Amorphous calcium carbonate with stable rosin coating as well as preparation method and application of amorphous calcium carbonate

Abstract

The invention relates to the technical field of amorphous calcium carbonate preparation, in particular to rosin-coated stable amorphous calcium carbonate and a preparation method and application thereof. Preparing a polyaspartic acid solution, adding an alcohol organic solvent to obtain a composite solvent, adding the regenerated micro-powder into the composite solvent, stirring and uniformly mixing to obtain a suspension, injecting CO2, and carrying out wet carbonization, vacuum filtration separation, washing and drying to obtain regenerated micro-powder micron particles containing ACC; the preparation method comprises the following steps: adding the calcium carbonate into a rosin solvent, uniformly stirring and mixing, and then carrying out vacuum filtration separation, washing and drying to obtain the rosin-packaged amorphous calcium carbonate micron particles. A uniform coating layer can be formed on the surfaces of ACC particles in a viscous solvent state, so that the influence of moisture on ACC crystallization is fully isolated, and the ACC stability is effectively maintained. Meanwhile, controllable dissolution is achieved through protonation in an alkaline environment, the gelling function of calcium carbonate can be recovered in a cement system, and the material performance is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of amorphous calcium carbonate preparation, and particularly relates to a rosin-coated and stabilized amorphous calcium carbonate, a preparation method thereof, and an application thereof. Background Art

[0002] Recycled fine powder of construction waste is a high-quality carbonization material, and its application as an auxiliary cementitious material in cement-based materials has been widely recognized. During the carbonization process, the recycled fine powder mainly generates calcium carbonate and silica gel. Among them, the silica gel with high pozzolanic activity is considered to be the main source of cementitious properties, while the calcium carbonate exists in the form of calcite and mainly plays a role in filling and nucleation. In recent years, as an emerging method, wet carbonization has significantly improved the performance of recycled fine powder by regulating the crystal form of calcium carbonate. However, the research on improving the cementitious properties of calcium carbonate is still relatively limited.

[0003] Calcium carbonate can form crystal forms such as calcite, aragonite, vaterite, and amorphous calcium carbonate (ACC) during the carbonization process. Theoretically, the most unstable ACC nucleates first, and then transforms into metastable vaterite or aragonite, and finally forms stable calcite. Due to the short-range disorder characteristics of ACC, it can crystallize into vaterite and calcite in the air with a humidity of 25% in only 3 days. This instability seriously restricts its application effect in cement-based materials. Therefore, improving the stability of ACC has become the key to fully exerting its cementitious properties.

[0004] Currently, the methods for improving the stability of ACC mainly include regulating synthesis conditions and surface coating modification. Among them, more stable ACC can be promoted by controlling synthesis conditions such as temperature, pH value, and additives. Polyaspartic acid (pAsp) has a significant effect on stabilizing ACC and inhibiting crystallization due to the complexation of its long-chain structure with calcium ions. However, the regulation of synthesis conditions is often a complex process and has a high cost. In contrast, surface modification has greater application potential. Theoretically, by coating organic or inorganic materials on the surface of ACC particles, not only can agglomeration be prevented, but also the stability can be improved, and at the same time, its controlled release characteristics can be given, making it more suitable for the cement system.

[0005] To meet the application requirements of the cement system, the surface-modified ACC needs to have dual characteristics: being stable in a humid environment to avoid loss of cementitious properties caused by premature crystallization, and being able to be effectively released during the hydration process. Considering the high-alkaline environment (pH 12-13) of ordinary Portland cement paste, the ideal surface modification material should have both water stability and alkali solubility. Currently, commonly used alkali-soluble materials, such as polyacrylic acid and polyvinyl alcohol, mostly rely on chemical polymerization methods, which are not only complex in process but also may cause premature crystallization of ACC.

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

[0007] Therefore, the development of ACC with both environmental stability and applicability to the cement system and its preparation method remains a key issue to be urgently solved. Summary of the Invention

[0008] One object of the present invention is an amorphous calcium carbonate stabilized by rosin coating, where rosin is located on the outer surface of the amorphous calcium carbonate and inside / outside the carbonized recycled fine powder, having both environmental stability and applicability to the cement system. This material is a carbonized cementitious material with long-term stable performance, expanding the practical application value of ACC in the cement field.

