Method for preparing modified dolomite powder

Abstract

The application discloses a preparation method of modified dolomite powder and belongs to the technical field of dolomite modification treatment. The modified dolomite powder is prepared from the following raw materials in weight: 70-90 parts of dolomite powder, 1-5 parts of white hydrogen bentonite powder, 10-30 parts of nano-carbonate and a dispersing agent, wherein the weight of the dispersing agent is 0.1-0.3 percent of the weight of the nano-carbonate. The preparation method of the modified dolomite powder provided by the application can make the weak-acid dolomite powder dispersion liquid and the weak-alkali nano-carbonate dispersion liquid mix, and then make the dolomite powder particles and the nano-carbonate particles assemble and agglomerate through electrostatic mutual attraction, thereby improving the loading capacity and loading area of the nano-carbonate particles on the surface of the dolomite powder particles, and making the nano-carbonate particles uniformly and stably coated on the surface of the dolomite powder particles to form composite particles.

Description

Technical Field

[0001] This invention relates to a method for preparing modified dolomite powder, belonging to the field of dolomite modification technology. Background Technology

[0002] Dolomite, with the chemical composition CaMg(CO3)2, is a carbonate mineral belonging to the trigonal crystal system. Ultrafine calcium-magnesium filler, produced from dolomite through beneficiation, washing, crushing, and fine grinding, can, to some extent, replace relatively expensive light or heavy calcium carbonate powders and is widely used in rubber, plastics, papermaking, and coatings manufacturing. Currently, the application of dolomite faces some challenges. For example, the reserves of high-grade dolomite are decreasing, leading to increasingly higher prices. Meanwhile, large quantities of low-whiteness dolomite are typically used as aggregates, making it difficult to apply to the manufacture of high-end coatings and other high-end products, resulting in low product value for dolomite powder. Furthermore, when dolomite powder is directly used as a filler, the sharp edges of the dolomite particles result in a large contact angle, and the significant difference in interfacial properties between the powder and the carrier material affects its dispersibility within the carrier material.

[0003] To improve the performance of dolomite powder, existing technologies attempt to modify it using mechanochemical methods or by coating the surface of dolomite powder particles with substances such as nano-calcium carbonate. For example, existing technologies provide a method for coating the surface of dolomite particles with calcium carbonate through chemical deposition in a Ca(OH)₂-H₂O-CO₂ system, which can modify the surface of dolomite powder particles. However, this method requires control of parameters such as Ca(OH)₂ concentration, gas-liquid ratio, reaction temperature, pH value, and conductivity, making the process complex and resulting in composite particles with highly variable performance. This invention aims to provide a new method for modifying dolomite powder to further improve its whiteness and dispersibility in carrier materials.

[0004] It should be noted that the above content falls within the inventor's technical knowledge and does not necessarily constitute prior art. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a method for preparing modified dolomite powder, which enables the modified dolomite powder to have the advantages of high hardness of dolomite as well as the physicochemical properties and high whiteness of nano carbonate, thus broadening the application field of dolomite powder and significantly increasing the economic added value of dolomite powder.

[0006] The present invention achieves the above objectives by adopting the following technical solutions:

[0007] A method for preparing modified dolomite powder includes the following raw materials by weight: 70-90 parts dolomite powder, 1-5 parts white hydrogen-based bentonite powder, 10-30 parts nano-carbonate, and a dispersant, wherein the weight of the dispersant is 0.1%-0.3% of the weight of the nano-calcium carbonate.

[0008] Among them, nano carbonates are selected from any one or two of calcium carbonate and magnesium carbonate;

[0009] The dispersant is selected from any one or more of sodium hexametaphosphate, sodium tripolyphosphate, and sodium pyrophosphate.

[0010] In a preferred embodiment of the present invention, the dolomite powder has a blue light whiteness of 85±5, and the white hydrogen-based bentonite powder has a blue light whiteness of 80±5.

[0011] In a preferred embodiment of the present invention, the dolomite powder has a particle size of 600-800 mesh, the white hydrogen-based bentonite powder has a particle size of 1000-1200 mesh, and the nano-carbonate has a particle size of 1-500 nm.

[0012] In a preferred embodiment of the present invention, the proportions of the components contained in the dolomite powder are as follows: silicon dioxide less than 3%, calcium oxide 30% ± 1.5%, magnesium oxide 20% ± 1.5%, aluminum oxide less than 0.1%, and acid-insoluble matter less than 3%.

