Grinding aids, methods of making and using the same

Abstract

The application relates to a grinding aid and a preparation method and application thereof, the grinding aid comprising a to-be-treated solution and a surfactant; the to-be-treated solution contains sodium acrylate, sodium hydroxide and sodium p-toluenesulfonate; and the surfactant comprises at least one of sodium dodecyl benzene sulfonate, sodium lignosulfonate, allyl polyether, fatty alcohol polyoxyethylene ether, alkyl phenol polyoxyethylene ether and nonyl phenol polyoxyethylene ether. The specific surfactant in the grinding aid cooperates with the to-be-treated solution, synergistically improves the interface wetting performance of the material, weakens the powder aggregation phenomenon, reduces the surface energy, and further improves the dispersibility of the material and the gradation and fluidity of the material.

Description

Technical Field

[0001] This application relates to the field of wastewater resource utilization technology, and in particular to a grinding aid, its preparation method, and its application. Background Technology

[0002] Calcium carbonate is the most common filler in powder coatings. In recent years, with the improvement of ultrafine calcium carbonate, complex structure, and surface modification technology, calcium carbonate products have tended towards specialization, refinement, and functionalization, and the particle size requirements have become increasingly stringent with process improvements. During the crushing process, calcium carbonate stone undergoes a cycle of crack formation, crack propagation, crack fracture, and then crack formation again. When the molecular force increases to a certain extent, the material begins to agglomerate until a dynamic equilibrium between crushing and agglomeration is reached, at which point the particle size no longer changes. Adding appropriate grinding aids is one of the effective methods to break the dynamic equilibrium between crushing and agglomeration without changing the grinding equipment and production process.

[0003] Traditional grinding aids mainly include inorganic grinding aids (such as sodium hexametaphosphate and sodium tripolyphosphate), organic grinding aids (such as ethylene glycol and triethanolamine), and polymeric grinding aids (such as polycarboxylate and polyacrylic acid derivatives). Traditional grinding aids have poor adaptability and stability, low grinding efficiency, and the particle size distribution and flowability of the ground materials cannot meet the increasingly demanding requirements of powder coating materials. Summary of the Invention

[0004] Therefore, it is necessary to provide grinding aids that can improve the particle size distribution and flowability of materials, as well as their preparation methods and applications.

[0005] One aspect of this application provides a grinding aid comprising a solution to be treated and a surfactant; the solution to be treated contains sodium acrylate, sodium hydroxide, and sodium p-toluenesulfonate; the surfactant comprises at least one selected from sodium dodecylbenzenesulfonate, sodium lignin sulfonate, allyl polyether, fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, and nonylphenol polyoxyethylene ether.

[0006] This application describes a grinding aid formulated by compounding a specific surfactant with a solution containing sodium acrylate, sodium hydroxide, and sodium p-toluenesulfonate. The specific surfactant and the solution work synergistically to significantly improve the interfacial wetting properties of the material, reduce powder agglomeration, lower surface energy, and thus enhance the dispersibility, gradation, and flowability of the material. Sodium acrylate in the solution promotes the dissolution or transformation of the ground material; sodium p-toluenesulfonate not only has good surface activity but also adsorbs onto the surface of the ground material particles, using electrostatic repulsion to maintain the dispersibility and stability of the grinding slurry; sodium hydroxide acts as a pH adjuster, altering the charge properties and quantity on the particle surface and improving particle dispersibility; and the compounding of the specific surfactant with the solution significantly improves the dispersibility, interfacial wetting, emulsification, and stability of the ground material.

[0007] Sodium dodecylbenzenesulfonate has a regular structure, strong dispersibility and surface activity, which can effectively prevent particle agglomeration and is less affected by external interference factors. Sodium lignosulfonate has good dispersibility and is not prone to agglomeration. The sulfonic acid groups in the structure of sodium dodecylbenzenesulfonate or sodium lignosulfonate will ionize in aqueous solution, causing the particle surface to carry the same charge and repel each other. When the particles are subjected to grinding force, cracks will be generated. Sodium dodecylbenzenesulfonate or sodium lignosulfonate, in combination with sodium acrylate and sodium toluenesulfonate in the solution to be treated, can not only accelerate the formation of cracks, but also prevent the healing of cracks, reduce powder agglomeration, and improve the grinding effect.

[0008] The molecular chain structure of allyl polyether gives it good dispersibility and large steric hindrance, providing a large number of reactive sites. It reacts with sodium acrylate, sodium toluenesulfonate and sodium hydroxide in the solution to be treated to undergo polymerization, cross-linking and other reactions, which helps to improve the overall strength and stability of the grinding slurry and reduce agglomeration.

