Rosin-coated stable amorphous calcium carbonate, method for its production and use

Abstract

The present application relates to amorphous calcium carbonate preparation technical field, specifically to a kind of rosin coated stable amorphous calcium carbonate, its preparation method and application, steps are: preparation rosin solvent;Polyaspartic acid solution is configured, and alcohol organic solvent is added to obtain composite solvent, regenerated powder is added into composite solvent and stirred uniformly into suspension, CO2 is injected to carry out wet carbonization, vacuum filtration separation, washing and drying, and the regenerated powder microparticle containing ACC is obtained;It is added into rosin solvent, and stirred and mixed uniformly, then vacuum filtration separation, washing and drying are carried out, and the rosin encapsulated amorphous calcium carbonate microparticle is obtained.Rosin can form uniform coating layer on the surface of ACC particle in viscous solvent state, fully isolate the influence of moisture on ACC crystallization, effectively maintain the stability of ACC.At the same time, in alkaline environment, controllable dissolution can be realized by protonation, and the cementing function of calcium carbonate can be restored in cement system, to improve material performance.

Description

Technical Field

[0001] This invention relates to the field of amorphous calcium carbonate preparation technology, specifically to a rosin-coated stable amorphous calcium carbonate, its preparation method, and its applications. Background Technology

[0002] Recycled construction waste powder is a high-quality carbonation material, and its application as an auxiliary cementitious material in cement-based materials has been widely recognized. During the carbonation process, the recycled powder mainly produces calcium carbonate and silica gel. Silica gel with high pozzolanic activity is considered the main source of its cementitious properties, while calcium carbonate exists in the form of calcite, primarily acting as a filler and nucleator. In recent years, wet carbonation, as an emerging method, has significantly improved the performance of recycled powder by controlling the crystal form of calcium carbonate. However, research on improving the cementitious properties of calcium carbonate remains relatively limited.

[0003] During carbonation, calcium carbonate can form various crystal forms, including calcite, aragonite, aragonite, and amorphous calcium carbonate (ACC). Theoretically, the most unstable ACC nucleates first, then transforms into the metastable aragonite or aragonite, eventually forming stable calcite. Due to its short-range disorder, ACC crystallizes into aragonite and calcite in just 3 days in air with 25% humidity. This instability severely limits its application in cement-based materials. Therefore, improving the stability of ACC is crucial to fully utilizing its cementitious properties.

[0004] Currently, methods to improve the stability of ACC mainly include controlling synthesis conditions and surface coating modification. Among these, controlling synthesis conditions such as temperature, pH, and additives can promote the formation of more stable ACC. Polyaspartic acid (pAsp), due to its long-chain structure and complexation with calcium ions, is highly effective in stabilizing ACC and inhibiting crystallization. However, controlling synthesis conditions is often complex and costly; in comparison, surface modification has greater application potential. Theoretically, coating the surface of ACC particles with organic or inorganic materials can prevent agglomeration, improve stability, and impart controlled-release properties, making it more suitable for cement systems.

[0005] To meet the application requirements of cement systems, surface-modified ACC must possess dual characteristics: stability in humid environments to avoid premature crystallization and loss of cementitious properties, while effectively releasing ACC during hydration. Given the highly alkaline environment (pH 12-13) of ordinary silicate cement paste, an ideal surface-modifying material should possess both water stability and alkali solubility. Currently used alkali-soluble materials, such as polyacrylic acid and polyvinyl alcohol, mostly rely on chemical polymerization methods, which are not only complex but may also induce premature crystallization of ACC.

[0006] Rosin, as a natural alkali-soluble material, has been widely used in the pharmaceutical field as an encapsulating agent for controlled drug release, demonstrating excellent application potential. Rosin is mainly composed of rosin acid and other resin acids, and is soluble in organic solvents. Its hydrophobic properties can effectively reduce the water absorption rate of concrete. Furthermore, similar to the mechanism of microencapsulation, hydroxide ions (OH-) in the concrete pore solution undergo a protonation reaction with rosin, increasing resin porosity and promoting its dissolution, thereby releasing internal substances. Based on these properties, rosin can serve as an environmentally friendly carrier for delivering pH-dependent corrosion inhibitors, providing a new approach for the surface modification of ACC (Adverse Chemicals).

