Highly dispersible calcium powder and method for its production

Abstract

This application relates to the field of calcium carbonate preparation technology, specifically disclosing a highly dispersible calcium powder and its preparation method. The preparation method of the highly dispersible calcium powder of this application includes the following steps: mixing heavy calcium carbonate coarse powder with a grinding aid, and then dry grinding to obtain pretreated heavy calcium carbonate coarse powder; mixing grinding media and grinding aid to obtain a mixture; mixing the pretreated heavy calcium carbonate coarse powder, water, and glycerol to obtain a mixed liquid; mixing the mixture and the mixed liquid to obtain a primary suspension, followed by wet grinding to obtain a semi-finished product; the grinding aid is mainly made from the following raw materials: dispersant, modifier, surfactant, and auxiliary agent, the modifier including aluminum-titanium composite coupling agent and [[2,5-bis(octyloxy)-1,4-phenylene]bis(methylene)]tetraethyl bisphosphate; drying the semi-finished product; mixing the semi-finished product with the grinding aid; and dry grinding to obtain the final product. The calcium powder obtained in this way has a high activation index and a low oil absorption value.

Description

Technical Field

[0001] This application relates to the field of calcium carbonate preparation technology, and more specifically, to a highly dispersible calcium powder and its preparation method. Background Technology

[0002] Calcium carbonate is a widely used inorganic salt, and it is generally classified into heavy calcium carbonate and light calcium carbonate according to different processing methods. Heavy calcium carbonate, also known as ground calcium carbonate, is produced by physical processing of raw materials such as natural limestone and shells; light calcium carbonate is produced by chemical processing.

[0003] Heavy calcium carbonate, due to its wide availability, is widely used as a filler in industries such as plastics and rubber. As heavy calcium carbonate becomes increasingly finer, traditional dry production processes are no longer sufficient in terms of equipment or economic efficiency. Wet grinding processes have emerged to address this need. The biggest difference between wet and dry grinding lies in the dispersion medium. Dry grinding uses air as the dispersion medium, while wet grinding uses water, along with grinding aids, resulting in better particle dispersion, higher grinding efficiency, and finer particle size.

[0004] Due to the inorganic nature of heavy calcium carbonate powder, its compatibility with organic resins is poor, and it is prone to agglomeration. To improve the dispersibility of calcium carbonate particles in polymer matrix materials, thereby enhancing the mechanical properties of calcium carbonate-filled polymer matrix composites and expanding their application in polymer composites, surface modification of calcium carbonate is necessary.

[0005] Currently, the commonly used surface modifiers for modifying heavy calcium carbonate are stearic acid and stearates. However, stearic acid and stearates are mainly adsorbed onto the surface of calcium carbonate particles through physical action, resulting in poor binding force. Consequently, heavy calcium carbonate modified with stearic acid has poor dispersibility.

[0006] Therefore, there is an urgent need to prepare a heavy calcium carbonate with high dispersibility. Summary of the Invention

[0007] To further improve the dispersibility of the prepared calcium carbonate powder, this application provides a highly dispersible calcium powder and its preparation method.

[0008] In a first aspect, this application provides a method for preparing highly dispersible calcium powder, employing the following technical solution:

[0009] A method for preparing highly dispersible calcium powder includes the following steps:

[0010] (1) Preparation of grinding aid: Diethylene glycol, fatty alcohol and alkylsilane are mixed to obtain a premix, and the premix, polyether polyol, stearic acid, stearate and aluminum isopropoxide are mixed to obtain a grinding aid;

[0011] (2) Pre-treated heavy calcium carbonate coarse powder: Mix the heavy calcium carbonate coarse powder with the grinding aid obtained in step (1), and then dry grind it to obtain pre-treated heavy calcium carbonate coarse powder.

[0012] (3) Semi-finished product preparation: Grinding media and grinding aid are mixed to obtain a mixture; pretreated heavy calcium carbonate powder, water and glycerin are mixed to obtain a mixed liquid; the mixture and the mixed liquid are mixed to obtain a primary suspension; the primary suspension is wet-ground to obtain a semi-finished product; the grinding aid is mainly made of the following raw materials in the following weight parts: 4-5 parts of dispersant, 1-2 parts of modifier, 2-3 parts of surfactant, and 0.5-1 parts of auxiliary agent. The modifier includes aluminum-titanium composite coupling agent and [[2,5-bis(octyloxy)-1,4-phenylene]bis(methylene)]tetraethyl bisphosphate. The auxiliary agent is composed of sodium dodecylbenzenesulfonate and mercaptoacetic acid in a mass ratio of (4-5):(1-2).

[0013] (4) Preparation of highly dispersible calcium powder: Dry the semi-finished product, mix the dried semi-finished product with the grinding aid obtained in step (1), and dry grind to obtain the powder.

[0014] By adopting the above technical solution, this application combines dry grinding and wet grinding to further refine the particle size of heavy calcium carbonate. Simultaneously, the addition of a self-made grinding aid during dry grinding reduces the agglomeration of heavy calcium carbonate obtained by dry grinding. The self-made grinding aid enhances the hydrophobicity of heavy calcium carbonate and reduces its oil absorption value. The polar bonds in the grinding aid form anchor points that mix with the heavy calcium carbonate, and the elongated organic ends directionally extend on the surface of the heavy calcium carbonate to form spatial barriers, thereby reducing agglomeration and improving the dispersibility of heavy calcium carbonate. Furthermore, the directional adsorption of polyether polyols on the surface of heavy calcium carbonate gives it nuclear electrical properties and forms a physical and chemical adsorption layer on the surface, further reducing the agglomeration of heavy calcium carbonate particles and improving its dispersibility.

[0015] In wet grinding, grinding aids are introduced to reduce the agglomeration of heavy calcium carbonate during the grinding process, resulting in a smaller particle size of the produced heavy calcium carbonate powder.

