In the papermaking industry, sodium carboxymethyl cellulose (CMC) serves several important functions throughout various stages of the papermaking process. Here’s how CMC works in the papermaking industry:

1. Retention and Drainage Aid:
   • CMC is commonly used as a retention and drainage aid in papermaking. It improves the retention of fine fibers, fillers, and other additives in the paper pulp, leading to higher paper strength and smoother surface characteristics.
   • CMC enhances the drainage of water from the paper pulp on the forming wire or fabric, resulting in faster dewatering and increased production efficiency.
   • By promoting fiber and filler retention and optimizing drainage, CMC helps improve the formation and uniformity of the paper sheet, reducing defects such as streaking, spots, and holes.
2. Formation Improvement:
   • Sodium CMC contributes to the formation improvement of paper sheets by enhancing the distribution and bonding of fibers and fillers during the sheet formation process.
   • It helps create a more uniform fiber network and filler distribution, resulting in improved paper strength, smoothness, and printability.
   • CMC reduces the tendency of fibers and fillers to agglomerate or clump together, ensuring even distribution throughout the paper sheet and minimizing defects such as mottling and uneven coating.
3. Surface Sizing:
   • In surface sizing applications, sodium CMC is used as a surface sizing agent to improve the surface properties of the paper, such as smoothness, ink receptivity, and print quality.
   • CMC forms a thin, uniform film on the surface of the paper, providing a smooth and glossy finish that enhances the appearance and printability of the paper.
   • It helps reduce ink penetration into the paper substrate, resulting in sharper print images, improved color reproduction, and reduced ink consumption.
4. Strength Enhancer:
   • Sodium CMC acts as a strength enhancer in papermaking by improving the bonding and cohesion between paper fibers.
   • It increases the internal bond strength (tensile strength and tear resistance) of the paper sheet, making it more durable and resistant to tearing and bursting.
   • CMC also enhances the wet strength of paper, preventing excessive deformation and collapse of the paper structure when exposed to moisture or liquid.
5. Controlled Flocculation:
   • CMC can be used to control the flocculation of paper pulp fibers during the papermaking process. By adjusting the dosage and molecular weight of CMC, the flocculation behavior of fibers can be optimized to improve drainage and formation characteristics.
   • Controlled flocculation with CMC helps reduce fiber flocculation and agglomeration, ensuring uniform dispersion of fibers and fillers throughout the paper pulp suspension.

sodium carboxymethyl cellulose (CMC) plays a critical role in the papermaking industry by serving as a retention and drainage aid, formation improver, surface sizing agent, strength enhancer, and controlled flocculation agent. Its versatility, compatibility, and effectiveness make it a valuable additive in various paper grades, including printing papers, packaging papers, tissue papers, and specialty papers, contributing to improved paper quality, performance, and value.