Preparation method of high-dispersion and high-activity nano calcium carbonate

Abstract

The invention discloses a preparation method of high-dispersion and high-activity nano calcium carbonate, which comprises the following steps: optimizing the mixing ratio and aging conditions of quicklime and water, carbonizing by using a specific crystal form control agent, regulating the growth path of calcium carbonate crystals, stirring at a high speed by using a dispersing agent before activation, and performing high-dispersion and high-activity nano calcium carbonate preparation. In the activation stage, an ultrasonic technology is used for assisting, sodium polyphosphate, calcium stearate, fatty alcohol-polyoxyethylene ether and a polysorbate compound active agent are used for modification, and through the combined action of electrostatic stabilization and organic compatibility strengthening, the absolute value of Zeta potential is increased, the steric hindrance effect is provided, particles are further prevented from approaching, and the particle size is reduced. The dispersity and activity of the nano calcium carbonate are remarkably improved, and a nano-scale product with the particle size of 80 nm and the BET value of 25-30 m < 2 > / g is finally obtained. By accurately controlling the temperature, the additive and the mass transfer condition, the problems of agglomeration and non-uniform particle size distribution in a traditional method are solved, and an efficient path is provided for industrial production of the high-performance inorganic filler.

Description

Technical Field

[0001] The invention belongs to the technical field of inorganic chemical industry, and in particular relates to a method for preparing highly dispersed and highly active nano calcium carbonate. Background Art

[0002] Calcium carbonate is an important inorganic chemical filler that is non-toxic, pollution-free, high in purity and low in price, making it widely used in plastics, coatings, rubber, papermaking, medical treatment, inks and other fields.

[0003] Heavy calcium carbonate particles have irregular morphology and high oil absorption before modification. Their surface is hydrophilic and oleophobic, and they are highly polar. They cannot chemically crosslink with high-molecular-weight organic materials such as rubber and plastic, and are prone to particle agglomeration. A single surface modifier has insufficient coating density and poor environmental adaptability. Since the surface energy is not sufficiently reduced, nano-calcium carbonate tends to reagglomerate after modification. The preparation of highly dispersible and highly active nano-calcium carbonate has long been a research hotspot for the preparation and application of nano-calcium carbonate, and is also a bottleneck and technical key that must be overcome for nano-calcium carbonate to achieve its nano-effect. Summary of the Invention

[0004] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0005] In view of the above-mentioned problems and / or the problems existing in the prior art, the present invention is proposed. This method uses a crystal form control agent, performs secondary carbonization, adds a dispersant, and adds a compounded surface modifier using ultrasonic technology to surface treat nano-calcium carbonate, thereby improving the dispersibility and activity of the nano-calcium carbonate and enhancing its compatibility in polymers.

[0006] Therefore, the object of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing highly dispersed and highly active nano-calcium carbonate.

[0007] In order to solve the above technical problems, the present invention provides the following technical solution: a method for preparing highly dispersed and highly active nano calcium carbonate, characterized by comprising:

[0008] Mix quicklime and boiling water in a mass ratio of 1:7-10, stir, sieve, and age for 12-24 hours to prepare calcium hydroxide slurry;

[0009] Add a crystal form control agent, introduce CO2 / N2 gas to carry out carbonization reaction, stop introducing gas when the pH reaches 6.8-7, and obtain a calcium carbonate suspension, which is then aged for 24-48 hours;

[0010] The aged calcium carbonate suspension is subjected to secondary carbonization to a pH of 7, a dispersant is added to the calcium carbonate suspension and stirred at high speed for 1 to 2 hours, then the temperature is raised to 65°C, a composite surface modifier is added to assist in ultrasonic modification, and the suspension is filtered, dried, crushed, and sieved to obtain highly dispersed and highly active nano-calcium carbonate.

[0011] As a preferred embodiment of the preparation method of the present invention, the calcium hydroxide slurry is carbonized, wherein the carbonization temperature is 15 to 45° C., and the crystal form control agent is one or more of citric acid, sucrose, glucose, sulfuric acid, zinc sulfate, and chitosan, and its mass is 0.01 to 0.5 mt% of the mass of the calcium hydroxide slurry.

[0012] As a preferred embodiment of the preparation method of the present invention, the CO2 / N2 gas flow ratio is 1:3.

