CN113461042A

CN113461042A - Optimization method of modification process of nano calcium carbonate

Info

Publication number: CN113461042A
Application number: CN202110817499.5A
Authority: CN
Inventors: 杨保俊; 涂新悦; 陈小龙; 王百年
Original assignee: Hefei University of Technology
Current assignee: Hefei University of Technology
Priority date: 2021-07-19
Filing date: 2021-07-19
Publication date: 2021-10-01

Abstract

The invention discloses a method for optimizing a modification process of nano calcium carbonate, which comprises the following steps: step 100, heating deionized water to 60 ℃, keeping the temperature, adding CaO powder into the deionized water, stirring and reacting, and then aging the reaction solution to obtain a calcium hydroxide solution; step 200, adding a calcium hydroxide solution and D-sodium gluconate into a carbonization chamber to perform carbonization reaction to prepare a carbonized mixture; step 300, sequentially carrying out suction filtration and washing on the carbonized mixture to obtain a calcium carbonate filter cake, adding deionized water, and pulping to obtain a calcium carbonate suspension; step 400, adding calcium carbonate suspension and sodium dodecyl sulfate into a modification chamber to perform modification reaction to prepare a modified mixture; and 500, sequentially carrying out suction filtration, drying at 60-80 ℃ and screening by a sieve of 90-110 meshes on the modified mixture to obtain the modified calcium carbonate. The invention optimizes the modification process condition and reduces the oil absorption value of the nano calcium carbonate under the condition of reducing the diameter of calcium carbonate particles.

Description

Optimization method of modification process of nano calcium carbonate

Technical Field

The invention relates to the technical field of calcium carbonate, in particular to a method for optimizing a modification process of nano calcium carbonate.

Background

Calcium carbonate is an important inorganic powder product, and can be used as an additive, a reinforcing agent and a whitening agent to be widely applied to the industrial departments of coating, printing ink, papermaking, rubber, plastics and the like. The nano calcium carbonate is ultrafine powder calcium carbonate with the particle size within 100nm, and has quantum size effect, small size effect, surface effect and macroscopic quantum effect. An important parameter determining the application performance of the nano calcium carbonate particles is the particle morphology. Many scholars at home and abroad begin to research the control preparation of the shape of the nano calcium carbonate, including optimizing process conditions, improving production equipment, adding a crystal form control agent and the like. The method for changing the crystallization behavior of the nano calcium carbonate by adding the crystal form control agent is favored, and the nano calcium carbonate product successfully prepared by the method has the shape of a cube, a needle, a chain lock, a sphere and the like. Although certain achievements are achieved in the research of controlling the morphology of calcium carbonate by a crystal form control agent in China, problems still exist, such as harsh production conditions, large additive dosage, low product purity, large particle size, uneven morphology, serious agglomeration and the like.

At present, few reports are provided for preparing spherical calcium carbonate by taking saccharides as a crystal form control agent, a writer controls reaction conditions by adding D-sodium gluconate as the crystal form control agent to prepare spheroidal nano calcium carbonate, and the influence of the reaction conditions on the morphology and the particle size of the nano calcium carbonate is discussed. The oil absorption of the nano calcium carbonate is an important reference index for judging the affinity of the particles and organic matters, and is another important factor influencing the practical application performance of the nano calcium carbonate besides the morphology of the nano calcium carbonate. The unmodified nano calcium carbonate particles have high surface energy, are in a thermodynamic unstable state and are easy to aggregate into clusters; the particle surface is hydrophilic and oleophobic, the particles are difficult to be uniformly dispersed in an organic medium, the bonding force between the particles and the high polymer is weak, and interface defects are easily caused, so that certain properties of the high polymer are reduced. Therefore, the surface modification treatment of the nano calcium carbonate reduces the surface potential energy of the nano calcium carbonate and increases the oleophylic hydrophobicity, thereby having certain practical significance. The common modification methods of the nano calcium carbonate comprise 2 types of dry modification and wet modification. The dry modification process is simple, but the modification effect is poor, and the commonly used modifiers comprise titanate coupling agents, phosphate coupling agents and the like. The wet modification process is relatively complex, but the modification effect is good. Commonly used modifiers are fatty acids (salts), phosphate esters, sulfonates, quaternary ammonium salts, inorganic substances, etc.

