Nano calcium carbonate and liquid-phase synthesis method thereof

Abstract

The invention belongs to the technical field of preparation of inorganic nano materials, and particularly relates to nano calcium carbonate and a liquid-phase synthesis method thereof. The liquid-phase synthesis method of the nano calcium carbonate comprises the steps that an emulsion containing organic carbon amine droplets and an aqueous solution containing calcium ions are subjected to a double decomposition reaction, the particle size of the organic carbon amine droplets in the emulsion containing the organic carbon amine droplets is 100 nm or below, then obtained calcium carbonate slurry is filtered, washed and dried, and the nano calcium carbonate is obtained. By adopting the method provided by the invention, the nano calcium carbonate with nano size, high purity, regular morphology, good dispersity and narrow particle size distribution can be obtained at normal temperature.

Description

Technical Field

[0001] The invention belongs to the technical field of inorganic nano material preparation, and specifically relates to nano calcium carbonate and a liquid phase synthesis method thereof. Background Art

[0002] Nano calcium carbonate has super strong dispersibility and ultra-fine particle structure, which can play a role in strengthening and toughening, reducing product costs and significantly improving quality. Nano calcium carbonate is mainly used in high-end rubber and plastic products, papermaking, silicone adhesive, automobile chassis paint, ink and other industries.

[0003] The particle size and crystal form of nano calcium carbonate are mainly determined by the carbonization process, and the core technology of the carbonization process is the carbonization reaction equipment and process technology. At present, the more mature and industrialized preparation method of nano calcium carbonate is the lime carbonization method. This method calcines selected limestone to obtain calcium oxide and kiln gas; digests calcium oxide, and crushes the resulting suspension calcium hydroxide under high shear force, removes particles and impurities by multi-stage suspension separation, and obtains a refined calcium hydroxide suspension of a certain concentration; then introduces carbon dioxide gas, adds appropriate crystal form control agents, and carbonizes to the end point under freezing and high pressure conditions to obtain calcium carbonate slurry, which is then dehydrated, dried, and surface treated to obtain nano calcium carbonate products. Among them, the carbonization process usually adopts bubbling carbonization, stirring carbonization, spray carbonization or ultra-gravity carbonization. However, the traditional carbonization process has the disadvantages of long carbonization time, high power consumption, low carbon dioxide utilization rate, large product particle size and wide distribution range.

[0004] CN108083312A discloses a carbonization reactor and a method for preparing nano calcium carbonate with small particle size, high dispersibility and low oil absorption value by using the carbonization reactor. The carbonization reactor comprises a liquid film nucleator and a crystal grower, and the nucleation and growth of nano calcium carbonate are carried out step by step. First, a gas distributor is provided in the liquid film nucleator, and carbon dioxide gas is contacted with slurry in the opposite direction, so that the gas-liquid contact is good, so that the calcium hydroxide slurry is fully reacted in the carbonization tower to facilitate the generation of crystal nuclei, and then after aging, secondary carbonization, surface treatment, filter pressing dehydration, drying and crushing, a nano calcium carbonate with a particle size of 20 to 30 nm is obtained. However, in the nucleation reaction involved in the method, the carbon dioxide concentration needs to be as high as 100%, the conditions are relatively harsh, and the reaction process needs secondary carbonization, and the control conditions are many during actual operation, the process is relatively complicated, and the operating cost is high.

[0005] CN102602973A discloses a method for synthesizing ultrafine calcium carbonate using carbide slag, which includes adding ammonium chloride to a carbide slag suspension to extract calcium, filtering out the slag, adding a crystal control agent to the resulting solution of calcium chloride and ammonia water, and then introducing CO2 gas to obtain calcium carbonate. However, in order to ensure that calcium hydroxide and ammonium chloride react completely, ammonia must be continuously evaporated during the reaction process. Wastewater, waste gas, and waste residue in the entire production process are difficult to handle, which seriously pollutes the environment. At the same time, a large amount of Cl adsorbed by calcium in the CaCO3 obtained by carbonization is - It is difficult to remove completely, which seriously affects its application field, and the large amount of NH4Cl entrained affects the purity of the product. In addition, the morphology of the calcium carbonate particles obtained by this method is not uniform enough, the dispersibility is poor, and the particle size distribution is wide.