[0009] Another object of the present invention is to provide a preparation method for amorphous calcium carbonate stabilized by rosin coating, which is simple and easy to adjust.

[0010] A third object of the present invention is to provide an amorphous calcium carbonate stabilized by rosin coating, its preparation method, and its application.

[0011] The solution adopted by the present invention to achieve the first object is: a preparation method for amorphous calcium carbonate stabilized by rosin coating, comprising the following steps:

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

[0013] (2) Preparation of carbonized recycled fine powder containing amorphous calcium carbonate: Dissolve a certain mass of polyaspartic acid in water to prepare a polyaspartic acid solution, then add an alcohol-based organic solvent and mix evenly to obtain a composite solvent. Then add recycled fine powder to the composite solvent and stir to mix evenly into a suspension. Slowly inject CO2 into the suspension for wet carbonization. After carbonization, perform vacuum filtration separation, washing, and drying to obtain carbonized recycled fine powder micron particles containing amorphous calcium carbonate;

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

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

[0016] Preferably, in step (2), the alcohol organic solvent is anhydrous ethanol, methanol, or isopropyl alcohol, 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 fine powder is obtained by crushing and grinding waste concrete into solid powder with a particle size of 200-2000 mesh, and the solid-liquid ratio of the recycled fine powder to the composite solvent is 1 g: 20-50 mL.

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

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

[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 revolutions per minute, and the total stirring time is 45-60 hours.

[0022] The solution adopted by the present invention to achieve the second object is: an amorphous calcium carbonate stabilized by rosin coating, prepared by the described preparation method.

[0023] The solution adopted by the present invention to achieve the third object is: an application of the described rosin-stabilized amorphous calcium carbonate as a gelling material in a cement system.

[0024] The amorphous calcium carbonate stabilized by rosin coating prepared by the method of the present invention, the rosin is located on the outer surface of the amorphous calcium carbonate and the inner / outer surface of the carbonized recycled fine powder, and the average particle size of the rosin-coated fine powder is less than or equal to 100 μm.

[0025] The rosin coating layer enables ACC to remain stable in the external environment for a long time and can be stably stored in both dry and humid environments. When the rosin-stabilized ACC is applied to the cement system, the rosin coating layer gradually dissolves in the initial alkaline environment, allowing ACC to re-contact external moisture and undergo crystallization transformation. During the crystallization transformation process, ACC forms a cross-linked structure of calcium carbonate crystals through the dissolution-recrystallization mechanism and solid-state transformation, tightly binding the surrounding cement solid particles and constructing a dense matrix structure. The high stability of ACC ensures its excellent gelling performance in the cement system, thus enhancing the overall performance of the cement-based material.

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

[0027] (1) Excellent material adaptability. The unique properties of rosin make it particularly suitable for the cement system. Rosin has excellent adhesion performance and can form a uniform coating layer on the surface of ACC particles in a viscous solvent state, effectively isolating the influence of moisture on the crystallization of ACC and maintaining the stability of ACC. At the same time, it can be controllably dissolved through protonation in an alkaline environment and can restore the gelling function of calcium carbonate in the cement system, improving the material performance.

[0028] (2) The rosin coating process is simple and efficient. The ACC encapsulation is achieved by a simple immersion method, which is convenient to operate, does not require the addition of extra 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. It makes full use of waste concrete resources, realizes the high-value utilization of solid waste, reduces the consumption of raw materials, and the production process is green and environmentally friendly. Description of the Drawings

[0030] Figure 1 It is the transmission electron microscope image of the rosin-coated and stabilized amorphous calcium carbonate prepared in Example 1;

[0031] Figure 2 It is the scanning electron microscope image of the rosin-coated and stabilized amorphous calcium carbonate prepared in Example 1;

[0032] Figure 3 It is the energy spectrum analysis image of the rosin-coated and stabilized amorphous calcium carbonate prepared in Example 1;

[0033] Figure 4 It is the infrared spectrum image of the rosin-coated and stabilized amorphous calcium carbonate prepared in Example 1 at different times;

[0034] Figure 5 It is the infrared spectrum image of the rosin-coated and stabilized amorphous calcium carbonate prepared in Example 1 at different humidities;

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

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

[0037] For a better understanding of the present invention, the following examples are further descriptions of the present invention, but the content of the present invention is not limited to the following examples only.

