The Application and Mechanism of Soda Ash in the Papermaking Industry

  Soda ash is widely used in the paper industry. In the pulping stage, it can be used as cooking agent to decompose fiber raw materials, assist delignification and treat recycled fiber. In the papermaking stage, it can activate the sizing agent to enhance the water resistance and other properties of the paper, adjust the pH value of the paper to improve durability and printability, and soften the water quality to ensure the papermaking process and paper quality. The specific application and mechanism are as follows:

1.  In the pulping stage

①Cooking agent in chemical pulping: In the chemical pulping process, soda ash can be used as cooking agent. It can chemically react with the lignin in wood, grass and other plant fiber raw materials, so that the lignin is dissolved and separated from the fiber, so as to decompose the fiber raw materials into usable pulp. Compared with caustic soda (sodium hydroxide) pulping, soda ash pulping is relatively low-cost and less corrosive to equipment. For example, in the production of wheatgrass pulp, the lignin in wheatgrass can be effectively removed by using soda ash cooking, and better quality pulp can be obtained.

②Delignification assistant: soda ash can adjust the pH value of the cooking solution, create a suitable alkaline environment for the delignification reaction, and help improve the efficiency and effect of delignification. When used in combination with other pulping agents, soda ash can promote the degradation and dissolution of lignin molecules, so that fibers can be better separated, while reducing the damage to cellulose and hemicellulose, which is conducive to improving the yield and quality of pulp.

③Treatment of recycled fibers: In the process of waste paper recycling and pulping, soda ash helps to remove impurities such as ink and adhesives in waste paper. It can weaken the binding force of ink particles and fiber surface, and it is easier to remove impurities such as ink through subsequent screening, washing and other processes, so as to improve the quality of recycled fiber and make it better for paper production.

2.  In the papermaking stage

①Activator of paper sizing agent: In the paper sizing process, some sizing agents need to play their best role under certain alkaline conditions. Soda ash can adjust the pH value of the sizing solution, activate the sizing agent, improve the sizing effect, and thus enhance the water resistance and oil resistance of the paper. For example, when using rosin glue sizing, soda ash can react with rosin acid to generate sodium rosin acid, so that it is better adsorbed on the fiber surface, forming a uniform sizing film, and improving the waterproof performance of the paper.

②Adjust the pH value of the paper: soda ash can be used to adjust the pH value of the paper, so that the paper is weakly alkaline. In the weakly alkaline environment, the cellulose and other components in the paper are more stable and not easy to hydrolysis and other reactions, which is conducive to improving the durability and preservation performance of the paper. At the same time, the appropriate pH value can also improve the printability of the paper, improve the adhesion of the ink and drying speed, so that the printing effect is better.

③water softener: If the water used in the papermaking process contains more calcium, magnesium and other metal ions, it may affect the papermaking process and paper quality, such as causing the paper to produce spots, strength decline and other problems. Soda ash can react with calcium and magnesium ions in water to generate calcium carbonate, magnesium carbonate and other precipitates, thereby reducing the hardness of water, reducing the influence of impurities in water on the papermaking process, and ensuring the stability of paper quality.

From https://www.51chem.com/.

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