In the prior art, the oil absorption value of calcium carbonate is related to the particle size and also to the crystal form of the particles. And the oil absorption value directly influences the application of calcium carbonate in plastics. If the oil absorption value of the calcium carbonate is higher, the absorption amount of the plasticizer by the calcium carbonate is also large, so that the processability of the plastic is poor, and on the contrary, the oil absorption value of the calcium carbonate is small, the absorption amount of the plasticizer is also small, the influence on the processability of the plastic is less, the plastic product has certain requirements on the oil absorption value of the calcium carbonate, and the heavy calcium carbonate is generally selected in application, but when the heavy calcium carbonate is filled into the plastic, the dispersibility is poor, so that the filling effect is poor.

Disclosure of Invention

The invention aims to provide a method for optimizing a modification process of nano calcium carbonate, which aims to solve the technical problem of high oil absorption caused by light calcium carbonate in the prior art.

In order to solve the technical problems, the invention specifically provides the following technical scheme:

a method for optimizing a modification process of nano calcium carbonate comprises the following steps:

step 100, heating deionized water to 60 ℃, keeping the temperature, adding CaO powder into the deionized water, stirring and reacting, and then aging the reaction solution to obtain a calcium hydroxide solution;

step 200, adding a calcium hydroxide solution and D-sodium gluconate into a carbonization chamber to perform carbonization reaction to prepare a carbonized mixture;

step 300, sequentially carrying out suction filtration and washing on the carbonized mixture to obtain a calcium carbonate filter cake, adding deionized water, and pulping to obtain a calcium carbonate suspension;

step 400, adding calcium carbonate suspension and sodium dodecyl sulfate into a modification chamber to perform modification reaction to prepare a modified mixture;

and 500, sequentially carrying out suction filtration, drying at 60-80 ℃ and screening by a sieve of 90-110 meshes on the modified mixture to obtain the modified calcium carbonate.

As a preferred embodiment of the present invention, the carbonization method of step 200 comprises:

step 201, adding 7-9% of calcium hydroxide solution into a carbonization chamber, heating the solution in the carbonization chamber to 50-60 ℃ through water bath heating, and stirring the solution in the carbonization chamber at the speed of 700-;

202, adding 1-2% by mass of D-sodium gluconate into the solution, passing carbon dioxide gas into the solution, and controlling the flow rate of the carbon dioxide gas to be 60-80 mL/min;

and step 203, stopping introducing the carbon dioxide gas until the pH value of the calcium hydroxide solution reaches 7 so as to complete the carbonization reaction.

As a preferred embodiment of the present invention, the specific method for modification in step 400 includes:

step 401, adding 7-9% by mass of calcium carbonate suspension and 3-4% by mass of sodium dodecyl sulfate into a modification chamber;

step 402, heating the liquid in the modification chamber in a water bath at 60-80 ℃;

and 403, keeping the mixture in the modification chamber at a constant temperature of 60-80 ℃, simultaneously stirring the mixture in the modification chamber in a non-mechanical manner, and finishing the modification process after 40-70 min.

As a preferable embodiment of the present invention, the non-mechanical stirring method in step 403 includes:

4031, stirring a gas-liquid interface in the modification chamber through a second stirring piece in the modification chamber to form a transverse stirring flow at the gas-liquid interface;

4032, the mixture at the bottom of the modification chamber is extracted by the non-contact driving part in the modification chamber and sprayed upwards to form a longitudinal stirring flow in the liquid.

As a preferable scheme of the present invention, the non-contact driving component includes a circulation cavity tube and an air pumping device, one end of the circulation cavity tube is connected to the top end of the modification chamber, a high pressure air cavity is arranged at the bottom end of the circulation cavity tube, the high pressure air cavity is communicated and mounted at the bottom end of the modification chamber, the air pumping device is mounted in the circulation cavity tube, and the air pumping device can pump air at the top end of the modification chamber to the high pressure air cavity;

the bottom end of the modification chamber is provided with a spraying assembly, the spraying assembly is positioned above the high-pressure air cavity, the spraying assembly can spray airflow to the modification chamber under the driving of the gas in the high-pressure air cavity, and the spraying assembly can prevent the liquid in the modification chamber from flowing back to the high-pressure air cavity;

the high-pressure air cavity is communicated with the other end of the circulating cavity tube through a through tube, the air extractor is arranged at one end of the through tube close to the high-pressure air cavity, and the other end of the through tube is fixedly provided with a one-way valve.

