of ammonium zinc phosphate pigments for waterborne epoxy coating and synthesis method thereof, including the configuration pH value is 1~5 zinc ion solution, the configuration pH value is 1~5 ammonium ion solution, the configuration pH value is 7~14 phosphate ion solution, ammonium ion solution is mixed with zinc ion solution to obtain mixed solution, phosphate ion solution is atomized and sprayed into mixed solution to obtain ammonium zinc phosphate solution, and ammonium zinc phosphate solution is placed in ultrasonic vibration and microwave heating auxiliary device to carry out ultrasonic refinement, heating and carry out heat preservation, filter the precipitate in ammonium zinc phosphate solution and carry out drying to obtain ammonium zinc phosphate pigment, to solve the problem that the particle size of the ammonium zinc phosphate pigment prepared by the existing method is coarse, the solubility is low, the hydrolysis ability is weak, and the compatibility between the inorganic pigment and the organic resin interface during the curing process is poor, so as to improve the corrosion protection ability of the new generation of ammonium zinc phosphate inorganic pigment in waterborne epoxy coating.

Description

Technical Field

[0001] This invention belongs to the field of anti-corrosion inorganic pigment synthesis technology, and specifically relates to a zinc ammonium phosphate pigment for water-based epoxy coatings and its synthesis method. Background Technology

[0002] In the coatings industry, waterborne epoxy coatings have attracted much attention due to their environmental advantages. Rust-preventive pigments are crucial for improving the corrosion resistance of coatings. Zinc ammonium phosphate inorganic pigments, as a type of material with rust-preventive potential, have been explored for application in waterborne epoxy coatings. However, their current application has several drawbacks:

[0003] First, from a solubility perspective, zinc phosphate inorganic pigments have low solubility in aqueous solutions (solubility product Ksp = 9.1 × 10⁻⁶). -33 This makes it difficult for it to quickly and fully release the active ingredient Zn in waterborne epoxy coating systems. 2+ and (PO4) 3- Consequently, it cannot react fully with the metal substrate in time to form an effective protective film, resulting in insufficient initial protection against the metal.

[0004] Secondly, from a compatibility perspective, it is difficult for the crystals of zinc phosphate pigment to form strong coordination bonds with water-based epoxy coatings. This makes it difficult for zinc phosphate inorganic pigment and water-based epoxy resin to form a good interfacial bond. The significant difference in their chemical structures makes it easy for pigment particles to agglomerate or be unevenly distributed within the coating during the film-forming process. This unevenness not only affects the appearance quality of the coating, but more importantly, it creates weak areas within the coating, such as numerous pinholes and pores, which greatly reduces the overall protective performance of the coating.

[0005] Furthermore, considering the inherent characteristics of the pigment itself, zinc phosphate inorganic pigments have an irregular crystal structure and a wide particle size distribution, making precise control difficult. This means that in coating applications, it is impossible to guarantee the ideal rust-preventive effect with each addition. Larger particles may not be able to fill the coating's microstructure smoothly, affecting the coating's density.

[0006] In view of these issues, how to effectively improve the solubility and hydrolysis ability of zinc phosphate pigments in aqueous solutions, 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 novel waterborne epoxy coatings. Summary of the Invention

[0007] The purpose of this invention is to provide a zinc ammonium phosphate pigment for waterborne epoxy coatings and its synthesis method, aiming to solve the problems of large particle size, low solubility, weak hydrolysis ability, and poor compatibility between inorganic pigments and organic resins during curing of zinc phosphate pigments prepared by existing methods, thereby improving the corrosion protection ability of the new generation of zinc phosphate-based inorganic pigments in waterborne epoxy coatings.

