Composite calcium source zinc calcium phosphate refractory material, preparation method and application

Abstract

The invention relates to the technical field of inorganic non-metallic materials, discloses a composite calcium source calcium zinc phosphate refractory material, a preparation method and application, and aims to solve the technical problems that the reaction is out of control, the water-soluble substance residue is high and the performance is difficult to consider in the preparation of the traditional calcium zinc phosphate material. Calcium hydroxide and calcium carbonate are adopted to form a composite calcium source, and a dynamic time-sharing feeding process is matched and comprises the following steps: firstly, stirring a phosphoric acid aqueous solution and a zinc oxide-calcium hydroxide mixture at 20-35 DEG C for 20-40 minutes to form initial slurry, then adding calcium carbonate accounting for 0-30% of the total calcium mole number at an initial thickening point of the slurry, continuing to stir for 20-40 minutes, and finally, adding calcium carbonate accounting for 0-30% of the total calcium mole number at the initial thickening point of the slurry; and carrying out suction filtration, and drying at 100-110 DEG C for 1.5-2.5 hours to obtain a finished According to the method, the operable time is prolonged by more than 200%, the content of water-soluble substances is reduced by more than 50%, high early strength and structural compactness are both considered, and the method is suitable for the fields of high-end anticorrosive coatings and the like and has remarkable process and performance advantages.

Description

Technical Field

[0001] This invention relates to the field of inorganic non-metallic materials technology, specifically to the preparation technology of zinc-calcium phosphate-based refractory materials. More particularly, it relates to a method for preparing low-water-soluble, high-density composite calcium-source zinc-calcium phosphate refractory materials using calcium hydroxide and calcium carbonate as a composite calcium source through a dynamic time-sharing feeding process, and the refractory materials obtained by this method. The products of this invention can be widely used in high-performance applications such as long-lasting anti-corrosion coatings, water-resistant adhesives, and electronic packaging materials. Background Technology

[0002] Zinc phosphate-calcium based inorganic refractories, with their green and environmentally friendly properties and dual functions of fire resistance and corrosion resistance, have become a core development direction to replace traditional organic fire-retardant coatings, showing broad application prospects in many fields such as construction, rail transportation, and electronics. However, the industrialization process of this type of material has always been limited by the key bottleneck of water-soluble substance residue and leaching, which seriously restricts its promotion and application in harsh environments such as outdoor and high-humidity environments, becoming a core technical obstacle to unleashing its application potential.

[0003] The aforementioned water-soluble substances mainly originate from incompletely reacted phosphoric acid raw materials, soluble phosphate byproducts, and free ions during the preparation process. Their negative impact on material performance manifests in two core dimensions: Firstly, under normal usage conditions, water-soluble substances are easily leached out with ambient moisture, leading to a sharp decline in the coating's water resistance and causing defects such as blistering, softening, and surface efflorescence, severely damaging the coating's appearance integrity and substrate adhesion. Secondly, in high-temperature fire scenarios, the rapid loss of water-soluble substances directly degrades the density and structural integrity of the fireproof charcoal layer, resulting in a significant reduction in thermal insulation performance and creating serious safety hazards. Therefore, effectively reducing the water-soluble content in zinc-calcium phosphate materials is a key requirement for achieving high-performance applications.

[0004] From the perspective of raw material systems and preparation processes, existing room-temperature synthesis technologies have fundamental flaws: they commonly use highly reactive calcium hydroxide (Ca(OH)2) as the sole calcium source, and often employ a "one-step" mixing process (mixing all solid raw materials with phosphoric acid solution at once). The acid-base neutralization reaction between calcium hydroxide and phosphoric acid is characterized by its rapid rate and high exothermic reaction. Combined with an unreasonable mixing process, this directly triggers a series of chain reactions:

[0005] Firstly, uncontrolled reaction kinetics leads to poor process adaptability. The highly active calcium hydroxide reacts violently with phosphoric acid in a single application, releasing a large amount of heat instantly, causing a sudden rise in system temperature and rapid evaporation of water. This results in a sharp increase in slurry viscosity within minutes, making the workable time (work window) too short to meet the requirements of complex construction processes such as spraying, scraping, and precision molding.

