A NEW SIZING AGENT - STYRENE-MALEIC ANHYDRIDE COPOLYMER WITH ALUM OR IRON MORDANTS

Alkali-soluble styrene-maleic anhydride copolymers (SMA) were found to be good sizing agents on unbleached Douglas-fir kraft pulp and unblea ched thermomechanical pulp (TMP) when used with ferrous chloride or al um as mordants. Three SMAs with different molecular weights and maleic anhydride contents were tested as internal sizing agents for both ble ached and unbleached pulps. All three polymers gave good sizing to the unbleached pulps. None showed any significant sizing effect on bleach ed pulps. No dependence upon polymer molecular weight or maleic anhydr ide content weight or maleic anhydride content was observed. Rosin siz ing showed approximately the same breaking length and burst index rega rdless of mordant. SMA sized unbleached Douglas-fir kraft pulp with fe rrous chloride or alum as mordant gave increases of 49-59% in breaking length and 51-65% in burst index when compared to rosin sized paper a t the same conditions. Brightness was greatly decreased when ferrous c hloride was used as mordant.