[0008] To achieve the above objectives, this technical solution provides a method for synthesizing zinc ammonium phosphate pigment for waterborne epoxy coatings, comprising the following steps:

[0009] Prepare zinc ion solution: Mix deionized water, soluble zinc salt and cationic surfactant to obtain zinc ion solution, and the pH value of zinc ion solution is 1~5;

[0010] Prepare an ammonium ion solution: Mix deionized water, soluble ammonium salt, and ammonia water to obtain an ammonium ion solution with a pH value of 1-5.

[0011] Prepare phosphate ion solution: Mix deionized water, phosphoric acid, soluble phosphate and organic solvent to obtain phosphate solution, and the pH value of phosphate ion solution is 7~10;

[0012] Preparation of zinc ammonium phosphate solution: Mix ammonium ion solution with zinc ion solution to obtain mixed solution, atomize phosphate ion solution into mixed solution to obtain zinc ammonium phosphate solution, and place zinc ammonium phosphate solution in ultrasonic agitation and microwave heating auxiliary device for ultrasonic refinement, heating and heat preservation;

[0013] Precipitated zinc ammonium phosphate pigment: The precipitate in the zinc ammonium phosphate solution is filtered and dried to obtain zinc ammonium phosphate pigment.

[0014] The method for synthesizing zinc ammonium phosphate pigment for waterborne epoxy coatings provided in this solution produces zinc ammonium phosphate pigment with stable three-dimensional structure, high solubility in aqueous solution, strong hydrolysis ability, and the ability to improve interfacial compatibility by forming hydrogen bonds between ammonium ions and organic resins. At the same time, the large number 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 waterborne epoxy coatings.

[0015] In the “Preparation of 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 1-5, so as to effectively inhibit the hydrolysis of zinc ions to form zinc hydroxide precipitate.

[0016] Specifically, zinc ions exist in a hydrolysis equilibrium in zinc ion solutions. When the pH of the zinc ion solution increases, zinc ions readily combine with hydroxide ions to undergo a hydrolysis reaction, forming zinc hydroxide precipitate. In the zinc ammonium phosphate pigment synthesis scheme involved in this method, to ensure a sufficient and stable zinc ion concentration in the zinc ion solution to participate in subsequent reactions with ammonium ions, phosphate ions, etc., the pH of the zinc ion solution is controlled to a relatively acidic environment of 1-5. In this way, zinc ions can exist in a relatively stable ionic state in the solution, ensuring that the reaction can proceed according to the expected stoichiometric ratio when mixed with other ions in the subsequent reaction. This avoids problems such as inaccurate composition or decreased yield of the synthesized zinc ammonium phosphate pigment due to a decrease in zinc ion concentration caused by hydrolysis. Moreover, within this pH range, the activity of zinc ions is in a relatively suitable state, neither too active due to excessive acidity leading to uncontrollable reactions, nor causing unnecessary hydrolysis or other side reactions due to proximity to neutral or alkaline conditions.

[0017] 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.

[0018] In the “Preparation of Zinc Ion Solution”, the soluble zinc salt is selected from one or both of inorganic soluble zinc salts and organic soluble zinc salts.

[0019] Furthermore, when an inorganic soluble zinc salt is chosen as the soluble zinc salt, a zinc ion solution is obtained by mixing the soluble zinc salt, a complexing agent, and a surfactant. The complexing agent is a weak acid and does not contain sodium ions. This has the advantage of maintaining the zinc ion concentration (Zn) in the solution. 2+ and ammonium ions NH4 + It exists stably and effectively inhibits the agglomeration phenomenon during the growth of nano-zinc ammonium phosphate crystals, thus making it easier to prepare micro-nano-scale zinc ammonium phosphate pigments with three-dimensional structures.

[0020] Specifically, weakly acidic complexing agents can form specific complex structures with zinc and ammonium ions, acting like "stabilizers" to ensure their stable existence in solution and guarantee a sufficient and stable ion supply for subsequent reactions. Simultaneously, during the growth of nano-sized zinc ammonium phosphate crystals, the complexing agent can alter the ion distribution and crystal surface properties, reducing the possibility of aggregation between crystal nuclei due to uneven local ion concentrations. It can also form a "protective film" on the crystal surface, effectively inhibiting agglomeration and facilitating the preparation of three-dimensional micro / nano-scale zinc ammonium phosphate pigments.