[0009] When fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, and nonylphenol polyoxyethylene ether are combined with sodium acrylate, sodium toluenesulfonate, and sodium hydroxide in the solution to be treated and used to grind slurry, they all exhibit excellent wettability, emulsification, and dispersibility. During grinding, they can reduce the surface tension between particles and slurry, allowing particles to be better dispersed in the slurry and preventing particle agglomeration.

[0010] The above-mentioned grinding aids can reduce the viscosity of materials ground in wet processes, prevent material stratification, and thus improve the stability of the materials.

[0011] The material ground with the above-mentioned grinding aid has fewer aggregated particles, less friction between particles, more compact packing, better overall performance such as oil absorption and activation, and longer performance.

[0012] The above-mentioned grinding aids improve material grinding efficiency, reduce grinding energy consumption, and are inexpensive, resulting in good economic and environmental benefits.

[0013] In some embodiments, the mass ratio of the solution to be treated to the surfactant is 1:0.08~0.39.

[0014] In some embodiments, the grinding aid satisfies at least one of the following conditions:

[0015] (1) The surfactant comprises the sodium dodecylbenzenesulfonate and the allyl polyether;

[0016] (2) The surfactant includes the sodium lignosulfonate and the alkylphenol polyoxyethylene ether.

[0017] In some embodiments, the grinding aid satisfies at least one of the following conditions:

[0018] (1) The mass ratio of the solution to be treated, the sodium dodecylbenzenesulfonate, and the allyl polyether is 1:0.1~0.32:0.04~0.1;

[0019] (2) The mass ratio of the solution to be treated, the sodium lignosulfonate and the alkylphenol polyoxyethylene ether is 1:0.12~0.33:0.025~0.08.

[0020] In some embodiments, the solution to be treated is wastewater from the production of acrylic acid and its esters, the solid content of the wastewater is 30% to 50%, the mass content of sodium acrylate in the wastewater is 15% to 37%, the mass content of sodium hydroxide in the wastewater is 0.3% to 13%, and the mass content of sodium p-toluenesulfonate in the wastewater is 0.3% to 5%.

[0021] A second aspect of this application provides a method for preparing a grinding aid as described in the first aspect, comprising the following steps: blending the solution to be treated and the surfactant to obtain the grinding aid.

[0022] In some embodiments, the method for preparing the grinding aid satisfies at least one of the following conditions:

[0023] (1) The solution to be treated is acrylic acid and its ester production wastewater. Before the blending, a concentration step is also included: the acrylic acid and its ester production wastewater with a solid content of 2% to 20% is concentrated into the acrylic acid and its ester production wastewater with a solid content of 30% to 50% by mass content.

[0024] (2) The blending temperature of the blend is 40°C ~ 50°C.

[0025] A third aspect of this application provides the application of the grinding aid as described in the first aspect in a grinding process.

[0026] In some embodiments, the application of the grinding aid in the grinding process includes the following steps:

[0027] Calcium carbonate coarse powder is wet-milled with the aforementioned grinding aid and water to obtain calcium carbonate slurry.

[0028] In some embodiments, the application of the grinding aid in the grinding process satisfies at least one of the following conditions:

[0029] (1) The amount of the grinding aid added is 0.2% to 0.5% of the mass of the coarse calcium carbonate powder;

[0030] (2) The average particle size of the coarse calcium carbonate powder is 250 mesh to 500 mesh;

[0031] (3) The grinding time of the wet grinding is 25 min to 45 min. Detailed Implementation

[0032] To facilitate understanding of the present invention, a more complete description will be given below with reference to relevant embodiments, wherein preferred embodiments of the invention are provided. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that a thorough and complete understanding of the disclosure of the present invention will be achieved.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0034] Fillers in powder coatings not only reduce costs but also improve material properties. Calcium carbonate is one of the most common fillers in powder coatings. In recent years, with the development of ultrafine calcium carbonate, complex structures, and surface modification technologies, calcium carbonate filler products have become increasingly specialized, refined, and functional, leading to higher requirements for particle size. Therefore, technicians have attempted to address this issue by adding grinding aids to the grinding process. However, traditional grinding aids suffer from poor adaptability and stability, low grinding efficiency, and the particle size distribution and flowability of the ground materials cannot meet the increasingly stringent requirements for powder coating materials. Based on this, one aspect of this application provides a grinding aid comprising a solution to be treated and a surfactant; the solution to be treated contains sodium acrylate, sodium hydroxide, and sodium p-toluenesulfonate; the surfactant comprises at least one of sodium dodecylbenzenesulfonate, sodium lignosulfonate, allyl polyether, fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, and nonylphenol polyoxyethylene ether.