As a preferable scheme of the invention, the spraying assembly comprises a U-shaped cavity tube fixedly mounted on the modification chamber, a spraying cavity tube is arranged above the U-shaped cavity tube, the spraying cavity tube is mounted on a symmetrical axis of the U-shaped cavity tube in a communicating manner, a storage tank is arranged at the bottom end of the U-shaped cavity tube, at least two air injection channels are mounted on the side wall of the storage tank, the bottom end of the air injection pipeline is mutually communicated with the high-pressure air cavity, and a movable door is mounted at the other end of the air injection pipeline;

the movable door can be automatically opened after reaching a preset air pressure in the high-pressure air cavity and automatically closed when being lower than the preset air pressure.

In a preferred embodiment of the present invention, a fluid guide is fixedly installed at the center of the storage tank, the air injection duct can horizontally inject an air flow into the storage tank, and the sidewall of the fluid guide can guide the air flow to flow upward.

As a preferable scheme of the present invention, the movable door includes a circular plate disposed at the center of the corresponding end surface of the air injection pipeline, the circular plate is connected to the air injection pipeline through a plurality of connecting rods, a closing plate for closing a gap between two adjacent connecting rods is hinged to the air injection pipeline, the closing plate is connected to the air injection pipeline through an elastic restoring member, and a screen is connected between two adjacent connecting rods.

As a preferable scheme of the invention, the second stirring member comprises a bracket fixedly installed in the modification chamber, a slurry support is rotatably installed on the bracket, the bottom surface of the slurry support is attached to a gas-liquid interface in the modification chamber, a plurality of stirring pieces are uniformly connected to the bottom surface of the slurry support, a membrane cavity is wrapped on the stirring pieces, a liquid layer is filled in the membrane cavity, and the density of the liquid layer is greater than that of water.

As a preferable aspect of the present invention, the non-contact driving member is extracted by a specific method including:

40321, extracting the air heated by the water bath above the modification chamber by using air extraction equipment;

40322, unidirectionally injecting the extracted gas into the high-pressure gas cavity;

40323, when the air pressure inside the high-pressure air cavity reaches a preset value, the high-pressure air cavity sprays horizontal air flow to the bottom of the modification chamber;

40324, driving the bottom of the modification chamber by horizontal gas flow to mix to form horizontal liquid flow;

40325 a conical media is placed at the bottom of the modification chamber, and the horizontal liquid flow impinges on and is redirected by the conical media to form a longitudinal stirring flow.

Compared with the prior art, the invention has the following beneficial effects:

the invention firstly prepares the nano calcium carbonate by taking the D-gluconic acid as a crystal form control agent, thereby further reducing the particle size of the calcium carbonate and facilitating better dispersion in the industrial filling process, and then prepares the modified calcium carbonate by utilizing the nano calcium carbonate to be matched with sodium dodecyl sulfate, so that the oil absorption of the modified calcium carbonate is reduced (the oil absorption is less than 60mL according to 100 g), and in the modification process of the nano calcium carbonate, the invention reduces the mechanical stirring of the nano calcium carbonate, drives the calcium carbonate to stir in a water flow mode, can effectively prevent the modified adsorption layer on the surface of the calcium carbonate from falling off, and effectively ensures the modification effect and the success rate.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It should be apparent that the drawings in the following description are merely exemplary, and that other embodiments can be derived from the drawings provided by those of ordinary skill in the art without inventive effort.

FIG. 1 is a schematic flow chart of a process optimization method according to an embodiment of the present invention;

FIG. 2 is a schematic overall structure diagram according to an embodiment of the present invention;

FIG. 3 is a schematic structural diagram of a movable door according to an embodiment of the present invention;

FIG. 4 is a schematic structural diagram of a stirring paddle according to an embodiment of the present invention.

The reference numerals in the drawings denote the following, respectively:

1-a modification chamber; 2-a second stirring member; 3-a non-contact drive component; 4-stirring paddle;

21-a scaffold; 22-pulp support; 23-stirring slices; 24-a membrane cavity; 25-a membrane cavity;

31-a circulation lumen; 32-a gas extraction device; 33-high pressure air cavity; 34-a spray assembly; 35-a through pipe; 36-a one-way valve;

341-U-shaped lumen; 342-an ejection lumen; 343-a storage tank; 344-a gas injection channel; 345-a movable door; 346-introducing a fluid;

3451-circular plate; 3452-connecting rod; 3453-closure plate; 3454-elastic restoring member; 3455-Screen.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in fig. 1, the invention provides a method for optimizing a modification process of nano calcium carbonate, which comprises the following steps:

Wherein, the carbonization method of the step 200 comprises the following steps:

step 202, adding 1-1.5 mass percent of D-sodium gluconate into the solution, passing carbon dioxide gas into the solution, and controlling the flow rate of the carbon dioxide gas to be 60-80 mL/min;

Wherein, the specific method for modification in the step 400 comprises the following steps:

step 401, adding 7-9% by mass of calcium carbonate suspension and 3-4% by mass of modifier into a modification chamber;

and 403, keeping the mixture in the modification chamber at a constant temperature of 60-80 ℃, simultaneously stirring the mixture in the modification chamber in a non-mechanical manner, and finishing the modification process after 50-70 min.