[0021] When organic soluble zinc salts are chosen, the zinc ion solution contains no complexing agent or only a small amount of complexing agent. This is because organic soluble zinc salts themselves contain various organic groups, which interact specifically with zinc ions in solution. This allows the state and reactivity of zinc ions to be regulated to a certain extent, eliminating the need to add large amounts of complexing agents to maintain the stability of the relevant ions and inhibit crystal aggregation, as is required when using inorganic soluble zinc salts.

[0022] In addition, inorganic soluble zinc salts include one or a combination of zinc chloride, zinc sulfate, zinc nitrate, zinc bromide, zinc perchlorate, or several in compatible conditions. Organic soluble zinc salts include one or a combination of zinc acetate, zinc gluconate, zinc lactate, zinc propionate, zinc citrate, zinc formate dihydrate, zinc hexafluorosilicate, zinc salicylate, or several in compatible conditions.

[0023] 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.

[0024] In the "preparation of zinc ion solution" step, the cationic surfactant is selected from one or more of the following: dodecylquinoline bromide, fatty amine salts, hexadecyltrimethylammonium chloride, and polyquaternary ammonium salts. It should be noted that since the zinc ion solution is acidic, this scheme selects a cationic surfactant that can be stably present in acidic solutions. Furthermore, the addition of this cationic surfactant can effectively inhibit the growth of zinc ammonium phosphate crystals, thereby forming smaller zinc ammonium phosphate nanocrystals, and simultaneously effectively inhibiting the aggregation of nanocrystals.

[0025] Specifically, cationic surfactants can effectively inhibit crystal growth through multiple mechanisms. On one hand, they adsorb onto the surface of the forming zinc ammonium phosphate crystal nuclei, occupying part of the nucleus surface space. This hinders the subsequent deposition and growth of zinc ions, ammonium ions, and phosphate ions towards the nucleus, thus limiting the crystal growth rate. On the other hand, the presence of cationic surfactants in the solution alters the diffusion rate and distribution of ions, causing changes in the concentration gradient of ions near the nucleus, further slowing down the crystal growth process. Through these effects, the goal of forming smaller zinc ammonium phosphate nanocrystals has been successfully achieved. This smaller crystal size has many advantages, such as increasing the specific surface area of ​​the pigment, allowing it to interact more fully with other components in waterborne epoxy coatings, improving pigment dispersibility and reactivity, and thus enhancing the coating's anti-rust and anti-corrosion properties.

[0026] Besides inhibiting crystal growth, cationic surfactants can reduce the surface energy of crystal nuclei and weaken the attraction between nanocrystals through adsorption on the crystal nucleus surface. Simultaneously, their presence in the solution alters the electrostatic field distribution, generating electrostatic repulsion between the nanocrystals. This mechanism of increasing and decreasing electrostatic forces allows the nanocrystals to maintain a relatively independent state in the solution, effectively inhibiting nanocrystal aggregation. This ensures that the prepared zinc ammonium phosphate nanocrystals possess good uniformity and dispersibility, which is more conducive to improving their performance in applications such as waterborne epoxy coatings.

