Polyamide Epichlorohydrin (PAE) resin has become an indispensable tool for papermakers looking to impart superior wet strength and enhance other paper properties. With a range of PAE products available, each with slightly different characteristics, choosing the right one for a specific application is crucial for maximizing performance and cost-effectiveness. This guide outlines the key factors papermakers should consider when selecting a PAE wet strength agent.

1. Paper Grade and Required Performance Characteristics

The intended use of the final paper product is the primary determinant in selecting a PAE resin. Different paper grades have varying requirements for wet strength, dry strength, absorbency, and permanence of the wet strength effect.

  • High-Demand Wet Strength: For products like industrial wipers, filter papers, or durable packaging exposed to constant moisture, resins offering the highest degree of permanent wet strength are essential.
  • Sanitary Tissues (Facial, Towels): While wet strength is important, maintaining softness and absorbency is also critical. Some PAE formulations are optimized to balance these properties.
  • Specialty Papers: For currency, maps, or decorative papers, the permanence and stability of the wet strength over time might be prioritized.

2. Process Conditions: pH and Chemistry Compatibility

PAE resins are known for their versatility across different pH ranges, typically performing well in neutral to alkaline conditions. However, variations exist:

  • pH Range: Ensure the chosen PAE resin is optimized for your specific machine's pH. Some formulations might offer slightly better performance or stability at the extreme ends of the effective pH range.
  • Anionic Trash Load: In systems with a high concentration of anionic materials (e.g., from recycled pulp or other additives), a PAE resin with a strong cationic charge density will be more effective in binding to fibers and resisting displacement by anionic impurities.
  • Other Additives: Compatibility with other chemicals used in the wet end (sizing agents, retention aids, etc.) is important to prevent unwanted interactions or reduced efficacy of any component.

3. Resin Characteristics: Solids Content, Viscosity, and Purity

The physical and chemical properties of the PAE resin itself play a significant role:

  • Solids Content: PAE resins are available in various solids concentrations (e.g., 12.5%, 20%, 25%). Higher solids content can mean more active polymer per unit volume, potentially reducing shipping and storage costs. However, higher solids resins may also have higher viscosities, impacting handling and dilution.
  • Viscosity: Lower viscosity resins are generally easier to pump, dilute, and meter. Ensure the viscosity is suitable for your plant’s existing equipment.
  • Purity and By-products: While PAE is a non-formaldehyde resin, the manufacturing process can result in by-products like 1,3-DCP and 3-MCPD. Regulatory requirements and environmental concerns may necessitate choosing resins with lower levels of these by-products. Always check product specifications for relevant certifications or compliance statements.

4. Cost-in-Use and Supplier Support

While the purchase price of a resin is important, the true measure of its value is the 'cost-in-use'. This considers the dosage required for desired performance, the impact on other chemicals, and any efficiency gains or losses.

  • Dosage Requirements: Some PAE resins may require lower dosages to achieve the same level of wet strength as others, leading to cost savings.
  • Technical Support: Partnering with a reputable supplier who can offer technical expertise, assistance with trials, and troubleshooting is invaluable. They can help guide you to the most suitable PAE product for your specific needs.

Conclusion

Selecting the optimal PAE wet strength resin involves a careful consideration of the target paper properties, the papermaking process chemistry, the resin's inherent characteristics, and the overall cost-effectiveness. By understanding these factors and working closely with suppliers, papermakers can leverage the power of PAE to achieve superior paper performance, enhance machine efficiency, and ensure product safety and sustainability.