[0035] This application describes a grinding aid formulated by compounding a specific surfactant with a solution containing sodium acrylate, sodium hydroxide, and sodium p-toluenesulfonate. The specific surfactant and the solution work synergistically to significantly improve the interfacial wetting properties of the material, reduce powder agglomeration, lower surface energy, and thus enhance the dispersibility, gradation, and flowability of the material. Sodium acrylate in the solution promotes the dissolution or transformation of the ground material; sodium p-toluenesulfonate not only has good surface activity but also adsorbs onto the surface of the ground material particles, using electrostatic repulsion to maintain the dispersibility and stability of the grinding slurry; sodium hydroxide acts as a pH adjuster, altering the charge properties and quantity on the particle surface and improving particle dispersibility; and the compounding of the specific surfactant with the solution significantly improves the dispersibility, interfacial wetting, emulsification, and stability of the ground material.

[0036] Sodium dodecylbenzenesulfonate has a regular structure, strong dispersibility and surface activity, which can effectively prevent particle agglomeration and is less affected by external interference factors. Sodium lignosulfonate has good dispersibility and is not prone to agglomeration. The sulfonic acid groups in the structure of sodium dodecylbenzenesulfonate or sodium lignosulfonate will ionize in aqueous solution, causing the particle surface to carry the same charge and repel each other. When the particles are subjected to grinding force, cracks will be generated. Sodium dodecylbenzenesulfonate or sodium lignosulfonate, in combination with sodium acrylate and sodium toluenesulfonate in the solution to be treated, can not only accelerate the formation of cracks, but also prevent the healing of cracks, reduce powder agglomeration, and improve the grinding effect.

[0037] The molecular chain structure of allyl polyether gives it good dispersibility and large steric hindrance, providing a large number of reactive sites. It reacts with sodium acrylate, sodium toluenesulfonate and sodium hydroxide in the solution to be treated to undergo polymerization, cross-linking and other reactions, which helps to improve the overall strength and stability of the grinding slurry and reduce agglomeration.

[0038] When fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, and nonylphenol polyoxyethylene ether are combined with sodium acrylate, sodium toluenesulfonate, and sodium hydroxide in the solution to be treated and used to grind slurry, they all exhibit excellent wettability, emulsification, and dispersibility. During grinding, they can reduce the surface tension between particles and slurry, allowing particles to be better dispersed in the slurry and preventing particle agglomeration.

[0039] The above-mentioned grinding aids can reduce the viscosity of materials ground in wet processes, prevent material stratification, and thus improve the stability of the materials.

[0040] The material ground with the above-mentioned grinding aid has fewer aggregated particles, less friction between particles, more compact packing, better overall performance such as oil absorption and activation, and longer performance.

[0041] The above-mentioned grinding aids improve material grinding efficiency, reduce grinding energy consumption, and are inexpensive, resulting in good economic and environmental benefits.

[0042] Understandably, the solution to be treated can be a mixed solution containing sodium acrylate, sodium hydroxide and sodium p-toluenesulfonate.

[0043] In some embodiments, the solution to be treated is saline wastewater containing sodium acrylate, sodium hydroxide, and sodium p-toluenesulfonate.

[0044] In some embodiments, the solution to be treated is a mixture of three types of wastewater: wastewater containing sodium acrylate, wastewater containing sodium hydroxide, and saline wastewater containing sodium toluenesulfonate.

[0045] In some embodiments, the solution to be treated is a mixed solution obtained by dissolving sodium acrylate, sodium hydroxide and sodium p-toluenesulfonate in water.

[0046] Furthermore, in the solution to be treated, the solid content is 30%~50%, the mass content of sodium acrylate is 15%~37%, the mass content of sodium hydroxide is 0.3%~13%, and the mass content of sodium p-toluenesulfonate is 0.3%~5%.

[0047] In some embodiments, the solution to be treated is wastewater from the production of acrylic acid and its esters. This application combines a specific surfactant with the wastewater from the production of acrylic acid and its esters containing sodium acrylate, sodium hydroxide, and sodium p-toluenesulfonate to form a grinding aid. This not only improves the dispersibility of the material being ground, enhancing its gradation and flowability, but also enables the resource utilization of wastewater, reducing pollution and bringing environmental benefits.

[0048] Understandably, when producing acrylic acid and its esters by esterification of acrylic acid and alcohols, a slight excess of acrylic acid is generally used to ensure the selectivity and conversion rate of the reaction. Therefore, at the end of the reaction, the reaction apparatus needs to be cleaned with a low-concentration alkaline solution to prevent excess acrylic acid from entering the separation section and causing corrosion to the equipment. However, the cleaning process generates a large amount of alkaline washing wastewater containing salts, sodium acrylate, sodium hydroxide, and sodium p-toluenesulfonate (residual catalyst). Acrylic acid and its esters are a general term for esters of acrylic acid and its homologues, including methyl acrylate, ethyl acrylate, methyl 2-methacrylate, and ethyl 2-methacrylate. Depending on the actual situation, the components of this alkaline washing wastewater can be concentrated to the required mass content through triple-effect evaporation, thus obtaining the aforementioned acrylic acid and its ester production wastewater. Furthermore, the unconcentrated alkaline washing wastewater is also applicable to this application.