[0027] In the "Preparation of Zinc Ion Solution" step, the zinc ion solution is placed in an auxiliary device equipped with ultrasonic vibration and microwave heating functions, and the temperature of the zinc ion solution is controlled between 25°C and 50°C. This scheme uses ultrasonic vibration and microwave heating technology. Ultrasonic vibration breaks up any potential agglomeration between solute particles, allowing soluble zinc salts, complexing agents, surfactants, and other solutes to be more evenly dispersed in the solution. Microwave heating controls the temperature to 25°C to 50°C, effectively preventing excessive hydrolysis of zinc ions. If the temperature is too high, exceeding 50°C, the possibility of zinc ion hydrolysis forming zinc hydroxide precipitate will greatly increase. This will not only lead to a decrease in the zinc ion concentration in the solution, affecting subsequent reactions with ammonium ions, phosphate ions, etc., but may also introduce zinc hydroxide precipitate during the growth of zinc ammonium phosphate crystals, destroying the regularity and purity of the crystals. Within the temperature range of 25°C to 50°C, the hydrolysis reaction can be effectively controlled, ensuring that zinc ions exist in a stable ionic state in the solution, providing a sufficient and pure source of zinc ions for the synthesis of zinc ammonium phosphate pigments.

[0028] In some embodiments, the ultrasonic oscillation frequency is 20 kHz to 130 kHz; the microwave radiation heater power is 100 W to 2000 W.

[0029] 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. The amount of the first pH adjuster is sufficient to adjust the pH to the specified range. This method promotes the dissolution of zinc salt and Zn. 2+ The ions exist stably in solution, reducing Zn. 2+ Ion concentration is used to prevent the aggregation of zinc phosphate crystals after formation. Specifically, in each liter of deionized water, the soluble zinc salt is 5g~30g, the cationic surfactant is 1g~10g or 5mL~20mL, the complexing agent is 1g~10g, and the primary pH adjuster is 1g~10g or 1mL~20mL.

[0030] In the "preparing ammonium ion solution" step, a second pH adjuster is added to the ammonium ion solution to make its pH value 1-5. This ensures the proper balance of ammonium ions (NH4+). + Stable existence. This scheme controls the pH value of the ammonium ion solution within the acidic range of 1-5 by adding a second pH adjuster, which effectively inhibits the hydrolysis reaction of ammonium ions. This allows ammonium ions to exist in a relatively stable ionic state in the solution, ensuring that sufficient and stable ammonium ions participate in the synthesis of zinc ammonium phosphate pigment during subsequent mixed reactions with zinc ion solutions, avoiding problems such as the reaction not proceeding as expected or the product yield decreasing due to the large-scale hydrolysis and escape of ammonium ions.

[0031] In some embodiments, the second pH adjuster is one or more of hydrochloric acid, sulfuric acid, and nitric acid.

[0032] In the "preparation of ammonium ion solution" step, the soluble ammonium salts include soluble inorganic ammonium salts and soluble organic ammonium salts. The soluble inorganic ammonium salts are one of ammonium carbonate, ammonium bicarbonate, ammonium nitrate, ammonium sulfate, ammonium chloride, and ammonium fluoride, or a combination of several under compatible conditions. The soluble organic ammonium salts are one of ammonium tartrate, ammonium oxalate, ammonium formate, and ammonium citrate, or a combination of several under compatible conditions. Soluble inorganic ammonium salts generally have good solubility and a fast dissociation rate, enabling them to rapidly provide a large amount of ammonium ions in the initial stage of solution preparation. While the dissociation rate of soluble organic ammonium salts may be relatively slower, they can continuously and stably release ammonium ions in the solution, thus ensuring the supply of ammonium ions throughout the reaction process. Furthermore, the simultaneous use of soluble inorganic and soluble organic ammonium salts can influence the crystal growth process from different angles, resulting in more uniform and regular crystal growth, reducing crystal defects, and improving the crystal quality of zinc ammonium phosphate pigment.

[0033] In the preparation of ammonium ion solution, the mass ratio of soluble inorganic ammonium salt or soluble organic ammonium salt to ammonia water is set between 1:1 and 5:1. This primarily serves to provide ammonium ions. Specifically, in each liter of deionized water, the dosage is 10g-60g of soluble inorganic ammonium salt, 10g-60g of soluble organic ammonium salt, 10mL-100mL of ammonia water, and 1g-10g or 1mL-20mL of a second pH adjuster.