[0016] Some grinding aids are adsorbed on the surface of the grinding media, while others are dispersed in the heavy calcium carbonate powder. Under the action of the grinding media, the grinding aids are more evenly distributed on the surface of the coarse heavy calcium carbonate powder. By optimizing and adjusting the raw material components and component ratios in the grinding aids, the grinding aids can play a better role in the grinding of heavy calcium carbonate. The dispersants, modifiers, auxiliary agents, and surfactants in the grinding aids work together to reduce the agglomeration of heavy calcium carbonate.

[0017] The introduction of dispersants facilitates adsorption on the surface of heavy calcium carbonate, reduces the surface energy of heavy calcium carbonate, optimizes the wetting properties of the particle surface, and forms effective steric hindrance between particles to improve repulsive force.

[0018] The addition of additives helps reduce the impact of heat on the dispersibility of heavy calcium carbonate. Simultaneously, the introduced thiol and carboxyl groups work synergistically with the modifier to improve the dispersibility of heavy calcium carbonate. Some additives are adsorbed on the surface of heavy calcium carbonate, while others are adsorbed on the surface of the grinding media. The additives adsorbed on the grinding media surface help reduce the free energy of both the grinding media and the surface of heavy calcium carbonate, increasing the wettability of the particle surface and reducing heat-induced agglomeration of heavy calcium carbonate. The addition of thioglycolic acid in the additives improves the dispersion stability of heavy calcium carbonate, effectively inhibiting the formation and enlargement of particle clusters. This process is beneficial for enhancing the energy transfer process within heavy calcium carbonate. Furthermore, the carboxyl group introduced by thioglycolic acid helps introduce thermally conductive groups, and the thermal conductivity increases with increasing temperature, thus reducing the impact of heat on the dispersibility of calcium carbonate. Sodium dodecylbenzenesulfonate in the auxiliary agent introduces sulfonic acid groups, long-chain alkyl groups, and benzene ring groups, thereby improving the bonding strength with heavy calcium carbonate and increasing the wettability of the particle surface. The introduction of the benzene ring also helps improve the conductivity of the grinding aid. The introduction of benzene sulfonic acid groups in sodium dodecylbenzenesulfonate facilitates interaction with carboxyl groups, further reducing the impact of heat on the dispersibility of calcium carbonate.

[0019] The modifiers added in this application include an aluminum-titanium composite coupling agent and tetraethyl [[2,5-bis(octyloxy)-1,4-phenylene]bis(methylene)]bisphosphate. Tetraethyl [[2,5-bis(octyloxy)-1,4-phenylene]bis(methylene)]bisphosphate contains ester groups, bisphosphate groups, and alkoxy groups. With increasing temperature, the ester and alkoxy groups readily undergo larger group or chain segment vibrations, thereby improving the thermal conductivity of the material. In conjunction with the auxiliary agents, this reduces the impact of heat on the dispersibility of heavy calcium carbonate. The introduction of bisphosphate groups can form multi-point adsorption with the Ca-O groups on the surface of heavy calcium carbonate particles. The coating consists of attachment or bonding points, thus firmly encapsulating the surface of heavy calcium carbonate particles. The hydrophobic alkyl long chains transform the heavy calcium carbonate from hydrophilic to hydrophobic, resulting in high structural stability and reducing the likelihood of agglomeration. The aluminum-titanium composite coupling agent molecule has a dual-center atom, simultaneously possessing low-carbon chain alkoxy and long-carbon chain alkanoyloxy, which facilitates the interaction of calcium carbonate with other organic substances. Furthermore, the easily hydrolyzed alkoxy groups in the aluminum-titanium composite coupling agent molecule react chemically with the free protons on the surface of heavy calcium carbonate, forming a monomolecular film on the surface of heavy calcium carbonate, thereby reducing the agglomeration of calcium carbonate and improving its dispersibility.

[0020] Preferably, the mass ratio of heavy calcium carbonate coarse powder to grinding aid in step (2) is (20-25):(1-2).

[0021] By adopting the above technical solution, the amount of heavy calcium carbonate coarse powder and grinding aid added is adjusted so that the mass ratio of heavy calcium carbonate coarse powder to grinding aid reaches the optimal level. Using the ratio within the scope of this application, it is convenient to further improve the dispersibility of heavy calcium carbonate while reducing the particle size of the heavy calcium carbonate powder fine powder.

[0022] Preferably, the modifier in step (3) is composed of an aluminum-titanium composite coupling agent, [[2,5-bis(octyloxy)-1,4-phenylene]bis(methylene)]tetraethyl bisphosphate, and disodium hexadecyl sulfonylphenoxybenzenesulfonate in a mass ratio of (4-5):(2-3):(2-3).

[0023] By adopting the above technical solution, the modifier is obtained by compounding three components: an aluminum-titanium composite coupling agent, [[2,5-bis(octyloxy)-1,4-phenylene]bis(methylene)]bisphosphonate tetraethyl ester, and disodium hexadecyl sulfonylphenoxybenzenesulfonate. The ratio of the three components is adjusted to achieve the optimal ratio, which facilitates better synergistic effects of the three components, thereby improving the modification effect of the modifier on heavy calcium carbonate and improving the dispersibility of heavy calcium carbonate; among which,

[0024] The aluminum-titanium composite coupling agent interacts with the calcium carbonate surface through covalent bonding. The CO-Ti bonds on the coupling agent open and bond with the -OH bonds on the calcium carbonate surface. Calcium ions on the surface of the calcium carbonate particles come into contact with water molecules in the atmosphere and undergo hydrolysis, producing alkaline hydroxyl groups on the surface. These hydroxyl groups on the calcium carbonate surface bond with the inorganic-loving ends of the aluminum-titanium composite coupling agent, thereby enhancing the activation function of the calcium carbonate.