[0038] Example 1

[0039] The embodiment of the present application provides a preparation method of rosin-coated stable amorphous calcium carbonate, including the following steps:

[0040] At 25 °C, 20 g of rosin powder is dissolved in 200 g of absolute ethanol to form a rosin solvent with a concentration of 10 wt%. Subsequently, 9 g of polyaspartic acid (pAsp, molecular mass 4100 Da) is dissolved in 60 g of deionized water to form a 15 wt% pAsp solution. Then, 140 g of absolute ethanol and 30 g of the pAsp solution are mixed in a beaker at a ratio of 7:3 and stirred at 500 revolutions per minute for 5 minutes to form a mixed solution with a total mass of 200 g. After that, 10 g of recycled concrete micro powder is added to the mixed solution and stirred at 500 revolutions per minute for 5 minutes to ensure sufficient mixing among the components. Then, carbonization treatment is carried out, and pure CO2 (purity ≥ 99.9%) is slowly injected into the suspension at a flow rate of 0.2 L / min for 15 minutes of wet carbonization. After the carbonization ends, the suspension is separated by vacuum filtration, the separated solid is washed twice with absolute ethanol, and finally dried in a vacuum drying oven at 40 °C for 24 hours to obtain carbonized recycled micro powder containing ACC. Then, the carbonized recycled micro powder containing ACC is added to the previously prepared rosin solvent, stirred at 350 revolutions per minute at 25 °C for 1 hour, the colloidal mixture is separated by vacuum filtration again, and finally the obtained colloidal precipitate is placed in an oven at 40 °C for drying, and finally a rosin-coated stable amorphous calcium carbonate material is obtained.

[0041] Figure 1 This is the transmission electron microscope image of the rosin-coated stable amorphous calcium carbonate prepared in this example. It can be seen from the figure that the thickness of the rosin coating layer on the surface of the amorphous calcium carbonate particles is 50 nm.

[0042] Figure 2 This is the scanning electron microscope image of the rosin-coated stable amorphous calcium carbonate prepared in this example. It can be seen from the figure that the surface of the amorphous calcium carbonate particles is almost completely coated with rosin, and the rosin encapsulation effect is good.

[0043] Figure 3 This is the energy spectrum analysis diagram of the rosin-coated stable amorphous calcium carbonate prepared in this example. It can be seen from the figure that the proportions of Ca and Si elements contained in the amorphous calcium carbonate itself are very small, while the C and O elements contained in the rosin are still significant, indicating that the surface of the amorphous calcium carbonate particles has been coated with rosin.

[0044] Figure 4 This is the infrared spectrum diagram of the rosin-coated stable amorphous calcium carbonate prepared in this example at different times. It can be seen from the figure that after 60 days of placement, there are still gentle infrared doublets at 1410 - 1460 cm -1 which proves that the rosin-coated amorphous calcium carbonate can still exist stably after long-term placement.

[0045] Figure 5 This is the infrared spectrum diagram of the rosin-coated stable amorphous calcium carbonate prepared in this example at different humidities. It can be seen from the figure that after 7 days of placement in a high-humidity environment (RH 50% - 90%), there are still gentle infrared doublets at 1410 - 1460 cm -1 which proves that the rosin-coated amorphous calcium carbonate can still exist stably in a high-humidity environment.

[0046] Figure 6 This is the moisture absorption curve diagram of the rosin-coated stable amorphous calcium carbonate prepared in this example. It can be seen from the figure that the moisture absorption of the rosin-coated amorphous calcium carbonate has decreased by 83%, and the significant decrease in moisture absorption is beneficial to the long-term stability of the amorphous calcium carbonate.

[0047] Figure 7 This is the strength development diagram of the rosin-coated stable amorphous calcium carbonate applied to the cement system in this example. It can be seen from the figure that compared with directly incorporating it into the cement system, the strength of the amorphous calcium carbonate-cement composite system incorporated after 28 days of placement has decreased by 11.1%, while the strength of the rosin-coated stable amorphous calcium carbonate-cement composite system remains unchanged, indicating that rosin coating effectively ensures the long-term stability of the gelling ability of the amorphous calcium carbonate.