[0013] As a preferred embodiment of the preparation method of the present invention, the dispersant is at least one of polyethylene glycol, polyvinyl pyrrolidone, polycarboxylate and polyacrylamide, and the mass of the dispersant is 0.1-0.6% of the mass of the dry basis of calcium carbonate.

[0014] As a preferred embodiment of the preparation method of the present invention, the composite surface modifier is composed of calcium stearate, sodium polyphosphate, fatty alcohol polyoxyethylene ether, and polysorbate, and the mass of the modifier is 1-4% of the dry mass of calcium carbonate.

[0015] As a preferred embodiment of the preparation method of the present invention, the power of the auxiliary ultrasound is 200-300W.

[0016] Another object of the present invention is to overcome the deficiencies in the prior art and provide a highly dispersed and highly active nano calcium carbonate, characterized in that: the BET of the nano calcium carbonate is 25 to 30 m 2 / g, and the average particle size is 80nm.

[0017] Beneficial effects of the present invention:

[0018] (1) During the carbonization process, the morphology of nano-calcium carbonate can be regularized by using a crystal control agent, and its compatibility with organic polymers can be improved. By adding a dispersant and ultrasonic technology, the dispersibility of nano-calcium carbonate can be improved from both physical and chemical aspects. Adding a dispersant for pretreatment before surface treatment changes the interaction force between nano-calcium carbonate particles, enhances the repulsive force, and improves the utilization effect of the surface treatment agent during surface treatment.

[0019] (2) The polyphosphate ions after ionization of sodium polyphosphate are adsorbed on the surface of nano-calcium carbonate, significantly increasing the negative charge density on the particle surface, increasing the absolute value of the Zeta potential, enhancing the double-layer repulsion, and effectively preventing the agglomeration of nanoparticles; calcium stearate stretches in non-polar media, providing a steric hindrance effect, further preventing the particles from approaching, and is a conventional treatment agent for nano-calcium carbonate, which plays a role in reducing the cost of the treatment agent; fatty acid polyoxyethylene ether and polysorbate are non-ionic surfactants that are liquid at room temperature, have good dispersibility, and are compatible with other types of surfactants. Due to the synergistic effect between the treatment agents of each component, coupled with the pretreatment of the dispersant and the assistance of ultrasonic technology, the dispersibility and activity of nano-calcium carbonate are greatly improved.

[0020] (3) The nano calcium carbonate prepared by the present invention has the characteristics of simple process, cost saving, high dispersion and high activity. The prepared nano calcium carbonate has a BET of 25-30m 2 / g, and the average particle size is 80nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0022] Figure 1 This is a SEM image of nano-calcium carbonate prepared in Example 1 of the present invention.

[0023] Figure 2 This is a TEM image of nano-calcium carbonate prepared in Example 1 of the present invention.

[0024] Figure 3 This is a water contact angle diagram of nano-calcium carbonate prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0025] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0026] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0027] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0028] Unless otherwise specified, the reagents used in the present invention are commercially available.

[0029] Instruments used in the examples of the present invention: BSD-660 specific surface area analyzer; Bettersize 2600 laser particle size distribution analyzer.

[0030] Performance testing method used in the present invention:

[0031] (1) Activation degree: The activation degree of activated calcium carbonate was tested according to GB / T 19281-2003 “Analysis method of calcium carbonate”, i.e., the hydrophobicity of activated calcium carbonate was used to characterize the activation degree by calculating the proportion of activated calcium carbonate floating on the water surface.

[0032] (2) Contact angle test: Activated calcium carbonate was tested using a contact angle meter. The samples were pressed into tablets using a powder tablet press before testing. The contact angle of each sample was tested three times in parallel and the average value was taken.

[0033] (3) Oil absorption value detection: The oil absorption value is determined according to method 3.20 in GB / T19281-2014 "Analysis method of calcium carbonate".

[0034] (4) BET test: Weigh 0.05g to 0.50g of sample to the nearest 0.0001g and measure according to the method specified in GB / T19587.