[0049] In some embodiments, the solution to be treated is wastewater from the production of acrylic acid and its esters, which contains sodium acrylate, sodium hydroxide, and sodium p-toluenesulfonate; the solid content of the wastewater is 30% to 50%, the mass content of sodium acrylate in the wastewater is 15% to 37%, the mass content of sodium hydroxide in the wastewater is 0.3% to 13%, and the mass content of sodium p-toluenesulfonate in the wastewater is 0.3% to 5%.

[0050] In some embodiments, the mass ratio of the solution to be treated to the surfactant is 1:0.08~0.39.

[0051] As an example, the mass ratio of the solution to be treated to the surfactant can be 1:0.08, 1:0.09, 1:0.10, 1:0.11, 1:0.12, 1:0.13, 1:0.14, 1:0.15, 1:0.16, 1:0.17, 1:0.18, 1:0.19, 1:0.20, 1:0.21, 1:0.22, or 1:0. 23, 1:0.24, 1:0.25, 1:0.26, 1:0.27, 1:0.28, 1:0.29, 1:0.30, 1:0.31, 1:0.32, 1:0.33, 1:0.34, 1:0.35, 1:0.36, 1:0.37, 1:0.38, and 1:0.39, or any two of the above values ​​as endpoints within the range. At this mass ratio of the solution to be treated and the surfactant, the gradation of the ground material can be further optimized, the D50 of the material can be reduced, the particle size below 2 μm can be increased, and the flowability, stability, oil absorption, and activation of the material can be improved.

[0052] The preferred mass ratio of the solution to be treated to the surfactant is 1:0.2~0.35.

[0053] In some embodiments, the surfactant comprises the sodium dodecylbenzenesulfonate and the allyl polyether.

[0054] In some embodiments, the grinding aid comprises a solution to be treated, the sodium dodecylbenzenesulfonate, and the allyl polyether.

[0055] In some embodiments, the grinding aid comprises a solution to be treated, sodium dodecylbenzenesulfonate, and allyl polyether; the mass ratio of the solution to be treated, sodium dodecylbenzenesulfonate, and allyl polyether is 1:0.1~0.32:0.04~0.1. Preferably, the mass ratio of the solution to be treated, sodium dodecylbenzenesulfonate, and allyl polyether is 1:0.15~0.3:0.05~0.1. More preferably, the mass ratio of the solution to be treated, sodium dodecylbenzenesulfonate, and allyl polyether is 1:0.15~0.25:0.06~0.08.

[0056] This grinding aid works synergistically with the treatment solution, sodium dodecylbenzenesulfonate, and the allyl polyether to optimize the gradation of the ground material, reduce the D50 of the material, increase the particle size of particles below 2 μm, and improve the material's flowability, stability, oil absorption, and activation.

[0057] Furthermore, the solution to be treated is wastewater from the production of acrylic acid and its esters.

[0058] In some embodiments, the surfactant includes the sodium lignosulfonate and the alkylphenol polyoxyethylene ether.

[0059] In some embodiments, the grinding aid comprises a solution to be treated, the sodium lignosulfonate, and the alkylphenol polyoxyethylene ether.

[0060] In some embodiments, the grinding aid comprises a solution to be treated, sodium lignosulfonate, and alkylphenol polyoxyethylene ether; the mass ratio of the acrylic acid and its ester production wastewater, the sodium lignosulfonate, and the alkylphenol polyoxyethylene ether is 1:0.12~0.33:0.025~0.08.

[0061] This grinding aid works synergistically through the interaction of the solution to be treated, sodium lignosulfonate, and alkylphenol polyoxyethylene ether. It optimizes the gradation of the ground material, reduces the material D50, increases the particle size below 2μm, and improves the material's flowability, stability, oil absorption, and activation.

[0062] Furthermore, the solution to be treated is wastewater from the production of acrylic acid and its esters.

[0063] In some embodiments, the grinding aid comprises a solution to be treated and sodium dodecylbenzenesulfonate.

[0064] In some embodiments, the grinding aid comprises a solution to be treated and sodium lignosulfonate.

[0065] In some embodiments, the grinding aid comprises a solution to be treated and an allyl polyether.

[0066] In some embodiments, the grinding aid comprises a solution to be treated and a fatty alcohol polyoxyethylene ether.

[0067] In some embodiments, the grinding aid comprises a solution to be treated and alkylphenol polyoxyethylene ether.

[0068] In some embodiments, the grinding aid comprises a solution to be treated and nonylphenol polyoxyethylene ether.

[0069] In some embodiments, the grinding aid includes a solution to be treated, sodium dodecylbenzene sulfonate, and sodium lignin sulfonate.

[0070] In some embodiments, the grinding aid comprises a solution to be treated, sodium dodecylbenzenesulfonate, and fatty alcohol polyoxyethylene ether.

