At present, the production methods of heavy calcium carbonate mainly include dry method and wet method. The dry method generally produces heavy calcium below 2500 mesh. If the heavy calcium above 2500 mesh is produced, wet grinding is mainly used, while dry grinding is used as Preliminary process of wet grinding. Wet ground heavy calcium has the characteristics of good processing fluidity, high surface brightness, and excellent mechanical properties. It is mainly used in plastic products; with the increase of fineness, it is used in interior wall latex paint. Its contrast ratio, washing resistance, and whiteness etc. gradually increased. Therefore, more and more heavy calcium manufacturers are starting to develop the production of wet grinding heavy calcium from the dry heavy calcium processing production line. Guilin Hongcheng, as a manufacturer of calcium carbonate grinding mills, will introduce to you today the production and application of wet grinding heavy calcium.
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1. Production of wet-grinding heavy calcium: First, the dry-process heavy calcium powder is made into a suspension and placed in a mill for further crushing. After dehydration and drying, ultra-fine heavy calcium carbonate is obtained. The production process of wet grinding heavy calcium is as follows:
(1) Raw ore→jaw crushing→Raymond mill→wet stirring mill or flake machine (intermittent, multi-stage or cycle)→wet classifier→sieving→drying→activation→bag (coating grade heavy calcium). The wet method superfine classification is added to the process flow, which can separate the qualified products in time and improve the efficiency. Wet superfine classification equipment mainly includes small-diameter cyclone, horizontal spiral classifier and disc classifier. After classification, the pulp concentration is relatively thin, and sometimes a sedimentation tank is required. The economic index of this process is good, but the classification is difficult to operate. At present, there is no very effective wet method ultra-fine classification equipment.
(2) Raw ore→jaw crushing→Raymond mill→wet stirring mill→sieving→drying→activation→bag (filler grade heavy calcium).
(3) Raw ore→jaw crushing→Raymond mill→wet stirring mill or flake machine (intermittent, multi-stage or cycle)→sieving (papermaking coating grade heavy calcium slurry).
2. Advantages of wet-grinding heavy calcium: comparing product performance, wet-grinding heavy calcium has some obvious advantages over dry grinding. Mainly reflected in the following aspects:
(1) Particle size: The wet-milled superfine heavy calcium has a fine particle size, mainly producing products above 3000 mesh, and the content of<2μm can generally reach 90%, while the dry-process product has a relatively coarse particle size, mainly producing products below 2500 mesh.
(2) Particle size distribution: The particle size distribution of the heavy calcium produced by the wet method is narrow, showing a unimodal or bimodal distribution; while the dry method produces a wide particle size distribution of the heavy calcium, showing a bimodal or multimodal distribution.
(3) Granularity: Due to the different grinding environment and force-bearing mode of the particles during grinding, the particles of the heavy calcium products of wet grinding are generally spherical or quasi-spherical, while the products of dry grinding are mostly amorphous and have obvious edges and corners.
(4) Moisture content: The wet-process ultra-fine heavy calcium has undergone a drying procedure during the production process, and the moisture content is generally controlled below 0.3%, but the dry-process heavy calcium production cannot control the moisture content, which is generally above 1%. During the modification process, the dispersibility and fluidity of wet-process superfine heavy calcium are obviously better than those produced by dry process.
3. Application of wet grinding heavy calcium:
(1) Latex paint: When heavy calcium is used as a filler in latex paint, it plays a filling role and has a certain dry covering performance, which not only reduces the cost of latex paint, but also acts as a skeleton to improve the thickness, hardness, water resistance and Scrub resistance and other properties. Therefore, heavy calcium is more and more widely used in the architectural coating industry.
(2) Breathable membrane: The dispersibility and particle size (size, distribution) of calcium carbonate powder determine the fluidity of the powder itself, and also directly affect the production speed and process stability of the breathable membrane. Porosity, pore structure, air permeability and mechanical properties play a decisive role. Using heavy calcium produced by wet grinding as a "porogen" has lower oil absorption value, better dispersion and fluidity, and can also significantly reduce the amount of carrier resin, plasticizer, lubricant and other additives.
(3) Masterbatch: Masterbatch coloring is the most commonly used method in plastic coloring at present, and it usually consists of three parts: carrier resin, pigment, and additive. A large number of studies have shown that the use of calcium carbonate, wollastonite or barium sulfate to replace part of the pigments to prepare masterbatches can improve the dispersibility of pigments and reduce production costs without reducing the color performance of the masterbatch. Studies have shown that the color masterbatch prepared by wet-grinding heavy calcium instead of titanium dioxide has the same coloring performance when the replacement amount is 20%, which is very similar to the performance of pure pigments, and the color difference is small.
As a heavy calcium mill manufacturer, Guilin Hongcheng produces HCQ, HC series large-scale heavy calcium Raymond mill, HLM coarse powder vertical mill and other heavy calcium grinding equipment in the front-end dry production of wet grinding heavy calcium Has been widely used and good reputation. If you have the production demand of wet grinding heavy calcium and need front-end dry grinding equipment, please leave us a message for equipment details.