[0007] Therefore, developing ACC and its preparation method that combine environmental stability and applicability to cement systems remains a key issue that urgently needs to be addressed. Summary of the Invention

[0008] One of the objectives of this invention is to provide a rosin-coated stable amorphous calcium carbonate, with rosin located on the outer surface of the amorphous calcium carbonate and on the inner / outer surface of the carbonized regenerated micro powder. This material combines environmental stability and applicability to cement systems, and is a carbonized cementitious material with long-term stable performance, thus expanding the practical application value of ACC in the cement field.

[0009] The second objective of this invention is to provide a method for preparing rosin-coated stable amorphous calcium carbonate, which is simple and easy to adjust.

[0010] The third objective of this invention is to provide a rosin-coated stable amorphous calcium carbonate, its preparation method, and its application.

[0011] One of the solutions adopted to achieve the objective of this invention is: a method for preparing rosin-coated stable amorphous calcium carbonate, comprising the following steps:

[0012] (1) Preparation of rosin solvent: A certain mass of rosin powder is dissolved in an alcohol-based organic solvent to prepare rosin solvent;

[0013] (2) Preparation of carbonized regenerated micro powder containing amorphous calcium carbonate: A certain mass of polyaspartic acid is dissolved in water to prepare a polyaspartic acid solution. Then, an alcohol organic solvent is added and mixed evenly to obtain a composite solvent. Then, regenerated micro powder is added to the composite solvent and stirred and mixed to form a suspension. CO2 is slowly injected into the suspension for wet carbonization. After carbonization, vacuum filtration, washing and drying are performed to obtain carbonized regenerated micro powder micron particles containing amorphous calcium carbonate.

[0014] (3) Add the carbonized regenerated micronized powder containing amorphous calcium carbonate prepared in step (2) to the rosin solvent prepared in step (1), stir and mix evenly, then perform vacuum filtration separation, washing and drying to obtain rosin-encapsulated amorphous calcium carbonate micronized particles.

[0015] Preferably, in step (1), the alcohol organic solvent is anhydrous ethanol, methanol, or isopropanol, the concentration of the rosin solvent is 10wt%-15wt%, and the viscosity of the rosin solvent is 300-400cp.

[0016] Preferably, in step (2), the alcohol organic solvent is anhydrous ethanol, methanol, or isopropanol, the concentration of the polyaspartic acid solution is 10wt%-15wt%, and the mass percentage of the alcohol organic solvent in the composite solvent is 10%-30%.

[0017] Preferably, in step (2), the recycled micro powder is solid powder made by crushing and grinding waste concrete into a particle size of 200-2000 mesh, and the solid-liquid ratio of the recycled micro powder to the composite solvent is 1g:20-50mL.

[0018] Preferably, in step (2), the CO2 gas injection flow rate is 0.1-0.25 L / min, the carbonization process lasts for 10-20 minutes, and the solvent pH is 8-8.5.

[0019] Preferably, in step (3), the solid-liquid ratio of carbonized regenerated micronized powder containing amorphous calcium carbonate to rosin solvent is 1g:20-50mL.

[0020] Preferably, in step (3), the thickness of the rosin coating layer on the surface of the amorphous calcium carbonate particles is 40-60 nm.

[0021] Preferably, in step (3), the stirring speed is 300-500 rpm and the total stirring time is 45-60 hours.

[0022] The second objective of this invention is achieved by using a rosin-coated stable amorphous calcium carbonate prepared by the aforementioned method.

[0023] The solution adopted to achieve the third objective of this invention is: the application of the aforementioned rosin-stabilized amorphous calcium carbonate as a cementing material in a cement system.

[0024] The method of the present invention prepares rosin-coated stable amorphous calcium carbonate, wherein the rosin is located on the outer surface of the amorphous calcium carbonate and on the inner / outer surface of the carbonized regenerated micro powder, and the average particle size of the rosin-coated micro powder is less than or equal to 100 μm.

