Alkyl Ketene Dimer (AKD) is a highly effective sizing agent for paper, known for its ability to impart excellent water resistance and improve printability. However, achieving optimal results with AKD requires careful attention to its application process. NINGBO INNO PHARMCHEM CO.,LTD. provides essential guidance for paper manufacturers on how to optimize AKD usage for maximum efficiency and superior paper quality.

The journey of AKD from a raw chemical to an effective sizing agent involves several critical stages. The first step is the preparation of a stable AKD emulsion. AKD is a waxy solid at room temperature, so it must be emulsified in water using specific emulsifying agents and controlled heating (typically above its melting point, around 50-60°C). The quality of the emulsion is paramount; it should be fine, uniform, and stable to ensure even distribution onto the paper fibers. Factors like the type and concentration of emulsifiers, mixing speed, and temperature control during preparation directly influence the emulsion's effectiveness.

The point of addition for the AKD emulsion into the papermaking process is another crucial consideration. Typically, AKD is added at the wet end of the paper machine, after pulp refining and before the headbox. This placement ensures sufficient time for the AKD to interact with the cellulose fibers before sheet formation. The exact location might vary based on machine design and the specific type of AKD formulation used, but thorough mixing is essential to achieve uniform dispersion throughout the pulp slurry.

Dosage control is vital for both efficacy and cost-effectiveness. The amount of AKD added, expressed as a percentage of oven-dry pulp, depends on the target sizing level required for the specific paper grade. Overdosing can lead to over-sizing, potentially affecting paper properties like flexibility or printability, and incurring unnecessary costs. Underdosing, conversely, will result in insufficient sizing. Manufacturers must calibrate their dosing systems accurately and perform regular checks to maintain the correct application rate. This often involves lab testing and pilot trials to determine the optimal dosage for specific grades and machine conditions.

The curing process of AKD is temperature-dependent and occurs during the drying stages of papermaking. As the paper sheet moves through the dryer section, the heat promotes the esterification reaction between AKD and cellulose fibers, solidifying the hydrophobic barrier. Ensuring adequate temperature and residence time in the dryer section is critical for complete curing. Insufficient drying temperature or time can lead to incomplete sizing, which may manifest as poor water resistance or delayed development of sizing properties.

Furthermore, factors like the pH of the pulp slurry, the presence of other chemicals (retention aids, strength additives), and the type of furnish (fiber composition) can influence AKD performance. Maintaining a neutral to slightly alkaline pH (7.0-8.5) is essential for AKD's optimal reactivity. Collaborating with a chemical supplier like NINGBO INNO PHARMCHEM CO.,LTD. can provide valuable technical support in troubleshooting and optimizing these parameters, ensuring that paper manufacturers achieve the best possible results from their AKD sizing applications.