[0034] In the "preparing phosphate ion solution" step, a third pH adjuster is added to the phosphate ion solution to achieve a pH of 7-14. This effectively promotes the subsequent phosphate ion (PO4) ion exchange. 3- ammonium ions NH4 + and zinc ions Zn 2+The reaction rate between them is reduced, and a large amount of heat is released during the acid-base neutralization reaction, which increases the number of nucleation sites for zinc ammonium phosphate crystals and inhibits the growth of crystal nuclei, thereby forming nanoscale zinc ammonium phosphate crystals.

[0035] 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.

[0036] 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 stably provides phosphate ions (PO4). 3- This ensures a continuous and stable source of phosphate ions for subsequent reactions with ammonium and zinc ions. Metaphosphoric acid can polymerize in solution, forming metaphosphoric acid molecular chains with varying degrees of polymerization. These chains can then decompose and release phosphate ions, enriching the supply of phosphate ions. The combination of these two ensures both a continuous and stable source of phosphate ions and allows for flexible adjustment of phosphate ion concentration through the unique properties of metaphosphoric acid, facilitating the formation of high-quality zinc ammonium phosphate crystals.

[0037] In the step of “preparing 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 under compatible conditions.

[0038] In the step of "preparing the phosphate ion solution", the organic solvent is one or more of ethanol, polyethylene glycol, glycerol, and ethyl acetate. The addition of the organic solvent dilutes the phosphate ions (PO4) in the phosphate ion solution. 3- Concentration, slowing down the reduction of phosphate ion (PO4) concentration. 3- ammonium ions NH4 + and zinc ions Zn 2+ The reaction rate between them is improved, which is conducive to the growth of zinc ammonium phosphate crystals along the (101), (011) and (200) crystal planes, resulting in a three-dimensional structure of zinc ammonium phosphate pigment formed by plate-like stacking.

[0039] In the step of "preparing the phosphate ion solution", the phosphate ions are placed in a magnetically stirred water bath, and the concentration of the phosphate ion solution is controlled between 25°C and 50°C. Within this temperature range, the degree of ionization of phosphate ions is relatively moderate. It avoids the situation where ionization is too slow due to excessively low temperature, resulting in insufficient concentration of phosphate ions available for subsequent reactions; nor does it cause drastic changes in the pH and other properties of the solution due to excessively high temperature, affecting the existing forms and reactivity of other ions. Furthermore, the activity of ammonium and zinc ions is also at an appropriate level, allowing for smoother interactions with phosphate ions.

[0040] In some embodiments, the stirring speed of the magnetically stirred water bath is 50 r·min. -1 Up to 1000 r·min -1 The heating power ranges from 100W to 2000W.

[0041] 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. The third pH adjuster is added to adjust the pH to the specified range. This increases the phosphate concentration in the solution, promoting the reaction of phosphate with Zn. 2+ and NH4 + The reaction rate between ions is increased; the pH value of the phosphate-containing solution is increased to maintain alkalinity, promoting the generation of heat during the reaction and providing energy for the nucleation of zinc ammonium phosphate crystals. 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 adjuster is 1g~20g or 1mL~20mL.

[0042] In the "preparation of zinc ammonium phosphate solution" step, the zinc ammonium phosphate solution is subjected to ultrasonic refining, heating, and heat preservation in an ultrasonic vibration and microwave heating auxiliary device. The temperature of the zinc phosphate solution is controlled at 25℃~50℃, and the heat preservation time is 0.1h~24h. This method 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 zinc ammonium phosphate.

[0043] In the step of "preparing 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 zinc ammonium phosphate solution.

[0044] In the "precipitation of zinc ammonium phosphate pigment" step, the precipitate in the zinc ammonium phosphate solution is filtered and the precipitate is placed in a drying oven to dry, wherein the temperature of the drying oven is 50℃~200℃.