[0006] Secondly, defects in the reaction process induce material structural deterioration. Violent reactions and rapid curing make it difficult for the gas trapped in the slurry to escape, easily forming bubble defects. At the same time, the thermal stress generated by rapid shrinkage can cause microcracks in the green body, directly damaging the material's density and mechanical strength.

[0007] Third, incomplete reaction exacerbates the problem of water-soluble residues. The violent and short-lived reaction process physically blocks the diffusion of reactant molecules and further reactions. A large amount of unreacted phosphoric acid and acid phosphate precursors are "frozen" in the solidified network, directly resulting in a high content of water-soluble substances, which cannot meet the performance requirements of high-end anti-corrosion and other scenarios.

[0008] To address these issues, the industry has proposed various technical solutions, but all have significant limitations and have failed to fundamentally overcome the bottlenecks.

[0009] 1. Multi-component compound retarding scheme: such as the high-performance formula of magnesium phosphate cement disclosed in patent CN119859028A, which solves the contradiction between rapid setting and high strength through "cocktail" multi-component compounding. However, this scheme has defects such as high raw material cost, strict process control requirements, narrow formula window, and insufficient verification of long-term durability, making it difficult to achieve large-scale engineering application.

[0010] 2. Admixture control scheme: such as the retarded magnesium phosphate cement technology disclosed in patent CN118221367A, which improves setting characteristics by adding admixtures, but does not solve the root cause of violent reaction from the essence of the raw material system. At the same time, it introduces new technical problems such as high raw material sensitivity and increased cost, and does not involve the synergistic control design of composite calcium source.

[0011] 3. Single calcium source alternative: Some technologies attempt to completely replace calcium hydroxide with calcium carbonate to slow down the reaction rate, but this approach will cause new problems, including slow reaction start-up, almost zero early strength, and the continuous generation of CO2 gas by the reaction of calcium carbonate and phosphoric acid, resulting in loose and porous interior of the green body, and a significant deterioration in structural density and mechanical properties.

[0012] In summary, existing technologies either rely on external regulation through the physical addition of additives or employ simple substitution of a single calcium source. Neither approach addresses the fundamental design of the raw material system or the synergistic optimization of the process, failing to leverage the differences in reaction kinetics among different calcium sources to achieve endogenous regulation of the synthesis process. In the field of room-temperature synthesis of zinc-calcium phosphate materials, existing technologies have fallen into a systemic contradiction resembling a "trilemma"—a difficulty in simultaneously achieving "reaction controllability," "reaction completeness," and "comprehensive material performance." An innovative technological solution is urgently needed to fundamentally optimize both the raw material system and the preparation process, systematically resolving these core contradictions and breaking through the current technological bottlenecks. Summary of the Invention

[0013] This invention provides a composite calcium-source zinc-calcium phosphate refractory material, its preparation method, and its application. The aim is to overcome the limitations of the traditional "one-step" process and design an innovative synthesis route to systematically solve the three irreconcilable contradictions in the preparation of zinc-calcium phosphate materials: "violent reaction and construction controllability", "rapid curing and complete reaction", and "early strength and low water-soluble content". This results in the preparation of a high-performance zinc-calcium phosphate material with excellent construction performance, high early strength, low internal defects, and extremely low water-soluble content.

[0014] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0015] A method for preparing a composite calcium-sourced zinc phosphate calcium refractory material includes the following steps:

[0016] (1) Preparation of initial reaction slurry: According to the raw material molar ratio, the molar ratio of zinc oxide (ZnO) to calcium hydroxide (Ca(OH)2) is 2:1 to 1:2. Prepare a phosphoric acid aqueous solution with a mass percentage concentration of 30%-40%, and the phosphoric acid accounts for 10%-30% of the total mass of the raw materials; at an initial temperature of 20°C-35°C, mix the phosphoric acid aqueous solution with the first solid component (a mixture of ZnO and Ca(OH)2) and stir at a stirring rate of 200-300 rpm for 20-40 minutes to form the initial reaction slurry. During this stage, the system temperature rises to 70°C-95°C.