[0025] The phosphate ester in [[2,5-bis(octyloxy)-1,4-phenylene]bis(methylene)]bis(methylene) tetraethyl phosphate selectively interacts with calcium carbonate in a specific direction to form a spatial network structure; the introduction of phosphate ester facilitates the reduction of friction between calcium carbonate particles, has the effect of aiding grinding, and reduces the substances that cause friction between contacting surfaces, thus reducing the heat generated during surface movement.

[0026] The sulfonate group in disodium hexadecyl sulfonylphenoxybenzenesulfonate is acidic as an anchoring group, which facilitates the reaction with the hydroxyl groups on the surface of calcium carbonate. The sulfonate group enhances the adsorption strength of disodium hexadecyl sulfonylphenoxybenzenesulfonate on the surface of calcium carbonate.

[0027] Preferably, the disodium hexadecyl sulfonylphenoxybenzenesulfonate is a modified disodium hexadecyl sulfonylphenoxybenzenesulfonate, and the preparation method of the modified disodium hexadecyl sulfonylphenoxybenzenesulfonate includes the following steps:

[0028] S1. Disodium hexadecyl sulfonylphenoxybenzenesulfonate is mixed with ethanol to obtain a disodium hexadecyl sulfonylphenoxybenzenesulfonate slurry. The disodium hexadecyl sulfonylphenoxybenzenesulfonate slurry, water, polyethylene glycol, concentrated ammonia, and calcium chloride solution are mixed and stirred. Then carbon dioxide gas is introduced to react. The mixture is filtered and washed with distilled water and dried to obtain intermediate material one.

[0029] S2. The intermediate material one is then calcined to obtain intermediate material two;

[0030] S3. Mix water, sodium bisulfate, and maleic anhydride, then add acrylic acid and ammonium persulfate dropwise and react to obtain intermediate material three;

[0031] S4. Spray intermediate material three onto the surface of intermediate material two and dry it at the same time to obtain pretreated intermediate material two. Immerse pretreated intermediate material two in acrylic emulsion and dry it to obtain modified intermediate material two. Mix modified intermediate material two with coating agent and intermediate material three and dry it to obtain the final product. The coating agent is composed of flake calcium carbonate and polydimethylsiloxane in a mass ratio of (4-5):(1-2).

[0032] By adopting the above technical solution, this application modifies disodium hexadecyl sulfonylphenoxybenzenesulfonate to better exert its modifying effect on calcium carbonate. The process involves coating the surface of disodium hexadecyl sulfonylphenoxybenzenesulfonate with calcium carbonate, followed by calcination of the coating. Then, a polyacrylic acid dispersant is sprayed onto the surface of the calcined calcium carbonate, followed by coating. The modified disodium hexadecyl sulfonylphenoxybenzenesulfonate has a relatively large particle size, facilitating its interaction with the grinding media and accelerating the crushing of coarse heavy calcium carbonate powder. The coating agent on the surface of disodium hexadecyl sulfonylphenoxybenzenesulfonate interacts with other dispersants and surfactants in the grinding aid, adsorbing onto the surface of calcium carbonate during rotation. As the crushing process proceeds, the coating layer on disodium hexadecyl sulfonylphenoxybenzenesulfonate gradually detaches, improving the dispersibility of calcium carbonate and reducing its agglomeration.

[0033] Preferably, the mass ratio of the modified intermediate material II to the coating agent is (1-2):(3-4).

[0034] By adopting the above technical solution, the mass ratio of the modified intermediate material II and the coating agent is adjusted to achieve the optimal mass ratio. Using the ratio of modified intermediate material II to coating agent of this application, the resulting coating layer is not too thick. At the same time, it is easy to completely coat the modified intermediate material II, which facilitates the better performance of the coating agent and allows disodium hexadecyl sulfonylphenoxybenzenesulfonate to play its role layer by layer, thus improving the dispersibility of calcium carbonate.

[0035] Preferably, the flaky calcium carbonate is flaky heavy calcium carbonate.

[0036] By adopting the above technical solution, the use of plate-like heavy calcium carbonate may reduce the sliding friction between particles during the grinding process, play a wetting role, facilitate the interaction with polydimethylsiloxane in the coating agent, thereby reducing the agglomeration generated during the grinding process, improving grinding efficiency, and improving the dispersibility of calcium carbonate.

[0037] Preferably, the dispersant is composed of a polyester dispersant and sodium polyacrylate in a mass ratio of (4-5):(1-2). The preparation method of the polyester dispersant includes the following steps: mixing caprolactone, hexanoic acid, and tetrabutyl titanate, heating, refluxing, reacting, dissolving in ethyl acetate after the reaction, precipitating in petroleum ether to obtain the reactant, mixing the reactant with polyethylene polyamine and toluene, and refluxing under nitrogen protection to obtain the final product.

[0038] By adopting the above technical solution, the dispersant of this application is obtained by compounding two components: a polyester-type dispersant and sodium polyacrylate. The ratio of the two components is adjusted to achieve the optimal ratio. The polyester-type dispersant is a self-made dispersant, which is a "comb-shaped" superdispersant with polyethylene polyamine as the anchoring group. The anchoring group facilitates the grafting of the dispersant onto the calcium carbonate surface, which further improves the steric hindrance of the calcium carbonate surface and reduces the agglomeration of calcium carbonate. Sodium polyacrylate can easily coat the calcium carbonate surface together with the polyester-type dispersant, thereby reducing the surface energy of calcium carbonate, making the calcium carbonate in a stable state, and the particles are relatively dispersed. Even if some calcium carbonate is agglomerated, the agglomeration type is mostly soft agglomeration, which is easily broken under the action of the grinding media.

[0039] Preferably, the grinding media is composed of zirconia ceramic microspheres and alumina ceramic balls in a mass ratio of (3-4):(1-2).

[0040] By adopting the above technical solution, the grinding media is obtained by compounding two components: zirconia ceramic microspheres and alumina ceramic balls. The ratio of the two components is adjusted to better exert the function of the grinding media. At the same time, zirconia ceramic microspheres and alumina ceramic balls have good thermal conductivity, which makes it easy to cooperate with the auxiliary agents to dissipate the heat generated during the grinding process and reduce the problem of poor dispersion of heavy calcium carbonate caused by heat.