[0045] In addition, this solution provides a zinc ammonium phosphate pigment for waterborne epoxy coatings, synthesized according to the aforementioned method for synthesizing zinc ammonium phosphate pigment for waterborne epoxy coatings. It has a three-dimensional spatial structure and a specific surface area of ​​50 m². 2 ·g -1 ~ 220 m 2 ·g -1 The dimensions are 0.1μm to 5.0μm in length and width, and 10 nm to 200nm in thickness. The specific surface area of ​​common micron-sized zinc phosphate on the market is relatively small, generally between 1.5-10 m² / g, while the specific surface area of ​​two-dimensional sheet-like micro-nano-sized zinc phosphate on the market is between 8.7-39 m² / g.

[0046] Compared with existing technologies, this technical solution has the following characteristics and beneficial effects:

[0047] This method for synthesizing zinc ammonium phosphate pigment for waterborne epoxy coatings optimizes crystal growth, refines grain size, and increases specific surface area through precise control of reaction conditions. The scheme precisely adjusts the pH value in each ionic solution preparation and selects appropriate reagents to inhibit the growth of zinc ammonium phosphate crystals, forming fine nanocrystals, increasing specific surface area, and improving dispersibility and reactivity in waterborne epoxy coatings. The prepared zinc ammonium phosphate pigment has high solubility and strong hydrolysis ability in aqueous solution. The phosphate ions generated by hydrolysis can form a complete passivation film on the substrate metal surface, effectively blocking corrosive ions and significantly improving the corrosion protection effect of organic coatings. Simultaneously, it can improve interfacial compatibility by forming hydrogen bonds with organic resins through ammonium ions, ensuring uniform dispersion and tight bonding in waterborne epoxy coatings, avoiding compatibility issues, and guaranteeing coating performance. When the zinc ammonium phosphate pigment of this scheme is applied to waterborne epoxy coatings, it can significantly improve their corrosion protection effect, resist external erosion, extend the service life of metal products, and has a good physical barrier effect against corrosive ions. Attached Figure Description

[0048] Figure 1 This is a scanning electron microscope image of a micro / nano-scale three-dimensional flower-like zinc ammonium phosphate pigment according to Embodiment 1 of the present invention.

[0049] Figure 2 This is the XRD spectrum of the micro-nano-scale three-dimensional flower-like structure zinc ammonium phosphate pigment according to Embodiment 1 of the present invention.

[0050] Figure 3 This is a scanning electron microscope image of the micro-nano-scale three-dimensional spherical zinc ammonium phosphate pigment of Embodiment 2 of the present invention. Detailed Implementation

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0052] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0053] Example 1

[0054] Prepare zinc ion solution: Take a clean beaker with a capacity of 10L, add 1L of deionized water to the beaker, and then add 10g of zinc chloride, 10mL of polyethylene glycol, and 2g of sodium acetate in sequence. Adjust the pH of the solution to 2 with acetic acid. This solution is called zinc ion solution. Use an ultrasonic vibration and microwave heating auxiliary device to ultrasonically refine the zinc ion solution, heat it and maintain the temperature at 50℃.

[0055] To prepare an ammonium ion solution: Take a clean beaker with a capacity of 10L, add 1L of deionized water to the beaker, then add 20g of ammonium carbonate, 30mL of ammonia water, and adjust the pH of the solution to 2 with dilute hydrochloric acid. This solution is called an ammonium ion solution.

[0056] To prepare a phosphate ion solution: Take a clean 10L beaker and add 1L of deionized water. Then, add 5mL of phosphoric acid, 20g of ammonium dihydrogen phosphate, 20mL of ethanol, and sodium hydroxide to adjust the pH to 11. This solution is denoted as the phosphate ion solution. Heat the phosphate ion solution in a magnetically stirred water bath at 50℃, maintaining the temperature at a stirring speed of 500 r·min. -1 ;

[0057] Preparation of zinc ammonium phosphate solution: The ammonium ion solution is introduced into the zinc ion solution to form a mixed solution. The phosphate ion solution is atomized and sprayed into the mixed solution using an air compressor spray device to form zinc ammonium phosphate solution. The zinc ammonium phosphate solution is further ultrasonically refined and heated using an ultrasonic vibration and microwave heating auxiliary device, and the temperature is maintained at 50°C.