[0048] Comparative Example 1

[0049] The difference from Example 1 is that on the basis of Example 1, the rosin solvent with a concentration of 10 wt% is replaced by a rosin solvent with a concentration of 1 wt%, and the types and addition sequences of other raw materials are the same as those in Example 1.

[0050] Comparative Example 2

[0051] The difference from Example 1 is that on the basis of Example 1, the rosin solvent with a concentration of 10 wt% is replaced by a rosin solvent with a concentration of 5 wt%, and the types and addition sequences of other raw materials are the same as those in Example 1.

[0052] Comparative Example 3

[0053] The difference from Example 1 is that on the basis of Example 1, the rosin solvent with a concentration of 10 wt% is replaced by a rosin solvent with a concentration of 8 wt%, and the types and addition sequences of other raw materials are the same as those in Example 1.

[0054] Example 2

[0055] The embodiment of the present application provides a preparation method of amorphous calcium carbonate stabilized by rosin coating, including the following steps:

[0056] At 25 °C, 24 g of rosin powder is dissolved in 200 g of absolute ethanol to form a rosin solvent with a concentration of 12 wt%. Subsequently, 7.2 g of polyaspartic acid (pAsp, molecular mass 4100 Da) is dissolved in 60 g of deionized water to form a 12 wt% pAsp solution. Then, 140 g of absolute ethanol and 30 g of the pAsp solution are mixed in a beaker at a ratio of 7:3 and stirred at 500 revolutions per minute for 5 minutes to form a mixed solution with a total mass of 200 g. After that, 10 g of recycled concrete micro powder is added to the mixed solution and stirred at 500 revolutions per minute for 5 minutes to ensure sufficient mixing between the components. Then, carbonization treatment is carried out, and pure CO2 (purity ≥ 99.9%) is slowly injected into the suspension at a flow rate of 0.2 L / min for 15 minutes of wet carbonization. After the carbonization is completed, the suspension is separated by vacuum filtration, the separated solid is washed twice with absolute ethanol, and finally dried in a vacuum drying oven at 40 °C for 24 hours to obtain carbonized recycled micro powder containing ACC. Then, the carbonized recycled micro powder containing ACC is added to the previously prepared rosin solvent, stirred at 350 revolutions per minute at 25 °C for 1 hour, and then the colloidal mixture is separated by vacuum filtration again. Finally, the obtained colloidal precipitate is placed in an oven at 40 °C for drying, and finally a material of amorphous calcium carbonate stabilized by rosin coating is obtained.

[0057] Example 3

[0058] At 25°C, 28g of rosin powder was dissolved in 200g of anhydrous ethanol to form a rosin solvent with a concentration of 14wt%. Subsequently, 9g of polyaspartic acid (pAsp, molecular weight 4100Da) was dissolved in 60g of deionized water to form a 15wt% pAsp solution. Then 140g of anhydrous ethanol and 30g of 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. After that, 10g of recycled concrete powder was added to the mixed solution and stirred at 500 rpm for 5 minutes to ensure that the components were fully mixed. Then carbonization treatment was carried out, and pure CO2 (purity ≥99.9%) was slowly injected into the suspension at a flow rate of 0.2L / min for 15 minutes of wet carbonization. After the carbonization is completed, the suspension is separated by vacuum filtration, and the separated solid is washed twice with anhydrous ethanol, and finally dried in a vacuum drying oven at 40°C for 24 hours to obtain carbonized regenerated micropowder containing ACC. Then, the carbonized regenerated micropowder containing ACC is added to the previously prepared rosin solvent, and after stirring at 350 rpm for 1 hour at 25°C, the colloidal mixture is separated by vacuum filtration again, and finally the obtained colloidal precipitate is placed in an oven at 40°C to dry, and finally a rosin-coated stable amorphous calcium carbonate material is obtained.

