What kind of nano calcium carbonate should the paper industry use?

In terms of paper coatings, nano calcium carbonate is generally only used in special products such as quantitative coated paper and matt copper paper, and its dosage can be as high as 80%. Due to its whiteness, large specific surface area, high surface activity, high strength and hardness, nano-calcium carbonate can help improve the quality of coated paper. By adding nano-calcium carbonate to the coating, coated paper with high gloss, high whiteness, high surface strength and high ink absorption can be obtained, and the smoothness of the paper can be improved.

â–  Technical requirements for nanometer calcium carbonate for papermaking

(1) Crystal morphology

PCC crystal morphology is one of the most important factors affecting papermaking production operability, coating performance, and paper quality. Various forms of PCC can be roughly divided into two forms of single crystal particles and polymers. The former influences on papermaking mainly from morphology and aspect ratio, and the latter mainly comes from complex pore structure characteristics.

(2) aspect ratio

The aspect ratio refers to the ratio of the length to the diameter of a single particle. Spindle, column and needle are all large aspect ratio crystals, and their aspect ratio is generally (4~7):1. Large aspect ratio PCC is used for paper filler. When calcium carbonate single crystal is combined with paper fiber. It is easy to produce bridging effect, so that the fiber swells and forms uniform pores, which is favorable for the air permeability, thickness, opacity, stiffness, reduction of two-sided difference, and obtaining high filler retention rate of the paper.

The rice grain and the diamond cube belong to the small aspect ratio, and the aspect ratios of the two are: (2~3): 1, (1~2): 1; while the sheet is usually described by the ratio of diameter to thickness, generally (6~14): 1, small aspect ratio PCC, only suitable for paper coatings, showing good coating gloss.

(3) Multimer PCC

Also known as complex PCC, it is generally formed by polymerization of monomers such as needles, very fine spheres, cubes, and rice grains, such as chrysanthemums. Its main physical properties are: é«™ porosity, é«™ dispersion coefficient, high oil absorption (adsorption) and low bulk density values. At the same filler retention rate, it is advantageous to increase the opacity, bulk, stiffness, calender paper smoothness, gas permeability and ink absorption of the filled paper.

The main negative effect is that the strength and sizing degree of the paper to be filled are slightly lower, followed by the viscosity and the surface strength of the coating. Therefore, complex PCC is rarely used alone in paper coatings, and is often used in combination with other small aspect ratio PCCs.

(4) Apparent shape of particles

Any form of PCC requires regular, uniform, uniform, and smooth edges; the aggregates of the aggregates are non-blocking; the number of monocrystalline particles of the chrysanthemum is similar, the opening degree is similar, and the end of the single crystal is sharp; the spindle is The needle is sharp.

(5) Apparent porosity and porosity

The surface of the PCC has fine pores, and the fine pores of the fine-quality PCC are fine and uniform, so that the PCC of the same morphology and particle diameter has a larger specific surface area, and the oil absorption value and astigmatism coefficient of the crucible.