[0035] Example 1

[0036] Quicklime and boiling water were mixed in a mass ratio of 1:8, stirred for 1 hour, passed through a 200-mesh sieve, and aged for 24 hours to prepare a calcium hydroxide slurry;

[0037] Add sucrose, a crystal form control agent, at a mass of 0.5 mt% based on the mass of the calcium hydroxide slurry, introduce CO2 / N2 gas to carry out carbonization reaction at 28°C, with a CO2 / N2 gas flow ratio of 1:3, and stop introducing gas when the reaction reaches a pH of 6.8-7 to obtain a calcium carbonate suspension, which is then aged for 24 hours;

[0038] The aged calcium carbonate suspension was subjected to secondary carbonization to a pH of 7. A dispersant, polycarboxylate, was added to the suspension, stirring at high speed for 2 hours. The suspension was then heated to 65°C and modified with an ultrasonic-assisted composite surface modifier, 4% of the dry calcium carbonate mass. The mass ratio of calcium stearate, sodium polyphosphate, and fatty alcohol polyoxyethylene ether was 3:1:1. The suspension was filtered, dried, crushed, and sieved to produce highly dispersed and active nano-calcium carbonate.

[0039] In this embodiment, adding a dispersant pretreatment after the secondary carbonization can reduce the agglomeration of calcium carbonate and improve the dispersibility. The compound active agent assists the ultrasonic technology to increase the dispersibility and activity of nano calcium carbonate. Figure 1 The SEM image of the nano calcium carbonate prepared in this embodiment is: Figure 2 This is a TEM image of the nano-calcium carbonate prepared in this embodiment. It can be seen that the prepared nano-calcium carbonate has good dispersibility.

[0040] Figure 3 This is a water contact angle diagram of the nano-calcium carbonate prepared in this example. The contact angle was tested to be 131.34°.

[0041] Example 2

[0042] Quicklime and boiling water were mixed in a mass ratio of 1:10, stirred for 0.5 h, passed through a 200-mesh sieve, and aged for 12 h to prepare a calcium hydroxide slurry;

[0043] Adding a crystal form control agent, citric acid, at a mass of 0.1 mt% based on the mass of the calcium hydroxide slurry, introducing CO2 / N2 gas to carry out a carbonization reaction at 20°C, with a CO2 / N2 gas flow ratio of 1:3. When the reaction reaches a pH of 6.8-7, the introduction of gas is stopped to obtain a calcium carbonate suspension, and the calcium carbonate suspension is aged for 48 hours;

[0044] The aged calcium carbonate suspension was subjected to secondary carbonization to a pH of 7. Polyvinylpyrrolidone (0.1% by weight of the dry calcium carbonate) was then added to the suspension, followed by high-speed stirring for 1 hour. The suspension was then heated to 65°C and modified using ultrasonic technology using a composite surface modifier (2.5% by weight of the dry calcium carbonate). The mixture was then prepared using a 2:1:2 mass ratio of calcium stearate, sodium polyphosphate, and polysorbate. The mixture was then filtered, dried, crushed, and sieved to produce highly dispersed and active nano-calcium carbonate.

[0045] Example 3

[0046] Quicklime and boiling water were mixed in a mass ratio of 1:10, stirred for 0.5 h, passed through a 200-mesh sieve, and aged for 24 h to prepare a calcium hydroxide slurry;

[0047] Add sucrose, a crystal form control agent, at a mass of 0.1 mt% based on the mass of the calcium hydroxide slurry, introduce CO2 / N2 gas to carry out carbonization reaction at 35°C, with a CO2 / N2 gas flow ratio of 1:3, and stop introducing gas when the reaction reaches a pH of 6.8-7 to obtain a calcium carbonate suspension, which is then aged for 36 hours;

[0048] The aged calcium carbonate suspension was subjected to secondary carbonization to a pH of 7. A dispersant, polyethylene glycol, was added to the suspension, stirring at high speed for 1 hour. The suspension was then heated to 65°C and modified using ultrasonic technology using a composite surface modifier, with the composite modifier accounting for 3.5% of the dry calcium carbonate mass. The mixture was then filtered, dried, crushed, and sieved to produce highly dispersed and active nano-calcium carbonate.

[0049] Example 4

[0050] Quicklime and boiling water were mixed in a mass ratio of 1:9, stirred for 1 hour, passed through a 200-mesh sieve, and aged for 18 hours to prepare a calcium hydroxide slurry;

[0051] Sulfuric acid, a crystal form control agent, was added at a mass of 0.05 mt% based on the mass of the calcium hydroxide slurry, and CO2 / N2 gas was introduced to carry out a carbonization reaction at 35°C with a CO2 / N2 gas flow ratio of 1:3. The introduction of gas was stopped when the pH reached 6.8-7 to obtain a calcium carbonate suspension, and the calcium carbonate suspension was aged for 24 hours;

[0052] An aged calcium carbonate suspension is subjected to secondary carbonization to a pH of 7. A dispersant, polycarboxylate, is added to the suspension, stirring at high speed for 1 hour. The suspension is then heated to 65°C and modified using ultrasonic technology using a composite surface modifier, with the composite modifier accounting for 3% of the dry calcium carbonate mass. The mass ratio of calcium stearate, sodium polyphosphate, and fatty alcohol polyoxyethylene ether is 2:2:1. The suspension is then filtered, dried, crushed, and sieved to produce highly dispersed and active nano-calcium carbonate.

