NO. 369, Road S209, Huanxiu, Qingdao City, China
Heavy calcium carbonate, also known as ground calcium carbonate, or heavy calcium for short, is made by processing natural carbonate minerals as raw materials. It has high chemical purity, high inertness, good thermal stability, will not decompose below 400℃, high whiteness, low oil absorption, low refractive index, soft, dry, free of crystal water, low hardness, low abrasion value, non-toxic, Tasteless, odorless, good dispersion and other advantages.
As a functional inorganic filler, calcium carbonate is mainly used in papermaking, plastics, paint and coatings, rubber and other industries. From a global perspective, calcium carbonate for papermaking accounts for 60% of the consumption structure.
As a functional filler, heavy calcium carbonate, its mesh number, whiteness and calcium carbonate content determine its application areas. 325 meshes, whiteness 95%, calcium carbonate content 98% can be used for paper making; 325 mesh, whiteness 95%, calcium carbonate content 98.5% can be used for artificial marble; 325 mesh, whiteness 90%, calcium carbonate content 98% Can be used for construction; 400 mesh, whiteness 93%, 96% calcium carbonate content can be used for rubber; 400 mesh, whiteness 95%, calcium carbonate content 99% can be used for plastics; 400 mesh, whiteness 95%, carbonic acid 98.5% calcium content can be used for floor tiles.
With the development of grinding and grading equipment, the production and demand of ultrafine heavy calcium powder has increased significantly. Among them, the use of 2500-6500 mesh heavy calcium powder in high-end papermaking has also increased.
The raw materials are carbonate minerals such as shells, calcite, marble, limestone, chalk and dolomite.
Common heavy calcium processing methods include dry, wet, and dry-wet process combination methods. Dry processing is conducive to the realization of industrial scale and a certain degree of product refinement; wet processing is conducive to achieving a higher degree of product refinement and functional production; dry and wet process combination is conducive to making up for the dry process in high-end products The insufficiency.
From a practical point of view, products with D97=2500 mesh or less are generally produced by dry method; products with D97=2500~6500 mesh (or higher content of 2μm) are usually produced by wet method.
The main equipment of dry process is Raymond mill, ball mill, jet mill, ring roller mill, vibration mill, vertical mill, and high-speed mechanical impact mill.
At present, the dry processing of large-scale enterprises in the world mostly uses vertical mill processing equipment and technology. The large-scale and fine-grained benefits of vertical mill dry powder production are the most obvious. It has become one of the main research directions in the refined processing technology of heavy calcium powder in recent years.
The wet method is used to process refined and functional heavy calcium powder, the mesh number is above 3000, and the equipment mostly uses stirring mills. Adding pulverizing aids in the fine media mill can prepare sub-micron or even Nana ultra-fine powder.
Wet grinding mainly produces products above 3000 meshes, and dry grinding mainly produces products below 2500 meshes. The particle size distribution of heavy calcium produced by wet method is narrow, which is unimodal or bimodal; the particle size distribution of heavy calcium produced by dry method is broad, and the distribution is bimodal or multimodal.
The particles of wet grinding products are generally spherical or quasi-spherical; dry products are mostly indeterminate and have obvious edges and corners.
The dry-wet integrated process of vertical mill + secondary classification + tertiary classification and multi-stage wet grinding can be used to produce 325~800 mesh products to meet the basic needs of the market, and use super-subdivision equipment for secondary and tertiary The graded production of medium and high-end fine powders of 800 to 2500 meshes meets the needs of the medium and high-end markets. The lower product adopts wet grinding and other fine grinding and functional development, and produces 2500~6500 mesh ultra-fine functional powder to meet the high-end market demand.
The dry-wet integrated process of vertical mill + secondary classification + tertiary classification combined with multi-stage wet grinding not only realizes the large-scale industrialization of heavy calcium, refined and functional products, but also improves the product structure, which is the future of heavy carbonic acid An integrated demonstration process for the in-depth development of calcium industry transformation and upgrading.
The minerals of heavy calcium carbonate dissociate during the crushing process, and unsaturated particles Canad2+CO32-will be exposed. Unsaturated particles will hydrate with surface water, making the surface of heavy calcium carbonate particles hydrophilic and oleo phobic. The active points on the surface of heavy calcium carbonate can be used for physical and chemical modification to change its hydrophilic and oleo phobic properties.
Modification methods include: physical coating modification, surface deposition modification, surface chemical modification (coupling agent modification, composite coupling agent modification, polymer coating modification, organic matter modification), mechanochemical modification High-energy surface modification (irradiation, plasma, ultrasonic).
To optimize the effect of surface modification, the size of modified heavy calcium carbonate is hand-sized, green and environmentally friendly, and the conversion of calcium carbonate modification to special type, functional type and high value-added type is the development trend of heavy calcium surface modification.