[0071] In some embodiments, the grinding aid comprises a solution to be treated, sodium dodecylbenzenesulfonate, and alkylphenol polyoxyethylene ether.

[0072] In some embodiments, the grinding aid includes a solution to be treated, sodium dodecylbenzenesulfonate, and nonylphenol polyoxyethylene ether.

[0073] In some embodiments, the grinding aid comprises a solution to be treated, sodium lignosulfonate, and allyl polyether.

[0074] In some embodiments, the grinding aid includes a solution to be treated, sodium lignosulfonate, and fatty alcohol polyoxyethylene ether.

[0075] In some embodiments, the grinding aid comprises a solution to be treated, sodium lignosulfonate, and nonylphenol polyoxyethylene ether.

[0076] In some embodiments, the allyl polyether has a molecular weight of 1000-2400. Preferably, the molecular weight of the allyl polyether is 1000-2000.

[0077] A second aspect of this application provides a method for preparing the grinding aid described in the first aspect, comprising the following steps: blending the solution to be treated and the surfactant to obtain the grinding aid.

[0078] In some embodiments, the blending temperature is 40°C to 50°C.

[0079] In some embodiments, the solution to be treated is acrylic acid and its ester production wastewater, and a concentration step is included before the blending: the acrylic acid and its ester production wastewater with a solid content of 2% to 20% is concentrated to the acrylic acid and its ester production wastewater with a solid content of 30% to 50% by mass.

[0080] In some embodiments, the wastewater from the production of acrylic acid and its esters, with a solid content of 2% to 20%, contains sodium acrylate at a mass content of 0.5% to 20%, sodium hydroxide at a mass content of 0.1% to 5%, and sodium p-toluenesulfonate at a mass content of 0.1% to 2%. Currently, the composition and mass ratio of alkaline washing wastewater generated during the cleaning of production equipment with sodium hydroxide in the production process of acrylic acid and its esters are usually within this range. The grinding aid obtained by concentrating this alkaline washing wastewater has higher grinding efficiency and better effect.

[0081] In some embodiments, the concentration step employs triple-effect evaporation for concentration. Triple-effect evaporation can concentrate the solution and recover the solvent.

[0082] In some embodiments, triple-effect evaporation concentration treatment involves evaporating and concentrating acrylic acid and its ester production wastewater with a solid content of 2% to 20% sequentially through three separators: a first-effect separator, a second-effect separator, and a third-effect separator, to finally obtain the desired acrylic acid and its ester production wastewater with a solid content of 30% to 50%.

[0083] In some embodiments, the gas phase temperature of the single-effect separator is 70.5°C to 81.5°C, and the gas phase pressure is -30.3 kPa to 40.3 kPa.

[0084] In some embodiments, the gas phase temperature of the double-effect separator is 60.8°C to 70.5°C, and the gas phase pressure is -55.7 kPa to 64.7 kPa.

[0085] In some embodiments, the gas phase temperature of the triple-effect separator is 50.5°C to 60.5°C, and the gas phase pressure is -65.6 kPa to 73.6 kPa.

[0086] Furthermore, the single-effect separator, double-effect separator, and triple-effect separator all employ evaporators.

[0087] A third aspect of this application provides the application of the grinding aid as described in the first aspect in the calcium carbonate grinding process.

[0088] When the aforementioned grinding aids are applied to the grinding process, the wastewater from the production of acrylic acid and its esters can be utilized in a deep manner. This can improve the particle size distribution and rheological properties of the ground materials, increase the activity rate and stability of the materials, and reduce grinding energy consumption.

[0089] In some implementations, the application includes the following steps:

[0090] Calcium carbonate coarse powder is wet-milled with the aforementioned grinding aid and water to obtain calcium carbonate slurry.

[0091] When the aforementioned grinding aids are applied to the calcium carbonate grinding process, the wastewater from the production of acrylic acid and its esters is utilized in a comprehensive manner. This process has the effects of reducing viscosity of calcium carbonate slurry, improving the particle size distribution and rheological properties of calcium carbonate, and increasing the activity and stability of calcium carbonate. In addition, it also reduces grinding energy consumption.

[0092] In some embodiments, the average particle size of the coarse calcium carbonate powder is 250 mesh to 500 mesh.

[0093] In some embodiments, the wet grinding time is 25 min to 45 min.

[0094] In some embodiments, the application of grinding aid in the calcium carbonate grinding process includes: coarsely crushing dried calcite ore with a jaw crusher, followed by dry grinding with a ball mill to obtain coarse calcium carbonate powder; then uniformly mixing the coarse calcium carbonate powder, grinding aid and water and feeding it into a ball mill for wet grinding for 25 min to 45 min to obtain calcium carbonate slurry.