[0013] The method for preparing modified dolomite powder provided by this invention includes the following steps:

[0014] (1) Mix dolomite powder and white hydrogen-based bentonite powder with water, adjust the pH value to 6-7, and then ultrasonically disperse for 15-30 minutes at a frequency of 1500-2000 Hz to prepare a dolomite powder dispersion. The purpose of this step is to activate the dolomite powder. White hydrogen-based bentonite powder swells when it comes into contact with water, which has a suspending effect. Moreover, it has high thermal stability, which can suspend the dolomite powder in the dispersion and prevent it from settling, thus forming a stable dolomite powder dispersion.

[0015] (2) Mix nano-carbonate with dispersant and water, adjust the pH to 7-8, and then disperse at high speed of 100,000-150,000 rpm for 30-50 min to prepare nano-carbonate dispersion; wherein, sodium hexametaphosphate, sodium tripolyphosphate and sodium pyrophosphate are negatively charged after ionization in water as dispersants, and adsorb onto the surface of nano-carbonate particles, so that a double electric layer structure is formed on the surface of nano-carbonate particles, the surface charge density is increased, and the van der Waals attraction between nano-carbonate particles is overcome by the repulsive force of the same charge on the surface, thereby improving the dispersion effect of nano-carbonate;

[0016] (3) Mix the dolomite powder dispersion with the nano carbonate dispersion, adjust the pH value to 7±0.1, and then mix at a speed of 30,000 to 50,000 rpm for 60 to 90 minutes to prepare a mixture;

[0017] (4) The mixture is atomized and dried at 30-50℃ to prepare modified dolomite powder.

[0018] In a preferred embodiment of the present invention, in step (1), the weight of water added is 8 to 10 times the sum of the weights of dolomite powder and white hydrogen-based bentonite powder.

[0019] In a preferred embodiment of the present invention, in step (2), the weight of water added is 8 to 10 times the sum of the weights of the nano carbonate and the dispersant.

[0020] In a preferred embodiment of the present invention, the pH adjuster is citric acid or sodium bicarbonate.

[0021] The beneficial effects of this application include, but are not limited to:

[0022] The modified dolomite powder preparation method provided by the present invention involves mixing a weakly acidic dolomite powder dispersion with a weakly alkaline nano-carbonate dispersion. Through electrostatic attraction, the dolomite powder particles and nano-carbonate particles are assembled and agglomerated, which increases the loading capacity and loading area of ​​the nano-carbonate particles on the surface of the dolomite powder particles, so that the nano-carbonate particles are uniformly and stably coated on the surface of the dolomite powder particles to form composite particles.

[0023] The composite particles provided by this invention have an overall size in the micrometer range, solving the problem of poor dispersibility of nano-carbonates. Furthermore, the nano-carbonates, acting as a surface modifier, blunt the edges and corners of the dolomite particles, improving their particle shape and reducing the contact angle of the coated particles, thus facilitating dispersion. Secondly, the coating of the dolomite particles with nano-carbonates significantly increases the specific surface area of ​​the composite particles, enhancing their surface energy and chemical activity, thereby improving the activity of the dolomite powder and promoting its good interfacial bonding with the carrier material. Thirdly, coating low-grade dolomite particles with nano-carbonates not only improves whiteness but also gives the composite particles the advantages of high dolomite hardness and the physicochemical properties of nano-carbonates, broadening the application areas of dolomite powder. It can be used in the production of high-end latex paints and other products, significantly increasing the economic added value of dolomite powder. Attached Figure Description

[0024] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0025] Figure 1SEM image of dolomite particles coated with nano-carbonates. Detailed Implementation

[0026] The present invention will be further described in detail below. However, it should be noted that the following specific embodiments are merely exemplary examples of the invention, and the scope of protection of the invention is not limited thereto. The scope of protection of the invention is defined only by the claims. It will be apparent to those skilled in the art that various other modifications and substitutions can be made to the embodiments of the invention within the scope of protection defined by the claims, and the same technical effects can still be achieved, thus achieving the ultimate technical objective of the invention.

[0027] In the following examples, the blue light whiteness of the dolomite powder is 85±5, and the blue light whiteness of the white hydrogen-based bentonite powder is 80±5.

[0028] The particle size of dolomite powder is 600-800 mesh, the particle size of white hydrogen-based bentonite powder is 1000-1200 mesh, and the particle size of nano carbonate is 1-500 nm.

[0029] The dolomite powder is sourced from Meng County, Yangquan City, Shanxi Province. The proportions of the components in the dolomite powder are as follows: silicon dioxide less than 3%, calcium oxide 30% ± 1.5%, magnesium oxide 20% ± 1.5%, aluminum oxide less than 0.1%, and acid-insoluble matter less than 3%.