[0041] Preferably, the particle size distribution of the grinding media is as follows: 30-40% by mass of 3mm, 50-60% by mass of 1mm, and 10-15% by mass of 0.5mm.

[0042] By adopting the above technical solution, the particle size of the grinding media is adjusted, and multiple particle sizes are used for gradation, which facilitates better grinding of the heavy calcium carbonate particles. At the same time, it makes the grinding range wider, allows the grinding aid to mix better with the heavy calcium carbonate, and improves the dispersibility of the heavy calcium carbonate.

[0043] Secondly, this application provides a highly dispersible calcium powder, which adopts the following technical solution:

[0044] A highly dispersible calcium powder is prepared by the above-mentioned method for preparing highly dispersible calcium powder.

[0045] In summary, this application has the following beneficial effects:

[0046] 1. This application uses a grinding method of first dry grinding, then wet grinding, and finally dry grinding to facilitate the preparation of heavy calcium carbonate with a small particle size. The addition of grinding aids during the dry grinding process helps to reduce the agglomeration of heavy calcium carbonate during grinding and reduces the particle size of the pretreated heavy calcium carbonate powder. Subsequently, the pretreated heavy calcium carbonate is wet ground. The grinding of heavy calcium carbonate with a small particle size helps to reduce the generation of heat. At the same time, the added grinding aids further reduce the agglomeration of heavy calcium carbonate during grinding and further improve the dispersibility of heavy calcium carbonate while reducing the particle size.

[0047] 2. This application adds a grinding aid to wet grinding. The dispersant, modifier, auxiliary agent and surfactant in the grinding aid work together to reduce the agglomeration of heavy calcium carbonate. Detailed Implementation

[0048] The present application will be further described in detail below with reference to the embodiments.

[0049] The processes, conditions, and experimental methods for implementing this invention, except as specifically mentioned below, are all common knowledge and general knowledge in the field. The scope of protection of this invention is not limited to the following embodiments. All variations and advantages that can be conceived by those skilled in the art without departing from the spirit and scope of the inventive concept are included in this invention.

[0050] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application are all commercially available.

[0051] Example of Grinding Aid Preparation

[0052] Preparation Example 1: The grinding aid in this preparation example includes the following raw materials by weight: 4 kg of dispersant, 1 kg of modifier, 2 kg of surfactant, and 0.5 kg of auxiliary agent; the dispersant is sodium polyacrylate, the modifier is composed of aluminum-titanium composite coupling agent and tetraethyl [[2,5-bis(octyloxy)-1,4-phenylene]bis(methylene)]bisphosphate in a mass ratio of 1:1, the surfactant is hexadecyl pyridine chloride, and the auxiliary agent is composed of sodium dodecylbenzenesulfonate and mercaptoacetic acid in a mass ratio of 4:1.

[0053] The preparation method of the grinding aid in this example includes the following steps: mixing the dispersant, modifier, surfactant and auxiliary agent to obtain the desired product.

[0054] Preparation Example 2: The grinding aid in this preparation example differs from that in Preparation Example 1 in that it includes the following raw materials by weight: 5 kg of dispersant, 2 kg of modifier, 3 kg of surfactant, and 1 kg of auxiliary agent; the auxiliary agent is composed of sodium dodecylbenzenesulfonate and mercaptoacetic acid in a mass ratio of 5:2.

[0055] Preparation Example 3: The grinding aid in this preparation example differs from that in Preparation Example 2 in that the modifier is composed of an aluminum-titanium composite coupling agent, [[2,5-bis(octyloxy)-1,4-phenylene]bis(methylene)]tetraethyl bisphosphate, and disodium hexadecyl sulfonylphenoxybenzenesulfonate in a mass ratio of 4:2:2.

[0056] Preparation Example 4: The grinding aid in this preparation example differs from that in Preparation Example 2 in that the modifier is composed of an aluminum-titanium composite coupling agent, [[2,5-bis(octyloxy)-1,4-phenylene]bis(methylene)]tetraethyl bisphosphate, and disodium hexadecyl sulfonylphenoxybenzenesulfonate in a mass ratio of 5:3:3.

[0057] Preparation Example 5: The grinding aid in this preparation example differs from that in Preparation Example 4 in that: disodium hexadecyl sulfonylphenoxybenzenesulfonate is modified disodium hexadecyl sulfonylphenoxybenzenesulfonate. The preparation method of modified disodium hexadecyl sulfonylphenoxybenzenesulfonate includes the following steps:

[0058] S1. Disodium hexadecyl sulfonylphenoxybenzenesulfonate was mixed with ethanol at a mass ratio of 1:30 to obtain a disodium hexadecyl sulfonylphenoxybenzenesulfonate slurry. The disodium hexadecyl sulfonylphenoxybenzenesulfonate slurry, water, polyethylene glycol, concentrated ammonia, and calcium chloride solution were mixed at a mass ratio of 15:80:2:2:0.5 and stirred at 300 r / min. Then, carbon dioxide gas was introduced at a flow rate of 180 mL / min. After reacting for 2 h, the mixture was filtered and washed 10 times with distilled water, and then dried to obtain intermediate material one. The drying temperature was 100℃ and the drying time was 2 h. The weight average molecular weight of the polyethylene glycol was 600.

[0059] S2. The intermediate material 1 is then calcined to obtain intermediate material 2. The calcination process involves placing intermediate material 1 in a muffle furnace and first heating it to 300°C at a heating rate of 8°C / min, then heating it to 400°C at a heating rate of 3°C / min, holding it at 400°C for 2 hours, then cooling it to 350°C at a cooling rate of 3°C / min, and finally cooling it to room temperature at a cooling rate of 8°C / min.