[0095] Furthermore, the calcium carbonate content in the calcite ore is ≥95%; the average particle size of the calcite ore is 12 mm ~ 25 mm; the average particle size of the calcite ore after jaw crushing is 45 mesh ~ 65 mesh; and the average particle size of the coarse calcium carbonate powder is 250 mesh ~ 500 mesh.

[0096] In some embodiments, the grinding aid is added at a rate of 0.2% to 0.5% of the mass of the coarse calcium carbonate powder.

[0097] In some embodiments, the grinding aid is added by spraying, thereby allowing the aid to be more fully dispersed in the calcium carbonate powder.

[0098] In some embodiments, the wastewater from the production of acrylic acid and its esters comes from alkaline washing wastewater generated during the cleaning of the production equipment with sodium hydroxide in the production process of ethyl acrylate, propyl acrylate or butyl acrylate.

[0099] The following are specific examples.

[0100] The alkaline washing wastewater generated during the cleaning of the ethyl acrylate production unit with sodium hydroxide in the esterification of acrylic acid and ethanol is taken as an example. The components of this alkaline washing wastewater are as follows: sodium acrylate, sodium p-toluenesulfonate, sodium hydroxide, alcohols, aldehydes, sodium sulfate, sodium chloride, as well as water-insoluble calcium and magnesium salts and unavoidable solid impurities. The solid content of this alkaline washing wastewater is 2%–20%, the mass content of sodium acrylate is 0.5%–20%, the mass content of sodium hydroxide is 0.1%–5%, and the mass content of sodium p-toluenesulfonate is 0.1%–2%. Specifically, due to reaction conditions and raw materials, the ethyl acrylate production unit may retain the following raw materials: acrylic acid, the catalyst sodium p-toluenesulfonate, and ethanol; may retain organic byproducts: formaldehyde and acrolein; may retain sodium sulfate, sodium chloride, as well as water-insoluble calcium and magnesium salts and other unavoidable solid impurities from the raw materials; and may also retain the product ethyl acrylate. After the ethyl acrylate production unit is cleaned with sodium hydroxide, acrylic acid reacts to form sodium acrylate; ethyl acrylate hydrolyzes into sodium acrylate and the corresponding small molecule alcohols. Therefore, the components of this alkaline washing wastewater are sodium acrylate, sodium p-toluenesulfonate, sodium hydroxide, alcohols, aldehydes, sodium sulfate, sodium chloride, as well as water-insoluble calcium and magnesium salts and unavoidable solid impurities.

[0101] Then, the above-mentioned alkaline washing wastewater is pretreated by filtration to remove water-insoluble calcium salts, magnesium salts, and unavoidable solid impurities.

[0102] Next, triple-effect evaporation and concentration treatment is performed to remove alcohols, aldehydes, sodium sulfate, and sodium chloride from the alkaline washing wastewater. Further concentration treatment yields the desired acrylic acid and ester production wastewater. This acrylic acid and ester production wastewater contains only three components: sodium acrylate, sodium hydroxide, and sodium p-toluenesulfonate. The solid content of this wastewater is 30%–50%, the mass content of sodium acrylate is 15%–37%, the mass content of sodium hydroxide is 0.3%–13%, and the mass content of sodium p-toluenesulfonate is 0.3%–5%.

[0103] The specific steps in the triple-effect evaporation concentration process are as follows:

[0104] The above-mentioned alkaline washing wastewater is treated in a single-effect separator with a gas phase temperature of 70.5~81.5°C and a gas phase pressure of -30.3~40.3 kPa, causing alcohols and aldehydes to volatilize. It is then treated in a second-effect separator with a gas phase temperature of 60.8~70.5°C and a gas phase pressure of -55.7~64.7 kPa, causing partial crystallization of sodium sulfate. Finally, it is treated in a triple-effect separator with a gas phase temperature of 50.5~60.5°C and a gas phase pressure of -65.6~73.6 kPa, causing sodium sulfate and sodium chloride to crystallize and precipitate. After filtration, the wastewater is concentrated to the required solids content.

[0105] The specific content of each component in the wastewater from the production of acrylic acid and its esters is as described in the examples.

[0106] Example 1

[0107] Grinding aid was prepared by stirring 300g of acrylic acid and its ester production wastewater, 75g of sodium dodecylbenzenesulfonate, and 18g of allyl polyether with a molecular weight of 2000 in a 45°C water bath for 1 hour.

[0108] The solid content of the above-mentioned wastewater from the production of acrylic acid and its esters is 49.73%, the mass content of sodium acrylate is 36.79%, the mass content of sodium hydroxide is 8.06%, and the mass content of sodium p-toluenesulfonate is 4.88%; the sodium dodecylbenzenesulfonate is model LAS-30; and the allyl polyether is model APEG-2000.

