CMC For Paper

Carboxymethyl Cellulose (CMC) can significantly improving the paper's water resistance, surface strength and printability.

I. Main Application Forms

1. Internal Sizing Agent

CMC is added directly to the pulp, where the carboxyl groups on its molecular chains form hydrogen bonds with the hydroxyl groups on the fiber surface, enabling uniform distribution among the fibers.

Function: It reduces the paper's absorption of water and ink, improving water resistance and dimensional stability. Suitable for writing paper, cultural paper, and similar grades.

2. Surface Sizing Auxiliary

CMC is compounded with primary sizing agents such as starch and AKD (alkyl ketene dimer) and applied to the paper surface to form a continuous film.

Function: It enhances surface strength, smoothness, and abrasion resistance while reducing linting and dusting during printing. Commonly used in coated paper, packaging paper, and similar grades.

II. Core Functions and Benefits

Improved Water Resistance

After the hydrophilic carboxyl groups of CMC are adsorbed by fibers, they block the hydrophilic sites on the fiber surface, reducing the paper's sizing degree (e.g., Cobb value) by 30%–50%.

Enhanced Surface Strength

When used as a surface sizing auxiliary, CMC works synergistically with starch to improve surface bonding strength (SCT value), meeting the demands of high-speed printing.

Better Fiber Bonding

In internal sizing, CMC acts as a "bridge" between fibers, reinforcing fiber bonding and increasing tensile strength and tear strength by 10%–20%.

Excellent Compatibility

CMC blends well with other papermaking additives such as fillers, dyes, and preservatives, without affecting paper whiteness or dyeing performance. It also offers a wide working pH range (5–9).