Improving The Sizing Efficiency Of Asa By Using Hydrophobically Modified And Acid-Hydrolyzed Cationic Starch

An important part of preparing ASA emulsion is to use cationic starch emulsifiers. Generally, the ratio of starch emulsifier to ASA is as high as 2:1-4:1.

But have you ever thought that if the cationic starch emulsifier is modified to have a certain hydrophobicity, can it improve the stability of ASA emulsion? At the same time, will the sizing efficiency of ASA emulsion using this hydrophobic starch be better?

Furthermore, if the molecular weight of the above cationic hydrophobic starch is deliberately reduced, will it help to obtain ASA emulsion products with smaller particle size, thereby making the sizing efficiency of ASA emulsion products higher?

As for the answer to the above question, in fact, as early as 2004, the team of Professor Hak Lae Lee and Professor Hye Jung Youn from the College of Agriculture and Life Sciences at Seoul National University in South Korea gave the answer. For details, see the literature:

Hak Lae Lee, Jong Soon Kim, and Hye Jung Youn, Improvement of ASA sizing efficiency using hydrophobically modified and acid-hydrolyzed starches, TAPPI J. 3(13): 3-6 (2004). The title of the paper can be translated as: Improving the sizing efficiency of ASA using hydrophobically modified and acid-hydrolyzed starches.

Two interesting findings obtained in this study are summarized as follows:

1. Using hydrophobically modified cationic starch as an emulsifier can make ASA emulsion more stable, which is manifested by the smaller change in pH value of the emulsion product over time, because the reaction of ASA hydrolysis to dibasic acid is delayed.

2. Using the above hydrophobic cationic starch to emulsify ASA does not improve the sizing efficiency of ASA; however, the sizing efficiency of ASA can be improved by acidifying and degrading the hydrophobic starch before use, because the hydrophobic starch with a smaller molecular weight can reduce the thickness of the starch layer of the ASA emulsion, obtain emulsion particles with smaller particle size, and distribute them more evenly on the fiber.

If the viscosity of the starch solution is too low, it will generally lead to a poor sizing effect of ASA. This phenomenon is consistent with this study by Seoul University, that is, the amount of acid used to degrade the hydrophobic cationic starch should not be too high, otherwise the molecular weight of the product will be too low (the viscosity will also be too low), and the sizing effect will be reduced.