[0006] CN110755882A discloses an extraction solution for preparing active light calcium carbonate, its use and a method for preparing active light calcium carbonate, which adopts an organic solution extraction and stripping method, uses carbide slag or low-grade Ca(OH)2 as a calcium source, and prepares high-value-added active light calcium carbonate or nano calcium carbonate, and the extractant can be recycled, achieving a new breakthrough different from the traditional method. However, the invention does not report on the method for further preparing nano calcium carbonate. Summary of the invention

[0007] The first purpose of the present invention is to provide a novel method for synthesizing nano calcium carbonate, which has a simple process and can obtain nano calcium carbonate with regular morphology, good dispersibility and narrow particle size distribution.

[0008] Specifically, the liquid phase synthesis method of nano calcium carbonate provided by the present invention comprises subjecting an emulsion containing small organic carbon amine droplets to a double decomposition reaction with an aqueous solution containing calcium ions, wherein the particle size of the small organic carbon amine droplets in the emulsion containing small organic carbon amine droplets is less than 100 nm, and then filtering, washing and drying the obtained calcium carbonate slurry to obtain nano calcium carbonate.

[0009] The second object of the present invention is to provide nano calcium carbonate prepared by the above method.

[0010] The present invention extends and expands on the basis of CN110755882A, and proposes a method for realizing stable and controllable synthesis of nano calcium carbonate. The key of the present invention is to use an emulsion containing small organic carbon amine droplets with a specific particle size as a synthesis and limiting template of nano calcium carbonate, and by controlling the particle size of the small organic carbon amine droplets, nano calcium carbonate with nanometer size, regular morphology, good dispersibility and narrow particle size distribution can be obtained at room temperature, the product quality can be greatly improved, and stable production can be easily achieved in industry, overcoming the defect of unstable product quality caused by factors such as uneven concentration distribution of reactants in the reaction process of conventional carbonization method. In addition, the method provided by the present invention has simple process, low energy consumption, and is easy to achieve industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a scanning electron microscope result of the nano-calcium carbonate obtained in Example 1;

[0012] Figure 2 This is a scanning electron microscope result of the nano-calcium carbonate obtained in Example 4;

[0013] Figure 3 This is the scanning electron microscope result of the nano calcium carbonate obtained in Comparative Example 1. DETAILED DESCRIPTION

[0014] The nano calcium carbonate liquid phase synthesis method provided by the present invention comprises the steps of subjecting an emulsion containing organic carbon amine small droplets to double decomposition reaction with an aqueous solution containing calcium ions, wherein the particle size of the organic carbon amine small droplets in the emulsion containing organic carbon amine small droplets is less than 100 nm, and then filtering, washing and drying the obtained calcium carbonate slurry to obtain nano calcium carbonate.

[0015] In the above-mentioned nano calcium carbonate liquid phase synthesis process, the particle size of the organic carbon amine droplets in the emulsion containing the organic carbon amine droplets is below 100nm, specifically 100nm, 95nm, 90nm, 85nm, 80nm, 75nm, 70nm, 65nm, 60nm, 55nm, 50nm, 45nm, 40nm, 35nm, 30nm, 25nm, 20nm, 15nm, 10nm, 5nm or any value therebetween. The particle size of the organic carbon amine droplets is determined according to the target nano calcium carbonate product. When it is necessary to obtain nano calcium carbonate with a larger particle size, the particle size of the organic carbon amine droplets needs to be increased; when it is necessary to obtain nano calcium carbonate with a smaller particle size, the particle size of the organic carbon amine droplets needs to be reduced.

[0016] The present invention does not limit the source of the emulsion containing small organic carbon amine droplets, as long as the particle size of the small organic carbon amine droplets contained therein is less than 100 nm, it can be commercially available, or prepared according to various existing methods. In a preferred embodiment, the emulsion containing small organic carbon amine droplets is obtained by pre-emulsifying an organic carbon amine solution and water under stirring, and then passing the obtained pre-emulsified liquid into a primary pipeline reactor or a high-speed shearing machine for emulsification. When preparing the emulsion containing small organic carbon amine droplets according to the above preferred method, the particle size of the small organic carbon amine droplets is mainly regulated by controlling the ratio of the organic carbon amine solution and water, as well as the temperature, time and shear force of the pre-emulsification and emulsification.

[0017] In the preparation process of the above-mentioned emulsion containing small organic carbon amine droplets, the concentration of the organic carbon amine solution is preferably 10-50wt%, such as 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt% or any value therebetween. The organic carbon amine solution contains an organic carbon amine and an organic solvent, wherein the organic carbon amine is a substance obtained after the organic amine absorbs carbon dioxide, and the organic solvent can dissolve the organic amine and the organic carbon amine. Among them, the carbon atom number of the organic carbon amine can be C1-C30, preferably C5-C18, specifically C5, C8, C10, C12, C15, C18 or any value therebetween, and is particularly preferably at least one of di-n-butylamine, trioctylamine, dodecylamine, diisooctylamine, isooctylamine, octadecylamine and cyclopentylamine. The organic solvent may be any existing substance capable of dissolving organic amines and organic carbon amines, for example, it may be selected from at least one of alcohol solvents, ether solvents, ester solvents, ketone solvents and acrylate solvents. Among them, the alcohol solvents may include methanol, ethanol, ethylene glycol, n-propanol, isopropanol, octanol, etc. The ether solvents may include ether, propylene oxide, etc., and the ester solvents may include methyl acetate, ethyl acetate, propyl acetate, etc. The ketone solvents may include acetone, methyl butyl ketone, methyl isobutyl ketone, etc. The acrylate solvents may include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, etc.

[0018] In the preparation process of the above-mentioned emulsion containing small organic carbon amine droplets, the mass ratio of the organic carbon amine solution to water is preferably (1-50):1, such as at least one of 1:1, 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, etc.

[0019] In the preparation process of the above-mentioned emulsion containing small organic carbon amine droplets, the pre-emulsification temperature is preferably room temperature, that is, 0-40°C, specifically 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C or any value therebetween.

[0020] In the preparation process of the above-mentioned emulsion containing small organic carbon amine droplets, the emulsification temperature is preferably 0-40°C, specifically 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C or any value therebetween.

[0021] In the preparation process of the above-mentioned emulsion containing organic carbon amine droplets, the conditions of the pre-emulsification and emulsification are preferably such that the particle size of the organic carbon amine droplets in the obtained emulsion containing organic carbon amine droplets is less than 100 nm, and there is no special limitation.

[0022] In the above-mentioned liquid phase synthesis process of nano calcium carbonate, the method of performing a double decomposition reaction on the emulsion containing small organic carbon amine droplets and the aqueous solution containing calcium ions can be directly stirring and mixing the emulsion containing small organic carbon amine droplets and the aqueous solution containing calcium ions and / or ultrasonically mixing them. Preferably, the two streams of the emulsion containing small organic carbon amine droplets and the aqueous solution containing calcium ions are pumped into a secondary pipeline reactor for uniform mixing. At this time, the aqueous solution containing calcium ions can be quickly fused into the small organic carbon amine droplets in the form of small calcium ion droplets under the action of strong impact force, and the oil phase in the small droplets can play an isolation role. The small particles of calcium carbonate formed by the reaction of calcium ions and organic carbon amines in the same small droplets can avoid fusion into large particles of calcium carbonate under the protection of the oil phase. The obtained nano calcium carbonate can be controlled at a nano size with a more regular morphology and a narrower particle size distribution. In addition, the mixing conditions preferably include a temperature of 0 to 80°C, such as 0, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C or any value therebetween; a residence time in the secondary pipeline reactor of more than 10s, such as 10s, 12s, 15s, 18s, 20s, 22s, 25s, 28s, 30s, 32s, 34s, 36s, 38s, 40s, 42s, 44s, 46s, 48s, 50s, 55s, 60s, 65s, 70s, 75s, 80s, etc.; and the reaction is terminated when the calcium ion concentration in the system is reduced to below 2wt%.

[0023] In the above-mentioned nano calcium carbonate liquid phase synthesis process, the concentration of the aqueous solution containing calcium ions is preferably 5-30wt%, such as 5wt%, 8wt%, 10wt%, 12wt%, 15wt%, 18wt%, 20wt%, 22wt%, 24wt%, 26wt%, 28wt%, 30wt% or any value therebetween. The calcium ions in the aqueous solution containing calcium ions are preferably derived from at least one of calcium formate, calcium acetate and calcium propionate. In addition, the molar ratio of calcium ions in the aqueous solution containing calcium ions to organic carbon ammonium is preferably (0.8-1.3):1, such as 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1 or any value therebetween.

[0024] In a preferred embodiment, the reaction device involved in the nano calcium carbonate liquid phase synthesis method includes a pre-reaction disperser, a primary pipeline reactor and a secondary pipeline reactor, and the synthesis process includes: placing an organic carbon amine solution and water in a pre-reaction disperser for mixing to achieve pre-emulsification, passing the obtained pre-emulsion into a primary pipeline reactor for emulsification, obtaining an emulsion containing small organic carbon amine droplets, wherein the particle size of the small organic carbon amine droplets in the emulsion is below 100nm, and then the emulsion and the aqueous solution containing calcium ions are collided and pumped into a secondary pipeline reactor to make the materials uniformly mixed, and then the obtained calcium carbonate slurry is filtered, washed and dried to obtain nano calcium carbonate. The carbonization process of the present invention has high material mixing efficiency, the reaction speed can be greatly improved, the operability is strong, it is easy to achieve continuous production, and the obtained nano calcium carbonate has uniform particle size distribution and stable product quality, which overcomes the disadvantages of the conventional carbonization method in that the concentration of reactants is unevenly distributed during the reaction process and the product quality is unstable. In addition, the present invention can control the formation of a series of nano calcium carbonate products with different nanometer scales and shapes by regulating the particle size of small organic carbamide droplets in the emulsion, thereby realizing customized production according to different market demands.

[0025] In a preferred embodiment, the aqueous solution containing calcium ions is obtained in the following manner: a calcium source solution containing calcium hydroxide is contacted with an extraction solution for reaction, and then the obtained reaction solution is extracted, filtered and stratified to obtain an organic phase solution containing organic amine and organic extraction solvent and an aqueous solution containing calcium ions; the extraction solution contains an organic extraction solvent, an organic amine and a carboxylic acid, the organic extraction solvent is insoluble in water and can dissolve the organic amine, the organic amine is insoluble in water and soluble in the organic extraction solvent, the organic amine acid salt formed by the organic amine and the carboxylic acid is soluble in the organic extraction solvent, and the calcium carboxylate obtained by the reaction of the carboxylic acid and calcium hydroxide is soluble in water but insoluble in the organic extraction solvent. At this time, it is possible to produce high-quality nano calcium carbonate using a low-grade calcium source as a raw material, greatly improving resource utilization and added value. The mass proportion of the organic extraction solvent in the extraction solution is 20-90%, such as 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or any value therebetween. The organic extraction solvent may be selected from at least one of a dispersant, a coupling agent, a plasticizer, a crystal control agent and a solvent having a functional group. The organic amine preferably accounts for 5 to 70% of the mass of the extraction solution, such as 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or any value therebetween. The organic amine is preferably an organic amine of C8 to C24. The carboxylic acid preferably accounts for 3 to 30% of the mass of the extraction solution, such as 3%, 5%, 10%, 15%, 20%, 25%, 30% or any value therebetween. The carboxylic acid is preferably a low-level organic carboxylic acid, and the calcium carboxylate obtained by reacting with calcium hydroxide is easily soluble in water and poorly soluble in an organic extraction solvent.

[0026] In addition, the present invention also provides nano calcium carbonate prepared by the method.

[0027] The present invention will be described in detail below through examples.

[0028] Preparation Example 1 Aqueous solution containing calcium ions and its preparation method

[0029] Take 270g 4-heptanone, 21g dibutylamine, and 9g propionic acid and mix them evenly to prepare an organic extraction solution. Mix the prepared organic extraction solution with carbide slag slurry containing 8% Ca(OH)2 to control the Ca content in the carbide slurry. 2+ The molar ratio of propionic acid to the organic extraction solution is 1:2. After sufficient reaction, the insoluble matter is filtered out and the mixture is allowed to stand for stratification. An organic solution containing dibutylamine and 4-heptanone is obtained as the upper layer, and an aqueous solution containing calcium propionate is obtained as the lower layer.

[0030] Preparation Example 2 Aqueous solution containing calcium ions and its preparation method

[0031] Take 180g of n-octanol, 72g of dodecylamine and 15g of formic acid and mix them evenly to prepare an organic extraction solution. Mix the prepared organic extraction solution with carbide slag slurry containing 10% Ca(OH)2 to control the Ca content in the carbide slurry. 2+ The molar ratio of formic acid to the organic extraction solution is 1:2.2. After sufficient reaction, the insoluble matter is filtered out and the mixture is allowed to stand for stratification. An organic solution containing dodecylamine and n-octanol is obtained in the upper layer, and an aqueous solution containing calcium formate is obtained in the lower layer.

[0032] Preparation Example 3 Aqueous solution containing calcium ions and its preparation method

[0033] Take 50g butyl acrylate, 172g octadecylamine and 25g acetic acid and mix them evenly to prepare an organic extraction solution. Mix the prepared organic extraction solution with lime milk containing 20wt% Ca(OH)2 to control the Ca content in the lime milk. 2+ The molar ratio of acetic acid to the organic extraction solution is 1:2.3. After sufficient reaction, the insoluble matter is filtered out and the mixture is allowed to stand for stratification. An organic solution containing octadecylamine and butyl acrylate is obtained in the upper layer, and an aqueous solution containing calcium acetate is obtained in the lower layer.

[0034] Preparation Example 4 Aqueous solution containing calcium ions and preparation method thereof

[0035] The aqueous solution containing calcium ions was prepared according to the method of Preparation Example 1, except that the organic extraction solution was replaced by pure propionic acid and the Ca 2+ The molar ratio of propionic acid to propionic acid is controlled at 1:2. The specific steps are as follows: mixing propionic acid with carbide slag slurry containing 8% Ca(OH)2, and controlling the Ca(OH)2 content in the carbide slurry. 2+ The molar ratio of calcium propionate to propionic acid is 1:2 to obtain an aqueous solution containing calcium propionate.

[0036] Example 1

[0037] S1. Pre-emulsify a 10% organic carbon amine solution (di-n-butylamine, the organic solvent is octanol) and water at a mass ratio of 50:1 at room temperature to obtain a pre-emulsified liquid;

[0038] S2. The pre-emulsion obtained in step S1 is passed into a primary pipeline reactor, and emulsified under the action of high-speed shear force at room temperature to obtain a solution containing small organic carbon amine droplets, wherein the particle size of the small organic carbon amine droplets is 70 to 80 nm;

[0039] S3. The solution containing small organic carbon amine droplets obtained in step S2 and the aqueous solution containing calcium propionate obtained in preparation example 1 are pumped into a secondary pipeline reactor to mix the materials evenly and fully contact and react. After the reaction is completed, the obtained calcium carbonate slurry is drawn out from the secondary pipeline mixer, and then filtered, washed and dried to obtain nano calcium carbonate. The molar ratio of calcium ion to organic carbon amine is 1.2:1, the secondary pipeline reaction temperature is 25°C, the reaction time is 10s, and the calcium ion concentration in the system is reduced to below 2wt%.

[0040] The content of CaCO3 in the nano calcium carbonate is 97.2%, the particle size D50 is 80nm and D97 is 120nm, the oil absorption value is 28mL / 100mg, and the activation degree is 98%. As can be seen from the above results, the numerical values ​​of particle size D50 and particle size D97 are very close, which can be explained that the particle size distribution of the nano calcium carbonate is narrow. The nano calcium carbonate is obtained by surface modification activation treatment, and the activation degree can reflect the dispersibility. The higher the activation degree, the better the dispersibility. Since the activation degree of the nano calcium carbonate has reached 98%, it can be explained that its dispersibility is good. From the scanning electron microscope picture Figure 1 As shown, from Figure 1 It can be seen that the morphology of the nano-calcium carbonate is regular and spindle-shaped.

[0041] Example 2

[0042] S1. Pre-emulsify a 20% organic carbon amine solution (dodecylamine, the organic solvent is methyl acrylate) and water at a mass ratio of 40:1 at room temperature to obtain a pre-emulsion;

[0043] S2. The pre-emulsion obtained in step S1 is passed into a primary pipeline reactor, and emulsified at 40° C. under the action of high-speed shear force to obtain a solution containing small organic carbon amine droplets, wherein the particle size of the small organic carbon amine droplets is 60 to 70 nm;

[0044] S3. The solution containing small organic carbon amine droplets obtained in step S2 and the aqueous solution containing calcium formate obtained in preparation example 2 are pumped into a secondary pipeline reactor to mix the materials evenly and fully contact and react. After the reaction is completed, the obtained calcium carbonate slurry is drawn out from the secondary pipeline mixer, and then filtered, washed and dried to obtain nano calcium carbonate. The molar ratio of calcium ion to organic carbon amine is 1:1, the secondary pipeline reaction temperature is 40°C, the reaction time is 40s, and the calcium ion concentration in the system is reduced to below 2wt%.

[0045] CaCO3 content is 97.0% in this nano-calcium carbonate, and particle size D50 is 70nm and D97 is 100nm, and oil absorption value is 26mL / 100mg, activation degree 98%. From particle diameter D50 and D97, can illustrate the narrow particle size distribution of this nano-calcium carbonate.Because the activation degree of this nano-calcium carbonate has reached 98%, can illustrate its good dispersibility thus.Can find out from scanning electron microscope figure, the morphology rule of this nano-calcium carbonate is needle-shaped.

[0046] Example 3

[0047] S1. Pre-emulsify a 40% organic carbon amine solution (isooctylamine, the organic solvent is methyl isobutyl ketone) and water at a mass ratio of 10:1 at room temperature to obtain a pre-emulsified liquid;

[0048] S2. The pre-emulsion obtained in step S1 is passed into a primary pipeline reactor, and emulsified at 20° C. under the action of high-speed shear force to obtain a solution containing small organic carbon amine droplets, wherein the particle size of the small organic carbon amine droplets is 90 to 100 nm;

[0049] S3. The solution containing small organic carbon amine droplets obtained in step S2 and the aqueous solution containing calcium acetate obtained in preparation example 3 are pumped into a secondary pipeline reactor to mix the materials evenly and fully contact and react. After the reaction is completed, the obtained calcium carbonate slurry is drawn out from the secondary pipeline mixer, and then filtered, washed and dried to obtain nano calcium carbonate. The molar ratio of calcium ion to organic carbon amine is 0.8:1, the secondary pipeline reaction temperature is 15°C, the reaction time is 45s, and the calcium ion concentration in the system is reduced to less than 2wt%.

[0050] CaCO3 content is 97.3% in this nano-calcium carbonate, and particle size D50 is 90nm and D97 is 130nm, and oil absorption value is 25mL / 100mg, activation degree 98%. From particle diameter D50 and D97, can illustrate the narrow particle size distribution of this nano-calcium carbonate.Because the activation degree of this nano-calcium carbonate has reached 98%, can illustrate its good dispersibility thus.Can find out from scanning electron microscope figure, the morphology rule of this nano-calcium carbonate is chain-shaped.

[0051] Example 4

[0052] S1. Pre-emulsify a 10% organic carbon amine solution (diisooctylamine, the organic solvent is butyl ether) and water at a mass ratio of 20:1 at room temperature to obtain a pre-emulsified liquid;

[0053] S2. The pre-emulsion obtained in step S1 is passed into a primary pipeline reactor, and emulsified at 15° C. under the action of high-speed shear force to obtain a solution containing small organic carbon amine droplets, wherein the particle size of the small organic carbon amine droplets is 50 to 60 nm;

[0054] S3. The solution containing small organic carbon amine droplets obtained in step S2 and the aqueous solution containing calcium propionate obtained in preparation example 1 are pumped into a secondary pipeline reactor to mix the materials evenly and fully contact and react. After the reaction is completed, the obtained calcium carbonate slurry is drawn out from the secondary pipeline mixer, and then filtered, washed and dried to obtain nano calcium carbonate. The molar ratio of calcium ion to organic carbon amine is 1.1:1, the secondary pipeline reaction temperature is 60°C, the reaction time is 50s, and the calcium ion concentration in the system is reduced to below 2wt%.

[0055] The content of CaCO3 in the nano calcium carbonate is 97.5%, the particle size D50 is 60nm and D97 is 90nm, the oil absorption value is 25mL / 100mg, and the activation degree is 98%. The particle size D50 and D97 show that the particle size distribution of the nano calcium carbonate is narrow. Since the activation degree of the nano calcium carbonate has reached 98%, it can be shown that its dispersibility is good. From the scanning electron microscope picture Figure 2 As shown, from Figure 2 It can be seen that the nano calcium carbonate has a regular morphology and is spherical.

[0056] Example 5

[0057] Nano calcium carbonate was prepared according to the method of Example 1, except that the aqueous solution containing calcium propionate obtained in Preparation Example 1 was replaced by the aqueous solution containing calcium propionate obtained in Preparation Example 4 in the same weight portion, and the other conditions were the same as in Example 1 to obtain nano calcium carbonate.

[0058] CaCO3 content is 97.5% in this nano-calcium carbonate, and particle size D50 is 85nm and D97 is 110nm, and oil absorption value is 26mL / 100mg, and activation degree is 97%. From particle diameter D50 and D97, can illustrate the narrow particle size distribution of this nano-calcium carbonate.Because the activation degree of this nano-calcium carbonate has reached 97%, can illustrate its good dispersibility thus.Can find out from scanning electron microscope figure, the morphology regularity of this nano-calcium carbonate is needle-shaped.

[0059] Comparative Example 1

[0060] Nano calcium carbonate was prepared according to the method of Example 1, except that the step of emulsifying in the primary pipeline reactor was not included. Instead, the pre-emulsified liquid obtained in step S1 (the average diameter of the small droplets was 300 nm) and the aqueous solution containing calcium propionate obtained in Preparation Example 1 were directly pumped into the secondary pipeline reactor for reaction. The remaining conditions were the same as those in Example 1 to obtain nano calcium carbonate.

[0061] The content of CaCO3 in the nano calcium carbonate is 98%, the particle size D50 is 300nm and D97 is 950nm, the oil absorption value is 25mL / 100mg, and the activation degree is above 98%. The numerical difference between the particle size D50 and D97 is large, which can be explained that the particle size distribution of the nano calcium carbonate is wide. Since the activation degree of the nano calcium carbonate has reached 98%, it can be explained that its dispersibility is good. From the scanning electron microscope Figure 3 It can be seen that the morphology of the nano calcium carbonate is irregular spherical. In comparison, the morphology of the nano calcium carbonate in Example 1 is more regular.

[0062] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention.

Claims

1. A nano calcium carbonate liquid phase synthesis method, characterized in that, The method comprises subjecting an emulsion containing organic carbon amine small droplets to double decomposition reaction with an aqueous solution containing calcium ions, wherein the particle size of the organic carbon amine small droplets in the emulsion containing organic carbon amine small droplets is below 100 nm, and then filtering, washing and drying the obtained calcium carbonate slurry to obtain nano calcium carbonate.

2. Nano calcium carbonate liquid phase synthesis method according to claim 1, is characterized in that, The emulsion containing small organic carbon amine droplets is obtained by pre-emulsifying an organic carbon amine solution and water under stirring conditions, and then passing the obtained pre-emulsion into a primary pipeline reactor or a high-speed shearing machine for emulsification.

3. nano calcium carbonate liquid phase synthesis method according to claim 2, is characterized in that, The mass ratio of the organic carbon amine solution to water is (1-50):1; Preferably, the concentration of the organic carbon amine solution is 10 to 50 wt%; Preferably, the organic carbon amine solution contains an organic carbon amine and an organic solvent, wherein the organic carbon amine is a substance obtained by absorbing carbon dioxide from an organic amine, and the organic solvent can dissolve the organic amine and the organic carbon amine; Preferably, the organic amine has a carbon number of C5 to C18, and is preferably at least one selected from di-n-butylamine, trioctylamine, dodecylamine, diisooctylamine, isooctylamine, octadecylamine and cyclopentylamine; Preferably, the organic solvent is selected from at least one of alcohol solvents, ether solvents, ester solvents, ketone solvents and acrylic ester solvents.

4. nano calcium carbonate liquid phase synthesis method according to claim 2, is characterized in that, The temperatures of the pre-emulsification and emulsification are independently 0 to 40° C., and the time of the pre-emulsification and emulsification is based on the particle size of the organic carbon amine droplets in the obtained emulsion containing organic carbon amine droplets being below 100 nm.

5. Nano calcium carbonate liquid phase synthesis method according to claim 1, is characterized in that, The double decomposition reaction is carried out by pumping two streams of an emulsion containing small organic carbon amine droplets and an aqueous solution containing calcium ions into a secondary pipeline reactor for uniform mixing.

6. Nano calcium carbonate liquid phase synthesis method according to claim 5, is characterized in that, The mixing conditions include a temperature of 0 to 80° C., a residence time in the secondary pipeline reactor of more than 10 seconds, and the reaction is terminated when the calcium ion concentration in the system decreases to less than 2 wt %.

7. The method for synthesizing nano calcium carbonate in liquid phase according to any one of claims 1 to 6, characterized in that: The concentration of the aqueous solution containing calcium ions is 5 to 30 wt %; Preferably, the calcium ions in the aqueous solution containing calcium ions are derived from at least one of calcium formate, calcium acetate and calcium propionate; Preferably, the molar ratio of calcium ions to organic ammonium carbonate in the calcium ion-containing aqueous solution is (0.8-1.3):

1.

8. The method for synthesizing nano calcium carbonate in liquid phase according to any one of claims 1 to 6, characterized in that: The aqueous solution containing calcium ions is obtained in the following manner: a calcium source solution containing calcium hydroxide is contacted with an extraction solution for reaction, and then the obtained reaction solution is extracted, filtered and allowed to stand for stratification to obtain an organic phase solution containing an organic amine and an organic extraction solvent and an aqueous solution containing calcium ions; the extraction solution contains an organic extraction solvent, an organic amine and a carboxylic acid, the organic extraction solvent is insoluble in water but can dissolve the organic amine, the organic amine is insoluble in water but soluble in the organic extraction solvent, the organic amine acid salt formed by the organic amine and the carboxylic acid is soluble in the organic extraction solvent, and the calcium carboxylate obtained by the reaction of the carboxylic acid and calcium hydroxide is soluble in water but insoluble in the organic extraction solvent.

9. Nano calcium carbonate liquid phase synthesis method according to claim 8, is characterized in that, The mass proportion of the organic extraction solvent in the extraction solution is 20 to 90%; Preferably, the organic extraction solvent is selected from at least one of a dispersant, a coupling agent, a plasticizer, a crystal form control agent and a solvent having a functional group; Preferably, the organic amine accounts for 5 to 70% of the mass of the extraction solution; Preferably, the carboxylic acid accounts for 3-30% by mass of the extraction solution.

10. Nano calcium carbonate prepared by the method according to any one of claims 1 to 9.

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