Low viscosity in sodium carboxymethyl cellulose (CMC) production is usually caused by three factors: raw materials, production process, or molecular structure. The core reason is an insufficient degree of polymerization (molecular weight) or a low degree of substitution (DS).

Specific reasons and solutions are as follows:

1. Raw Materials and Molecular Structure

· Low Degree of Polymerization (Main Cause): Viscosity is mainly determined by the length of the molecular chain (degree of polymerization). If the raw material cellulose is severely degraded or the degree of polymerization itself is low, the product viscosity will inevitably be low.

· Uneven Degree of Substitution: A low degree of substitution or uneven distribution of substituents will weaken the intermolecular forces, thereby reducing viscosity.

 2. Production Process Control

· Improper Alkalization/Etherification: This is the core issue. Improper control of alkali concentration, temperature, or time (such as excessively high etherification temperature leading to main chain degradation) will result in incomplete reaction and insufficient viscosity.

• Material Proportioning Issues: Insufficient amounts of chloroacetic acid (etherifying agent) or sodium hydroxide directly affect the degree of substitution and viscosity.

• Excessive Degradation: Improper protection during alkalization and etherification processes, such as strong alkalis or high temperatures, can break down molecular chains, leading to a significant decrease in viscosity.

3. Post-processing and External Factors

• Physical Form: Excessively fine particles increase the contact area during dissolution, causing localized hydrolysis or mechanical damage, resulting in a decrease in measured viscosity.

• Environmental Factors: Low pH (acidic) or high temperatures (such as excessively high drying temperatures) in the later stages can damage the molecular structure, leading to an irreversible decrease in viscosity.

• Impurity Interference: The presence of divalent metal ions (Ca²⁺, Mg²⁺) or salt impurities can disrupt the molecular chain extension state, reducing viscosity.

4. Role of CMC in Paper Production
CMC plays a vital role in papermaking processes. It improves paper strength and surface smoothness.  It enhances fiber bonding during sheet formation. CMC paper making grade. The paper quality becomes more uniform.

Targeted Solutions

• Raw Material Selection: Prioritize the use of high-polymerization-degree pure cellulose raw materials (such as refined cotton), and avoid using degraded pulp.

• Optimize the process: Precisely control the alkali concentration and etherification temperature to prevent excessive degradation; appropriately extend the ripening time (e.g., etherification for more than 70 minutes) to ensure a complete reaction.

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