[0030] Unless otherwise specified, all raw materials were purchased through commercial channels.

[0031] Example 1:

[0032] In this embodiment, the modified dolomite powder is prepared from the following raw materials by weight:

[0033] raw material weight Dolomite powder 70kg White hydrogen-based bentonite powder 1kg Nano carbonates: Nano calcium carbonate, Nano magnesium carbonate 20kg of nano-calcium carbonate and 15kg of nano-magnesium carbonate Dispersant: Sodium hexametaphosphate 0.3% by weight of nano-calcium carbonate and nano-magnesium carbonate

[0034] The method for preparing modified dolomite powder provided in this embodiment specifically includes the following steps:

[0035] (1) Mix dolomite powder and white hydrogen-based bentonite powder with water. The weight of water added is 9 times the sum of the weights of dolomite powder and white hydrogen-based bentonite powder. Adjust the pH value to 6.5. Then, ultrasonically disperse the mixture for 30 minutes at a frequency of 1800 Hz to prepare a dolomite powder dispersion.

[0036] (2) Mix nano carbonate with dispersant and water. The weight of water added is 8 times the sum of the weights of dolomite powder and white hydrogen-based bentonite powder. Adjust the pH value to 7.4, disperse at high speed for 45 min, and disperse at a speed of 120,000 rpm to prepare nano carbonate dispersion.

[0037] (3) Mix the dolomite powder dispersion with the nano carbonate dispersion, adjust the pH value to 7±0.1, and mix at a speed of 40,000 rpm for 80 min to prepare a mixture;

[0038] (4) The mixture is atomized and dried at 35°C to prepare modified dolomite powder.

[0039] The pH adjusters are citric acid and sodium bicarbonate.

[0040] Example 2:

[0041] In this embodiment, the modified dolomite powder is prepared from the following raw materials by weight:

[0042] raw material weight Dolomite powder 90kg White hydrogen-based bentonite powder 5kg Nano carbonates: Nano calcium carbonate 30kg Dispersant: Sodium pyrophosphate 0.1% by weight of nano-calcium carbonate

[0043] Example 3:

[0044] In this embodiment, the modified dolomite powder is prepared from the following raw materials by weight:

[0045] raw material weight Dolomite powder 80kg White hydrogen-based bentonite powder 2.5kg Nano carbonates: Nano magnesium carbonate 40kg Dispersant: Sodium tripolyphosphate 0.2% by weight of nano-magnesium carbonate

[0046] Figure 1 The image shown is a SEM image of dolomite particles coated with nano-carbonates.

[0047] To verify the modification effect of the dolomite powder provided in this application, the following tests were conducted on the modified dolomite powder and its effects, and the results are shown in the table below.

[0048] The modified dolomite powder prepared in the embodiments of the present invention and the dolomite powder raw material sample were tested for whiteness and oil absorption value according to conventional methods. The results are shown in the table below.

[0049] Sample Whiteness Oil absorption value (ml / 100g) Example 1: Modified Dolomite Powder 88 20.6 Example 2 Modified Dolomite Powder 86 19.3 Example 3 Modified Dolomite Powder 93 27.8 600-800 mesh ordinary dolomite powder 82 17.8

[0050] As can be seen from the table above, the whiteness of the modified dolomite powder prepared in Examples 1-3 of the present invention is significantly increased. The increase in oil absorption value indicates that the surface roughness of the dolomite particles is increased and the specific surface area is increased, which can improve the bonding force between the dolomite powder and plastic and rubber substrates.

[0051] Application Example 1:

[0052] To further verify the performance of the modified dolomite powder provided by the present invention, in Application Example 1, the modified dolomite powder prepared in the embodiments of the present invention and ordinary dolomite powder were applied to PVC plastic.

[0053] Specifically, the PVC plastic formula is as follows: 100 parts PVC resin, 4 parts ACR, 17 parts dolomite powder (using the modified dolomite powder of this invention or ordinary dolomite powder for experimental comparison), 28 parts heavy calcium carbonate (430 mesh), 5 parts silicone oil, 1.5 parts sodium stearate, 3 parts calcium-zinc composite stabilizer, 2 parts diisononyl phthalate (DINP), and 0.5 parts 1076 antioxidant. The PVC plastic is prepared according to conventional methods, and the tensile strength and impact strength of the plastic are measured as shown in the table below.

[0054] Testing items Modified dolomite powder of the present invention Ordinary dolomite powder Tensile strength (MPa) 26.43 21.45 Impact strength MPa 20.14 16.8

[0055] The results in the table above show that the modified dolomite powder prepared in the embodiments of the present invention can significantly improve the tensile strength and impact strength of PVC plastics.