[0017] (2) Introducing calcium carbonate midway for reaction regulation: Within 20-30 minutes after the initial mixing begins in step (1), and when the slurry reaches its initial thickening point (viscosity increases significantly but still has good fluidity), calcium carbonate is added to the initial reaction slurry. The amount of calcium carbonate added is based on its Ca content. 2+ Based on the molar number, it accounts for 0%-30% of the total calcium molar number in the first solid component; then, at a reaction temperature of 70°C-95°C, stirring is continued for 20-40 minutes at a stirring rate of 150-300 rpm;

[0018] (3) Filtration and drying: The slurry that has completed the reaction in step (2) is filtered, and the resulting filter cake is dried at a constant temperature of 100°C-110°C for 1.5-2.5 hours to obtain composite calcium source zinc phosphate calcium refractory material.

[0019] Preferably, the molar ratio of zinc oxide to calcium hydroxide in step (1) is 1:1.

[0020] Preferably, the mass percentage concentration of the phosphoric acid aqueous solution in step (1) is 35%.

[0021] Preferably, the phosphoric acid in step (1) accounts for 20% of the total mass of the raw materials.

[0022] Preferably, the amount of calcium carbonate added in step (2) is based on its Ca content. 2+ Based on the molar number, it accounts for 6% of the total calcium molar number in the first solid component.

[0023] The present invention also provides a composite calcium source zinc calcium phosphate refractory material, wherein the main crystalline phase of the refractory material is zinc calcium phosphate dihydrate (CaZn2(PO4)2·2H2O), the water-soluble content is ≤0.91wt%, the pH value of the 10% aqueous suspension is 6.5-7.0, and the ignition vector at 600℃ is ≤11.2%.

[0024] Furthermore, the Zn in the refractory material 2+ The content is 29.5%-34.5%, PO4 3- The content is 47.5%-48.7%, Ca 2 + The content is 10.3%-11.5%.

[0025] Furthermore, the early strength of the refractory material is ≥15MPa after curing at room temperature for 24 hours, and the 7-day strength is ≥30MPa.

[0026] Furthermore, the refractory material retains ≥90% of its strength after being immersed in water for 7 days.

[0027] Furthermore, the refractory material is applied in the fields of high-end anti-corrosion coatings, water-resistant adhesives, or electronic packaging materials.

[0028] Compared with the prior art, the present invention has the following technical advantages:

[0029] 1. A qualitative leap has been achieved in process performance.

[0030] This invention utilizes a dynamic time-sharing feeding process, with the later addition of calcium carbonate buffering the intense exothermic reaction between calcium hydroxide and phosphoric acid. This extends the workable time of the slurry from several minutes in the traditional process to tens of minutes, an extension of over 200%, providing ample operating window for complex construction processes such as spraying, scraping, and precision molding. At the same time, the gentle reaction process allows sufficient time for air bubbles inside the slurry to escape, eliminating structural defects such as air bubbles and microcracks at the source, and significantly improving the density of the green body.

[0031] 2. A breakthrough reduction in water-soluble content has been achieved.

[0032] The post-reaction stage of calcium carbonate can fully consume the residual phosphoric acid and water-soluble phosphate precursors from the initial reaction, reducing the water-soluble content of the final product by more than 50% compared to the traditional one-step feeding process, down to a minimum of 0.91 wt%. This extremely low water-soluble content completely solves the leaching problem during material use, meeting the stringent requirements for water resistance and long-term stability in high-end anti-corrosion coatings, electronic packaging materials, and other fields, thus breaking through the application barriers of traditional materials.

[0033] 3. Achieve balanced optimization of material mechanical properties

[0034] The composite calcium source system of this invention combines the high early strength (strength ≥15MPa after 24h curing at room temperature) brought by calcium hydroxide with the continuous increase in later strength contributed by calcium carbonate (strength ≥30MPa after 7 days). The strength development curve is more reasonable and can meet the construction requirements of rapid demolding and the structural requirements of long-term service. At the same time, the dense crystal structure endows the material with excellent resistance to degradation. The strength retention rate after 7 days of water immersion is ≥90%, which is far superior to traditional materials.