With the increase of the mass fraction of the modifier, the oil absorption of the spheroidal nano calcium carbonate tends to increase after gradually decreasing, and when the dosage of the modifier is 3.5 percent, the oil absorption reaches the minimum value of 44.1mL according to 100 g. The oil absorption of the calcium carbonate is reduced as the coating amount of the calcium carbonate surface medicament is increased along with the increase of the dosage of the modifier; the amount of the modifier is continuously increased, when the surface coating amount of the calcium carbonate reaches a saturated state, the oil absorption is not reduced, and the addition of the modifier can lead the redundant modifier molecules to be adsorbed on the surface of the completely modified calcium carbonate, so that part of the hydrophilic groups on the surface of the calcium carbonate face outwards, thereby reducing the modification effect. Therefore, the best modifier mass fraction was selected to be 3.5%.

D-sodium gluconate is used as D-sodium gluconate, the spheroidal nano calcium carbonate is successfully prepared by a carbonization method, the influence of factors such as carbonization temperature and D-sodium gluconate dosage on the appearance of the nano calcium carbonate is considered, and the obtained optimized process conditions are that the carbonization temperature is 50 ℃, the stirring speed is 800r/min, the mass fraction of the D-sodium gluconate is 1.5%, the initial mass fraction of the calcium hydroxide is 7%, and the CO2 flow rate is 60 mL/min.

The prepared nano calcium carbonate is modified by a wet method, the influence of factors such as the using amount of a modifier, the modification temperature, the modification time and the like on the oil absorption of the nano calcium carbonate is considered, and the optimal modification process conditions are that the mass fraction of the modifier is 3.5%, the modification temperature is 70 ℃, and the modification time is 50 min. The oil absorption of the modified spheroidal nano calcium carbonate reaches the first-class standard of national industrial calcium carbonate (the oil absorption is less than 60mL according to 100 g).

The invention aims to prepare nano-grade modified calcium carbonate, so that the particles of the modified calcium carbonate are smaller, and the smaller particles of the modified calcium carbonate can be driven and stirred by smaller driving force, thereby providing the possibility of removing mechanical stirring, and further improving the modification effect and success rate of the modified calcium carbonate.

The morphology and particle size of calcium carbonate are very sensitive to temperature. The preparation of the spheroidal nano calcium carbonate is facilitated at a lower temperature of less than or equal to 50 ℃; the spherical-like calcium carbonate particles are difficult to obtain at higher temperature of more than 50 ℃; and the calcium carbonate particles have the tendency of spindle-shaped transition along with the gradual rise of the temperature. This is probably due to the fact that the nucleation rate and growth rate of calcium carbonate are increased at high temperature, but the growth rate is the dominant factor, resulting in most of the grains growing into spindle-shaped particles; and the lower temperature can reduce the growth rate of the calcium carbonate particles, so that the nucleation rate of the calcium carbonate particles is the dominant factor, and finally, spherical calcium carbonate particles with smaller particle size and uniform appearance are formed. The optimal carbonization temperature is selected to be 50 ℃ in comprehensive consideration.

The stirring speed has obvious influence on the morphology of the calcium carbonate particles. When the stirring speed is less than 800r/min, the morphology of the calcium carbonate particles is a typical spindle-shaped structure. When the stirring speed reaches or exceeds 800r/min, the calcium carbonate particles begin to be converted from a spindle shape into a sphere-like shape, the particle size of the particles is uniform, and the appearance is single. The reason for this may be that the initially formed calcium carbonate crystal nuclei having a high surface energy are rapidly accumulated locally due to a too low stirring speed to adhere to each other to form a spindle-shaped structure. When the rotating speed reaches 800r/min, the shape of the particles is similar to a sphere, the stirring rotating speed is continuously increased, and the shape change of the particles is not obvious. Comprehensively considering, the optimal stirring speed is selected to be 800 r/min.

