Sizing agent for paper making
Alkyl ketene dimer (AKD) is a reactive neutral sizing agent. It is a waxy solid modified starch derivative. It is insoluble in water, but soluble in some aromatic hydrocarbon and organic oil solvents. It can react with hydroxyl groups on cellulose fibers under suitable heating conditions to form hydrophobic ester bonds, and endow paper with water resistance. It keeps stable under neutral and weakly alkaline environment. It will hydrolyze and lose sizing activity when exposed to strong acid, strong alkali or excessive high temperature for a long time. It is slightly hygroscopic, and will melt when the temperature rises above its melting point. It cannot coexist with strong oxidants.
Applicaion of Sizing agent for paper making
This paper sizing agent (Alkyl Ketene Dimer, AKD) is an important reactive neutral functional auxiliary for papermaking. It is applicable to a wide range of paper grades, including cultural printing paper, office copy paper, kraft packaging paper, corrugated base paper, coated paper, food wrapping paper, release base paper, and all kinds of special industrial paper. It reacts chemically with hydroxyl groups on cellulose fiber surfaces under moderate drying temperature to form a compact, continuous hydrophobic film, which greatly improves the water repellency, surface strength and dimensional stability of finished paper. It effectively restrains water penetration into the paper substrate, reduces ink feathering and bleeding during printing, and enhances ink fixation, print gloss and writing performance. It works perfectly in neutral and weakly alkaline papermaking systems, which avoids the corrosion of metal paper machine parts that usually occurs in acidic rosin sizing processes, extends the service life of screens, rollers and other equipment, and lowers the consumption of anti-corrosion materials. It has outstanding compatibility with wet strength agents, retention aids, drainage agents, fillers and other common papermaking chemicals, and will not produce precipitates or abnormal changes to the pulp system. It can be used for both internal sizing and surface sizing processes. When added in pulp, it gives uniform water resistance across the whole paper sheet; when used for surface sizing, it lifts surface gloss and reduces surface dusting. It maintains stable sizing efficiency after long-term storage of finished paper, and the sizing effect will not decay rapidly with ageing. It can help paper manufacturers reduce the dosage of alum and other acidic auxiliary agents, simplify the wastewater treatment burden of paper mills, and meet the environmental protection requirements of modern papermaking. It can be adjusted into different activity grades to match high-speed paper machines, slow-speed specialty paper machines and on-machine coating production lines. It will not cause obvious yellowing of paper after long-term storage, and preserves the original softness of paper sheets. It is also suitable for producing biodegradable packaging paper and food-contact paper products, which meets the strict safety requirements for food packaging.
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