[0035] 4. Synergistic optimization of production costs and process adaptability

[0036] This invention uses inexpensive calcium carbonate to replace more expensive calcium hydroxide, directly reducing raw material costs. Furthermore, the preparation process does not require complex or special production equipment and can be implemented on existing inorganic non-metallic material production lines by simply adjusting the feeding sequence. The process is highly adaptable, easy to achieve large-scale and stable production, and has significant value for industrial promotion.

[0037] 5. Significantly improved compatibility with the metal matrix

[0038] The material prepared by this invention has a pH value of 6.5-7.0 in a 10% aqueous suspension, which is weakly neutral and does not leach acidic water-soluble substances, thus avoiding the risk of corrosion to the metal substrate. At the same time, the dense material structure can form a continuous protective barrier, which greatly improves the anti-corrosion protection effect on the metal substrate and can be directly applied to high-end metal anti-corrosion fields such as ships and bridges.

[0039] 6. Highly applicable to industrial use

[0040] The present invention discloses a method for preparing composite calcium-source zinc phosphate calcium refractory materials. The raw materials used are conventional industrial-grade raw materials, which are inexpensive and easy to procure. The preparation process does not require special equipment and can be implemented by modifying existing inorganic non-metallic material production lines. The process is highly controllable and stable. The resulting product has low water solubility, high early strength, high density, and excellent metal compatibility. It can be widely used in high-end anti-corrosion coatings, water-resistant adhesives, electronic packaging materials, and other fields, and has significant industrial applicability and market promotion value.

[0041] In summary, this invention, through an ingenious process design, not simply improves upon existing methods, but fundamentally reconstructs the synthesis pathway of zinc calcium phosphate materials. This systematically solves a series of technical problems that have long plagued this field, achieving a synergistic leap forward in processability, functionality (low water solubility), and structure (high strength and high density), opening up new prospects for the application of this type of material in high-tech fields. Attached Figure Description

[0042] Figure 1 Figure for an example sample without calcium carbonate.

[0043] Figure 2 Example diagram of introducing calcium carbonate sample. Detailed Implementation

[0044] To make the technical solution of the present invention easier for those skilled in the art to understand and implement, the preparation method and product performance of the present invention will now be described in detail with reference to specific embodiments. The embodiments of the present invention are only for explaining the present invention and are not intended to limit the scope of protection of the present invention. All simple adjustments made based on the core technical solution of the present invention fall within the scope of protection of the present invention.

[0045] I. Experimental Materials

[0046] The raw materials used in the embodiments and comparative examples of this invention are all industrial-grade conventional raw materials, specifically as follows: zinc oxide (ZnO, purity ≥99%), calcium hydroxide (Ca(OH)2, purity ≥95%), calcium carbonate (CaCO3, purity ≥98%), phosphoric acid (H3PO4, industrial grade, concentration 85%), and deionized water was used in the experiments.

[0047] II. Performance Testing Methods

[0048] 1. Phase analysis: The phases of the product were characterized by X-ray diffraction (XRD), and the main crystalline phase was confirmed by comparison with the standard PDF card (CaZn2(PO4)2·2H2O, PDF#86-2372);

[0049] 2. Water-soluble content test: Refer to GB / T 5211.1-2003 "Determination of Water-soluble Matter in Pigments - Cold Extraction Method"

[0050] At room temperature, a sample is soaked in a certain amount of water, and water-soluble substances are extracted by stirring and filtration. The filtrate is evaporated and dried, and the mass of the residue is weighed to calculate the mass fraction of water-soluble substances.

[0051] 3. pH test: The pH value of the 10% aqueous suspension was measured using a pH meter;

[0052] 4. Burning vector test: The sample is burned to constant weight at 600℃. Based on the mass difference before and after burning, the percentage of mass lost relative to the original sample mass is calculated.

[0053] 5. Mechanical property testing: The slurry was prepared into 40mm×40mm×160mm specimens, and the compressive strength after curing at room temperature for 24 hours and 7 days was tested using a pressure testing machine;

[0054] 6. Water resistance test: The sample cured for 7 days was immersed in deionized water for 7 days, and the strength retention rate after immersion was tested.