When the mass fraction of the D-sodium gluconate is less than 1.5 percent, the calcium carbonate particles have uneven particle size and irregular appearance; when the mass fraction of the D-sodium gluconate reaches 1.5%, the prepared calcium carbonate particles have uniform particle size and single appearance. This is probably because when the amount of D-sodium gluconate is small, the amount of gluconate ions in the liquid phase is not sufficient to completely combine with calcium ions provided by calcium hydroxide, so that most of carbonate ions provided by carbon dioxide directly react with calcium ions provided by calcium hydroxide without replacing calcium ions in calcium gluconate, so that the gluconate ions cannot play a sufficient crystal-directing role; the change of the morphology of the calcium carbonate particles is not obvious when the mass fraction of the sodium D-gluconate is continuously increased, which indicates that 1.5 percent of the sodium gluconate is enough to provide enough guide crystal nucleuses. Therefore, the optimal mass fraction of sodium D-gluconate is selected to be 1.5%.

When the initial mass fraction of the calcium hydroxide is lower than 7%, the morphology and the particle size distribution of calcium carbonate particles are relatively uniform; when the initial mass fraction of the calcium hydroxide is higher than 7 percent, the morphology and the particle size of the prepared calcium carbonate particles are gradually worsened, the proportion of the spheroidal calcium carbonate particles is reduced, and a part of the particles are changed from spheroidal to irregular blocky. This is probably because the mass fraction of calcium hydroxide is low, the concentration and supersaturation of calcium ions in the liquid phase are low, the number of calcium carbonate crystal nuclei formed is relatively small, the number of times of collision between the crystal nuclei is limited, and the particle size of the particles formed is small; on the contrary, when the concentration is large, the number of calcium carbonate crystal nuclei is relatively increased, and the number of collisions is also increased, resulting in the growth of calcium carbonate particles into irregular particles. Therefore, 7% was selected as the optimum initial mass fraction of calcium hydroxide.

When the flow rate is lower than 60mL/min, the calcium carbonate particles have different shapes and uneven particle sizes; when the flow rate is increased to 60mL/min, the calcium carbonate particles are in a sphere-like shape and are uniform and single in size; the flow rate is increased continuously, so that a part of the calcium carbonate particles are transformed from the sphere-like shape to other shapes, and the proportion of the sphere-like particles is reduced. Therefore, 60mL/min was selected as the optimum flow rate.

The non-mechanical stirring method in step 403 includes:

Therefore, in the present invention, a method of directly contacting calcium carbonate without using a stirring machine is provided, in which calcium carbonate is stirred to reduce the falling of organic groups.

The non-mechanical stirring is mainly driven by a water flow or an air flow in an isothermal mode, and the transverse stirring flow and the longitudinal stirring flow are matched to form three-dimensional stirring in the modification chamber 1, so that the calcium carbonate can move in multiple dimensions.

The non-contact driving component 3 comprises a circulating cavity pipe 31 and an air pumping device 32, one end of the circulating cavity pipe 31 is connected to the top end of the modification chamber 1, a high-pressure air cavity 33 is arranged at the bottom end of the circulating cavity pipe 31, the high-pressure air cavity 33 is communicated and installed at the bottom end of the modification chamber 1, the air pumping device 32 is installed in the circulating cavity pipe 31, and the air pumping device 32 can pump air at the top end of the modification chamber 1 to the high-pressure air cavity 33; a spraying assembly 34 is installed at the bottom end of the modification chamber 1, the spraying assembly 34 is located above the high-pressure air cavity 33, the spraying assembly 34 can spray airflow to the modification chamber 1 under the driving of the air in the high-pressure air cavity 33, and the spraying assembly 34 can prevent the liquid in the modification chamber 1 from flowing back to the high-pressure air cavity 33; the high-pressure air chamber 33 is communicated with the other end of the circulating cavity tube 31 through a through tube 35, the air extractor 32 is installed at one end of the through tube 35 close to the high-pressure air chamber 33, and a one-way valve 36 is fixedly installed at the other end of the through tube 35.

The gradual inflation is performed through the check valve 36, and the high pressure air chamber 33 is inflated to ensure that the high pressure air chamber 33 can eject a relatively high speed air flow.

The horizontal stirring flow is mainly stirred by the second stirring piece 2 at the gas-liquid interface, the stirring wave generated by the second stirring piece 2 is downwards transmitted and gradually reduced, and the direct contact of the calcium carbonate and the second stirring piece 2 can be avoided only by controlling the spraying height of the longitudinal stirring flow.

The longitudinal stirring flow is sprayed out from the bottom of the modification chamber 1, and the calcium carbonate in the modification chamber 1 is driven to move upwards by the longitudinal stirring flow.