[0060] S3. Mix water, sodium bisulfate, and maleic anhydride, then add acrylic acid and ammonium persulfate dropwise and react to obtain intermediate material three; wherein, the mass ratio of maleic anhydride to acrylic acid is 1:3; the mass ratio of acrylic acid to ammonium persulfate is 1:0.2; the mass ratio of maleic anhydride, water, and sodium bisulfate is 1:20:0.5; and the reaction temperature is 80℃.

[0061] S4. Spray intermediate material three onto the surface of intermediate material two and dry simultaneously to obtain pretreated intermediate material two. The drying temperature is 110℃ and the drying time is 80 min. The mass ratio of intermediate material two to intermediate material three is 3:1. Immerse pretreated intermediate material two in acrylic emulsion for 30 min and dry at 50℃ to obtain modified intermediate material two. Mix modified intermediate material two with coating agent and intermediate material three at a mass ratio of 1:3:4 and dry to obtain the final product. The coating agent is composed of flake calcium carbonate and polydimethylsiloxane at a mass ratio of 4:1; the flake calcium carbonate is flake heavy calcium carbonate.

[0062] Preparation Example 6: The grinding aid in this preparation example differs from that in Preparation Example 5 in that the preparation method of the modified disodium hexadecyl sulfonylphenoxybenzenesulfonate includes the following steps:

[0063] S1. Disodium hexadecyl sulfonylphenoxybenzenesulfonate was mixed with ethanol at a mass ratio of 1:30 to obtain a disodium hexadecyl sulfonylphenoxybenzenesulfonate slurry. The disodium hexadecyl sulfonylphenoxybenzenesulfonate slurry, water, polyethylene glycol, concentrated ammonia, and calcium chloride solution were mixed at a mass ratio of 15:80:2:2:0.5 and stirred at 300 r / min. Then, carbon dioxide gas was introduced at a flow rate of 180 mL / min. After reacting for 2 h, the mixture was filtered and washed 10 times with distilled water, and then dried to obtain intermediate material one. The drying temperature was 100℃ and the drying time was 2 h. The weight average molecular weight of the polyethylene glycol was 600.

[0064] S2. Mix water, sodium bisulfate, and maleic anhydride, then add acrylic acid and ammonium persulfate dropwise and react to obtain intermediate material three; wherein, the mass ratio of maleic anhydride to acrylic acid is 1:3; the mass ratio of acrylic acid to ammonium persulfate is 1:0.2; the mass ratio of maleic anhydride, water, and sodium bisulfate is 1:20:0.5; and the reaction temperature is 80℃.

[0065] S3. Spray intermediate material three onto the surface of intermediate material one and dry simultaneously to obtain pretreated intermediate material one. The drying temperature is 110℃ and the drying time is 80 min. The mass ratio of intermediate material one to intermediate material three is 3:1. Immerse pretreated intermediate material one in acrylic emulsion for 30 min and dry at 50℃ to obtain modified intermediate material one. Mix modified intermediate material one with coating agent and intermediate material three at a mass ratio of 1:3:4 and dry to obtain the final product. The coating agent is composed of flake calcium carbonate and polydimethylsiloxane at a mass ratio of 4:1. The flake calcium carbonate is flake heavy calcium carbonate.

[0066] Preparation Example 7: The grinding aid in this preparation example differs from that in Preparation Example 5 in that the preparation method of the modified disodium hexadecyl sulfonylphenoxybenzenesulfonate includes the following steps:

[0067] S1. Disodium hexadecyl sulfonylphenoxybenzenesulfonate was mixed with ethanol at a mass ratio of 1:30 to obtain a disodium hexadecyl sulfonylphenoxybenzenesulfonate slurry. The disodium hexadecyl sulfonylphenoxybenzenesulfonate slurry, water, polyethylene glycol, concentrated ammonia, and calcium chloride solution were mixed at a mass ratio of 15:80:2:2:0.5 and stirred at 300 r / min. Then, carbon dioxide gas was introduced at a flow rate of 180 mL / min. After reacting for 2 h, the mixture was filtered and washed 10 times with distilled water, and then dried to obtain intermediate material one. The drying temperature was 100℃ and the drying time was 2 h. The weight average molecular weight of the polyethylene glycol was 600.

[0068] S2. The intermediate material 1 is then calcined to obtain intermediate material 2. The calcination process involves placing intermediate material 1 in a muffle furnace and first heating it to 300°C at a heating rate of 8°C / min, then heating it to 400°C at a heating rate of 3°C / min, holding it at 400°C for 2 hours, then cooling it to 350°C at a cooling rate of 3°C / min, and finally cooling it to room temperature at a cooling rate of 8°C / min.

[0069] S3. Immerse intermediate material two in acrylic emulsion for 30 minutes, then dry at 50°C to obtain modified intermediate material two. Mix modified intermediate material two with a coating agent at a mass ratio of 1:3 and dry to obtain the final product. The coating agent consists of flake calcium carbonate and polydimethylsiloxane at a mass ratio of 4:1. The flake calcium carbonate is flake heavy calcium carbonate.

[0070] Preparation Example 8: The grinding aid in this preparation example differs from that in Preparation Example 5 in that the preparation method of the modified disodium hexadecyl sulfonylphenoxybenzenesulfonate includes the following steps:

[0071] S1. Disodium hexadecyl sulfonylphenoxybenzenesulfonate was mixed with ethanol at a mass ratio of 1:30 to obtain a disodium hexadecyl sulfonylphenoxybenzenesulfonate slurry. The disodium hexadecyl sulfonylphenoxybenzenesulfonate slurry, water, polyethylene glycol, concentrated ammonia, and calcium chloride solution were mixed at a mass ratio of 15:80:2:2:0.5 and stirred at 300 r / min. Then, carbon dioxide gas was introduced at a flow rate of 180 mL / min. After reacting for 2 h, the mixture was filtered and washed 10 times with distilled water, and then dried to obtain intermediate material one. The drying temperature was 100℃ and the drying time was 2 h. The weight average molecular weight of the polyethylene glycol was 600.