[0053] Example 5

[0054] Quicklime and boiling water were mixed in a mass ratio of 1:8, stirred for 1 hour, passed through a 200-mesh sieve, and aged for 18 hours to prepare a calcium hydroxide slurry;

[0055] Adding a crystal form control agent chitosan at a mass of 0.05 mt% based on the mass of the calcium hydroxide slurry, introducing CO2 / N2 gas to carry out a carbonization reaction at 35°C, with a CO2 / N2 gas flow ratio of 1:3. When the reaction reaches a pH of 6.8-7, the introduction of gas is stopped to obtain a calcium carbonate suspension, and the calcium carbonate suspension is aged for 36 hours;

[0056] The aged calcium carbonate suspension was subjected to secondary carbonization to a pH of 7. A dispersant, sodium polycarboxylate, was added to the suspension, stirring at high speed for 1 hour. The suspension was then heated to 65°C and modified with an ultrasonic-assisted composite surface modifier, 4% of the dry calcium carbonate mass. The mass ratio of calcium stearate, sodium polyphosphate, and polysorbate was 1:2:2. The suspension was filtered, dried, crushed, and sieved to produce highly dispersed and active nano-calcium carbonate.

[0057] Example 6

[0058] Quicklime and boiling water were mixed in a mass ratio of 1:10, stirred for 0.5 h, passed through a 200-mesh sieve, and aged for 24 h to prepare a calcium hydroxide slurry;

[0059] Sulfuric acid, a crystal form control agent, was added at a mass of 0.1 mt% based on the mass of the calcium hydroxide slurry, and CO2 / N2 gas was introduced to carry out a carbonization reaction at 40°C with a CO2 / N2 gas flow ratio of 1:3. The introduction of gas was stopped when the pH reached 6.8-7 to obtain a calcium carbonate suspension, and the calcium carbonate suspension was aged for 36 hours;

[0060] The aged calcium carbonate suspension was subjected to secondary carbonization to a pH of 7. Polyethylene glycol (0.1% of the dry weight of the calcium carbonate) was then added to the suspension and stirred at high speed for 1 hour. The suspension was then heated to 65°C and modified with an ultrasonic-assisted composite surface modifier (3% of the dry weight of the calcium carbonate). The composite modifier was added in a mass ratio of 2:1:2 to calcium stearate, sodium polyphosphate, and polysorbate. The suspension was then filtered, dried, crushed, and sieved to produce highly dispersed and active nano-calcium carbonate.

[0061] Comparative Example 1

[0062] Quicklime and boiling water were mixed in a mass ratio of 1:8, stirred for 1 hour, passed through a 200-mesh sieve, and aged for 24 hours to prepare a calcium hydroxide slurry;

[0063] Add sucrose, a crystal form control agent, at a mass of 0.5 mt% based on the mass of the calcium hydroxide slurry, introduce CO2 / N2 gas to carry out carbonization reaction at 28°C, with a CO2 / N2 gas flow ratio of 1:3, and stop introducing gas when the reaction reaches a pH of 6.8-7 to obtain a calcium carbonate suspension, which is then aged for 24 hours;

[0064] The aged calcium carbonate suspension was subjected to secondary carbonization to a pH of 7. A dispersant, polycarboxylate, was added to the suspension, stirring at high speed for 2 hours. The suspension was then heated to 65°C and modified with an ultrasonic-assisted composite surface modifier, 4% of the dry calcium carbonate mass. The composite modifier was added in a 3:1:1 mass ratio of calcium stearate, sodium polyphosphate, and alkyltrimethylammonium chloride. The suspension was then filtered, dried, crushed, and sieved to produce highly dispersed and active nano-calcium carbonate.

