Comprehensive Comparison and Analysis of ASA and AKD: Neutral Sizing Agents for Papermaking

Foreword

In modern papermaking, sizing is a crucial step in imparting water and liquid resistance to paper. With increasing demands for environmental protection and paper durability, neutral.../Alkaline sizing has replaced traditional acidic sizing as the mainstream method. Against this backdrop, alkenyl succinic anhydride (…WORK) and alkyl ketene dimer (AKDThese two have become the two most important neutral sizing agents. They share the same goal, but their chemical properties and application methods are quite different.

Core Features Comparison

WORKAlkenyl succinic anhydride is figuratively called an "impatient athlete." It exhibits extremely high reactivity and rapid sizing, completing the reaction quickly in the wet end of the paper machine with almost no need for post-curing, making it ideal for high-speed paper machine production. However, its chemically reactive nature makes it highly susceptible to hydrolysis, necessitating a sophisticated on-site emulsification system.

AKDAlkyl ketene dimers are like a "slow-burning genius." Their reaction is mild and slow, with the sizing effect mainly completed gradually during drying and subsequent storage, requiring a "curing period" of several hours to several days to achieve optimal results. Their advantage lies in the long-lasting and stable sizing effect, but it is necessary to manage the phenomenon of "false sizing."

Preparation and Mechanism of Action

Preparation route

· WORKPreparation: It is obtained by an addition reaction of long-chain olefins with maleic anhydride. The process is relatively simple and efficient, but the product is an unstable oily liquid that must be emulsified on-site before use.

· AKDPreparation: Synthesized from natural fatty acids through multiple steps including acyl chloride and dimerization. The process is more complex, and the product is a solid, typically supplied as a pre-emulsified commercial emulsion.

Mechanism of action

· WORKIt belongs to "rapid esterification": the anhydride ring in its molecule can quickly undergo ring-opening esterification with the hydroxyl group of cellulose under neutral conditions to form a strong hydrophobic ester bond.

· AKDIt belongs to the category of "delayed curing": its β-molecule-The lactone ring needs to be opened under thermal energy, and then undergoes a nucleophilic addition reaction with the cellulose hydroxyl group to form a stable ketone ester structure.

Core Application Technology

WORKThe lifeline of applications: emulsification systems

WORKThe application depends entirely on the emulsification effect. It must be emulsified into a stable, positively charged emulsion with fine particle size using high-shear equipment, cationic emulsifiers (such as quaternary ammonium salts), and cationic starch. This process requires preparation on demand and strict temperature control (usually...).<70℃) andpHValue, the storage time of emulsion generally does not exceed4-6Hours to prevent hydrolysis and failure.

AKDKey to application: Maturity management

AKDThe core of the application lies in ensuring sufficient chemical bonding. Appropriate drying temperature and sufficient storage time are required, and sometimes a curing accelerator needs to be added to promote complete reaction and avoid "false sizing" caused by physical adsorption, thereby achieving a durable and stable sizing effect.

Selection Guide: How to Make Decisions Based on Your Needs

· chooseWORKIf you are looking for: extremely high production speeds (suitable for high-speed paper machines); instant sizing effects for quick inspection and shipment; and flexibility to frequently adjust production formulas, then you must be willing and able to invest in and maintain a sophisticated online emulsification and process control system.

· chooseAKDIf you value: the ultimate and lasting water resistance and durability of the final product (such as high-grade paperboard and specialty paper); ease of wet end operation (using ready-to-use commercial emulsions); and stable production planning that allows sufficient curing time for the product.

Summarize

WORKandAKDThese are the two pillars of neutral sizing technology, each with its irreplaceable advantages and applicable scenarios. (Choose...)WORKThis means embracing efficiency and flexibility, but mastering emulsification as a core process is essential; choosing...AKDThis means pursuing stable and lasting results, but it requires accepting delays and managing the maturation process effectively. A wise choice stems from a comprehensive consideration of one's own production conditions, product goals, and technical management capabilities.