Calcium carbonate is a versatile industrial raw material used in various fields, including plastics, paper, rubber, construction, food, medicine, and more. The type of calcium carbonate required by different industries varies depending on several factors.
From a mineral composition perspective, calcium carbonate can be in the form of calcite, large and small square solutions, coarse crystals, ice continent stone, marble, dali rock, white jade, limestone, stone stalactite, stalagmites, stone pillars, stone mantle, travertine, chalk, aragonite, and more.
Based on sedimentation volume, there are heavy calcium carbonate, light calcium carbonate, and precipitated calcium carbonate. The fineness of calcium carbonate varies as well, ranging from a few mesh to 5000 mesh and other ultra-fine particles such as nano calcium carbonate.
Oil absorption value: the rubber industry has higher requirements for the oil absorption value of ultrafine calcium carbonate, the higher the oil absorption value, the better the wettability and reinforcement of rubber.
pH value: the pH value of ultrafine calcium carbonate mainly affects its vulcanization rate, generally should be controlled at 9.5~10.5, if the pH value is low, the vulcanization rate slows down, reduces efficiency and increases energy consumption.
Crystal shape: Because rubber requires very high reinforcement performance, the crystal shape of ultrafine calcium carbonate should be mainly chain or chain lock, and the chain segments will be intertwined during processing, which can enhance the strength of the system.
Particle size: the nano calcium carbonate particle size applied to rubber is generally 80~120nm is appropriate, the particle size is too large to play a reinforcing effect, and the particle size is too small and the contact area of rubber infiltration increases, making dispersion difficult and affecting the mixing of rubber.
Moisture: moisture control should not be higher than 0.5%, if the moisture is too high, the vulcanization scorching time is prolonged, which is not conducive to the increase of vulcanization rate.
In recent years, in the papermaking process, the amount of calcium carbonate, talc, kaolin, wollastonite, bentonite and other fillers and pigments has been increasing, and it has become an important papermaking raw material that ranks second only to fiber. And with the gradual transformation of acid papermaking process to neutral and alkaline papermaking process, calcium carbonate as an important papermaking raw material is increasingly used in the papermaking industry.
The application of calcium carbonate in papermaking is mainly in two aspects: one is as a papermaking filler, and the other is as a coating pigment.
Calcium carbonate in paper is used as filler. Calcium carbonate is used as a filler in paper for the following purposes. The filler is dispersed between the slurry fibers to fill the void to improve the optical properties such as opacity and whiteness of the paper; Improve the ink absorption of paper, so that the paper has better printability; Meet some special performance requirements of paper, such as improving the electrical conductivity and heat resistance of paper; Reduce the use of fiber raw materials and reduce production costs; The filler has a large specific surface area, which helps to overcome resin obstacles.
Heavy calcium carbonate is mainly used as a filler in printing paper, writing paper, office paper and advertising paper other than cigarette paper, filter paper and special low-weight information paper. In principle, lightweight calcium carbonate can be used in all papers, and is currently mainly used as a high-grade paper filler. For example: cigarette paper, office information paper (such as fax paper, instrument recording paper, inkjet printing paper), low-weight newsprint, low-quantity coated paper, etc.