[0072] S2. The intermediate material 1 is then calcined to obtain intermediate material 2. The calcination process involves placing intermediate material 1 in a muffle furnace and first heating it to 300°C at a heating rate of 8°C / min, then heating it to 400°C at a heating rate of 3°C / min, holding it at 400°C for 2 hours, then cooling it to 350°C at a cooling rate of 3°C / min, and finally cooling it to room temperature at a cooling rate of 8°C / min.

[0073] S3. Mix water, sodium bisulfate, and maleic anhydride, then add acrylic acid and ammonium persulfate dropwise and react to obtain intermediate material three; wherein, the mass ratio of maleic anhydride to acrylic acid is 1:3; the mass ratio of acrylic acid to ammonium persulfate is 1:0.2; the mass ratio of maleic anhydride, water, and sodium bisulfate is 1:20:0.5; and the reaction temperature is 80℃.

[0074] S4. Spray intermediate material 3 onto the surface of intermediate material 2 and dry it at the same time to obtain pretreated intermediate material 2. The drying temperature is 110℃ and the drying time is 80min. The mass ratio of intermediate material 2 to intermediate material 3 is 3:1.

[0075] Preparation Example 9: The grinding aid in this preparation example differs from that in Preparation Example 1 in that the dispersant is composed of a polyester-type dispersant and sodium polyacrylate in a mass ratio of 5:2. The preparation method of the polyester-type dispersant includes the following steps: caprolactone, hexanoic acid, and tetrabutyl titanate are mixed in a mass ratio of 20:6:1, heated to 150°C under nitrogen protection, refluxed, and reacted. After the reaction is completed, ethyl acetate is dissolved and petroleum ether is precipitated to obtain the reactant. The reactant is mixed with polyethylene polyamine and toluene in a mass ratio of 10:3:0.3, refluxed at 150°C for 6 hours under nitrogen protection, and excess toluene is removed after the reaction is completed to obtain the final product.

[0076] Preparation Example 10: The grinding aid in this preparation example differs from that in Preparation Example 1 in that the grinding aid is a silane coupling agent.

[0077] Preparation Example 11: The grinding aid in this preparation example differs from that in Preparation Example 1 in that a modifier is used to replace the auxiliary agent in an equal amount.

[0078] Preparation Example 12: The grinding aid in this preparation example differs from that in Preparation Example 1 in that the modifier is replaced by an auxiliary agent in equal amounts.

[0079] Example

[0080] Example 1: The preparation method of highly dispersible calcium powder in this example includes the following steps:

[0081] (1) Preparation of grinding aid: Diethylene glycol, fatty alcohol and alkylsilane are mixed in a mass ratio of 10:8:1 to obtain a premix. The premix, polyether polyol, stearic acid, stearate and aluminum isopropoxide are mixed in a mass ratio of 5:3:3:1 to obtain the grinding aid. The mixing temperature is 80℃. The stearate is sodium stearate and the fatty alcohol is dodecyl alcohol.

[0082] (2) Pre-treated heavy calcium carbonate coarse powder: The heavy calcium carbonate coarse powder is mixed with the grinding aid obtained in step (1), and then dry-ground to obtain pre-treated heavy calcium carbonate coarse powder; the mass ratio of heavy calcium carbonate coarse powder to grinding aid is 20:1.

[0083] (3) Semi-finished product preparation: The grinding media and grinding aid are mixed at a mass ratio of 1:3 to obtain a mixture; the pretreated heavy calcium carbonate coarse powder, water, and glycerol are mixed at a mass ratio of 25:10:1 to obtain a mixed liquid; the mixture and the mixed liquid are mixed at a mass ratio of 3:25 to obtain a primary suspension; the primary suspension is subjected to wet grinding to obtain a semi-finished product; the grinding aid is prepared in Preparation Example 1; wherein, the grinding media is composed of zirconia ceramic microspheres and alumina ceramic balls at a mass ratio of 3:1. The particle size of the grinding media is 2 mm; the particle size of the heavy calcium carbonate coarse powder is 500 mesh; the grinding temperature of wet grinding is 45℃, the grinding speed is 1800 r / min, and the slurry flow rate is 3 t / h;

[0084] (4) Preparation of highly dispersible calcium powder: Dry the semi-finished product, mix the semi-finished product with the grinding aid obtained in step (1) at a mass ratio of 20:1, and dry grind it to obtain the powder. The drying temperature is 140℃ and the drying time is 5h. Spray drying is used for drying.

[0085] The highly dispersible calcium powder in this embodiment was prepared using the above-described preparation method.

[0086] Table 1 Grinding aids for highly dispersible calcium powders in Examples 1-9

[0087]

[0088] Example 2: The highly dispersible calcium powder of this example uses the grinding aids shown in Table 1. The difference from Example 1 is that the grinding aids are prepared in Preparation Example 2; the grinding media are composed of zirconia ceramic microspheres and alumina ceramic balls in a mass ratio of 5:2; and the mass ratio of heavy calcium carbonate coarse powder to grinding aid is 25:2.

[0089] Examples 3-9: The grinding aids used in the highly dispersible calcium powder of this example are shown in Table 1. The difference from Example 1 is that the preparation method of the grinding aids is different.

[0090] Example 10: The high dispersibility calcium powder in this example differs from that in Example 1 in that the particle size distribution of the grinding media is as follows: 30% by mass of 3mm, 55% by mass of 1mm, and 15% by mass of 0.5mm.

[0091] Comparative Example

[0092] Comparative Example 1: The high dispersibility calcium powder in this comparative example differs from that in Example 1 in that the grinding aid was prepared using Preparation Example 10.

[0093] Comparative Example 2: The high dispersibility calcium powder in this comparative example differs from that in Example 1 in that the grinding aid was prepared using Preparation Example 11.

[0094] Comparative Example 3: The high dispersibility calcium powder in this comparative example differs from that in Example 1 in that the grinding aid was prepared using Preparation Example 12.