[0058] Obtaining zinc ammonium phosphate: Use a vacuum filtration device to filter the precipitate in the zinc ammonium phosphate solution, and place the precipitate in a drying oven to dry it. The temperature of the drying oven is set to 100℃.

[0059] Example 1 of this invention utilizes a method assisted by ultrasonic oscillation and microwave heating to synthesize zinc ammonium phosphate pigment with a micro / nano-scale three-dimensional flower-like structure, such as... Figure 1 As shown, Figure 1 This is a scanning electron microscope image of the micro / nano-scale three-dimensional flower-like structure of zinc ammonium phosphate pigment. Figure 2 The image shows the XRD pattern of this micro-nano-scale three-dimensional flower-like zinc ammonium phosphate pigment. It can be seen that the grain size of this flower-like zinc ammonium phosphate pigment has been further refined, and it has a stable three-dimensional spatial structure. In addition, it has high solubility and strong hydrolysis ability in aqueous solution. On the one hand, it can improve the interfacial compatibility by forming hydrogen bonds between ammonium ions and organic resins. On the other hand, the large number of phosphate ions generated by hydrolysis can form a complete passivation film on the substrate metal surface, thereby significantly improving the corrosion protection effect of organic coatings.

[0060] Example 2

[0061] To prepare a zinc ion solution, take a clean 10L beaker and add 1L of deionized water. Then add 10g of zinc citrate, 5g of sodium dodecylbenzenesulfonate, and 3g of sodium citrate in sequence. Adjust the pH of the solution to 3 with citric acid. This solution is then labeled as the zinc ion solution. The zinc ion solution is ultrasonically refined and heated using an ultrasonic vibration and microwave heating auxiliary device, and the temperature is maintained at 30℃.

[0062] To prepare an ammonium ion solution, take a clean beaker with a capacity of 10L, add 1L of deionized water to the beaker, then add 20g of ammonium citrate, 50mL of ammonia water, and adjust the pH of the solution to 3 with dilute hydrochloric acid. This solution is called the ammonium ion solution.

[0063] To prepare a phosphate ion solution, take a clean 10L beaker and add 1L of deionized water. Then, add 5mL of phosphoric acid, 20g of ammonium dihydrogen phosphate, 10mL of ethyl acetate, and adjust the pH of the solution to 8 with sodium hydroxide. This solution is denoted as the phosphate ion solution. Heat the phosphate ion solution in a magnetically stirred water bath at 30℃, maintaining the temperature at a stirring speed of 500 r·min. -1 .

[0064] Prepare a zinc ammonium phosphate solution and wait for the solid to completely dissolve. Then, introduce the ammonium ion solution into the 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 a zinc ammonium phosphate solution. Continue to use an ultrasonic vibration and microwave heating auxiliary device to ultrasonically refine the zinc ammonium phosphate solution, heat it and maintain the temperature at 30°C.

[0065] Obtain zinc ammonium phosphate, filter the precipitate from the zinc ammonium phosphate solution using a vacuum filtration device, and place the precipitate in a drying oven to dry at a temperature of 100℃.

[0066] Example 2 of this invention utilizes an ultrasonic oscillation and microwave heating-assisted method to synthesize zinc ammonium phosphate pigment with a micro / nano-scale three-dimensional spherical structure. A scanning electron microscope image of the spherical zinc ammonium phosphate pigment crystals is shown below. Figure 3 As shown, the spherical zinc ammonium phosphate pigment has a further refined grain size and a stable three-dimensional spatial structure. It also has high solubility and strong hydrolysis ability in aqueous solution. On the one hand, it can improve the interfacial compatibility by forming hydrogen bonds between ammonium ions and organic resins. On the other hand, the large number of phosphate ions generated by hydrolysis can form a complete passivation film on the surface of the base metal, thereby significantly improving the corrosion protection effect of organic coatings.

