Production and application of superfine heavy calcium carbonate in China
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The development of China's heavy calcium carbonate, regardless of the number, variety and technology of application, has a large gap compared with developed countries. The ratio of heavy calcium and light calcium in developed countries is 14-18:1, while China only 3—4:1.
The production process of heavy calcium carbonate in China mainly includes dry method and wet method, and the grinding equipment used in different processes is also different. Dry equipment mainly includes Raymond mill and high-speed mechanism impact mill, ball mill , rotary mill, vertical mill and so on. Among them, Raymond mill and vertical mill mainly process 200-400 mesh fine powder, and by improving it, the fine grader can be processed to process 600-800 mesh powder. High-speed mechanical impact pulverizer is mainly used to produce 1000-1250 mesh products. The combination of ball mill and dry micro-powder classifier can produce ultra-fine heavy calcium. The product fineness d97 can reach 4,5,6,8,10,15,20,25μm, and can be adjusted freely within the index range. The processing technology of this heavy calcium is characterized by continuous closed circuit production, multi-stage grading, single machine production capacity, and unit power consumption is greatly reduced compared with other grinding equipment, mainly used for large-scale superfine heavy calcium carbonate production. factory. Rotary mill or hurricane mill is used to process 500 mesh-800 mesh heavy calcium. It can be used to process products above 1250 mesh after being equipped with fine classifier. The wet process was established only after 1993. Compared with the dry process, the wet process produces high purity, fine particle size, stable quality, high ultra-fine processing efficiency and low cost. It is mainly used for the production of d60=2μm. And papermaking fillers and coating grade products with d90=2μm, the grinding equipment used mainly includes grinding and stripping machines, mixers and sanders. [next]
At present, the product structure of domestic heavy calcium carbonate is: 60-800 mesh fine powder accounts for about 88%, and more than 1250 mesh (d97≤10μm) ultrafine powder accounts for about 12% of the total output. Calcium carbonate products account for about 10% of total production.
The main consumption areas of domestic heavy calcium carbonate are plastics industry, paper industry, rubber industry, paints, adhesives, medicines and so on. The plastics industry is the largest consumer of heavy calcium carbonate. The refined heavy calcium powder can significantly improve the bonding strength and mechanical properties of the interface of plastic composites. The use of fine heavy calcium powder in plastics can reduce the cost of manufacturing and improve and improve its performance. It is reported that the heavy calcium filler with an average particle size of 5-10 μm can be filled in the polyester composite by 10%-15%; the filling amount of the heavy calcium with an average particle diameter of 1-3 μm can even reach the polymer. 20% - 40%. Therefore, the application range and amount of ultra-fine and surface-modified heavy calcium in plastic products will also expand. There are two main uses for heavy calcium carbonate in the paper industry, one as a filler and the other as a coating. At present, the majority of paper mills using an acid papermaking process, the filler is used mainly kaolin and talc, heavy calcium lower dosage of only 6.4%. However, the neutral sizing process or the alkaline sizing process is the development direction of the paper industry, which will eventually replace the acid sizing. The heavy calcium powder as a filler will replace talcum powder or kaolin in a wide range. Paint coatings are also one of the main consumption areas of heavy calcium. They are generally used as fillers and body pigments. The main application is architectural coatings. In developed countries such as Europe and the United States, adhesives are also one of the main consumption areas of heavy calcium, but the adhesive has higher requirements for heavy calcium. Generally, the fineness is >1250 mesh (<10μm), and the surface is organically modified. Due to the low production level of heavy calcium in China, the amount of heavy calcium in the adhesive is limited. In addition, heavy calcium carbonate with fine particle size, high purity and good whiteness is also used in the fields of ink, medicine, cosmetics and the like. [next]
At present, the main problem in the production of heavy calcium carbonate in China is that the product structure is unreasonable: about 88% is a fine powder of 60-800 mesh, and ultrafine powder of more than 1250 mesh only accounts for about 12% of the total output. Active heavy calcium carbonate products account for only about 10% of total production. As a result, 60-400 mesh fine powder supply exceeds demand, high-quality ultra-fine and ultra-fine active heavy calcium powder can not meet the needs of high-grade paper, degradable plastics, adhesives, etc., and it is still necessary to import some heavy calcium carbonate products every year. situation.
Superfine heavy calcium carbonate filler is widely used in rubber, plastics, ink, paint, pharmaceutical, food, resin, paper, cosmetics, household chemicals, feed additives and phosphorus fertilizer production industries, the development of modern industry, processing With the continuous advancement of technology, the application range of heavy calcium powder will gradually broaden. 2. Chemical composition: Ultra-fine heavy calcium carbonate is an industrial mineral product obtained by crushing and grinding natural calcium carbonate. Its main chemical composition is CaCO 3 , followed by MgO, Fe 2 O 3 , R 2 O 3 and SiO. 2 components.