[0095] Performance testing

[0096] Oil absorption value test: The highly dispersible calcium powders prepared in Examples 1-10 and Comparative Examples 1-3 were tested for their oil absorption value. The test method includes the following steps:

[0097] (1) Before testing, place the sample to be tested in an oven to dry for 40 minutes, then take it out and place it in a sealed container with desiccant to cool to room temperature;

[0098] (2) Weigh the dried and cooled sample (generally weigh 1.000g), with a mass accuracy of 0.0005g. Place the weighed sample on a clean glass plate with an area of ​​not less than 200mm×200mm, and then use an acid burette with an accuracy of Grade A to dispense the grease (dibutyl phthalate);

[0099] (3) While slowly adding the oil to the sample using an acid burette, continuously stir with a glass rod to ensure that the sample and oil are mixed evenly. The endpoint of the test is: when the last drop is added, the sample and oil just clump together, with no free dry sample remaining.

[0100] The formula for calculating the oil absorption value is: A0 = V / M (mL / g);

[0101] Where A0 is the oil absorption value; V is the volume of the oil used; and M is the mass of the sample. The test results are shown in Table 2.

[0102] Activation index performance test: Highly dispersible calcium powder prepared in Examples 1-10 and Comparative Examples 1-3 was tested using the following steps: 100 mL of water was measured using a graduated cylinder and added to a 125 mL separatory funnel. 1 g of the highly dispersible calcium powder was added to the funnel, the mixture was shaken up and down, and allowed to stand for 0.5 h. Then, the stopcock was opened to release the sample that had settled at the bottom. The sample was dried, weighed, and the mass of the floating portion was obtained by subtracting the mass of the settled sample from the original mass of 1 g. The formula for calculating the activation index is:

[0103] Activation index = (mass of sample in suspension / total mass of sample) × 100%;

[0104] The activation index results are shown in Table 2.

[0105] Particle size test: The highly dispersible calcium powders prepared in Examples 1-10 were tested using a laser particle size analyzer to detect the content of particles smaller than 2 μm. The content of particles smaller than 2 μm in the highly dispersible calcium powders prepared in each example of this application is >90%.

[0106] Table 2. Performance test results of highly dispersible calcium powders in Examples 1-10 and Comparative Examples 1-3

[0107]

[0108] Based on the data in Example 1, Comparative Example 1, and Table 2, it can be seen that the highly dispersible calcium powder of Example 1 has a higher activity index and a lower oil absorption value. The difference between Example 1 and Comparative Example 1 is that Example 1 uses a self-made grinding aid. This application believes that using a self-made grinding aid, in which raw materials such as alkylsilane and polyether polyol are added during the preparation process, can help to further improve the dispersion performance of the obtained highly dispersible calcium powder.

[0109] Based on Example 1, Comparative Examples 2-3, and the data in Table 2, it can be seen that the activity index and oil absorption value of the highly dispersible calcium powder in Example 1 are better than those in Comparative Examples 2-3. The difference between Example 1 and Comparative Examples 2-3 is that Example 1 simultaneously added an auxiliary agent and a modifier. This application believes that when an auxiliary agent and a modifier are added simultaneously during the preparation of highly dispersible calcium powder, the auxiliary agent and the modifier work together synergistically to further improve the dispersibility of the highly dispersible calcium powder. Simply increasing the quality of the modifier and the auxiliary agent cannot improve the dispersibility of the highly dispersible calcium powder. The ratio of each component of the grinding aid has a significant impact on the dispersibility of the highly dispersible calcium powder.

[0110] Based on Examples 1-2 and the data in Table 2, it can be seen that the highly dispersible calcium powder of Examples 1-2 has a higher activity index and a lower oil absorption value. This application believes that using the grinding aid of this application to treat the coarse powder of heavy calcium carbonate can, on the one hand, reduce the particle size of heavy calcium carbonate, and on the other hand, improve the dispersibility of heavy calcium carbonate.

[0111] Based on Examples 2-4 and the data in Table 2, it can be seen that the highly dispersible calcium powder of Examples 3-4 has better dispersibility. The difference between Examples 3-4 and Example 2 is that the modifier in Examples 3-4 is a compound of three components: aluminum-titanium composite coupling agent, [[2,5-bis(octyloxy)-1,4-phenylene]bis(methylene)]tetraethyl bisphosphate, and disodium hexadecyl sulfonylphenoxybenzenesulfonate. This application believes that when the modifier is a compound of three components: aluminum-titanium composite coupling agent, [[2,5-bis(octyloxy)-1,4-phenylene]bis(methylene)]tetraethyl bisphosphate, and disodium hexadecyl sulfonylphenoxybenzenesulfonate, the three components work together to further improve the dispersibility of the highly dispersible calcium powder.

[0112] Based on Examples 4-5 and the data in Table 2, it can be seen that the activity index and oil absorption value of the highly dispersible calcium powder in Example 5 are better than those in Example 4. The difference between Example 5 and Example 4 is that Example 5 treats the disodium hexadecyl sulfonylphenoxybenzenesulfonate in the modifier. This application believes that by treating the disodium hexadecyl sulfonylphenoxybenzenesulfonate, calcium carbonate is coated on the outside of the disodium hexadecyl sulfonylphenoxybenzenesulfonate. Then, the coated calcium carbonate is calcined to further improve the hardness of the calcium carbonate. Subsequently, flake calcium carbonate and polydimethylsiloxane are coated on the surface of the calcium carbonate. Thus, the modified disodium hexadecyl sulfonylphenoxybenzenesulfonate helps to significantly improve the dispersibility of the highly dispersible calcium powder.

[0113] Based on Examples 5-8 and the data in Table 2, it can be seen that the dispersibility of the highly dispersible calcium powder in Example 5 is better than that in Examples 6-8. Different treatment methods are used to treat disodium hexadecyl sulfonylphenoxybenzenesulfonate, resulting in different dispersibility of the highly dispersible calcium powder. The highly dispersible calcium powder prepared by the treatment method of this application has better dispersibility.