[0109] Spray 12g (0.4% of the mass of the coarse calcium carbonate powder) of the above grinding aid onto 3kg of 400-mesh coarse calcium carbonate powder, pour it into a 1580×800×1000mm ball mill containing 1.61kg of water, grind for 40min, and prepare a 65% concentration calcium carbonate slurry.

[0110] Example 2

[0111] Grinding aid was prepared by stirring 300g of acrylic acid and its ester production wastewater, 50g of sodium dodecylbenzenesulfonate, and 27g of allyl polyether with a molecular weight of 900 in a 45°C water bath for 1 hour.

[0112] The solid content of the above-mentioned wastewater from the production of acrylic acid and its esters is 31.12%, the mass content of sodium acrylate is 16.38%, the mass content of sodium hydroxide is 11.78%, and the mass content of sodium p-toluenesulfonate is 2.96%; the sodium dodecylbenzenesulfonate is model LAS-30; and the allyl polyether is model APEG-900.

[0113] Spray 12g (0.4% of the mass of the coarse calcium carbonate powder) of the above grinding aid onto 3kg of 400-mesh coarse calcium carbonate powder, pour it into a 1580×800×1000mm ball mill containing 1.61kg of water, grind for 40min, and prepare a 65% concentration calcium carbonate slurry.

[0114] Example 3

[0115] Grinding aid was prepared by stirring 300g of acrylic acid and its ester production wastewater, 50g of sodium dodecylbenzenesulfonate, and 22g of allyl polyether with a molecular weight of 1000 in a 45°C water bath for 1 hour.

[0116] The solid content of the above-mentioned wastewater from the production of acrylic acid and its esters is 34.5%, the mass content of sodium acrylate is 17.95%, the mass content of sodium hydroxide is 12.45%, and the mass content of sodium p-toluenesulfonate is 4.1%; the sodium dodecylbenzenesulfonate is model LAS-30; and the allyl polyether is model APEG-1000.

[0117] Spray 12g (0.4% of the mass of the coarse calcium carbonate powder) of the above grinding aid onto 3kg of 400-mesh coarse calcium carbonate powder, pour it into a 1580×800×1000mm ball mill containing 1.61kg of water, grind for 40min, and prepare a 65% concentration calcium carbonate slurry.

[0118] Example 4

[0119] Example 4 is basically the same as Example 1, except that: sodium lignosulfonate of equal mass is used to replace LAS-30, and alkylphenol polyoxyethylene ether of equal mass is used to replace allyl polyether.

[0120] Among them, the sodium lignosulfonate mentioned above is a 30% mass concentration solution, and the alkylphenol polyoxyethylene ether is OP-10 with a 70% mass concentration.

[0121] Example 5

[0122] Example 5 is basically the same as Example 1, except that: an equal mass of fatty alcohol polyoxyethylene ether is used instead of allyl polyether.

[0123] Among them, the aforementioned fatty alcohol polyoxyethylene ether is model AEO-9 with a mass concentration of 92%.

[0124] Example 6

[0125] Example 6 is basically the same as Example 1, except that nonylphenol polyoxyethylene ether is used instead of allyl polyether in equal mass.

[0126] The nonylphenol polyoxyethylene ether mentioned above is model NP-10 with a mass concentration of 92%.

[0127] Example 7

[0128] Example 7 is basically the same as Example 1, except that sodium dodecylbenzenesulfonate of equal mass is used instead of allyl polyether.

[0129] Comparative Example 1

[0130] Comparative Example 1 is basically the same as Example 1, except that no grinding aid is added.

[0131] Comparative Example 2

[0132] Comparative Example 2 is basically the same as Example 1, except that the grinding aid does not contain the surfactants sodium dodecylbenzenesulfonate and allyl polyether, and the surfactants in the grinding aid are replaced by an equal mass of acrylic acid and its ester production wastewater.

[0133] Comparative Example 3

[0134] Comparative Example 3 is basically the same as Example 1, except that an equal mass of sodium acrylate solution with a mass concentration of 30% is used to replace the wastewater from the production of acrylic acid and its esters in the grinding aid.

[0135] Comparative Example 4

[0136] Comparative Example 4 is basically the same as Example 1, except that sodium stearate and allyl polyether are replaced with equal masses.

[0137] The calcium carbonate slurries of Examples 1-7 and Comparative Examples 1-4 were tested for particle size distribution, viscosity, stability, oil absorption and activation degree. The test results are shown in Table 1 below.

[0138] The test conditions or standards for each performance test item are as follows:

[0139] Particle size distribution: The calcium carbonate slurry was dried at 105°C for 8 hours to obtain powder, and the particle size distribution of the powder was tested using a laser particle size analyzer.

[0140] Viscosity test: The viscosity data of calcium carbonate slurry was tested using a rotational viscometer.

[0141] Stability test: Weigh 500g of the above calcium carbonate slurry into a beaker, let it stand for 5 days, and observe whether there is water separation or stratification.