[0025] The rosin coating layers enable ACC to maintain long-term stability in external environments, allowing for stable storage in both dry and humid conditions. When rosin-stabilized ACC is applied to cement systems, the rosin coating gradually dissolves in the initial alkaline environment, allowing the ACC to re-expose to external moisture and undergo crystallization transformation. During this transformation, ACC forms a cross-linked structure of calcium carbonate crystals through a dissolution-recrystallization mechanism and solid-state transformation, tightly binding the surrounding cement particles to create a dense matrix structure. The high stability of ACC ensures its excellent cementitious properties in cement systems, thereby enhancing the overall performance of cement-based materials.

[0026] The present invention has the following advantages and beneficial effects:

[0027] (1) The material has excellent compatibility. The unique properties of rosin make it particularly suitable for cement systems. Rosin has excellent adhesion properties. In a viscous solvent state, it can form a uniform coating layer on the surface of ACC particles, which can effectively isolate the influence of moisture on ACC crystallization and maintain the stability of ACC. At the same time, it can be controlled to dissolve in an alkaline environment through protonation. In cement systems, it can restore the cementitious function of calcium carbonate and improve the material performance.

[0028] (2) The rosin coating process is simple and efficient. It adopts a simple soaking method to achieve ACC encapsulation. It is easy to operate, does not require the addition of additional reagents or complex equipment, has a wide range of raw material sources, low cost, good process repeatability, and is suitable for large-scale production.

[0029] (3) Significant environmental benefits: fully utilize waste concrete resources, realize high-value utilization of solid waste, reduce raw material consumption, and make the production process green and environmentally friendly. Attached Figure Description

[0030] Figure 1 This is a transmission electron microscope image of the rosin-coated stable amorphous calcium carbonate prepared in Example 1 of this invention.

[0031] Figure 2 This is a scanning electron microscope image of the rosin-coated stable amorphous calcium carbonate prepared in Example 1 of this invention.

[0032] Figure 3 This is the energy dispersive spectroscopy (EDS) analysis diagram of the rosin-coated stable amorphous calcium carbonate prepared in Example 1 of this invention.

[0033] Figure 4 The infrared spectra of rosin-coated stable amorphous calcium carbonate prepared in Example 1 at different times;

[0034] Figure 5 The infrared spectra of rosin-coated stable amorphous calcium carbonate prepared in Example 1 under different humidity conditions;

[0035] Figure 6 This is a moisture absorption curve of the rosin-coated stable amorphous calcium carbonate prepared in Example 1.

[0036] Figure 7 This is a strength development diagram of the rosin-coated stable amorphous calcium carbonate prepared in Example 1 applied to a cement system. Detailed Implementation

[0037] To better understand the present invention, the following embodiments are further illustrations of the present invention, but the content of the present invention is not limited to the following embodiments.

[0038] Example 1

[0039] This application provides a method for preparing rosin-coated stable amorphous calcium carbonate, comprising the following steps:

[0040] At 25°C, 20g of rosin powder was dissolved in 200g of anhydrous ethanol to form a 10wt% rosin solvent. Subsequently, 9g of polyaspartic acid (pAsp, molecular weight 4100 Da) was dissolved in 60g of deionized water to form a 15wt% pAsp solution. Then, 140g of anhydrous ethanol and 30g of the pAsp solution were mixed in a beaker at a ratio of 7:3 and stirred at 500 rpm for 5 minutes to form a mixed solution with a total mass of 200g. Next, 10g of recycled concrete powder was added to the mixed solution and stirred at 500 rpm for 5 minutes to ensure thorough mixing of the components. Then, carbonization was performed by slowly injecting pure CO2 (purity ≥99.9%) into the suspension at a flow rate of 0.2L / min for 15 minutes of wet carbonization. After carbonization, the suspension was separated by vacuum filtration. The separated solids were washed twice with anhydrous ethanol and then dried in a vacuum drying oven at 40°C for 24 hours to obtain carbonized regenerated micro powder containing ACC. The ACC-containing carbonized regenerated micro powder was then added to the previously prepared rosin solvent and stirred at 350 rpm for 1 hour at 25°C. The gelatinous mixture was then separated by vacuum filtration again. Finally, the resulting gelatinous precipitate was dried in an oven at 40°C to obtain rosin-coated stable amorphous calcium carbonate material.

