Sodium carboxymethyl cellulose (CMC) finds various applications in the paper industry due to its unique properties as a water-soluble polymer. Here are some common applications of CMC in the paper industry:

1. Surface Sizing:
   • CMC is used as a surface sizing agent in papermaking to improve the surface strength, smoothness, and printability of paper. It forms a thin film on the surface of the paper, reducing surface porosity and enhancing ink holdout during printing.
2. Internal Sizing:
   • CMC can be added to the paper pulp as an internal sizing agent to improve the paper’s resistance to liquid penetration and increase its water repellency. This helps prevent ink spread and improves the quality of printed images and text.
3. Retention and Drainage Aid:
   • CMC serves as a retention aid and drainage aid in the papermaking process, improving the retention of fine particles and fillers in the paper pulp and enhancing drainage efficiency on the paper machine. This results in improved paper formation, reduced paper breaks, and increased machine productivity.
4. Control of Coating Rheology:
   • In coated paper production, CMC is used as a rheology modifier in the coating formulation to control viscosity and flow behavior. It helps maintain uniform coating thickness, improve coating coverage, and enhance the surface properties of coated papers, such as gloss and smoothness.
5. Strength Enhancement:
   • CMC can improve the tensile strength, tear resistance, and durability of paper products when added to the paper pulp. It acts as a binder, strengthening fibers and enhancing paper formation, which leads to improved paper quality and performance.
6. Control of Paper Properties:
   • By adjusting the type and concentration of CMC used in papermaking formulations, paper manufacturers can tailor the properties of the paper to meet specific requirements, such as brightness, opacity, stiffness, and surface smoothness.
7. Formation Improvement:
   • CMC helps improve the formation of paper sheets by promoting fiber bonding and reducing the formation of defects such as pinholes, spots, and streaks. This results in more uniform and consistent paper sheets with improved visual appearance and printability.
8. Functional Additive:
   • CMC can be added to specialty papers and paperboard products as a functional additive to impart specific properties, such as moisture resistance, anti-static properties, or controlled release characteristics.

sodium carboxymethyl cellulose (CMC) plays a vital role in the paper industry by contributing to the production of high-quality papers with desirable properties, including surface strength, printability, water resistance, and formation. Its versatility and effectiveness make it a valuable additive in various stages of the papermaking process, from pulp preparation to coating and finishing.