CMC in the papermaking industry

 Sodium carboxymethyl cellulose (CMC) is an anionic water-soluble polymer compound obtained by etherification of cellulose. It has good water solubility, film-forming, suspension, emulsification and thickening properties. In the papermaking industry, CMC, as an important functional additive, is widely used in pulping, papermaking, coating and other process links, significantly improving the quality and production efficiency of paper.

1. Basic properties of CMC

CMC is the product formed by the etherification reaction of cellulose with sodium chloroacetate. Its main properties include:

Good water solubility: CMC is easily soluble in cold water to form a transparent and uniform colloidal solution.

Thickening and film-forming properties: It has a significant viscosity-enhancing effect in the solution and can form a dense film layer on the surface of the paper.

Dispersion and stabilization: CMC can be used as an emulsifier or suspending agent to keep the system stable.

Excellent hydrophilicity: Because it contains a large number of carboxymethyl groups, it can form hydrogen bonds with water to improve the hydrophilicity of paper.

2. Main applications of CMC in the papermaking industry

Pulping stage

During the pulping process in the early stage of papermaking, CMC can be added as a dispersant and fiber treatment agent to improve the dispersibility of the pulp and the bonding force between fibers. Specific effects include:

Improving fiber dispersibility: CMC can prevent the aggregation between fibers, help the uniform distribution of pulp, and improve the uniformity and smoothness of paper sheets.

Enhancing fiber bonding: CMC molecules can penetrate between fibers and enhance the hydrogen bonding between fibers, thereby improving the dry strength and wet strength of the finished paper.

Papermaking stage

During the papermaking process, CMC is often used as a surface sizing agent, dry strength agent and retention and drainage aid:

Surface sizing: By adding CMC in the wet part of the paper machine or the surface sizing section, the sizing performance of the paper surface can be improved, the water resistance and printability of the paper can be improved, and it is especially suitable for printing paper and writing paper.

Increasing dry strength: The carboxyl groups in CMC can hydrogen bond with the hydroxyl groups in the pulp to improve the bonding force between fibers, thereby significantly improving the dry strength of the finished paper.

Retention and drainage effects: CMC can form composite flocs with inorganic fillers and other additives, improve the retention rate of fine fibers, fillers, etc., help improve paper structure and reduce resource waste.

Paper coating stage

As a coating additive, CMC has thickening, film-forming and dispersing effects, and is widely used in the paper coating process:

As a coating binder: CMC can combine with pigment particles to make them more firmly attached to the paper surface, improving the adhesion and stability of the coating.

Improving coating fluidity: CMC adjusts the rheological properties of the coating to make it have good coating adaptability and reduce coating defects.

Improving coating performance: The uniform film formed by CMC can improve the smoothness, whiteness and printability of the coating.

Specialty paper manufacturing

In the production of some specialty papers (such as carbonless paper, photosensitive paper, security paper, etc.), CMC can also be used in combination with other functional additives to give paper more functionality, such as oil resistance and anti-counterfeiting properties. Especially in environmentally friendly paper products and food packaging paper, CMC is favored for its degradable and non-toxic properties.

3. Advantages of using CMC

Green and environmentally friendly: CMC is derived from natural cellulose, non-toxic and harmless during use, and meets the requirements of sustainable development.

High cost performance: CMC is used in small amounts but has significant effects. It can effectively reduce the amount of other chemicals used in papermaking and reduce overall costs.

Improve paper quality: Improve paper strength, printing adaptability and appearance performance to meet the quality requirements of high-end paper products.

As a cellulose derivative with excellent performance, CMC plays an irreplaceable role in the papermaking industry. From improving pulp dispersibility and enhancing paper strength to improving coating performance and improving paper surface quality, CMC has become an indispensable and important auxiliary agent for modern papermaking. With the in-depth development of the concept of green environmental protection, the application prospects of CMC in the field of papermaking will be broader, and its potential in functionalization and environmental protection still needs to be further explored and developed.