Performance of cationic styrene maleimide copolymers in the wet end of papermaking.

APPLICATION: New chemical additives composed of styrene maleimide resins help improve retention properties without impairing other characteristics of the paper.

Although styrene maleic anhydridye (SMA) copolymers are used today as sizing agents, little research has been carried out on some new styrene maleimide resins, or SMA imides. Relatively inexpensive, SMA imide resins can be dissolved easily and can be used in the headbox. They are available in different ratios of styrene to maleimide, from 1:1 to 1:4.

In this study, the researchers carried out experiments on SMA imides to determine how well these new resins perform in the wet end of the paper machine. They worked with three SMA imides at styrene to maleimide ratios r of 1/1, 1/2, and 1/3. In addition, they evaluated a methylated SMA imide resin, SMA IQ, which has a styrene to maleimide ratio of 1/2 but has an extra methyl group bonded to the nitrogen atom in the ammonium group.

When SMA imide resins were used as coagulants with chemical recycled pulp and TMP, the retention of fines and fillers was measured to be high. The wet strength, burst strength, and tear strength of paper handsheets were substantially improved, with good linting efficiency and an increase in brightness. SMA IQ was found to promote interfiber bonding and can be considered a good dry strength additive.

Overall, SMA imide resins are versatile chemicals with intrinsic properties that can be used under diverse conditions. Consequently, these resins are adaptable to the particular needs of a paper mill. View this paper online at http://www.tappi.org/index.asp?pid=29100

Edouard Valton and Mohini Sain are with the University of Toronto, Canada. John Schmidhauser is with Sartomer Company, Exton, PA. Email Sain at [e-mail].