In this embodiment, there is provided an airflow-driven method: the method of recycling gas production by pumping air from the top end of the modification chamber 1 and then spraying air from the bottom end of the modification chamber 1 is mainly characterized in that the temperature of the modification chamber 1 can be kept relatively stable in consideration of the condition that the modification chamber 1 is sealed and is heated in a water bath.

It is of course also possible to draw the liquid in the modification chamber 1 and then spray it downwards, but this solution would reduce the entrapment of the liquid calcium carbonate, resulting in direct contact of the calcium carbonate with the mechanical structure.

Heating the external liquid by pumping will cause the amount of solution in the modification chamber 1 to change, affecting the modification process.

The spraying assembly 34 comprises a U-shaped cavity tube 341 fixedly mounted on the modification chamber 1, a spraying cavity 342 is arranged above the U-shaped cavity tube 341, the spraying cavity 342 is mounted on a symmetry axis of the U-shaped cavity tube 341 in a communicating manner, a storage tank 343 is arranged at the bottom end of the U-shaped cavity tube 341, at least two air injection channels 344 are mounted on the side wall of the storage tank 343, the bottom ends of the air injection channels 344 are mutually communicated with the high-pressure air cavity 33, and a movable door 345 is mounted at the other end of the air injection channels 344; the movable door 345 can be automatically opened after reaching a preset air pressure in the high pressure air chamber 33, and can be automatically closed when being lower than the preset air pressure.

The U-shaped cavity tube 341 can receive calcium carbonate and concentrate toward the bottom of the U-shaped cavity tube 341, and the U-shaped cavity tube 341 is configured by a special shape, which can increase the difficulty of the calcium carbonate returning from the U-shaped cavity tube 341.

Wherein, a fluid guiding body 346 is fixedly installed at the center of the storage tank 343, the air injection pipe 344 can horizontally spray an air flow into the storage tank 343, and the sidewall of the fluid guiding body 346 can guide the air flow to flow upwards.

An inwardly directed horizontal air stream is emitted through the air jet passage 344 and drives the calcium carbonate concentrated in the reservoir 343, which moves laterally inwardly and collides with the fluid 346 and moves upwardly as directed by the fluid 346.

The specific air pressure of the air jet and the caliber of the air jet pipeline 344 are equivalent to the force directly acting on the surface of the nano calcium carbonate, the acting force is larger than the acting force of the first stirring member stirring the water flow at 800r/min, and the acting force can not drive the nano calcium carbonate to collide with the liquid layer 25, and preferably, the acting force is equal to 1.2 times the acting force of the first stirring member stirring the water flow at 800 r/min.

The guiding fluid 346 approaches a cone shape to be guided by its curved surface.

The movable door 345 includes a circular plate 3451 disposed at the center of the corresponding end surface of the air injection duct 344, the circular plate 3451 is connected to the air injection duct 344 through a plurality of connecting rods 3452, a closing plate 3453 for closing a gap between two adjacent connecting rods 3452 is hinged to the air injection duct 344, the closing plate 3453 is connected to the air injection duct 344 through an elastic restoring member 3454, and a screen 3455 is connected between two adjacent connecting rods 3452.

Through setting up polylith closing plate 3453 with the angle that opens and shuts that reduces single closing plate 3453, can reduce the deformation degree of single elasticity piece 3454 that resets, can make elasticity reset the faster recovery of piece 3454 to prevent calcium carbonate's refluence.

Wherein, second stirring piece 2 includes fixed mounting and is in support 21 in the modification room 1 rotate on the support 21 and install and starch and hold in the palm 22, the bottom surface laminating that the thick liquid held in the palm 22 is in on the gas-liquid interface in the modification room 1 the bottom surface that the thick liquid held in the palm 22 evenly is connected with a plurality of stirring pieces 23 the parcel has membrane chamber 24 on the stirring piece 23 the membrane chamber 24 intussuseption is filled with liquid layer 25, just the density of liquid layer 25 is greater than the density of water.

The liquid layer 25 is settled under water by the larger density, so that the liquid layer 25 can act as a secondary paddle for stirring, and the liquid layer 25 is soft in texture due to its mainly liquid constitution, and can reduce damage to calcium carbonate, such as carbon tetrachloride (CCl)₄) Trichloromethane, and the like.