[0055] III. Comparative Example (Traditional One-Step Process)

[0056] The comparative example uses a traditional one-step feeding process (without calcium carbonate addition), as follows: The raw materials with a molar ratio of ZnO 60%, H3PO4 10%, and Ca(OH)2 30% are mixed together, and an acid-base reaction occurs at a stirring speed of 300 rpm and a stirring temperature of 70°C; the slurry after the reaction is completed is filtered to obtain a filter cake; the obtained filter cake is placed in a constant temperature drying oven at 110°C and dried for 2.5 hours to obtain zinc calcium phosphate material.

[0057] The performance parameters of the comparative product are: Zn 2+ Content 36.1%, PO4 3- Content 31.9%, Ca 2+ Content 10.23%, pH value of 10% aqueous suspension 6.51, water-soluble content 2.1wt%, ignition vector at 600℃ 10.1%, strength after 24h curing at room temperature 10MPa, strength after 7d 22MPa, and strength retention rate after 7d immersion in water 75%.

[0058] IV. Examples

[0059] In an embodiment of the present invention, a method for preparing a composite calcium-sourced zinc phosphate calcium refractory material includes the following steps:

[0060] 1. Preparation of initial reaction slurry

[0061] (1) Determining the raw material ratio: Control the molar ratio of zinc oxide (ZnO) to calcium hydroxide (Ca(OH)2) to be 2:1 to 1:2. This ratio range can ensure the formation of a stable phosphate precursor in the initial stage, while avoiding reaction imbalance caused by excessive amount of a single raw material; Prepare a phosphoric acid aqueous solution with a mass percentage concentration of 30%-40%, with phosphoric acid accounting for 10%-30% of the total mass of raw materials. The phosphoric acid aqueous solution in this concentration range can take into account both reactivity and slurry fluidity, avoiding local over-reaction caused by excessive concentration or incomplete reaction caused by excessively low concentration.

[0062] (2) Mixing reaction process: At an initial temperature of 20°C-35°C, the above-mentioned phosphoric acid aqueous solution is mixed with the first solid component (a mixture of ZnO and Ca(OH)2) and stirred vigorously at a stirring rate of 200-300 rpm for 20-40 minutes to form an initial reaction slurry. During the stirring process, the system temperature will naturally rise to 70°C-95°C. This temperature range provides suitable thermodynamic conditions for the formation of the zinc calcium phosphate precursor and will not cause the slurry to solidify rapidly due to excessive temperature rise.

[0063] 2. Calcium carbonate is introduced midway through the reaction to regulate its progression.

[0064] (1) Timing of addition: Calcium carbonate is added to the initial reaction slurry within 20-30 minutes after the start of initial mixing, when the slurry reaches the initial thickening point (i.e., the critical state where the slurry viscosity increases significantly but still has good fluidity). The timing of this addition is one of the core innovations of this invention. At this time, the initial slurry has formed a preliminary phosphate network, and the addition of calcium carbonate can participate in the subsequent reaction regulation without destroying the initial network.

[0065] (2) Control of calcium carbonate dosage: The amount of calcium carbonate added is determined by its Ca content. 2+ The amount of calcium carbonate used is 0%-30% of the total calcium moles in the first solid component. This range of dosage ensures that calcium carbonate fully consumes the residual phosphoric acid and water-soluble precursors, while avoiding excessive CO2 production caused by excessive calcium carbonate, which leads to a porous green body.

[0066] (3) Subsequent reaction process: After adding calcium carbonate, maintain the system temperature at 70°C-95°C and continue stirring at a stirring rate of 150-300 rpm for 20-40 minutes. The stirring rate in this stage is slightly lower than that in the initial stage, which can ensure that the reaction proceeds fully while avoiding damage to the already formed phosphate network structure and ensuring the uniformity of the slurry.

