The role of aluminum sulfate in the papermaking industry

The role of aluminum sulfate in the papermaking industry

Aluminum sulfate solid is a white crystal that is widely used in various industries. In the papermaking industry, paper is made of fiber (wood pulp or straw pulp). Unsizing paper absorbs water and is not suitable for writing and printing.

In addition, the strength of paper will decrease after absorbing water, which will affect its use. Therefore, except for toilet paper, filter paper and cigarette paper, about 80% of paper needs to add or apply some water-resistant substances on the surface of the paper to make the paper have the performance of delaying liquid penetration, so as to achieve the purpose of ink resistance and oil resistance (such as food packaging paper). This aluminum sulfate process is called sizing, and the added substance is called aluminum sulfate sizing agent.

Through the analysis of the aluminum sulfate sizing principle, it is believed that the molecules of the sizing agent should have both hydrophilic and hydrophobic groups, so that it can be evenly retained on the fiber surface by itself or with the help of other retention agents, so that the hydrophilic group can be combined with the fiber, and the hydrophobic group can be turned to the outside of the fiber, thereby reducing the surface free energy between the fiber and the air, changing the contact angle of the liquid on the fiber surface, and achieving the purpose of sizing. Most papers need sizing. Aluminum sulfate sizing agents can be divided into internal sizing agents and surface sizing agents. Internal sizing agents are widely used chemicals in the papermaking industry, because aluminum sulfate is mainly used for internal sizing in papermaking. Aluminum sulfate is mainly used as a papermaking sizing agent and a flocculant for drinking water, industrial water and wastewater treatment. It is also used to produce artificial gemstones and other aluminum salts, alum, potassium alum, and raw materials for refined aluminum sulfate.

In addition, it is also widely used as a clarifier, petroleum decolorizer, concrete waterproofing agent and rainproof cloth raw material, papermaking white powder, titanium dioxide membrane treatment and catalyst carrier production.