Example 1

The method is carried out in the device shown in FIGS. 2-3, and comprises the following specific steps:

step A, heating deionized water to 60 ℃ and keeping the temperature, adding CaO powder into the deionized water, stirring and reacting, and then aging the reaction solution to obtain a calcium hydroxide solution;

b, adding 8% by mass of calcium hydroxide solution into a carbonization chamber, heating the solution in the carbonization chamber to 50 ℃ through water bath heating, and stirring the solution in the carbonization chamber at the speed of 800r/min through a first stirring piece;

step C, adding 1.5% by mass of D-sodium gluconate into the solution, passing carbon dioxide gas into the solution, controlling the flow rate of the carbon dioxide gas to 70mL/min, and stopping introducing the carbon dioxide gas until the pH value of the calcium hydroxide solution reaches 7 to finish the carbonization reaction;

step D, carrying out suction filtration and washing on the carbonized mixture in sequence to obtain a calcium carbonate filter cake, adding deionized water, and pulping to obtain a calcium carbonate suspension;

step E, adding 8 mass percent of calcium carbonate suspension and 3.5 mass percent of sodium dodecyl sulfate into the modification chamber;

step F, heating the liquid in the modification chamber in a water bath at 70 ℃ to keep the mixture in the modification chamber in a constant temperature state at 70 ℃;

step G, hot air above the modification chamber is pumped into the high-pressure air cavity 33 through the air pumping device 32, the jet assembly 34 jets out the hot air in the high-pressure air cavity 33, the jetted air flow blows the nano calcium carbonate to flow along the guide fluid 346 and form an upward nano carbonic acid flow, the nano carbonic acid flow is upwards thrown out and falls down, the non-contact stirring process is completed in the process, and the modification process is completed after the nano carbonic acid flow lasts for 50 min;

and step H, sequentially carrying out suction filtration, drying at 70 ℃ and screening by a 100-mesh sieve on the modified mixture to obtain the modified calcium carbonate.

Example 2

The procedure is as in example 1, except that:

and E, adding 8 mass percent of calcium carbonate suspension and 3.0 mass percent of sodium dodecyl sulfate into the modification chamber.

Example 3

The procedure is as in example 1, except that:

and F, heating the liquid in the modification chamber in a water bath at 80 ℃ to keep the mixture in the modification chamber in a constant temperature state of 70 ℃.

Comparative example 1

The procedure is as in example 1, except that:

and G, as shown in figure 4, stirring the nano calcium carbonate in the modification chamber by using a stirring paddle 4 for 50min, and then finishing the modification process.

Detection example 1

The spheroidal nano calcium carbonate prepared in example 1 has a uniform particle size (50-100 nm), and is nano calcium carbonate. The dispersion is uniform, the appearance is single and is similar to a sphere. The minimum oil absorption (based on 100 g) was 45.1 mL.

Detection example 2

The spheroidal nano calcium carbonate prepared in example 2 has a uniform particle size (50-100 nm), and is nano calcium carbonate. The dispersion is uniform, the appearance is single and is similar to a sphere. The minimum oil absorption (based on 100 g) was 48.2 mL.

Detection example 3

The spheroidal nano calcium carbonate prepared in example 3 has a uniform particle size (50-100 nm), and is nano calcium carbonate. The dispersion is uniform, the appearance is single and is similar to a sphere. The minimum oil absorption (based on 100 g) was 47.3 mL.

Detection example 4

The spheroidal nano calcium carbonate prepared by the comparative example 1 has uniform particle size (50-100 nm) and is nano calcium carbonate. The dispersion is uniform, the appearance is single and is similar to a sphere. The minimum oil absorption (based on 100 g) was 46.8 mL.

And (3) measuring the oil absorption of the sample:

the oil absorption of the modified calcium carbonate sample is measured by using an analysis method of the oil absorption of calcium carbonate in the national standard GB 19281-2003 'calcium carbonate analysis method'. The determination method comprises weighing 5g of sample, accurately measuring to 0.01g, and placing on a glass plate. DOP is put into a 50mL burette, DOP is dripped into a sample, the sample is continuously stirred and ground by a knife during dripping, the sample is dispersed at first, and then the sample is gradually agglomerated until the sample is completely wetted by DOP, and the end point is formed. After waiting 5min, the number of burette volumes was read. Oil absorption is measured as ω 3 and is the volume (mL) of DOP absorbed per 100g of calcium carbonate. The calculation formula is as follows:

ω3＝(V/m)×100。

v-volume of DOP added dropwise, mL:

m-mass of sample, g.

Taking the average value of the results of the parallel determination, the absolute difference of the results of the 2 times of parallel determination is not more than 2.0 mL.