[0041] Figure 1 The image shows a transmission electron microscope (TEM) image of the rosin-coated stable amorphous calcium carbonate prepared in this embodiment. As can be seen from the image, the thickness of the rosin coating layer on the surface of the amorphous calcium carbonate particles is 50 nm.

[0042] Figure 2 The image shows a scanning electron microscope (SEM) image of the rosin-coated stable amorphous calcium carbonate prepared in this embodiment. As can be seen from the image, the surface of the amorphous calcium carbonate particles is almost completely coated with rosin, and the rosin encapsulation effect is good.

[0043] Figure 3 The image shows the energy dispersive spectroscopy (EDS) analysis of the rosin-coated stable amorphous calcium carbonate prepared in this embodiment. As can be seen from the image, the proportion of Ca and Si elements contained in the amorphous calcium carbonate itself is very small, while the C and O elements contained in the rosin are still significant, which indicates that the surface of the amorphous calcium carbonate particles has been coated with rosin.

[0044] Figure 4 The images show the infrared spectra of rosin-coated stable amorphous calcium carbonate prepared in this embodiment at different times. As can be seen from the figures, after 60 days of storage, the concentration of calcium carbonate at 1410-1460 cm⁻¹... -1 However, the presence of a flat infrared double peak proves that the amorphous calcium carbonate coated with rosin can still exist stably after long-term storage.

[0045] Figure 5 The images show the infrared spectra of rosin-coated stable amorphous calcium carbonate prepared in this embodiment under different humidity levels. As can be seen from the figures, after being placed in a high humidity environment (RH 50%-90%) for 7 days, the concentration of calcium carbonate at 1410-1460 cm⁻¹... -1 However, the presence of flat infrared double peaks proves that amorphous calcium carbonate coated with rosin can still exist stably under high humidity conditions.

[0046] Figure 6 The figure shows the hygroscopic curve of the rosin-coated stable amorphous calcium carbonate prepared in this embodiment. As can be seen from the figure, the hygroscopicity of the rosin-coated amorphous calcium carbonate decreased by 83%, and the significant decrease in hygroscopicity is beneficial to the long-term stability of the amorphous calcium carbonate.

[0047] Figure 7 The graph shows the strength development of rosin-coated stable amorphous calcium carbonate in a cement system as described in this embodiment. As can be seen from the graph, compared with direct addition to the cement system, the strength of the amorphous calcium carbonate-cement composite system added after 28 days decreased by 11.1%, while the strength of the rosin-coated stable amorphous calcium carbonate-cement composite system remained unchanged. This indicates that rosin coating effectively ensures the long-term stability of the cementing ability of amorphous calcium carbonate.

[0048] Comparative Example 1

[0049] The difference from Example 1 is that the 10wt% rosin solvent is replaced with a 1wt% rosin solvent, while the types and order of addition of other raw materials remain the same as in Example 1.

[0050] Comparative Example 2

[0051] The difference from Example 1 is that the 10wt% rosin solvent is replaced with a 5wt% rosin solvent, while the types and order of addition of other raw materials remain the same as in Example 1.

[0052] Comparative Example 3

[0053] The difference from Example 1 is that the 10wt% rosin solvent is replaced with an 8wt% rosin solvent, while the types and order of addition of other raw materials remain the same as in Example 1.

