It is the 'invisible hero' of the paper industry! How does calcium carbonate make paper whiter and smoother?

In the paper industry, calcium carbonate is a crucial raw material. It not only plays a pivotal role in the production process of paper, but also plays a key role in making paper whiter and smoother. Due to its abundant sources, low price, fine particles, high whiteness, it can significantly improve the opacity of paper, increase the ink absorption of paper, make paper relatively soft and compact, improve glossiness, and have little impact on the physical strength of paper. Calcium carbonate has been widely used in the papermaking industry.

Calcium carbonate plays two major roles in the paper industry

In the paper industry, calcium carbonate mainly plays two roles: paper filler and coating pigment. As a filler, calcium carbonate is dispersed between the fibers of the pulp to fill the gaps and improve the optical properties of the paper, such as opacity and whiteness. As a coating pigment, it is used to improve the quality and uniformity of the final printed product on paper or cardboard, resulting in better optical performance, smoothness, and glossiness of the paper.

1. As a filler

Calcium carbonate is mainly used as a filler in printing paper, writing paper, office paper, and advertising paper, except for cigarette paper, filter paper, and special low basis weight information paper. In practical applications, the heavy calcium raw material used for copperplate paper is 325 mesh, with a whiteness requirement of 92 or higher and a calcium carbonate content greater than 98%; Whiteboard paper and other materials should have a fineness of 1250 mesh or above, a whiteness requirement of 92 or above, and a calcium carbonate content of 98%.

Light calcium can be applied as a papermaking filler in principle to all types of paper, and is currently mainly used as a filler for high-end paper. For example: cigarette paper, office information paper (such as fax paper, instrument recording paper, inkjet printing paper), low basis weight news paper, low basis weight coated paper, etc.

2. As a coating pigment

Calcium carbonate can be used as a pigment for both base and top coatings to improve the quality and uniformity of printed products, and many characteristics of coated paper also depend on the choice of pigment. Calcium carbonate has high whiteness and good fluidity, making it suitable for preparing high solid content coatings; The demand for adhesive is relatively low, which can improve the ink absorption of the coating; Can provide good whiteness and color tone, improve breathability; It is one of the most commonly used coating pigments.

The secret to improving the whiteness and smoothness of paper

1. Improve whiteness: Calcium carbonate itself has extremely high whiteness, making it an ideal choice for improving paper whiteness. When calcium carbonate is added as a filler or pigment to paper, its high whiteness can significantly improve the overall whiteness of the paper, making it look whiter and flawless.

2. Increase glossiness and smoothness: The particles of calcium carbonate are small and uniform, which forms a delicate and uniform coating on the surface of the paper. This coating not only improves the glossiness of the paper, but also makes the surface of the paper smoother, reducing the occurrence of powder and hair loss during printing, thereby enhancing the printing quality.

Selection of Calcium Carbonate for Papermaking

Both heavy calcium carbonate and light calcium carbonate have their own advantages as papermaking fillers. The choice of calcium carbonate should be determined according to the actual paper production process requirements.

The amount of filler added is mainly determined by factors such as the type of paper, the type of pulp, the properties of the filler itself, and the papermaking conditions of the paper machine. In order to save plant fibers and reduce production costs, the amount of filler added should be appropriately increased while ensuring the requirements for paper copying and use.

Multiple advantages of calcium carbonate

In addition to improving the whiteness and smoothness of paper, calcium carbonate also has multiple advantages:

1. Cost reduction: Calcium carbonate has abundant sources and is inexpensive. Using it can reduce the amount of fiber raw materials used, thereby lowering production costs.

2. Improve ink absorption: Calcium carbonate has good ink absorption properties, which enables paper to better absorb ink during the printing process and improve the printing effect.

3. Enhance paper performance: Although the addition of calcium carbonate may have a certain impact on the physical strength of the paper, modified calcium carbonate can significantly improve the paper's tensile index, burst index, and other properties, making the paper more durable.

Calcium carbonate modification for papermaking

Although calcium carbonate is one of the important fillers in the paper industry, unmodified calcium carbonate has poor compatibility and bonding strength with pulp fibers, low retention rate, and is prone to material interface defects, reducing the mechanical strength of paper. Therefore, it is necessary to modify calcium carbonate, and the modification methods mainly include chemical coating modification and surface modification.

Calcium carbonate is widely used in the paper industry. Whether it is ordinary writing paper, office paper, or high-end copperplate paper, whiteboard paper, etc., the presence of calcium carbonate can be seen. Especially in the production of some special paper products, calcium carbonate plays an irreplaceable role and can truly be called the "invisible hero" of the paper industry.