The specific method for extracting the non-contact driving part comprises the following steps:

The above embodiments are only exemplary embodiments of the present application, and are not intended to limit the present application, and the protection scope of the present application is defined by the claims. Various modifications and equivalents may be made by those skilled in the art within the spirit and scope of the present application and such modifications and equivalents should also be considered to be within the scope of the present application.

Claims

1. A method for optimizing a modification process of nano calcium carbonate is characterized by comprising the following steps:

2. The optimization method of the modification process of nano calcium carbonate according to claim 1, characterized in that: the carbonization method of the step 200 comprises the following steps:

3. The optimization method of the modification process of nano calcium carbonate according to claim 2, characterized in that: the specific method for modification in step 400 includes:

4. The optimization method of the modification process of nano calcium carbonate according to claim 3, characterized in that: the specific non-mechanical stirring method in step 403 includes:

5. The optimization method of the modification process of nano calcium carbonate according to claim 4, characterized in that: the non-contact driving component (3) comprises a circulating cavity pipe (31) and an air pumping device (32), one end of the circulating cavity pipe (31) is connected to the top end of the modification chamber (1), a high-pressure air cavity (33) is arranged at the bottom end of the circulating cavity pipe (31), the high-pressure air cavity (33) is communicated and installed at the bottom end of the modification chamber (1), the air pumping device (32) is installed in the circulating cavity pipe (31), and the air pumping device (32) can pump air at the top end of the modification chamber (1) to the high-pressure air cavity (33);

a spraying assembly (34) is installed at the bottom end of the modification chamber (1), the spraying assembly (34) is located above the high-pressure air chamber (33), the spraying assembly (34) can spray airflow to the modification chamber (1) under the driving of air in the high-pressure air chamber (33), and the spraying assembly (34) can prevent liquid in the modification chamber (1) from flowing back to the high-pressure air chamber (33);

the high-pressure air cavity (33) is communicated with the other end of the circulating cavity tube (31) through a through tube (35), the air suction device (32) is installed at one end, close to the high-pressure air cavity (33), of the through tube (35), and a one-way valve (36) is fixedly installed at the other end of the through tube (35).

6. The optimization method of the modification process of nano calcium carbonate according to claim 5, characterized in that: the spraying assembly (34) comprises a U-shaped cavity tube (341) fixedly arranged in the modification chamber (1), a spraying cavity tube (342) is arranged above the U-shaped cavity tube (341), the spraying cavity tube (342) is communicated and arranged on a symmetry axis of the U-shaped cavity tube (341), a storage tank (343) is arranged at the bottom end of the U-shaped cavity tube (341), at least two air injection channels (344) are arranged on the side wall of the storage tank (343), the bottom end of the air injection pipeline (344) is communicated with the high-pressure air cavity (33), and a movable door (345) is arranged at the other end of the air injection pipeline (344);

the movable door (345) can be automatically opened after reaching a preset air pressure in the high-pressure air chamber (33) and automatically closed when being lower than the preset air pressure.

7. The optimization method of the modification process of nano calcium carbonate according to claim 6, characterized in that: a fluid guide (346) is fixedly installed at the center of the storage tank (343), the air injection pipeline (344) can horizontally spray air flow into the storage tank (343), and the side wall of the fluid guide (346) can guide the air flow to flow upwards.

8. The optimization method of the modification process of nano calcium carbonate according to claim 7, characterized in that: the movable door (345) comprises a circular plate (3451) arranged in the center of the corresponding end face of the air injection pipeline (344), the circular plate (3451) is connected with the air injection pipeline (344) through a plurality of connecting rods (3452), a closing plate (3453) used for closing the gap between two adjacent connecting rods (3452) is hinged on the air injection pipeline (344), the closing plate (3453) is connected with the air injection pipeline (344) through an elastic resetting piece (3454), and a screen (3455) is connected between two adjacent connecting rods (3452).

9. The optimization method of the modification process of nano calcium carbonate according to claim 8, characterized in that: second stirring piece (2) are including fixed mounting support (21) in modification room (1) rotate on support (21) and install and starch support (22), the bottom surface laminating that the thick liquid held in the palm (22) is in on the gas-liquid interface in modification room (1) the bottom surface that the thick liquid held in the palm (22) evenly is connected with a plurality of stirring pieces (23) the parcel has membrane chamber (24) on stirring piece (23) the intussuseption of membrane chamber (24) is filled with liquid layer (25), just the density of liquid layer (25) is greater than the density of water.

10. The optimization method of the modification process of nano calcium carbonate according to any one of claims 5 to 9, characterized in that: the specific method for extracting the non-contact driving part comprises the following steps: