The excellent suspending, bonding and dispersing properties of bentonite make it widely used in coatings. Its advantages are roughly as follows:
- Bentonite has excellent suspension and dispersion properties in water medium. The production process of bentonite makes the coating less prone to sedimentation and stratification, with uniform color, thereby improving the stability of the coating suspension. Moreover, it has good brushing performance and can form a coating of uniform thickness, smoothness and flatness. Based on this point, some heavy calcium carbonate can be added to the coating to replace light calcium carbonate, thereby reducing costs.
- Bentonite forms flocculent substances in water and has a thickening effect. Its molecular groups can combine with the organic base materials in the coating, enhancing the water resistance of the coating, and improving the strength and adhesion of the coating.
- Bentonite has certain adhesive force and covering power, and is low in price. When added to polyvinyl alcohol series coatings, the amount of polyvinyl alcohol and its fillers (such as light calcium carbonate) can be greatly reduced, thereby lowering the product cost.
- Bentonite has excellent hydrophilicity, plasticity, expansibility and adhesiveness. It can combine with an appropriate amount of water to form a colloid. In water, it can release charged ions. The repulsion between these ions serves as a dispersant in coatings. In waterproof coatings, bentonite particles in high-speed motion collide and cut with hot asphalt, breaking and gelatinizing the asphalt. The polar substances within the already gelatinized asphalt particles adsorb the bentonite particles, forming a colloidal hydration film on the surface of the asphalt particles. This reduces the interfacial tension between asphalt and water, prevents the asphalt particles from re-agglomerating, and thus forms a stable dispersed phase, playing the role of an emulsifier.
- Bentonite has cold resistance, and the coatings formulated with it can still be used at relatively low temperatures in winter.
The process of processing bentonite by Raymond mill
Raw material pretreatment
First, the raw bentonite ore is roughly crushed. Use a jaw crusher to crush large pieces of ore to an appropriate particle size of 15-30mm to avoid clogging the feed port of the Raymond mill. At the same time, the moisture content of the raw materials should be controlled below 10%. When the moisture content is too high, it needs to be pre-treated by sun-drying or a dedicated dryer. If necessary, a small amount of desiccant can be added to reduce viscosity. The pre-treated materials are sent to the storage bin by the bucket elevator and then evenly and quantitatively conveyed to the grinding mill by the electromagnetic vibrating feeder.
Grinding and classification
After the materials enter the grinding chamber of the Raymond mill, they are crushed under the pressure of the grinding rollers and grinding rings. The built-in analyzer of the Raymond mill controls the fineness of the finished product by adjusting the rotational speed. The higher the rotational speed, the finer the screened powder, and it can be freely adjusted from 80 to 400 mesh. The powder produced by grinding is carried into the classification system by the airflow of the fan. The unqualified coarse powder will automatically return to the grinding chamber for reprocessing, forming a closed loop. If drying treatment is required, hot air at a temperature of ≤200℃ can be introduced to evaporate moisture without damaging the structure of bentonite.
Powder collection and packaging
The powder that meets the fineness requirements enters the cyclone separator or pulse dust collector with the airflow to achieve the separation and collection of gas and powder. The collected finished products are conveyed to the finished product silo by the conveying device, and finally packaged by the automatic packaging machine or powder loading tank truck, and can be put into subsequent applications. The entire process requires regular cleaning of the grinding rollers and pipelines to prevent the adhesion and accumulation of bentonite, which may affect production efficiency.
Shanghai Cronus is mainly engaged in the manufacturing and promotion of mining crushing equipment and grinding equipment. Our company's Raymond mill, vertical mill and ultrafine mill are widely used in the grinding processing of bentonite and its products. If you have any needs, you can call our free hotline!