[0054] Example 2

[0055] This application provides a method for preparing rosin-coated stable amorphous calcium carbonate, comprising the following steps:

[0056] At 25°C, 24g of rosin powder was dissolved in 200g of anhydrous ethanol to form a 12wt% rosin solvent. Then, 7.2g of polyaspartic acid (pAsp, molecular weight 4100 Da) was dissolved in 60g of deionized water to form a 12wt% pAsp solution. Next, 140g of anhydrous ethanol and 30g of the pAsp solution were mixed in a beaker at a ratio of 7:3 and stirred at 500 rpm for 5 minutes to form a mixed solution with a total mass of 200g. Then, 10g of recycled concrete powder was added to the mixed solution and stirred at 500 rpm for 5 minutes to ensure thorough mixing of the components. Finally, carbonization was performed by slowly injecting pure CO2 (purity ≥99.9%) into the suspension at a flow rate of 0.2L / min for 15 minutes of wet carbonization. After carbonization, the suspension was separated by vacuum filtration. The separated solids were washed twice with anhydrous ethanol and then dried in a vacuum drying oven at 40°C for 24 hours to obtain carbonized regenerated micro powder containing ACC. The ACC-containing carbonized regenerated micro powder was then added to the previously prepared rosin solvent and stirred at 350 rpm for 1 hour at 25°C. The gelatinous mixture was then separated by vacuum filtration again. Finally, the resulting gelatinous precipitate was dried in an oven at 40°C to obtain rosin-coated stable amorphous calcium carbonate material.

[0057] Example 3

[0058] At 25°C, 28g of rosin powder was dissolved in 200g of anhydrous ethanol to form a 14wt% rosin solvent. Subsequently, 9g of polyaspartic acid (pAsp, molecular weight 4100 Da) was dissolved in 60g of deionized water to form a 15wt% pAsp solution. Then, 140g of anhydrous ethanol and 30g of the pAsp solution were mixed in a beaker at a ratio of 7:3 and stirred at 500 rpm for 5 minutes to form a mixed solution with a total mass of 200g. Next, 10g of recycled concrete powder was added to the mixed solution and stirred at 500 rpm for 5 minutes to ensure thorough mixing of the components. Then, carbonization was performed by slowly injecting pure CO2 (purity ≥99.9%) into the suspension at a flow rate of 0.2L / min for 15 minutes of wet carbonization. After carbonization, the suspension was separated by vacuum filtration. The separated solids were washed twice with anhydrous ethanol and then dried in a vacuum drying oven at 40°C for 24 hours to obtain carbonized regenerated micro powder containing ACC. The ACC-containing carbonized regenerated micro powder was then added to the previously prepared rosin solvent and stirred at 350 rpm for 1 hour at 25°C. The gelatinous mixture was then separated by vacuum filtration again. Finally, the resulting gelatinous precipitate was dried in an oven at 40°C to obtain rosin-coated stable amorphous calcium carbonate material.

[0059] Example 4

[0060] At 25°C, 30g of rosin powder was dissolved in 200g of anhydrous ethanol to form a 15wt% rosin solvent. Subsequently, 9g of polyaspartic acid (pAsp, molecular weight 4100 Da) was dissolved in 60g of deionized water to form a 15wt% pAsp solution. Then, 140g of anhydrous ethanol and 30g of the pAsp solution were mixed in a beaker at a ratio of 7:3 and stirred at 500 rpm for 5 minutes to form a mixed solution with a total mass of 200g. Next, 10g of recycled concrete powder was added to the mixed solution and stirred at 500 rpm for 5 minutes to ensure thorough mixing of the components. Then, carbonization was performed by slowly injecting pure CO2 (purity ≥99.9%) into the suspension at a flow rate of 0.2L / min for 15 minutes of wet carbonization. After carbonization, the suspension was separated by vacuum filtration. The separated solids were washed twice with anhydrous ethanol and then dried in a vacuum drying oven at 40°C for 24 hours to obtain carbonized regenerated micro powder containing ACC. The ACC-containing carbonized regenerated micro powder was then added to the previously prepared rosin solvent and stirred at 350 rpm for 1 hour at 25°C. The gelatinous mixture was then separated by vacuum filtration again. Finally, the resulting gelatinous precipitate was dried in an oven at 40°C to obtain rosin-coated stable amorphous calcium carbonate material.