[0067] 3. Filtration and drying

[0068] The reacted slurry is filtered to remove free water and trace impurities that did not participate in the reaction. The resulting filter cake is then placed in a constant temperature drying oven at 100°C-110°C and dried for 1.5-2.5 hours to obtain the final composite calcium zinc phosphate calcium refractory material. This drying process ensures the stable retention of crystal water in the filter cake while avoiding crystal structure damage caused by high temperatures.

[0069] To make the present invention more fully disclosed, more specific embodiments are described below.

[0070] Examples 1-5 (Optimization of dynamic feeding process without calcium carbonate)

[0071] Example 1

[0072] A method for preparing a composite calcium-source zinc phosphate calcium refractory material includes the following steps:

[0073] 1. Preparation of initial reaction slurry

[0074] (1) Determination of raw material ratio: The molar ratio of zinc oxide (ZnO) to calcium hydroxide (Ca(OH)2) is controlled at 2:1. This ratio range can ensure the formation of a stable phosphate precursor in the initial stage, while avoiding reaction imbalance caused by excessive amount of single raw material; Prepare a phosphoric acid aqueous solution with a mass percentage concentration of 35%, with phosphoric acid accounting for 10% of the total mass of raw materials. The phosphoric acid aqueous solution in this concentration range can take into account both reactivity and slurry fluidity, avoiding local over-reaction caused by excessive concentration or incomplete reaction caused by excessively low concentration.

[0075] (2) Mixing reaction process: At an initial temperature of 28°C, the above-mentioned phosphoric acid aqueous solution is mixed with the first solid component (a mixture of ZnO and Ca(OH)2) and stirred vigorously at a stirring rate of 270 rpm for 30 minutes to form an initial reaction slurry. During the stirring process, the system temperature will naturally rise to 75°C. This temperature range provides suitable thermodynamic conditions for the formation of the zinc calcium phosphate precursor and will not cause the slurry to solidify rapidly due to excessive temperature rise.

[0076] 2. Calcium carbonate is introduced midway through the reaction to regulate its progression.

[0077] (1) Timing of addition: Calcium carbonate is added to the initial reaction slurry within 25 minutes after the start of initial mixing and when the slurry reaches the initial thickening point (i.e., the critical state where the slurry viscosity increases significantly but still has good fluidity). The timing of this addition is one of the core innovations of this invention. At this time, the initial slurry has formed a preliminary phosphate network, and the addition of calcium carbonate can participate in the subsequent reaction regulation without destroying the initial network.

[0078] (2) Control of calcium carbonate dosage: The amount of calcium carbonate added is determined by its Ca content. 2+ Based on the molar amount, it accounts for 10.44% of the total calcium molars in the first solid component. This dosage range ensures that calcium carbonate fully consumes the residual phosphoric acid and water-soluble precursors, while avoiding excessive CO2 production caused by excessive calcium carbonate, which leads to a porous green body.

[0079] (3) Subsequent reaction process: After adding calcium carbonate, maintain the system temperature at 75°C and continue stirring at a stirring rate of 270 rpm for 300 minutes. The stirring rate in this stage is slightly lower than that in the initial stage, which can ensure that the reaction proceeds fully while avoiding damage to the already formed phosphate network structure and ensuring the uniformity of the slurry.

[0080] 3. Filtration and drying

[0081] The reacted slurry was filtered to remove free water and trace impurities that had not participated in the reaction. The resulting filter cake was then placed in a constant-temperature drying oven at 110°C and dried for 2.5 hours to obtain the final composite calcium zinc phosphate refractory material. This drying process ensures the stable retention of crystal water in the filter cake while avoiding crystal structure damage caused by high temperatures.

[0082] Examples 1-5 are optimization experiments of dynamic feeding process without the addition of calcium carbonate. Examples 2-5 are basically the same as Example 1, except that the stirring speed, stirring temperature, drying parameters and raw material ratio are adjusted. Specific parameters and performance are shown in Table 1.