[0059] Example 4

[0060] At 25 ° C, 30g of rosin powder was dissolved in 200g of anhydrous ethanol to form a rosin solvent with a concentration of 15wt%. Subsequently, 9g of polyaspartic acid (pAsp, molecular weight 4100Da) was dissolved in 60g of deionized water to form a 15wt% pAsp solution. Then 140g of anhydrous ethanol and 30g of 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. After that, 10g of recycled concrete powder was added to the mixed solution and stirred at 500 rpm for 5 minutes to ensure that the components were fully mixed. Then carbonization treatment was carried out, and pure CO2 (purity ≥99.9%) was slowly injected into the suspension at a flow rate of 0.2L / min for 15 minutes of wet carbonization. After the carbonization is completed, the suspension is separated by vacuum filtration, and the separated solid is washed twice with anhydrous ethanol, and finally dried in a vacuum drying oven at 40°C for 24 hours to obtain carbonized regenerated micropowder containing ACC. Then, the carbonized regenerated micropowder containing ACC is added to the previously prepared rosin solvent, and after stirring at 350 rpm for 1 hour at 25°C, the colloidal mixture is separated by vacuum filtration again, and finally the obtained colloidal precipitate is placed in an oven at 40°C to dry, and finally a rosin-coated stable amorphous calcium carbonate material is obtained.

[0061] The present invention tested the materials described in the above embodiments under a conventional environment (temperature 25 ± 5°C, humidity 50 ± 5%), and the test results are shown in Table 1. The time when ACC stably exists is defined as the number of days when the decrease does not exceed 15% compared with the initial ACC content. The strength is the strength of the cement system obtained when ACC with or without rosin coating is placed outside for 28 days and then replaces cement at a substitution rate of 20% at the age of 28 days.

[0062] Table 1 Test Results of Rosin-Coated Stable Amorphous Calcium Carbonate

[0063]

[0064]

[0065] As can be seen from Table 1, the stable existence time of ACC coated with rosin 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 the gelling ability of ACC, and the strength of the obtained cement system at the age of 28 days is significantly higher.

[0066] The above is the preferred implementation manner of the present invention. Of course, the scope of the rights of the present invention cannot be limited thereby. It should be pointed out that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and changes can be made, and these improvements and changes are also regarded as the protection scope of the present invention.

Claims

1. A preparation method of rosin-coated stable amorphous calcium carbonate, characterized in that, It includes the following steps: (1) Preparation of rosin solvent: Dissolve a certain mass of rosin powder in an alcohol organic solvent to prepare a rosin solvent; (2) Preparation of carbonized regenerated micropowder containing amorphous calcium carbonate: Dissolve a certain mass of polyaspartic acid in water to prepare a polyaspartic acid solution, then add an alcohol organic solvent and mix evenly to obtain a composite solvent. Then add regenerated micropowder to the composite solvent and stir to mix evenly into a suspension. Slowly inject CO2 into the suspension for wet carbonization. After carbonization, perform vacuum filtration separation, washing and drying to obtain carbonized regenerated micropowder micron particles containing amorphous calcium carbonate; (3) Add the carbonized regenerated micropowder micron particles 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 micron particles.

2. The preparation method of the amorphous calcium carbonate stabilized by rosin coating according to claim 1, characterized in that, 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 300-400 cp.

3. The preparation method of the amorphous calcium carbonate stabilized by rosin coating according to 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 10wt%-15wt%, and the mass percentage of the alcohol organic solvent in the composite solvent is 10%-30%.

4. The preparation method of the amorphous calcium carbonate stabilized by rosin coating according to claim 1, characterized in that, In step (2), the regenerated micropowder is obtained by crushing and grinding waste concrete into solid powder with a particle size of 200-2000 mesh, and the solid-liquid ratio of the regenerated micropowder to the composite solvent is 1 g: 20-50 mL.

5. The preparation method of the rosin-coated stable amorphous calcium carbonate according to claim 1, characterized in that, In step (2), the injection flow rate of CO2 gas 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 preparation method of the rosin-coated amorphous calcium carbonate according to claim 1, wherein, In step (3), the solid-liquid ratio of the carbonized regenerated micropowder micron particles containing amorphous calcium carbonate to the rosin solvent is 1 g: 20-50 mL.

7. The preparation method of the rosin-coated 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 preparation method of the rosin-coated amorphous calcium carbonate according to claim 1, characterized in that, In step (3), the stirring speed is 300-500 revolutions per minute, and the total stirring time is 45-60 hours.

9. An amorphous calcium carbonate stabilized by rosin coating, characterized in that, It is prepared by using the preparation method described in any one of claims 1 to 8.

10. Application of an amorphous calcium carbonate stabilized by rosin as described in claim 9 as a gelling material in a cement system.

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