[0061] This invention tested the materials described in the above embodiments under normal environmental conditions (temperature 25±5℃, humidity 50±5%), and the test results are shown in Table 1. The stable existence time of ACC is defined as the number of days in which the ACC content decreases by no more than 15% compared to the initial ACC content. Strength is the strength of the cement system obtained at 28 days after the ACC (whether or not it is rosin-coated) has been left outdoors for 28 days, and then replaced with cement at a 20% replacement rate.

[0062] Table 1. Test results of rosin-coated stable amorphous calcium carbonate

[0063]

[0064]

[0065] As shown in Table 1, the stable existence time of ACC after rosin coating can be extended from the original 3 days to about 60 days. In addition, in the cement system, rosin ensures the long-term stability of ACC's cementitious ability, and the resulting cement system has significantly higher strength at 28 days.

[0066] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing rosin-coated stable amorphous calcium carbonate, characterized in that, Includes the following steps: (1) Preparation of rosin solvent: A certain mass of rosin powder is dissolved in an alcohol-based organic solvent to prepare a rosin solvent, wherein the concentration of the rosin solvent is 10 wt%-15 wt%; (2) Preparation of carbonized regenerated micro powder containing amorphous calcium carbonate: A certain mass of polyaspartic acid is dissolved in water to prepare a polyaspartic acid solution, and then an alcohol organic solvent is added and mixed evenly to obtain a composite solvent. Then, regenerated micro powder is added to the composite solvent and stirred and mixed to form a suspension. CO2 is slowly injected into the suspension for wet carbonization. After carbonization, vacuum filtration, washing and drying are performed to obtain carbonized regenerated micro powder micron particles containing amorphous calcium carbonate. The regenerated micro powder is made by crushing and grinding waste concrete into solid powder with a particle size of 200-2000 mesh. (3) Add the carbonized regenerated micronized powder containing amorphous calcium carbonate prepared in step (2) to the rosin solvent prepared in step (1), stir and mix evenly, then perform vacuum filtration separation, washing and drying to obtain rosin-encapsulated amorphous calcium carbonate micronized particles.

2. The method for preparing rosin-coated stable amorphous calcium carbonate as described in claim 1, characterized in that, In step (1), the alcohol organic solvent is anhydrous ethanol, methanol, or isopropanol, and the rosin solvent viscosity is 300-400 cp.

3. The method for preparing rosin-coated stable amorphous calcium carbonate as described in claim 1, characterized in that, In step (2), the alcohol organic solvent is anhydrous ethanol, methanol, or isopropanol, the concentration of the polyaspartic acid solution is 10 wt%-15 wt%, and the mass percentage of the alcohol organic solvent in the composite solvent is 10%-30%.

4. The method for preparing rosin-coated stable amorphous calcium carbonate as described in claim 1, characterized in that, In step (2), the solid-liquid ratio of the regenerated micro powder to the composite solvent is 1g:20-50mL.

5. The method for preparing rosin-coated stable amorphous calcium carbonate as described in claim 1, characterized in that, In step (2), the CO2 gas injection rate is 0.1-0.25 L / min, the carbonization process lasts for 10-20 minutes, and the solvent pH is 8-8.

5.

6. The method for preparing rosin-coated stable amorphous calcium carbonate as described in claim 1, characterized in that, In step (3), the solid-liquid ratio of carbonized regenerated micronized powder containing amorphous calcium carbonate to rosin solvent is 1g:20-50mL.

7. The method for preparing rosin-coated stable amorphous calcium carbonate as described in claim 1, characterized in that, In step (3), the thickness of the rosin coating layer on the surface of the amorphous calcium carbonate particles is 40-60 nm.

8. The method for preparing rosin-coated stable amorphous calcium carbonate as described in claim 1, characterized in that, In step (3), the stirring speed is 300-500 rpm and the total stirring time is 45-60 hours.

9. A rosin-coated and stabilized amorphous calcium carbonate, characterized in that, It is prepared by any one of the preparation methods described in claims 1 to 8.

10. The application of rosin-stabilized amorphous calcium carbonate as described in claim 9 as a cementing material in a cement system.

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