[0056] Application Example 2:

[0057] When titanium dioxide is applied to coatings, in addition to improving whiteness, it also provides opacity or hiding power to the coating. Opacity or hiding power is a measure of the coating's ability to cover a surface that has been coated with other coatings.

[0058] In application example 2, the modified dolomite powder and ordinary dolomite powder prepared in the embodiments of the present invention are applied to a coating, wherein the basic formulation of the coating is as follows:

[0059] 203g heavy calcium carbonate, 150g kaolin, 231g water, 1g CF-10 wetting agent, 6g TEGO-747W dispersant, 1.5g FSN-100 leveling agent, 14g C-12 film-forming aid, 5g R-2020 polyurethane leveling agent, 2.5g Aidi Ke B-199 defoamer, 272g AC-261P acrylic emulsion, 14g ethylene glycol solvent, 95g titanium dioxide (d50 is 0.42μm).

[0060] The application effects of using the modified dolomite powder prepared in the embodiments of the present invention to replace part of the titanium dioxide, compared with using all titanium dioxide, are shown in the table below.

[0061] Group <![CDATA[Hiding power (g / m 2 )]]> The modified dolomite powder of this invention consists of 65g and titanium dioxide 30g. 10.78 The modified dolomite powder of this invention consists of 40g and titanium dioxide 55g. 10.56 All made of titanium dioxide 10.24 The modified dolomite powder of this invention consists of 45g and titanium dioxide 55g. 10.07 The modified dolomite powder of this invention (70g + titanium dioxide) is used. 10.12

[0062] As can be seen from the results in the table above, applying the modified dolomite powder and ordinary dolomite powder prepared in the embodiments of the present invention to coatings can reduce the amount of titanium dioxide used.

[0063] The above specific embodiments should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, any alternative improvements or modifications made to the embodiments of the present invention shall fall within the scope of protection of the present invention.

[0064] Any aspects of this invention not described in detail are well-known to those skilled in the art.

Claims

1. A method for producing a modified dolomite powder, characterized by, It is prepared from the following raw materials by weight: 70-90 parts dolomite powder, 1-5 parts white hydrogen-based bentonite powder, 10-30 parts nano-carbonate, and a dispersant, wherein the weight of the dispersant is 0.1%-0.3% of the weight of the nano-carbonate calcium; Among them, nano carbonates are selected from any one or two of calcium carbonate and magnesium carbonate; The dispersant is selected from any one or more of sodium hexametaphosphate, sodium tripolyphosphate, and sodium pyrophosphate; The dolomite powder has a blue light whiteness of 85±5, and the white hydrogen-based bentonite powder has a blue light whiteness of 80±5. The dolomite powder has a particle size of 600-800 mesh, the white hydrogen-based bentonite powder has a particle size of 1000-1200 mesh, and the nano carbonate has a particle size of 1-500 nm. The preparation method of modified dolomite powder includes the following steps: (1) Mix dolomite powder and white hydrogen-based bentonite powder with water, adjust the pH value to 6-7, and then ultrasonically disperse for 15-30 minutes at a frequency of 1500-2000 Hz to prepare a dolomite powder dispersion. (2) Mix nano carbonate with dispersant and water, adjust the pH to 7-8, and then disperse at high speed of 100,000-150,000 rpm for 30-50 min to prepare nano carbonate dispersion; (3) Mix the dolomite powder dispersion with the nano carbonate dispersion, adjust the pH value to 7±0.1, and then mix at a speed of 30,000 to 50,000 rpm for 60 to 90 minutes to prepare a mixture; (4) The mixture is atomized and dried at 30-50℃ to prepare modified dolomite powder.

2. The method for preparing modified dolomite powder according to claim 1, characterized in that, The proportions of the components contained in the dolomite powder are as follows: silicon dioxide less than 3%, calcium oxide 30%±1.5%, magnesium oxide 20%±1.5%, aluminum oxide less than 0.1%, and acid-insoluble matter less than 3%.

3. The method for preparing modified dolomite powder according to claim 1, characterized in that, In step (1), the weight of water added is 8 to 10 times the sum of the weights of dolomite powder and white hydrogen-based bentonite powder.

4. The method for preparing modified dolomite powder according to claim 1, characterized in that, In step (2), the weight of water added is 8 to 10 times the sum of the weights of the nano carbonate and the dispersant.

5. The method for preparing modified dolomite powder according to claim 1, characterized in that, pH adjusters include citric acid and sodium bicarbonate.

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