[0065] Comparative Example 2

[0066] Quicklime and boiling water were mixed in a mass ratio of 1:10, stirred for 0.5 h, passed through a 200-mesh sieve, and aged for 12 h to prepare a calcium hydroxide slurry;

[0067] Add sucrose, a crystal form control agent, at a mass of 0.5 mt% based on the mass of the calcium hydroxide slurry, introduce CO2 / N2 gas to carry out carbonization reaction at 28°C, with a CO2 / N2 gas flow ratio of 1:3, and stop introducing gas when the reaction reaches a pH of 6.8-7 to obtain a calcium carbonate suspension, which is then aged for 24 hours;

[0068] The aged calcium carbonate suspension was subjected to secondary carbonization to a pH of 7. Ethanol (0.3% by weight of the dry calcium carbonate basis) was then added to the suspension and stirred at high speed for 2 hours. The suspension was then heated to 65°C and modified with a composite surface modifier (4% by weight of the dry calcium carbonate basis). The surface modifier was then added in a 3:1:1 weight ratio of calcium stearate, sodium polyphosphate, and fatty alcohol polyoxyethylene ether. The suspension was then filtered, dried, crushed, and sieved to produce highly dispersed and active nano-calcium carbonate.

[0069] Table 1

[0070] Experiment number <![CDATA[BETm 2 / g]]> Activation contact angle Example 1 29.8293 99.99％ 131.34° Example 2 30.5020 99.51％ 130.25° Example 3 35.3959 99.76％ 125.08° Example 4 32.0636 99.87％ 128.30° Example 5 33.6841 98.94％ 124.33° Example 6 34.7293 99.25％ 122.59° Comparative Example 1 36.4808 98.93％ 119.84° Comparative Example 2 35.8293 97.25％ 123.25°

[0071] The active nano-calcium carbonate powders prepared in the examples and comparative examples were subjected to performance testing. The results are shown in Table 1. In Table 1, the activity can reach 99.99%, and the water contact angle is above 130°. However, in Comparative Example 1, a quaternary ammonium salt cationic surfactant is used during the secondary surface treatment. In comparison, its activity and water contact angle are not as good as those in Example 1. Comparative Example 2 is dispersed in ethanol without ultrasound assistance, and its activation and contact angle are obviously not as good as those after stirring with a dispersant.

[0072] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, and all of these should be included in the scope of the present invention.

Claims

1. A method for preparing highly dispersed and highly active nano-calcium carbonate, characterized in that: include, Mix quicklime and boiling water in a mass ratio of 1:7-10, stir, sieve, and age for 12-24 hours to prepare calcium hydroxide slurry; Add a crystal form control agent, introduce CO2 / N2 gas to carry out carbonization reaction, stop introducing gas when the pH reaches 6.8-7, and obtain a calcium carbonate suspension, which is then aged for 24-48 hours; The aged calcium carbonate suspension is subjected to secondary carbonization to a pH of 7, a dispersant is added to the calcium carbonate suspension and stirred at high speed for 1 to 2 hours, then the temperature is raised to 65°C, a composite surface modifier is added to assist in ultrasonic modification, and the suspension is filtered, dried, crushed, and sieved to obtain highly dispersed and highly active nano-calcium carbonate.

2. The preparation method according to claim 1, wherein: The calcium hydroxide slurry is carbonized, wherein the carbonization temperature is 15-45°C.

3. The preparation method according to claim 1, wherein: The crystal form control agent is one or more of citric acid, sucrose, glucose, sulfuric acid, zinc sulfate, and chitosan, and its mass accounts for 0.01 to 0.5 mt% of the mass of the calcium hydroxide slurry.

4. The preparation method according to claim 1, wherein: The CO2 / N2 gas flow ratio is 1:

3.

5. The preparation method according to claim 1, wherein: The dispersant is at least one of polyethylene glycol, polyvinyl pyrrolidone, polycarboxylate and polyacrylamide, and the mass of the dispersant is 0.1-0.6% of the mass of the dry basis of calcium carbonate.

6. The preparation method according to claim 1, wherein: The compound surface modifier consists of calcium stearate, sodium polyphosphate, fatty alcohol polyoxyethylene ether and polysorbate, and the mass of the modifier is 1-4% of the mass of the dry basis of calcium carbonate.

7. The preparation method according to claim 1, wherein: The power of the auxiliary ultrasound is 200-300W.

8. The highly dispersed and highly active nano-calcium carbonate prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The BET of the nano calcium carbonate is 25 to 30 m 2 / g, and the average particle size is 80nm.

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