[0083]

[0084] As shown in Table 1, Example 3 exhibits the best overall performance, primarily due to its lowest water-soluble content (1.92 wt%). This superior characteristic stems from the synergistic effect of its specific formulation (40% ZnO, 20% H3PO4, 40% Ca(OH)2) and optimized process conditions (reaction temperature 85°C, stirring speed 225 rpm). This combination effectively promotes the formation of the insoluble zinc-calcium phosphate double salt, resulting in a product with a more compact and stable crystal structure, as evidenced by its lowest loss on ignition (8.6%). The stable crystal structure more firmly locks zinc, calcium, and phosphate ions within the crystal lattice, thereby minimizing the leaching of water-soluble substances. Simultaneously, the product of Example 3 has a suitable pH value (6.63), ensuring good compatibility in coating systems. In contrast, the comparative examples and Examples 1 and 2 may have resulted in incomplete reactions due to the high ZnO content; while in Examples 4 and 5, although the pH increased after further increasing the H3PO4 content and reaction temperature, the water-soluble content rebounded significantly, indicating a decrease in chemical stability. Therefore, Example 3 successfully achieved the best balance and unexpected technical effect in the core objective of this invention—reducing water-soluble content to improve the performance of rust-preventive pigments. The process conditions of Example 3 were used to adjust the ratio of calcium carbonate to calcium hydroxide, as shown in Examples 6-10.

[0085] Examples 6-10 (Composite calcium source process modified with calcium carbonate)

[0086] Examples 6-10 use the basic process parameters of Example 3 as a benchmark, adjusting the substitution ratio of calcium carbonate (in Ca...) 2+ (Based on molar number, it can replace 2%-10% of calcium hydroxide). Specific parameters and performance are shown in Table 2.

[0087]

[0088] This invention explores a modification scheme that partially replaces calcium hydroxide with calcium carbonate. The results in Table 2 show that this substitution produces unexpected synergistic effects. As shown in Examples 6 to 10, with increasing CaCO3 substitution, the water-soluble content of the product initially decreases and then increases, reaching a minimum of 0.91% at a substitution amount of 6% (Example 8). Although its weight loss on ignition (11.2%) is higher than that of the unsubstituted example (Example 3, 8.6%), indicating the formation of a new thermodynamically stable phase, this is precisely the reasonable and controllable structural evolution accompanying the minimization of water-soluble content. When the substitution amount exceeds 6% (Examples 9 and 10), the weight loss on ignition deteriorates sharply, while the water-soluble content increases, proving that excessive substitution introduces unstable factors. Therefore, Example 8 represents the optimal balance between formulation and performance in the modification scheme of this invention, achieving ultimate optimization of water-soluble content without compromising the basic structural stability of the product by introducing an appropriate amount of calcium carbonate.

[0089] To verify whether the introduction of calcium carbonate to partially replace calcium hydroxide altered the main crystalline phase structure of the zinc calcium phosphate anti-rust pigment, X-ray diffraction (XRD) analysis was performed on the products of the examples. The results showed (see...) Figure 1 , 2 Regardless of the substitution ratio of calcium carbonate (from 2% to 10%), the XRD patterns of the examples (Examples 6 to 10) were completely consistent with the diffraction peak positions and relative intensities of the standard PDF card (CaZn2(PO4)2·2H2O, PDF#86-2372).

[0090] This key data fully demonstrates that, under the process conditions described in this invention, the introduction of calcium carbonate did not alter the final crystalline phase of the product, and all samples successfully and exclusively produced the target compound—calcium zinc phosphate dihydrate. Therefore, the technical effects observed in this invention, particularly the significant reduction in water-soluble content (e.g., 0.91% in Example 8), are not due to the formation of a novel crystalline compound, but rather to the optimized adjustment of the crystallinity, grain size, crystal morphology, and surface chemical properties of the target crystal by an appropriate amount of calcium carbonate. This method of optimizing product performance by fine-tuning the reaction precursor while maintaining the main crystalline phase demonstrates the ingenuity and predictability of this invention, resulting in superior effects beyond its inherent characteristics.

[0091] V. Analysis of the Effects of the Implementation Examples

[0092] By comparing the proportions and examples, it can be seen that:

[0093] 1. Compared with the traditional one-step process (comparative example), the dynamic feeding process of the present invention (Examples 1-5) can significantly reduce the water-soluble content and improve mechanical properties. Among them, the water-soluble content of Example 3 is reduced by 9% compared with the comparative example, the 24-hour strength is increased by 50%, and the water resistance strength retention rate is increased by 13%.

