Calcium carbonate processing is a traditional industry. Driven by robust demand across numerous sectors, China boasts over a thousand calcium carbonate manufacturers of varying scales. In particular, the demand for ground calcium carbonate (GCC) will maintain an average annual growth rate of 5% to 8% over the next five years.With the rapid expansion of the calcium carbonate market, downstream end-user industries have put forward more personalized functional requirements for calcium carbonate powder, mainly reflected in ultra-fine processing and functional modification of the product. Ultra-fine calcium carbonate has gradually become the core development focus of the GCC industry, and the advancement of wet grinding technology can basically realize the ultra-fine processing of ground calcium carbonate.
Calcium carbonate is currently the most consumed filler in the paper industry. This shift stems from the gradual replacement of acidic papermaking processes by neutral and alkaline papermaking technologies in China, which has greatly boosted market demand for calcium carbonate.
The paper industry represents a key downstream application market for calcium carbonate, whose functions in papermaking fall into two main categories:
1. Calcium Carbonate for Paper Filling
Most manufacturers adopt low-mesh products ranging from 325 mesh to 800 mesh. The addition dosage varies with paper types, ranging from 5% to 50%, and this product is mainly used by base paper producers.
2. Calcium Carbonate for Paper Coating
Coating-grade calcium carbonate is a high value-added product segment within the calcium carbonate industry with stringent fineness standards. The slurry used requires a particle content of over 65% for particles smaller than 2 μm. Most large paper mills operate self-contained calcium carbonate grinding facilities, pumping calcium carbonate slurry directly to the paper machine mixing chest via pipelines for pulp preparation. Three core reasons account for the widespread use of slurry:
First, paper mills consume massive volumes of calcium carbonate. Purchasing low-mesh raw powder and conducting in-house grinding effectively cuts production costs.
Second, high-mesh slurry produced via wet grinding can be directly connected to the paper machine mixing chest, eliminating separate steps of dry powder mixing, stirring and dispersion.
3. paper machines equipped with coating lines impose extremely strict fineness requirements on calcium carbonate.
Ordinary dried powder hardly meets fineness grades above 90, while ultra-fine slurry exhibits superior dispersibility compared with ultra-fine dry powder.Pigments account for 70% to 90% of coating layers by mass fraction, which explains the strong demand for coating-grade calcium carbonate from coated paper production lines.
