As a supplier of AKD polymer emulsifier, I am often asked about its chemical properties. AKD, or alkyl ketene dimer, is a widely used sizing agent in the papermaking industry, and its polymer emulsifier form offers unique advantages. In this blog, I will delve into the chemical properties of AKD polymer emulsifier, shedding light on why it is a top choice for many papermaking applications.
Molecular Structure and Composition
The core of AKD is a four - membered ring structure, specifically a β - lactone ring. This ring is key to its reactivity. The alkyl chains attached to the β - lactone ring can vary in length, typically ranging from C14 to C18. These alkyl groups are responsible for the hydrophobic nature of AKD. When AKD is formulated into a polymer emulsifier, it is dispersed in an aqueous medium with the help of emulsifying agents.
The polymer component in the AKD polymer emulsifier is usually a synthetic polymer that acts as a stabilizing agent. It helps to keep the AKD droplets uniformly dispersed in the water phase, preventing coalescence and sedimentation. The choice of polymer can significantly affect the stability and performance of the emulsifier. Common polymers used include polyvinyl alcohol (PVA), polyethylene glycol (PEG), and various copolymers.
Reactivity
One of the most important chemical properties of AKD polymer emulsifier is its reactivity with cellulose. When the AKD polymer emulsifier is added to the papermaking pulp, the β - lactone ring in the AKD molecule reacts with the hydroxyl groups (-OH) on the cellulose fibers. This reaction forms a covalent bond between the AKD and the cellulose, which is a key step in the sizing process.
The reaction mechanism involves the opening of the β - lactone ring, followed by an acylation reaction with the cellulose hydroxyl groups. This results in the formation of a hydrophobic layer on the surface of the cellulose fibers. The hydrophobic layer reduces the penetration of water and other polar liquids into the paper, improving the paper's water - resistance, printability, and dimensional stability.
The reactivity of AKD is influenced by several factors, including pH, temperature, and the presence of other chemicals in the pulp. The reaction is typically favored under alkaline conditions, with an optimal pH range of 7.5 - 9.5. Higher temperatures can also accelerate the reaction rate, but excessive heat may cause the decomposition of AKD or the polymer in the emulsifier.
Stability
The stability of AKD polymer emulsifier is crucial for its effective use in papermaking. A stable emulsifier ensures that the AKD droplets remain uniformly dispersed in the water phase during storage, transportation, and application. There are two main types of stability to consider: physical stability and chemical stability.
Physical Stability: Physical stability refers to the resistance of the emulsifier to phase separation, creaming, and sedimentation. The polymer in the AKD polymer emulsifier plays a vital role in maintaining physical stability. It forms a protective layer around the AKD droplets, preventing them from coming into contact and coalescing. The viscosity of the continuous phase also affects physical stability. A higher viscosity can slow down the movement of the droplets, reducing the likelihood of aggregation.
Chemical Stability: Chemical stability is related to the resistance of AKD and the polymer in the emulsifier to chemical degradation. AKD is sensitive to hydrolysis, especially under acidic or high - temperature conditions. Hydrolysis of the β - lactone ring can lead to the formation of fatty acids and ketones, which reduces the sizing efficiency of AKD. The polymer in the emulsifier should also be chemically stable to maintain its emulsifying and stabilizing functions.
Compatibility with Other Papermaking Additives
In the papermaking process, AKD polymer emulsifier is often used in combination with other additives. Therefore, its compatibility with these additives is an important consideration.
Anionic Trash Catcher: Anionic trash in the pulp can interfere with the sizing process by adsorbing onto the AKD droplets or the cellulose fibers. An Anionic Trash Catcher can be used to remove anionic trash from the pulp. AKD polymer emulsifier is generally compatible with anionic trash catchers, and their combined use can improve the sizing efficiency and the overall quality of the paper.
Fixing Agent in Papermaking Inkjet Paper: Fixing Agent in Papermaking Inkjet Paper is used to improve the ink absorption and fixation on the paper surface. AKD polymer emulsifier can be used in conjunction with fixing agents to enhance the water - resistance of the inkjet paper while maintaining good ink - fixing properties.
Dry and Wet Strength Agent for Papermaking: Dry and Wet Strength Agent for Papermaking is used to increase the strength of the paper in both dry and wet conditions. AKD polymer emulsifier is compatible with many dry and wet strength agents, and their combined use can produce paper with excellent strength and water - resistance.
Environmental Impact
In recent years, environmental concerns have become increasingly important in the papermaking industry. AKD polymer emulsifier has several advantages in terms of environmental impact.
Firstly, AKD is a biodegradable compound. The alkyl chains and the β - lactone ring in AKD can be broken down by microorganisms in the environment, reducing its long - term environmental persistence. Secondly, the polymer used in the emulsifier can be selected to be environmentally friendly. For example, PVA and PEG are relatively non - toxic and biodegradable polymers.
Conclusion
In summary, the chemical properties of AKD polymer emulsifier, including its molecular structure, reactivity, stability, compatibility with other additives, and environmental impact, make it an ideal sizing agent for the papermaking industry. Its ability to form covalent bonds with cellulose fibers provides excellent water - resistance and other performance benefits to the paper.
If you are in the papermaking industry and are looking for a high - quality AKD polymer emulsifier, we are here to help. Our products are carefully formulated to ensure optimal performance and stability. We can also provide technical support and advice on the use of our AKD polymer emulsifier in your specific papermaking process. Contact us to start a procurement discussion and take your papermaking quality to the next level.
References
- Hubbe, M. A., Rojas, O. J., Venditti, R. A., & Pawlak, J. J. (2007). Sizing of paper with alkyl ketene dimer: A review. Progress in Organic Coatings, 58(3), 179 - 197.
- Xiao, R., & Hubbe, M. A. (2012). Effects of salts and other factors on the sizing efficiency of alkyl ketene dimer emulsions. Journal of Pulp and Paper Science, 38(6), 231 - 239.
- Shen, J., & Yang, F. (2015). Preparation and properties of AKD emulsion stabilized by cationic polyacrylamide and polyvinyl alcohol. Journal of Dispersion Science and Technology, 36(10), 1394 - 1400.