China's papermaking ground calcium carbonate (below)

4. Development of slurry products to high solids content In the initial stage of developing GCC for papermaking, mud cakes containing 20% ​​to 25% moisture are the main product forms. Currently, this product form has basically been replaced by slurry and dry powder. The use of domestic small-sized mills can now meet the requirements for producing a slurry with a solid content of 70% to 75% of the general quality standard. The China Pulp and Paper Research Institute uses a new improved mill and the latest production technology to produce D962μm slurry products with solids content of 78%-80%, enabling users to achieve solids content without the need for additional dry powder. 68%-72% high consistency paper coating. The emergence of this high-consistency GCC slurry production technology will impact the market of paint grade dry powder products to a certain extent, and its production cost will be higher than the production of 75% concentration products, equivalent to 1/3-1/4 of the dry powder cost. .
5. The particle size distribution of products and the concept of particle size distribution of engineering pigments are one of the most important indicators for paper-making GCC filler and coating grade products. Filler grade products involve the wear of the pigment on the equipment and the retention of the filler in the sheet and the optical properties of the paper. Coating grade products involve the rheology of the coating, the volume of the pigment filling, and the optical properties and printability of the paper coating. Therefore, whether GCC suppliers can provide products with different particle size distributions that are more suitable for improving paper quality according to the technical requirements of different paper grades in paper mills has become an important content for evaluating the production technology level of manufacturers.
With traditional GCC pigments, the nature of the paper often creates conflicting features. For example, using a finer GCC can increase the gloss of the coated paper, but it also speeds up the solidification rate of the ink and reduces the gloss of the print. Fine pigment components also reduce paper brightness and opacity. Recent studies on the particle size and distribution of GCC pigments abroad have proposed the concept of “engineered pigments”. Although there is no strict definition of this term, the research scope is to adjust the GCC particle size distribution to the paper coating pigments. Research and hole-like structure to improve and improve the optical and post-printing properties of paper. The research results show that the engineering pigments have the best particle size distribution and air permeability, which can improve the brightness, opacity, smoothness, and printing glossiness of the coated paper at once, so that the printed crystals can have high-quality printed images. Replacing the general GCC used for precoating with the engineering GCC can improve the opacity and anti-foaming properties of the sheet.
At present, most domestic paper GCC products are general GCC products, with a wide particle size distribution, mostly in the 9-15 grain class, and the latest production technology can be controlled at 7-9 grain grades. The engineering GCC products have attracted the attention of the paper industry, and the product size tends to develop in a narrower distribution direction.
6. The index of crystal whiteness (brightness) rises. The majority of foreign paper-making GCC whiteness is 87%-92%, and products with whiteness over 90% can increase the price of whiteness by 1 to 3 US dollars per metric ton per ton. The whiteness of paper-making GCC has increased from 90%-92% six years ago to the current level of 94%, and has further increased. At present, the domestic whiteness of D90 products can reach 96% -97%. The high whiteness product market in foreign countries consumes little, and the price is higher. It is mainly used for high brightness paper and instead of TiO2. The preference of domestic paper consumers for high whiteness is one of the reasons for the increase in whiteness. GCC producers often use high brightness as a sales tool. Marketing strategies that increase whiteness and do not raise prices also contribute to the increase in whiteness. On the one hand, this phenomenon reflects the market demand for high-white paper. It also reflects the imperfections in the use of technology by paper mills, the irrational prices, and the irrational use of limited high-quality calcite resources in China.
7. New Progress in Dry Processing of D90 Products The traditional concept of paper GCC advocates wet production. The advantages are high output, low cost, and easy control of particle size distribution. In particular, wet processed particles have a smooth surface and small edges and corners. The wear value and wettability of the surface of the wet processed product particles with the water have better compatibility with the paint additives. In recent years, due to advances in high-precision grading equipment and dry efficient grinding equipment, it has become possible to control large particle contents. Italy and Malaysia have built two D90 coating grade GCC production lines used in the production of high-speed coating machines. It is estimated that by the end of this year, the first dry process production line with an annual output of 10,000 tons will be put into use, which may have a certain impact on the wet-dry D90 powdered product market. The cost of topcoat products currently produced using dry processes is still higher than wet processing.
The foreign wet paper GCC production equipment features large volume, large aspect ratio, low line speed, high performance wear-resistant materials and fully automatic control. The top of the barrel has a settlement zone, which can effectively control large particles and increase slurry concentration. . At present, domestic papermaking GCC production equipment is mostly 80-500L minicomputers. In order to increase production efficiency, higher line speeds are generally used, resulting in large equipment and medium wear, poor product quality stability, and unsatisfactory particle size distribution. % solids products have certain difficulties. From the perspective of the operation of the four sets of imported equipment in the country, the replacement of wearing parts can reach more than 20,000 hours under normal conditions, while the domestic machines generally only have 7000 hours. In recent years, medium-sized aircraft with 1000L, 1500L, and 3000L have been introduced in the country, which has created conditions for solving the problems of small-scale equipment cluster production and poor quality stability. However, there are still certain difficulties in the production of 78%-80% concentration products.
In terms of grinding media, domestic alumina balls and zirconia balls have been able to meet the production needs of general quality products, but the wear cost of tons of products is still higher than the imported ball, and needs further improvement.