[0142] Oil absorption test: The calcium carbonate slurry was dried at 105°C for 8 hours to obtain powder, and then the oil absorption value of the powder was tested according to GB / T 19281-2014.

[0143] Activation degree determination: Calcium carbonate slurry was dried at 105°C for 8 hours to obtain powder, and then the activation degree of the powder was tested according to GB / T 19281-2014.

[0144] Table 1

[0145]

[0146] As shown in Table 1 above, the grinding aids prepared in Examples 1-7 significantly reduced the D50 of the calcium carbonate slurry, increased the content of particles smaller than 2 μm, and improved the fluidity, stability, oil absorption, and activation of the calcium carbonate slurry, resulting in better performance. In Comparative Example 1, without the grinding aid, the slurry exhibited severe stratification and poor stability. Comparative Example 2, using wastewater from the production of acrylic acid and its esters directly as a grinding aid, had a positive effect on particle size distribution, but slight stratification occurred in the calcium carbonate slurry, and its stability and activation need improvement. In Comparative Example 3, replacing the wastewater with sodium acrylate aqueous solution was slightly better than using wastewater directly as a grinding aid, but there was no significant improvement in stability, activation, or other properties. In Comparative Example 4, replacing the surfactant with sodium stearate did not yield outstanding performance.

[0147] As can be seen from Examples 1-3, the grinding aid includes wastewater from the production of acrylic acid and its esters, sodium dodecylbenzenesulfonate, and allyl polyether. When the mass ratio of the wastewater from the production of acrylic acid and its esters, sodium dodecylbenzenesulfonate, and allyl polyether is 1:0.1~0.32:0.04~0.1, the three components interact synergistically, further optimizing the gradation and overall performance of the calcium carbonate slurry. When the mass ratio of the wastewater from the production of acrylic acid and its esters, sodium dodecylbenzenesulfonate, and allyl polyether is 1:0.15~0.25:0.06~0.08, the gradation and overall performance of the calcium carbonate slurry are even more outstanding.

[0148] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0149] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A grinding aid, characterized in that, The grinding aid comprises acrylic acid and its ester production wastewater and a surfactant; the acrylic acid and its ester production wastewater contains sodium acrylate, sodium hydroxide, and sodium p-toluenesulfonate; the surfactant comprises at least one of sodium dodecylbenzenesulfonate, sodium lignin sulfonate, allyl polyether, fatty alcohol polyoxyethylene ether, and alkylphenol polyoxyethylene ether. The mass ratio of the acrylic acid and its ester production wastewater to the surfactant is 1:0.08~0.39; The solid content of the wastewater from the production of acrylic acid and its esters is 30% to 50%, the mass content of sodium acrylate in the wastewater is 15% to 37%, the mass content of sodium hydroxide in the wastewater is 0.3% to 13%, and the mass content of sodium p-toluenesulfonate in the wastewater is 0.3% to 5%.

2. The grinding aid as described in claim 1, characterized in that, At least one of the following conditions must be met: (1) The surfactant comprises the sodium dodecylbenzenesulfonate and the allyl polyether; (2) The surfactant includes the sodium lignosulfonate and the alkylphenol polyoxyethylene ether.

3. The grinding aid as described in claim 2, characterized in that, At least one of the following conditions must be met: (1) The mass ratio of the acrylic acid and its ester production wastewater, the sodium dodecylbenzenesulfonate and the allyl polyether is 1:0.1~0.32:0.04~0.1; (2) The mass ratio of the acrylic acid and its ester production wastewater, the sodium lignosulfonate and the alkylphenol polyoxyethylene ether is 1:0.12~0.33:0.025~0.

08.

4. A method for preparing a grinding aid as described in any one of claims 1 to 3, characterized in that, The process includes the following steps: blending the wastewater from the production of acrylic acid and its esters with the surfactant to obtain the grinding aid.

5. The method for preparing the grinding aid as described in claim 4, characterized in that, At least one of the following conditions must be met: (1) Before the blending, a concentration step is also included: the acrylic acid and its ester production wastewater with a solid content of 2% to 20% is concentrated into the acrylic acid and its ester production wastewater with a solid content of 30% to 50% by mass content; (2) The blending temperature of the blend is 40°C ~ 50°C.

6. The application of a grinding aid as described in any one of claims 1 to 3 in a grinding process.

7. An application as described in claim 6, characterized in that, The steps include the following: Calcium carbonate coarse powder is wet-milled with the aforementioned grinding aid and water to obtain calcium carbonate slurry.

8. The application as described in claim 7, characterized in that, At least one of the following conditions must be met: (1) The amount of the grinding aid added is 0.2% to 0.5% of the mass of the coarse calcium carbonate powder; (2) The average particle size of the coarse calcium carbonate powder is 250 mesh to 500 mesh; (3) The grinding time of the wet grinding is 25 min to 45 min.

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