Alkyl Ketene Dimer (AKD) is a cornerstone of modern papermaking, widely utilized as a neutral sizing agent to impart water resistance and improve ink absorbency. However, the efficiency of AKD sizing is a complex interplay of various factors. NINGBO INNO PHARMCHEM CO.,LTD. provides expert insights into these critical elements, helping papermakers optimize AKD performance for enhanced product quality and operational efficiency.

The inherent chemistry of AKD, characterized by its reactive β-lactone ring, is fundamental to its function. This ring opens during the drying and curing phase, forming covalent bonds with cellulose hydroxyl groups. This chemical reaction is the basis for creating a hydrophobic surface. Factors like fiber type and fines content significantly affect AKD efficiency. For instance, hardwood pulps, with their shorter fibers and higher fines content, absorb AKD more readily but may require higher dosages. Softwood pulps generally offer more uniform sizing behavior. NINGBO INNO PHARMCHEM CO.,LTD. advises clients to consider their specific pulp characteristics when determining AKD dosage and application strategies to maximize sizing efficiency.

Maintaining precise wet-end conditions, particularly pH and conductivity, is vital. AKD sizing is most effective within a neutral to slightly alkaline pH range (6.5–8.0). Low pH can lead to premature hydrolysis of the AKD ring, reducing its reactivity and potentially destabilizing the AKD emulsion. Conversely, conditions that are too alkaline can also be detrimental. NINGBO INNO PHARMCHEM CO.,LTD. emphasizes the importance of consistent pH control and monitoring of wet-end chemistry to prevent sizing defects and optimize AKD usage. Furthermore, the interaction of AKD with retention aids, fillers, and other additives in the wet-end system can influence its retention and fixation onto the fibers. Proper management of retention aid dosage is key to ensuring AKD is effectively bonded to the fibers rather than being lost in the white water, thus improving the overall sizing efficiency.

The drying temperature and curing time are equally critical for the successful chemical bonding of AKD with cellulose. Insufficient drying means unreacted AKD remains in the sheet, reducing sizing effectiveness and potentially leading to sizing reversion. Excessive drying can cause premature hydrolysis or evaporation of emulsifiers. NINGBO INNO PHARMCHEM CO.,LTD. works with manufacturers to fine-tune these parameters for optimal results. Additionally, factors like machine speed and drainage conditions can impact AKD droplet stability and retention time, requiring strategic adjustments to dosage and the use of auxiliary agents to maintain efficiency.

Finally, the stability and shelf life of the AKD emulsion itself are paramount. A high-quality emulsion, stabilized by appropriate surfactants and emulsifiers, ensures even distribution and effective sizing. NINGBO INNO PHARMCHEM CO.,LTD. is committed to providing stable, high-performance AKD emulsions and expert guidance to help papermakers navigate the complexities of AKD sizing, ensuring optimal water resistance and cost-effectiveness in their operations.