[0067] This invention is not limited to the preferred embodiments described above. Anyone can derive other products in various forms under the guidance of this invention. However, regardless of any changes in shape or structure, any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A method for synthesizing zinc ammonium phosphate pigment for waterborne epoxy coatings, characterized in that, Includes the following steps: Preparation of zinc ion solution: A zinc ion solution is obtained by mixing deionized water, soluble zinc salt, and cationic surfactant. The pH value of the zinc ion solution is 1-5. The soluble zinc salt is selected from one or two of inorganic soluble zinc salt and organic soluble zinc salt. When inorganic soluble zinc salt is selected, the zinc ion solution is obtained by mixing soluble zinc salt, complexing agent, and surfactant. The complexing agent is a weak acid and does not contain sodium ions. Prepare an ammonium ion solution: Mix deionized water, soluble ammonium salt, and ammonia water to obtain an ammonium ion solution with a pH value of 1-5. Prepare phosphate ion solution: Mix deionized water, phosphoric acid, soluble phosphate and organic solvent to obtain phosphate solution, and the pH value of phosphate ion solution is 7~10; Preparation of zinc ammonium phosphate solution: Mix ammonium ion solution with zinc ion solution to obtain mixed solution, atomize phosphate ion solution into mixed solution to obtain zinc ammonium phosphate solution, and place zinc ammonium phosphate solution in ultrasonic agitation and microwave heating auxiliary device for ultrasonic refinement, heating and heat preservation; Precipitated zinc ammonium phosphate pigment: The precipitate in the zinc ammonium phosphate solution is filtered and dried to obtain zinc ammonium phosphate pigment, which has a three-dimensional spatial structure.

2. The method for synthesizing zinc ammonium phosphate pigment for waterborne epoxy coatings according to claim 1, characterized in that, Add a first pH adjuster to the zinc ion solution, the first pH adjuster being one or more of nitric acid, sulfuric acid, hydrochloric acid, acetic acid, citric acid, tartaric acid, malic acid, succinic acid, and lactic acid; add a second pH adjuster to the ammonium ion solution, the second pH adjuster being one or more of hydrochloric acid, sulfuric acid, and nitric acid; add a third pH adjuster to the phosphate ion solution, the third pH adjuster being 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 coatings according to claim 1, characterized in that, The cationic surfactant is selected from one or more of the following: dodecylquinoline bromide, fatty amine salt, hexadecyltrimethylammonium chloride, and polyquaternary ammonium salt.

4. The method for synthesizing zinc ammonium phosphate pigment for waterborne epoxy coatings according to claim 1, characterized in that, The zinc ion solution was placed in an auxiliary device equipped with ultrasonic vibration and microwave heating functions, and the temperature of the zinc ion solution was controlled at 25°C to 50°C; the phosphate ion solution was placed in a water bath with magnetic stirring, and the temperature of the phosphate ion solution was controlled at 25°C to 50°C.

5. The method for synthesizing zinc ammonium phosphate pigment for waterborne epoxy coatings according to claim 1, characterized in that, 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 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 under compatible conditions.

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

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

8. The method for synthesizing zinc ammonium phosphate pigment for waterborne epoxy coatings according to claim 1, characterized in that, In the "preparation of zinc ion solution", the mass ratio of soluble zinc salt, cationic surfactant and complexing agent 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.

9. A zinc ammonium phosphate pigment for use in waterborne epoxy coatings, characterized in that, The zinc ammonium phosphate pigment for waterborne epoxy coatings is synthesized according to any one of claims 1 to 8 and has a three-dimensional spatial structure.

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