[0114] Based on Examples 1 and 9, and the data in Table 2, it can be seen that the activity index and oil absorption value of the highly dispersible calcium powder of Example 9 are better than those of the highly dispersible calcium powder of Example 1. The difference between Example 9 and Example 1 is that the dispersant used in Example 9 is a self-made dispersant. The addition of the self-made dispersant results in better dispersibility of the highly dispersible calcium powder.

[0115] Based on Examples 1 and 10, and the data in Table 2, it can be seen that the highly dispersible calcium powder of Example 10 has better dispersibility. The difference between Example 10 and Example 1 is that the grinding media in Example 10 has a different particle size. This application believes that the highly dispersible calcium powder obtained by using multiple particle size distributions has better dispersibility.

[0116] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing highly dispersible calcium powder, characterized in that, Includes the following steps: (1) Preparation of grinding aid: Diethylene glycol, fatty alcohol and alkylsilane are mixed to obtain a premix, and the premix, polyether polyol, stearic acid, stearate and aluminum isopropoxide are mixed to obtain a grinding aid; (2) Pre-treated heavy calcium carbonate coarse powder: Mix the heavy calcium carbonate coarse powder with the grinding aid obtained in step (1), and then dry grind it to obtain pre-treated heavy calcium carbonate coarse powder. (3) Semi-finished product preparation: Grinding media and grinding aid are mixed to obtain a mixture; pretreated heavy calcium carbonate powder, water and glycerin are mixed to obtain a mixed liquid; the mixture and the mixed liquid are mixed to obtain a primary suspension; the primary suspension is wet-ground to obtain a semi-finished product; the grinding aid is mainly made of the following raw materials in the following weight parts: 4-5 parts of dispersant, 1-2 parts of modifier, 2-3 parts of surfactant, and 0.5-1 parts of auxiliary agent. The modifier includes aluminum-titanium composite coupling agent and [[2,5-bis(octyloxy)-1,4-phenylene]bis(methylene)]tetraethyl bisphosphate. The auxiliary agent is composed of sodium dodecylbenzenesulfonate and mercaptoacetic acid in a mass ratio of (4-5):(1-2). (4) Preparation of highly dispersible calcium powder: Dry the semi-finished product, mix the dried semi-finished product with the grinding aid obtained in step (1), and dry grind to obtain the powder.

2. The method for preparing highly dispersible calcium powder according to claim 1, characterized in that, The mass ratio of heavy calcium carbonate coarse powder to grinding aid in step (2) is (20-25):(1-2).

3. The method for preparing highly dispersible calcium powder according to claim 1, characterized in that, The modifier in step (3) is composed of aluminum-titanium composite coupling agent, [[2,5-bis(octyloxy)-1,4-phenylene]bis(methylene)]tetraethyl bisphosphate, and disodium hexadecyl sulfonylphenoxybenzenesulfonate in a mass ratio of (4-5):(2-3):(2-3).

4. The method for preparing highly dispersible calcium powder according to claim 3, characterized in that, The disodium hexadecylsulfonylphenoxybenzenesulfonate is a modified disodium hexadecylsulfonylphenoxybenzenesulfonate, and the preparation method of the modified disodium hexadecylsulfonylphenoxybenzenesulfonate includes the following steps: S1. Disodium hexadecyl sulfonylphenoxybenzenesulfonate is mixed with ethanol to obtain a disodium hexadecyl sulfonylphenoxybenzenesulfonate slurry. The disodium hexadecyl sulfonylphenoxybenzenesulfonate slurry, water, polyethylene glycol, concentrated ammonia, and calcium chloride solution are mixed and stirred. Then carbon dioxide gas is introduced to react. The mixture is filtered and washed with distilled water and dried to obtain intermediate material one. S2. Intermediate material one is then calcined to obtain intermediate material two; S3. Mix water, sodium bisulfate, and maleic anhydride, then add acrylic acid and ammonium persulfate dropwise and react to obtain intermediate material three; S4. Spray intermediate material three onto the surface of intermediate material two and dry it at the same time to obtain pretreated intermediate material two. Immerse pretreated intermediate material two in acrylic emulsion and dry it to obtain modified intermediate material two. Mix modified intermediate material two with coating agent and intermediate material three and dry it to obtain the final product. The coating agent is composed of flake calcium carbonate and polydimethylsiloxane in a mass ratio of (4-5):(1-2).

5. The method for preparing highly dispersible calcium powder according to claim 4, characterized in that, The mass ratio of the modified intermediate material II to the coating agent is (1-2):(3-4).

6. The method for preparing highly dispersible calcium powder according to claim 4, characterized in that, The flaky calcium carbonate is flaky heavy calcium carbonate.

7. The method for preparing highly dispersible calcium powder according to claim 1, characterized in that, The dispersant is composed of a polyester dispersant and sodium polyacrylate in a mass ratio of (4-5):(1-2). The preparation method of the polyester dispersant includes the following steps: mixing caprolactone, hexanoic acid, and tetrabutyl titanate, heating, refluxing, and reacting. After the reaction is completed, ethyl acetate is dissolved and petroleum ether is precipitated to obtain the reactant. The reactant is mixed with polyethylene polyamine and toluene, and the mixture is refluxed under nitrogen protection to obtain the final product.

8. The method for preparing highly dispersible calcium powder according to claim 1, characterized in that, The grinding media consists of zirconia ceramic microspheres and alumina ceramic balls in a mass ratio of (3-5):(1-2).

9. The method for preparing highly dispersible calcium powder according to claim 1, characterized in that, The grinding media have a particle size distribution of 30-40% by mass for 3mm particles, 50-60% by mass for 1mm particles, and 10-15% by mass for 0.5mm particles.

10. A highly dispersible calcium powder, characterized in that: It is prepared by the method of any one of claims 1-9 for preparing highly dispersible calcium powder.

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