[0094] 2. By introducing a calcium carbonate composite calcium source (Examples 6-10) on the basis of dynamic feeding process, the water-soluble content can be further reduced. The water-soluble content of Example 8 is reduced by 56.7% compared with the comparative example, and the mechanical properties and water resistance are improved simultaneously, realizing the synergistic optimization of processability, performance and compatibility.

Claims

1. A method for preparing a composite calcium-sourced zinc phosphate calcium refractory material, characterized in that, Includes the following steps: (1) Preparation of initial reaction slurry: According to the raw material molar ratio, the molar ratio of ZnO to Ca(OH)2 is 2:1 to 1:2, prepare a phosphoric acid aqueous solution with a mass percentage concentration of 30%-40%, and the phosphoric acid accounts for 10%-30% of the total mass of the raw materials; at an initial temperature of 20°C-35°C, the phosphoric acid aqueous solution is mixed with the first solid component and stirred at a stirring rate of 200-300 rpm for 20-40 minutes to form the initial reaction slurry. During this stage, the system temperature rises to 70°C-95°C. (2) Introducing calcium carbonate midway for reaction regulation: Within 20-30 minutes after the initial mixing begins in step (1), and when the slurry reaches the initial thickening point, calcium carbonate is added to the initial reaction slurry. The amount of calcium carbonate added is based on its Ca content. 2+ Based on the molar number, it accounts for 0%-30% of the total calcium molar number in the first solid component; then, at a reaction temperature of 70°C-95°C, stirring is continued for 20-40 minutes at a stirring rate of 150-300 rpm; (3) Filtration and drying: The slurry that has completed the reaction in step (2) is filtered, and the resulting filter cake is dried at a constant temperature of 100°C-110°C for 1.5-2.5 hours to obtain composite calcium source zinc phosphate calcium refractory material.

2. The preparation method of the composite calcium source zinc phosphate calcium refractory material according to claim 1, characterized in that, The molar ratio of zinc oxide to calcium hydroxide in step (1) is 1:

1.

3. The preparation method of the composite calcium source zinc phosphate calcium refractory material according to claim 1, characterized in that, The mass percentage concentration of the phosphoric acid aqueous solution in step (1) is 35%.

4. The preparation method of the composite calcium source zinc phosphate calcium refractory material according to claim 1, characterized in that, The phosphoric acid mentioned in step (1) accounts for 20% of the total mass of the raw materials.

5. The preparation method of the composite calcium source zinc phosphate calcium refractory material according to claim 1, characterized in that, The amount of calcium carbonate added in step (2) is determined by its Ca content. 2+ Based on the molar number, it accounts for 6% of the total calcium molar number in the first solid component.

6. A composite calcium-source zinc phosphate calcium refractory material, characterized in that, The refractory material is prepared by the preparation method according to any one of claims 1-5, wherein the main crystalline phase is CaZn2(PO4)2·2H2O, the water-soluble content is ≤0.91wt%, the pH value of the 10% aqueous suspension is 6.5-7.0, and the ignition vector at 600℃ is ≤11.2%.

7. The composite calcium source zinc phosphate calcium refractory material according to claim 6, characterized in that, Zn in the refractory material 2 + The content is 29.5%-34.5%, PO4 3- The content is 47.5%-48.7%, Ca 2+ The content is 10.3%-11.5%.

8. The composite calcium source zinc phosphate calcium refractory material according to claim 6, characterized in that, The early strength of the refractory material is ≥15MPa after curing at room temperature for 24 hours, and the 7-day strength is ≥30MPa.

9. The composite calcium source zinc phosphate calcium refractory material according to claim 6, characterized in that, The refractory material retains ≥90% of its strength after being immersed in water for 7 days.

10. An application of the composite calcium source zinc phosphate calcium refractory material according to any one of claims 6-9, characterized in that, The refractory material is used in high-end anti-corrosion coatings, water-resistant adhesives, or electronic packaging materials.

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